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Rindraharisaona, E. J., E. Cordier, G. Barruol, F. R. Fontaine, and M. Singh. "Assessing swells in La Réunion Island from terrestrial seismic observations, oceanographic records and offshore wave models." Geophysical Journal International 221, no. 3 (2020): 1883–95. http://dx.doi.org/10.1093/gji/ggaa117.
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SUMMARY La Réunion Island in the southwest Indian Ocean is seasonally affected by austral swells among which some extreme events may have strong impacts on coastal infrastructures. The very limited number of sensors available on and around the island and in the whole SW Indian Ocean impedes any direct monitoring of the swell activity. In this study, we analyse direct observations of the ocean swell by combining terrestrial measurements of the microseismic noise with in situ oceanographic observations issued from two pressure gauges and an Acoustic Doppler Current Profiler (ADCP), together with swell numerical modelling. The reliability of the terrestrial seismic station to characterize the ocean activity in both the primary and secondary microseisms peaks (PM and SM, respectively), and also in the long period secondary microseismic peak (LPSM) for the case of La Réunion Island is presented and discussed here. By computing the hourly RMS of the PM and LP(SM) amplitudes, we establish a transfer function between the PM and (LP)SM amplitude and the maximum wave height, which appears to be valid for any PM and LPSM amplitudes >0.15 μm and >1.0 μm, respectively. The correlation coefficient between the PM amplitude and the wave height is >0.92. It suggests that the PM amplitude can be used as a robust proxy for the swell height and may help calibrating the wave heights from other independent observable. For some swell events, we observe LPSM that correlate well (>0.91) with the local wave height suggesting a generation by coastal swell reflection. From polarization and spectral analyses, directions and periods of swells are also well retrieved from seismic data. Finally, continuous measure of the SM amplitude shows that it can be used as precursor information for distant swells that may hit La Réunion Island a few days after their generation in the southern Indian Ocean.
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Wiguna, Taufan, Rahadian Rahadian, Sri Ardhyastuti, Safira Rahmah, and Tati Zera. "SEISMIC FACIES ANALYSIS ON 2D SEISMIC REFLECTION PROFILE IN BARUNA AND JAYA LINE AT NORTH EAST JAVA BASIN." Jurnal Neutrino 9, no. 1 (2016): 15. http://dx.doi.org/10.18860/neu.v9i1.3665.
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<p class="abstrak">Two dimension (2D) seismic profile of Baruna and Jaya lines at North-East Java Basin show seismic reflector characteristics that can be used to interpret sediment thickness and continuity. Those reflector characteristics that can be applied for seismic facies analysis that represent depositional environment. This study starts from seismic data processing that using Kirchhoff Post Stack Time Migration method which is 2D seismic profile as result. Seismic reflector characterization has been done to both 2D profiles. Seismic reflector characterization was grouped as (i) individual reflection, (ii) reflection configuration, (iii) reflection termination, (iv) external form. Individual reflection characteristics show high and medium amplitude, medium and low frequency, and continuous. Configuration reflection is continuous with parallel and subparallel type. Reflection termination shows onlap, and external form shows sheet drape. Local mound appearance can be interpreted as paleo-reef. Facies seismic anlysis result for this study area is shelf.</p>
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Howell, Frank T. "A continuous seismic profile survey of Windermere." Geological Journal 7, no. 2 (2007): 329–34. http://dx.doi.org/10.1002/gj.3350070208.
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Hu, Liang-Zie, George A. McMechan, and Jerry M. Harris. "Elastic finite-difference modeling of cross-hole seismic data." Bulletin of the Seismological Society of America 78, no. 5 (1988): 1796–806. http://dx.doi.org/10.1785/bssa0780051796.
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Abstract Cross-hole seismic data exhibit unique characteristics not seen in surface survey data or even in vertical seismic profile data. These are, to a large extent, due to the near-horizontal propagation involved. Transmitted, reflected, evanescent, guided, and converted waves are all prominent; these require an elastic algorithm for realistic simulation. Elastic finite-differences are used to synthesize responses (both fixed-time snapshots and seismogram profiles) for a series of two-dimensional models of increasing complexity. Special emphasis is given to guided waves in continuous and segmented low-velocity zones.
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Snyder, David, Gervais Perron, Karen Pflug, and Kevin Stevens. "New insights into the structure of the Sudbury Igneous Complex from downhole seismic studies." Canadian Journal of Earth Sciences 39, no. 6 (2002): 943–51. http://dx.doi.org/10.1139/e02-013.
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New vertical seismic profiles from the northwest margin of the Sudbury impact structure provide details of structural geometries within the lower impact melt sheet (usually called the Sudbury Igneous Complex) and the sublayer norite layer. Vertical seismic profile sections and common depth point transformation images display several continuous reflections that correlate with faults and stratigraphic boundaries logged from drill cores. Of four possible mechanisms that explain repeated rock units, late-stage flow or normal faulting that occurred within the last layers to cool and crystallize might best explain the observations, especially the most prominent reflectors observed in the seismic data. These results reaffirm previously proposed two-stage cooling and deformation models for the impact melt sheet.
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Simon, H., S. Buske, P. Hedin, C. Juhlin, F. Krauß, and R. Giese. "Anisotropic Kirchhoff pre-stack depth migration at the COSC-1 borehole, central Sweden." Geophysical Journal International 219, no. 1 (2019): 66–79. http://dx.doi.org/10.1093/gji/ggz286.
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SUMMARYA remarkably well preserved representation of a deeply eroded Palaeozoic orogen is found in the Scandinavian Caledonides, formed by the collision of the two palaeocontinents Baltica and Laurentia. Today, after 400 Ma of erosion along with uplift and extension during the opening of the North Atlantic Ocean, the geological structures in central western Sweden comprise far transported allochthonous units, the underlying Precambrian crystalline basement, and a shallow west-dipping décollement that separates the two and is associated with a thin layer of Cambrian black shales. These structures, in particular the Seve Nappes (upper part of the Middle Allochthons), the Lower Allochthons and the highly reflective basement are the target of the two approximately 2.5 km deep fully cored scientific boreholes in central Sweden that are part of the project COSC (Collisional Orogeny in the Scandinavian Caledonides). Thus, a continuous 5 km tectonostratigraphic profile through the Caledonian nappes into Baltica’s basement will be recovered. The first borehole, COSC-1, was successfully drilled in 2014 and revealed a thick section of the seismically highly reflective Lower Seve Nappe. The Seve Nappe Complex, mainly consisting of felsic gneisses and mafic amphibolites, appears to be highly anisotropic. To allow for extrapolation of findings from core analysis and downhole logging to the structures around the borehole, several surface and borehole seismic experiments were conducted. Here, we use three long offset surface seismic profiles that are centred on the borehole COSC-1 to image the structures in the vicinity of the borehole and below it. We applied Kirchhoff pre-stack depth migration, taking into account the seismic anisotropy in the Seve Nappe Complex. We calculated Green’s functions using an anisotropic eikonal solver for a VTI (transversely isotropic with vertical axis of symmetry) velocity model, which was previously derived by the analysis of VSP (Vertical Seismic Profile) and surface seismic data. We show, that the anisotropic results are superior to the corresponding isotropic depth migration. The reflections appear significantly more continuous and better focused. The depth imaging of the long offset profiles provides a link between a high-resolution 3-D data set and the regional scale 2-D COSC Seismic Profile and complements these data sets, especially in the deeper parts below the borehole. However, many of the reflective structures can be observed in the different data sets. Most of the dominant reflections imaged originate below the bottom of the borehole and are situated within the Precambrian basement or at the transition zones between Middle and Lower Allochthons and the basement. The origin of the deeper reflections remains enigmatic, possibly representing dolerite intrusions or deformation zones of Caledonian or pre-Caledonian age.
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Chang, Yan Yan, Chang Song Lin, Xin Huai Zhou, and Shi Qiang Xia. "Seismic Sedimentology Research on Sublacustrine Fan of the Oligocene Dongying Formation, Liaozhong Depression, Bohai Bay Basin, Northeast China." Advanced Materials Research 807-809 (September 2013): 2151–54. http://dx.doi.org/10.4028/www.scientific.net/amr.807-809.2151.
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In Liaozhong Depression, five types of sublacustrine fans are developed in the relative lowstand systems tracts of the fourth-order sequence in Dongying Formation. In drilling cores, typical turbidites characteristics exist including bedding structures such as slump deformation structure, parallel bedding, grading laminations and multi-stage scoured basal surfaces. They also can be recognized in well logs with distinctive low gamma-ray and high-resistivity stacking patterns. Logging curves usually display serrated bell shape, cylinder shape and funnel shape respectively. On seismic reflection profiles, sublacustrine fan typically shows lateral downlap on its external geometry and continuous or discontinuous “vermicular” reflection characteristics in its inner seismic reflection texture. According to the calibration results of drilling data, continuous seismic reflection profiles are interpreted to be mud-rich deposits with cohesive, soft sediment-deformation. Discontinuous seismic reflections with lateral migration and apparent incised valleys are interpreted to be sand-rich deposits which probably host the most potential litho-stratigraphic traps.
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Ismail, Ahmed, F. Brett Denny, and Mohamed Metwaly. "Comparing continuous profiles from MASW and shear-wave reflection seismic methods." Journal of Applied Geophysics 105 (June 2014): 67–77. http://dx.doi.org/10.1016/j.jappgeo.2014.03.007.
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Jackson, H. R. "Seismic refraction profiles in the Gulf of Saint Lawrence and implications for extent of continuous Grenville lower crust." Canadian Journal of Earth Sciences 39, no. 1 (2002): 1–17. http://dx.doi.org/10.1139/e01-054.
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Near the exposed Grenville craton, a two-layer crust with velocities of 6.2 km s1 and 6.65 km s1 and low gradient is measured. The 6.65 km s1 velocity is observed at the shallow depth of 15 km and the Moho at greater than 40 km depth. Towards the Appalachian orogen, a southwards dipping ramp is developed in the mid crust on the top of the 6.65 km s1 layer. A collinear reflection profile confirms the southwards dipping ramp, the shallowing Moho and the lateral changes in the lower crust. A published refraction profile that crosses this reflection profile near the southern end confirms the termination of the 6.65 km s1 layer and its replacement by a slower velocity. With the publishing of wide angle reflectionrefraction (WAR) profile 88-2, two pairs of lines are now available in the gulf that cross the craton into the orogen with both WAR and deep seismic reflection coverage. The combined data sets are used to distinguish the Grenville lower crustal block based on patterns of reflectivity and associated velocities. Near the Gaspé, the Grenville lower crustal block extends southwestward and, by extrapolation of the tectonostratigraphic zones offshore, underlies the Humber zone. In contrast, profiles in the gulf to the west of Newfoundland imply the continuous Grenville lower crustal block terminates seaward of the Humber surface terrane. Along-strike variations in the extent of Grenville lower crustal block beneath the northern Appalachians are suggested as an important factor in determining the style of crustal deformation.
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Pratt, Thomas L., James F. Dolan, Jackson K. Odum, William J. Stephenson, Robert A. Williams, and Mary E. Templeton. "Multiscale seismic imaging of active fault zones for hazard assessment: A case study of the Santa Monica fault zone, Los Angeles, California." GEOPHYSICS 63, no. 2 (1998): 479–89. http://dx.doi.org/10.1190/1.1444349.
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High‐resolution seismic reflection profiles at two different scales were acquired across the transpressional Santa Monica Fault of north Los Angeles as part of an integrated hazard assessment of the fault. The seismic data confirm the location of the fault and related shallow faulting seen in a trench to deeper structures known from regional studies. The trench shows a series of near‐vertical strike‐slip faults beneath a topographic scarp inferred to be caused by thrusting on the Santa Monica fault. Analysis of the disruption of soil horizons in the trench indicates multiple earthquakes have occurred on these strike‐slip faults within the past 50 000 years, with the latest being 1000 to 3000 years ago. A 3.8-km-long, high‐resolution seismic reflection profile shows reflector truncations that constrain the shallow portion of the Santa Monica Fault (upper 300 m) to dip northward between 30° and 55°, most likely 30° to 35°, in contrast to the 60° to 70° dip interpreted for the deeper portion of the fault. Prominent, nearly continuous reflectors on the profile are interpreted to be the erosional unconformity between the 1.2 Ma and older Pico Formation and the base of alluvial fan deposits. The unconformity lies at depths of 30–60 m north of the fault and 110–130 m south of the fault, with about 100 m of vertical displacement (180 m of dip‐slip motion on a 30°–35° dipping fault) across the fault since deposition of the upper Pico Formation. The continuity of the uncomformity on the seismic profile constrains the fault to lie in a relatively narrow (50 m) zone, and to project to the surface beneath Ohio Avenue immediately south of the trench. A very high‐resolution seismic profile adjacent to the trench images reflectors in the 15 to 60 m depth range that are arched slightly by folding just north of the fault. A disrupted zone on the profile beneath the south end of the trench is interpreted as being caused by the deeper portions of the trenched strike‐slip faults where they merge with the thrust fault.
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Paap, B. F., C. W. Dubelaar, J. L. Gunnink, and A. P. Oost. "Unraveling the shallow geology of the western Wadden Sea using high resolution seismics." Netherlands Journal of Geosciences - Geologie en Mijnbouw 91, no. 3 (2012): 341–55. http://dx.doi.org/10.1017/s0016774600000482.
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AbstractModelling of the shallow subsurface of the Dutch Wadden Sea is merely based on lithological information extracted from a limited amount of core samples. In order to improve the subsurface model and to provide a better basis for engineering purposes, seismic data have recently been acquired, processed and interpreted. This study focuses on the interpretation of seismic data in a pilot area in the southwestern part of the Dutch Wadden Sea near the Afsluitdijk. In order to acquire a maximum detail of subsurface information in a time-efficient way, multiple types of seismic systems were deployed simultaneously in a ‘one-sweep-survey’, providing information over depth ranges up to 60 m subsurface depth. Data from three seismic systems are presented; a chirp system, a boomer and sparker source in combination with hydrophone streamers. Geological interpretation of the seismic data was made by identifying seismic facies units and subsequently correlating them to geological cross-sections, running parallel to the Afsluitdijk. Geological cross-sections were derived from the existing geological and hydrogeological model and from relatively densely spaced borehole information. Six key reflectors were identified on the seismic data along the Dutch Afsluitdijk that make up four seismic facies units. Results of seismic profiles show good recognition of internal structures in especially Holocene sediments. A clay plug and a shallowing of a channel at the eastern side of the pilot area were interpreted as channel infills resulting from the rather sudden dominance by newer tidal channels to the west, probably coinciding with the opening of the Marsdiep channel. The channel wall deposits observed were interpreted as a turning of the drainage channel after closure of the IJsselmeer. Strong reflections of deeper levels (>15 m below Dutch vertical datum, i.e. N.A.P.) were interpreted as clay/sand interfaces in the Middle-Pleistocene Urk Formation and were more continuous than previously thought. It is concluded that high resolution seismics add valuable information yielding improved understanding of the sedimentary structure of the shallow subsurface, which in turn can be useful for near future engineering works along the Afsluitdijk.
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Beck, C., J. L. Reyss, F. Leclerc, et al. "Identification of deep subaqueous co-seismic scarps through specific coeval sedimentation in Lesser Antilles: implication for seismic hazard." Natural Hazards and Earth System Sciences 12, no. 5 (2012): 1755–67. http://dx.doi.org/10.5194/nhess-12-1755-2012.
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Abstract. During the GWADASEIS cruise (Lesser Antilles volcanic arc, February–March 2009) a very high resolution (VHR) seismic-reflection survey was performed in order to constrain Late Quaternary to Present faulting. The profiles we obtained evidence frequent "ponding" of reworked sediments in the deepest areas, similar to the deposition of Mediterranean "homogenites". These bodies are acoustically transparent (few ms t.w.t. thick) and are often deposited on the hanging walls of dominantly normal faults, at the base of scarps. Their thickness appears sufficient to compensate (i.e. bury) co-seismic scarps between successive earthquakes, resulting in a flat and horizontal sea floor through time. In a selected area (offshore Montserrat and Nevis islands), piston coring (4 to 7 m long) was dedicated to a sedimentological analysis of the most recent of these particular layers. It corresponds to non-stratified homogenous calcareous silty sand (reworked calcareous plankton and minor volcanoclastics). This layer can be up to 2 m thick, and overlies fine-grained hemipelagites. The upper centimeters of the latter represent the normal RedOx water/sediment interface. 210Pb and 137Cs activities lack in the massive sands, while a normal profile of unsupported 210Pb decrease is observed in the hemipelagite below, together with a 137Cs peak corresponding to the Atmospheric Nuclear Experiments (1962). The RedOx level was thus capped by a recent instantaneous major sedimentary event considered as post-1970 AD; candidate seismic events to explain this sedimentary deposits are either the 16 March 1985 earthquake or the 8 October 1974 one (Mw = 6.3 and Mw = 7.4, respectively). This leads to consider that the syntectonic sedimentation in this area is not continuous but results from accumulation of thick homogenites deposited after the earthquakes (as observed in the following weeks after Haiti January 2010 event, McHugh et al., 2011). The existence of such deposits suggests that, in the area of study, vertical throw likely results from cumulated effects of separated earthquakes rather than from aseismic creep. Examination of VHR profiles shows that all major co-seismic offsets are recorded in the fault growth sequence and that co-seismic offsets can be precisely estimated. By using a sedimentation rate deduced from 210Pb decrease curve (0.5 mm yr−1) and taking into account minor reworking events detected in cores, we show that the Redonda system may have been responsible for five >M6 events during the last 34 000 yr. The approach presented in this work differs from fault activity analyses using displaced sets of isochronous surfaces and postulating co-seismic offsets. Combining VHR seismic imagery and coring we can decipher co-seismic vs. slow continuous displacement, and thus actually estimate the amplitude and the time distribution of major co-seismic offsets.
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Chiu, Stephen K. L., and Robert R. Stewart. "Tomographic determination of three‐dimensional seismic velocity structure using well logs, vertical seismic profiles, and surface seismic data." GEOPHYSICS 52, no. 8 (1987): 1085–98. http://dx.doi.org/10.1190/1.1442374.
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A tomographic technique (traveltime inversion) has been developed to obtain a two‐ or three‐dimensional velocity structure of the subsurface from well logs, vertical seismic profiles (VSP), and surface seismic measurements. The earth was modeled by continuous curved interfaces (polynomial or sinusoidal series), separating regions of constant velocity or transversely isotropic velocity. Ray tracing for each seismic source‐receiver pair was performed by solving a system of nonlinear equations which satisfy the generalized Snell’s law. Surface‐to‐borehole and surface‐to‐surface rays were included. A damped least‐squares formulation provided the updating of the earth model by minimizing the difference between the traveltimes picked from the real data and calculated traveltimes. Synthetic results indicated the following conclusions. For noise‐free cases, the inversion converged closely from the initial guess to the true model for either surface or VSP data. Adding random noise to the observations and performing the inversion indicated that (1) using surface data alone allows reconstruction of the broad velocity structure but with some inaccuracy; (2) using VSP data alone gives a very accurate but laterally limited velocity structure; and (3) the integration of both data sets produces a more laterally extensive, accurate image of the subsurface. Finally, a field example illustrates the viability of the method to construct a velocity structure from real data.
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Behm, Michael, Feng Cheng, Anna Patterson, and Gerilyn S. Soreghan. "Passive processing of active nodal seismic data: estimation of <i>V</i><sub>P</sub>∕<i>V</i><sub>S</sub> ratios to characterize structure and hydrology of an alpine valley infill." Solid Earth 10, no. 4 (2019): 1337–54. http://dx.doi.org/10.5194/se-10-1337-2019.
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Abstract. The advent of cable-free nodal arrays for conventional seismic reflection and refraction experiments is changing the acquisition style for active-source surveys. Instead of triggering short recording windows for each shot, the nodes are continuously recording over the entire acquisition period from the first to the last shot. The main benefit is a significant increase in geometrical and logistical flexibility. As a by-product, a significant amount of continuous data might also be collected. These data can be analyzed with passive seismic methods and therefore offer the possibility to complement subsurface characterization at marginal additional cost. We present data and results from a 2.4 km long active-source profile, which have recently been acquired in western Colorado (US) to characterize the structure and sedimentary infill of an over-deepened alpine valley. We show how the “leftover” passive data from the active-source acquisition can be processed towards a shear wave velocity model with seismic interferometry. The shear wave velocity model supports the structural interpretation of the active P-wave data, and the P-to-S-wave velocity ratio provides new insights into the nature and hydrological properties of the sedimentary infill. We discuss the benefits and limitations of our workflow and conclude with recommendations for the acquisition and processing of similar datasets.
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Liang, Xiaofeng, Sicheng Zuo, Shilin Li, and Yongge Feng. "Burial Process of a Seismic Station by Moving Dunes in Tarim Basin." Seismological Research Letters 91, no. 5 (2020): 2936–41. http://dx.doi.org/10.1785/0220200116.
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Abstract A temporary seismometer vault was buried by a moving sand dune in the Taklimakan Desert at northwestern China in October 2019. The dune gradually covered the solar panel and the power supply to the seismic station was subsequently cut off. Here, we show that the burial process can be diagnosed according to the temperature record from the thermometer in the data-logger, an ultra-low-frequency seismic signal, and the change of high-frequency noise level from the continuous seismograms recorded by the broadband seismometer. The ultra-low-frequency seismic signal reflects the thermoelastic effect of the suspension spring in the seismometer corresponding to the temperature gradient in the sensor vault. At the same time, the variation of high-frequency noise level correlates well with the temperature profile and the ultra-low-frequency seismic signal, indicating the ground wind intensity. The peak frequency shifts and their different responses on three-component waveforms for the high-frequency noise might reflect the distance from the moving dunes to the station and their moving directions. This observation shows a potential usage of continuous seismograms to study rapid environment change around a temporary seismic station.
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Maxime Abbey, Assa, Loukou Nicolas Kouame, Lacine Coulibaly, Simon Pierre Djroh, and Boko Celestin Sombo. "STUDY OF THE ARCHITECTURE OF SEDIMENTARY DEPOSITS IN THE IVORIAN ONSHORE BASIN THROUGH SEISMIC REFLECTION." International Journal of Advanced Research 8, no. 12 (2020): 575–84. http://dx.doi.org/10.21474/ijar01/12186.
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The seismic profiles analysis of 4,533 km study area made it possible to study the sedimentary deposits in the Ivorian onshore basin. The method used consisted of manual plots of the seismic sections leading to the production of isochronos, iso-velocity, isobaths and isopac maps. As for the stratigraphic interpretation, it was used to develop a sedimentary model to extract information on the nature of sedimentary deposits and the mechanisms of their establishment based on the analysis of seismic facies. Examination of the different seismic profiles of the study area allowed the onshore sedimentary series to be subdivided into four main sequences which are: sequences I, II, III and IV. Thus, this analysis revealed two stages of sedimentary deposits linked to the behavior of the reflectors: 1. a syn-rift stage, characterized by significant fracturing in the sedimentation with faults and tilted blocks inthe Lower Cretaceous 2. a post-rift stage , corresponding to a less deformed sedimentation with parallel and continuous reflectors from the Upper Cretaceous to the present . These two phases allow us to understand the stratigraphic evolution of the onshore basin.
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Vargas-Cordero, I., U. Tinivella, F. Accaino, et al. "Basal and Frontal Accretion Processes versus BSR Characteristics along the Chilean Margin." Journal of Geological Research 2011 (September 12, 2011): 1–10. http://dx.doi.org/10.1155/2011/846101.
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Multichannel seismic reflection data recorded between Itata (36°S) and Coyhaique offshores (43°S) were processed to obtain seismic images. Analysis of the seismic profiles revealed that weak and discontinuous bottom simulating reflectors were associated to basal accretion processes, while strong and continuous bottom simulating reflectors were associated to frontal accretion processes. This can be explained considering that during basal accretion processes, extensional tectonic movements due to uplifting can favour fluid escapes giving origin to weaker and most discontinuous bottom simulating reflectors. During frontal accretion processes (folding and thrusting), high fluid circulation and stable tectonic conditions however can be responsible of stronger and most continuous bottom simulating reflectors. Along the Arauco-Valdivia offshores, steep accretionary prisms, normal faults, slope basins, and thicker underplated sediment bed were associated to basal accretion, while along the Itata, Chiloe and Coyhaique offshores, small accretionary prisms, folding, and thinner underplated sediment bed were associated to frontal accretion.
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Tary, Jean Baptiste, Mirko van der Baan, and Roberto Henry Herrera. "Applications of high-resolution time-frequency transforms to attenuation estimation." GEOPHYSICS 82, no. 1 (2017): V7—V20. http://dx.doi.org/10.1190/geo2016-0022.1.
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Attenuation estimates quantify the loss of energy of propagating seismic waves due to anelastic processes. It is often carried out in the frequency domain. The most well-known methods for attenuation estimation, such as the spectral ratio and frequency-shift methods, compare spectral shapes of waveforms along a given raypath. They require broad spectra such as those obtained with the Fourier transform and the continuous wavelet transform. These methods are incompatible with high-resolution time-frequency transforms, which drastically localize time-frequency information. On the other hand, these transforms indicate stronger resistance to noise and can be used in combination with the peak frequency method to estimate attenuation. We have applied high-resolution transforms, namely the synchrosqueezing transform, basis pursuit, and complete ensemble empirical-mode decomposition, to a synthetic wedge example and two seismic data set examples, a seismic reflection profile, and a vertical seismic profile (VSP). Results for the synthetic example find that most high-resolution transforms are able to reliably estimate quality factors. Using centroid frequencies, the seismic reflection profile exhibits local increases in centroid frequencies, which likely indicates imprints from apparent attenuation over intrinsic attenuation. Centroid frequencies and effective quality factors for the VSP are consistent for the different spectral estimation techniques. These three examples illustrate the value of high-resolution transforms for frequency and quality factor measurements.
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Calvert, Andrew J. "Continuous estimation of 3-D reflector orientations along 2-D deep seismic reflection profiles." Tectonophysics 718 (October 2017): 61–71. http://dx.doi.org/10.1016/j.tecto.2016.11.002.
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Paul, M. A., and L. M. Jobson. "Geotechnical properties of soft clays from the Witch Ground Basin, central North Sea." Geological Society, London, Engineering Geology Special Publications 7, no. 1 (1991): 151–56. http://dx.doi.org/10.1144/gsl.eng.1991.007.01.12.
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AbstractThe Witch Ground Basin to the northeast of Peterhead is occupied by Late to Postglacial clays which reach a maximum thickness of over forty metres. High resolution seismic surveys have shown that the Sediments can be divided into two stratigraphic units on the basis of their acoustic signatures: the upper Witch Ground Formation shows in its lower part a finely detailed pattern of laterally continuous multiple reflectors, whereas the lower Swatchway and Coal Pit Formations present a disorganised signature in which few reflectors are continuous.Profiles of bulk density, water content and undrained shear strength have been obtained from two continuously sampled, adjacent boreholes which penetrated the sediments to a depth of forty metres. These show that the deposits of the Witch Ground Basin comprise a single geotechnical unit with the properties expected of a fine grained sediment of glaciomarine origin. The principal geotechnical properties change gradationally as a result of changes in composition and from selfweight compression. The different seismic signatures on which the basin stratigraphy is based are not reflected by major geotechnical changes within the sediment, but may well result from secondary features of the geotechnical profile.
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Ouzandja, Toufiq, and Mohamed Hadid. "Sensitivity analysis of geotechnical site conditions effect on the seismic response of a saturated inhomogeneous poroviscoelastic soil profile." World Journal of Engineering 15, no. 6 (2018): 661–77. http://dx.doi.org/10.1108/wje-12-2017-0388.
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Purpose This paper aims to present the investigation of the linear and nonlinear seismic site response of a saturated inhomogeneous poroviscoelastic soil profile for different soil properties, such as pore-water saturation, non-cohesive fines content FC, permeability k, porosity n and coefficient of uniformity Cu. Design/methodology/approach The inhomogeneous soil profile is idealized as a multi-layered saturated poroviscoelastic medium and is characterized by the Biot’s theory, with a shear modulus varying continuously with depth according to the Wichtmann’s model. Seismic response analysis has been evaluated through a computational model, which is based on the exact stiffness matrix method formulated in the frequency domain assuming that the incoming seismic waves consist of inclined P-SV waves. Findings Unlike the horizontal seismic response, the results indicate that the vertical one is strongly affected by the pore water saturation. Moreover, in the case of fully saturated soil profile, the same vertical response spectra are found for the two cases of soil behavior, linear and nonlinear. Originality/value This research is a detailed study of the geotechnical soil properties effect on the bi-directional seismic response of saturated inhomogeneous poroviscoelastic soil profile, which has not been treated before; the results are presented in terms of the peak acceleration ratio, as well as the free-field response spectra and the spectral ratio (V/H).
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Clowes, Ron M., Colin A. Zelt, John R. Amor, and Robert M. Ellis. "Lithospheric structure in the southern Canadian Cordillera from a network of seismic refraction lines." Canadian Journal of Earth Sciences 32, no. 10 (1995): 1485–513. http://dx.doi.org/10.1139/e95-122.
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Lithospheric velocity structure and its relationship to regional tectonics and development of the southern Canadian Cordillera are derived from a synthesis of interpretations from nine in-line seismic refraction–wide-angle reflection profiles and broadside data recorded during the Lithoprobe Southern Cordillera Refraction Experiment (SCoRE) and other refraction experiments across southern British Columbia, and one profile in northwestern Washington. Consistency of the SCoRE two-dimensional models at their intersection positions is achieved through application of a simultaneous inversion of all relevant traveltime data. The cross-sectional and map presentations demonstrate the strong degree of three-dimensional heterogeneity within the crust and upper mantle. A first-order characteristic is the continuous increase in crustal velocities westward from the Foreland belt to the Insular belt. The variations do not correlate with the morphogeological belts; they do correspond with large-scale geological and (or) tectonic features and seismic reflection results. Crustal thickness varies from 30 to 48 km; a lack of comparable variation in Bouguer gravity anomalies requires significant density changes in the crust. Variations in the seismic parameters do not correlate well with variations in crustal resistivity or heat flow, suggesting that generalizations relating low resistivities, high temperatures, and low seismic velocities must be treated with caution. Seismic heterogeneities are due primarily to lithological and (or) structural variations and are superimposed on the generally low velocities attributed to the thermal regime. An upper mantle reflector beneath the mainland Cordillera is inferred to be the top of a shallow asthenosphere. Westward flow in the warm asthenosphere interacts with the cold lithosphere of the subducting Juan de Fuca plate below the central Coast belt, forming a "sink" that could provide a driving mechanism for the flow.
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Afonin, Nikita, Elena Kozlovskaya, Suvi Heinonen, and Stefan Buske. "Near-surface structure of the Sodankylä area in Finland, obtained by passive seismic interferometry." Solid Earth 12, no. 7 (2021): 1563–79. http://dx.doi.org/10.5194/se-12-1563-2021.
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Abstract. Controlled-source seismic exploration surveys are not always possible in nature-protected areas. As an alternative, the application of passive seismic techniques in such areas can be proposed. In our study, we show results of passive seismic interferometry application for mapping the uppermost crust in the area of active mineral exploration in northern Finland. We utilize continuous seismic data acquired by the Sercel Unite wireless multichannel recording system along several profiles during XSoDEx (eXperiment of SOdankylä Deep Exploration) multidisciplinary geophysical project. The objective of XSoDEx was to obtain a structural image of the upper crust in the Sodankylä area of northern Finland in order to achieve a better understanding of the mineral system at depth. The key experiment of the project was a high-resolution seismic reflection experiment. In addition, continuous passive seismic data were acquired in parallel with reflection seismic data acquisition. Due to this, the length of passive data suitable for noise cross-correlation was limited from several hours to a couple of days. Analysis of the passive data demonstrated that dominating sources of ambient noise are non-stationary and have different origins across the XSoDEx study area. As the long data registration period and isotropic azimuthal distribution of noise sources are two major conditions for empirical Green function (EGF) extraction under the diffuse field approximation assumption, it was not possible to apply the conventional techniques of passive seismic interferometry. To find the way to obtain EGFs, we used numerical modelling in order to investigate properties of seismic noise originating from sources with different characteristics and propagating inside synthetic heterogeneous Earth models representing real geological conditions in the XSoDEx study area. The modelling demonstrated that scattering of ballistic waves on irregular shape heterogeneities, such as massive sulfides or mafic intrusions, could produce a diffused wavefield composed mainly of scattered surface waves. In our study, we show that this scattered wavefield can be used to retrieve reliable EGFs from short-term and non-stationary data using special techniques. One of the possible solutions is application of “signal-to-noise ratio stacking” (SNRS). The EGFs calculated for the XSoDEx profiles were inverted, in order to obtain S-wave velocity models down to the depth of 300 m. The obtained velocity models agree well with geological data and complement the results of reflection seismic data interpretation.
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Büker, Frank, Alan G. Green, and Heinrich Horstmeyer. "Shallow seismic reflection study of a glaciated valley." GEOPHYSICS 63, no. 4 (1998): 1395–407. http://dx.doi.org/10.1190/1.1444441.
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Shallow seismic reflection data were recorded along two long (>1.6 km) intersecting profiles in the glaciated Suhre Valley of northern Switzerland. Appropriate choice of source and receiver parameters resulted in a high‐fold (36–48) data set with common midpoints every 1.25 m. As for many shallow seismic reflection data sets, upper portions of the shot gathers were contaminated with high‐amplitude, source‐generated noise (e.g., direct, refracted, guided, surface, and airwaves). Spectral balancing was effective in significantly increasing the strength of the reflected signals relative to the source‐generated noise, and application of carefully selected top mutes ensured guided phases were not misprocessed and misinterpreted as reflections. Resultant processed sections were characterized by distributions of distinct seismic reflection patterns or facies that were bounded by quasi‐continuous reflection zones. The uppermost reflection zone at 20 to 50 ms (∼15 to ∼40 m depth) originated from a boundary between glaciolacustrine clays/silts and underlying glacial sands/gravels (till) deposits. Of particular importance was the discovery that the deepest part of the valley floor appeared on the seismic section at traveltimes >180 ms (∼200 m), approximately twice as deep as expected. Constrained by information from boreholes adjacent to the profiles, the various seismic units were interpreted in terms of unconsolidated glacial, glaciofluvial, and glaciolacustrine sediments deposited during two principal phases of glaciation (Riss at >100 000 and Würm at ∼18 000 years before present).
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Ku, Taeseo, Paul W. Mayne, and Ethan Cargill. "Continuous-interval shear wave velocity profiling by auto-source and seismic piezocone tests." Canadian Geotechnical Journal 50, no. 4 (2013): 382–90. http://dx.doi.org/10.1139/cgj-2012-0278.
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A new exploratory procedure for collecting continuous shear wave velocity measurements via cone penetration testing using a special autoseis source is presented whereby wavelets can be generated and recorded every 1 to 10 s. The continuous-interval seismic piezocone test (CiSCPTu) offers a fast, productive, and reliable means to expedite the collection of downhole shear wave velocity profiles, as well as additional readings on cone tip resistance, sleeve friction, and penetration porewater pressures with depth. A site in Windsor, Virginia, is utilized for illustrating the collection of data, calibration, and post-processing issues arising from large numbers of wavelets that require filtering, windowing, and selection in both time and frequency domain analyses. At the test site, the geology consists of shallow Holocene deposits of clays and sands to 8 m that are underlain by much stiffer calcareous sandy marine clay soils of Miocene age, which extend beyond the termination depths of the soundings at 30 m.
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Sexton, John L., Harvey Henson, Paul Dial, and K. Shedlock. "Mini-Sosie High Resolution Seismic Reflection Profiles Along the Bootheel Lineament in the New Madrid Seismic Zone." Seismological Research Letters 63, no. 3 (1992): 297–307. http://dx.doi.org/10.1785/gssrl.63.3.297.
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Abstract Results of geological and geophysical research conducted in the New Madrid seismic zone since the early 1970’s indicate that much of the seismicity of the area is associated with late Precambrian age rift-related geological structures that have been reactivated by contemporary stresses. Deep seismic reflection surveys have been used to detect and delineate deeply buried geological structures thought to be associated with the seismicity. Satellite imagery and aerial photographs have recently been used to detect a linear feature named the Bootheel lineament inferred to be the surface expression of one of the faults responsible for the 1811–1812 earthquakes. To assess the seismogenic potential of these deep structures and linear features, high resolution seismic reflection and geomorphic studies are required. In July and August, 1990, Mini-Sosie high resolution reflection surveys were conducted in the New Madrid seismic zone. A total of 23 line-kilometers of high resolution reflection data were collected at nine locations. Specific targets for the new surveys include several locations on the Bootheel lineament in the New Madrid area, its northern projection near Sikeston, Missouri, and its southern projection near Blytheville, Arkansas at locations related to the Blytheville arch. A location several kilometers south of Charleston, Missouri, was also selected. Data presented in this paper consist of 7 line-kilometers recorded at locations on or close to the Bootheel lineament near New Madrid, Missouri, Hayti, Missouri, and Blytheville, Arkansas. Numerous small-offset faults, channels and other structures in Tertiary, Cretaceous and Paleozoic age rocks have been interpreted from the Mini-Sosie seismic sections. These structures, although generally not major features themselves, may be associated with deep seated rift-related reactivated structures. Many of the small-offset faults appear to deform or offset Quaternary age sediments. The spatial correlation of the observed faulting with sandblows and lineaments identified from aerial photographs, suggests the possibility that the observed faulting, sandblows, and linear features may be genetically related. If this is the case, then, because the origin of the sandblows has generally been attributed to the 1811–1812 seismic activity, the observed faulting may have been active at that time. It is not possible to directly link a single correlatable seismic signature with the Bootheel lineament, and thus we cannot state unequivocally that the lineament is continuous from Blytheville, Arkansas to New Madrid, Missouri. However, each seismic line has imaged similar small-offset faulting and gentle folding. If the faults and deformation observed are directly caused by reactivated deep structures associated with the Bootheel lineament, then, due to its great length, the total of which is yet undefined, this structure may be a source zone for major earthquakes, and therefore requires further investigations. The possibility exists, however, that the small scale faulting and deformation are ubiquitous throughout the New Madrid seismic zone. Additional high resolution seismic data are required to resolve this question.
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Schmitt, Douglas R. "Seismic attributes for monitoring of a shallow heated heavy oil reservoir: A case study." GEOPHYSICS 64, no. 2 (1999): 368–77. http://dx.doi.org/10.1190/1.1444541.
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In production geophysics, detecting the zones of production or constraining the in‐situ conditions within a reservoir are often of greater importance than obtaining highly resolved seismic structural images. Standard seismic data processing distorts the signal and limits the potential for extracting additional information, especially for shallow targets. An alternative “shift‐stack” procedure is applied in the processing of a shallow 12-fold, 1-m common midpoint (CMP) spacing reflection profile acquired over a heated Athabasca heavy oil sand reservoir. The shift‐stack involves summing of CMP traces which have been flattened to an appropriate reference event. Simple modeling confirms that the prestack waveforms are better preserved by this process. Amplitude and frequency attributes are extracted from the reflection profile. Amplitudes of a continuous reservoir event vary by 600% over 35-m intervals along the profile. Bright spots correlate with heated regions. Apparent frequencies, as measured by the instantaneous frequency and by short time‐window power spectral estimates of the subreservoir event are 20–30 Hz lower in these same regions. These diminished apparent frequencies most probably result from interference of the subreservoir reflection with events related to structural changes within the reservoir. A complete interpretation of the results has not been attempted as knowledge of the in‐situ conditions is incomplete. However, changes in the seismic response at the well locations suggest that these attributes are useful in detection and mapping of heated zones. The shiftstack procedure may also be useful in environmental and geotechnical applications.
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Sun, Langqiu F., Bernd Milkereit, and Douglas R. Schmitt. "Measuring velocity dispersion and attenuation in the exploration seismic frequency band." GEOPHYSICS 74, no. 2 (2009): WA113—WA122. http://dx.doi.org/10.1190/1.3068426.
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No perfectly elastic medium exists in the earth. In an anelastic medium, seismic waves are distorted by attenuation and velocity dispersion. Velocity dispersion depends on the petrophysical properties of reservoir rocks, such as porosity, fractures, fluid mobility, and the scale of heterogeneities. However, velocity dispersion usually is neglected in seismic data processing partly because of the insufficiency of observations in the exploration seismic frequency band (∼5 through [Formula: see text]). The feasibility of determining velocity dispersion in this band is investigated. Four methods are used in measuring velocity dispersion from uncorrelated vibrator vertical seismic profile (VSP) data: the moving window crosscorrelation (MWCC) method, instantaneous phase method, time-frequency spectral decomposition method, and cross-spectrum method. The MWCC method is a new method that is satisfactorily robust, accurate, and efficient in measuring the frequency-dependent traveltime in uncorrelated vibrator records. The MWCC method is applied to the uncorrelated vibrator VSP data acquired in the Mallik gas hydrate research well. For the first time, continuous velocity dispersion is observed in the exploration seismic frequency band using uncorrelated vibrator VSP data. The observed velocity dispersion is fitted to a straight line with respect to log frequency to calculate [Formula: see text]. This provides an alternative method for [Formula: see text] measurement.
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Ryaboy, Vladislav. "Upper mantle structure along a profile from Oslo (NORESS) to Helsinki to Leningrad, based on explosion seismology." Bulletin of the Seismological Society of America 80, no. 6B (1990): 2194–213. http://dx.doi.org/10.1785/bssa08006b2194.
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Abstract Waveforms from the NORESS array were analyzed for 147 industrial explosions during the 1985 to 1988 period, along a profile running east from Oslo (NORESS) to Helsinki to Leningrad (OHL profile). The events were 250 to 1300 km from NORESS and had local magnitude in the range 2.0 to 3.5. Event locations and origin times constrained by the University of Helsinki's regional seismic network provide a reliable basis for travel-time estimation at NORESS. We also used data recorded by NORSAR in 1979 for three shots on the FENNOLORA north-south, long-range seismic profile, which were near the OHL profile. Analysis of mantle P-wave signals from the explosions showed that first arrivals could be traced continuously to a distance of 750 to 800 km, where there is a cutoff and shift of approximately 2.0 to 2.5 sec in the travel-time curve and an increase in average apparent velocity. Interpretation of the observed travel times and waveforms for this profile suggests a low-velocity zone from approximately 105 to 135 km depth. Combined analysis of the seismic data with a Bouguer gravity map indicates the presence in the upper mantle of a high-velocity, high-density body of linear extent approximately from 200 to 300 to 500 to 600 km east of the NORESS array. It is postulated that this body may represent the root of an ancient volcanic system, in which lighter, silicic constituents were depleted from the upper mantle during the eruptive phase.
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Piana Agostinetti, Nicola, Francesca Martini, and Joe Mongan. "Sedimentary basin investigation using receiver function: an East African Rift case study." Geophysical Journal International 215, no. 3 (2018): 2105–13. http://dx.doi.org/10.1093/gji/ggy405.
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SUMMARY We apply receiver function (RF) methodology to map the geometry of a sedimentary basin along a ∼10-km-long profile of broadband seismometers that recorded continuously for approximately 3 months. For a subset of the stations, we apply the Neighbourhood Algorithm inversion scheme, to quantify the geometry of basin bounding fault directly beneath the stations. We compare our results with active reflection seismic data and with the lithostratigraphy from a well located along the profile. We find that the P-to-s conversions from the sediments–basement interface (SBI), recorded in RF data sets together with information on intrabasin structures, are useful for obtaining high resolution images of the basin. The depth of the SBI derived from RF inversion is consistent (within ∼0.4 km) with the estimates from active reflection seismic and the well data. This study highlights that analysis of teleseismic waveforms can retrieve relevant information on the structure of a sedimentary basin.
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Sysoev, A. P. "JUSTIFICATION OF PARAMETERS OF THE 2D CDP FIELD SYSTEM." Geology and mineral resources of Siberia, no. 3 (2020): 59–65. http://dx.doi.org/10.20403/2078-0575-2020-3-59-65.
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When performing seismic observations, 2D seismograms of a common shot point are represented as a discrete function of two variables, i.e. time and receiver – source offset. When recording a wave field using single seismic receivers placed small distance apart (UniQ technology), two goals are pursued : maintaining high frequencies of reflected signals by eliminating the effect of microstatics and fulfilling the Kotelnikov sampling theorem when discretizing a continuous field with respect to a spatial variable, thereby eliminating the effect of spatial aliasing of regular interference waves. At the stage of digital processing, this allows to solve the problem of extracting useful signals and suppressing noise more effectively. Taking the idea of a close array of receivers as a whole, it is proposed to optimize the profile observation system by source – receiver spacing combining analog and digital grouping of seismic receivers. In this case, the spatial sampling of the field is determined by the distance between the centers of receiver groups, and the parameters of the analog – digital grouping are calculated from the condition of suppressing spatial aliasing frequencies. Based on the analysis of static corrections obtained during processing of previous seismic studies, a method is proposed for assessing the effect of lateral microstatics variations on the results of analog grouping.
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Smith, N. J. P., and A. W. A. Rushton. "Cambrian and Ordovician stratigraphy related to structure and seismic profiles in the western part of the English Midlands." Geological Magazine 130, no. 5 (1993): 665–71. http://dx.doi.org/10.1017/s0016756800020975.
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AbstractIn England the Cambrian successions include relatively continuous, dominantly argillaceous sequences (Nuneaton area, > 900 m thick) and arenaceous successions punctuated by hiatuses (Malvern, Shropshire). The Tremadoc (lower Ordovician) succeeds paraconformably; it is widespread, dominantly argillaceous and locally very thick (> 2000 m). Deposition of the lower Tremadoc is thought to have been rapid. Uplift of regional extent occurred in early Ordovician (post-Tremadoc) times and inversion of the basins, such as the Tremadoc Worcester Graben, occurred during the Variscan Orogeny. The disposition of the Cambrian–Tremadoc beneath the Upper Llandovery unconformity is thought to reflect the arrangement of basins and highs at that time. Evidence from seismic profiles indicates deposition in half-grabens. In the Welsh Borderland, evidence from outcrops and boreholes suggests that the St David's Series (Middle Cambrian) is locally thickened against syn-depositional faults. The thinning and local absence of the St David's Series across such faults is attributed to the influence of tilt-block highs. Rifting and tilting allowed thick Tremadoc to accumulate (e.g. in a precursor Worcester Graben), but evidence for the direction of thickening is masked by lack of seismic markers and by the effect of pre-landovery erosion.
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Rutkowski, Jacek, Katarzyna Król, and Jadwiga Szczepańska. "Lithology of the Profundal Sediments in Słupiańska Bay (Wigry Lake, NE Poland) - Introduction to Interdisciplinary Study." Geochronometria 27, no. -1 (2007): 47–52. http://dx.doi.org/10.2478/v10003-007-0020-3.
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Lithology of the Profundal Sediments in Słupiańska Bay (Wigry Lake, NE Poland) - Introduction to Interdisciplinary Study In this paper, a lithological study taking into account trace metals of the profundal sediments from Słupiańska Bay in Wigry Lake is presented. A profile 5.26 m long has sandy muds at the bottom and moving upwards layers of calcareous gyttja, lacustrine chalk, and again calcareous gyttja are present. The profile is continuous, typical for the sediments of NE Poland formed from Allerøde to recent time. The results of the lithological analysis were correlated with results of high-resolution seismic survey. The results together with radiocarbon dating are part of interdisciplinary complex research comprising paleobiological study of pollen, Cladocera, diatom successions and human activity, which will be published in successive papers.
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Vejbæk, Ole Valdemar, and Rasmus Rasmussen. "Forward modelling of seismic response from North Sea Chalk." Geological Survey of Denmark and Greenland (GEUS) Bulletin 7 (July 29, 2005): 17–20. http://dx.doi.org/10.34194/geusb.v7.4824.
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Seismic inversion has become a standard tool for porosity prediction in chalk exploration and field development. AVO (amplitude versus offset) processing for fluid prediction is, however, still not widely applied in chalk. Forward modelling may help to assess the value of acquiring these data, as well as support subsequent interpretation. This paper presents a forward modelling tool to simulate seismic response resulting from changes in degree of compaction and fluid contents in profiles. Modelling is carried out with software developed by Norsk Hydro A/S (the Compound Model Builder), where the Geological Survey of Denmark and Greenland has supplied special capabilities to model North Sea Chalk. The forward modelling is illustrated with a seismic line straddling the Dan and Halfdan chalk fields (Fig. 1). Hydrocarbons are found in the uppermost Danian and Maastrichtian chalk where porosity may exceed 30%. Production takes place from wells centred on an anticline in the Dan Field, and although structural closure is lacking for the Halfdan Field, a surprising laterally continuous oil column is found between the two fields (e.g. Jacobsen et al. 1999; Albrechtsen et al. 2001).The modelling target is the effect on seismic data of such oil occurrences. The rather subtle impact on rock properties requires very realistic and detailed modelling. Fortunately, the pelagic deep-water origin of the chalk makes it very uniform laterally, such that compaction effects and fluid changes handled by the modelling tool account for lateral seismic changes, whereas well data support vertical changes.
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Price, Audrey C., Edward W. Woolery, Ronald C. Counts, et al. "Quaternary Displacement on the Joiner Ridge Fault, Eastern Arkansas." Seismological Research Letters 90, no. 6 (2019): 2250–61. http://dx.doi.org/10.1785/0220190149.
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ABSTRACT The New Madrid seismic zone of the central United States is an intraplate seismic zone with blind structures that are not seismically active but may pose seismic hazards. The Joiner ridge fault (JRF) is the 35‐kilometer‐long east‐bounding fault of the Joiner ridge blind horst located in eastern Arkansas ∼50 km northwest of Memphis, Tennessee. Shallow S‐wave (SH‐mode) seismic reflection profiles, continuous cores, and radiometric dating of Quaternary alluvium across the JRF reveal down‐to‐the‐east reverse faulting and folding of Eocene strata and overlying Quaternary Mississippi River alluvium. The base of the Quaternary alluvium has an age of 20.3 ka and is vertically displaced 12 m, resulting in an average slip rate of 0.6±0.1 mm/yr over the past 20.3 ka. The overlying upper Wisconsinan and Holocene alluvial facies are also displaced by the JRF. These facies increase in thickness across the JRF and were used to calculate late Wisconsinan and Holocene slip histories. The JRF slipped 7 m between 20.3 and 17.5 ka, 3 m between 12.3 and 11.5 ka, and 2 m between 11.5 and 8.9 ka. No apparent slip occurred on the JRF within the last 8.9 ka. This research illustrates that slip has been intermittent and that slip magnitudes on the JRF diminished through the late Wisconsinan and early Holocene.
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Cowan, Ellen A., Paul R. Carlson, and Ross D. Powell. "The marine record of the Russell Fiord outburst flood, Alaska, U.S.A." Annals of Glaciology 22 (1996): 194–99. http://dx.doi.org/10.3189/1996aog22-1-194-199.
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The advance of Hubbard Glacier, near Yakutat, Alaska, U.S.A., in spring 1986 blocked the entrance to Russell Fiord with an ice-and-sediment dam, behind which a lake formed. The water level in Russell Lake rose to 25.5 m a.s.l. The dam catastrophically failed in October 1986, releasing 5.4 km3 of water into Disenchantment Bay. High-resolution seismic-reflection profiles show a 7.5 km long channel system cut into and buried by glacimarine sediment, represented by continuous, parallel reflections. The chaotic seismic facies filling the channel is interpreted to be debris flow deposits. A gravity core from channel-overbank deposits contained sandy diamicton with mud clasts. Above the channel a 1–2 m thick sediment drape extends across the bay. Laminated mud, fining-upward sand beds and diamicton were recovered from this unit. The sediment-drape deposits were produced by suspension settling from turbid plumes and non-channelized turbidity currents generated by the outburst flood.
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Cowan, Ellen A., Paul R. Carlson, and Ross D. Powell. "The marine record of the Russell Fiord outburst flood, Alaska, U.S.A." Annals of Glaciology 22 (1996): 194–99. http://dx.doi.org/10.1017/s026030550001541x.
Full textAbstract:
The advance of Hubbard Glacier, near Yakutat, Alaska, U.S.A., in spring 1986 blocked the entrance to Russell Fiord with an ice-and-sediment dam, behind which a lake formed. The water level in Russell Lake rose to 25.5 m a.s.l. The dam catastrophically failed in October 1986, releasing 5.4 km3of water into Disenchantment Bay. High-resolution seismic-reflection profiles show a 7.5 km long channel system cut into and buried by glacimarine sediment, represented by continuous, parallel reflections. The chaotic seismic facies filling the channel is interpreted to be debris flow deposits. A gravity core from channel-overbank deposits contained sandy diamicton with mud clasts. Above the channel a 1–2 m thick sediment drape extends across the bay. Laminated mud, fining-upward sand beds and diamicton were recovered from this unit. The sediment-drape deposits were produced by suspension settling from turbid plumes and non-channelized turbidity currents generated by the outburst flood.
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Dwairi, Hazim, and Mervyn Kowalsky. "Implementation of Inelastic Displacement Patterns in Direct Displacement-Based Design of Continuous Bridge Structures." Earthquake Spectra 22, no. 3 (2006): 631–62. http://dx.doi.org/10.1193/1.2220577.
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Through the use of nonlinear time-history analysis, the displacement patterns of bridges subjected to transverse seismic attack are investigated. The variables considered in the study consist of bridge geometry, superstructure stiffness, substructure strength and stiffness, abutment support conditions, and earthquake ground motion. A series of three inelastic displacement pattern scenarios were identified: (1) rigid body translation (2) rigid body translation with rotation, and (3) flexible pattern. A relative stiffness index that is a function of the superstructure and substructure stiffness was shown to be a key variable in determining the type of displacement pattern a bridge is likely to follow. The results described in this paper have significant implications for performance-based seismic design procedures such as direct displacement-based design (DDBD). If the displacement pattern for a bridge can be identified with significant confidence at the start of the design process, application of approaches such as DDBD can be simplified. However, if the characteristics of the bridge are such that prescribing a pattern at the start of the process is not feasible, then an alternative approach must be employed for DDBD to proceed. Of the three displacement pattern scenarios defined in this paper, the first two require minimal effort in the design. For the third scenario, an iterative algorithm is proposed. Lastly, as a means for verification and demonstration, a series of bridges with various configurations was designed using DDBD for rigid body translation and flexible pattern scenarios. The designs for the flexible scenario showed good agreement with selected target profiles for bridges with up to five spans.
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Bianchi, Irene, Elmer Ruigrok, Anne Obermann, and Edi Kissling. "Moho topography beneath the European Eastern Alps by global-phase seismic interferometry." Solid Earth 12, no. 5 (2021): 1185–96. http://dx.doi.org/10.5194/se-12-1185-2021.
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Abstract. In this work we present the application of the global-phase seismic interferometry (GloPSI) technique to a dataset recorded across the Eastern Alps with the EASI (Eastern Alpine Seismic Investigation) temporary seismic network. GloPSI aims at rendering an image of the lithosphere from the waves that travel across the core before reaching the seismic stations (i.e. PKP, PKiKP, PKIKP). The technique is based on the principle that a stack of autocorrelations of transmission responses mimics the reflection response of a medium and is used here to retrieve information about the crust–mantle boundary, such as its depth and topography. We produce images of the upper lithosphere using 64 teleseismic events. We notice that with GloPSI, we can well image the topography of the Moho in regions where it shows a nearly planar behaviour and corresponds to a strong velocity contrast (i.e. in the northern part of the profile, from the Bohemian Massif to the Northern Calcareous Alps). Below the higher crests of the Alpine chain, and the Tauern Window in particular, we cannot find evidence of the boundary between crust and mantle. The GloPSI results indicate the absence of an Adriatic crust made of laterally continuous layers smoothly descending southwards and confirm the observations of previous studies suggesting a structurally complex and faulted internal Alpine crustal structure.
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Limberger, Fabian, Michael Lindenfeld, Hagen Deckert, and Georg Rümpker. "Seismic radiation from wind turbines: observations and analytical modeling of frequency-dependent amplitude decays." Solid Earth 12, no. 8 (2021): 1851–64. http://dx.doi.org/10.5194/se-12-1851-2021.
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Abstract. In this study, we determine spectral characteristics and amplitude decays of wind turbine induced seismic signals in the far field of a wind farm (WF) close to Uettingen, Germany. Average power spectral densities (PSDs) are calculated from 10 min time segments extracted from (up to) 6 months of continuous recordings at 19 seismic stations, positioned along an 8 km profile starting from the WF. We identify seven distinct PSD peaks in the frequency range between 1 and 8 Hz that can be observed to at least 4 km distance; lower-frequency peaks are detectable up to the end of the profile. At distances between 300 m and 4 km the PSD amplitude decay can be described by a power law with exponent b. The measured b values exhibit a linear frequency dependence and range from b=0.39 at 1.14 Hz to b=3.93 at 7.6 Hz. In a second step, the seismic radiation and amplitude decays are modeled using an analytical approach that approximates the surface wave field. Since we observe temporally varying phase differences between seismograms recorded directly at the base of the individual wind turbines (WTs), source signal phase information is included in the modeling approach. We show that phase differences between source signals have significant effects on the seismic radiation pattern and amplitude decays. Therefore, we develop a phase shift elimination method to handle the challenge of choosing representative source characteristics as an input for the modeling. To optimize the fitting of modeled and observed amplitude decay curves, we perform a grid search to constrain the two model parameters, i.e., the seismic shear wave velocity and quality factor. The comparison of modeled and observed amplitude decays for the seven prominent frequencies shows very good agreement and allows the constraint of shear velocities and quality factors for a two-layer model of the subsurface. The approach is generalized to predict amplitude decays and radiation patterns for WFs of arbitrary geometry.
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Lozano, Lucía, Juan Vicente Cantavella, and Jaime Barco. "A new 3-D P-wave velocity model for the Gulf of Cadiz and adjacent areas derived from controlled-source seismic data: application to nonlinear probabilistic relocation of moderate earthquakes." Geophysical Journal International 221, no. 1 (2019): 1–19. http://dx.doi.org/10.1093/gji/ggz562.
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SUMMARY The SW Iberian margin is well known for its complex tectonic setting and crustal structure and by the occurrence of moderate magnitude earthquakes and some great tsunamigenic earthquakes. Fortunately, many seismic reflection and refraction profiles have been carried out, providing detailed information about the crustal structure of the main geologic domains in this region. These studies show a first-order variation due to the transition from oceanic to continental domain, large-scale heterogeneities within the crust and an irregular Moho topography. Routine earthquake locations in this area have been usually computed using a general 1-D velocity model which is clear that cannot account for such a heterogeneous structure. In addition, regional seismic stations used to locate the Gulf of Cadiz seismicity are on land and far away to the east, implying large azimuthal gaps and distances. In this context, a 3-D approach seems necessary to properly solve the crustal velocity field and improve earthquake location in this area. With this purpose, we present a new digital 3-D P-wave velocity distribution for the crust and uppermost mantle derived from previously published controlled-source seismic experiments carried out in SW Iberia and the Gulf of Cadiz over the last 40 yr. We have reviewed more than 50 wide-angle and multichannel seismic reflection and refraction profiles and digitized the most significant published 2-D seismic velocity models, performing an updated compilation of crustal parameters (P-wave velocities and geometry and depth of the main crustal interfaces). These velocities as a function of position and depth have been interpolated using ordinary kriging algorithm to obtain, in the form of a regular georeferenced 20 × 20 × 1 km grid spacing, a high-resolution 3-D P-wave velocity distribution for the crust and uppermost mantle and a continuous Moho depth map of the whole area of this study (33°N–41°N latitude and 15°W–5°W longitude). Since current seismic location tools allow the implementation of 3-D grid structures, we have applied our 3-D model to relocate a selection of moderate earthquakes occurred in the studied region using a probabilistic nonlinear method. In the Gulf of Cadiz area the probabilistic approximation provides maximum likelihood hypocentres located within the uppermost mantle with the majority of depths ranging between 20 and 45 km. This model would subsequently be implemented at the Spanish Seismic Network for the routine relocation of the seismicity of the area.
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Chmiel, M., A. Mordret, P. Boué, et al. "Ambient noise multimode Rayleigh and Love wave tomography to determine the shear velocity structure above the Groningen gas field." Geophysical Journal International 218, no. 3 (2019): 1781–95. http://dx.doi.org/10.1093/gji/ggz237.
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SUMMARY The Groningen gas field is one of the largest gas fields in Europe. The continuous gas extraction led to an induced seismic activity in the area. In order to monitor the seismic activity and study the gas field many permanent and temporary seismic arrays were deployed. In particular, the extraction of the shear wave velocity model is crucial in seismic hazard assessment. Local S-wave velocity-depth profiles allow us the estimation of a potential amplification due to soft sediments. Ambient seismic noise tomography is an interesting alternative to traditional methods that were used in modelling the S-wave velocity. The ambient noise field consists mostly of surface waves, which are sensitive to the Swave and if inverted, they reveal the corresponding S-wave structures. In this study, we present results of a depth inversion of surface waves obtained from the cross-correlation of 1 month of ambient noise data from four flexible networks located in the Groningen area. Each block consisted of about 400 3-C stations. We compute group velocity maps of Rayleigh and Love waves using a straight-ray surface wave tomography. We also extract clear higher modes of Love and Rayleigh waves. The S-wave velocity model is obtained with a joint inversion of Love and Rayleigh waves using the Neighbourhood Algorithm. In order to improve the depth inversion, we use the mean phase velocity curves and the higher modes of Rayleigh and Love waves. Moreover, we use the depth of the base of the North Sea formation as a hard constraint. This information provides an additional constraint for depth inversion, which reduces the S-wave velocity uncertainties. The final S-wave velocity models reflect the geological structures up to 1 km depth and in perspective can be used in seismic risk modelling.
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Fruehn, Juergen, Moritz M. Fliedner, and Robert S. White. "Integrated wide‐angle and near‐vertical subbasalt study using large‐aperture seismic data from the Faeroe—Shetland region." GEOPHYSICS 66, no. 5 (2001): 1340–48. http://dx.doi.org/10.1190/1.1487079.
Full textAbstract:
Acquiring large‐aperture seismic data (38 km maximum offset) along a profile crossing the Faeroe—Shetland basin in the North Atlantic enables us to use wide‐angle reflections and refractions, in addition to conventional streamer data (0–6 km), for subbasalt imaging. The wide‐angle results are complemented and confirmed by images obtained from the conventional near‐vertical‐offset range. Traveltime tomography applied to the wide‐angle data shows a low‐velocity layer (3.5–4.5 km/s) underneath southeastward‐thinning lava flows, suggesting a 2.5–3.0‐km‐thick sedimentary layer. The velocity model obtained from traveltime tomography is used to migrate wide‐angle reflections from large offsets that arrive ahead of the water‐wave cone. The migrated image shows base‐basalt and sub—basalt reflections that are locally coincident with the tomographic boundaries. Application of a new multiple suppression technique and controlled stacking of the conventional streamer data produces seismic sections consistent with the wide‐angle results. Prestack depth migration of the near‐vertical offsets shows a continuous base‐basalt reflection and a clearly defined termination of the basalt flows.
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Lichman, Eugene, and E. John Northwood. "High‐resolution velocity notch filter without Gibbs effect." GEOPHYSICS 62, no. 1 (1997): 274–87. http://dx.doi.org/10.1190/1.1444128.
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A new technique has been developed to reject or pass constant velocity coherent energy. Compared to the widely used frequency‐wavenumber (ο‐k) filtering method, this technique does not show either spatial aliasing or Gibbs effect. The filter operator is designed analytically as an infinite continuous function in the ο‐k domain. This function has the property that, when transformed by the integral inverse Fourier transform into the time‐space (t‐x) domain, it becomes a short discrete function with the same properties as the continuous infinite function in the ο‐k domain. No sampling or truncation of the filter operator is needed, hence no Gibbs oscillations are introduced into the operator impulse response or into the filtered data. Because of the extremely high‐velocity resolution and dynamic range of the designed coherent energy filter, it is particularly useful for the up‐ and downgoing energy separation on the vertical seismic profile data and for the peg‐leg multiples attenuation.
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Muyzert, Everhard. "Seabed property estimation from ambient-noise recordings: Part I — Compliance and Scholte wave phase-velocity measurements." GEOPHYSICS 72, no. 2 (2007): U21—U26. http://dx.doi.org/10.1190/1.2435587.
Full textAbstract:
The ability to derive a near-surface shear-velocity profile from ambient-noise records is useful for seismic applications such as shear-wave statics estimation and geohazard prediction. Measurements of seafloor compliance and Scholte wave velocity and amplitude are all related to the near-surface shear-velocity profile. I analyzed a data set of [Formula: see text] of continuous noise records recorded by an ocean bottom cable deployed in [Formula: see text] deep water for seafloor compliance and Scholte waves. I failed to observe seafloor compliance because of limitations in the record length. I have detected Scholte waves on the inline and vertical component geophones and Love waves on the crossline component using [Formula: see text] spectra. Both the Scholte and Love wave phase-velocities can be explained by a simple 1D isotropic near-surface model. The Scholte waves may have been excited by acoustic energy from the recording vessel, while no satisfactory excitation mechanism has been found for the Love waves.
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Kiernan, Michael, Dan Jackson, Jack Montgomery, J. Brian Anderson, Brannon W. McDonald, and Kaye Chancellor Davis. "Characterization of a Karst Site using Electrical Resistivity Tomography and Seismic Full Waveform Inversion." Journal of Environmental and Engineering Geophysics 26, no. 1 (2021): 1–11. http://dx.doi.org/10.32389/jeeg20-045.
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Karst geology is characterized by the presence of sinkholes and voids, which may pose significant risk to existing infrastructure. Sinkhole formation is often observed near active quarries, where dewatering operations can alter regional groundwater flow patterns leading to subsidence and increased void formation. In these areas, identifying locations which may be susceptible to sinkhole formation requires an ability to map dissolution features within the rock. Traditional geotechnical explorations alone are not well-suited to this effort as they only provide subsurface information at discrete points and therefore may miss voids within the rock. Geophysical methods offer a means to produce continuous profiles of the rock surface and possible locations for voids but interpreting the results of these tests in karstic geology can be challenging. This study uses 2D electrical resistivity and seismic surveys at a site with previous sinkhole activity along an interstate in central Alabama. The site is adjacent to a limestone quarry. Resistivity data is collected using 2D dipole-dipole and strong-gradient arrays. The seismic data is processed using a full waveform inversion (FWI) technique. Subsurface profiles interpreted from the geophysical surveys are then compared to borehole data from previous site investigations. Results from the geophysical surveys are found to be consistent with borehole data regarding variation of bedrock depth and identification of possible sinkhole features. Potential limitations and sources of error pertaining to each survey type are considered.
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Kellett, R. L., A. E. Barnes, and M. Rive. "The deep structure of the Grenville Front: a new perspective from western Quebec." Canadian Journal of Earth Sciences 31, no. 2 (1994): 282–92. http://dx.doi.org/10.1139/e94-027.
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The Grenville Front is a major tectonic boundary exposed on the Canadian Shield. The front is defined as the northwestern limit of Grenvillian deformation, on the basis of geochronological and metamorphic data. This boundary is also evident in some geophysical data sets. The Lithoprobe Abitibi–Grenville transect crosses the Grenville Front near Lac Témiscamingue in western Quebec. A new 114 km long deep seismic reflection line shows a crustal structure quite different from that seen on previous surveys across the Grenville Front. The Archean foreland (Pontiac Subprovince) has a pattern of reflectivity similar to that seen in most of the Superior Province. This pattern continues for some 30 km south of the surface exposure of the Grenville Front. There is no evidence for a band of dipping reflectors truncating the horizontal Pontiac reflectors; in fact, the leading edge of the Grenville Province is difficult to identify on the seismic section. The Moho is well defined and reveals that the crust thins under the Grenville Front. The magnetotelluric survey shows that the upper crust is resistive across the entire profile, but the resistivity is higher within a Grenvillian allochthonous terrane at the southern end of the profile. The mid-crustal low-resistivity layer and the upper mantle electrical anisotropy are also continuous across the Grenville Front. The Grenville Front is highly variable in its character along the Grenville Orogen, and this character may be strongly controlled by the nature of the foreland to the northwest.
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Ortiz-Sanguino, Laura, Javier Tellez, Heather Bedle, and Dilan Martinez-Sanchez. "Seismic characterization of a blocky mass-transport deposit in the Trealla Limestone Formation, North Carnarvon Basin, Australia." Interpretation 8, no. 4 (2020): SR53—SR58. http://dx.doi.org/10.1190/int-2020-0049.1.
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The deepwater Cenozoic strata in the North Carnarvon Basin, Australia, represent an interval of interest for stratigraphic studies in passive margins settings of mixed siliciclastic-carbonate environments. We have explored the geomorphological characteristics of a mass-transport deposit (MTD) within the Trealla Limestone Formation to describe in detail the differences among the blocks. To characterize the individual geometry and structural configuration of the blocks within the MTD, we used geometric seismic attributes such as coherence, curvature, dip azimuth, and dip magnitude using horizon slices and vertical profiles. The evaluation finds two types of blocks: remnant and glide (or rafted) blocks. Remnant blocks are in situ and stratigraphically continuous fragments with the underlying strata. This type of block is frequently fault-bounded and displays low deformation evidence. Glide blocks are part of the transported material detached from a paleoslope. These blocks are deformed and occasionally appear as “floating” fragments embedded within a chaotic matrix in the MTD. Glide blocks are used as kinematic indicators of the direction of deposition of MTDs. We evaluate these elements in a modern continental analog that resembles a similar setting for a better understanding of the slide occurrence. Geological feature: Glide blocks, North Carnarvon Basin, Australia Seismic appearance: Discrete angular blocks with internal reflectors Alternative interpretations: Differential dissolution in a mixed siliciclastic-carbonate environment Features with a similar appearance: Carbonate buildups, differential dissolution blocks Formation: Trealla Limestone Formation, North Carnarvon Basin Age: Early-Middle Miocene Location: Offshore Northwest Australia, North Carnarvon Basin Seismic data: Obtained from Western Australian Petroleum and Geothermal Information Management System, Draeck 3D seismic data set Analysis tools: Visualization software (Petrel 2019) and attribute performance software (AASPI 6.0)
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ΣΑΚΕΛΛΑΡΙΟΥ, Δ., Γ. ΡΟΥΣΑΚΗΣ, Χ. ΚΡΑΝΗΣ, Ε. ΚΑΜΠΕΡΗ, Π. ΓΕΩΡΓΙΟΥ, and Ν. ΣΚΟΥΛΙΚΙΔΗΣ. "Neotectonic movements, sedimentation and water-level fluctuation of the Lake Vegoritis in Upper Quaternary." Bulletin of the Geological Society of Greece 34, no. 1 (2001): 207. http://dx.doi.org/10.12681/bgsg.17015.
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Lake Vegoritis is a 20km long lake located within the NE-SW oriented, Late Pliocene - Quaternary Vegoritis neotectonic depression. More than 200km of high resolution Boomer profiles provided valuable data on the recent evolution of the area. Two main seismic units separated from each other by an erosional surface (Reflector "W") were recognized in the upper 50-60m below the lakebed. The upper seismic unit is an onlapping basin fill characterized by parallel, sub-horizontal internal reflectors. The thickness of the unit reaches 15-20m in the deeper part of the lake. The lower seismic unit is a parallel-stratified unit with continuous internal reflections, slightly folded or inclined. We interpret Reflector "W" as the peri-lake land-surface during the last lake-level low stand, i.e. during the last glacial maximum. The lake has amassed on average 15-20m of sediments since the end of Wurm Glacial Period with a mean sedimentation rate of about lm/kyr. 210Pb geochronology applied on a sediment core recovered in front of the main water stream outflow yielded maximum sedimentation rate of 0.4cm/y for the time before 1956 and 0.6cm/y since 1956. The later is attributed to the dramatic man-induced lowering of the lake level by more than 30m between 1956-1990. Both the lakebed and the sediments below dip gently westwards, towards the SW-NE trending Vegoritis marginal fault. Slope failure phenomena occur in various stratigraphie levels along the fault-controlled western steep slope. The newly discovered E-W trending Ag Panteleimon fault divides Vegoritis fault into a northern active segment and a southern less effective one. On the seismic profiles the southern fault block subsides forming a 2m high morphological step on the lakebed, while the lake sediments are slightly folded. Further to the west Ag. Panteleimon fault separates Jurassic marbles to the north from Pleistocene conglomerates to the south and divides the NE-SW trending Petron-lake fault into two segments. We interpret Ag. Panteleimon fault as a dextral strike slip fault with minor normal component. In conclusion, strike slip movements have significantly influenced the formation and evolution of the Late Pliocene-Quaternary Vegoritis asymmetric graben and possibly of other basins in NW Greece. Despite the "suspicious" very low seismicity of the area, both normal and strike slip faults remain presently active with high seismic potential
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Schmelzbach, Cedric, Heinrich Horstmeyer, and Christopher Juhlin. "Shallow 3D seismic-reflection imaging of fracture zones in crystalline rock." GEOPHYSICS 72, no. 6 (2007): B149—B160. http://dx.doi.org/10.1190/1.2787336.
Full textAbstract:
A limited 3D seismic-reflection data set was used to map fracture zones in crystalline rock for a nuclear waste disposal site study. Seismic-reflection data simultaneously recorded along two roughly perpendicular profiles (1850 and [Formula: see text] long) and with a [Formula: see text] receiver array centered at the intersection of the lines sampled a [Formula: see text] area in three dimensions. High levels of source-generated noise required a processing sequence involving surface-consistent deconvolution, which effectively increased the strength of reflected signals, and a linear [Formula: see text] filtering scheme to suppress any remaining direct [Formula: see text]-wave energy. A flexible-binning scheme significantly balanced and increased the CMP fold, but the offset and azimuth distributions remain irregular; a wide azimuth range and offsets [Formula: see text] are concentrated in the center of the survey area although long offsets [Formula: see text] are only found at the edges of the site. Three-dimensional dip moveout and 3D poststack migration were necessary to image events with conflicting dips up to about 40°. Despite the irregular acquisition geometry and the high level of source-generated noise, we obtained images rich in structural detail. Seven continuous to semicontinuous reflection events were traced through the final data volume to a maximum depth of around [Formula: see text]. Previous 2D seismic-reflection studies and borehole data indicate that fracture zones are the most likely cause of the reflections.