The Virtual Seismometer Method: Its Theory, History, and Promise
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Keck Combined Strong-Motion/Broadband Obs
KECK COMBINED STRONG-MOTION/BROADBAND OBS WHOI Ocean Bottom Seismograph Laboratory W.M. Keck Foundation Award to Understand Earthquake Predictability at East Pacific Rise Transform Faults. • In 2006, the W.M. Keck Foundation awarded funding to Jeff McGuire and John Collins to determine the physical mechanisms responsible for the observed capability to predict, using foreshocks, large (Mw ~6) transform-fault earthquakes at the East Pacific Rise, and to gain greater insight into the fundamentals of earthquake mechanics in general. • Achieving this objective required building 10 OBS of a new and unique type that could record, without saturation, the large ground motions generated by moderate to large earthquakes at distances of less than ~10 km. W.M. Keck OBS: Combined Broadband Seismometer and Strong-Motion Accelerometer • The broadband OBS available from OBSIP carry a broadband seismometer whose performance is optimized to resolve the earth’s background noise, which can be as small as 10-11 g r.m.s. in a bandwidth of width 1/6 decade at periods of about 100 s. Thus, these sensors are ideal for resolving ground motions from large distant earthquakes, necessary for structural seismology studies. • Ground motions from local, moderate to large earthquakes can generate accelerations of up a g or more, which would saturate or clip these sensors. Currently, there are no sensors (or data-loggers) that have a dynamic range to resolve this ~220 dB range of ground motion. • To overcome this limitation, we used Keck Foundation funding to build 10 OBS equipped with both a conventional broadband seismometer and a strong- motion accelerometer with a clip level of 2.5 g. -
Insights from the P Wave Travel Time Tomography in the Upper Mantle Beneath the Central Philippines
remote sensing Article Insights from the P Wave Travel Time Tomography in the Upper Mantle Beneath the Central Philippines Huiyan Shi 1 , Tonglin Li 1,*, Rui Sun 2, Gongbo Zhang 3, Rongzhe Zhang 1 and Xinze Kang 1 1 College of Geo-Exploration Science and Technology, Jilin University, No.938 Xi Min Zhu Street, Changchun 130026, China; [email protected] (H.S.); [email protected] (R.Z.); [email protected] (X.K.) 2 CNOOC Research Institute Co., Ltd., Beijing 100028, China; [email protected] 3 State Key Laboratory of Geodesy and Earth’s Dynamics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China; [email protected] * Correspondence: [email protected] Abstract: In this paper, we present a high resolution 3-D tomographic model of the upper mantle obtained from a large number of teleseismic travel time data from the ISC in the central Philippines. There are 2921 teleseismic events and 32,224 useful relative travel time residuals picked to compute the velocity structure in the upper mantle, which was recorded by 87 receivers and satisfied the requirements of teleseismic tomography. Crustal correction was conducted to these data before inversion. The fast-marching method (FMM) and a subspace method were adopted in the forward step and inversion step, respectively. The present tomographic model clearly images steeply subduct- ing high velocity anomalies along the Manila trench in the South China Sea (SCS), which reveals a gradual changing of the subduction angle and a gradual shallowing of the subduction depth from the north to the south. -
The East African Rift System in the Light of KRISP 90
ELSEVIER Tectonophysics 236 (1994) 465-483 The East African rift system in the light of KRISP 90 G.R. Keller a, C. Prodehl b, J. Mechie b,l, K. Fuchs b, M.A. Khan ‘, P.K.H. Maguire ‘, W.D. Mooney d, U. Achauer e, P.M. Davis f, R.P. Meyer g, L.W. Braile h, 1.0. Nyambok i, G.A. Thompson J a Department of Geological Sciences, University of Texas at El Paso, El Paso, TX 79968-0555, USA b Geophysikalisches Institut, Universitdt Karlwuhe, Hertzstrasse 16, D-76187Karlsruhe, Germany ’ Department of Geology, University of Leicester, University Road, Leicester LEl 7RH, UK d U.S. Geological Survey, Office of Earthquake Research, 345 Middlefield Road, Menlo Park, CA 94025, USA ’ Institut de Physique du Globe, Universite’ de Strasbourg, 5 Rue Ret& Descartes, F-67084 Strasbourg, France ‘Department of Earth and Space Sciences, University of California at Los Angeles, Los Angeles, CA 90024, USA ’ Department of Geology and Geophysics, University of Wuconsin at Madison, Madison, WI 53706, USA h Department of Earth and Atmospheric Sciences, Purdue University, West Lafayette, IN 47907, USA i Department of Geology, University of Nairobi, P.O. Box 14576, Nairobi, Kenya ’ Department of Geophysics, Stanford University, Stanford, CA 94305, USA Received 21 September 1992; accepted 8 November 1993 Abstract On the basis of a test experiment in 1985 (KRISP 85) an integrated seismic-refraction/ teleseismic survey (KRISP 90) was undertaken to study the deep structure beneath the Kenya rift down to depths of NO-150 km. This paper summarizes the highlights of KRISP 90 as reported in this volume and discusses their broad implications as well as the structure of the Kenya rift in the general framework of other continental rifts. -
Full-Text PDF (Final Published Version)
Pritchard, M. E., de Silva, S. L., Michelfelder, G., Zandt, G., McNutt, S. R., Gottsmann, J., West, M. E., Blundy, J., Christensen, D. H., Finnegan, N. J., Minaya, E., Sparks, R. S. J., Sunagua, M., Unsworth, M. J., Alvizuri, C., Comeau, M. J., del Potro, R., Díaz, D., Diez, M., ... Ward, K. M. (2018). Synthesis: PLUTONS: Investigating the relationship between pluton growth and volcanism in the Central Andes. Geosphere, 14(3), 954-982. https://doi.org/10.1130/GES01578.1 Publisher's PDF, also known as Version of record License (if available): CC BY-NC Link to published version (if available): 10.1130/GES01578.1 Link to publication record in Explore Bristol Research PDF-document This is the final published version of the article (version of record). It first appeared online via Geo Science World at https://doi.org/10.1130/GES01578.1 . Please refer to any applicable terms of use of the publisher. University of Bristol - Explore Bristol Research General rights This document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/red/research-policy/pure/user-guides/ebr-terms/ Research Paper THEMED ISSUE: PLUTONS: Investigating the Relationship between Pluton Growth and Volcanism in the Central Andes GEOSPHERE Synthesis: PLUTONS: Investigating the relationship between pluton growth and volcanism in the Central Andes GEOSPHERE; v. 14, no. 3 M.E. Pritchard1,2, S.L. de Silva3, G. Michelfelder4, G. Zandt5, S.R. McNutt6, J. Gottsmann2, M.E. West7, J. Blundy2, D.H. -
Earthquake Measurements
EARTHQUAKE MEASUREMENTS The vibrations produced by earthquakes are detected, recorded, and measured by instruments call seismographs1. The zig-zag line made by a seismograph, called a "seismogram," reflects the changing intensity of the vibrations by responding to the motion of the ground surface beneath the instrument. From the data expressed in seismograms, scientists can determine the time, the epicenter, the focal depth, and the type of faulting of an earthquake and can estimate how much energy was released. Seismograph/Seismometer Earthquake recording instrument, seismograph has a base that sets firmly in the ground, and a heavy weight that hangs free2. When an earthquake causes the ground to shake, the base of the seismograph shakes too, but the hanging weight does not. Instead the spring or string that it is hanging from absorbs all the movement. The difference in position between the shaking part of the seismograph and the motionless part is Seismograph what is recorded. Measuring Size of Earthquakes The size of an earthquake depends on the size of the fault and the amount of slip on the fault, but that’s not something scientists can simply measure with a measuring tape since faults are many kilometers deep beneath the earth’s surface. They use the seismogram recordings made on the seismographs at the surface of the earth to determine how large the earthquake was. A short wiggly line that doesn’t wiggle very much means a small earthquake, and a long wiggly line that wiggles a lot means a large earthquake2. The length of the wiggle depends on the size of the fault, and the size of the wiggle depends on the amount of slip. -
Geophysical Journal International
Geophysical Journal International Geophys. J. Int. (2017) 209, 1892–1905 doi: 10.1093/gji/ggx133 Advance Access publication 2017 April 1 GJI Seismology Surface wave imaging of the weakly extended Malawi Rift from ambient-noise and teleseismic Rayleigh waves from onshore and lake-bottom seismometers N.J. Accardo,1 J.B. Gaherty,1 D.J. Shillington,1 C.J. Ebinger,2 A.A. Nyblade,3 G.J. Mbogoni,4 P.R.N. Chindandali,5 R.W. Ferdinand,6 G.D. Mulibo,6 G. Kamihanda,4 D. Keir,7,8 C. Scholz,9 K. Selway,10 J.P. O’Donnell,11 G. Tepp,12 R. Gallacher,7 K. Mtelela,6 J. Salima5 and A. Mruma4 1Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964, USA. E-mail: [email protected] 2Department of Earth and Environmental Sciences, Tulane University, New Orleans, LA 70118,USA 3Department of Geosciences, The Pennsylvania State University, State College, PA 16802,USA 4Geological Survey of Tanzania, Dodoma, Tanzania 5Geological Survey Department of Malawi, Zomba, Malawi 6Department of Geology, University of Dar es Salaam, Dar es Salaam, Tanzania 7National Oceanography Centre Southampton, University of Southampton, Southampton S017 1BJ, United Kingdom 8Dipartimento di Scienzedella Terra, Universita degli Studi di Firenze, Florence 50121,Italy 9Department of Earth Sciences, Syracuse University, New York, NY 13210,USA 10Department of Earth and Planetary Sciences, Macquarie University, NSW 2109, Australia 11School of Earth and Environment, University of Leeds, Leeds, LS29JT, United Kingdom 12Alaska Volcano Observatory, U.S. Geological Survey, Anchorage, AK 99775,USA Accepted 2017 March 28. Received 2017 March 13; in original form 2016 October 12 SUMMARY Located at the southernmost sector of the Western Branch of the East African Rift System, the Malawi Rift exemplifies an active, magma-poor, weakly extended continental rift. -
Seismic Tomography Shows That Upwelling Beneath Iceland Is Confined to the Upper Mantle
Geophys. J. Int. (2001) 146, 504–530 Seismic tomography shows that upwelling beneath Iceland is confined to the upper mantle G. R. Foulger,1 M. J. Pritchard,1 B. R. Julian,2 J. R. Evans,2 R. M. Allen,3 G. Nolet,3 W. J. Morgan,3 B. H. Bergsson,4 P. Erlendsson,4 S. Jakobsdottir,4 S. Ragnarsson,4 R. Stefansson4 and K. Vogfjo¨rd5 1 Department of Geological Sciences, University of Durham, Durham, DH1 3LE, UK. E-mail: [email protected] 2 US Geological Survey, 345 Middlefield Road., Menlo Park, CA 94025, USA 3 Department of Geological and Geophysical Sciences, Guyot Hall, Princeton University, Princeton, NJ 08544–5807, USA 4 Meteorological Office of Iceland, Bustadavegi 9, Reykjavik, Iceland 5 National Energy Authority, Grensasvegi 9, Reykjavik, Iceland Accepted 2001 April 3. Received 2001 March 19; in original form 2000 August 1 SUMMARY We report the results of the highest-resolution teleseismic tomography study yet performed of the upper mantle beneath Iceland. The experiment used data gathered by the Iceland Hotspot Project, which operated a 35-station network of continuously recording, digital, broad-band seismometers over all of Iceland 1996–1998. The structure of the upper mantle was determined using the ACH damped least-squares method and involved 42 stations, 3159 P-wave, and 1338 S-wave arrival times, including the phases P, pP, sP, PP, SP, PcP, PKIKP, pPKIKP, S, sS, SS, SKS and Sdiff. Artefacts, both perceptual and parametric, were minimized by well-tested smoothing techniques involving layer thinning and offset-and-averaging. Resolution is good beneath most of Iceland from y60 km depth to a maximum of y450 km depth and beneath the Tjornes Fracture Zone and near-shore parts of the Reykjanes ridge. -
BY JOHNATHAN EVANS What Exactly Is an Earthquake?
Earthquakes BY JOHNATHAN EVANS What Exactly is an Earthquake? An Earthquake is what happens when two blocks of the earth are pushing against one another and then suddenly slip past each other. The surface where they slip past each other is called the fault or fault plane. The area below the earth’s surface where the earthquake starts is called the Hypocenter, and the area directly above it on the surface is called the “Epicenter”. What are aftershocks/foreshocks? Sometimes earthquakes have Foreshocks. Foreshocks are smaller earthquakes that happen in the same place as the larger earthquake that follows them. Scientists can not tell whether an earthquake is a foreshock until after the larger earthquake happens. The biggest, main earthquake is called the mainshock. The mainshocks always have aftershocks that follow the main earthquake. Aftershocks are smaller earthquakes that happen afterwards in the same location as the mainshock. Depending on the size of the mainshock, Aftershocks can keep happening for weeks, months, or even years after the mainshock happened. Why do earthquakes happen? Earthquakes happen because all the rocks that make up the earth are full of fractures. On some of the fractures that are known as faults, these rocks slip past each other when the crust rearranges itself in a process known as plate tectonics. But the problem is, rocks don’t slip past each other easily because they are stiff, rough and their under a lot of pressure from rocks around and above them. Because of that, rocks can pull at or push on each other on either side of a fault for long periods of time without moving much at all, which builds up a lot of stress in the rocks. -
Chapter 2 the Evolution of Seismic Monitoring Systems at the Hawaiian Volcano Observatory
Characteristics of Hawaiian Volcanoes Editors: Michael P. Poland, Taeko Jane Takahashi, and Claire M. Landowski U.S. Geological Survey Professional Paper 1801, 2014 Chapter 2 The Evolution of Seismic Monitoring Systems at the Hawaiian Volcano Observatory By Paul G. Okubo1, Jennifer S. Nakata1, and Robert Y. Koyanagi1 Abstract the Island of Hawai‘i. Over the past century, thousands of sci- entific reports and articles have been published in connection In the century since the Hawaiian Volcano Observatory with Hawaiian volcanism, and an extensive bibliography has (HVO) put its first seismographs into operation at the edge of accumulated, including numerous discussions of the history of Kīlauea Volcano’s summit caldera, seismic monitoring at HVO HVO and its seismic monitoring operations, as well as research (now administered by the U.S. Geological Survey [USGS]) has results. From among these references, we point to Klein and evolved considerably. The HVO seismic network extends across Koyanagi (1980), Apple (1987), Eaton (1996), and Klein and the entire Island of Hawai‘i and is complemented by stations Wright (2000) for details of the early growth of HVO’s seismic installed and operated by monitoring partners in both the USGS network. In particular, the work of Klein and Wright stands and the National Oceanic and Atmospheric Administration. The out because their compilation uses newspaper accounts and seismic data stream that is available to HVO for its monitoring other reports of the effects of historical earthquakes to extend of volcanic and seismic activity in Hawai‘i, therefore, is built Hawai‘i’s detailed seismic history to nearly a century before from hundreds of data channels from a diverse collection of instrumental monitoring began at HVO. -
Passive Seismic Interferometry in the Real World: Application with Microseismic and Traffic Noise
Passive seismic interferometry in the real world: Application with microseismic and traffic noise By Yang Zhao A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Engineering - Civil and Environmental Engineering in the Graduate Division of the University of California, Berkeley Committee in charge: Professor James W. Rector III, Chair Professor Steven D. Glaser Professor Doug Dreger Fall 2013 Passive seismic interferometry in the real world: Application with microseismic and traffic noise © 2013 by Yang Zhao Abstract Passive seismic interferometry in the real world: Application with microseismic and traffic noise by Yang Zhao Doctor of Philosophy in Civil and Environmental Engineering University of California, Berkeley Professor James Rector III, Chair The past decade witnessed rapid development of the theory of passive seismic interferometry followed by numerous applications of interferometric approaches in seismic exploration and exploitation. Developments conclusively demonstrates that a stack of cross- correlations of traces recorded by two receivers over sources appropriately distributed in three-dimensional heterogeneous earth can retrieve a signal that would be observed at one receiver if another acted as a source of seismic waves. The main objective of this dissertation was to review the mathematical proof of passive seismic interferometry, and to develop innovative applications using microseismicity induced by hydraulic fracturing and near-surface void characterization. We began this dissertation with the definitions and mathematical proof of Green’s function representation, together with the description of the physical mechanisms of passive seismic interferometry. Selected computational methods of passive seismic interferometry are also included. The first application was to extract body waves and perform anisotropy analysis from passive downhole microseismic noise acquired in hydrocarbon-bearing reservoirs. -
Ambient Seismic Noise Imaging of the Lowermost Mantle Beneath the North Atlantic Ocean Lise Retailleau, Pierre Boué, Lei Li, Michel Campillo
Ambient Seismic Noise Imaging of the Lowermost Mantle Beneath the North Atlantic Ocean Lise Retailleau, Pierre Boué, Lei Li, Michel Campillo To cite this version: Lise Retailleau, Pierre Boué, Lei Li, Michel Campillo. Ambient Seismic Noise Imaging of the Lower- most Mantle Beneath the North Atlantic Ocean. Geophysical Journal International, Oxford University Press (OUP), 2020, 222 (2), pp.1339-1351. 10.1093/gji/ggaa210. hal-02928287 HAL Id: hal-02928287 https://hal.univ-grenoble-alpes.fr/hal-02928287 Submitted on 2 Sep 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Ambient Seismic Noise Imaging of the Lowermost Mantle Beneath the North Atlantic Ocean Lise Retailleau1,2*, Pierre Boué3, Lei Li3 and Michel Campillo3 1 Department of Geophysics, Stanford University, Stanford, California, USA. 2 Now at Observatoire Volcanologique du Piton de la Fournaise, Institut de Physique du Globe de Paris, CNRS, UMR 7154-Sismologie, La Plaine des Cafres, La Réunion, France 3 Université Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, IRD, IFSTTAR, ISTerre, 38000 -
Crustal Structure of the Eastern Anatolia Region (Turkey) Based on Seismic Tomography
geosciences Article Crustal Structure of the Eastern Anatolia Region (Turkey) Based on Seismic Tomography Irina Medved 1,2,* , Gulten Polat 3 and Ivan Koulakov 1 1 Trofimuk Institute of Petroleum Geology and Geophysics SB RAS, Prospekt Koptyuga, 3, 630090 Novosibirsk, Russia; [email protected] 2 Sobolev Institute of Geology and Mineralogy SB RAS, Prospekt Koptyuga, 3, 630090 Novosibirsk, Russia 3 Department of Civil Engineering, Yeditepe University, 26 Agustos Yerleskesi, 34755 Istanbul, Turkey; [email protected] * Correspondence: [email protected]; Tel.: +7-952-922-49-67 Abstract: Here, we investigated the crustal structure beneath eastern Anatolia, an area of high seismicity and critical significance for earthquake hazards in Turkey. The study was based on the local tomography method using data from earthquakes that occurred in the study area provided by the Turkiye Cumhuriyeti Ministry of Interior Disaster and Emergency Management Directorate Earthquake Department Directorate of Turkey. The dataset used for tomography included the travel times of 54,713 P-waves and 38,863 S-waves from 6355 seismic events. The distributions of the resulting seismic velocities (Vp, Vs) down to a depth of 60 km demonstrate significant anomalies associated with the major geologic and tectonic features of the region. The Arabian plate was revealed as a high-velocity anomaly, and the low-velocity patterns north of the Bitlis suture are mostly associated with eastern Anatolia. The upper crust of eastern Anatolia was associated with a ~10 km thick high-velocity anomaly; the lower crust is revealed as a wedge-shaped low-velocity anomaly. This kind of seismic structure under eastern Anatolia corresponded to the hypothesized existence of Citation: Medved, I.; Polat, G.; a lithospheric window beneath this collision zone, through which hot material of the asthenosphere Koulakov, I.