Journal articles: 'Low velocity zone'

1

Thybo, Hans. "The heterogeneous upper mantle low velocity zone." Tectonophysics 416, no. 1-4 (April 2006): 53–79. http://dx.doi.org/10.1016/j.tecto.2005.11.021.

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Hirschmann, Marc M. "Partial melt in the oceanic low velocity zone." Physics of the Earth and Planetary Interiors 179, no. 1-2 (March 2010): 60–71. http://dx.doi.org/10.1016/j.pepi.2009.12.003.

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Thorne, Michael S., Edward J. Garnero, Gunnar Jahnke, Heiner Igel, and Allen K. McNamara. "Mega ultra low velocity zone and mantle flow." Earth and Planetary Science Letters 364 (February 2013): 59–67. http://dx.doi.org/10.1016/j.epsl.2012.12.034.

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4

Lin-Gun, Liu. "Water, low-velocity zone and the descending lithosphere." Tectonophysics 164, no. 1 (July 1989): 41–48. http://dx.doi.org/10.1016/0040-1951(89)90232-1.

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5

Liu, Yike, Xu Chang, Futian Liu, and Ye Zheng. "Three-dimensional velocity images beneath the KangDian Tethyan tectonic zone of China." Canadian Journal of Earth Sciences 39, no. 10 (October 1, 2002): 1517–25. http://dx.doi.org/10.1139/e02-053.

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Three-dimensional velocity images of the crust and upper mantle beneath the KangDian Tethyan tectonic zone in China are constructed using P-wave travel-time residuals of earthquakes. The KangDian Tethyan tectonic zone is a transitional zone in tectonic structures and an important topographic border line. It is also a zone of concentration of shallow-focus earthquakes. The imaging results indicate that there is a significant lateral heterogeneity in the crust and upper mantle beneath the KangDian Tethyan tectonic zone in China. The velocity images of the upper crust show features closely related to the tectonic features on the surface. A low-velocity layer exists in a very wide range of the mid-crust. Almost all of the major earthquakes took place in the transition strips between high- and low-velocity zones in the crust above 20 km depth. From the velocity images at 20+0 and 50+0 km depth, respectively, we find that the epicenters of strong earthquakes with magnitude larger than 6.0 are almost entirely distributed in the low-velocity zones or on their boundaries.

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Hazarika, Devajit, Koushik Sen, and Naresh Kumar. "Characterizing the intracrustal low velocity zone beneath northwest India–Asia collision zone." Geophysical Journal International 199, no. 3 (September 30, 2014): 1338–53. http://dx.doi.org/10.1093/gji/ggu328.

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7

Park, Jin-Oh, Gou Fujie, Lalith Wijerathne, Takane Hori, Shuichi Kodaira, Yoshio Fukao, Gregory F. Moore, Nathan L. Bangs, Shin'ichi Kuramoto, and Asahiko Taira. "A low-velocity zone with weak reflectivity along the Nankai subduction zone." Geology 38, no. 3 (March 2010): 283–86. http://dx.doi.org/10.1130/g30205.1.

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8

Jan van Heijst, Hendrik, Roel Snieder, and Robert Nowack. "Resolving a low-velocity zone with surface-wave data." Geophysical Journal International 118, no. 2 (August 1994): 333–43. http://dx.doi.org/10.1111/j.1365-246x.1994.tb03965.x.

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9

Hough, S. E., Y. Ben-Zion, and P. Leary. "Fault-zone waves observed at the southern Joshua Tree earthquake rupture zone." Bulletin of the Seismological Society of America 84, no. 3 (June 1, 1994): 761–67. http://dx.doi.org/10.1785/bssa0840030761.

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Abstract Waveform and spectral characteristics of several aftershocks of the M 6.1 22 April 1992 Joshua Tree earthquake recorded at stations just north of the Indio Hills in the Coachella Valley can be interpreted in terms of waves propagating within narrow, low-velocity, high-attenuation, vertical zones. Evidence for our interpretation consists of: (1) emergent P arrivals prior to and opposite in polarity to the impulsive direct phase; these arrivals can be modeled as headwaves indicative of a transfault velocity contrast; (2) spectral peaks in the S wave train that can be interpreted as internally reflected, low-velocity fault-zone wave energy; and (3) spatial selectivity of event-station pairs at which these data are observed, suggesting a long, narrow geologic structure. The observed waveforms are modeled using the analytical solution of Ben-Zion and Aki (1990) for a plane-parallel layered fault-zone structure. Synthetic waveform fits to the observed data indicate the presence of NS-trending vertical fault-zone layers characterized by a thickness of 50 to 100 m, a velocity decrease of 10 to 15% relative to the surrounding rock, and a P-wave quality factor in the range 25 to 50.

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Hunt, Martin, Shawn Clark, and Rob Tkach. "Velocity distributions near the inlet of corrugated steel pipe culverts." Canadian Journal of Civil Engineering 39, no. 12 (December 2012): 1243–51. http://dx.doi.org/10.1139/l2012-112.

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This paper presents the findings of a study examining the velocity field within the inlet region of a corrugated steel pipe (CSP) culvert model with vertical headwall, 45° wingwall, and projecting end inlet treatments. Also examined are the effects of embedding the culvert below the stream bed and backfilling the culvert with granular material. Three-dimensional velocity distributions were measured in an effort to better understand how these inlet treatments may affect fish passage. The study examined velocity structure within a CSP culvert with a diameter of 0.8 m at a flow rate of 0.175 m3/s. Measurements were recorded using acoustic Doppler velocimeters at four locations; 0.25, 0.5, 1, and 2 diameters downstream of the inlet. The velocity field of each inlet configuration was dominated by a central jet of high velocity flow surrounded by a low velocity recirculation zone. Analysis of the percent area less than Uavg for each inlet treatment found that the projecting end configuration contained the largest low velocity zone. The usefulness of the low velocity recirculation zone as a fish passage corridor may however be limited by the presence of significant vertical and spanwise velocities as well as high shear zones.

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KAWASAKI, Ichiro, Shun-ichiro KARATO, and Toru OUCHI. "Regional Variation and Origin of Upper Mantle Low Velocity Zone." Zisin (Journal of the Seismological Society of Japan. 2nd ser.) 42, no. 2 (1989): 239–54. http://dx.doi.org/10.4294/zisin1948.42.2_239.

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12

Presnall, Dean C., and Gudmundur H. Gudfinnsson. "Oceanic Volcanism from the Low-velocity Zone – without Mantle Plumes." Journal of Petrology 52, no. 7-8 (January 1, 2011): 1533–46. http://dx.doi.org/10.1093/petrology/egq093.

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13

Helffrich, George, and Geoffrey A. Abers. "Slab low-velocity layer in the eastern Aleutian subduction zone." Geophysical Journal International 130, no. 3 (September 1997): 640–48. http://dx.doi.org/10.1111/j.1365-246x.1997.tb01858.x.

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14

Gardés, Emmanuel, Mickael Laumonier, Malcolm Massuyeau, and Fabrice Gaillard. "Unravelling partial melt distribution in the oceanic low velocity zone." Earth and Planetary Science Letters 540 (June 2020): 116242. http://dx.doi.org/10.1016/j.epsl.2020.116242.

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15

Mashinskii, E. I. "Microplasticity effect in low-velocity zone induced by seismic wave." Journal of Applied Geophysics 83 (August 2012): 90–95. http://dx.doi.org/10.1016/j.jappgeo.2012.04.006.

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16

Long, Shu Chang, Ze Jin Li, Gang Kuang, Yan Bin He, and Xiao Hu Yao. "Research on Low Velocity Impact Damage of Laminated Composite." Applied Mechanics and Materials 513-517 (February 2014): 201–5. http://dx.doi.org/10.4028/www.scientific.net/amm.513-517.201.

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Damage caused by low-velocity-impact in laminated composite will significantly reduce the strength of the structure. A new numerical model is proposed for the research on the impact induced damage of laminated composite. Multiple forms of damage within and between layers are considered in this model. The cohesive contact technology is used to simulate the bonding properties between layers. The model can describe the information of delamination more accurately and efficiently. Then, a study is carried out to investigate the relationship of delamination and matrix cracking caused by low-velocity-impact. The result reveals that the area and axis of the delamination zone is affected by the direction of the matrix cracking zone.

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17

Liu, Zhen, Jeffrey Park, and Shun‐ichiro Karato. "Seismological detection of low‐velocity anomalies surrounding the mantle transition zone in Japan subduction zone." Geophysical Research Letters 43, no. 6 (March 16, 2016): 2480–87. http://dx.doi.org/10.1002/2015gl067097.

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18

Zheng, Yingcai, Francis Nimmo, and Thorne Lay. "Seismological implications of a lithospheric low seismic velocity zone in Mars." Physics of the Earth and Planetary Interiors 240 (March 2015): 132–41. http://dx.doi.org/10.1016/j.pepi.2014.10.004.

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19

Sifré, David, Emmanuel Gardés, Malcolm Massuyeau, Leila Hashim, Saswata Hier-Majumder, and Fabrice Gaillard. "Electrical conductivity during incipient melting in the oceanic low-velocity zone." Nature 509, no. 7498 (April 30, 2014): 81–85. http://dx.doi.org/10.1038/nature13245.

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20

Li, Y. G., and P. C. Leary. "Fault zone trapped seismic waves." Bulletin of the Seismological Society of America 80, no. 5 (October 1, 1990): 1245–71. http://dx.doi.org/10.1785/bssa0800051245.

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Abstract Two instances of fault zone trapped seismic waves have been observed. At an active normal fault in crystalline rock near Oroville in northern California, trapped waves were excited with a surface source and recorded at five near-fault borehole depths with an oriented three-component borehole seismic sonde. At Parkfield, California, a borehole seismometer at Middle Mountain recorded at least two instances of the fundamental and first higher mode seismic waves of the San Andreas fault zone. At Oroville recorded particle motions indicate the presence of both Love and Rayleigh normal modes. The Love-wave dispersion relation derived for an idealized wave guide with velocity structure determined by body-wave travel-time inversion yields seismograms of the fundamental mode that are consistent with the observed Love-wave amplitude and frequency. Applying a similar velocity model to the Parkfield observations, we obtain a good fit to the trapped wavefield amplitude, frequency, dispersion, and mode time separation for an asymmetric San Andreas fault zone structure—a high-velocity half-space to the southwest, a low-velocity fault zone, a transition zone containing the borehole seismometer, and an intermediate velocity half-space to the northeast. In the Parkfield borehole seismic data set, the locations (depth and offset normal to fault plane) of natural seismic events which do or do not excite trapped waves are roughly consistent with our model of the low velocity zone. We conclude that it is feasible to obtain near-surface borehole records of fault zone trapped waves. Because trapped modes are excited only by events close to the fault zone proper—thereby fixing these events in space relative to the fault—a wider investigation of possible trapped mode waveforms recorded by a borehole seismic network could lead to a much refined body-wave/tomographic velocity model of the fault and to a weighting of events as a function of offset from the fault plane. It is an open question whether near-surface sensors exist in a stable enough seismic environment to use trapped modes as an earth monitoring device.

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21

SATO, Hiroki. "Seismic Velocity at Mantle Solidus Temperature: Implications for the Thermal Structure of the Low Velocity Zone." Zisin (Journal of the Seismological Society of Japan. 2nd ser.) 48, no. 1 (1995): 131–37. http://dx.doi.org/10.4294/zisin1948.48.1_131.

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22

Aziz Zanjani, Farzaneh, Guoqing Lin, and Clifford H. Thurber. "Nested regional-global seismic tomography and precise earthquake relocation along the Hikurangi subduction zone, New Zealand." Geophysical Journal International 227, no. 3 (July 28, 2021): 1567–90. http://dx.doi.org/10.1093/gji/ggab294.

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SUMMARY Seismic and geodetic examinations of the Hikurangi subduction zone (HSZ) indicate a remarkably diverse and complex system. Here, we investigate the 3-D P-wave velocity structure of the HSZ by applying an iterative, nested regional-global tomographic algorithm. The new model reveals enhanced details of seismic variations along the HSZ. We also relocate over 57 000 earthquakes using this newly developed 3-D model and then further improve the relative locations for 75 per cent of the seismicity using waveform cross-correlation. Double seismic zone characteristics, including occurrence, depth distribution and thickness change along the strike of the HSZ. An aseismic but fast Vp zone separates the upper and lower planes of seismicity in the southern and northern North Island. The upper plane of seismicity correlates with low Vp zones below the slab interface, indicating fluid-rich channels formed on top and/or within a dehydrated crust. A broad low Vp zone is resolved in the lower part of the subducting slab that could indicate hydrous mineral breakdown in the slab mantle. In the northern North Island and southern North Island, the lower plane of seismicity mostly correlates with the top of these low Vp zones. The comparison between the thermal model and the lower plane of seismicity in the northern North Island supports dehydration in the lower part of the slab. The mantle wedge of the Taupo volcanic zone (TVZ) is characterized by a low velocity zone underlying the volcanic front (fluid-driven partial melting), a fast velocity anomaly in the forearc mantle (a stagnant cold nose) and an underlying low velocity zone within the slab (fluids from dehydration). These arc-related anomalies are the strongest beneath the central TVZ with known extensive volcanism. The shallow seismicity (<40 km depth) correlates with geological terranes in the overlying plate. The aseismic impermeable terranes, such as the Rakaia terrane, may affect the fluid transport at the plate interface and seismicity in the overlying plate, which is consistent with previous studies. The deep slow slip events (25–60 km depths) mapped in the Kaimanawa, Manawatu and Kapiti regions coincide with low Vp anomalies. These new insights on the structure along the HSZ highlight the change in the locus of seismicity and dehydration at depth that is governed by significant variations in spatial and probably temporal attributes of subduction zone processes.

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23

Li, Jun, Hui Li, Hui Chen, Jinrong Su, Yongsheng Liu, and Ping Tong. "Eikonal Equation-Based Seismic Tomography of the Source Areas of the 2008 Mw 7.9 Wenchuan Earthquake and the 2013 Mw 6.6 Lushan Earthquake." Bulletin of the Seismological Society of America 110, no. 2 (February 18, 2020): 886–97. http://dx.doi.org/10.1785/0120190134.

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ABSTRACT We use the eikonal equation-based seismic travel-time tomography method to image the source areas of the 2008 Wenchuan earthquake and the 2013 Lushan earthquake in the Longmenshan fault zone. High-resolution VP and VS models are obtained by inverting 75,686 P-wave and 74,552 S-wave travel times of local earthquakes during the period from 2009 to 2018. The tomographic models reveal strong crustal velocity heterogeneities in the study area. A significant velocity contrast exists across the Longmenshan fault zone: The western Songpan–Ganzi block is a high-velocity body, whereas the eastern Sichuan basin is a low-velocity anomaly. The hypocenter of the 2008 Wenchuan earthquake is between a high-velocity and a low-velocity anomaly. Beneath the Wenchuan mainshock, there is a significant low-velocity structure in the lower crust. The 2013 Lushan earthquake occurred in rocks associated with a high-velocity anomaly. A distinct low-velocity zone with low seismicity is imaged between the 2008 Wenchuan earthquake and the 2013 Lushan earthquake, where the crustal ductile deformation is likely to occur. The Baoxing complex to the northwest of the Lushan hypocenter exhibits as a high-velocity anomaly, which may be a carrier of stress accumulation and more prone to seismic activities in the future.

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Chen, Hao, Xiao Yan Tong, Xiang Zheng, and Lei Jiang Yao. "Acoustic Emission Analysis of Composite Laminates under Low Velocity Impact." Advanced Materials Research 118-120 (June 2010): 216–20. http://dx.doi.org/10.4028/www.scientific.net/amr.118-120.216.

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One of the problems preventing the industrial application of composites is the lack of an efficient method to detect and discriminate among types of damage occurring during service. To solve this problem, low velocity impact experiments are carried out on T300/QY8911 composite laminates. And synchronously, the acoustic emission (AE) technique and impact monitoring systems were used to record the AE signals and the impact force. The damage evolution, damage modes and acoustic emission (AE) activity were easily detected and evaluated by the analysis of both AE waveform and impact load. In this way, the damage development process containing matrix cracking, delamination and fibers breakage is investigated. The energy release of damage are theoretically approximated and correlated with the AE energy. By the theory, the “high energy damage zone” is defined in the scatter diagrams of amplitude-frequency. It is easily to prove that the primary damage mode of “high energy damage zone” is delamination.

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25

Vasco, Don W., John E. Peterson, and Ernest L. Majer. "A simultaneous inversion of seismic traveltimes and amplitudes for velocity and attenuation." GEOPHYSICS 61, no. 6 (November 1996): 1738–57. http://dx.doi.org/10.1190/1.1444091.

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It is possible to efficiently use traveltime and amplitude information to infer variations in velocity and Q. With little additional computation, terms accounting for source radiation pattern and receiver coupling may be included in the inversion. The methodology is based upon a perturbation approach to paraxial ray theory. The perturbation approach linearizes the relationship between velocity deviations and traveltime and amplitude anomalies. Using the technique, we infer the velocity and attenuation structure at a fractured granitic site near Raymond, California. A set of four well pairs are examined and each is found to contain two zones of strong attenuation. The velocity variations contain an upper low velocity region corresponding to the uppermost attenuating zone. The location of these zones agrees with independent well‐log and geophysical data. The velocity and attenuation anomalies appear to coincide with extensively fractured sections of the borehole and may indicate fracture zones rather than individual fractures.

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Mashinskii, E. I. "Effects of Intermittent Inelasticity when Propagating Seismic Wave in Low Velocity Zone." Mining science and technology 4, no. 1 (April 27, 2019): 31–41. http://dx.doi.org/10.17073/2500-0632-2019-1-31-41.

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The study of atypical manifestations of rock inelasticity improves understanding of the physical mechanisms of seismic wave propagation and attenuation in real environments. In the field experiments, the propagation of longitudinal wave at frequency of 240–1000 Hz between two shallow boreholes in low speed zone was investigated. The measurements were performed using a piezoelectric pulse emitter and similar receiver tools positioned in the boreholes. "Stress-time" σ(t) digital responses were recorded by the open channel with microsecond temporal resolution. The unusual short-period variations of amplitude in the form of sharp flattening wave front, stress drop, or plateau of different width (tens of microseconds) were detected in the wave profile. These low-amplitude variations in the waveform were regarded as manifestations of hopping intermittent inelasticity. This inelastic process was assumed to affect the waveform transformation. The contribution of hopping inelasticity depends on the applied stress magnitude, i.e. in this case, the seismic response amplitude. The mechanism of hopping inelasticity at small strains may be explained by microplasticity of rocks. The findings obtained represent a new step in understanding of physics of seismic and acoustic wave propagation in rocks and can be useful for handling of applied problems in geophysics and mining.

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Kim, N. W., and A. J. Seriff. "Marine PSSP reflections with a bottom velocity transition zone." GEOPHYSICS 57, no. 1 (January 1992): 161–70. http://dx.doi.org/10.1190/1.1443180.

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Marine shear‐wave reflection methods using the conventional data acquisition system (i.e., source and receiver in water) rely on two mode conversions at the water bottom to produce shear reflections such as PSSP. Some theoretical considerations and the results of a marine check shot survey conducted in the Gulf of Mexico demonstrate that the difficulty in observing PSSP events is attributable to weak P-S and S-P conversion at the bottom in regions with very low shear velocity (a few hundred ft/s or less) sediments at the bottom. For a simple water bottom with a low shear‐wave velocity, water over a uniform half space, the PS conversion factor is proportional to [Formula: see text] and the SP conversion factor is proportional to [Formula: see text], where [Formula: see text] is the bottom shear velocity. For [Formula: see text] their product gives PSSP reflections that can be comparable in amplitude to typical PPPP events. For [Formula: see text], the PSSP events should be about 30 dB weaker and probably not visible. For typical Gulf of Mexico sediments with a shear velocity transition zone several tens of feet thick at the bottom, the situation is even worse, since the velocities start near zero and may not reach 500 ft/s. This condition is common in many areas of recent sedimentations.

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Wang, Dong Sheng, Guang Qu, and Jin Lan Su. "Experimental Study on Dilution Ratio of Laser Cladding of Al₂O₃-13 % TiO₂ Ceramic Coating." Advanced Materials Research 978 (June 2014): 36–39. http://dx.doi.org/10.4028/www.scientific.net/amr.978.36.

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In this study, Al2O3–13 wt% TiO2ceramic coating was prepared on the substrate of a GH416 Ni-base superalloy by squash presetting laser cladding. The effects of processing parameters on dilution ratio were investigated. The result shows that the coating consists of two zones: the ceramic clad zone and dilution zone. The dilution ratio increases with the increase of laser power, whereas, the dilution ratio decreases with the increase of laser beam moving velocity. However, the coating with a low laser power is difficult to obtain metallurgical bonding to substrate, and with a high moving velocity can easily produce pores. The clad ceramic coatings characterized by a dense structure, no cracks, low dilution, and good metallurgical bonding to substrate were obtained under optimum processing parameters.

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Gosselin, Jeremy M., Pascal Audet, Clément Estève, Morgan McLellan, Stephen G. Mosher, and Andrew J. Schaeffer. "Seismic evidence for megathrust fault-valve behavior during episodic tremor and slip." Science Advances 6, no. 4 (January 2020): eaay5174. http://dx.doi.org/10.1126/sciadv.aay5174.

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Fault slip behavior during episodic tremor and slow slip (ETS) events, which occur at the deep extension of subduction zone megathrust faults, is believed to be related to cyclic fluid processes that necessitate fluctuations in pore-fluid pressures. In most subduction zones, a layer of anomalously low seismic wave velocities [low-velocity layer (LVL)] is observed in the vicinity of ETS and suggests high pore-fluid pressures that weaken the megathrust. Using repeated seismic scattering observations in the Cascadia subduction zone, we observe a change in the seismic velocity associated with the LVL after ETS events, which we interpret as a response to fluctuations in pore-fluid pressure. These results provide direct evidence of megathrust fault-valve processes during ETS.

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Jiang, Zhengrong, and Weijun Gao. "Impact of Enclosure Boundary Patterns and Lift-Up Design on Optimization of Summer Pedestrian Wind Environment in High-Density Residential Districts." Energies 14, no. 11 (May 30, 2021): 3199. http://dx.doi.org/10.3390/en14113199.

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A comfortable wind environment favors the sustainable development of urban residential districts and public health. However, the rapid growth of high-rise urban residential districts leads to low wind velocity environments in summer. This study examines the influence of enclosure boundary patterns and lift-up design on the wind environment and proposes an optimization strategy to improve the low wind velocity environment in residential districts in summer. A typical residential district in Hangzhou was selected; the average wind velocity, calm wind zone ratio and comfortable wind zone ratio were selected as the evaluation indexes. The wind environment for different enclosure boundary patterns and lift-up designs were obtained via computational fluid dynamics (CFD) simulations. The results indicate that the pedestrian wind environment is greatly improved in residential districts by reducing the height/width of the enclosure boundary, increasing the permeability rate and adopting a lift-up design in all buildings within residential districts. A combination of permeable railings and lift-up design is recommended; this can increase the average wind velocity and the ratio of comfortable wind zones by 70% and 200%, respectively. This study provides practical guidelines for the optimization of a low wind velocity environment in Chinese high-density residential districts in summer.

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Huang, Bor-Shouh, Ta-liang Teng, and Yeong Tein Yeh. "Numerical modeling of fault-zone trapped waves: Acoustic case." Bulletin of the Seismological Society of America 85, no. 6 (December 1, 1995): 1711–17. http://dx.doi.org/10.1785/bssa0850061711.

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Abstract We have obtained numerical results for an acoustic wave propagating in a 3D medium with mixed boundary conditions. The specific model involves a vertical low-velocity fault zone of varying thickness embedded in an otherwise homogeneous half-space. At the fault-zone boundary, the stress and displacement are continuous; on the free surface, the stress is zero. A pseudo-spectrum method is employed to achieve sufficient resolution with reasonable computation time on a CRAY. Results show the development of guided waves trapped in the fault zone. These guided waves display large amplitudes and lengthening waveforms; they propagate at lower velocity with amplitudes that drop off mainly due to energy leakage out of the fault zone. As the width of the fault zone varies, the wave energy tends to funnel into the new low-velocity wave guide. At large distance, these guided waves become the dominant arrivals on seismograms. The waveforms are useful to recover the geometry and properties of the fault zone.

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Wu, Yafei, and George A. McMechan. "Estimation of fracture height using microseismicity associated with hydraulic fracturing." GEOPHYSICS 63, no. 3 (May 1998): 908–17. http://dx.doi.org/10.1190/1.1444401.

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The ratio of horizontal‐to‐vertical (H/V) particle velocity in background microseismic radiation associated with hydraulic fracturing is substantially higher in the dilatant, low‐velocity fractured zone than it is outside. This provides a useful diagnostic for determining the height of the fractured zone. Numerical synthesis of guided wave phenomena within the low‐velocity fractured zone accounts for much of the observed behavior, but measured H/V patterns are not totally consistent with either pure tensile or pure shear sources. A composite model containing both tensile‐compressional sources and asperity shear failures appears to satisfy the main observations better than either source type does alone. This composite is consistent with current models of earthquake aftershock sequences, which also have different mechanisms at the edges and in the interior of a fracture zone (tensile and shear, respectively). The H/V phenomenon is consistent with a predominance of energy with shear‐wave polarization traveling at postcritical angles, produced either directly by the source or by P-to-S conversion at the edges of the fracture zone. The H/V ratios are enhanced by increasing dilatancy, which decreases the velocity within the fracture zone.

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Parra, Jorge O., Van Price, Carl Addington, Brian J. Zook, and Randolph J. Cumbest. "Interwell seismic imaging at the Savannah River Site, South Carolina." GEOPHYSICS 63, no. 6 (November 1998): 1858–65. http://dx.doi.org/10.1190/1.1444478.

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Crosswell and continuity logging seismic measurements were made beneath a large tank (27 m diameter) used for processing radioactive waste at the Department of Energy (DOE) Savannah River Site in the Atlantic Coastal Plain of South Carolina. We used the data to delineate a low‐velocity zone (soft materials) and image the connectivity of a clay unit between wells. The low‐velocity zone depicted on the crosswell seismic tomogram integrated with data from cores and well logs revealed soft materials in the region between 150 and 180 ft (46–55 m). The bottom boundary of this low‐velocity zone correlates with a reflection observed in the crosswell seismic image at a depth of 180 ft (55 m). This reflection corresponds to the impedance contrast between the soft materials and the more rigid Tinker Formation. The low‐velocity zone of soft materials indicates a dissolution margin of a carbonate unit (which is part of the Utley limestone) and the presence of loose sands of the Griffins Landing Member. Ray tracing and common source seismograms show that the rigid part of the Utley limestone extends horizontally about 12.5 ft (4 m) west of the receiver well. The continuity logging data showed leaky and normal modes in the region between 140 and 150 ft (43–46 m). The computed group velocity contours of leaky and normal modes are consistent with waveguide models based on well logs and crosswell seismic data. This indicates that the low‐velocity tan clay (confining unit) within the Griffins Landing Member is connected between wells.

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Tauzin, B., S. Kim, and B. L. N. Kennett. "Pervasive seismic low-velocity zones within stagnant plates in the mantle transition zone: Thermal or compositional origin?" Earth and Planetary Science Letters 477 (November 2017): 1–13. http://dx.doi.org/10.1016/j.epsl.2017.08.006.

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35

Benz, H. M., and J. McCarthy. "Evidence for an upper mantle low velocity zone beneath the southern Basin and Range-Colorado Plateau transition zone." Geophysical Research Letters 21, no. 7 (April 1, 1994): 509–12. http://dx.doi.org/10.1029/93gl01660.

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36

Hansen, Ralf T. J., Michael G. Bostock, and Nikolas I. Christensen. "Nature of the low velocity zone in Cascadia from receiver function waveform inversion." Earth and Planetary Science Letters 337-338 (July 2012): 25–38. http://dx.doi.org/10.1016/j.epsl.2012.05.031.

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37

Rubaiyn, Al, Awali Priyono, and Jamhir Safani. "Delineating a low velocity zone using joint inversion of rayleigh-wave dispersion curve." IOP Conference Series: Earth and Environmental Science 311 (August 14, 2019): 012077. http://dx.doi.org/10.1088/1755-1315/311/1/012077.

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Roberts, Peter M., Keiiti Aki, and Michael C. Fehler. "A low-velocity zone in the basement beneath the Valles Caldera, New Mexico." Journal of Geophysical Research: Solid Earth 96, B13 (December 10, 1991): 21583–96. http://dx.doi.org/10.1029/91jb02048.

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39

Sato, Hiroki, I. Selwyn Sacks, Tsutomu Murase, and Christopher M. Scarfe. "Thermal structure of the low velocity zone derived from laboratory and seismic investigations." Geophysical Research Letters 15, no. 11 (October 1988): 1227–30. http://dx.doi.org/10.1029/gl015i011p01227.

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40

Shen, Xuzhang, Xiaohui Yuan, and Xueqing Li. "A ubiquitous low-velocity layer at the base of the mantle transition zone." Geophysical Research Letters 41, no. 3 (February 11, 2014): 836–42. http://dx.doi.org/10.1002/2013gl058918.

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41

Tauzin, B., R. D. van der Hilst, G. Wittlinger, and Y. Ricard. "Multiple transition zone seismic discontinuities and low velocity layers below western United States." Journal of Geophysical Research: Solid Earth 118, no. 5 (May 2013): 2307–22. http://dx.doi.org/10.1002/jgrb.50182.

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42

Selway, Kate, and J. P. O'Donnell. "A small, unextractable melt fraction as the cause for the low velocity zone." Earth and Planetary Science Letters 517 (July 2019): 117–24. http://dx.doi.org/10.1016/j.epsl.2019.04.012.

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Wang, Na, Heng Bin Cui, and Xiao Yun Feng. "Direct Torque Control Methods of EMU during All Speed Range." Advanced Materials Research 462 (February 2012): 891–96. http://dx.doi.org/10.4028/www.scientific.net/amr.462.891.

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This paper theoretically analyzes the principle of the direct torque control method, then builds the direct torque control scheme of electric multiple-units(EMU) running during all speed range: indirect torque control in low velocity zone, eighteen polygon flux control method in moderate velocity zone and weakening hexagonal flux control strategy in high velocity zone. Simulation results show that the EMU direct torque control strategy in all speed range is feasible, and the system has good dynamic and static performance. All of the researches are available in the EMU controller research.

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44

Li, Haiou, Xiwei Xu, Wentao Ma, Ronghua Xie, Jingli Yuan, and Changpeng Xu. "Seismic Structure of Local Crustal Earthquakes beneath the Zipingpu Reservoir of Longmenshan Fault Zone." International Journal of Geophysics 2011 (2011): 1–6. http://dx.doi.org/10.1155/2011/407673.

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Three-dimensional P wave velocity models under the Zipingpu reservoir in Longmenshan fault zone are obtained with a resolution of 2 km in the horizontal direction and 1 km in depth. We used a total of 8589 P wave arrival times from 1014 local earthquakes recorded by both the Zipingpu reservoir network and temporary stations deployed in the area. The 3-D velocity images at shallow depth show the low-velocity regions have strong correlation with the surface trace of the Zipingpu reservoir. According to the extension of those low-velocity regions, the infiltration depth directly from the Zipingpu reservoir itself is limited to 3.5 km depth, while the infiltration depth downwards along the Beichuan-Yingxiu fault in the study area is about 5.5 km depth. Results show the low-velocity region in the east part of the study area is related to the Proterozoic sedimentary rocks. The Guanxian-Anxian fault is well delineated by obvious velocity contrast and may mark the border between the Tibetan Plateau in the west and the Sichuan basin in the east.

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Jornet-Monteverde, Julio Antonio, and Juan José Galiana-Merino. "Low-Cost Conversion of Single-Zone HVAC Systems to Multi-Zone Control Systems Using Low-Power Wireless Sensor Networks." Sensors 20, no. 13 (June 27, 2020): 3611. http://dx.doi.org/10.3390/s20133611.

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This paper presents a novel approach to convert a conventional house air conditioning installation into a more efficient system that individually controls the temperature of each zone of the house through Wi-Fi technology. Each zone regulates the air flow depending on the detected temperature, providing energy savings and increasing the machine performance. Therefore, the first step was to examine the communication bus of the air conditioner and obtain the different signal codes. Thus, an alternative Controller module has been designed and developed to control and manage the requests on the communication bus (Bus–Wi-Fi gateway). A specific circuit has been designed to adapt the signal of the serial port of the Controller with the communication bus. For the acquisition of the temperature and humidity data in each zone, a Node module has been developed, which communicates with the Controller through the Wi-Fi interface using the Message Queuing Telemetry Transport (MQTT) protocol with Secure Sockets Layer / Transport Layer Security (SSL/TLS) certificates. It has been equipped with an LCD touch screen as a human-machine interface. The Controller and the Node modules have been developed with the ultra-low power consumption CC3200 microController of Texas Instruments and the code has been implemented under the TI-RTOS real-time operating system. An additional module based on the Raspberry Pi computer has been designed to create the Wi-Fi network and implement the required network functionalities. The developed system not only ensures that the temperature in each zone is the desired one, but also controls the fan velocity of the indoor unit and the opening area of the vent registers, which considerably improves the efficiency of the system. Compared with the single-zone system, the experiments carried out show energy savings between 75% and 94% when only one of the zones is selected, and 44% when the whole house is air-conditioned, in addition to considerably improving user comfort.

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Afif, H., A. D. Nugraha, M. Muzli, S. Widiyantoro, Z. Zulfakriza, S. Wei, D. P. Sahara, et al. "Local earthquake tomography of the source region of the 2018 Lombok earthquake sequence, Indonesia." Geophysical Journal International 226, no. 3 (May 13, 2021): 1814–23. http://dx.doi.org/10.1093/gji/ggab189.

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SUMMARY We develop and present a 3-D seismic velocity model of the source region of the 2018 Lombok, Indonesia earthquakes by using local earthquake tomography. The data consist of 28 728 P- and 20 713 S-wave arrival times from 3259 events which were recorded by 20 local seismic stations. The results show that most of the significant earthquakes occur to the edge of high-velocity regions. We interpret these to represent coherent blocks of the Flores Oceanic Crust underthrusting Lombok. At depths shallower than the nucleation area of the largest earthquake, many triggered aftershocks are located within a low-velocity, high-Vp/Vs region which is probably a highly fractured fault zone with a large amount of fluid. This fault zone is parallel to the dip of the Flores Back Arc Thrust and probably ruptured during this earthquake sequence. A prominent low-velocity, high-Vp/Vs region is colocated with the northwest and southern flank of the Rinjani volcanic complex. This large aseismic region is probably related to a wide area of the crust containing fluids due to ongoing magma intrusion beneath the volcano. To the east of Rinjani Volcano a cooled intrusive complex was imaged. It is characterized by high-velocity and low-Vp/Vs, supported by the presence of a high Bouguer anomaly. We confirm the existence of the Sumbawa Strait Strike-Slip Fault and find it is characterized by an elongated low-velocity, high-Vp/Vs zone.

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Jia, Zhuo, and Gongbo Zhang. "Teleseismic Tomography for Imaging the Upper Mantle Beneath Northeast China." Applied Sciences 10, no. 13 (June 30, 2020): 4557. http://dx.doi.org/10.3390/app10134557.

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Tomographic imaging technology is a geophysical inversion method. According to the ray scanning, this method carries on the inversion calculation to the obtained information, and reconstructs the image of the parameter distribution rule of elastic wave and electromagnetic wave in the measured range, so as to delineate the structure of the geological body. In this paper, teleseismic tomography is applied by using seismic travel time data to constrain layered crustal structure where Fast Marching Methods (FMM) and the subspace method are considered as forward and inverse methods, respectively. Based on the travel time data picked up from seismic waveform data in the study region, the P-wave velocity structure beneath Northeast China down to 750 km is obtained. It can be seen that there are low-velocity anomalies penetrating the mantle transition zone under the Changbai volcano group, Jingpohu Volcano, and Arshan Volcano, and these low-velocity anomalies extend to the shallow part. In this paper, it is suggested that the Cenozoic volcanoes in Northeast China were heated by the heat source provided by the dehydration of the subducted Pacific plate and the upwelling of geothermal matter in the lower mantle. The low-velocity anomaly in the north Songliao basin does not penetrate the mantle transition zone, which may be related to mantle convection and basin delamination. According to the low-velocity anomalies widely distributed in the upper mantle and the low-velocity bodies passing through the mantle transition zone beneath the volcanoes, this study suggests that the Cenozoic volcanoes in Northeast China are kindred and have a common formation mechanism.

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Rodgers, Arthur, and Joydeep Bhattacharyya. "Upper Mantle Shear and Compressional Velocity Structure of the Central US Craton: Shear Wave Low-Velocity Zone and Anisotropy." Geophysical Research Letters 28, no. 2 (January 15, 2001): 383–86. http://dx.doi.org/10.1029/2000gl012112.

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Zhao, Weixin, Simo Kilpeläinen, Risto Kosonen, and Juha Jokisalo. "Experimental comparison of local low velocity unit combined with radiant panel and diffuse ceiling ventilation systems." Indoor and Built Environment 29, no. 6 (May 4, 2020): 895–914. http://dx.doi.org/10.1177/1420326x20918398.

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In this study, the performance of a micro-environment system was analysed and compared with diffused ceiling ventilation. In the analysed micro-environment low velocity radiant panel system, two low velocity units and radiant panels were installed above workstations to supply directly clean air to occupants and to cover the cooling power required. With diffused ceiling ventilation, all cooling demand is covered with air and thus, the airflow rate required is higher than with low velocity radiant panel system. The varied heat gain from 40 to 80 W/m2 consists of two seated dummies, laptops, monitors and simulated solar gain. The results show that with perimeter exhaust and local supply air, 8–13% reduction of the total cooling load required is possible, in comparison to the standard mixing systems. The average exhaust temperature was 0.7–1.9°C higher than average room air temperature at the workstation. Moreover, the mean air temperature with the low velocity radiant panel system at the occupied zone was 0.6°C lower than with diffused ceiling ventilation. With low velocity radiant panel system, the air velocity was less than 0.12 m/s in the occupied zone. Also, the draught rate was less than 10%. Furthermore, the air change efficiency with the low velocity radiant panel system was over 70% which is better than 44–49% efficiency with diffused ceiling ventilation.

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Zhang, X., F. Bianchi, and H. Liu. "Predicting low-velocity impact damage in composites by a quasi-static load model with cohesive interface elements." Aeronautical Journal 116, no. 1186 (December 2012): 1367–81. http://dx.doi.org/10.1017/s0001924000007685.

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AbstractA numerical model is developed for predicting low-velocity impact damage in laminated composites. Stacked shell elements are employed to model laminate plies with discrete interface elements in pre-determined zones to model the onset and propagation of matrix cracks and delamination. These interface elements are governed by a bi-linear cohesive failure law. Cohesive element zone size is determined by a separate finite element analysis using solid elements to identify the stress concentration sites. In order to save the computational effort, low-velocity impact load is modelled by quasi-static loading. Influence of contact force induced friction on shear driven mode II delamination is modelled by a friction model. For a clustered cross-ply laminate, calculated impact force and damage area are in good agreement with the test results. It is shown that matrix cracks should be included in the model in order to simulate delamination in adjacent interface. The practical outcome of this research is a validated modelling approach that can be further improved for predicting low-velocity impact damage in other stacking sequences.

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Journal articles on the topic 'Low velocity zone'

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