Journal articles: 'Broadband Seismometers'

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Stähler, S. C., K. Sigloch, K. Hosseini, W. C. Crawford, G. Barruol, M. C. Schmidt-Aursch, M. Tsekhmistrenko, J. R. Scholz, A. Mazzullo, and M. Deen. "Performance report of the RHUM-RUM ocean bottom seismometer network around La Réunion, western Indian Ocean." Advances in Geosciences 41 (February 2, 2016): 43–63. http://dx.doi.org/10.5194/adgeo-41-43-2016.

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Abstract. RHUM-RUM is a German-French seismological experiment based on the sea floor surrounding the island of La Réunion, western Indian Ocean (Barruol and Sigloch, 2013). Its primary objective is to clarify the presence or absence of a mantle plume beneath the Reunion volcanic hotspot. RHUM-RUM's central component is a 13-month deployment (October 2012 to November 2013) of 57 broadband ocean bottom seismometers (OBS) and hydrophones over an area of 2000 × 2000 km2 surrounding the hotspot. The array contained 48 wideband OBS from the German DEPAS pool and 9 broadband OBS from the French INSU pool. It is the largest deployment of DEPAS and INSU OBS so far, and the first joint experiment. This article reviews network performance and data quality: of the 57 stations, 46 and 53 yielded good seismometer and hydrophone recordings, respectively. The 19 751 total deployment days yielded 18 735 days of hydrophone recordings and 15 941 days of seismometer recordings, which are 94 and 80 % of the theoretically possible yields. The INSU seismic sensors stand away from their OBS frames, whereas the DEPAS sensors are integrated into their frames. At long periods (> 10 s), the DEPAS seismometers are affected by significantly stronger noise than the INSU seismometers. On the horizontal components, this can be explained by tilting of the frame and buoy assemblage, e.g. through the action of ocean-bottom currents, but in addition the DEPAS intruments are affected by significant self-noise at long periods, including on the vertical channels. By comparison, the INSU instruments are much quieter at periods > 30 s and hence better suited for long-period signals studies. The trade-off of the instrument design is that the integrated DEPAS setup is easier to deploy and recover, especially when large numbers of stations are involved. Additionally, the wideband sensor has only half the power consumption of the broadband INSU seismometers. For the first time, this article publishes response information of the DEPAS instruments, which is necessary for any project where true ground displacement is of interest. The data will become publicly available at the end of 2017.

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Tape, Carl, Adam T. Ringler, and Don L. Hampton. "Recording the Aurora at Seismometers across Alaska." Seismological Research Letters 91, no. 6 (July 29, 2020): 3039–53. http://dx.doi.org/10.1785/0220200161.

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Abstract We examine three continuously recording data sets related to the aurora: all-sky camera images, three-component magnetometer data, and vertical-component, broadband seismic data as part of the EarthScope project (2014 to present). Across Alaska there are six all-sky cameras, 13 magnetometers, and >200 seismometers. The all-sky images and magnetometers have the same objective, which is to monitor space weather and improve our understanding of auroral activity, including the influence on magnetic fields in the ground. These variations in the magnetic field are also visible on seismometers, to the extent that during an auroral event, the long-period (40–800 s) waves recorded by a seismometer are magnetic field variations, not true ground motion. Although this is a problem—one that can be rectified with magnetic shielding at each seismometer site—it is also an opportunity because the present seismic array in Alaska is much broader than the coverage by magnetometers and all-sky cameras. Here we focus on three aurora events and document a direct link between aurora images in the night sky and seismometer recordings on ground. Simultaneous recordings by magnetometers provide a critical link between the sky images and the seismometer recordings. We document qualitative correlations among sky, magnetic, and seismic data. The findings suggest that the signature of auroral activity is widespread across seismometers in Alaska, implying that the seismic array could be used to enhance the spatial resolution of the existing network of all-sky cameras and magnetometers. Future efforts to improve the multisensor seismic stations in Alaska, for the purpose of monitoring seismic and auroral activity, should consider installation of all-sky cameras, installation of magnetometers, and magnetic shielding of seismic sensors.

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Marusiak, Angela G., Nicholas C. Schmerr, Daniella N. DellaGiustina, Brad Avenson, S. Hop Bailey, Veronica J. Bray, Juliette I. Brodbeck, et al. "The Deployment of the Seismometer to Investigate Ice and Ocean Structure (SIIOS) in Northwest Greenland: An Analog Experiment for Icy Ocean World Seismic Deployments." Seismological Research Letters 92, no. 3 (March 17, 2021): 2036–49. http://dx.doi.org/10.1785/0220200291.

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Abstract In anticipation of future spacecraft missions to icy ocean worlds, the Seismometer to Investigate Ice and Ocean Structure (SIIOS) was funded by National Aeronautics and Space Administration, to prepare for seismologic investigations of these worlds. During the summer of 2018, the SIIOS team deployed a seismic experiment on the Greenland ice sheet situated, approximately, 80 km north of Qaanaaq, Greenland. The seismometers deployed included one Trillium 120 s Posthole (TPH) broadband seismometer, 13 Silicon Audio flight-candidate seismometers, and five Sercel L28 4.5 Hz geophones. Seismometers were buried 1 m deep in the firn in a cross-shaped array centered on a collocated TPH and Silicon Audio instrument. One part of the array consisted of Silicon Audio and Sercel geophones situated 1 m from the center of the array in the ordinal directions. A second set of four Silicon Audio instruments was situated 1 km from the center of the array in the cardinal directions. A mock-lander spacecraft was placed at the array center and instrumented with four Silicon Audio seismometers. We performed an active-source experiment and a passive-listening experiment that lasted for, approximately, 12 days. The active–source experiment consisted of 9–12 sledgehammer strikes to an aluminum plate at 10 separate locations up to 100 m from the array center. The passive experiment recorded the ice-sheet ambient background noise, as well as local and regional events. Both datasets will be used to quantify differences in spacecraft instrumentation deployment strategies, and for evaluating science capabilities for single-station and small-aperture seismic arrays in future geophysical missions. Our initial results indicate that the flight-candidate seismometer performs comparably to the TPH at frequencies above 0.1 Hz and that instruments coupled to the mock-lander perform comparably to ground-based instrumentation in the frequency band of 0.1–10 Hz. For future icy ocean world missions, a deck-coupled seismometer would perform similarly to a ground-based deployment across the most frequency bands.

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Gerner, A., and G. Bokelmann. "Instrument self-noise and sensor misalignment." Advances in Geosciences 36 (September 17, 2013): 17–20. http://dx.doi.org/10.5194/adgeo-36-17-2013.

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Abstract. In this study we investigate self-noise of RefTekTM 151-60A "Observer" broadband seismometers (flat to velocity between 50 Hz down to T0=60 s, f0≈17 mHz) using the coherency analysis method introduced by Sleeman et al. (2006). We present a self-noise model for this type of sensor and compare it to the self-noise models of the standard observatory sensor STS-2 (Streckeisen) and RefTek's 151-120 broadband seismometer, which both have natural periods T0 of 120 s. We further report on the sensitivity of this technique to sensor misalignment and our success of eliminating leakage of the omnipresent microseism noise into self-noise estimates by numerically rotating seismic traces in order to find real self-noise.

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Vasilyev, I. M., Yu P. Kozhevnikov, S. A. Matsiyevskiy, V. G. Mezhberg, A. V. Rykov, and I. V. Ulomov. "The prospects for modernizing very broadband seismometers." Seismic Instruments 45, no. 1 (June 2009): 60–68. http://dx.doi.org/10.3103/s0747923909010101.

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YOSHIDA, Yasuhiro, Kenji KANJO, Satoshi HARADA, Kenji FUJIWARA, Toshiki OHTAKI, Akiko TANAKA, Satoshi KANESHIMA, et al. "Installation Experiment of Broadband Seismometers in Shallow Vaults." Zisin (Journal of the Seismological Society of Japan. 2nd ser.) 54, no. 1 (2001): 9–16. http://dx.doi.org/10.4294/zisin1948.54.1_9.

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Chen, Jui-Chun Freya, Wu-Cheng Chi, and Chu-Fang Yang. "Seismically Derived Ground Tilts Related to the 2010 Chilean Tsunami." Seismological Research Letters 92, no. 4 (March 24, 2021): 2172–81. http://dx.doi.org/10.1785/0220200288.

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Abstract Developing new ways to observe tsunami contributes to tsunami research. Tidal and deep-ocean gauges are typically used for coastal and offshore observations. Recently, tsunami-induced ground tilts offer a new possibility. The ground tilt signal accompanied by 2010 Mw 8.8 Chilean earthquake were observed at a tiltmeter network in Japan. However, tiltmeter stations are usually not as widely installed as broadband seismometers in other countries. Here, we studied broadband seismic records from Japan’s F-net and found ground tilt signals consistent with previously published tiltmeter dataset for this particular tsunamic event. Similar waveforms can also be found in broadband seismic networks in other countries, such as Taiwan, as well as an ocean-bottom seismometer. We documented a consistent time sequence of evolving back-azimuth directions of the tsunami waves at different stages of tsunami propagation through beamforming-frequency–wavenumber analysis and particle-motion analysis; the outcomes are consistent with the tsunami propagation model provided by the Pacific Tsunami Warning Center. These results shown that dense broadband seismic networks can provide a useful complementary dataset, in addition to tiltmeter arrays and other networks, to study or even monitor tsunami propagation using arrayed methods.

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Anglade, A., A. Lemarchand, J. M. Saurel, V. Clouard, M. P. Bouin, J. B. De Chabalier, S. Tait, et al. "Significant technical advances in broadband seismic stations in the Lesser Antilles." Advances in Geosciences 40 (April 10, 2015): 43–50. http://dx.doi.org/10.5194/adgeo-40-43-2015.

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Abstract. In the last few years, French West Indies observatories from the Institut de Physique du Globe de Paris (IPGP), in collaboration with The UWI Seismic Research Centre (SRC, University of West Indies), have modernized the Lesser Antilles Arc seismic and deformation monitoring network. 15 new, permanent stations have been installed that strengthen and expand its detection capabilities. The global network of the IPGP-SRC consortium is now composed of 20 modernized stations, all equipped with broadband seismometers, strong motion sensors, Global Positioning System (GPS) sensors and satellite communication for real-time data transfer. To enhance the sensitivity and reduce ambient noise, special efforts were made to improve the design of the seismic vault and the original Stuttgart shielding of the broadband seismometers (240 and 120s corner period). Tests were conducted for several months, involving different types of countermeasures, to achieve the highest performance level of the seismometers. GPS data, realtime and validated seismic data (only broadband) are now available from the IPGP data centre (http://centrededonnees.ipgp.fr/index.php?&lang=EN). This upgraded network feeds the Caribbean Tsunami Warning System supported by UNESCO and establishes a monitoring tool that produces high quality data for studying subduction and volcanic processes in the Lesser Antilles arc.

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Zecevic, Megan, Thomas S. Eyre, and David W. Eaton. "Static Ground Displacement for an Induced Earthquake Recorded on Broadband Seismometers." Bulletin of the Seismological Society of America 110, no. 5 (August 4, 2020): 2216–24. http://dx.doi.org/10.1785/0120200074.

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ABSTRACT Using geodetic methods, significant static ground deformation has been observed for many large natural earthquakes. Some of the largest earthquakes induced by hydraulic-fracturing operations have been observed in the Western Canada Sedimentary Basin; however, because of the size and depths of these events, the associated static ground deformations have not yet been observed using traditional geodetic techniques. A seismic processing technique, developed for small volcano-seismic events, has the potential to resolve micrometer-scale static displacements using broadband seismic data. In this study, we test this processing method using vertical component broadband recordings of an Mw 4.1 event acquired at four nearby broadband seismometers. Estimated static displacements at the four stations are compared with the theoretical surface displacement field for a dislocation on a finite rectangular source within a homogeneous, elastic half-space. The theoretical displacements have the same polarities as the measured displacements across the seismic network and have similar amplitudes for three of the four stations. However, one station yielded unstable results, which shows that care must be taken when using this method. These results suggest that this processing method has potential for obtaining surface deformation for small to moderate-sized earthquakes using broadband data.

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Haney, M. M., J. Power, M. West, and P. Michaels. "Causal Instrument Corrections for Short-Period and Broadband Seismometers." Seismological Research Letters 83, no. 5 (September 1, 2012): 834–45. http://dx.doi.org/10.1785/0220120031.

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Kozlovskaya, E., and A. Kozlovsky. "Influence of high-latitude geomagnetic pulsations on recordings of broadband force-balanced seismic sensors." Geoscientific Instrumentation, Methods and Data Systems 1, no. 2 (August 17, 2012): 85–101. http://dx.doi.org/10.5194/gi-1-85-2012.

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Abstract. Seismic broadband sensors with electromagnetic feedback are sensitive to variations of surrounding magnetic field, including variations of geomagnetic field. Usually, the influence of the geomagnetic field on recordings of such seismometers is ignored. It might be justified for seismic observations at middle and low latitudes. The problem is of high importance, however, for observations in Polar Regions (above 60° geomagnetic latitude), where magnitudes of natural magnetic disturbances may be two or even three orders larger. In our study we investigate the effect of ultra-low frequency (ULF) magnetic disturbances, known as geomagnetic pulsations, on the STS-2 seismic broadband sensors. The pulsations have their sources and, respectively, maximal amplitudes in the region of the auroral ovals, which surround the magnetic poles in both hemispheres at geomagnetic latitude (GMLAT) between 60° and 80°. To investigate sensitivity of the STS-2 seismometer to geomagnetic pulsations, we compared the recordings of permanent seismic stations in northern Finland to the data of the magnetometers of the IMAGE network located in the same area. Our results show that temporary variations of magnetic field with periods of 40–150 s corresponding to regular Pc4 and irregular Pi2 pulsations are seen very well in recordings of the STS-2 seismometers. Therefore, these pulsations may create a serious problem for interpretation of seismic observations in the vicinity of the auroral oval. Moreover, the shape of Pi2 magnetic disturbances and their periods resemble the waveforms of glacial seismic events reported originally by Ekström (2003). The problem may be treated, however, if combined analysis of recordings of co-located seismic and magnetic instruments is used.

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Forbriger, Thomas, Walter Zürn, and Rudolf Widmer-Schnidrig. "Challenges and Perspectives for Lowering the Vertical-Component Long-Period Detection Level." Seismological Research Letters 92, no. 4 (March 24, 2021): 2498–512. http://dx.doi.org/10.1785/0220200399.

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Abstract For observations of vertical-component acceleration in the normal-mode band (0.3–10 mHz), the detection sensitivity for signals from the Earth’s body can be improved to levels below the Peterson low-noise model (PLNM). This is achieved by deterministic procedures that (at least partly) remove the accelerations originating from atmospheric mass fluctuations. The physical models used in such corrections are still too simple and fail at frequencies above 3 mHz. Anticipating improved atmospheric correction procedures, we explore the prospects of lowering the detection level. From recordings of excellent vertical-component sensors operated under exceptional site conditions at the Black Forest Observatory, we select time windows of very low background signal, for which all of the contributing broadband seismometers showed their best performance. Streckeisen seismometers of type STS-1, STS-2, and STS-6A, a Nanometrics Trillium T360, and the superconducting gravimeter (SG) SG056 manufactured by GWR Instruments take part in this comparison. Because of their low level of self-noise, the STS-1 and the SG056-G1 benefit the most from a correction with the best currently available improved Bouguer plate model for atmospherically induced signals at frequencies below 1 mHz. As far as we know, this is the first case in which the background level of a broadband seismometer could be lowered below the PLNM. At signal periods beyond the normal-mode band (investigated up to 12 hr), the gravimeters show the lowest level of self-noise, directly followed by the STS-6A. In the band from 0.3 to 10 mHz, the STS-1 has the lowest level of self-noise, which is at least 4 dB below the PLNM, directly followed by the T360 and the STS-6A. Sensors of lower self-noise than the currently manufactured STS-6A or T360 are needed before improved atmospheric correction procedures lead to a significantly lower vertical-component detection threshold.

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Gerner, Andreas, Reinoud Sleeman, Wolfgang Lenhardt, and Bernhard Grasemann. "Improving Self‐Noise Estimates of Broadband Seismometers by 3D Trace Rotation." Seismological Research Letters 88, no. 1 (November 23, 2016): 96–103. http://dx.doi.org/10.1785/0220160137.

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Doody, C. D., A. T. Ringler, R. E. Anthony, D. C. Wilson, A. A. Holland, C. R. Hutt, and L. D. Sandoval. "Effects of Thermal Variability on Broadband Seismometers: Controlled Experiments, Observations, and Implications." Bulletin of the Seismological Society of America 108, no. 1 (December 26, 2017): 493–502. http://dx.doi.org/10.1785/0120170233.

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Dybing, Sydney N., Adam T. Ringler, David C. Wilson, and Robert E. Anthony. "Characteristics and Spatial Variability of Wind Noise on Near‐Surface Broadband Seismometers." Bulletin of the Seismological Society of America 109, no. 3 (March 19, 2019): 1082–98. http://dx.doi.org/10.1785/0120180227.

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Amundson, Jason M., John F. Clinton, Mark Fahnestock, Martin Truffer, Martin P. Lüthi, and Roman J. Motyka. "Observing calving-generated ocean waves with coastal broadband seismometers, Jakobshavn Isbræ, Greenland." Annals of Glaciology 53, no. 60 (2012): 79–84. http://dx.doi.org/10.3189/2012/aog60a200.

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AbstractWe use time-lapse photography, MODIS satellite imagery, ocean wave measurements and regional broadband seismic data to demonstrate that icebergs that calve from Jakobshavn Isbræ, Greenland, can generate ocean waves that are detectable over 150 km from their source. The waves, which are recorded seismically, have distinct spectral peaks, are not dispersive and persist for several hours. On the basis of these observations, we suggest that calving events at Jakobshavn Isbræ can stimulate seiches, or basin eigenmodes, in both Ilulissat Icefjord and Disko Bay. Our observations furthermore indicate that coastal, land-based seismometers located near calving termini (e.g. as part of the new Greenland Ice Sheet Monitoring Network (GLISN)) can aid investigations into the largely unexplored, oceanographic consequences of iceberg calving.

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Schweitzer, Johannes, Andreas Köhler, and Jon Magnus Christensen. "Development of the NORSAR Network over the Last 50 Yr." Seismological Research Letters 92, no. 3 (January 27, 2021): 1501–11. http://dx.doi.org/10.1785/0220200375.

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Abstract This contribution describes the development of Norwegian Seismic Array (NORSAR), from its origin 50 yr ago as a project for installing a single seismic array in southern Norway to a seismological research institute operating a network of six arrays and 14 three-component stations located in Norway and Antarctica. In addition, we document the different instrumentations from narrowband, mostly short-period sensors to today’s broadband seismometers that are installed at almost all sites.

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Melosantos, Arnaldo A., Karl Vincent C. Soriano, Ponzch Colleen M. Alcones, Jose U. Pantig, Jun D. Bonita, Ishmael C. Narag, Hiroyuki Kumagai, and Hiroshi Inoue. "Performance of Broadband Seismic Network of the Philippines." Journal of Disaster Research 10, no. 1 (February 1, 2015): 8–17. http://dx.doi.org/10.20965/jdr.2015.p0008.

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The Philippine Institute of Volcanology and Seismology implements a program on seismic and tsunami network development. It also plans to expand the Philippine seismic network (PSN), commission new stations, rehabilitate and improve existing stations, and repair and maintain the PSN. The PSN consists of 70 stations, 12 of which use broadband seismometers. Stations are strategically located to maximize the use of data from stations. The broadband seismic network is being developed to monitor earthquakes in and around the Philippines and to provide more accurate data for calculating earthquake parameters. Using data obtain from broadband records, the systemwill immediately calculate earthquake parameters useful for making decisions that provide highly accurate, timely warnings and information. PSN performance is evaluated in this study to ensure this. We consider background noise by analyzing station locations and conditions and their data contribution to SWIFT CMT solutions. We also use power spectral density (PSD) to compare station noise levels to global standards and study data gaps and their causes. Based on the above parameters and using a scale of poor-goodbest, the broadband seismic network is currently performing well.

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Kozlovskaya, E., and A. Kozlovsky. "Influence of high-latitude geomagnetic pulsations on recordings of broad-band force-balanced seismic sensors." Geoscientific Instrumentation, Methods and Data Systems Discussions 2, no. 1 (March 16, 2012): 107–48. http://dx.doi.org/10.5194/gid-2-107-2012.

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Abstract. Seismic broad-band sensors with electromagnetic feedback are sensitive to variations of surrounding magnetic field, including variations of geomagnetic field. Usually, the influence of the geomagnetic field on recordings of such seismometers is ignored. It might be justified for seismic observations at middle and low latitudes. The problem is of high importance, however, for observations in Polar Regions (above 60° geomagnetic latitude), where magnitudes of natural magnetic disturbances may be two or even three orders larger. In our study we investigate the effect of ultra-low frequency (ULF) magnetic disturbances, known as geomagnetic pulsations, on the STS-2 seismic broadband sensors. The pulsations have their sources and, respectively, maximal amplitudes in the region of the auroral ovals, which surround the magnetic poles in both hemispheres at geomagnetic latitude (MLAT) between 60° and 80°. To investigate sensitivity of the STS-2 seismometer to geomagnetic pulsations, we compared the recordings of permanent seismic stations in northern Finland to the data of the magnetometers of the IMAGE network located in the same area. Our results show that temporary variations of magnetic field with periods of 40–150 s corresponding to regular Pc4 and irregular Pi2 pulsations are seen very well in recordings of the STS-2 seismometers. Therefore, these pulsations may create a serious problem for interpretation of seismic observations in the vicinity of the auroral oval. Moreover, the shape of Pi2 magnetic disturbances and their periods resemble the waveforms of glacial seismic events reported originally by Ekström (2003). The problem may be treated, however, if combined analysis of recordings of collocated seismic and magnetic instruments is used.

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Barcheck, Grace, Geoffrey A. Abers, Aubreya N. Adams, Anne Bécel, John Collins, James B. Gaherty, Peter J. Haeussler, et al. "The Alaska Amphibious Community Seismic Experiment." Seismological Research Letters 91, no. 6 (August 19, 2020): 3054–63. http://dx.doi.org/10.1785/0220200189.

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Abstract The Alaska Amphibious Community Seismic Experiment (AACSE) is a shoreline-crossing passive- and active-source seismic experiment that took place from May 2018 through August 2019 along an ∼700 km long section of the Aleutian subduction zone spanning Kodiak Island and the Alaska Peninsula. The experiment featured 105 broadband seismometers; 30 were deployed onshore, and 75 were deployed offshore in Ocean Bottom Seismometer (OBS) packages. Additional strong-motion instruments were also deployed at six onshore seismic sites. Offshore OBS stretched from the outer rise across the trench to the shelf. OBSs in shallow water (<262 m depth) were deployed with a trawl-resistant shield, and deeper OBSs were unshielded. Additionally, a number of OBS-mounted strong-motion instruments, differential and absolute pressure gauges, hydrophones, and temperature and salinity sensors were deployed. OBSs were deployed on two cruises of the R/V Sikuliaq in May and July 2018 and retrieved on two cruises aboard the R/V Sikuliaq and R/V Langseth in August–September 2019. A complementary 398-instrument nodal seismometer array was deployed on Kodiak Island for four weeks in May–June 2019, and an active-source seismic survey on the R/V Langseth was arranged in June 2019 to shoot into the AACSE broadband network and the nodes. Additional underway data from cruises include seafloor bathymetry and sub-bottom profiles, with extra data collected near the rupture zone of the 2018 Mw 7.9 offshore-Kodiak earthquake. The AACSE network was deployed simultaneously with the EarthScope Transportable Array (TA) in Alaska, effectively densifying and extending the TA offshore in the region of the Alaska Peninsula. AACSE is a community experiment, and all data were made available publicly as soon as feasible in appropriate repositories.

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Shinohara, Masanao, Tetsuo Fukano, Toshihiko Kanazawa, Eiichiro Araki, Kiyoshi Suyehiro, Masashi Mochizuki, Kazuo Nakahigashi, Tomoaki Yamada, and Kimihiro Mochizuki. "Upper mantle and crustal seismic structure beneath the Northwestern Pacific Basin using a seafloor borehole broadband seismometer and ocean bottom seismometers." Physics of the Earth and Planetary Interiors 170, no. 1-2 (September 2008): 95–106. http://dx.doi.org/10.1016/j.pepi.2008.07.039.

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Aderhold, Kasey, Katherine E. Anderson, Angela M. Reusch, Mary C. Pfeifer, Richard C. Aster, and Tim Parker. "Data Quality of Collocated Portable Broadband Seismometers Using Direct Burial and Vault Emplacement." Bulletin of the Seismological Society of America 105, no. 5 (September 1, 2015): 2420–32. http://dx.doi.org/10.1785/0120140352.

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Lynner, Colton, Harm J. A. Van Avendonk, Anne Bécel, Gail L. Christeson, Brandon Dugan, James B. Gaherty, Steven Harder, et al. "The Eastern North American Margin Community Seismic Experiment: An Amphibious Active‐ and Passive‐Source Dataset." Seismological Research Letters 91, no. 1 (October 30, 2019): 533–40. http://dx.doi.org/10.1785/0220190142.

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Abstract The eastern North American margin community seismic experiment (ENAM‐CSE) was conceived to target the ENAM Geodynamic Processes at Rifting and Subducting Margins (GeoPRISMS) primary site with a suite of both active‐ and passive‐source seismic data that would shed light on the processes associated with rift initiation and evolution. To fully understand the ENAM, it was necessary to acquire a seismic dataset that was both amphibious, spanning the passive margin from the continental interior onto the oceanic portion of the North American plate, and multiresolution, enabling imaging of the sediments, crust, and mantle lithosphere. The ENAM‐CSE datasets were collected on‐ and offshore of North Carolina and Virginia over a series of cruises and land‐based deployments between April 2014 and June 2015. The passive‐source component of the ENAM‐CSE included 30 broadband ocean‐bottom seismometers (OBSs) and 3 onshore broadband instruments. The broadband stations were deployed contemporaneously with those of the easternmost EarthScope Transportable Array creating a trans‐margin amphibious seismic dataset. The active‐source portion of the ENAM‐CSE included several components: (1) two onshore wide‐angle seismic profiles where explosive shots were recorded on closely spaced geophones; (2) four major offshore wide‐angle seismic profiles acquired with an airgun source and short‐period OBSs (SPOBSs), two of which were extended onland by deployments of short‐period seismometers; (3) marine multichannel seismic (MCS) data acquired along the four lines of SPOBSs and a series of other profiles along and across the margin. During the cruises, magnetic, gravity, and bathymetric data were also collected along all MCS profiles. All of the ENAM‐CSE products were made publicly available shortly after acquisition, ensuring unfettered community access to this unique dataset.

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Alejandro, A. C. B., A. T. Ringler, D. C. Wilson, R. E. Anthony, and S. V. Moore. "Towards understanding relationships between atmospheric pressure variations and long-period horizontal seismic data: a case study." Geophysical Journal International 223, no. 1 (July 16, 2020): 676–91. http://dx.doi.org/10.1093/gji/ggaa340.

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SUMMARY Variations in atmospheric pressure have long been known to introduce noise in long-period (>10 s) seismic records. This noise can overwhelm signals of interest such as normal modes and surface waves. Generally, this noise is most pronounced on the horizontal components where it arises due to tilting of the seismometer in response to changes in atmospheric pressure. Several studies have suggested methodologies for correcting unwanted pressure-induced noise using collocated microbarograph records. However, how applicable these corrections are to varying geologic settings and installation types (e.g. vault versus post-hole) is unclear. Using coefficients obtained by solving for the residuals of these corrections, we can empirically determine the sensitivity of instruments in a specific location to the influences of pressure. To better understand how long-period, pressure-induced noise changes with time and emplacement, we examine horizontal seismic records along with barometric pressure at five different Global Seismographic Network stations, all with multiple broadband seismometers. We also analyse three Streckeisen STS-2 broadband seismometers, which are collocated with a microbarograph, at the Albuquerque Seismological Laboratory. We observe periods of high magnitude-squared-coherence (γ2-coherence; γ2 > 0.8) between the seismic and pressure signals which fluctuate through time, frequency, and even between seismic instruments in the same vault. These observations suggest that these tilt-generated signals are highly sensitive to very local (<10 m) site effects. However, we find that in cases where instruments are not located at a large depth (<100 m), the pressure-induced noise is polarized in a nearly constant direction that is consistent with local topographic features or the geometry of the vault. We also find that borehole instruments at a large depth (>100 m) appear to be unaffected by pressure-loading mechanisms outlined by Sorrells (1971) but possibly by Newtonian attraction. Correlating the induced-noise polarization direction with times of high coherence, we work to identify sensors that are ultimately limited by pressure-induced horizontal noise as well as period bands that can benefit from pressure corrections. We find that while the situation is complex, each sensor appears to have its own unique response to pressure. Our findings suggest that we can determine empirical relationships between pressure and induced tilt on a case by case basis.

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Ito, Aki, Hiroko Sugioka, and Eiichiro Araki. "An installation experiment with broadband ocean bottom seismometers for reducing low frequency seismic noises." JAMSTEC Report of Research and Development 2009 (2009): 131–39. http://dx.doi.org/10.5918/jamstecr.2009.131.

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Bashilov, I. P., S. G. Volosov, S. A. Korolyov, V. A. Merkulov, V. M. Ovtchinnikov, and O. V. Ovtchinnikova. "Comparative analysis of the characteristics of domestic and foreign broadband seismometers with capacitive transducers." Seismic Instruments 52, no. 3 (July 2016): 253–65. http://dx.doi.org/10.3103/s0747923916030026.

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Shen, Wenbin, Dijin Wang, and Cheinway Hwang. "Anomalous signals prior to Wenchuan earthquake detected by superconducting gravimeter and broadband seismometers records." Journal of Earth Science 22, no. 5 (September 30, 2011): 640–51. http://dx.doi.org/10.1007/s12583-011-0215-4.

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Li, Xiaojun, Dake Yang, Jianbo Xie, Jiemei Ma, Songyong Yuan, Weiwei Xu, Jianhe Zhao, and Dongsheng Li. "Applicability of the Welch method for examining self-noise level parameters for broadband seismometers." Geodesy and Geodynamics 6, no. 3 (May 2015): 233–39. http://dx.doi.org/10.1016/j.geog.2015.04.002.

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Bernauer, Felix, Kathrin Behnen, Joachim Wassermann, Sven Egdorf, Heiner Igel, Stefanie Donner, Klaus Stammler, et al. "Rotation, Strain, and Translation Sensors Performance Tests with Active Seismic Sources." Sensors 21, no. 1 (January 3, 2021): 264. http://dx.doi.org/10.3390/s21010264.

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Interest in measuring displacement gradients, such as rotation and strain, is growing in many areas of geophysical research. This results in an urgent demand for reliable and field-deployable instruments measuring these quantities. In order to further establish a high-quality standard for rotation and strain measurements in seismology, we organized a comparative sensor test experiment that took place in November 2019 at the Geophysical Observatory of the Ludwig-Maximilians University Munich in Fürstenfeldbruck, Germany. More than 24 different sensors, including three-component and single-component broadband rotational seismometers, six-component strong-motion sensors and Rotaphone systems, as well as the large ring laser gyroscopes ROMY and a Distributed Acoustic Sensing system, were involved in addition to 14 classical broadband seismometers and a 160 channel, 4.5 Hz geophone chain. The experiment consisted of two parts: during the first part, the sensors were co-located in a huddle test recording self-noise and signals from small, nearby explosions. In a second part, the sensors were distributed into the field in various array configurations recording seismic signals that were generated by small amounts of explosive and a Vibroseis truck. This paper presents details on the experimental setup and a first sensor performance comparison focusing on sensor self-noise, signal-to-noise ratios, and waveform similarities for the rotation rate sensors. Most of the sensors show a high level of coherency and waveform similarity within a narrow frequency range between 10 Hz and 20 Hz for recordings from a nearby explosion signal. Sensor as well as experiment design are critically accessed revealing the great need for reliable reference sensors.

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Xu, Weiwei, Songyong Yuan, Weitao Wang, Xinheng Luo, and Li Li. "Comparing Orientation Analysis Methods for a Shallow-Water Ocean-Bottom Seismometer Array in the Bohai Sea, China." Bulletin of the Seismological Society of America 110, no. 6 (September 22, 2020): 3174–84. http://dx.doi.org/10.1785/0120200174.

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ABSTRACT The horizontal orientation estimation of an ocean-bottom seismometer (OBS) is critical for providing reliable data for seismological studies. In this article, we applied three independent polarization analysis methods to estimate the absolute horizontal orientation of a pilot shallow-water OBS array in Bohai Sea, China. The OBS array was deployed in the autumn of 2018 and comprised 32 broadband seismometers lasting around 1 yr, aimed at investigating the geodynamics of North China craton and adjacent areas. The timings of the data were corrected through the correlation analysis of regional and teleseismic earthquake events, before the polarization analysis. Polarization analysis using P wave and Rayleigh wave, from both natural earthquakes and noise cross correlations, was performed. In total, 28 out of 29 stations obtained the effective estimates combining the three methods, of which 11 stations showed relatively robust results with variations well below 10° among the three methods. However, the superiority of one method over the others is not obvious. As there is a trade-off between the accepted final estimates and the number of qualified measurements defined by parameters such as the correlation coefficient threshold, window length, and filtering options, we investigated these effects using 15 different groups of parameters for the three methods, and the deviation statistics showed a distribution with the root mean square deviation of 9.2° for the whole array.

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Bonita, Jun D., Hiroyuki Kumagai, and Masaru Nakano. "Regional Moment Tensor Analysis in the Philippines: CMT Solutions in 2012–2013." Journal of Disaster Research 10, no. 1 (February 1, 2015): 18–24. http://dx.doi.org/10.20965/jdr.2015.p0018.

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Recently, the Philippine Institute of Volcanology and Seismology (PHIVOLCS) has upgraded its seismic network, equipping it with accelerometers and broadband seismometers for intensity and focal mechanism determinations. As part of this upgrade, PHIVOLCS adapted the use of a source analysis system called SWIFT to determine the centroid moment tensor (SWIFT CMT). SWIFT CMT solutions were estimated for medium to large size earthquakes (4.1 ≤Mw≤ 7.6) in the Philippines for the period of January 2012 to November 2013 and were statistically evaluated with respect to the CMT solutions of the Global Centroid Moment Tensor (GCMT) Project. The seismic moments, moment magnitudes, centroid locations, depths and focal mechanisms of most of the SWIFT CMT solutions are found to be consistent to those of the GCMT solutions for earthquakes withMw≥ 4.6. The SWIFT system with the new broadband seismographic network provides more CMT solutions for moderate size earthquakes (Mw≥ 4.1) than GCMT. SWIFT proves to be useful in the development of the Philippines CMT catalogue that will lead to a better understanding of seismotectonics in the Philippines.

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Tibuleac, I. M., D. H. von Seggern, J. G. Anderson, and J. N. Louie. "Computing Green's Functions from Ambient Noise Recorded by Accelerometers and Analog, Broadband, and Narrow-Band Seismometers." Seismological Research Letters 82, no. 5 (September 1, 2011): 661–75. http://dx.doi.org/10.1785/gssrl.82.5.661.

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Takanori Matsuzawa, Takumi Matsumoto, and Toshikazu Tanada. "Seismic inversion analysis of the 2014 and 2015 Kuchinoerabujima volcanic eruptions,using F-net broadband seismometers." Journal of Natural Disaster Science 37, no. 2 (2016): 91–103. http://dx.doi.org/10.2328/jnds.37.91.

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Kobayashi, Tomokazu, Takao Ohminato, Yoshiaki Ida, and Eisuke Fujita. "Intermittent inflations recorded by broadband seismometers prior to caldera formation at Miyake-jima volcano in 2000." Earth and Planetary Science Letters 357-358 (December 2012): 145–51. http://dx.doi.org/10.1016/j.epsl.2012.09.039.

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Rault, Claire, Wei-An Chao, Céline Gelis, Arnaud Burtin, Jui-Ming Chang, Odin Marc, Tz-Shin Lai, Yih-Min Wu, Niels Hovius, and Patrick Meunier. "Seismic Response of a Mountain Ridge Prone to Landsliding." Bulletin of the Seismological Society of America 110, no. 6 (July 21, 2020): 3004–20. http://dx.doi.org/10.1785/0120190127.

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ABSTRACT During an earthquake, site effects can play an important role in triggering landslides. To document the seismic response of steep hillslopes, we deployed broadband seismometers across a mountain ridge in Taiwan, in an area with a high earthquake-induced landslide hazard. The ridge has a simple, representative shape, and landslides have previously occurred there. Our seismometer array has recorded continuously during more than 1 yr, with both ambient-noise and regional moderate earthquakes as sources. Processing horizontal and vertical signal components, we show that the ridge has a complex response, which we attribute to the combined effects of the subsurface geology and the topographic geometry. Amplification and directionality of ground motion are observed both high and low on the ridge, giving rise to localized, elevated, earthquake-induced landslide hazard. Our database contains earthquakes with mostly similar locations, making it difficult to determine the effect of earthquake back azimuth on the ridge response. A part of the ridge response, possibly due to topographic effects, seems to be explained by a model derived from a frequency scale curvature proxy at low frequency. If correct, this would be a promising first step toward improving local ground-motion estimation in mountain areas. However, the definition of appropriate scaling parameters of site effects based on geophysical measurements, for use in regional and global landslide hazard equations applicable to mountain areas with substantial regolith thickness, remains a significant challenge.

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Xu, Weiwei, and Songyong Yuan. "A case study of seismograph self-noise test from Trillium 120QA seismometer and Reftek 130 data logger." Journal of Seismology 23, no. 6 (November 2019): 1347–55. http://dx.doi.org/10.1007/s10950-019-09872-9.

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Abstract Seismograph self-noise has become a de facto standard for instrument comparisons and their performance assessment and is considered as one of the most vital parameters for instrument comparison. For self-noise testing of modern force-balance feedback broadband seismometers, several factors have been thoroughly discussed and thought to be attributable to the self-noise estimate, including the data selection criteria, sensor alignment correction, timing error, correlation analysis method, and computational parameter selection during the computational process. This study focuses on some other factors, such as local site conditions, temperature insulating methods, and data logger self-noise interferences, with an aim to differentiate the self-noise contribution of these sources and their dependencies on time and frequency. A series of experiments were conducted at the Beijing National Earth Observatory using a Trillium 120QA seismometer and Reftek-130 data acquisition system at three different locations ranging from the ordinary equipment warehouse to global seismographic network level cave with a hard-rock base. Results show that noise-free site is necessary for the self-noise test in a frequency band greater than approximately 0.1 Hz. However, for a frequency band less than 0.1 Hz, the insulation method and installation procedures are far more important, although the influence of the site location cannot be neglected fully. A suitable preamp should be selected in the data logger configurations to ensure that the low-noise amplitude of the sensor signal is above the digitizer noise level.

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Freybourger, Marion, Jacques Hinderer, and Jeannot Trampert. "Comparative study of superconducting gravimeters and broadband seismometers STS-1 / Z in seismic and subseismic frequency bands." Physics of the Earth and Planetary Interiors 101, no. 3-4 (May 1997): 203–17. http://dx.doi.org/10.1016/s0031-9201(97)00003-4.

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Berenguer, Jean-Luc, Julien Balestra, Fabrice Jouffray, Fabrice Mourau, Françoise Courboulex, and Jean Virieux. "Celebrating 25 years of seismology at schools in France." Geoscience Communication 3, no. 2 (December 23, 2020): 475–81. http://dx.doi.org/10.5194/gc-3-475-2020.

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Abstract. An educational program focusing on seismological activities for school and university students that trains in observational sciences and raises citizen awareness of natural hazards has been active in France since 1995. Over this quarter century, different generations of students have learned various lessons concerning instrument installation, data recording, and analysis. These actions have led them into the field of scientific interrogation and interpretation, making them better prepared for our modern technological societies. We describe these student commitments that have been motivated by the installation of the first educational broadband seismometer in southern France. Analysis of regional earthquakes has generated a greater awareness of the seismic hazards where students live, while records of strong earthquakes all around the world have led to interaction between students, especially after the deployment of additional seismometers in schools. The natural extension of such an educational seismic network, first at the national level in France in 2006 and later in many countries through various collaborations, has enriched the pedagogical practices of teachers, increasing their skills in seismology and natural sciences among various other disciplines and complementing standard educational resources. We describe the necessary and sustainable relations between teachers and researchers over time. Combining students' motivation, teachers' experience and researchers' expertise has led to different hosting structures over the years. We conclude by presenting the feedback from a survey carried out in 2019 among all the teachers involved, highlighting the strong and weak points of such a long-term adventure. Recent integration into the official syllabus of the new Geosciences high school curricula in France illustrates the impact of such an exceptional experience.

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Marsan, David, Jérôme Weiss, Jean-Philippe Métaxian, Jacques Grangeon, Pierre-François Roux, and Jari Haapala. "Low-frequency bursts of horizontally polarized waves in the Arctic sea-ice cover." Journal of Glaciology 57, no. 202 (2011): 231–37. http://dx.doi.org/10.3189/002214311796405834.

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AbstractWe report the detection of bursts of low-frequency waves, typically f = 0.025 Hz, on horizontal channels of broadband seismometers deployed on the Arctic sea-ice cover during the DAMOCLES (Developing Arctic Modeling and Observing Capabilities for Long-term Environmental Studies) experiment in spring 2007. These bursts have amplitudes well above the ambient ice swell and a lower frequency content. Their typical duration is of the order of minutes. They occur at irregular times, with periods of relative quietness alternating with periods of strong activity. A significant correlation between the rate of burst occurrences and the ice-cover deformation at the ∼400 km scale centered on the seismic network suggests that these bursts are caused by remote, episodic deformation involving shearing across regional-scale leads. This observation opens the possibility of complementing satellite measurements of ice-cover deformation, by providing a much more precise temporal sampling, hence a better characterization of the processes involved during these deformation events.

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Chen, Chieh-Hung, Li-Ching Lin, Ta-Kang Yeh, Strong Wen, Huaizhong Yu, Chen Yu, Yongxin Gao, et al. "Determination of Epicenters before Earthquakes Utilizing Far Seismic and GNSS Data: Insights from Ground Vibrations." Remote Sensing 12, no. 19 (October 7, 2020): 3252. http://dx.doi.org/10.3390/rs12193252.

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Broadband seismometers, ground-based Global Navigation Satellite Systems (GNSS), and magnetometers that were located within an epicentral distance of approximately 150 km consistently observed the novel anomalous behaviors of the common-mode ground vibrations approximately 5–10 days before the M6.6 Meinong earthquake in Taiwan. The common-mode ground vibrations with amplitudes near 0.1 m at frequencies ranging from 8 × 10−5 to 2 × 10−4 Hz were generated near the region close to the epicenter of the impending earthquake. The common-mode vibrations were consistently observed in seismic and GNSS data associated with five other earthquakes in four distinct areas. The results reveal that the common-mode vibrations could be a typical behavior before earthquakes. The causal mechanism of common-mode vibrations can be attributed to crustal resonance excitations before fault dislocations occur. Potential relationships with other pre-earthquake anomalies suggest that the common-mode vibrations could be ground motion before earthquakes, which was investigated for a significant length of time.

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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 (October 2, 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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Smith, Nicholas R. A., Anya M. Reading, Michael W. Asten, and Charles W. Funk. "Constraining depth to basement for mineral exploration using microtremor: A demonstration study from remote inland Australia." GEOPHYSICS 78, no. 5 (September 1, 2013): B227—B242. http://dx.doi.org/10.1190/geo2012-0449.1.

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We constrain the depth and seismic structure of stiff sediment cover overlying a prospective basement terrane using a passive seismic technique which uses surface wave energy from microtremor (also known as ambient seismic energy or seismic noise). This may be applied to mineral exploration under cover to decrease the inherent ambiguity in modeling potential field data for exploration targeting. We use data from arrays of portable broadband seismometers, processed using both the multimode spatially averaged coherency (MMSPAC) method and the horizontal to vertical spectral ratio (HVSR) method, to produce profiles of seismic velocity structure along a 12-km transect. We have developed field protocols to ensure consistent acquisition of high-quality data in near-mine and remote locations and a variety of ground conditions. A wavefield approaching the theoretical ideal for MMSPAC processing is created by combining the energy content of an off-road vehicle, driven around the seismometer array, and ambient sources. We found that this combination results in significantly higher-quality MMSPAC waveforms in comparison with that obtained using ambient energy alone. Under ideal conditions, a theoretical maximum depth of investigation of 600 m can be achieved with a hexagonal sensor array with 50-m radius and MMSPAC and HVSR. The modeling procedure we employ is sensitive to layer thicknesses of [Formula: see text]. A high-velocity layer in the sediment package reduces the sensitivity to deeper structure. This can limit the modeling of underlying layers but may be addressed by detailed analysis of the HVSR peaks. Microtremor recordings including off-road vehicle noise, combined with the MMSPAC and HVSR processing techniques, may therefore be used to constrain sediment structure and depth to basement in a cost-effective and efficient method that could contribute greatly to future mineral exploration under cover.

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Power, John A., Mathew M. Haney, Stephen M. Botnick, James P. Dixon, David Fee, A. Max Kaufman, Dane M. Ketner, et al. "Goals and Development of the Alaska Volcano Observatory Seismic Network and Application to Forecasting and Detecting Volcanic Eruptions." Seismological Research Letters 91, no. 2A (January 2, 2020): 647–59. http://dx.doi.org/10.1785/0220190216.

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Abstract The Alaska Volcano Observatory (AVO) seismic network has been in operation since 1988 and during this time has grown from 29 to 217 seismic stations providing real-time monitoring of 32 active volcanoes in Alaska, as well as useful data for regional earthquake monitoring. Since 1988, AVO has detected 59 volcanic eruptions at Aleutian arc volcanoes, and 31 of these have been captured by local seismic instrumentation. As part of this monitoring effort, AVO has cataloged more than 120,000 earthquake hypocenters and magnitudes associated with volcanic processes throughout the arc. This high rate of volcanic activity provides an excellent opportunity to study seismicity associated with magmatic and eruptive processes and develop and refine analytical techniques to track volcanic seismicity and warn of hazardous eruptions. The network is currently undergoing an extensive upgrade, replacing aging short-period analog seismometers with digital broadband instruments. These are expected to improve AVO’s seismic capability and further facilitate other geophysical instrumentation such as continuous Global Positioning System receivers, infrasound sensors, and web cams.

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Lin, Guan-Wei, Ching Hung, Yi-Feng Chang Chien, Chung-Ray Chu, Che-Hsin Liu, Chih-Hsin Chang, and Hongey Chen. "Towards Automatic Landslide-Quake Identification Using a Random Forest Classifier." Applied Sciences 10, no. 11 (May 26, 2020): 3670. http://dx.doi.org/10.3390/app10113670.

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Landslide-generated seismic waves (landslide-quakes), exhibiting distinctive waveforms and frequency characteristics, can be recorded by nearby seismometers. Implementing an automatic classifier for landslide-quakes could help provide objective and accurate initiation times of landslides with efficiency. This study collected and analyzed the time information of 214 landslide seismic records due to 33 documented landslide events, from the Broadband Array in Taiwan for Seismology (BATS). In addition, equal numbers of earthquake and noise signals were also incorporated. The 642 seismic signals and time information were carefully examined using the random forest algorithm to create an automatic landslide-quake classifier. By validating the signal attributes of the landslide, earthquake, and noise events, specifically in the time and frequency domains, it was shown that the proposed classifier can reach an accuracy (the proportion of all correctly classified events to the total number of events) of 91.3%. To further evaluate the applicability of the automatic classifier, landslide-quakes generated during the devastating Typhoon Morakot (2009) and Typhoon Soudelor (2015) were also verified, showing that the sensitivity of the classifier is higher than 98%.

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Krawiec, Krzysztof, and Paulina Harba. "Comparison analysis of numerically calculated slip surfaces with measured S-wave velocity field for Just-Tęgoborze landslide in Carpathian flysch." E3S Web of Conferences 133 (2019): 01003. http://dx.doi.org/10.1051/e3sconf/201913301003.

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The article presents the comparison analysis between deformation field from numerical model and shear wave (S-wave) velocity field obtained from seismic interferometry (SI). Tests were conducted on active Just-Tęgoborze landslide. Geologically, the study area lies in Magura Nappe in the Outer Carpathians. The landslide’s flysch bedrock is covered by Quaternary colluvium built of clays and weathered clayey-rock deposits. During geotechnical investigation, properties of landslide body were established and failure surfaces were distinguished. In order to obtain S-wave velocity models, one-hour of ambient seismic noise was recorded by 12 broadband seismometers. As a result of data processing with SI method, Rayleigh surface wave propagation was reconstructed. The analysis of dispersion curves allowed to estimate a two dimensional S-wave velocity field. The deformation field were calculated assuming an elastic-plastic Coulomb-Mohr strength criterion. Images of shear strain increment, and values of factor of safety of the slope were obtained as a result of calculation. The comparison of the results indicates the similar characteristic features in the S-wave velocity field and the field of deformation calculated numerically.

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Walter, Fabian, Marco Olivieri, and John F. Clinton. "Calving event detection by observation of seiche effects on the Greenland fjords." Journal of Glaciology 59, no. 213 (2013): 162–78. http://dx.doi.org/10.3189/2013jog12j118.

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AbstractWith mass loss from the Greenland ice sheet accelerating and spreading to higher latitudes, the quantification of mass discharge in the form of icebergs has recently received much scientific attention. Here we make use of very low-frequency (0.001–0.01 Hz) seismic data from three permanent broadband stations installed in the summers of 2009–10 in northwest Greenland in order to monitor local calving activity. At these frequencies, calving seismograms are dominated by a tilt signal produced by local ground flexure in response to fjord seiching generated by major iceberg calving events. A simple triggering algorithm is proposed to detect calving events from large calving fronts with potentially no user interaction. Our calving catalogue identifies spatial and temporal differences in calving activity between Jakobshavn Isbræ and glaciers in the Uummannaq district ∼200 km to the north. The Uummannaq glaciers show clear seasonal fluctuations in seiche-based calving detections as well as seiche amplitudes. In contrast, the detections at Jakobshavn Isbræ show little seasonal variation, which may be evidence for an ongoing transition to winter calving activity. The results offer further evidence that seismometers can provide efficient and inexpensive monitoring of calving fronts.

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Karplus, Marianne S., Mohan Pant, Soma Nath Sapkota, John Nábělek, Aaron A. Velasco, Lok Bijaya Adhikari, Abhijit Ghosh, et al. "A Rapid Response Network to Record Aftershocks of the 2015 M 7.8 Gorkha Earthquake in Nepal." Seismological Research Letters 91, no. 4 (May 6, 2020): 2399–408. http://dx.doi.org/10.1785/0220190394.

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Abstract The Himalaya has experienced large damaging earthquakes over the past few centuries, most recently the damaging 25 April 2015 M 7.8 Gorkha earthquake in Nepal. Because of the continued earthquake risk presented by the continental collisional plate boundary at the Main Himalayan thrust and the high population densities in the region, collecting and processing data related to recent large earthquakes in this region is critically important for improving our understanding of the regional tectonics and earthquake hazard. Following the 2015 Gorkha earthquake, we deployed a National Science Foundation-funded rapid-response aftershock network known as the Nepal Array Measuring Aftershock Seismicity Trailing Earthquake network across the rupture area for 11 months beginning 7 weeks after the mainshock. The network consisted of 41 broadband and short-period seismometers, and 14 strong-motion sensors at 46 sites across eastern and central Nepal. The network spanned a region approximately 210 km along strike by 110 km across strike with a station spacing of 20–25 km. In this article, we report lessons learned from this deployment as well as details of the publicly accessible dataset including data recovery, data quality, and potential for future research.

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Weemstra, Cornelis, Lapo Boschi, Alexander Goertz, and Brad Artman. "Seismic attenuation from recordings of ambient noise." GEOPHYSICS 78, no. 1 (January 1, 2013): Q1—Q14. http://dx.doi.org/10.1190/geo2012-0132.1.

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We applied seismic interferometry to data from an ocean-bottom survey offshore Norway and found that ambient seismic noise can be used to constrain subsurface attenuation on a reservoir scale. By crosscorrelating only a few days of recordings by broadband ocean bottom seismometers, we were able to retrieve empirical Green’s functions associated with surface waves in the frequency range between 0.2 and 0.6 Hz and acoustic waves traveling through the sea water between 1.0 and 2.5 Hz. We discovered that the decay of these surface waves cannot be explained by geometrical spreading alone and required an additional loss of energy with distance. We quantified this observed attenuation in the frequency domain using a modified Bessel function to describe the cross-spectrum in a stationary field. We averaged cross-spectra of equally spaced station couples and sorted these azimuthally averaged cross-spectra with distance. We then obtained frequency-dependent estimates of attenuation by minimizing the misfit of the real parts to a damped Bessel function. The resulting quality factors as function of frequency are indicative of the depth variation of attenuation and correlated with the geology in the survey area.

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Holmgren, Joanna M., and Maximilian J. Werner. "Raspberry Shake Instruments Provide Initial Ground-Motion Assessment of the Induced Seismicity at the United Downs Deep Geothermal Power Project in Cornwall, United Kingdom." Seismic Record 1, no. 1 (April 1, 2021): 27–34. http://dx.doi.org/10.1785/0320210010.

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Abstract Raspberry Shake (RS) seismographs offer the potential for affordable and citizen-led seismic monitoring in areas with few publicly available seismometers, especially in previously quiescent regions experiencing induced seismicity. However, their scientific and regulatory potential remains largely untested. We examine the ground motions recorded by 11 RS and one broadband station within 15 km of the United Downs Deep Geothermal Power (UDDGP) project in Cornwall, United Kingdom, to evaluate the RS network’s suitability to provide an initial ground-motion assessment of the region. To date, the British Geological Survey (BGS) has reported 232 induced events originating at UDDGP since flow testing began in summer 2020, with two events exceeding local magnitude (ML) 1.5. Although the RS accelerometers are too noisy for UDDGP’s microseismic events, the vertical geophones are useful. Peak ground velocity observations are consistent with relevant ground-motion models, whereas peak ground acceleration (PGA) values are greater than predicted. Regional trends in the PGA levels are likely caused by path effects. Finally, RS estimates of ML are similar to those reported by the BGS. For sparse national seismic networks, RS stations can enable a preliminary evaluation of seismic events and their ground motions.

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Kohler, Monica D., Katrin Hafner, Jeffrey Park, Jessica C. E. Irving, Jackie Caplan-Auerbach, John Collins, Jonathan Berger, Anne M. Tréhu, Barbara Romanowicz, and Robert L. Woodward. "A Plan for a Long-Term, Automated, Broadband Seismic Monitoring Network on the Global Seafloor." Seismological Research Letters 91, no. 3 (April 15, 2020): 1343–55. http://dx.doi.org/10.1785/0220190123.

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Abstract Establishing an extensive and highly durable, long-term, seafloor network of autonomous broadband seismic stations to complement the land-based Global Seismographic Network has been a goal of seismologists for decades. Seismic signals, chiefly the vibrations from earthquakes but also signals generated by storms and other environmental processes, have been processed from land-based seismic stations to build intriguing but incomplete images of the Earth’s interior. Seismologists have mapped structures such as tectonic plates and other crustal remnants sinking deep into the mantle to obtain information on their chemical composition and physical state; but resolution of these structures from land stations is not globally uniform. Because the global surface is two-thirds ocean, increasing the number of seismic stations located in the oceans is critical for better resolution of the Earth’s interior and tectonic structures. A recommendation for a long-term seafloor seismic station pilot experiment is presented here. The overarching instrumentation goal of a pilot experiment is performance that will lead to the installation of a large number of long-term autonomous ocean-bottom seismic stations. The payoff of a network of stations separated from one another by a few hundred kilometers under the global oceans would be greatly refined resolution of the Earth’s interior at all depths. A second prime result would be enriched understanding of large-earthquake rupture processes in both oceanic and continental plates. The experiment would take advantage of newly available technologies such as robotic wave gliders that put an affordable autonomous prototype within reach. These technologies would allow data to be relayed to satellites from seismometers that are deployed on the seafloor with long-lasting, rechargeable batteries. Two regions are presented as promising arenas for such a prototype seafloor seismic station. One site is the central North Atlantic Ocean, and the other high-interest locale is the central South Pacific Ocean.

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Journal articles on the topic 'Broadband Seismometers'

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