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Sample records for active seismic area

  1. Seismic activity of Tokyo area and Philippine Sea plate under Japanese Islands

    NASA Astrophysics Data System (ADS)

    Sakai, S.; Nakagawa, S.; Nanjo, K.; Kasahara, K.; Panayotopoulos, Y.; Tsuruoka, H.; Kurashimo, E.; Obara, K.; Hirata, N.; Kimura, H.; Honda, R.

    2012-12-01

    The Japanese government has estimated the probability of earthquake occurrence with magnitude 7-class during the next 30 years as 70 %. This estimation is based on five earthquakes that occurred in this area in the late 120 years. However, it has been revealed that this region is lying on more complicated tectonic condition due to the two subducted plates and the various types of earthquakes which have been caused by. Therefore, it is necessary to classify these earthquakes into inter-plate earthquakes and intra-plate ones. Then, we have been constructing a seismic observation network since 5 years ago. Tokyo Metropolitan area is a densely populated region of about 40 million people. It is the center of Japan both in politics and in economy. So that human activities have been conducting quite busily, this region is unsuitable for seismic observation. Then, we have decided to make an ultra high dense seismic observation network. We named it the Metropolitan Seismometer Observation Network; MeSO-net. MeSO-net consists of 296 seismic stations. Minimum interval is about 2km and average interval is about 5km.We picked the P- and S-wave arrival times manually. We applied double-difference tomography method to the dataset and estimated the velocity structure. We depicted the plate boundaries from the newly developed velocity model. And, we referred to the locations of the repeating earthquakes, the distributions of normal hypocenters and the focal mechanisms. Our plate model became relatively flat and a little shallower than previous one.Seismicity of Metropolitan area after the M9 event was compared to the one before M9 event. The seismic activity is about 4 times as high as before the M9 event occurred. We examined spatial distribution of the activated seismicity with respect to the newly developed plate configuration. The activated events are located on upper boundaries and they have almost thrust type mechanisms. Recently, a slow slip event has occurred on October in

  2. Geomorphic evidence of active faults growth in the Norcia seismic area (central Apennines, Italy)

    NASA Astrophysics Data System (ADS)

    Materazzi, Marco; Aringoli, Domenico; Farabollini, Piero; Giacopetti, Marco; Pambianchi, Gilberto; Tondi, Emanuele; Troiani, Francesco

    2016-04-01

    Fault-growth by segment linkage is one of the fundamental processes controlling the evolution, in both time and the space, of fault systems. In fact, step-like trajectories shown by length-displacement diagrams for individual fault arrays suggest that the development of evolved structures result by the linkage of single fault segments. The type of interaction between faults and the rate at which faults reactivate not only control the long term tectonic evolution of an area, but also influence the seismic hazard, as earthquake recurrence intervals tend to decrease as fault slip rate increase. The use of Geomorphological investigations represents an important tool to constrain the latest history of active faults. In this case, attention has to be given to recognize morphostructural, historical, environmental features at the surface, since they record the long-term seismic behavior due to the fault growth processes (Tondi and Cello, 2003). The aim of this work is to investigate the long term morphotectonic evolution of a well know seismic area in the central Apennines: the Norcia intramontane basin (Aringoli et al., 2005). The activity of the Norcia seismic area is characterized by moderate events and by strong earthquakes with maximum intensities of X-XI degrees MCS and equivalent magnitudes around 6.5±7.0 (CPTI, 2004). Based on the morphostructural features as well as on the historical seismicity of the area, we may divide the Norcia seismic area into three minor basins roughly NW-SE oriented: the Preci sub-basin in the north; the S. Scolastica and the Castel S. Maria sub-basins in the south. The wider basin (S. Scolastica) is separated from the other two by ridges transversally oriented with respect the basins themselves; they are the geomorphological response to the tectonic deformation which characterizes the whole area. Other geomorphological evidences of tectonic activity are represented by deformation of old summit erosional surfaces, hydrographic network

  3. Geology of the area of induced seismic activity at Monticello Reservoir, South Carolina

    SciTech Connect

    Secor, D.T. Jr.; Smith, W.A.; Snoke, A.W.; Peck, L.S.; Pitcher, D.M.; Prowell, D.C.; Simpson, D.H.

    1982-08-10

    This study provides geological background information necessary for an evaluation of the earthquake hazard in an area of induced seismic activity at Monticello Reservoir, South Carolina. This region contains a thick stratified sequence of Proterozoic Z and Cambrian metasedimentary and metavolcanic rocks. In the early to middle Paleozoic, this sequence was recrystallized and deformed under metamorphic conditions that ranged from greenschist to amphibolite facies and experienced at least two episodes of folding. The region has been intruded by late kinematic to postkinematic granitoid plutons of Silurian and Carboniferous ages and by numerous northwest trending diabase diks of Late Traissic and Early Jurassic age. The region south of Monticello Reservoir in the Carolina slate belt experienced two episodes of faulting in the late Paleozoic and/or early to middle Mesozoic. The older group of faults trends approximately east, has only small displacements, and is characterized by extensive silicifiction of the fault zones. The younger group of faults trends approximately north has experienced dip slip displacements up to 1700 m and is characterized by carbonate mineralization in the fault zones. Both sets of faults are cut by an undeformed diabase dike of Late Triassic or Early Jurassic age. The induced seismic activity around Monticello Reservoir is occurring in a heterogeneous quartz monzonite pluton of Carboniferous age. The pluton contains large enclaves of country rock and is cut by numerous, diversely oriented small faults and joint. These local inhomogeneities in the pluton together with an irregular stress field are interpreted to control the diffuse seismic activity around the reservoir. In view of the apparent absence of lengthy faults it is unlikely that a large-magnitude earthquake will occur in response to the stress and pore pressure changes related to the impoundment of Monticello Reservoir.

  4. Ionospheric plasma deterioration in the area of enhanced seismic activity as compared to antipodal sites far from seismicity

    NASA Astrophysics Data System (ADS)

    Gulyaeva, Tamara; Arikan, Feza; Poustovalova, Ljubov; Stanislawska, Iwona

    2016-07-01

    The early magnetogram records from two nearly antipodal sites at Greenwich and Melbourne corresponding to the activity level at the invariant magnetic latitude of 50 deg give a long series of geomagnetic aa indices since 1868. The aa index derived from magnetic perturbation values at only two observatories (as distinct from the planetary ap index) experiences larger extreme values if either input site is well situated to the overhead ionospheric and/or field aligned current systems producing the magnetic storm effects. Analysis of the earthquakes catalogues since 1914 has shown the area of the peak global earthquake occurrence in the Pacific Ocean southwards from the magnetic equator, and, in particular, at Australia. In the present study the ionospheric critical frequency, foF2, is analyzed from the ionosonde measurements at the nearby observatories, Canberra and Slough (Chilton), and Moscow (control site) since 1944 to 2015. The daily-hourly-annual percentage occurrence of positive ionospheric W index (pW+) and negative index (pW-) is determined. It is found that the ionospheric plasma depletion pW- of the instant foF2 as compared to the monthly median is well correlated to the aa index at all three sites but the positive storm signatures show drastic difference at Canberra (no correlation of pW+ with aa index) as compared to two other sites where the high correlation is found of the ionospheric plasma density enhancement with the geomagnetic activity. A possible suppression of the enhanced ionospheric variability over the region of intense seismicity is discussed in the paper. This study is supported by TUBITAK EEEAG 115E915.

  5. High-resolution seismic structure analysis of an active submarine mud volcano area off SW Taiwan

    NASA Astrophysics Data System (ADS)

    Lin, Hsiao-Shan; Hsu, Shu-Kun; Tsai, Wan-Lin; Tsai, Ching-Hui; Lin, Shin-Yi; Chen, Song-Chuen

    2015-04-01

    In order to better understand the subsurface structure related to an active mud volcano MV1 and to understand their relationship with gas hydrate/cold seep formation, we conducted deep-towed side-scan sonar (SSS), sub-bottom profiler (SBP), multibeam echo sounding (MBES), and multi-channel reflection seismic (MCS) surveys off SW Taiwan from 2009 to 2011. As shown in the high-resolution sub-bottom profiler and EK500 sonar data, the detailed structures reveal more gas seeps and gas flares in the study area. In addition, the survey profiles show several submarine landslides occurred near the thrust faults. Based on the MCS results, we can find that the MV1 is located on top of a mud diapiric structure. It indicates that the MV1 has the same source as the associated mud diapir. The blanking of the seismic signal may indicate the conduit for the upward migration of the gas (methane or CO2). Therefore, we suggest that the submarine mud volcano could be due to a deep source of mud compressed by the tectonic convergence. Fluids and argillaceous materials have thus migrated upward along structural faults and reach the seafloor. The gas-charged sediments or gas seeps in sediments thus make the seafloor instable and may trigger submarine landslides.

  6. Active Seismic Imaging Experiment

    NASA Astrophysics Data System (ADS)

    Berge, Patricia A.; Dawson, Phillip B.; Evans, John R.

    In September 1985 the U.S. Geological Survey (USGS) and Lawrence Livermore National Laboratory (LLNL) will conduct an active seismic experiment in the Medicine Lake area of northern California. The work is supported by the Geothermal Research Program of USGS and by the Geothermal and Hydropower Technologies Division of the U.S. Department of Energy. We invite interested organizations or individuals to record our explosions from Medicine Lake volcano and surrounding areas not covered by the USGS-LLNL array.

  7. A robust satellite technique for monitoring seismically active areas: The case of Bhuj Gujarat earthquake

    NASA Astrophysics Data System (ADS)

    Genzano, N.; Aliano, C.; Filizzola, C.; Pergola, N.; Tramutoli, V.

    2007-02-01

    A robust satellite data analysis technique (RAT) has been recently proposed as a suitable tool for satellite TIR surveys in seismically active regions and already successfully tested in different cases of earthquakes (both high and medium-low magnitudes). In this paper, the efficiency and the potentialities of the RAT technique have been tested even when it is applied to a wide area with extremely variable topography, land coverage and climatic characteristics (the whole Indian subcontinent). Bhuj-Gujarat's earthquake (occurred on 26th January 2001, MS ˜ 7.9) has been considered as a test case in the validation phase, while a relatively unperturbed period (no earthquakes with MS ≥ 5, in the same region and in the same period) has been analyzed for confutation purposes. To this aim, 6 years of Meteosat-5 TIR observations have been processed for the characterization of the TIR signal behaviour at each specific observation time and location. The anomalous TIR values, detected by RAT, have been evaluated in terms of time-space persistence in order to establish the existence of actually significant anomalous transients. The results indicate that the studied area was affected by significant positive thermal anomalies which were identified, at different intensity levels, not far from the Gujarat coast (since 15th January, but with a clearer evidence on 22nd January) and near the epicentral area (mainly on 21st January). On 25th January (1 day before Gujarat's earthquake) significant TIR anomalies appear on the Northern Indian subcontinent, showing a remarkable coincidence with the principal tectonic lineaments of the region (thrust Himalayan boundary). On the other hand, the results of the confutation analysis indicate that no meaningful TIR anomalies appear in the absence of seismic events with MS ≥ 5.

  8. Active seismic experiment

    NASA Technical Reports Server (NTRS)

    Kovach, R. L.; Watkins, J. S.; Talwani, P.

    1972-01-01

    The Apollo 16 active seismic experiment (ASE) was designed to generate and monitor seismic waves for the study of the lunar near-surface structure. Several seismic energy sources are used: an astronaut-activated thumper device, a mortar package that contains rocket-launched grenades, and the impulse produced by the lunar module ascent. Analysis of some seismic signals recorded by the ASE has provided data concerning the near-surface structure at the Descartes landing site. Two compressional seismic velocities have so far been recognized in the seismic data. The deployment of the ASE is described, and the significant results obtained are discussed.

  9. Seismic images of the active fault system in the Yunlin and Chiayi area of Taiwan.

    NASA Astrophysics Data System (ADS)

    Sun, Wei-Hsiang; Shih, Ruey-Chyuan

    2015-04-01

    The Yunlin and Chiayi area in western Taiwan are well known of having a higher risk of earthquake disaster. The main fault system that controls the structure deformation in this area consists of the Chiuchiungkeng fault, the Meishan fault, and the Gukeng fault. According to historical records, the 1906 Meishan earthquake, magnitude 7.1, was triggered by the right-lateral strike-slip fault Meishan fault. Previous Seismic surveys showed that the Meishan fault is a high angle fault with flower structure. The Chiuchiungkeng fault is a thrust fault, located at front of the western foothills. Formations on the hanging wall and foot wall of the fault, both dipping to the east with different angles, can be identified from seismic images. The Gukeng fault was never been studied before. From the recent study of GPS monitoring, we may found that the velocity field near the Gukeng fault had a significant difference at both side of the fault. In addition, there is other information showed that there exists an aseismic gap around the fault. The above phenomena could be considered as a stress accumulation along the Gukeng fault. In the other words, the Gukeng fault could be playing an important role of controlling the regional surface deformation and seismicity distribution in this area. In this case, it will be worthwhile of knowing where the Gukeng fault is, and its subsurface structure. In this presentation, we will show our study of the subsurface structure of the Gukeng fault by using the seismic exploration method. The data consist of the shallow seismic reflection images those conducted by ourselves and the deeper seismic profiles acquired by CPC. Three dimensional relationships between the Gukeng fault, the Meishan fault, the Chiuchiungkeng fault, and other structures such as the Hsiaomei anticline will be illustrated as well.

  10. Multi-Parameter Observation and Detection of Pre-Earthquake Signals in Seismically Active Areas

    NASA Technical Reports Server (NTRS)

    Ouzounov, D.; Pulinets, S.; Parrot, M.; Liu, J. Y.; Hattori, K.; Kafatos, M.; Taylor, P.

    2012-01-01

    The recent large earthquakes (M9.0 Tohoku, 03/2011; M7.0 Haiti, 01/2010; M6.7 L Aquila, 04/2008; and M7.9 Wenchuan 05/2008) have renewed interest in pre-anomalous seismic signals associated with them. Recent workshops (DEMETER 2006, 2011 and VESTO 2009 ) have shown that there were precursory atmospheric /ionospheric signals observed in space prior to these events. Our initial results indicate that no single pre-earthquake observation (seismic, magnetic field, electric field, thermal infrared [TIR], or GPS/TEC) can provide a consistent and successful global scale early warning. This is most likely due to complexity and chaotic nature of earthquakes and the limitation in existing ground (temporal/spatial) and global satellite observations. In this study we analyze preseismic temporal and spatial variations (gas/radon counting rate, atmospheric temperature and humidity change, long-wave radiation transitions and ionospheric electron density/plasma variations) which we propose occur before the onset of major earthquakes:. We propose an Integrated Space -- Terrestrial Framework (ISTF), as a different approach for revealing pre-earthquake phenomena in seismically active areas. ISTF is a sensor web of a coordinated observation infrastructure employing multiple sensors that are distributed on one or more platforms; data from satellite sensors (Terra, Aqua, POES, DEMETER and others) and ground observations, e.g., Global Positioning System, Total Electron Content (GPS/TEC). As a theoretical guide we use the Lithosphere-Atmosphere-Ionosphere Coupling (LAIC) model to explain the generation of multiple earthquake precursors. Using our methodology, we evaluated retrospectively the signals preceding the most devastated earthquakes during 2005-2011. We observed a correlation between both atmospheric and ionospheric anomalies preceding most of these earthquakes. The second phase of our validation include systematic retrospective analysis for more than 100 major earthquakes (M>5

  11. Radon-gas extraction and counting system for analyzing radon and radium in groundwater in seismically active areas

    SciTech Connect

    Knauss, K.

    1980-12-08

    A high concentration of radon in groundwater has attracted recent attention as a precursor of seismic activity. We have constructed a system that extracts and counts radon gas from solid, liquid, and gas samples. The radon is extracted in a closed system onto activated charcoal. The desorbed radon is then measured in a phosphored acrylic cell by scintillation counting of gross alpha radiation. The efficiency of the total system (extraction plus counting) is 90 +- 3% or better. Compact design and sturdy construction make the system completely portable and well suited to field operations in remote loations. Results are given for radon and radium in groundwaters in the Livermore area.

  12. Seismic Research in two selected seismic active areas of Greece from the Department of Geodesy and Surveying of AUTH

    NASA Astrophysics Data System (ADS)

    Asteriadis, G.; Contadakis, M. E.

    Among the various methods which can be used for the short term earthquake forecasting is that of the monitoring of the variations of the local water table. This method was applied in two areas of Greece which present high seismisity. The results so far of this research indicate that the following up of the water level and temperature of the shallow underground water of an area could be used together with other methods in use of the short term earthquake forecasting efficiently.(in Greeks)

  13. Regional Observation of Seismic Activity in Baekdu Mountain

    NASA Astrophysics Data System (ADS)

    Kim, Geunyoung; Che, Il-Young; Shin, Jin-Soo; Chi, Heon-Cheol

    2015-04-01

    Seismic unrest in Baekdu Mountain area between North Korea and Northeast China region has called attention to geological research community in Northeast Asia due to her historical and cultural importance. Seismic bulletin shows level of seismic activity in the area is higher than that of Jilin Province of Northeast China. Local volcanic observation shows a symptom of magmatic unrest in period between 2002 and 2006. Regional seismic data have been used to analyze seismic activity of the area. The seismic activity could be differentiated from other seismic phenomena in the region by the analysis.

  14. Study on Seismic Zoning of Sino-Mongolia Arc Areas

    NASA Astrophysics Data System (ADS)

    Xu, G.

    2015-12-01

    According to the agreement of Cooperation on seismic zoning between Institute of Geophysics, China Earthquake Administration and Research Center of Astronomy and Geophysics, Mongolian Academy of Science, the data of geotectonics, active faults, seismicity and geophysical field were collected and analyzed, then field investigation proceeded for Bolnay Faults, Ar Hutul Faults and Gobi Altay Faults, and a uniform earthquake catalogue of Mongolia and North China were established for the seismic hazard study in Sino-Mongolia arc areas. Furthermore the active faults and epicenters were mapped and 2 seismic belts and their 54 potential seismic sources are determined. Based on the data and results above mentioned the seismicity parameters for the two seismic belts and their potential sources were studied. Finally, the seismic zoning with different probability in Sino-Mongolia arc areas was carried out using China probabilistic hazard analysis method. By analyzing the data and results, we draw the following main conclusions. Firstly, the origin of tectonic stress field in the study areas is the collision and pressure of the India Plate to Eurasian Plate, passing from the Qinghai-Tibet Plateau. This is the reason why the seismicity is higher in the west than in the east, and all of earthquakes with magnitude 8 or greater occurred in the west. Secondly, the determination of the 2 arc seismic belts, Altay seismic belt and Bolnay-Baikal seismic belt, are reasonable in terms of their geotectonic location, geodynamic origin and seismicity characteristics. Finally, there are some differences between our results and the Mongolia Intensity Zoning map published in 1985 in terms of shape of seismic zoning map, especially in the areas near Ulaanbaatar. We argue that our relsults are reasonable if we take into account the data use of recent study of active faults and their parameters, so it can be used as a reference for seismic design.

  15. Patterns of seismic activity preceding large earthquakes

    NASA Technical Reports Server (NTRS)

    Shaw, Bruce E.; Carlson, J. M.; Langer, J. S.

    1992-01-01

    A mechanical model of seismic faults is employed to investigate the seismic activities that occur prior to major events. The block-and-spring model dynamically generates a statistical distribution of smaller slipping events that precede large events, and the results satisfy the Gutenberg-Richter law. The scaling behavior during a loading cycle suggests small but systematic variations in space and time with maximum activity acceleration near the future epicenter. Activity patterns inferred from data on seismicity in California demonstrate a regional aspect; increased activity in certain areas are found to precede major earthquake events. One example is given regarding the Loma Prieta earthquake of 1989 which is located near a fault section associated with increased activity levels.

  16. Global positioning system survey data for active seismic and volcanic areas of eastern Sicily, 1994 to 2013.

    PubMed

    Bonforte, Alessandro; Fagone, Sonia; Giardina, Carmelo; Genovese, Simone; Aiesi, Gianpiero; Calvagna, Francesco; Cantarero, Massimo; Consoli, Orazio; Consoli, Salvatore; Guglielmino, Francesco; Puglisi, Biagio; Puglisi, Giuseppe; Saraceno, Benedetto

    2016-01-01

    This work presents and describes a 20-year long database of GPS data collected by geodetic surveys over the seismically and volcanically active eastern Sicily, for a total of more than 6300 measurements. Raw data were initially collected from the various archives at the Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Catania-Osservatorio Etneo and organized in a single repository. Here, quality and completeness checks were performed, while all necessary supplementary information were searched, collected, validated and organized together with the relevant data. Once all data and information collections were completed, raw binary data were converted into the universal ASCII RINEX format; all data are provided in this format with the necessary information for precise processing. In order to make the data archive readily consultable, we developed software allowing the user to easily search and obtain the needed data by simple alphanumeric and geographic queries. PMID:27479914

  17. Ambient noise tomography in the Naruko/Onikobe volcanic area, NE Japan: implications for geofluids and seismic activity

    NASA Astrophysics Data System (ADS)

    Tamura, Jun; Okada, Tomomi

    2016-01-01

    To understand the earthquake generation in volcanic areas, it is important to investigate the presence of geofluids in the uppermost crust. We applied ambient noise tomography to the Naruko/Onikobe volcanic area and constructed a detailed 3-D S-wave velocity ( V s) model using continuous records from a dense seismic network and surrounding stations. The low-velocity zones were found beneath Naruko Volcano, Onikobe Caldera, and Mt. Kurikoma. The low-velocity zone beneath Onikobe Caldera may correspond to a magma reservoir, which is also characterized by surrounding S-wave reflectors. The molten magma originates from the upwelling flows in the mantle wedge. We also conducted the relocation of aftershocks of the 2008 Iwate-Miyagi Nairiku earthquake by double-difference tomography based on the obtained velocity model. Beneath Mt. Kurikoma, aftershock distribution delineates one of the unfavorably oriented fault planes of the main shock, which implies that the low-velocity zone around the fault plane is related to the presence of overpressurized fluid.

  18. Seismic Holography of Solar Activity

    NASA Technical Reports Server (NTRS)

    Lindsey, Charles

    2000-01-01

    The basic goal of the project was to extend holographic seismic imaging techniques developed under a previous NASA contract, and to incorporate phase diagnostics. Phase-sensitive imaging gives us a powerful probe of local thermal and Doppler perturbations in active region subphotospheres, allowing us to map thermal structure and flows associated with "acoustic moats" and "acoustic glories". These remarkable features were discovered during our work, by applying simple acoustic power holography to active regions. Included in the original project statement was an effort to obtain the first seismic images of active regions on the Sun's far surface.

  19. TEC variations over the Mediterranean during the seismic activity of 20th October, in the area of eastern Aegean

    NASA Astrophysics Data System (ADS)

    Contadakis, M. E.; Arabelos, D. N.; Asteriadis, G.; Spatalas, S. D.; Pikridas, Ch.

    2007-04-01

    It is well known that TEC variations over a particular site sustain variations of different causality, global (earth revolution, earth rotation, earth-tides, variations of the geomagnetic field etc.) or local (atmospheric or underground explosions, earthquakes, volcanoes etc. A lot of work has been done by a great number of researchers on the characteristics of ionospheric variations according to their causality (wave- length, attenuation and velocity and way of propagation). In order that TEC variations over a particular site be used as earthquake precursory diagnostic a concrete sense of the interrelation of TEC variations over different sites as well as their respond of the geomagnetic field variations would be of great interest. In this paper the TEC data of eight GPS stations of the EUREF network (AUT1, Thessaloniki, TUC2, Crete in Greece, MAT.Matera and LAMP, Lampedusa in Italy, GAIA, in Portugal, RABT, Rabat, EVPA, Evpatoria in Ukrain and TRAB, Trabson in Turkey) were analyzed using wavelet analysis in order to detect any frequency dependence of the correlation of TEC over different stations. In the same time frequency dependence of Dst and TEC variations are searched in order to detect any correlation. The main conclusion of this analysis is that the constituents of TEC variation with periods <3h are more suitable in searching for earthquake precursors. On the base of this conclusion the analyzed TEC series are searched for possible precursory phenomena. Variation in TEC constituents with periods <3h over the stations AUT1 and TUC2 occurred ±10days of the seismic activity may be attributed to this tectonic activity.

  20. Waveform through the subducted plate under the Tokyo region in Japan observed by a ultra-dense seismic network (MeSO-net) and seismic activity around mega-thrust earthquakes area

    NASA Astrophysics Data System (ADS)

    Sakai, S.; Kasahara, K.; Nanjo, K.; Nakagawa, S.; Tsuruoka, H.; Morita, Y.; Kato, A.; Iidaka, T.; Hirata, N.; Tanada, T.; Obara, K.; Sekine, S.; Kurashimo, E.

    2009-12-01

    In central Japan, the Philippine Sea plate (PSP) subducts beneath the Tokyo Metropolitan area, the Kanto region, where it causes mega-thrust earthquakes, such as the 1703 Genroku earthquake (M8.0) and the 1923 Kanto earthquake (M7.9) which had 105,000 fatalities. A M7 or greater earthquake in this region at present has high potential to produce devastating loss of life and property with even greater global economic repercussions. The Central Disaster Management Council of Japan estimates the next great earthquake will cause 11,000 fatalities and 112 trillion yen (1 trillion US$) economic loss. This great earthquake is evaluated to occur with a probability of 70 % in 30 years by the Earthquake Research Committee of Japan. We had started the Special Project for Earthquake Disaster Mitigation in Tokyo Metropolitan area (2007-2012). Under this project, the construction of the Metropolitan Seismic Observation network (MeSO-net) that consists of about 400 observation sites was started [Kasahara et al., 2008; Nakagawa et al., 2008]. Now, we had 178 observation sites. The correlation of the wave is high because the observation point is deployed at about 2 km intervals, and the identification of the later phase is recognized easily thought artificial noise is very large. We also discuss the relation between a deformation of PSP and intra-plate M7+ earthquakes: the PSP is subducting beneath the Honshu arc and also colliding with the Pacific plate. The subduction and collision both contribute active seismicity in the Kanto region. We are going to present a high resolution tomographic image to show low velocity zone which suggests a possible internal failure of the plate; a source region of the M7+ intra-plate earthquake. Our study will contribute a new assessment of the seismic hazard at the Metropolitan area in Japan. Acknowledgement: This study was supported by the Earthquake Research Institute cooperative research program.

  1. Integrated multi-parameters Probabilistic Seismic Landslide Hazard Analysis (PSLHA): an innovative approach in the active volcano-tectonic area of Campi Flegrei (Italy)

    NASA Astrophysics Data System (ADS)

    Caccavale, M.; Matano, F.; Sacchi, M.; Somma, R.; Troise, C.; De Natale, G.

    2013-12-01

    The western coastal sector of Campania region (southern Italy) is characterised by the presence of the active volcano-tectonic area of Campi Flegrei. This area represents a very particular and interesting case-study for a probabilistic seismic hazard analysis (PSHA). The principal seismic source, related with the caldera, is not clearly constrained in the on-shore and off-shore areas. The well-known and monitored phenomenon of bradyseism affecting a large portion of case-study area is not modelled in the standard PSHA approach. From the environmental point of view the presence of very high exposed values in terms of population, buildings, infrastructures and palaces of high archaeological, natural and artistic value, makes this area a strategic natural laboratory to develop new methodologies. Moreover the geomorphological and geo-volcanological features lead to a heterogeneous coastline, made up by both beach and tuff cliffs, rapidly evolving for erosion and landslide (i.e. mainly rock fall and rock slide) phenomena that represent an additional hazard aspect. In the Campi Flegrei the possible occurrence of a moderate/large seismic event represents a serious threat for the inhabitants, for the infrastructures as well as for the environment. In the framework of Italian MON.I.C.A project (sinfrastructural coastlines monitoring) an innovative and dedicated probabilistic methodology has been applied to identify the areas with higher tendency of landslide occurrence due to the seismic effect. Resident population reported the occurrence of some small rock falls along tuff quarry slopes during the main shocks of the 1982-84 bradyseismic events. The PSHA methodology, introduced by Cornell (1968), combines the contributions to the hazard from all potential sources of earthquakes and the average activity rates associated to each seismogenic zone considered. The result of the PSHA is represented by the spatial distribution of a ground-motion (GM) parameter A, such as Peak

  2. Volcano Observations Using an Unmanned Autonomous Helicopter : seismic and GPS observations near the active summit area of Sakurajima and Kirishima volcano, Japan

    NASA Astrophysics Data System (ADS)

    Ohminato, T.; Kaneko, T.; Koyama, T.; Watanabe, A.; Takeo, M.; Iguchi, M.; Honda, Y.

    2012-04-01

    Observations in the vicinity of summit area of active volcanoes are very important from various viewpoints such as understanding physical processes in the volcanic conduit. It is, however, highly difficult to install observation sensors near active vents because of the risk of sudden eruptions. We have been developing a safe volcano observation system based on an unmanned aerial vehicle (UAV). As an UAV, we adopted an unmanned autonomous helicopter manufactured by Yamaha-Motor Co., Ltd. We have also developed earthquake observation modules and GPS receiver modules that are exclusively designed for UAV installation at summit areas of active volcanoes. These modules are light weight, compact size, and solar powered. For data transmission, a commercial cellular-phone network is used. Our first application of the sensor installation by the UAV is Sakurajima, one of the most active volcanos in Japan. In November 2009, 2010, and 2011, we installed up to four seismic sensors within 2km from the active summit crater. In the 2010 and 2011 operations, we succeeded in pulling up and collecting the sensor modules by using the UAV. In the 2011 experiment, we installed two GPS receivers near the summit area of Sakurajima volcano. We also applied the UAV installation to another active volcano, Shinmoedake in Kirishima volcano group. Since the sub-plinian eruption in February 2011, entering the area 3km from the summit of Shinmoe-dake has been prohibited. In May and November 2011, we installed seismic sensors and GPS receivers in the off-limit zone. Although the ground coupling of the seismic modules is not perfect due to the way they are installed, the signal-to-noise ratio of the seismic signals recorded by these modules is fairly good. Despite the low antenna height of 50 cm from the ground surface, the location errors in horizontal and vertical GPS components are 1cm and 3cm, respectively. For seismic signals associated with eruptions at Sakurajima from November 2010 to

  3. Observations of seismic activity in Southern Lebanon

    NASA Astrophysics Data System (ADS)

    Meirova, T.; Hofstetter, R.

    2013-04-01

    Recent seismic activity in southern Lebanon is of particular interest since the tectonic framework of this region is poorly understood. In addition, seismicity in this region is very infrequent compared with the Roum fault to the east, which is seismically active. Between early 2008 and the end of 2010, intense seismic activity occurred in the area. This was manifested by several swarm-like sequences and continuous trickling seismicity over many days, amounting in total to more than 900 earthquakes in the magnitude range of 0.5 ≤ M d ≤ 5.2. The region of activity extended in a 40-km long zone mainly in a N-S direction and was located about 10 km west of the Roum fault. The largest earthquake, with a duration magnitude of M d = 5.2, occurred on February 15, 2008, and was located at 33.327° N, 35.406° E at a depth of 3 km. The mean-horizontal peak ground acceleration observed at two nearby accelerometers exceeded 0.05 g, where the strongest peak horizontal acceleration was 55 cm/s2 at about 20 km SE of the epicenter. Application of the HypoDD algorithm yielded a pronounced N-S zone, parallel to the Roum fault, which was not known to be seismically active. Focal mechanism, based on full waveform inversion and the directivity effect of the strongest earthquake, suggests left-lateral strike-slip NNW-SSE faulting that crosses the NE-SW traverse faults in southern Lebanon.

  4. Seismic activity of Erebus volcano, antarctica

    NASA Astrophysics Data System (ADS)

    Kaminuma, Katsutada

    1987-11-01

    Mount Erebus is presently the only Antarctic volcano with sustained eruptive activity in the past few years. It is located on Ross Island and a convecting anorthoclase phonolite lava lake has occupied the summit crater of Mount Erebus from January 1973 to September 1984. A program to monitor the seismic activity of Mount Erebus named IMESS was started in December 1980 as an international cooperative program among Japan, the United States and New Zealand. A new volcanic episode began on 13 September, 1984 and continued until December. Our main observations from the seismic activity from 1982 1985 are as follows: (1) The average numbers of earthquakes which occurred around Mount Erebus in 1982, 1983 and January August 1984 were 64, 134 and 146 events per day, respectively. Several earthquake swarms occurred each year. (2) The averag number of earthquakes in 1985 is 23 events per day, with only one earthquake swarm. (3) A remarkable decrease of the background seismicity is recognized before and after the September 1984 activity. (4) Only a few earthquakes were located in the area surrounding Erebus mountain after the September 1984 activity. A magma reservoir is estimated to be located in the southwest area beneath the Erebus summit, based on the hypocenter distributions of earthquakes.

  5. A detailed seismic zonation model for shallow earthquakes in the broader Aegean area

    NASA Astrophysics Data System (ADS)

    Vamvakaris, D. A.; Papazachos, C. B.; Papaioannou, Ch. A.; Scordilis, E. M.; Karakaisis, G. F.

    2016-01-01

    In the present work we propose a new seismic zonation model of area type sources for the broader Aegean area, which can be readily used for seismic hazard assessment. The definition of this model is based not only on seismicity information but incorporates all available seismotectonic and neotectonic information for the study area, in an attempt to define zones which show not only a rather homogeneous seismicity release but also exhibit similar active faulting characteristics. For this reason, all available seismological information such as fault plane solutions and the corresponding kinematic axes have been incorporated in the analysis, as well as information about active tectonics, such as seismic and active faults. Moreover, various morphotectonic features (e.g. relief, coastline) were also considered. Finally, a revised seismic catalogue is employed and earthquake epicentres since historical times (550 BC-2008) are employed, in order to define areas of common seismotectonic characteristics, that could constitute a discrete seismic zone. A new revised model of 113 earthquake seismic zones of shallow earthquakes for the broader Aegean area is finally proposed. Using the proposed zonation model, a detailed study is performed for the catalogue completeness for the recent instrumental period.Using the defined completeness information, seismicity parameters (such as G-R values) for the 113 new seismic zones have been calculated, and their spatial distribution was also examined. The spatial variation of the obtained b values shows an excellent correlation with the geotectonic setting in the area, in good agreement with previous studies. Moreover, a quantitative estimation of seismicity is performed in terms of the mean return period, Tm, of large (M ≥ 6.0) earthquakes, as well as the most frequent maximum magnitude, Mt, for a typical time period (T = 50 yr), revealing significant spatial variations of seismicity levels within the study area. The new proposed

  6. Preceding seismic activity and slow slip events in the source area of the 2011 Mw 9.0 Tohoku-Oki earthquake: a review

    NASA Astrophysics Data System (ADS)

    Hasegawa, Akira; Yoshida, Keisuke

    2015-12-01

    The 2011 Tohoku-Oki earthquake ruptured a large area of the megathrust east of NE Japan. The earthquake's magnitude was 9.0, substantially larger than predicted. It is important to know what occurred in the source area prior to this great megathrust earthquake to improve understanding of the nucleation processes of large earthquakes and risk assessments in subduction zones. Seafloor observation data revealed the existence of two extremely large slip patches: one just updip of the mainshock hypocenter and the other 80-100 km to the north near the trench axis. For 70-90 years before 2003, M > 6 events and slips of M > c. 7 events on the megathrust occurred in the areas surrounding these two large slip patches. Seismic activity had increased since at least 2003 in the downdip portion of the source area of the Tohoku-Oki earthquake. In addition, long-term accelerated slow slip occurred in this downdip portion of the source area in the decades before the Tohoku-Oki earthquake. About 1 month before the earthquake, a slow slip event (SSE) took place at relatively shallow depths between the two large slip patches, accompanied by foreshock activity. Both the slow slip and foreshocks propagated from north to south toward the southern large slip patch. Two days before the earthquake, an M 7.3 foreshock and an associated postseismic slip began at relatively deep depths in the megathrust between the two large slip patches. In addition, a slow slip type event seems to have occurred approximately half a day after the M 7.3 foreshock near the mainshock hypocenter. This slow slip event and the foreshock activity again propagated from north to south toward the mainshock hypocenter. These long- and short-term preceding seismic and aseismic slip gradually reduced the interplate coupling, increased shear stresses at the two large slip patches (i.e., two strong asperity patches), and finally led to the rupture of the great Tohoku-Oki earthquake.

  7. Repeat Measurements of Seismic Noise at the Waiotapu Geothermal Area, North Island, NZ

    SciTech Connect

    Whiteford, P.C.

    1995-01-01

    The amplitudes of seismic ground noise were remeasured at 66 sites in the Waiotapu and Reporoa geothermal areas in 1995 to determine whether amplitudes had changed since the first survey in 1970. In both 1995 and 1970 high levels of seismic noise occurred in two localities, one at Waiotapu and one at Reporoa. The elevated levels of seismic noise at most sites are thought to be caused by surface or near-surface geothermal activity. At seven sites in the Waiotapu area seismic noise levels were almost the same in 1995 as in 1970, indicating no change in the intensity of the source of the geothermal seismic noise. At most other sites the 1995 seismic noise levels were different to those measured in 1970, although at sites with high levels of seismic noise the differences were usually less than at sites with low levels of seismic noise.

  8. TEC variations over the Mediterranean during the seismic activity period of the last quarter of 2005 in the area of Greece

    NASA Astrophysics Data System (ADS)

    Contadakis, M. E.; Arabelos, D. N.; Asteriadis, G.; Spatalas, S. D.; Pikridas, Ch.

    2008-04-01

    TEC variations over a particular site sustain variations of different causality, global (earth revolution, earth rotation, earth-tides, variations of the geomagnetic field etc.) or local (atmospheric or underground explosions, earthquakes, volcanoes etc. A lot of work has been done by a great number of researchers on the characteristics of ionospheric variations according to their causality (wave - length, attenuation and velocity and way of propagation). In order that TEC variations over a particular site be used as earthquake precursory diagnostic a concrete sense of the interrelation of TEC variations over different sites as well as their respond of the geomagnetic field variations would be of great interest. In this paper the TEC data of eight GPS stations of the EUREF network (AUT1, Thessaloniki and TUC2, Crete in Greece, MAT, Matera and LAMP, Lampedusa in Italy, GAIA in Portugal, RABT in Rabat, EVPA, Evpatoria in Ukrain and TRAB, Trabson in Turkey) were analyzed using wavelet and DFTanalysis in order to detect any frequency dependence of the correlation of TEC over different stations. In the same time, frequency dependence of Dst and TEC variations are searched in order to detect any correlation. The main conclusion of this analysis is that the constituents of TEC variation with periods <3h are more suitable in searching for earthquake precursors. On the base of this conclusion the analyzed TEC series are searched for possible precursory phenomena, during the seismic activity of the last quarter of 2005, in the area of Greece. Variation in TEC constituents with periods <3h over the stations AUT1 and TUC2 occurred ±10days of the seismic activity may be attributed to this tectonic activity.

  9. The Pollino Seismic Sequence: Activated Graben Structures in a Seismic Gap

    NASA Astrophysics Data System (ADS)

    Rößler, Dirk; Passarelli, Luigi; Govoni, Aladino; Bindi, Dino; Cesca, Simone; Hainzl, Sebatian; Maccaferri, Francesco; Rivalta, Eleonora; Woith, Heiko; Dahm, Torsten

    2015-04-01

    The Mercure Basin (MB) and the Castrovillari Fault (CF) in the Pollino range (Southern Apennines, Italy) represent one of the most prominent seismic gaps in the Italian seismic catalogue, with no M>5.5 earthquakes during the last centuries. In historical times several swarm-like seismic sequences occurred in the area including two intense swarms within the past two decades. The most energetic one started in 2010 and has been still active in 2014. The seismicity culminated in autumn 2012 with a M=5 event on 25 October. The range hosts a number of opposing normal faults forming a graben-like structure. Their rheology and their interactions are unclear. Current debates include the potential of the MB and the CF to host large earthquakes and the style of deformation. Understanding the seismicity and the behaviour of the faults is necessary to assess the tectonics and the seismic hazard. The GFZ German Research Centre for Geosciences and INGV, Italy, have jointly monitored the ongoing seismicity using a small-aperture seismic array, integrated in a temporary seismic network. Based on this installation, we located more than 16,000 local earthquakes that occurred between November 2012 and September 2014. Here we investigate quantitatively all the phases of the seismic sequence starting from January 2010. Event locations along with moment tensor inversion constrain spatially the structures activated by the swarm and the migration pattern of the seismicity. The seismicity forms clusters concentrated within the southern part of the MB and along the Pollino Fault linking MB and CF. Most earthquakes are confined to the upper 10 km of the crust in an area of ~15x15 km2. However, sparse seismicity at depths between 15 and 20 km and moderate seismicity further north with deepening hypocenters also exist. In contrast, the CF appears aseismic; only the northern part has experienced micro-seismicity. The spatial distribution is however more complex than the major tectonic structures

  10. Seismic signature of crustal magma and fluid from deep seismic sounding data across Tengchong volcanic area

    NASA Astrophysics Data System (ADS)

    Bai, Z. M.; Zhang, Z. Z.; Wang, C. Y.; Klemperer, S. L.

    2012-04-01

    The weakened lithosphere around eastern syntax of Tibet plateau has been revealed by the Average Pn and Sn velocities, the 3D upper mantle velocity variations of P wave and S wave, and the iimaging results of magnetotelluric data. Tengchong volcanic area is neighboring to core of eastern syntax and famous for its springs, volcanic-geothermal activities and remarkable seismicity in mainland China. To probe the deep environment for the Tengchong volcanic-geothermal activity a deep seismic sounding (DSS) project was carried out across the this area in 1999. In this paper the seismic signature of crustal magma and fluid is explored from the DSS data with the seismic attribute fusion (SAF) technique, hence four possible positions for magma generation together with some locations for porous and fractured fluid beneath the Tengchong volcanic area were disclosed from the final fusion image of multi seismic attributes. The adopted attributes include the Vp, Vs and Vp/Vs results derived from a new inversion method based on the No-Ray-Tomography technique, and the migrated instantaneous attributes of central frequency, bandwidth and high frequency energy of pressure wave. Moreover, the back-projected ones which are mainly consisted by the attenuation factor Qp , the delay-time of shear wave splitting, and the amplitude ratio between S wave and P wave + S wave were also considered in this fusion process. Our fusion image indicates such a mechanism for the surface springs: a large amount of heat and the fluid released by the crystallization of magma were transmitted upward into the fluid-filled rock, and the fluid upwells along some pipeline since the high pressure in deep, thus the widespread springs of Tengchong volcanic area were developed. Moreover, the fusion image, regional volcanic and geothermal activities, and the seismicity suggest that the main risk of volcanic eruption was concentrated to the south of Tengchong city, especially around the shot point (SP) Tuantian

  11. 3D image of Brittle/Ductile transition in active volcanic area and its implication on seismicity: The Campi Flegrei caldera case study

    NASA Astrophysics Data System (ADS)

    Castaldo, Raffaele; Luca, D'auria; Susi, Pepe; Giuseppe, Solaro; Pietro, Tizzani

    2015-04-01

    The thermo-rheology of the rocks is a crucial aspect to understand the mechanical behavior of the crust in young and tectonically active area. As a consequence, several studies have been performed since last decades in order to understand the role of thermic state in the evolution of volcanic environments. In this context, we analyze the upper crust rheology of the Campi Flegrei active caldera (Southern Italy). Our target is the evaluation of the 3D geometry of the Brittle-Ductile transition beneath the resurgent caldera, by integrating the available geological, geochemical, and geophysical data. We first performed a numerical thermal model by using the a priori geological and geophysical information; than we employ the retrieved isothermal distribution to image the rheological stratification of the shallow crust beneath caldera. In particular, considering both the thermal proprieties and the mechanical heterogeneities of the upper crust, we performed, in a Finite Element environment, a 3D conductive time dependent thermal model through an numerical of solution of the Fourier equation. The dataset consist in temperature measurements recorded in several deep wells. More specifically, the geothermal gradients were measured in seven deep geothermal boreholes, located in three main distinct areas: Mofete, Licola, and San Vito. In addition, we take into account also the heat flow density map at the caldera surface calculated by considering the thermal measurements carried out in 30 shallow water wells. We estimate the isothermal distribution of the crust calibrating two model parameters: the heat production [W], associated to the magma injection episodes in the last 60 kyears within the magma chamber and the heat flow coefficient [W/m2*K] at the external surface. In particular, the optimization procedure has been performed using an exhaustive grid search, to minimize the differences between model and experimental measurements. The achieved results allowed us to

  12. Hydro-meteorological hazards associated with extreme precipitation events in a geomorphological-active area of Europe: Vrancea-Buzau Seismic Region

    NASA Astrophysics Data System (ADS)

    Dragota, C.; Micu, D.; Zarea, R.; Micu, M.

    2012-04-01

    When a high incidence of hydro-meteorological hazards characterizes a region where its coping capacity is poorly developed, the elements at risk vulnerability may notable increase. This is the case of Vrancea-Buzau Seismic Region, located in the Curvature Carpathians and Subcarpathians of Romania. This region is one of Europe's most landslide-prone areas, which also experiences propitious conditions for flash-floods, and is at the same time, the most active cub-crustal province of Europe. This paper aims at presenting the meteorological framework of heavy rain events occurrence, highlighting their role in the region's hydrology and geomorphology. The paper outlines some typical synoptic conditions favourable for triggering severe flash-flood and multiple-landslides events (e.g. Mediterranean fronts, retrograde Cyclones or trans-Carpathian air mass advections). By selecting several case studies (i.e. 1975 and 2005, considered the wettest years from the observational data in the region), characterizing both the Carpathian mountains and the Subcarpathian hills and depressions, a preliminary inventory of damages caused by such processes was undertaken, as a basis for a future vulnerability assessment in the region. The presence of numerous elements at risk (e.g. a dense and sometimes continuous network of villages or scattered households) overlaps one of Europe's most reduced income/family areas. Consequently, an increase of the potential losses value was observed in the last decades due to heavy rain episodes. The paper offers important results for the assessment of the flash-flood and landslide hazard at regional level (FP7 MC-ITN CHANGES Project), as a necessary input for the local strategies of risk reduction, by determining the potential recurrence intervals for certain thresholds of one of the most important triggering factors such as precipitation.

  13. Precursory seismic activity before the 1944 Tonankai (Japan) earthquake: focusing on the downward migration of seismic activity

    NASA Astrophysics Data System (ADS)

    Mogi, Kiyoo

    1987-08-01

    Based on the latest JMA earthquake catalog, the author investigated seismic activity around the time of the 1944 Tonankai earthquake ( M 7.9, M w 8.1 ) and the 1946 Nankaido earthquake ( M 8.1, M w 8.1 ), which were both great thrust-type earthquakes along the Nankai Trough. For about 20 years before these earthquakes their focal regions had been quiescent (appearance of a seismic gap of the second kind) and the surrounding areas had become increasingly active, forming a doughnut pattern). Several years before these earthquakes occurred seismic activity increased at shallow depths of the area to the north. This activity gradually migrated downwards, and the Tonankai earthquake occurred when it reached its limit (a depth of approximately 70 km). The author has previously reported on several cases of increased activity in the deep seismic plane at a depth of 300-500 km prior to large shallow earthquakes along the Japan Trench (Mogi, 1973). This paper will demonstrate that a similar phenomenon occurs when the depth of the deep seismic plane is only about 70 km. For several years before the Tonankai earthquake there had been a slight increase in seismicity in the area along the trough, which is where the plate subducts. Two or three days before tne earthquake marked ground tilt also proceeded at the northeastern tip of the focal region. It is evident that the Tonankai earthquake was preceded by various long-term and short-term precursory phenomena.

  14. Geyser's Eruptive Activity in Broadband Seismic Records

    NASA Astrophysics Data System (ADS)

    Kugaenko, Yulia; Saltykov, Vadim

    2010-05-01

    -phase steam mixture and the conduit wall, due to an increased amount of steam in final stages of boiling. The most important result is detection of hidden underground geyser in the area of the Giant geyser. Its deep activity is recorded by seismometer (by seismic and mass position channels) as very stable quasi-periodic oscillations with period 16-18 min. Earlier the existents of the underground geyser was assumed due to observation of intense bursts with such periodicity during boiling-effusion mode berofe every eruption of the Giant geyser. So the supposed underground geyser was accounted as the main heat provider and the principal cause of the Giant geyser eruptions. We named this deep quasi-periodic source of seismic signal (underground geyser) "Heart of Giant". As a result of that, our reconnaissance seismic survey is informative and shows some new facts about geysers, which were not detected earlier by other most traditional methods of geyser study. The main task for future seismic research in the Valley of the Geysers is the location and more particular analysis of the underground "Heart of Giant" geyser.

  15. A Seismic Structure Study in the Kaoping Area, Southwestern Taiwan

    NASA Astrophysics Data System (ADS)

    Chen, K. P.; Wang, C. Y.; Tsai, Y. B.; Chang, W. Y.

    2014-12-01

    The difference between S wave and S-to-P wave conversion (Sp phase) arrival times is enhanced with Rectilinear Motion Detector filtering to describe alluvial-sediment thickness in the Kaohsiung-Pingtung (Kaoping) plains area. A more complete understanding of the underground structures of the Kaoping area is provided and explains why the surrounding regions in Taiwan experience more earthquakes. Data are based on seismic activity recorded by PANDA for the period 1995 to 1997. The difference between S wave and Sp phase arrival times show that the sedimentary layer is thicker along the west and southwest coast. P wave travel time residuals, high frequency attenuation parameters kappa, and quality factor QP, QSand coda waves confirm this result. We also determined the orientation of the Chaochou fault using the first motion of P-waves arrivals. To the east of the Chaochou fault, stress trends southeast-northwest, while to the west, it trends northeast-southwest. The change of stress trends East and West of Chaochou fault suggest the presence of a highly fluid accretionary wedge in the Kaoping area. The Chaochou fault forms a seismically active tectonic boundary with uplift of the hanging wall leading to westward tilting of the basement of the Kaoping plains. We demonstrate these features are why there are relatively few earthquakes in the Kaoping area. The presence of a highly fluid accretionary wedge is indicated by a thick alluvial layer in the west and southwest Kaoping coast; the Peikung High acts as the indenter that may allow seismic energy to escape and reduce the number of earthquakes in the region.

  16. Seismicity and Faulting in an Urbanized area: Flagstaff, Arizona

    NASA Astrophysics Data System (ADS)

    Brumbaugh, D. S.

    2013-12-01

    Flagstaff, Arizona is a community of more than 60,000 and lies in an area of active tectonism. Well documented evidence exists of geologically recent volcanism and fault related seismicity. The urban area is located within a volcanic field that is considered active and the area is also the locus of numerous fault systems, some of whose members are considered to be potentially active. This suggestion of active faulting and seismicity for the area is supported by the recent 1993 Mw 5.3 Cataract Creek earthquake. Chief concern for Flagstaff is focused upon the Anderson Mesa fault which has a mapped surface length of 40 kilometers with the north end extending into the city limits of Flagstaff. A worse case scenario for rupture along the entire length of the fault would be the occurrence of an Mw 6.9 earthquake. The slip rate for this fault is low, however it is not well determined due to a lack of Neogene or Quaternary deposits. The historic record of seismicity adjacent to the surface expression of the Anderson Mesa fault includes two well recorded earthquake swarms (1979,2011) as well as other individual events over this time period all of which are of M< 4.0. The epicentral locations of these events are of interest with respect to the fault geometry which shows four prominent segments: North, Central, South, Ashurst. All of the historic events are located within the central segment. This distribution can be compared to evidence available for the orientation of regional stresses. The focal mechanism for the 1993 Mw 5.3 Cataract Creek earthquake shows a northwest striking preferred slip surface with a trend (300) parallel to that of the Central segment of the Anderson Mesa fault (300-305). The other three fault segments of the Anderson Mesa fault have north-south trends. The seismicity of the Central segment of the fault suggests that slip on this segment may occur in the future. Given the length of this segment a MCE event could be as large as Mw 6.3.

  17. Seismic hazard assessment of Syria using seismicity, DEM, slope, active tectonic and GIS

    NASA Astrophysics Data System (ADS)

    Ahmad, Raed; Adris, Ahmad; Singh, Ramesh

    2016-07-01

    In the present work, we discuss the use of an integrated remote sensing and Geographical Information System (GIS) techniques for evaluation of seismic hazard areas in Syria. The present study is the first time effort to create seismic hazard map with the help of GIS. In the proposed approach, we have used Aster satellite data, digital elevation data (30 m resolution), earthquake data, and active tectonic maps. Many important factors for evaluation of seismic hazard were identified and corresponding thematic data layers (past earthquake epicenters, active faults, digital elevation model, and slope) were generated. A numerical rating scheme has been developed for spatial data analysis using GIS to identify ranking of parameters to be included in the evaluation of seismic hazard. The resulting earthquake potential map delineates the area into different relative susceptibility classes: high, moderate, low and very low. The potential earthquake map was validated by correlating the obtained different classes with the local probability that produced using conventional analysis of observed earthquakes. Using earthquake data of Syria and the peak ground acceleration (PGA) data is introduced to the model to develop final seismic hazard map based on Gutenberg-Richter (a and b values) parameters and using the concepts of local probability and recurrence time. The application of the proposed technique in Syrian region indicates that this method provides good estimate of seismic hazard map compared to those developed from traditional techniques (Deterministic (DSHA) and probabilistic seismic hazard (PSHA). For the first time we have used numerous parameters using remote sensing and GIS in preparation of seismic hazard map which is found to be very realistic.

  18. a Seismic Reflection Study on the Ablation Area of the Taku Glacier, Southeast Alaska

    NASA Astrophysics Data System (ADS)

    Zechmann, J. M.; Gusmeroli, A.; Booth, A.; Truffer, M.

    2014-12-01

    Active-source seismic reflection techniques have been frequently used to document temporal and spatial variability in subglacial conditions beneath the ice sheets. Seismic surveys may provide the topography of the subglacial landscape as well as information about the properties of subglacial sediments and water. The former is achieved by standard 2D seismic imaging, the latter by amplitude analysis of the base-ice reflection. Seismic techniques for subglacial characterization have not yet been fully explored on mountain glaciers, where the ice is warmer and more attenuative to seismic energy, and the area available for survey is often more restrictive. In March 2014 we collected a high-resolution seismic reflection survey on the lower ablation area of the Taku Glacier in South-East Alaska. The survey line was composed of 120 geophones buried 0.5 m in the snowpack and spaced by 5 meters. The surface of the glacier was covered by a spatially variable 2-6 m thick snow cover. Shots, 99 charges of the binary explosive kinepak (152 grams), were drilled to 6 meters below surface. We present preliminary seismic images, attenuation estimates and amplitude analysis as well as a discussion of the challenges of seismic studies in the ablation area of large mountain glaciers where spatially variable snowpack, rough topography and hidden crevasses hamper standard seismic interpretation and render successful data interpretation more difficult.

  19. 3D Modelling of Seismically Active Parts of Underground Faults via Seismic Data Mining

    NASA Astrophysics Data System (ADS)

    Frantzeskakis, Theofanis; Konstantaras, Anthony

    2015-04-01

    During the last few years rapid steps have been taken towards drilling for oil in the western Mediterranean sea. Since most of the countries in the region benefit mainly from tourism and considering that the Mediterranean is a closed sea only replenishing its water once every ninety years careful measures are being taken to ensure safe drilling. In that concept this research work attempts to derive a three dimensional model of the seismically active parts of the underlying underground faults in areas of petroleum interest. For that purpose seismic spatio-temporal clustering has been applied to seismic data to identify potential distinct seismic regions in the area of interest. Results have been coalesced with two dimensional maps of underground faults from past surveys and seismic epicentres, having followed careful reallocation processing, have been used to provide information regarding the vertical extent of multiple underground faults in the region of interest. The end product is a three dimensional map of the possible underground location and extent of the seismically active parts of underground faults. Indexing terms: underground faults modelling, seismic data mining, 3D visualisation, active seismic source mapping, seismic hazard evaluation, dangerous phenomena modelling Acknowledgment This research work is supported by the ESPA Operational Programme, Education and Life Long Learning, Students Practical Placement Initiative. References [1] Alves, T.M., Kokinou, E. and Zodiatis, G.: 'A three-step model to assess shoreline and offshore susceptibility to oil spills: The South Aegean (Crete) as an analogue for confined marine basins', Marine Pollution Bulletin, In Press, 2014 [2] Ciappa, A., Costabile, S.: 'Oil spill hazard assessment using a reverse trajectory method for the Egadi marine protected area (Central Mediterranean Sea)', Marine Pollution Bulletin, vol. 84 (1-2), pp. 44-55, 2014 [3] Ganas, A., Karastathis, V., Moshou, A., Valkaniotis, S., Mouzakiotis

  20. Stochastic seismic analysis in the Messina strait area

    SciTech Connect

    Cacciola, P.; Maugeri, N.; Muscolino, G.

    2008-07-08

    After 1908 Messina earthquake significant progresses have been carried out in the field of earthquake engineering. Usually seismic action is represented via the so called elastic response spectrum or alternatively by time histories of ground motion acceleration. Due the random nature of the seismic action, alternative representations assume the seismic action as zero-mean Gaussian process fully defined by the so-called Power Spectral Density function. Aim of this paper is the comparative study of the response of linear behaving structures adopting the above representation of the seismic action using recorded earthquakes in the Messina strait area. In this regard, a handy method for determining the power spectral density function of recorded earthquakes is proposed. Numerical examples conducted on the existing space truss located in Torre Faro (Messina) will show the effectiveness of stochastic approach for coping with the seismic analysis of structures.

  1. Study on Seismicity of Sino-Mongolia Arc Areas

    NASA Astrophysics Data System (ADS)

    Xu, Guangyin; Wang, Suyun

    2016-04-01

    Using the earthquake catalogue from China, Mongolia and the global catalogue, the uniform catalogue of North China, Mongolia and adjacent areas, which is within the region 80-130°E, 40-55°N, has been established by Institute of Geophysics, China Earthquake Administration and Research Center of Astronomy and Geophysics, Mongolian Academy of Science for the seismic hazard analysis and seismic zoning map of Mongolia according to the following principles. 1) Earthquakes, which just exist in one catalogue, need to be verified further. If the earthquakes occurred in the country where the catalog comes from, then they will be adopted. If not, it should be checked with other more data. 2) The events that come from the three data sources have be checked and verified as followings. (1) The parameters of earthquakes that occurred in China will be taken from China catalog. (2)The parameters of earthquakes that occurred in Mongolia will be taken from Mongolia catalog. (3) The parameters of earthquakes that occurred in the adjacent areas will be taken from the global catalog by Song et al. According to the uniform catalogue, the seismicity of the North China, Mongolia and adjacent areas is analyzed, and the conclusions as followings are made. 1) The epicenter map can be roughly divided into two parts, bounded by the longitude line 105°E , in accordance with the "North-South Seismic Belt" of China. The seismicity is in a high level with many strong earthquakes in the west and is in a low level with little strong events in the east. 2) Most earthquakes are shallow-focus events, but there are also several middle or deep-focus events in the study area. 3) Earthquakes with magnitude greater than 5 are basically complete since 1450 A.D., and the seismicity of the study areas is in a high level since 1700 A. 4) Two seismic belts, Altay seismic belt and Bolnay-Baikal seismic belt, are determined according to the epicenters and tectonics. 5) The b-values of magnitude - frequency

  2. Successes and failures of recording and interpreting seismic data in structurally complex area: seismic case history

    SciTech Connect

    Morse, V.C.; Johnson, J.H.; Crittenden, J.L.; Anderson, T.D.

    1986-05-01

    There are successes and failures in recording and interpreting a single seismic line across the South Owl Creek Mountain fault on the west flank of the Casper arch. Information obtained from this type of work should help explorationists who are exploring structurally complex areas. A depth cross section lacks a subthrust prospect, but is illustrated to show that the South Owl Creek Mountain fault is steeper with less apparent displacement than in areas to the north. This cross section is derived from two-dimensional seismic modeling, using data processing methods specifically for modeling. A flat horizon and balancing technique helps confirm model accuracy. High-quality data were acquired using specifically designed seismic field parameters. The authors concluded that the methodology used is valid, and an interactive modeling program in addition to cross-line control can improve seismic interpretations in structurally complex areas.

  3. Network Optimization for Induced Seismicity Monitoring in Urban Areas

    NASA Astrophysics Data System (ADS)

    Kraft, T.; Husen, S.; Wiemer, S.

    2012-12-01

    With the global challenge to satisfy an increasing demand for energy, geological energy technologies receive growing attention and have been initiated in or close to urban areas in the past several years. Some of these technologies involve injecting fluids into the subsurface (e.g., oil and gas development, waste disposal, and geothermal energy development) and have been found or suspected to cause small to moderate sized earthquakes. These earthquakes, which may have gone unnoticed in the past when they occurred in remote sparsely populated areas, are now posing a considerable risk for the public acceptance of these technologies in urban areas. The permanent termination of the EGS project in Basel, Switzerland after a number of induced ML~3 (minor) earthquakes in 2006 is one prominent example. It is therefore essential to the future development and success of these geological energy technologies to develop strategies for managing induced seismicity and keeping the size of induced earthquake at a level that is acceptable to all stakeholders. Most guidelines and recommendations on induced seismicity published since the 1970ies conclude that an indispensable component of such a strategy is the establishment of seismic monitoring in an early stage of a project. This is because an appropriate seismic monitoring is the only way to detect and locate induced microearthquakes with sufficient certainty to develop an understanding of the seismic and geomechanical response of the reservoir to the geotechnical operation. In addition, seismic monitoring lays the foundation for the establishment of advanced traffic light systems and is therefore an important confidence building measure towards the local population and authorities. We have developed an optimization algorithm for seismic monitoring networks in urban areas that allows to design and evaluate seismic network geometries for arbitrary geotechnical operation layouts. The algorithm is based on the D-optimal experimental

  4. Upper plate responses to active spreading ridge/transform subduction: The tectonics, basin evolution, and seismicity of the Taita area, Chile Triple Junction

    SciTech Connect

    Flint, S.; Prior, D. ); Styles, P.; Murdie, R. ); Agar, S.; Turner, P. )

    1993-02-01

    Integrated field geophysical, structural and stratigraphic studies are attempting to elucidate the mechanisms and consequences of the Late Miocene-present day subduction of the Chile Ridge triple junction system. Preliminary data indicate a shallow plane of seismicity at about 15 km to 20 km depth below the Taitao peninsula. The depths correspond to the predicted depth range of subducted upper ocean crust. The calculated Bouguer anomaly map cannot be explained by the upper plate geology, suggesting that gravity is influenced by heterogeneities in the subducting oceanic plate. Seismic data imply that a subducted transform system underlying the inner Taitao Peninsula is still an active structure. A series of Middle-Late Tertiary sedimentary basins lie inboard of the triple junction. Within the Cosmelli basin, abrupt marine to continental facies transitions give clear evidence of base level changes. The amount of basinward shift of facies across sequence boundaries gets progressively greater up stratigraphy, indicating progressively greater base level changes. The lower part of the basin fill is folded and then thrusted eastward as a series of imbricates, while the overlying, greater thickness of fluvial sediments are only gently tilted westwards. We provisionally interpret this geometry to indicate that the early basin fill was deforming due to contractional tectonics while the later basin fill was being deposited. This complex basin history may reflect initiation and development of triple junction subduction.

  5. Active Seismic Monitoring for Earthquake Forecasting

    NASA Astrophysics Data System (ADS)

    Artamonova, M.; Korneev, V.

    2005-12-01

    Earthquake prediction remains high priority issue for disaster prevention. Study of the M6.0 2004 Parkfield and M7.0 1989 Loma Prieta strike-slip earthquakes on the San Andreas Fault (SAF) reveal seismicity peaks in the surrounding crust several months prior to the main events. Earthquakes directly within the SAF zone were intentionally excluded from the analysis because they manifest stress-release processes rather than stress accumulation. The observed increase in seismicity is interpreted as a signature of the increasing stress level in the surrounding crust, while the peak that occurs several months prior to the main event and the subsequent decrease in seismicity are attributed to damage-induced softening processes. Furthermore, in both cases there is a distinctive zone of low seismic activity that surrounds the epicentral region in the pre-event period. The increase of seismicity in the crust surrounding a potential future event and the development of a low-seismicity epicentral zone can be regarded as promising precursory information that could help signal the arrival of large earthquakes. We modeled the seismicity precursor phenomena using finite-element 2D model capable to replicate non-linear breaking of elastic rock. The distinctive seismicity peak was observed for a model simulating SAF properties at Park field. Such peaks are likely to be a good mid-term precursors allowing to declare alerts several months before earthquakes and pointing on their epicenter regions. The short tern alerts require use of active sources and their proper placement in order to monitor the developments of rock softening processes.

  6. Continued seismic monitoring of the Geysers, California geothermal area

    SciTech Connect

    Ludwin, R.S.; Bufe, C.G.

    1980-01-01

    Probable effects of geothermal development on seismicity at the Geysers are shown by the spatial coherence of decreases in gravity and pressure with maximum geodetic deformation and seismic moment sum along a line through the most developed area of the geothermal field. Increases in the mean number of events per day and in the magnitude of largest annual event correlate with increases in steam production. The two largest earthquakes in the steam field occurred near the two injection wells most distant from production wells, and large events (M/sub c greater than or equal to 2.5) occurred most frequently during months of peak injection. Spatial seismic clusters in proximity to injection wells have occurred soon after injection began. Preliminary data also indicate an increase in seismicity in a previously aseismic area near plant 15 following the beginning of power production at that plant in 1979.

  7. Permafrost Active Layer Seismic Interferometry Experiment (PALSIE).

    SciTech Connect

    Abbott, Robert; Knox, Hunter Anne; James, Stephanie; Lee, Rebekah; Cole, Chris

    2016-01-01

    We present findings from a novel field experiment conducted at Poker Flat Research Range in Fairbanks, Alaska that was designed to monitor changes in active layer thickness in real time. Results are derived primarily from seismic data streaming from seven Nanometric Trillium Posthole seismometers directly buried in the upper section of the permafrost. The data were evaluated using two analysis methods: Horizontal to Vertical Spectral Ratio (HVSR) and ambient noise seismic interferometry. Results from the HVSR conclusively illustrated the method's effectiveness at determining the active layer's thickness with a single station. Investigations with the multi-station method (ambient noise seismic interferometry) are continuing at the University of Florida and have not yet conclusively determined active layer thickness changes. Further work continues with the Bureau of Land Management (BLM) to determine if the ground based measurements can constrain satellite imagery, which provide measurements on a much larger spatial scale.

  8. Multiharmonic model of seismic activity in Kamchatka

    NASA Astrophysics Data System (ADS)

    Sobolev, G. A.; Valeev, S. G.; Faskhutdinova, V. A.

    2010-12-01

    Based on the uniform catalogue of earthquakes of the minimum energy class 8.5 for 1962-2008, multiharmonic models of seismic activity in Kamchatka are developed. The main harmonic components with periods from a few days to 12 years are identified. Both the entire catalogue and its modified versions obtained by the elimination of aftershocks and clusters, as well as nonoverlapping time series were used to study the stability of the models. The forward-prediction testing showed that in the models with weekly averaged initial data, periods of increased and reduced seismic activity lasting for several weeks are predicted with high confidence on an interval of up to 1.8% of the education period. This testifies for the presence of deterministic components in the seismic activity.

  9. Apollo 14 active seismic experiment.

    PubMed

    Watkins, J S; Kovach, R L

    1972-03-17

    Explosion seismic refraction data indicate that the lunar near-surface rocks at the Apollo 14 site consist of a regolith 8.5 meters thick and characterized by a compressional wave velocity of 104 meters per second. The regolith is underlain by a layer with a compressional wave velocity of 299 meters per second. The thickness of this layer, which we interpret to be the Fra Mauro Formation, is between 16 and 76 meters. The layer immediately beneath this has a velocity greater than 370 meters per second. We found no evidence of permafrost. PMID:17794200

  10. Apollo 14 active seismic experiment.

    NASA Technical Reports Server (NTRS)

    Watkins, J. S.; Kovach, R. L.

    1972-01-01

    Explosion seismic refraction data indicate that the lunar near-surface rocks at the Apollo 14 site consist of a regolith 8.5 meters thick and characterized by a compressional wave velocity of 104 meters per second. The regolith is underlain by a layer with a compressional wave velocity of 299 meters per second. The thickness of this layer, which we interpret to be the Fra Mauro Formation, is between 16 and 76 meters. The layer immediately beneath this has a velocity greater than 370 meters per second. We found no evidence of permafrost.

  11. Quantitative risk analysis of oil storage facilities in seismic areas.

    PubMed

    Fabbrocino, Giovanni; Iervolino, Iunio; Orlando, Francesca; Salzano, Ernesto

    2005-08-31

    Quantitative risk analysis (QRA) of industrial facilities has to take into account multiple hazards threatening critical equipment. Nevertheless, engineering procedures able to evaluate quantitatively the effect of seismic action are not well established. Indeed, relevant industrial accidents may be triggered by loss of containment following ground shaking or other relevant natural hazards, either directly or through cascade effects ('domino effects'). The issue of integrating structural seismic risk into quantitative probabilistic seismic risk analysis (QpsRA) is addressed in this paper by a representative study case regarding an oil storage plant with a number of atmospheric steel tanks containing flammable substances. Empirical seismic fragility curves and probit functions, properly defined both for building-like and non building-like industrial components, have been crossed with outcomes of probabilistic seismic hazard analysis (PSHA) for a test site located in south Italy. Once the seismic failure probabilities have been quantified, consequence analysis has been performed for those events which may be triggered by the loss of containment following seismic action. Results are combined by means of a specific developed code in terms of local risk contour plots, i.e. the contour line for the probability of fatal injures at any point (x, y) in the analysed area. Finally, a comparison with QRA obtained by considering only process-related top events is reported for reference. PMID:15908107

  12. Identifying induced seismicity in active tectonic regions: A case study of the San Joaquin Basin, California

    NASA Astrophysics Data System (ADS)

    Aminzadeh, F.; Göbel, T.

    2013-12-01

    Understanding the connection between petroleum-industry activities, and seismic event occurrences is essential to monitor, quantify, and mitigate seismic risk. While many studies identified anthropogenically-induced seismicity in intraplate regions where background seismicity rates are generally low, little is known about how to distinguish naturally occurring from induced seismicity in active tectonic regions. Further, it is not clear how different oil and gas operational parameters impact the frequency and magnitude of the induced seismic events. Here, we examine variations in frequency-size and spatial distributions of seismicity within the Southern Joaquin basin, an area of both active petroleum production and active fault systems. We analyze a newly available, high-quality, relocated earthquake catalog (Hauksson et al. 2012). This catalog includes many seismic events with magnitudes up to M = 4.5 within the study area. We start by analyzing the overall quality and consistence of the seismic catalog, focusing on temporal variations in seismicity rates and catalog completeness which could indicate variations in network sensitivity. This catalog provides relatively homogeneous earthquake recordings after 1981, enabling us to compare seismicity rates before and after the beginning of more pervasive petroleum-industry activities, for example, hydraulic-fracturing and waste-water disposals. We conduct a limited study of waste-water disposal wells to establish a correlation between seismicity statistics (i.e. rate changes, fractal dimension, b-value) within specific regions and anthropogenic influences. We then perform a regional study, to investigate spatial variations in seismicity statistics which are then correlated to oil field locations and well densities. In order to distinguish, predominantly natural seismicity from induced seismicity, we perform a spatial mapping of b-values and fractal dimensions of earthquake hypocenters. Seismic events in the proximity to

  13. Lunar seismic profiling experiment natural activity study

    NASA Technical Reports Server (NTRS)

    Duennebier, F. K.

    1976-01-01

    The Lunar Seismic Experiment Natural Activity Study has provided a unique opportunity to study the high frequency (4-20 Hz) portion to the seismic spectrum on the moon. The data obtained from the LSPE was studied to evaluate the origin and importance of the process that generates thermal moonquakes and the characteristics of the seismic scattering zone at the lunar surface. The detection of thermal moonquakes by the LSPE array made it possible to locate the sources of many events and determine that they are definitely not generated by astronaut activities but are the result of a natural process on the moon. The propagation of seismic waves in the near-surface layers was studied in a qualitative manner. In the absence of an adequate theoretical model for the propagation of seismic waves in the moon, it is not possible to assign a depth for the scattering layer. The LSPE data does define several parameters which must be satisfied by any model developed in the future.

  14. Crustal Deformation around Zhangjiakou-Bohai Seismically Active Belt

    NASA Astrophysics Data System (ADS)

    Jin, H.; Fu, G.; Kato, T.

    2011-12-01

    Zhangjiakou-Bohai belt is a seismically active belt located in Northern China around Beijing, the capital of China. Near such a belt many great earthquakes occurred in the past centuries (e.g. the 1976 Tanshan Ms7.8 earthquake, the 1998 Zhangbei Ms6.2 earthquake, etc). Chinese Government established dense permanent and regional Global Positioning System (GPS) stations in and near the area. We collected and analyzed all the GPS observation data between 1999 and 2009 around Zhangjiakou-Bohai seismic belt, and obtained velocities at 143 stations. At the same time we investigated Zhangjiakou-Bohai belt slip rate for three profiles from northwest to southeast, and constructed a regional strain field on the Zhangjiakou-Bohai seismic belt region by least-square collocation. Based on the study we found that: 1) Nowadays the Zhangjiakou-Bohai seismic belt is creeping with left-lateral slip rate of 2.0mm~2.4mm/a, with coupling depth of 35~50km; 2) In total, the slip and coupling depth of the northwestern seismic belt is less than the one of southeast side; 3) The maximum shear strain is about 3×10-8 at Beijing-Tianjin-Tangshan area.

  15. Seismic Swarms at Paricutin Volcano Area. Magmatic Intrusion or Tectonic Seismicity?

    NASA Astrophysics Data System (ADS)

    Pinzon, J. I.; Nunez-Cornu, F. J.; Escudero, C. R.; Rowe, C. A.

    2014-12-01

    We relocate a seismic swarm with more than 700 earthquakes that took place between May and June 2006 in the Paricutin volcano area, Mexico inside of the Michoacan monogenetic volcanic field. This seismic swarm was recorded by the project "Mapping the Riviera Subduction Zone" (MARS), a temporary seismic network that was installed in the states of Jalisco, Colima and Michoacán between January 2006 and June 2007. Previously seismic swarms in the area were reported in the years of 1997, 1999 and 2000. For one that took place in the year of 1997 the Servicio Sismologico Nacional deployed a local network in the area, they conclude that the source of the seismicity was tectonic with depths between 18 and 12 km. The episodes of 1999 and 2000 were reported as similar to the 1997 swarm. A previous analysis of the 2006 swarm concludes that the depth of seismicity migrates from 9 to 5 km and was originated by a magmatic intrusion. We did a relocation of this swarm reading all the events and using Hypo71 and the P-wave velocity model used by the Jalisco Seismic and Acelerometric Network; a waveform analysis using cross-correlation method was also carried out. We obtained 15 earthquakes families with a correlation factor equal or greater than 0.79 and composed focal mechanism for each family. These families present a migration in depth beginning at 16 km and ended at 9 km. Our results agrees with a magmatic intrusion, but not so shallow as the previous study of the 2006 swarm.

  16. A seismic survey of the Manson disturbed area

    NASA Technical Reports Server (NTRS)

    Sendlein, L. V. A.; Smith, T. A.

    1971-01-01

    The region in north-central Iowa referred to as the Manson disturbed area was investigated with the seismic refraction method and the bedrock configuration mapped. The area is approximately 30 km in diameter and is not detectable from the surface topography; however, water wells that penetrate the bedrock indicate that the bedrock is composed of disturbed Cretaceous sediments with a central region approximately 6 km in diameter composed of Precambrian crystalline rock. Seismic velocity differences between the overlying glacial till and the Cretaceous sediments were so small that a statistical program was developed to analyze the data. The program developed utilizes existing 2 segment regression analyses and extends the method to fit 3 or more regression lines to seismic data.

  17. Study of Local Seismic Events in Lithuania and Adjacent Areas Using Data from the PASSEQ Experiment

    NASA Astrophysics Data System (ADS)

    Janutyte, Ilma; Kozlovskaya, Elena; Motuza, Gediminas

    2013-05-01

    The territory of Lithuania and adjacent areas of the East European Craton have always been considered a region of low seismicity. Two recent earthquakes with magnitudes of more than 5 in the Kaliningrad District (Russian Federation) on 21 September 2004 motivated re-evaluation of the seismic hazard in Lithuania and adjacent territories. A new opportunity to study seismicity in the region is provided by the PASSEQ (Pasive Seismic Experiment) project that aimed to study the lithosphere-asthenosphere structure around the Trans-European Suture Zone. Twenty-six seismic stations of the PASSEQ temporary seismic array were installed in the territory of Lithuania. The stations recorded a number of local and regional seismic events originating from Lithuania and adjacent areas. This data can be used to answer the question of whether there exist seismically active tectonic zones in Lithuania that could be potentially hazardous for critical industrial facilities. Therefore, the aim of this paper is to find any natural tectonic seismic events in Lithuania and to obtain more general view of seismicity in the region. In order to do this, we make a manual review of the continuous data recorded by the PASSEQ seismic stations in Lithuania. From the good quality data, we select and relocate 45 local seismic events using the well-known LocSAT and VELEST location algortithms. In order to discriminate between possible natural events, underwater explosions and on-shore blasts, we analyse spatial distribution of epicenters and temporal distribution of origin times and perform both visual analysis of waveforms and spectral analysis of recordings. We show that the relocated seismic events can be grouped into five clusters (groups) according to their epicenter coordinates and origin and that several seismic events might be of tectonic origin. We also show that several events from the off-shore region in the Baltic Sea (at the coasts of the Kaliningrad District of the Russian Federation) are

  18. Seismic assessment of Technical Area V (TA-V).

    SciTech Connect

    Medrano, Carlos S.

    2014-03-01

    The Technical Area V (TA-V) Seismic Assessment Report was commissioned as part of Sandia National Laboratories (SNL) Self Assessment Requirement per DOE O 414.1, Quality Assurance, for seismic impact on existing facilities at Technical Area-V (TA-V). SNL TA-V facilities are located on an existing Uniform Building Code (UBC) Seismic Zone IIB Site within the physical boundary of the Kirtland Air Force Base (KAFB). The document delineates a summary of the existing facilities with their safetysignificant structure, system and components, identifies DOE Guidance, conceptual framework, past assessments and the present Geological and Seismic conditions. Building upon the past information and the evolution of the new seismic design criteria, the document discusses the potential impact of the new standards and provides recommendations based upon the current International Building Code (IBC) per DOE O 420.1B, Facility Safety and DOE G 420.1-2, Guide for the Mitigation of Natural Phenomena Hazards for DOE Nuclear Facilities and Non-Nuclear Facilities.

  19. Reflection seismic imaging in the volcanic area of the geothermal field Wayang Windu, Indonesia

    NASA Astrophysics Data System (ADS)

    Polom, Ulrich; Wiyono, Wiyono; Pramono, Bambang; Krawczyk, CharLotte M.

    2014-05-01

    Reflection seismic exploration in volcanic areas is still a scientific challenge and requires major efforts to develop imaging workflows capable of an economic utilization, e.g., for geothermal exploration. The SESaR (Seismic Exploration and Safety Risk study for decentral geothermal plants in Indonesia) project therefore tackles still not well resolved issues concerning wave propagation or energy absorption in areas covered by pyroclastic sediments using both active P-wave and S-wave seismics. Site-specific exploration procedures were tested in different tectonic and lithological regimes to compare imaging conditions. Based on the results of a small-scale, active seismic pre-site survey in the area of the Wayang Windu geothermal field in November 2012, an additional medium-scale active seismic experiment using P-waves was carried out in August 2013. The latter experiment was designed to investigate local changes of seismic subsurface response, to expand the knowledge about capabilities of the vibroseis method for seismic surveying in regions covered by pyroclastic material, and to achieve higher depth penetration. Thus, for the first time in the Wayang Windu geothermal area, a powerful, hydraulically driven seismic mini-vibrator device of 27 kN peak force (LIAG's mini-vibrator MHV2.7) was used as seismic source instead of the weaker hammer blow applied in former field surveys. Aiming at acquiring parameter test and production data southeast of the Wayang Windu geothermal power plant, a 48-channel GEODE recording instrument of the Badan Geologi was used in a high-resolution configuration, with receiver group intervals of 5 m and source intervals of 10 m. Thereby, the LIAG field crew, Star Energy, GFZ Potsdam, and ITB Bandung acquired a nearly 600 m long profile. In general, we observe the successful applicability of the vibroseis method for such a difficult seismic acquisition environment. Taking into account the local conditions at Wayang Windu, the method is

  20. Variation of the Earth tide-seismicity compliance parameter the last 50 years for the seismic area of Evoikos, Greece

    NASA Astrophysics Data System (ADS)

    Contadakis, Michael E.; Arabelos, Demetrious N.; Vergos, George; Spatalas, Spyrous

    2015-04-01

    The results of the analysis of the last 50 years earthquakes series in seismic active areas of Greece, i.e. the areas (a) of the Mygdonian Basin(Contadakis et al. 2007), (b) of the Ionian Islands (Contadakis et al. 2012 ) and (c) of the Hellenic Arc (Vergos et al. 2012 ), indicate that the monthly variation of the frequencies of earthquake occurrence is in accordance with the period of the tidal lunar monthly and semi-monthly (Mm and Mf) variations. The same happens with the corresponding daily variations of the frequencies of earthquake occurrence with the diurnal luni-solar (K1, O1) and semidiurnal lunar (M2) and solar (S2) tidal variations. In addition the confidence level for the identification of such period accordance between earthquakes occurrence frequency and tidal periods varies with seismic activity, i.e. the higher confidence level corresponds to periods with stronger seismic activity. These results are in favor of a tidal triggering process on earthquakes when the stress in the focal area is near the critical level. Based on these results, we consider the confidence level of earthquake frequency of occurrence - tidal period accordance, p, as an index of tectonic stress criticality for earthquake occurrence. A test on posterior of this idea, (i.e. the value of the confidence level index, p, indicate the fault matureness) in the case of the recent seismic activity at Fthiotida, was positive (Contadakis et al 2014). In this paper we present the results of a second test by the occasion of the recent seismic activity of Central Evoikos. The results also are positive. We suggest that this compliance parameter may be used as an additional element for the seismic risk assessment. References Cadicheanu, N., van Ruymbeke, M and Zhu P.,2007:Tidal triggering evidence of intermediate depth earthquakes in Vrancea zone(Romania), NHESS 7,733-740. Contadakis, M. E., Arabelos, D. N., Spatalas, S., 2009, Evidence for tidal triggering on the shallow earthquakes of the

  1. Initial Seismic Characterization of a Fault Controlled Hydrothermal Area

    NASA Astrophysics Data System (ADS)

    Bradford, J.; Lyle, M.; Clement, B.; Liberty, L.; Myers, R.; Paul, C.

    2002-12-01

    As part of an interdisciplinary project that aims to study the link between the physical characteristics of hydrothermal systems and the biota that occupy those systems, we have begun a detailed geophysical characterization of the Borax Lake hydrothermal area located near the center of Alvord Valley in the basin and range province of southeast Oregon. Basement rock is comprised of Miocene volcanic deposits overlain by up to 700 m of unconsolidated alluvium. Previous workers, based on gravity data and surface mapping, suggest that the Borax Lake hydrothermal area lies directly over a north/south trending fault. We are conducting seismic investigations on both a basin scale, to place the hydrothermal system in a larger geologic context, and a local high resolution scale for detailed imaging of fault architecture and hydrothermal flow paths. In this initial investigation, our primary objectives are to verify that a fault zone is present beneath the Borax Lake hot springs and to conduct tests to constrain acquisition parameters for detailed 3D seismic investigation. Initial seismic source tests indicate that the area is well suited to high resolution seismic investigation with clear reflections as deep as 300 ms and frequency content up to 500 Hz. Walk-away gathers show that the fluid distribution near the hot springs is complex with sharp gradients in the piezometric surface. To test the fault zone interpretation, and begin to build a large scale image of basin geometry, we acquired a 3.5 km seismic reflection profile perpendicular to the suspected fault zone. The profile consists of 30-fold CMP data acquired using a trailer mounted, 400 lb accelerated weight drop. Reflections are evident to depths of at least 500 m. Additionally, we acquired parallel magnetic profiles to constrain interpretation of the seismic data. Evidence for faulting is clear with the seismic image showing a complex normal fault zone bounded to the west by a structural high. Refraction analysis

  2. Ionospheric Response Due to Seismic Activity

    NASA Astrophysics Data System (ADS)

    Sharma, Dinesh Kumar

    2016-07-01

    Signatures of the seismic activity in the ionospheric F2 region have been studied by analyzing the measurement of electron and ion temperatures during the occurrence of earthquake. The ionospheric electron and ion temperatures data recorded by the RPA payload aboard the Indian SROSS-C2 satellite during the period from January 1995 to December 2000 were used for the altitude range 430-630 km over Indian region. The normal day's electron and ion temperatures have been compared to the temperatures recorded during the seismic activity. The details of seismic events were obtained from USGS earthquake data information website. It has been found that the average electron temperature is enhanced during the occurrence of earthquakes by 1.2 to 1.5 times and this enhancement was for ion temperature ranging from 1.1to 1.3 times over the normal day's average temperatures. The above careful quantitative analysis of ionospheric electron and ion temperatures data shows the consistent enhancement in the ionospheric electron and ion temperatures. It is expected that the seismogenic vertical electrical field propagates up to the ionospheric heights and induces Joule heating that may cause the enhancement in ionospheric temperatures.

  3. The study of recent seismicity in the aftershock area of Neftegorsk earthquake using waveform cross correlation

    NASA Astrophysics Data System (ADS)

    Kitov, Ivan; Turuntaev, Sergey; Konovalov, Alexei; Stepnov, Andrey

    2016-04-01

    Unusually long duration of seismic activity (more than 20 years) was observed in the aftershock area of the 1995 Neftegorsk, Sakhalin, Russia catastrophic earthquake (Ms=7.6). To study the phenomena, we have processed seismic data from 130 events occurred within that area as measured between 2006 and 2015. In order to improve the accuracy of relative location and magnitude estimation of these events we have applied new techniques based on waveform cross correlation. We use 7 three-component (3-C) seismic stations which detected most of these events. Three-component waveform templates were prepared for these stations from those events which had signals with SNR>5 at vertical channels. The events with 3 and more templates are used as master-events for waveform cross correlation. Overall, the re-estimated location and magnitudes demonstrate higher precisions and are used for the statistical analysis and numerical modelling of seismo-tectonic regime within the studied zone.

  4. Slope Stability Analysis In Seismic Areas Of The Northern Apennines (Italy)

    SciTech Connect

    Lo Presti, D.; Fontana, T.; Marchetti, D.

    2008-07-08

    Several research works have been published on the slope stability in the northern Tuscany (central Italy) and particularly in the seismic areas of Garfagnana and Lunigiana (Lucca and Massa-Carrara districts), aimed at analysing the slope stability under static and dynamic conditions and mapping the landslide hazard. In addition, in situ and laboratory investigations are available for the study area, thanks to the activities undertaken by the Tuscany Seismic Survey. Based on such a huge information the co-seismic stability of few ideal slope profiles have been analysed by means of Limit equilibrium method LEM - (pseudo-static) and Newmark sliding block analysis (pseudo-dynamic). The analysis--results gave indications about the most appropriate seismic coefficient to be used in pseudo-static analysis after establishing allowable permanent displacement. Such indications are commented in the light of the Italian and European prescriptions for seismic stability analysis with pseudo-static approach. The stability conditions, obtained from the previous analyses, could be used to define microzonation criteria for the study area.

  5. Seismic active control by neural networks.

    SciTech Connect

    Tang, Y.

    1998-01-01

    A study on the application of artificial neural networks (ANNs) to activate structural control under seismic loads is carried out. The structure considered is a single-degree-of-freedom (SDF) system with an active bracing device. The control force is computed by a trained neural network. The feed-forward neural network architecture and an adaptive back-propagation training algorithm is used in the study. The neural net is trained to reproduce the function that represents the response-excitation relationship of the SDF system under seismic loads. The input-output training patterns are generated randomly. In the back-propagation training algorithm, the learning rate is determined by ensuring the decrease of the error function at each epoch. The computer program implemented is validated by solving the classification of the XOR problem. Then, the trained ANN is used to compute the control force according to the control strategy. If the control force exceeds the actuator's capacity limit, it is set equal to that limit. The concept of the control strategy employed herein is to apply the control force at every time step to cancel the system velocity induced at the preceding time step so that the gradual rhythmic buildup of the response is destroyed. The ground motions considered in the numerical example are the 1940 El Centro earthquake and the 1979 Imperial Valley earthquake in California. The system responses with and without the control are calculated and compared. The feasibility and potential of applying ANNs to seismic active control is asserted by the promising results obtained from the numerical examples studied.

  6. Seismic active control by neutral networks

    SciTech Connect

    Tang, Yu

    1995-12-31

    A study on the application of artificial neural networks (ANNs) to active structural control under seismic loads is carried out. The structure considered is a single-degree-of-freedom (SDF) system with an active bracing device. The control force is computed by a trained neural network. The feedforward neural network architecture and an adaptive backpropagation training algorithm is used in the study. The neural net is trained to reproduce the function that represents the response-excitation relationship of the SDF system under seismic loads. The input-output training patterns are generated randomly. In the backpropagation training algorithm, the learning rate is determined by ensuring the decrease of the error function at each epoch. The computer program implemented is validated by solving the classification of the XOR problem. Then, the trained ANN is used to compute the control force according to the control strategy. If the control force exceeds the actuator`s capacity limit, it is set equal to that limit. The concept of the control strategy employed herein is to apply the control force at every time step to cancel the system velocity induced at the preceding time step so that the gradual rhythmic buildup of the response is destroyed. The ground motions considered in the numerical example are the 1940 El Centro earthquake and the 1979 Imperial Valley earthquake in California. The system responses with and without the control are calculated and compared. The feasibility and potential of applying ANNs to seismic active control is asserted by the promising results obtained from the numerical examples studied.

  7. The seismicity of Ethiopia; active plate tectonics

    USGS Publications Warehouse

    Mohr, P.

    1981-01-01

    Ethiopia, descended from the semimythical Kingdom of Punt, lies at the strategic intersection of Schmidt's jigsaw puzzle where the Red Sea, Gulf of Aden, and the African Rift System meet. Because of geologically recent uplift combined with rapid downcutting erosion by rivers, notably the Blue Nile (Abbay), Ethiopia is the most mountainous country in Africa. It is also the most volcanically active, while its historical seismicity matches that of the midocean ridges. And, in a sense, Ethiopia is host to an evoloving ocean ridge system. 

  8. Time-dependent seismic tomography of the Coso geothermal area, 1996-2004

    USGS Publications Warehouse

    Julian, B.R.; Foulger, G.R.

    2005-01-01

    The permanent 18-station network of three-component digital seismometers at the seismically active Coso geothermal area, California, provides high-quality microearthquake (MEQ) data that are well suited to investigating temporal variations in structure related to processes within the geothermal reservoir. A preliminary study [Julian, et al., 2003; Julian, et al., 2004] comparing data from 1996 and 2003 found significant variations in the ratio of the seismic wave-speeds, Vp/Vs, at shallow depths over this time interval. This report describes results of a more detailed study of each year from 1996 through 2004.

  9. Seasonal variations of seismic velocities in the San Jacinto fault area observed with ambient seismic noise

    NASA Astrophysics Data System (ADS)

    Hillers, G.; Ben-Zion, Y.; Campillo, M.; Zigone, D.

    2015-08-01

    We observe seasonal seismic wave speed changes (dv/v) in the San Jacinto fault area and investigate several likely source mechanisms. Velocity variations are obtained from analysis of 6 yr data of vertical component seismic noise recorded by 10 surface and six borehole stations. We study the interrelation between dv/v records, frequency-dependent seismic noise properties, and nearby environmental data of wind speed, rain, ground water level, barometric pressure and atmospheric temperature. The results indicate peak-to-peak seasonal velocity variations of ˜0.2 per cent in the 0.5-2 Hz frequency range, likely associated with genuine changes of rock properties rather than changes in the noise field. Phase measurements between dv/v and the various environmental data imply that the dominant source mechanism in the arid study area is thermoelastic strain induced by atmospheric temperature variations. The other considered environmental effects produce secondary variations that are superimposed on the thermal-based changes. More detailed work with longer data on the response of rocks to various known external loadings can help tracking the evolving stress and effective rheology at depth.

  10. A seismic hazard map of India and adjacent areas

    USGS Publications Warehouse

    Khattri, K.N.; Rogers, A.M.; Perkins, D.M.; Algermissen, S.T.

    1984-01-01

    We have produced a probabilistic seismic hazard map showing peak ground accelerations in rock for India and neighboring areas having a 10% probability of being exceeded in 50 years. Seismogenic zones were identified on the basis of historical seismicity, seismotectonics and geology of the region. Procedures for reducing the incompleteness of earthquake catalogs were followed before estimating recurrence parameters. An eastern United States acceleration attenuation relationship was employed after it was found that intensity attenuation for the Indian region and the eastern United States was similar. The largest probabilistic accelerations are obtained in the seismotectonic belts of Kirthar, Hindukush, Himalaya, Arakan-Yoma, and the Shillong massif where values of over 70% g have been calculated. ?? 1984.

  11. A comparison of active seismic source data to seismic excitations from the 2012 Tongariro volcanic eruptions, New Zealand

    NASA Astrophysics Data System (ADS)

    Jolly, Arthur; Kennedy, Ben; Keys, Harry; Lokmer, Ivan; Proctor, Jon; Lyons, John; Jolly, Gillian

    2014-05-01

    The 6 August 2012 eruption from Tongariro volcano's Te Maari vent comprised a complex sequence of events including at least 4 eruption jets, a large chasm collapse, and a debris avalanche (volume of ~7x105 m3) that propagated ~2 km beyond the eruptive vent. The eruption was poorly observed, being obscured by night time darkness, and the eruption chronology must be unravelled instead from a complex seismic record that includes discrete volcanic earthquakes, a sequence of low to moderate level spasmodic tremor and an intense burst of seismic and infrasound activity starting at 11:52:18 UTC that marked the eruption onset. We have discriminated the timing of the complex surface activity by comparing active seismic source data to the eruptive sequence. We dropped 11 high impact masses from helicopter to generate a range of active seismic sources in the vicinity of the eruption vent, chasm, and debris avalanche areas. We obtained 8 successful drops having an impact energy ranging from 3 to 9x106 joules producing seismic signals to a distance of 5 to 10 km and having good signal to noise characteristics in the 3-12 Hz range. For the 8 drops, we picked first-P arrival times and calculated amplitude spectra for a uniform set of four 3-component stations. From these, we obtained a distribution of amplitudes across the network for each drop position which varied systematically from the eruption vent and avalanche scar to the debris avalanche toe. We then compared these proxy source excitations to the natural eruption and pre-eruption data using a moving window cross-correlation approach. From the correlation processing, we found evidence for the debris avalanche a few minutes prior to the eruption in both the broad spectrum and narrow frequency (5-10 Hz) analysis. The total seismic energy release calculated from the new method is ~8x1011 joules, similar to an independently estimated calculation based on the radiated seismic energy. The inferred seismic energy release for the

  12. Structure and seismic activity of the Lesser Antilles subduction zone

    NASA Astrophysics Data System (ADS)

    Evain, M.; Galve, A.; Charvis, P.; Laigle, M.; Ruiz Fernandez, M.; Kopp, H.; Hirn, A.; Flueh, E. R.; Thales Scientific Party

    2011-12-01

    Several active and passive seismic experiments conducted in 2007 in the framework of the European program "Thales Was Right" and of the French ANR program "Subsismanti" provided a unique set of geophysical data highlighting the deep structure of the central part of the Lesser Antilles subduction zone, offshore Dominica and Martinique, and its seismic activity during a period of 8 months. The region is characterized by a relatively low rate of seismicity that is often attributed to the slow (2 cm/yr) subduction of the old, 90 My, Atlantic lithosphere beneath the Caribbean Plate. Based on tomographic inversion of wide-angle seismic data, the forearc can clearly be divided into an inner forearc, characterised by a high vertical velocity gradient in the igneous crust, and an outer forearc with lower crustal velocity gradient. The thick, high velocity, inner forearc is possibly the extension at depth of the Mesozoic Caribbean crust outcropping in La Désirade Island. The outer forearc, up to 70 km wide in the northern part of the study area, is getting narrower to the south and disappears offshore Martinique. Based on its seismic velocity structure with velocities higher than 6 km/s the backstop consists, at least partly, of magmatic rocks. The outer forearc is also highly deformed and faulted within the subducting trend of the Tiburon Ridge. With respect to the inner forearc velocity structure the outer forearc basement could either correspond to an accreted oceanic terrane or made of highly fractured rocks. The inner forearc is a dense, poorly deformable crustal block, tilted southward as a whole. It acts as a rigid buttress increasing the strain within both the overriding and subducting plates. This appears clearly in the current local seismicity affecting the subducting and the overriding plates that is located beneath the inner forearc. We detected earthquakes beneath the Caribbean forearc and in the Atlantic oceanic plate as well. The main seismic activity is

  13. Induced seismicity caused by hydraulic fracturing in deep geothermal wells in Germany and adjacent areas

    NASA Astrophysics Data System (ADS)

    Plenefisch, Thomas; Brückner, Lisa; Ceranna, Lars; Gestermann, Nicolai; Houben, Georg; Tischner, Torsten; Wegler, Ulrich; Wellbrink, Matthias; Bönnemann, Christian; Bertram, Andreas; Kirschbaum, Bernd

    2016-04-01

    Recently, the BGR has worked out a study on the potential environmental impact caused by hydraulic fracturing or chemical stimulations in deep geothermal reservoirs in Germany and adjacent areas. The investigations and analyses are based on existing studies and information provided by operators. The two environmental impacts being essentially considered in the report are induced seismicity and possible contamination of the groundwater reservoirs which serve for drinking water supply. Altogether, in this study, information on 30 hydraulic frac operations and 26 chemical stimulations including information from neighboring countries were compiled and analyzed. Out of the hydraulic stimulations two thirds were carried out as waterfracs and one third as fracturing with proppants. Parameters used in the study to characterize the induced seismicity are maximum magnitude, number of seismic events, size of the seismically active volume, and the relation of this volume to fault zones and the cap rock, as well as, finally, the impacts at the Earth's surface. The response of the subsurface to hydraulic fracturing is variable: There are some activities, which cause perceptible seismic events, others, where no perceptible but instrumentally detected events occurred, and moreover activities without even any instrumentally detected events. A classification of seismic hazard with respect to tectonic region, geology, or depth of the layer is still difficult, since the number of hydraulic fracturing measures in deep geothermal wells is small making a statistically sound analysis impossible. However, there are some indications, that hydraulic fracturing in granite in tectonically active regions like the Upper Rhine Graben results in comparatively stronger, perceptible seismicity compared to hydraulic fracturing in the sedimentary rocks of the North German basin. The maximum magnitudes of induced earthquakes caused by hydraulic fracturing of deep geothermal wells in Germany are

  14. Seismic image of a CO2 reservoir beneath a seismically active volcano

    USGS Publications Warehouse

    Julian, B.R.; Pitt, A.M.; Foulger, G.R.

    1998-01-01

    Mammoth Mountain is a seismically active volcano 200 000 to 50 000 years old, situated on the southwestern rim of Long Valley caldera, California. Since 1989 it has shown evidence of unrest in the form of earthquake swarms (Hill et al. 1990), volcanic 'long-period' earthquakes (Pitt and Hill 1994), increased output of magmatic 3He (Sorey et al. 1993) and the emission of about 500 tonnes day-1 of CO2 (Farrar et al. 1995; Hill 1996; M. Sorey, personal communication, 1997) which has killed trees and poses a threat to human safety. Local-earthquake tomography shows that in mid-1989 areas of subsequent tree-kill were underlain by extensive regions where the ratio of the compressional and shear elastic-wave speeds Vp/VS was about 9% lower than in the surrounding rocks. Theory (Mavko and Mukerji 1995), experiment (Ito, DeVilbiss and Nur 1979) and experience at other geothermal/volcanic areas (Julian et al. 1996) and at petroleum reservoirs (Harris et al. 1996) indicate that Vp/VS is sensitive to pore-fluid compressibility, through its effect on Vp. The observed Vp/VS anomaly is probably caused directly by CO2, and seismic Vp/VS tomography is thus a promising tool for monitoring gas concentration and movement in volcanoes, which may in turn be related to volcanic activity.

  15. Seismic image of a CO2 reservoir beneath a seismically active volcano

    NASA Astrophysics Data System (ADS)

    Julian, Bruce R; Pitt, A. M.; Foulger, G. R.

    1998-04-01

    Mammoth Mountain is a seismically active volcano 200000 to 50000 years old, situated on the southwestern rim of Long Valley caldera, California. Since 1989 it has shown evidence of unrest in the form of earthquake swarms (Hill et al. 1990), volcanic `long-period' earthquakes (Pitt & Hill 1994), increased output of magmatic 3He (Sorey et al. 1993) and the emission of about 500 tonnes day -1 of CO2 (Farrar et al. 1995; Hill 1996; M. Sorey, personal communication, 1997), which has killed trees and poses a threat to human safety. Local-earthquake tomography shows that in mid-1989 areas of subsequent tree-kill were underlain by extensive regions where the ratio of the compressional and shear elastic-wave speeds VP/VS was about 9 per cent lower than in the surrounding rocks. Theory (Mavko & Mukerji 1995), experiment (Ito, DeVilbiss & Nur 1979), and experience at other geothermal/volcanic areas (Julian et al. 1996) and at petroleum reservoirs (Harris et al. 1996) indicate that VP/VS is sensitive to pore-fluid compressibility, through its effect on VP . The observed VP/VS anomaly is probably caused directly by CO2, and seismic VP/VS tomography is thus a promising tool for monitoring gas concentration and movement in volcanoes, which may in turn be related to volcanic activity.

  16. Fault Activity, Seismicity and GPS Deformation of the Seismic Gap along the Red River Fault Zone (RRFZ) in Yunnan, China

    NASA Astrophysics Data System (ADS)

    Xue-Ze, Wen; Shengli, Ma; Fang, Du; Feng, Long

    2016-04-01

    Along the middle segment of the NW-trending and dextral-slip Red River fault zone (RRFZ), also the Honghe fault zone, Yunnan, China, there has been little of modern seismicity since the 1970's. Some Chinese researchers believed that this fault segment is inactive in the late Quaternary. However, more and more evidence shows that the middle segment of RRFZ is geologically-active in the late Quaternary, even is a Holocene-active one with evidence of paleo-earthquakes occurring. Our study suggests that along the fault segment there has been no any major earthquake occurring for over 500 years at least, and a large-scale seismic gap, the Honghe seismic gap, have formed there. On the modern seismicity, the middle segment of RRFZ has presented as a fault portion without or with very few small earthquakes occurring since the 1980's, but surrounded by several areas with low b-values, suggesting relatively high stress having built-up there. Also, GPS deformation analysis suggests that this fault segment has tightly locked already. Such tight locking would be associated with the fault geometry: A large-scale restraining bend of about 30°over a distance of ~100 km exists along the main fault trace along RRFZ between Yuanjiang and Yuanyang. However, how such a restraining bend makes the middle segment of RRFZ have tightly locked? How much strain has built up there? Moreover, how about the long-term seismic potential of major earthquake on the middle segment of RRFZ, and on some secondary active faults of the two sides of the segment, especially on the parallel faults Chuxiong, Qujiang and Shiping. All these are issues we want to study further. Keywords: Red River Fault Zone, Seismic Gap, Fault Activity, Seismicity, GPS Deformation

  17. Active seismic sources as a proxy for seismic surface processes: An example from the 2012 Tongariro volcanic eruptions, New Zealand

    NASA Astrophysics Data System (ADS)

    Jolly, A. D.; Lokmer, I.; Kennedy, B.; Keys, H. J. R.; Proctor, J.; Lyons, J. J.; Jolly, G. E.

    2014-10-01

    The 6 August 2012 eruption from Tongariro volcano's Te Maari vent comprised a complex sequence of events including at least 4 eruption pulses, a large chasm collapse, and a debris avalanche (volume of ~ 7 × 105 m3) that propagated ~ 2 km beyond the eruptive vent. The eruption was poorly observed, being obscured by night time darkness, and the eruption timing must be unravelled instead from a complex seismic record that includes discrete volcanic earthquakes, a sequence of low to moderate level spasmodic tremor and an intense burst of seismic and infrasound activity that marked the eruption onset. We have discriminated the evolution of the complex surface activity by comparing active seismic source data to the seismic sequence in a new cross correlation source location approach. We dropped 11 high impact masses from helicopter to generate a range of active seismic sources in the vicinity of the eruption vent, chasm, and debris avalanche areas. We obtained 8 successful drops having an impact energy ranging from 3 to 9 × 106 Nm producing observable seismic signals to a distance of 5 to 10 km and having good signal to noise characteristics in the 3-12 Hz range. For the 8 drops, we picked first-P arrival times and calculated amplitude spectra for a uniform set of four stations. We then compared these proxy source excitations to the natural eruption and pre-eruption data using a moving window cross correlation approach. From the correlation processing, we obtain a best matched source position in the near vent region for the eruption period and significant down channel excitations during both the pre and post eruption periods. The total seismic energy release calculated from the new method is ~ 8 × 1011 Nm, similar to an independently estimated calculation based on the radiated seismic energy. The new energy estimate may be more robust than those calculated from standard seismic radiation equations, which may include uncertainties about the path and site effects. The

  18. Geyser's Eruptive Activity in Broadband Seismic Records

    NASA Astrophysics Data System (ADS)

    Kugaenko, Yulia; Saltykov, Vadim

    2010-05-01

    A geyser is a spring characterized by intermittent discharge of water ejected turbulently and accompanied by a vapor phase (steam). The formation of geysers is due to particular hydrogeological conditions, which exist in only a few places on Earth, so they are a fairly rare phenomenon. The reasons of geyser periodicity and specifics of the activity for every particular geyser are not completely clear yet. So almost for all known geysers it is necessary to develop the personal model. In given study we first use seismic method for detection of possible hidden feature of geyser's eruptive activity in Kamchatkan Valley of the Geysers. Broadband seismic records of geyser generated signals were obtained in hydrothermal field. The Valley of the Geysers belongs to Kronotskiy State Natural Biosphere Reserve and the UNESCO World Natural Heritage Site "Volcanoes of Kamchatka". Neither seismological nor geophysical investigations were carried out here earlier. In September, 2009 seismic observation was organized in geyser's field by 24-bit digital output broadband seismometers (GURALP CMG-6TD flat velocity response 0.033-50 Hz). Four geysers were surveyed: the fountain type Big and Giant geysers; the cone type Pearl geyser and the short-period Gap geyser. Seismometers were set as possible close to the geyser's surface vent (usually at the distance near 3-5 m). Main parameters of the eruptions for the investigated geysers: - The Giant geyser is the most powerful among the regular active geysers in Kamchatkan Valley of the Geysers. The height of the fountain reaches 30 meters, the mass of water erupted is about 40-60 tons. The main cycle of activity varies significantly: in 1945 the intervals between eruptions was near 3 hours, nowadays it is 5-6 hours. As a geyser of fountain type, the Giant geyser erupts from the 2*3 m2 pool of water. - The Big geyser was flooded by the lake after the natural catastrophe (giant mud-stone avalanche, formed by landslide, bed into Geiyzernaya

  19. Prospectivity of Northern Barinas area through modern seismic data

    SciTech Connect

    Gil, E.; Rotundo, J.; Hernandez, L. )

    1993-02-01

    The area of study is located to north of the Merida arch, in the Barinas-Apure basin. The geologic section comprises early Cretaceous (Albiense) to Quaternary deposits. The Cretaceous sequence lies unconformably over the metamorphic basement; the lower section of Navay Formation, of Cretaceous age, is consider to be the source rock, and it is associated with maximum transgression (91.5 mma). In Barinas, this represent the lateral equivalent of La Luna Formation of the Maracaibo Lake. The Gobernador and Paguey Formations (later middle Eocene), overlie unconformably, the Cretaceous rocks. The lower section of the later formation is associated with maximum transgressive cycles as a result of the collision of the South American and Caribbean plates. Former interpretation of analogic seismic data showed small structures that were less evident towards the deeper part of the basin. Recently, Corpoven acquired 2350 km of excellent digital seismic data with a coverage of 3000%. This has allowed us to subdivide the area in three hydrocarbons prospective zones:(1) Northern Barinas Zone: Characterized by faults and structures very similar to other prospective fields of the area. (2) South Andean Slope: This was affected by the Andean orogenesis. In this zone we find the same sedimentary column, but the structures are bigger than the former producing. (3) Southern Guanate Zone: This zone shows light faulting and abundant acoustic anomalies probably associated to facies changes.

  20. Research on seismic survey design for doubly complex areas

    NASA Astrophysics Data System (ADS)

    Zhao, Hu; Yin, Cheng; Wu, Ming-Sheng; Wu, Xiao-Hua; Pan, Shu-Lin

    2012-06-01

    The complex geological conditions in doubly complex areas tend to result in difficult surface survey operations and poor target layer imaging in the subsurface which has a great impact on seismic data quality. In this paper, we propose an optimal crooked line survey method for decreasing the surface survey operational difficulties and improving the sub-layer event continuity. The method concentrates on the surface shooting conditions, first, selecting the proper shot positions based on the specific surface topographic features to reduce the shot difficulties and then optimizing the receiver positioning to meet the prerequisite that the subsurface reflection points remain in a straight line. Using this method cannot only lower the shooting difficulty of rough surface condition areas but also overcome the subsurface reflection point bending problem appearing in the traditional crooked line survey method. On the other hand, we use local infill shooting rather than conventional overall infill shooting to improve sublayer event continuity and uniformity with lower survey operation cost. A model has been calculated and processed with the proposed optimal crooked line survey and local infill shooting design method workflow and the results show that this new method can work for seismic surveys in double complex areas.

  1. RST (Robust Satellite Techniques) analysis for monitoring earth emitted radiation in seismically active area of California (US): a long term (2006-2011) analysis of GOES-W/IMAGER thermal data

    NASA Astrophysics Data System (ADS)

    Tramutoli, V.; Armandi, B.; Filizzola, C.; Genzano, N.; Lisi, M.; Paciello, R.; Pergola, N.

    2014-12-01

    More than ten years of applications of the RST (Robust Satellite Techniques) methodology for monitoring earthquake prone area by using satellite TIR(Thermal InfraRed) data, have shown the ability of this approach to discern anomalous TIR signals possibly associated to seismic activity from normal fluctuations of Earth's thermal emission related to other causes independent on the earthquake occurrence. The RST approach was already tested in the case of tens of earthquakes occurred in different continents (Europe, Asia, America and Africa), in various geo-tectonic settings (compressive, extensional and transcurrent) and with a wide range of magnitudes (from 4.0 to 7.9), by analyzing time series of TIR images acquired by sensors on board of polar (like NOAA/AVHRR, EOS/MODIS) and geostationary satellites (like MFG/MVIRI, MSG/SEVIRI, GOES/IMAGER). In addition RST method has been independently tested by several researchers around the world as well as in the framework of several projects funded by different national space agencies (like the Italian ASI, the U.S. NASA and the German DLR) and recently during the EC-FP7 projectPRE-EARTHQUAKES (www.pre-earthquakes.org),which was devoted to study the earthquake precursors using satellite techniques. This paper will show the results of RST analysis on 6 years (2006-2011)of TIR satellite record collected by GOES-W/IMAGER over Southern part United State (California).Results will be discussed particularly in the prospective of an integrated approach devoted to systematically collectand analyze in real-time, independent observations for a time-Dependent Assessment of Seismic Hazard (t-DASH).

  2. Issues Related to Seismic Activity Induced by the Injection of CO2 in Deep Saline Aquifers

    SciTech Connect

    Sminchak, Joel; Gupta, Neeraj; Byrer, Charles; Bergman, Perry

    2001-05-31

    Case studies, theory, regulation, and special considerations regarding the disposal of carbon dioxide (CO2) into deep saline aquifers were investigated to assess the potential for induced seismic activity. Formations capable of accepting large volumes of CO2 make deep well injection of CO2 an attractive option. While seismic implications must be considered for injection facilities, induced seismic activity may be prevented through proper siting, installation, operation, and monitoring. Instances of induced seismic activity have been documented at hazardous waste disposal wells, oil fields, and other sites. Induced seismic activity usually occurs along previously faulted rocks and may be investigated by analyzing the stress conditions at depth. Seismic events are unlikely to occur due to injection in porous rocks unless very high injection pressures cause hydraulic fracturing. Injection wells in the United States are regulated through the Underground Injection Control (UIC) program. UIC guidance requires an injection facility to perform extensive characterization, testing, and monitoring. Special considerations related to the properties of CO2 may have seismic ramifications to a deep well injection facility. Supercritical CO2 liquid is less dense than water and may cause density-driven stress conditions at depth or interact with formation water and rocks, causing a reduction in permeability and pressure buildup leading to seismic activity. Structural compatibility, historical seismic activity, cases of seismic activity triggered by deep well injection, and formation capacity were considered in evaluating the regional seismic suitability in the United States. Regions in the central, midwestern, and southeastern United States appear best suited for deep well injection. In Ohio, substantial deep well injection at a waste disposal facility has not caused seismic events in a seismically active area. Current

  3. SANITARY VULNERABILITY OF A TERRITORIAL SYSTEM IN HIGH SEISMIC AREAS

    NASA Astrophysics Data System (ADS)

    Teramo, A.; Termini, D.; de Domenico, D.; Marino, A.; Marullo, A.; Saccà, C.; Teramo, M.

    2009-12-01

    An evaluation procedure of sanitary vulnerability of a territorial system falling within a high seismic risk area, related to casualty treatment capability of hospitals after an earthquake, is proposed. The goal of the study is aimed at highlighting hospital criticalities for the arrangement of a prevention policy on the basis of territorial, demographic and sanitary type specific analyses of a given area. This is the first step of a procedure of territorial context reading within a damage scenario, addressed to a verification of preparedness level of the territorial system to a sanitary emergency referable both to a natural disaster and anthropic one. The results of carried out surveys are shown, at a different scale, on several sample areas of Messina Province (Italy) territory, evaluating the consistency of damage scenario with the number of casualties, medical doctors, available beds for the implementation of a emergency sanitary circuit.

  4. Seismic Noise Studies of Urbanized Areas at Puerto Vallarta Mexico

    NASA Astrophysics Data System (ADS)

    Lara Huerta, K. C.; Escudero, C. R.; Gomez, A.; Madrigal, L.

    2014-12-01

    The application of seismic noise techniques in urbanized environment becomes a valuable tool to obtain information that is critical in areas exposed to earthquakes. Damage distribution during large earthquakes is frequently conditioned by site effects, in this way we determine site effect using ambient noise measurements in the area of Puerto Vallarta, Mexico. We focus our microtremor measurements to the estimation of a subsoil structure. To perform this we use three different techniques H/V spectral ratios, array measurements of microtremors applying the SPAC and F-k techniques. This work discusses the results that were obtained applying these techniques to the urbanized areas of Puerto Vallarta city. We present a series of maps showing the result as well as analyzed its application to risk assessment.

  5. The tectonic puzzle of the Messina area (Southern Italy): Insights from new seismic reflection data

    PubMed Central

    Doglioni, Carlo; Ligi, Marco; Scrocca, Davide; Bigi, Sabina; Bortoluzzi, Giovanni; Carminati, Eugenio; Cuffaro, Marco; D'Oriano, Filippo; Forleo, Vittoria; Muccini, Filippo; Riguzzi, Federica

    2012-01-01

    The Messina Strait, that separates peninsular Italy from Sicily, is one of the most seismically active areas of the Mediterranean. The structure and seismotectonic setting of the region are poorly understood, although the area is highly populated and important infrastructures are planned there. New seismic reflection data have identified a number of faults, as well as a crustal scale NE-trending anticline few km north of the strait. These features are interpreted as due to active right-lateral transpression along the north-eastern Sicilian offshore, coexisting with extensional and right-lateral transtensional tectonics in the southern Messina Strait. This complex tectonic network appears to be controlled by independent and overlapping tectonic settings, due to the presence of a diffuse transfer zone between the SE-ward retreating Calabria subduction zone relative to slab advance in the western Sicilian side. PMID:23240075

  6. The tectonic puzzle of the Messina area (Southern Italy): insights from new seismic reflection data.

    PubMed

    Doglioni, Carlo; Ligi, Marco; Scrocca, Davide; Bigi, Sabina; Bortoluzzi, Giovanni; Carminati, Eugenio; Cuffaro, Marco; D'Oriano, Filippo; Forleo, Vittoria; Muccini, Filippo; Riguzzi, Federica

    2012-01-01

    The Messina Strait, that separates peninsular Italy from Sicily, is one of the most seismically active areas of the Mediterranean. The structure and seismotectonic setting of the region are poorly understood, although the area is highly populated and important infrastructures are planned there. New seismic reflection data have identified a number of faults, as well as a crustal scale NE-trending anticline few km north of the strait. These features are interpreted as due to active right-lateral transpression along the north-eastern Sicilian offshore, coexisting with extensional and right-lateral transtensional tectonics in the southern Messina Strait. This complex tectonic network appears to be controlled by independent and overlapping tectonic settings, due to the presence of a diffuse transfer zone between the SE-ward retreating Calabria subduction zone relative to slab advance in the western Sicilian side. PMID:23240075

  7. Seismic activity noted at Medicine Lake Highlands

    SciTech Connect

    Blum, D.

    1988-12-01

    The sudden rumble of earthquakes beneath Medicine Lake Highlands this fall gave geologists an early warning that one of Northern California's volcanoes may be stirring back to life. Researchers stressed that an eruption of the volcano is not expected soon. But the flurry of underground shocks in late September, combined with new evidence of a pool of molten rock beneath the big volcano, has led them to monitor Medicine Lake with new wariness. The volcano has been dormant since 1910, when it ejected a brief flurry of ash - worrying no one. A federal team plans to take measurements of Medicine Lake, testing for changes in its shape caused by underground pressures. The work is scheduled for spring because snows have made the volcano inaccessible. But the new seismic network is an effective lookout, sensitive to very small increases in activity.

  8. Erosion influences the seismicity of active thrust faults.

    PubMed

    Steer, Philippe; Simoes, Martine; Cattin, Rodolphe; Shyu, J Bruce H

    2014-01-01

    Assessing seismic hazards remains one of the most challenging scientific issues in Earth sciences. Deep tectonic processes are classically considered as the only persistent mechanism driving the stress loading of active faults over a seismic cycle. Here we show via a mechanical model that erosion also significantly influences the stress loading of thrust faults at the timescale of a seismic cycle. Indeed, erosion rates of about ~0.1-20 mm yr(-1), as documented in Taiwan and in other active compressional orogens, can raise the Coulomb stress by ~0.1-10 bar on the nearby thrust faults over the inter-seismic phase. Mass transfers induced by surface processes in general, during continuous or short-lived and intense events, represent a prominent mechanism for inter-seismic stress loading of faults near the surface. Such stresses are probably sufficient to trigger shallow seismicity or promote the rupture of deep continental earthquakes up to the surface. PMID:25412707

  9. Searching for Seismically Active Faults in the Gulf of Cadiz

    NASA Astrophysics Data System (ADS)

    Custodio, S.; Antunes, V.; Arroucau, P.

    2015-12-01

    The repeated occurrence of large magnitude earthquakes in southwest Iberia in historical and instrumental times suggests the presence of active fault segments in the region. However, due to an apparently diffuse seismicity pattern defining a broad region of distributed deformation west of Gibraltar Strait, the question of the location, dimension and geometry of such structures is still open to debate. We recently developed a new algorithm for earthquake location in 3D complex media with laterally varying interface depths, which allowed us to relocate 2363 events having occurred from 2007 to 2013, using P- and S-wave catalog arrival times obtained from the Portuguese Meteorological Institute (IPMA, Instituto Portugues do Mar e da Atmosfera), for a study area lying between 8.5˚W and 5˚W in longitude and 36˚ and 37.5˚ in latitude. The most remarkable change in the seismicity pattern after relocation is an apparent concentration of events, in the North of the Gulf of Cadiz, along a low angle northward-dipping plane rooted at the base of the crust, which could indicate the presence of a major fault. If confirmed, this would be the first structure clearly illuminated by seismicity in a region that has unleashed large magnitude earthquakes. Here, we present results from the joint analysis of focal mechanism solutions and waveform similarity between neighboring events from waveform cross-correlation in order to assess whether those earthquakes occur on the same fault plane.

  10. Seismic response in archaeological areas: the case-histories of Rome

    NASA Astrophysics Data System (ADS)

    Donati, Stefano; Funiciello, Renato; Rovelli, Antonio

    1999-03-01

    Rome is affected by earthquakes associated to three different seismogenic districts: the Central Apennines area, the Colli Albani volcanic area and the Roman area. The major effects were exclusively due to Apennine seismicity and reached in some cases felt intensities up to VII-VIII degree (MCS scale). The predominant role in the damage distribution seems to be played by the local geological conditions. The historical centre of the city is characterized by the presence of two geomorphologic domains: the alluvial plain of Tiber river and the topographic relieves of Roman Hills, where tradition indicates the first site of the city foundation. In particular, the right river side is characterized by the outcropping of the regional bedrock along the Monte Mario-Gianicolo ridge, while the eastern relieves are the remnants of the Sabatini and Albani volcanic plateau, deeply eroded by the Tiber river and its tributaries during the last glacial low-stand (Würm). These domains are characterized by a large difference in seismic response, due to the high impedance contrast between Holocene coarse deposits filling the Tiber Valley and sedimentary and volcanic Plio-Pleistocene units. Seismic damage observed in 150 monuments of downtown Rome was indicating a significant concentration on alluvial recent deposits. This result was confirmed by the geographical distribution of conservation and retrofitting activities subsequent to main earthquakes, mostly related to local geological conditions. The cases of Marcus Aurelius' Column and Colosseum confirmed the influence of the Holocene alluvial network in local seismic response. During 2500 years of history, the monuments of Rome have `memorized' the seismic effects of historical earthquakes. In some cases, the integration of historical and geological research and macroseismic observations may provide original and useful indications to seismologists to define the seismic response of the city. Local site effects represent a serious

  11. Calcium Stabilized And Geogrid Reinforced Soil Structures In Seismic Areas

    SciTech Connect

    Rimoldi, Pietro; Intra, Edoardo

    2008-07-08

    In many areas of Italy, and particularly in high seismic areas, there is no or very little availability of granular soils: hence embankments and retaining structures are often built using the locally available fine soil. For improving the geotechnical characteristics of such soils and/or for building steep faced structures, there are three possible techniques: calcium stabilization, geogrid reinforcement, and the combination of both ones, that is calcium stabilized and reinforced soil. The present paper aims to evaluate these three techniques in terms of performance, design and construction, by carrying out FEM modeling and stability analyses of the same reference embankments, made up of soil improved with each one of the three techniques, both in static and dynamic conditions. Finally two case histories are illustrated, showing the practical application of the above outlined techniques.

  12. Boundary separating the seismically active reelfoot rift from the sparsely seismic Rough Creek graben, Kentucky and Illinois

    USGS Publications Warehouse

    Wheeler, R.L.

    1997-01-01

    The Reelfoot rift is the most active of six Iapetan rifts and grabens in central and eastern North America. In contrast, the Rough Creek graben is one of the least active, being seismically indistinguishable from the central craton of North America. Yet the rift and graben adjoin. Hazard assessment in the rift and graben would be aided by identification of a boundary between them. Changes in the strikes of single large faults, the location of a Cambrian transfer zone, and the geographic extent of alkaline igneous rocks provide three independent estimates of the location of a structural boundary between the rift and the graben. The boundary trends north-northwest through the northeastern part of the Fluorspar Area Fault Complex of Kentucky and Illinois, and has no obvious surface expression. The boundary involves the largest faults, which are the most likely to penetrate to hypocentral depths, and the boundary coincides with the geographic change from abundant seismicity in the rift to sparse seismicity in the graben. Because the structural boundary was defined by geologic variables that are expected to be causally associated with seismicity, it may continue to bound the Reelfoot rift seismicity in the future.

  13. Multi-channel Linear Array Seismic Interferometry: Insights on Passive Seismic Imaging of the Upper 1 km in an Urban Area

    NASA Astrophysics Data System (ADS)

    Pettinger, E. M.; Stephenson, W. J.; Odum, J. K.

    2015-12-01

    High-resolution active-source seismic imaging in heavily urbanized regions is problematic because equipment deployment is often constrained to linear roadways, where access for active seismic sources may be limited and seismic energy from ambient urban noise can overpower active sources. To investigate the application of linear-array seismic interferometry for obtaining subsurface images in the upper 1 km beneath an urban area, we acquired passive seismic data along two roadways that cross a northern segment of the Seattle fault zone, Washington State. Both of the profiles were collocated with previously acquired active-source reflection lines, which we used as control for interpretations. The interferometry profiles were roughly 1 km in length and were acquired using 8-Hz resonant frequency, vertical-component geophones that were deployed at 5 m spacing (nominally 216 sensors). Approximately 24 hours of data were acquired on each profile over four days (because of permitting and security issues, the equipment could not be deployed overnight). The basic processing sequence used to create virtual source gathers (VSG's) included pre-correlation gain correction, resampling, bandpass filtering, correlation by cross coherence, and VSG editing. After editing, around 18% of the individual virtual sources were retained for further analysis. VSG's were then dip filtered prior to stacking to further mitigate coherent noise. Our VSG's resolve 4-30 Hz Rayleigh waves, propagating at 300-600 m/s, and at least one diving P-wave propagating at roughly 1800 m/s. These apparent velocities are similar to those of comparable wave phases observed in the active-source data. Overall, these newly acquired high-resolution seismic imaging data provide insights into seismic velocity of the upper 1 km across the Seattle fault zone.

  14. The Lusi seismic experiment: An initial study to understand the effect of seismic activity to Lusi

    NASA Astrophysics Data System (ADS)

    Karyono, Mazzini, Adriano; Lupi, Matteo; Syafri, Ildrem; Masturyono, Rudiyanto, Ariska; Pranata, Bayu; Muzli, Widodo, Handi Sulistyo; Sudrajat, Ajat; Sugiharto, Anton

    2015-04-01

    The spectacular Lumpur Sidoarjo (Lusi) eruption started in northeast Java on the 29 of May 2006 following a M6.3 earthquake striking the island [1,2]. Initially, several gas and mud eruption sites appeared along the reactivated strike-slip Watukosek fault system [3] and within weeks several villages were submerged by boiling mud. The most prominent eruption site was named Lusi. The Lusi seismic experiment is a project aims to begin a detailed study of seismicity around the Lusi area. In this initial phase we deploy 30 seismometers strategically distributed in the area around Lusi and along the Watukosek fault zone that stretches between Lusi and the Arjuno Welirang (AW) complex. The purpose of the initial monitoring is to conduct a preliminary seismic campaign aiming to identify the occurrence and the location of local seismic events in east Java particularly beneath Lusi.This network will locate small event that may not be captured by the existing BMKG network. It will be crucial to design the second phase of the seismic experiment that will consist of a local earthquake tomography of the Lusi-AW region and spatial and temporal variations of vp/vs ratios. The goal of this study is to understand how the seismicity occurring along the Sunda subduction zone affects to the behavior of the Lusi eruption. Our study will also provide a large dataset for a qualitative analysis of earthquake triggering studies, earthquake-volcano and earthquake-earthquake interactions. In this study, we will extract Green's functions from ambient seismic noise data in order to image the shallow subsurface structure beneath LUSI area. The waveform cross-correlation technique will be apply to all of recordings of ambient seismic noise at 30 seismographic stations around the LUSI area. We use the dispersive behaviour of the retrieved Rayleigh waves to infer velocity structures in the shallow subsurface.

  15. The Lusi seismic experiment: An initial study to understand the effect of seismic activity to Lusi

    SciTech Connect

    Karyono; Mazzini, Adriano; Sugiharto, Anton; Lupi, Matteo; Syafri, Ildrem; Masturyono,; Rudiyanto, Ariska; Pranata, Bayu; Muzli,; Widodo, Handi Sulistyo; Sudrajat, Ajat

    2015-04-24

    The spectacular Lumpur Sidoarjo (Lusi) eruption started in northeast Java on the 29 of May 2006 following a M6.3 earthquake striking the island [1,2]. Initially, several gas and mud eruption sites appeared along the reactivated strike-slip Watukosek fault system [3] and within weeks several villages were submerged by boiling mud. The most prominent eruption site was named Lusi. The Lusi seismic experiment is a project aims to begin a detailed study of seismicity around the Lusi area. In this initial phase we deploy 30 seismometers strategically distributed in the area around Lusi and along the Watukosek fault zone that stretches between Lusi and the Arjuno Welirang (AW) complex. The purpose of the initial monitoring is to conduct a preliminary seismic campaign aiming to identify the occurrence and the location of local seismic events in east Java particularly beneath Lusi.This network will locate small event that may not be captured by the existing BMKG network. It will be crucial to design the second phase of the seismic experiment that will consist of a local earthquake tomography of the Lusi-AW region and spatial and temporal variations of vp/vs ratios. The goal of this study is to understand how the seismicity occurring along the Sunda subduction zone affects to the behavior of the Lusi eruption. Our study will also provide a large dataset for a qualitative analysis of earthquake triggering studies, earthquake-volcano and earthquake-earthquake interactions. In this study, we will extract Green’s functions from ambient seismic noise data in order to image the shallow subsurface structure beneath LUSI area. The waveform cross-correlation technique will be apply to all of recordings of ambient seismic noise at 30 seismographic stations around the LUSI area. We use the dispersive behaviour of the retrieved Rayleigh waves to infer velocity structures in the shallow subsurface.

  16. Coexistence of thin- and thick-skinned tectonics in Zakynthos area (western Greece): Insights from seismic sections and regional seismicity

    NASA Astrophysics Data System (ADS)

    Kokkalas, S.; Kamberis, E.; Xypolias, P.; Sotiropoulos, S.; Koukouvelas, I.

    2013-06-01

    The structural style of the fold-and-thrust belt in the western part of the Hellenic foreland in an area offshore the Zakynthos Island is assessed on the basis of two lithoseismic profiles, earthquake data and field data in the broader area. The compressional deformation in the area is due to the late phases of subduction and collision between Aegean and African plates. Shortening is affecting a ~ 6-7 km thick sedimentary succession of Mesozoic carbonate rocks and evaporites, as well as Miocene to Pleistocene foredeep clastic deposits. Structures accommodating shortening in the Pre-Apulian and Ionian zones comprise a blind imbricate thrust system and fault-propagation folds that formed over a 10-11 km deep detachment. The thrust system comprises an array of forward-verging thrust faults, which sole out in a low-angle hinterland dipping décollement, separating the Mesozoic cover from the pre-Mesozoic basement. In this tectonic context, the Triassic evaporitic layers seem to play an important role in the vertical partitioning of the deformation style acting as either detachment horizons or lining the imbricate thrust surfaces. The concentration of recent seismic activity at a depth between 6 and 16 km implies that the pre-Mesozoic basement is also involved in the deformation in the form of upthrust basement slices, suggesting a combination of thick and thin-skinned deformation across this domain of the External Hellenides fold-and-thrust belt. The frontal part of the belt shows higher seismic activity along a low-angle blind thrust, as well as also in the areas where the individual thrust planes branch at depth to the basal décollement.

  17. Geospatial and In-Situ Monitoring Data for Seismic Hazard Assessment in Vrancea Area, Romania

    NASA Astrophysics Data System (ADS)

    Zoran, Maria

    Seismic hazard for almost half of the Romanian territory is determined by the Vrancea ac-tive seismic region, placed beneath the southern Carpathian Arc in Romania at conjunction of four tectonic blocks, which lie on the edge of the Eurasian plate. Vrancea zone is considered one of the most seismically active area in Europe, being characterized by strong intermediate depth seismicity in a very limited and well defined hypocentral region.Space-time anomalies of Earth's emitted radiation (radon in underground water and soil , thermal infrared in spec-tral range measured from satellite months to weeks before the occurrence of earthquakes etc.), ionospheric and electromagnetic anomalies have been interpreted, by several authors, as pre-seismic signals.Satellite remote sensing provides a systematic, synoptic framework for advancing scientific knowledge of the Earth complex system of geophysical phenomena which often lead to seismic hazards. Space-based geodetic measurements of the solid Earth with the Global Positioning System, combined with ground-based seismological measurements and satellite re-mote sensing information are yielding the principal data for modeling lithospheric processes and for accurately estimating the distribution of potentially damaging strong ground motions which is critical for earthquake engineering applications. Moreover, integrated with interfero-metric synthetic aperture radar, these measurements provide spatially continuous observations of deformation with sub-centimeter accuracy. Seismic and in situ monitoring, geodetic mea-surements, high-resolution digital elevation models (e.g. from InSAR, IKONOS and digital photogrammetry) and imaging spectroscopy (e.g. using ASTER, MODIS and Hyperion) are contributing significantly to seismic hazard risk assessment by revealing new insights in the understanding of the kinematics and dynamics of the complex plate boundary system and long-term deformation in relation with earthquake activity. Several

  18. Study of seismicity around Toba area based on relocation hypocenter result from BMKG catalogue

    SciTech Connect

    Ramdhan, Mohamad; Nugraha, Andri Dian

    2013-09-09

    Toba area has complex tectonic setting attracting many earth scientists to study and understand tectonic and geological process or setting. The area is affected by oblique subduction zone, Renun Sumatran fault sub segment and some volcanoes that are near it. The earthquake catalogue provided by BMKG from April, 2009 to December, 2011 must be relocated firstly to get the precise hypocenter. We used catalogue data of P and S phase or P phase only and double-difference method to relocate the earthquakes. The results show hypocenter position enhancement that can be interpreted tectonically. The earthquakes after relocation relating to the Sumatran fault, subduction zone, volcanoes and seismic activities beneath Toba caldera can be mapped clearly. The relocated hypocenters in this study are very important to provide information for seismic hazard assessment and disaster mitigation study.

  19. Seismicity study in Pournari reservoir area (W. Greece) 1981-2010

    NASA Astrophysics Data System (ADS)

    Pavlou, K.; Drakatos, G.; Kouskouna, V.; Makropoulos, K.; Kranis, H.

    2016-04-01

    The spatial-temporal evolution of seismicity is examined, during the initial impoundment of Pournari reservoir located on Arachthos River (Western Greece), as well as for the next 30 years. The results show that, despite the relatively moderate-to-high seismicity from west to east, there is no remarkable earthquake in the vicinity before the first reservoir impoundment. Immediately after the impoundment (January 1981), and during the first 4 months, a considerable number of low-magnitude seismic events were recorded in the broader area of the dam. Moreover, two independent major events occurred on March 10, 1981 ( M L = 5.6) and April 10, 1981 ( M L = 4.7) with focal depths 13 and 10 km, respectively. The detailed analysis of the two corresponding aftershock sequences shows that they present different behaviors (e.g., larger b-value and lower magnitude of the main aftershock) than that of other aftershock sequences in Greece. This seismicity is probably due to triggering, via the water loading mechanism and the undrained response due to a flysch appearance on the reservoir basement. The activation of the thrust fault may be attributed to the bulging of evaporites that characterize the disordered structure of W. Greece, via possible water intake. The detailed processing of the recorded seismicity during the period 1982-2010, in comparison with the variations of Pournari Dam water level, shows an increase of shallow seismicity ( h ≤ 5 km) in the vicinity of the reservoir up to a 10-km distance—in contrast to the initial period, characterized by a number of deeper events due to the background response change from undrained to drained status.

  20. Evidences for higher nocturnal seismic activity at the Mt. Vesuvius

    NASA Astrophysics Data System (ADS)

    Mazzarella, Adriano; Scafetta, Nicola

    2016-07-01

    We analyze hourly seismic data measured at the Osservatorio Vesuviano Ovest (OVO, 1972-2014) and at the Bunker Est (BKE, 1999-2014) stations on the Mt. Vesuvius. The OVO record is complete for seismic events with magnitude M ≥ 1.9. We demonstrate that before 1996 this record presents a daily oscillation that nearly vanishes afterwards. To determine whether a daily oscillation exists in the seismic activity of the Mt. Vesuvius, we use the higher quality BKE record that is complete for seismic events with magnitude M ≥ 0.2. We demonstrate that BKE confirms that the seismic activity at the Mt. Vesuvius is higher during nighttime than during daytime. The amplitude of the daily oscillation is enhanced during summer and damped during winter. We speculate possible links with the cooling/warming diurnal cycle of the volcanic edifice, with external geomagnetic field and with magnetostriction, which stress the rocks. We find that the amplitude of the seismic daily cycle changes in time and has been increasing since 2008. Finally, we propose a seismic activity index to monitor the 24-hour oscillation that could be used to complement other methodologies currently adopted to determine the seismic status of the volcano to prevent the relative hazard.

  1. Seismicity of the Lake Tahoe-Reno Area, Nevada and California

    NASA Astrophysics Data System (ADS)

    Smith, K. D.; Hauksson, S. E.

    2010-12-01

    Earthquakes in Lake-Tahoe Reno area are relocated with phase and waveform cross-correlation data using USGS application HYPODD. An approximately 10 km wide zone of seismicity extends from near Tahoe City, California eastward into south urban Reno. It represents one of several similar northeast trending zones of deformation and seismicity along the Walker Lane Belt of the western Great Basin. The area directly north of Lake Tahoe area is located in the transition between north-striking normal faulting systems that make up the Sierran frontal fault zone, to the south, and primary right-lateral strike slip fault zones of the northern Walker Lane Belt, to the north. Whereas the major normal faults along the Sierran front near the Reno-Tahoe area show little micro-earthquake activity, slip transfer regions, similar to what we observe north of Lake Tahoe include persistent seismicity, most likely involving numerous faults within an area distributed deformation. Although the fairly well defined northeast trend of seismicity north of Lake Tahoe includes M ~4+ left-lateral strike slip events consistent with the general orientation of the activity, right-lateral and normal faulting M ~4 earthquakes also occur along the trend. Additionally, portions of this northeast trending zone of activity consist of northwesterly alignments of small magnitude events and localized clusters of seismicity. The distributed seismicity and variety of focal mechanisms most likely reflects the transition from primary normal faulting to strike-slip faulting from south to north. The T-axes from earthquake focal mechanisms are oriented E-W at this latitude along the Sierran front. At its western extent, North Tahoe activity joins with northwest trending alignments of small magnitude events that evolve northwestward into the Mohawk Valley fault zone, near Sierraville, California. Its eastern extent, in south Reno, is nearly coincident with the southeastern limit of the 2008 Mogul-Somersett earthquake

  2. Seismic activity monitoring in the Izvorul Muntelui dam region

    NASA Astrophysics Data System (ADS)

    Borleanu, Felix; Otilia Placinta, Anca; Popa, Mihaela; Adelin Moldovan, Iren; Popescu, Emilia

    2016-04-01

    Earthquakes occurrences near the artificial water reservoirs are caused by stress variation due to the weight of water, weakness of fractures or faults and increasing of pore pressure in crustal rocks. In the present study we aim to investigate how Izvorul Muntelui dam, located in the Eastern Carpathians influences local seismicity. For this purpose we selected from the seismic bulletins computed within National Data Center of National Institute for Earth Physics, Romania, crustal events occurred between 984 and 2015 in a range of 0.3 deg around the artificial lake. Subsequently to improve the seismic monitoring of the region we applied a cross-correlation detector on the continuous recordings of Bicaz (BIZ) seismic stations. Besides the tectonic events we detected sources within this region that periodically generate artificial evens. We couldn't emphasize the existence of a direct correlation between the water level variations and natural seismicity of the investigated area.

  3. Ground motion prediction for the Vienna Basin area using the ambient seismic field

    NASA Astrophysics Data System (ADS)

    Schippkus, Sven; Zigone, Dimitri; Bokelmann, Götz; AlpArray Working Group

    2016-04-01

    The Vienna Basin is one of the most seismically active regions in Austria. Because of the population density and sensitive infrastructure, seismic hazard assessment in this area is of critical importance. An important part of seismic hazard analysis is ground motion prediction, which can in principle be done using either empirical studies to derive ground motion prediction equations (GMPEs) or using a physics-based approach to simulate ground motion by modelling surface wave propagation. Recently a new method has been presented that is based on the emergence of the inter-station Green's function from ambient noise cross-correlations (Denolle et al. 2013), which provides the impulse response of the Earth from a point source at the surface (from the site of one of the two receivers to the other). These impulse responses are dominated by surface waves, which would, in the case of a real earthquake, cause the major damages. The Green's function can in principle be modified to simulate a double couple dislocation at depth, i.e., a virtual earthquake. Using an adapted pre-processing method, the relative amplitudes of the ambient noise records of different inter-station paths are preserved in the correlation functions, and effects like attenuation and amplification of surface waves in sedimentary basins can be studied. This provides more precise information that will help improve seismic hazard evaluations. Here we present a preliminary study of such ground motion prediction for the Vienna Basin using about two dozen broadband stations from available networks in the area, e.g., stations from the University of Vienna (AlpArray) and Vienna Technical University. References Denolle, M. A., E. M. Dunham, G. A. Prieto, and G. C. Beroza (2013), Ground motion prediction of realistic earthquake sources using the ambient seismic field, J. Geophys. Res. Solid Earth, 118, 2102-2118, doi:10.1029/2012JB009603.

  4. Continuous, Large-Scale Processing of Seismic Archives for High-Resolution Monitoring of Seismic Activity and Seismogenic Properties

    NASA Astrophysics Data System (ADS)

    Waldhauser, F.; Schaff, D. P.

    2012-12-01

    Archives of digital seismic data recorded by seismometer networks around the world have grown tremendously over the last several decades helped by the deployment of seismic stations and their continued operation within the framework of monitoring earthquake activity and verification of the Nuclear Test-Ban Treaty. We show results from our continuing effort in developing efficient waveform cross-correlation and double-difference analysis methods for the large-scale processing of regional and global seismic archives to improve existing earthquake parameter estimates, detect seismic events with magnitudes below current detection thresholds, and improve real-time monitoring procedures. We demonstrate the performance of these algorithms as applied to the 28-year long seismic archive of the Northern California Seismic Network. The tools enable the computation of periodic updates of a high-resolution earthquake catalog of currently over 500,000 earthquakes using simultaneous double-difference inversions, achieving up to three orders of magnitude resolution improvement over existing hypocenter locations. This catalog, together with associated metadata, form the underlying relational database for a real-time double-difference scheme, DDRT, which rapidly computes high-precision correlation times and hypocenter locations of new events with respect to the background archive (http://ddrt.ldeo.columbia.edu). The DDRT system facilitates near-real-time seismicity analysis, including the ability to search at an unprecedented resolution for spatio-temporal changes in seismogenic properties. In areas with continuously recording stations, we show that a detector built around a scaled cross-correlation function can lower the detection threshold by one magnitude unit compared to the STA/LTA based detector employed at the network. This leads to increased event density, which in turn pushes the resolution capability of our location algorithms. On a global scale, we are currently building

  5. Local seismic network for monitoring of a potential nuclear power plant area

    NASA Astrophysics Data System (ADS)

    Tiira, Timo; Uski, Marja; Kortström, Jari; Kaisko, Outi; Korja, Annakaisa

    2016-04-01

    This study presents a plan for seismic monitoring of a region around a potential nuclear power plant. Seismic monitoring is needed to evaluate seismic risk. The International Atomic Energy Agency has set guidelines on seismic hazard evaluation and monitoring of such areas. According to these guidelines, we have made a plan for a local network of seismic stations to collect data for seismic source characterization and seismotectonic interpretations, as well as to monitor seismic activity and natural hazards. The detection and location capability of the network were simulated using different station configurations by computing spatial azimuthal coverages and detection threshold magnitudes. Background noise conditions around Pyhäjoki were analyzed by comparing data from different stations. The annual number of microearthquakes that should be detected with a dense local network centered around Pyhäjoki was estimated. The network should be dense enough to fulfill the requirements of azimuthal coverage better than 180° and automatic event location capability down to ML ˜ 0 within a distance of 25 km from the site. A network of 10 stations should be enough to reach these goals. With this setup, the detection threshold magnitudes are estimated to be ML = -0.1 and ML = 0.1 within a radius of 25 and 50 km from Pyhäjoki, respectively. The annual number of earthquakes detected by the network is estimated to be 2 (ML ≥ ˜ -0.1) within 25 km radius and 5 (ML ≥ ˜-0.1 to ˜0.1) within 50 km radius. The location accuracy within 25 km radius is estimated to be 1-2 and 4 km for horizontal coordinates and depth, respectively. Thus, the network is dense enough to map out capable faults with horizontal accuracy of 1-2 km within 25 km radius of the site. The estimation is based on the location accuracies of five existing networks in northern Europe. Local factors, such as seismic noise sources, geology and infrastructure might limit the station configuration and detection and

  6. A probabilistic method for evaluation of seismic amplification at a regional scale - A case study in some high seismic risk areas of the Northern Apennines (Italy)

    NASA Astrophysics Data System (ADS)

    Delle Donne, Dario; Ripepe, Maurizio; Lacanna, Giorgio; Marchetti, Emanuele; Fabbroni, Pierangelo; Baglione, Massimo; D'Intinosante, Vittorio

    2014-05-01

    Seismic amplification caused by local geological conditions has an important role in seismic risk assessment. The main parameters controlling seismic amplification are the shear wave velocities of shallow sub-surface (Vs) and the thickness of soft sediments (h). However, the knowledge of shear wave velocity profile is usually sparse and can not be measured over large areas. In this study we propose a method that integrates data from surface geological maps with data from subsurface seismo-stratigraphic well-logs, and is aimed to estimate seismic amplification over large areas (~100 km2) through a probabilistic approach. The methodology we developed is characterized by the following steps: 1. Analysis of the geological framework and definition of Seismic Units; 2. 1-D seismic modeling of each Seismic Unit; 3. Probability analysis of Seismic Amplification. Probability function of seismic amplification for each Seismic Unit is calculated for all the possible combinations of the expected values of Vs and thickness (h). We apply this approach to seismic areas in the Northern Apennines (Italy). Finally, the results of this analysis have been validated by seismic amplification measurements using local and regional earthquakes and with macro-seismic data. The comparison between the predicted amplification using this probabilistic approach and the measured seismic amplification shows a general agreement. This work is not intended as an alternative to the standard methodologies to calculate site effect, but offers a new approach to identify areas potentially more vulnerable.

  7. Temporary seismic networks on active volcanoes of Kamchatka (Russia)

    NASA Astrophysics Data System (ADS)

    Jakovlev, Andrey; Koulakov, Ivan; Abkadyrov, Ilyas; Shapiro, Nikolay; Kuznetsov, Pavel; Deev, Evgeny; Gordeev, Evgeny; Chebrov, Viktor

    2016-04-01

    We present details of four field campaigns carried out on different volcanoes of Kamchatka in 2012-2015. Each campaign was performed in three main steps: (i) installation of the temporary network of seismic stations; (ii) autonomous continuous registration of three component seismic signal; (III) taking off the network and downloading the registered data. During the first campaign started in September 2012, 11 temporary stations were installed over the Avacha group of volcanoes located 30 km north to Petropavlovsk-Kamchatsky in addition to the seven permanent stations operated by the Kamchatkan Branch of the Geophysical Survey (KBGS). Unfortunately, with this temporary network we faced with two obstacles. The first problem was the small amount of local earthquakes, which were detected during operation time. The second problem was an unexpected stop of several stations only 40 days after deployment. Nevertheless, after taking off the network in August 2013, the collected data appeared to be suitable for analysis using ambient noise. The second campaign was conducted in period from August 2013 to August 2014. In framework of the campaign, 21 temporary stations were installed over Gorely volcano, located 70 km south to Petropavlovsk-Kamchatsky. Just in time of the network deployment, Gorely Volcano became very seismically active - every day occurred more than 100 events. Therefore, we obtain very good dataset with information about thousands of local events, which could be used for any type of seismological analysis. The third campaign started in August 2014. Within this campaign, we have installed 19 temporary seismic stations over Tolbachik volcano, located on the south side of the Klyuchevskoy volcano group. In the same time on Tolbachik volcano were installed four temporary stations and several permanent stations operated by the KBGS. All stations were taking off in July 2015. As result, we have collected a large dataset, which is now under preliminary analysis

  8. The feeder system for the 2014 fissure eruption at Holuhraun, Bárðarbunga volcanic system, Iceland: Geodetic and seismic constraints on subsurface activity in the area north of the Vatnajökull ice cap

    NASA Astrophysics Data System (ADS)

    Dumont, Stéphanie; Parks, Michelle; Sigmundsson, Freysteinn; Hooper, Andy; Hreinsdóttir, Sigrun; Ófeigsson, Benedikt; Spaans, Karsten; Vogfjörd, Kristin; Jónsdóttir, Kristín; Hensch, Martin; Gudmundsson, Gunnar; Rafn Heimisson, Elias; Drouin, Vincent; Árnadóttir, Thóra; Pedersen, Rikke; Rut Hjartardóttir, Ásta; Magnússon, Eyjólfur

    2015-04-01

    An intense earthquake swarm began on 16 August 2014 at Bárðarbunga volcano under the Vatnajökull ice cap in Central Iceland. It marked the beginning of an intrusive activity, with a dyke propagating over 45 km northward. Such major magmatic activity has not been observed for the last three decades in Iceland, since the Krafla rifting episode 1975-1984. The dyke propagation stopped 15 days after the onset of the seismic activity, with the dyke distal end in the Holuhraun plain north of the Vatnajökull ice cap. A small 4 hour eruption marked the beginning of extrusive activity. A new fissure eruption opened up on 31 August at the northern dyke tip, with lava fountaining and feeding extensive lava flows. In January 2014 the surface covered by the lava had exceeded 80 km2, and the eruption activity does not show significant decline. We have carried out interferometric analysis of SAR data (InSAR) since the onset of the unrest. X-band satellite images from COSMO-SkyMed and TerraSAR-X satellites were acquired and analyzed to map ground surface deformation associated with the dyke emplacement. Despite most of the dyke propagation occurring under several hundreds meters of ice, the last 10 km were outside the ice cap, allowing better characterisation of the dyke-induced deformation. Here we focus on the deformation in the Holuhraun plain, in order to better understand the link between the surface deformation detected in the vicinity of the dyke by InSAR as well as GPS measurements, and the eruptive activity. The regular SAR acquisitions made over the Holuhraun area since the beginning of the unrest offer a unique opportunity to better understand the evolution of the intrusion feeding the fissure eruption. For that purpose, we focus on the faults and fissures forming the graben borders on the glacier as well as in the Holuhraun plain, initially mapped using high-resolution radar images, acquired by airborne radar. We extract movement along and perpendicular to these

  9. Seismic Velocities Imaging around "AFA" Hydrothermal Area in West Java, Indonesia derived from Dense Seimometer Network

    NASA Astrophysics Data System (ADS)

    Fanani Akbar, Akhmad; Nugraha, Andri Dian; Jousset, Philippe GM; Ryannugroho, Riskiray; Gassner, Alexandra; Jaya, Makky S.; Sule, Rachmat; Diningrat, Wahyuddin; Hendryana, Andri; Kusnadi, Yosep; Umar, Muksin; Indrinanto, Yudi; Erbas, Kemal

    2015-04-01

    We have deployed about 48 three component seismometers around "AFA" hydrothermal are in West Java, Indonesia from October 2012 up to October 2014 in order to detect microseismic event and to enhance our knowledge about subsurface seismic stucture. The seismometer network in this study, is the first dense seismometer array monitoring around hydrothermal area in Indonesia so far. We analyzed a huge waveform data set to distinguish microseismic, local and regional events. Then, we picked the onset of P-and S-wave arrival of microseismic events carefully visually by eye. We determined the initial microseismic event by applying Geiger's method with uniform seismic velocity model. Totally, we have been successfully determined 2,497 microseismic events around this hydrothermal area. We also improved 1D seismic velocities (Vp, Vs) and simultaneously with hypocenter adjustment as input for the tomography inversion in this study. Overall, the microseismic events are concentrated around production area activities and we also found strong cluster microseismic event in Southern part of this region which still need to be investigated in more details. Now, we are going on tomographic inversion step by using double-difference method. We are going to show more information during the meeting.

  10. Seismic imaging of the geodynamic activity at the western Eger rift in central Europe

    NASA Astrophysics Data System (ADS)

    Mullick, N.; Buske, S.; Hrubcova, P.; Ruzek, B.; Shapiro, S.; Wigger, P.; Fischer, T.

    2015-04-01

    The western Eger rift at the Czech-German border in central Europe is an important geodynamically active area within the European Cenzoic rift system (ECRS) in the forelands of the Alps. Along with two other active areas of the ECRS, the French Massif Central and the east and west Eifel volcanic fields, it is characterized by numerous CO2-rich fluid emission points and frequent micro-seismicity. Existence of a plume(s) is indicated in the upper mantle which may be responsible for these observations. Here we reprocess a pre-existing deep seismic reflection profile '9HR' and interpret the subsurface structures as mapped by seismic reflectivity with previous findings, mainly from seismological and geochemical studies, to investigate the geodynamic activity in the subsurface. We find prominent hints of pathways which may allow magmatic fluids originating in the upper mantle to rise through the crust and cause the observed fluid emanations and earthquake activity.

  11. Erosion influence the seismicity of active thrust faults

    NASA Astrophysics Data System (ADS)

    Steer, Philippe; Simoes, Martine; Cattin, Rodolphe; Shyu, J. Bruce H.

    2015-04-01

    Assessing seismic hazards remains one of the most challenging scientific issue in Earth sciences. Deep tectonic processes are classically considered as the only persistent mechanism driving the stress loading of active faults over a seismic cycle. Here we show with a mechanical model that erosion also significantly influences the stress loading of thrust faults at the timescale of a seismic cycle. Indeed, erosion rates of about ~0.1 to 20 mm/yr, as documented in Taiwan and in other active compressional orogens, can raise the Coulomb stress by ~0.1 to ~10 bar on the nearby thrust faults over the inter-seismic phase. Mass transfers induced by surface processes in general, during continuous or short-lived and intense events, represent a prominent mechanism for inter-seismic stress loading of faults near the surface. Such stresses are probably sufficient to promote the rupture of deep continental earthquakes up to the surface or to trigger shallow seismicity. We illustrate this last point by identifying seismic events in Taiwan, by the mean of a coupled statistical and mechanical approach, that were induced by intense erosional events.

  12. Erosion influence the seismicity of active thrust faults

    NASA Astrophysics Data System (ADS)

    Steer, Philippe; Simoes, Martine; Cattin, Rodolphe; Shyu, J. Bruce H.

    2016-04-01

    Assessing seismic hazards remains one of the most challenging scientific issue in Earth sciences. Deep tectonic processes are classically considered as the only persistent mechanism driving the stress loading of active faults over a seismic cycle. Here we show with a mechanical model that erosion also significantly influences the stress loading of thrust faults at the timescale of a seismic cycle. Indeed, erosion rates of about ˜0.1 to 20 mm/yr, as documented in Taiwan and in other active compressional orogens, can raise the Coulomb stress by ˜0.1 to ˜10 bar on the nearby thrust faults over the inter-seismic phase. Mass transfers induced by surface processes in general, during continuous or short-lived and intense events, represent a prominent mechanism for inter-seismic stress loading of faults near the surface. Such stresses are probably sufficient to promote the rupture of deep continental earthquakes up to the surface or to trigger shallow seismicity. We illustrate this last point by identifying seismic events in Taiwan, by the mean of a coupled statistical and mechanical approach, that were induced by intense erosional events.

  13. Geophysical Anomalies and Seismicity Suggest a Connection Between the Hayward and Calaveras Faults, Eastern San Francisco Bay Area, Northern California

    NASA Astrophysics Data System (ADS)

    Ponce, D. A.; Phelps, G. A.; Graymer, R. W.; Jachens, R. C.; Simpson, R. W.; Wentworth, C. M.

    2003-12-01

    Gravity, magnetic, and seismicity data of the eastern San Francisco Bay Area are used to reveal the three-dimensional subsurface geologic structure of the eastern San Francisco Bay Area and its relationship to ongoing seismicity. Combined, these data suggest a connection between the Hayward and Calaveras Faults. Gravity and magnetic modeling of a tabular gabbro body near San Leandro and relocated, double-difference seismicity data along the Hayward Fault (Ellsworth et al., 2000) suggest that the Hayward Fault dips to the northeast. Further southeast, double-difference seismicity data indicate that the fault dip becomes shallower, possibly connecting the creeping surface trace of the Hayward Fault with the diverging Mission seismicity trend at depth as suggested by Manaker and Michael (2003). In the stepover region, the southern extension of the Hayward Fault is parallel to the active central Calaveras Fault for about 25 km and the 4-km wide area in between is characterized by en echelon reverse (oblique?) faults. At depths below about 5 km, seismicity appears to be continuous, connecting the Hayward fault to the left-stepping central Calaveras Fault along the Mission seismicity trend. Geophysical interpretation of offset magnetic rock units also suggests that the northern Calaveras Fault has at most a few tens of kilometers of total offset and that most slip may be transferred from the southern Calaveras Fault, with a total offset of about 175 km, along the central Calaveras, Silver Creek, Hayward, and other faults west of the northern Calaveras Fault, consistent with present seismicity. Cross-sectional and 3D visualizations of these data are used to illustrate the proposed geometry of the connection between the Hayward and Calaveras Faults.

  14. Seismicity and Deep Structure of the Joint Area of Eurasian, North American and Okhotomorsk Plates

    NASA Astrophysics Data System (ADS)

    Soloviev, V. M.; Seleznev, V. S.; Salnikov, A. S.; Timofeev, V. Y.; Shibaev, S. V.; Petrov, A.; Liseikin, A. V.; Shenmayer, A. E.

    2013-05-01

    Modern geodynamics and seismicity of Far-Eastern region is mostly determined by interaction of Eurasian, Pacific, North American and supposed Amur and Okhotomorsk plates. The paper presents materials on seismicity, deep structure and space geodesy. These materials are used as a base for research the joint region of the plates. All earthquakes of this zone are aroused in the middle and in the bottom parts of the Earth`s crust at the depth of 7-30km. Seismic investigations and DSS observations materials show that seismic process is proceeding at pressure conditions. According to the DSS materials at the regional geotransect 2-DV (Magadan - Vrangel island) there is registered significant decrease of boundary velocity values (to 7.5-7.7 km/sec) along the Moho in the joint zone and local raise of the Moho. At the deep seismographic section in this zone we can see extremely heterogeneous middle crust, reduction of reflection contrast in the bottom of the crust and in the Moho section. In this zone we can also see reduction of average (effective) velocity in all stratum of the Earth`s crust, it can be an evidence of high fragmentation of the Earth`s crust structures. These materials, along with high seismicity at great depths up to 30 km, show appearance of the joint region of Okhotomorsk and North American plates not only in the upper part of the Earth`s crust, but also in the middle and in the bottom parts of the crust and in the Moho section. Along with the profile data of the geotransect 2-DV there are presented modern materials of areal seismological investigations for a section of joint of three big plates: earthquakes quantity distribution, total dedicated seismic energy and K- parameter, connected with velocities of P- and S-waves within seismic active layer of the Earth`s crust. By these data, the boundary of North American plate with Eurasian plate in the north and with Okhotomorsk plate in the south is more contrasting. The most severe earthquakes are also

  15. Variation of the Earth tide-seismicity compliance parameter during the recent seismic activity of Fthiotida, Greece

    NASA Astrophysics Data System (ADS)

    Contadakis, Michael; Aarabelos, Dimitrios; Vergos, Georgios; Spatalas, Spyridon

    2014-05-01

    Applying the Hi(stogram)Cum(ulation) method, which was introduced recently by Cadicheanu, van Ruymbecke and Zhu (2007), we analyze the series of the earthquakes occurred in the last 50 years in seismic active areas of Greece, i.e. the areas (a) of the Mygdonian Basin(Contadakis et al. 2007), (b) of the Ionian Islands (Contadakis et al. 2012 ) and (c) of the Hellenic Arc (Vergos et al. 2012 ) . The result of the analysis for all the areas indicate that the monthly variation of the frequencies of earthquake occurrence is in accordance with the period of the tidal lunar monthly and semi-monthly (Mm and Mf) variations and the same happens with the corresponding daily variations of the frequencies of earthquake occurrence with the diurnal luni-solar (K1) and semidiurnal lunar (M2) tidal variations. In addition the confidence level for the identifiation of such period accordance between earthquakes occurrence frequency and tidal periods varies with seismic activity, i.e. the higher confidence level corresponds to periods with stronger seismic activity. These results are in favor of a tidal triggering process on earthquakes when the stress in the focal area is near the critical level. Based on these results, we consider the confidence level of earthquake occurrence - tidal period accordance, p, as an index of tectonic stress criticality for earthquake occurrence and we check on posterior if the variation of the confidence level index, p, indicate the fault matureness in the case of the recent seismic activity at Fthiotida, Greece. In this paper we present the results of this test. References Cadicheanu, N., van Ruymbeke, M andZhu P.,2007:Tidal triggering evidence of intermediate depth earthquakes in Vrancea zone(Romania), NHESS 7,733-740. Contadakis, M. E., Arabelos, D. N., Spatalas, S., 2009, Evidence for tidal triggering on the shallow earthquakes of the seismic area of Mygdonia basin, North Greece, in Terrestrial and Stellar Environment, eds.D. Arabelos, M

  16. Seismic activity triggered by water wells in the Paraná Basin, Brazil

    NASA Astrophysics Data System (ADS)

    AssumpçãO, Marcelo; Yamabe, Tereza H.; Barbosa, José Roberto; Hamza, Valiya; Lopes, Afonso E. V.; Balancin, Lucas; Bianchi, Marcelo B.

    2010-07-01

    Triggered seismicity is commonly associated with deep water reservoirs or injection wells where water is injected at high pressure into the reservoir rock. However, earth tremors related solely to the opening of groundwater wells are extremely rare. Here we present a clear case of seismicity induced by pore-pressure changes following the drilling of water wells that exploit a confined aquifer in the intracratonic Paraná Basin of southeastern Brazil. Since 2004, shallow seismic activity, with magnitudes up to 2.9 and intensities V MM, has been observed near deep wells (120-200 m) that were drilled in early 2003 near the town of Bebedouro. The wells were drilled for irrigation purposes, cross a sandstone layer about 60-80 m thick and extract water from a confined aquifer in fractured zones between basalt flow layers. Seismic activity, mainly event swarms, has occurred yearly since 2004, mostly during the rainy season when the wells are not pumped. During the dry season when the wells are pumped almost continuously, the activity is very low. A seismographic network, installed in March 2005, has located more than 2000 microearthquakes. The events are less than 1 km deep (mostly within the 0.5 km thick basalt layer) and cover an area roughly 1.5 km × 5 km across. The seismicity generally starts in a small area and expands to larger distances with an equivalent hydraulic diffusivity ranging from 0.06 to 0.6 m2/s. Geophysical and geothermal logging of several wells in the area showed that water from the shallow sandstone aquifer enters the well at the top and usually forms waterfalls. The waterfalls flow down the sides of the wells and feed the confined, fractured aquifer in the basalt layer at the bottom. Two seismic areas are observed: the main area surrounds several wells that are pumped continuously during the dry season, and a second area near another well (about 10 km from the first area) that is not used for irrigation and not pumped regularly. The main area

  17. Active and passive seismic studies of geothermal resources in New Mexico and investigations of earthquake hazards to geothermal development

    SciTech Connect

    Morgan, P.; Daggett, P.H.

    1980-01-01

    Seismic data were collected in southwestern New Mexico to investigate the sources of the geothermal anomalies and to investigate the potential earthquake hazards of geothermal development. No major crustal structure anomalies have been located related to known geothermal resources, and no areas of continual seismicity have been identified, which is interpreted to indicate a lack of active, or recently active crustal intrusions in southwestern New Mexico. Without a magnetic heat source, the geothermal potential of the known anomalies is probably limited to intermediate and low temperature applications (<180/sup 0/C). The lack of continual seismicity indicates low seismic hazard in the area directly related to geothermal development, although the historic and geologically recent tectonic activity should be taken into consideration during any development in the area. A model of forced groundwater convection is presented to explain the geothermal anomalies in southwestern New Mexico, which is consistent with all available geological and geophysical data from the area.

  18. Geomorphological features of active tectonics and ongoing seismicity of northeastern Kumaun Himalaya, Uttarakhand, India

    NASA Astrophysics Data System (ADS)

    Pathak, Vivekanand; Pant, Charu C.; Darmwal, Gopal Singh

    2015-08-01

    The northeastern part of Kumaun Lesser Himalaya, Uttarakhand, India, lying between the rupture zones of 1905, Kangra and 1934, Bihar-Nepal earthquakes and known as `central seismic gap' is a segment of an active fault known to produce significant earthquakes and has not slipped in an unusually long time when compared to other segments. The studied section forms a part of this seismic gap and is seismically an active segment of the Himalayan arc, as compared to the remaining part of the Kumaun Lesser Himalaya and it is evident by active geomorphological features and seismicity data. The geomorphological features of various river valley transects suggest that the region had a history of tectonic rejuvenation which is testified by the deposition of various levels of terraces and their relative uplift, shifting and ponding of river channels, uplifted potholes, triangular facets on fault planes, fault scarps, etc. Further, the seismic data of five-station digital telemetered seismic network along with two stand alone systems show the distribution of earthquakes in or along the analyzed fault transects. It is observed that the microseismic earthquakes (magnitude 1.0-3.0) frequently occur in the region and hypocenters of these earthquakes are confined to shallow depths (10-20 km), with low stress drop values (1.0-10 bar) and higher peak ground velocity (PGV). The cluster of events is observed in the region, sandwiched between the Berinag Thrust (BT) in south and Main Central Thrust (MCT) in north. The occurrences of shallow focus earthquakes and the surface deformational features in the different river valley transect indicates that the region is undergoing neotectonic rejuvenation. In absence of chronology of the deposits it is difficult to relate it with extant seismicity, but from the geomorphic and seismic observations it may be concluded that the region is still tectonically active. The information would be very important in identifying the areas of hazard prone and

  19. Impacts of shaking Bengkulus seismicity to subsurface Wellbore in the XX area

    NASA Astrophysics Data System (ADS)

    Rusli, Saifatur; Pratama, M. Ardian; Mardiyan, Hilman; Mirza, Finisha, Brian

    2016-05-01

    Bengkulu earthquake was happened on Wednesday, May 5th 2010 at 23:29:03 WIB (UTC-7) with magnitude 6.5 Richter scale. The Epicentrum was very close to Mentawai Fault System located on latitude 4.063°S and longitude 101.085°E with depth subsurface 27 kms. It was occurred the result of the Indian Ocean Plate-Australia's activity with low angled-subducted beneath the island of Sumatra. Shaking Bengkulus seismicity impacted subsurface in the XX Area which situated on South Palembang Sub-Basin part of South Sumatra Basin (SSB) about 200 kms far away from the epicentrum. Due to XX Area has some producing wells so that the seismicity activities as hypothetically impacts to Subsurface Wellbore which has caused some wells casing problems in the same depth. The wells casing problem shown after conducted routine sand bailer by Sand Line Unit, it was a downhole device used to remove debris sands or similar small particles around the fishingnecks of downhole tools or equipment in the wellbore, and then Sand Bailer tools got scratch at one side body. Similarly, Sand Bailer tools couldnt lowered until Total Depth and got samples sands slightly. At the end, it has impacted to well performance to produce oil in the XX Area.

  20. Two-dimensional seismic attenuation images of Stromboli Island using active data

    NASA Astrophysics Data System (ADS)

    Prudencio, J.; Del Pezzo, E.; Ibáñez, J. M.; Giampiccolo, E.; Patané, D.

    2015-03-01

    In this work we present intrinsic and scattering seismic attenuation 2-D images of Stromboli Volcano. We used 21,953 waveforms from air gun shots fired by an oceanographic vessel and recorded at 33 inland and 10 ocean bottom seismometer seismic stations. Coda wave envelopes of the filtered seismic traces were fitted to the energy transport equation in the diffusion approximation, obtaining a couple of separate Qi and Qs in six frequency bands. Using numerically estimated sensitivity kernels for coda waves, separate images of each quality factor were produced. Results appear stable and robust. They show that scattering attenuation prevails over intrinsic attenuation. The scattering pattern shows a strong concordance with the tectonic lineaments in the area, while an area of high total attenuation coincides with the zone where most of the volcanic activity occurs. Our results provide evidence that the most important attenuation effects in volcanic areas are associated with the presence of geological heterogeneities.

  1. A Study on the Seismic Sequence Time Series for Arasbaran Area (NW Iran) as a Marker of Chaotic Process

    NASA Astrophysics Data System (ADS)

    Fathian Baneh, A.; Sarkhosh, L.

    2013-12-01

    Before August 11th, 2012 Arasbaran twin earthquakes (Mw 6.4 and Mw 6.3), no seismogenic fault has been fully recognized within the meizoseismal area of the events, neither there were obvious evidence on the microseismicity pattern of the region showing potentials of such activities for an earthquake to occur. In the present study, we tried to investigate the seismic activity of the area in a time period between 2006 and 2012 to verify whether symptoms are detectable in the seismicity of the region or not. In this case, we profited from two different approaches: a statistical method (considering which as a linear system) and Chaos theory (considering it as a non-linear system). We analyzed firstly the seismic time series based on magnitude/number of earthquakes versus time, using ARIMA modeling which refutes the linear behavior of the system. Therefore, we discussed the nonlinear behavior of earthquake time series of the study area to simply explain the complexities in the system using chaos theory for a time interval of six years. Moreover, the calculation of Lyapunov exponent was put into practice. Although results derived from ARIMA modeling indicate non-stability of the studied system and reveal the system undergoes a non-periodicity behavior, yet the positive estimated Lyapunov exponent obviously denotes the chaotic dynamics in the system. Such results could be used as a marker for more detailed further surveys of the areas which seem safe in terms of seismic hazard, as Arasbaran area was once deemed.

  2. Detecting seismic activity with a covariance matrix analysis of data recorded on seismic arrays

    NASA Astrophysics Data System (ADS)

    Seydoux, L.; Shapiro, N. M.; de Rosny, J.; Brenguier, F.; Landès, M.

    2016-03-01

    Modern seismic networks are recording the ground motion continuously at the Earth's surface, providing dense spatial samples of the seismic wavefield. The aim of our study is to analyse these records with statistical array-based approaches to identify coherent time-series as a function of time and frequency. Using ideas mainly brought from the random matrix theory, we analyse the spatial coherence of the seismic wavefield from the width of the covariance matrix eigenvalue distribution. We propose a robust detection method that could be used for the analysis of weak and emergent signals embedded in background noise, such as the volcanic or tectonic tremors and local microseismicity, without any prior knowledge about the studied wavefields. We apply our algorithm to the records of the seismic monitoring network of the Piton de la Fournaise volcano located at La Réunion Island and composed of 21 receivers with an aperture of ˜15 km. This array recorded many teleseismic earthquakes as well as seismovolcanic events during the year 2010. We show that the analysis of the wavefield at frequencies smaller than ˜0.1 Hz results in detection of the majority of teleseismic events from the Global Centroid Moment Tensor database. The seismic activity related to the Piton de la Fournaise volcano is well detected at frequencies above 1 Hz.

  3. Evaluating the Relationship Between Seismicity and Subsurface Well Activity in Utah

    NASA Astrophysics Data System (ADS)

    Lajoie, L. J.; Bennett, S. E. K.

    2014-12-01

    Understanding the relationship between seismicity and subsurface well activity is crucial to evaluating the seismic hazard of transient, non-tectonic seismicity. Several studies have demonstrated correlations between increased frequency of earthquake occurrence and the injection/production of fluids (e.g. oil, water) in nearby subsurface wells in intracontinental settings (e.g. Arkansas, Colorado, Ohio, Oklahoma, Texas). Here, we evaluate all earthquake magnitudes for the past 20-30 years across the diverse seismotectonic settings of Utah. We explore earthquakes within 5 km and subsequent to completion dates of oil and gas wells. We compare seismicity rates prior to well establishment with rates after well establishment in an attempt to discriminate between natural and anthropogenic earthquakes in areas of naturally high background seismicity. In a few central Utah locations, we find that the frequency of shallow (0-10 km) earthquakes increased subsequent to completion of gas wells within 5 km, and at depths broadly similar to bottom hole depths. However, these regions typically correspond to mining regions of the Wasatch Plateau, complicating our ability to distinguish between earthquakes related to either well activity or mining. We calculate earthquake density and well density and compare their ratio (earthquakes per area/wells per area) with several published metrics of seismotectonic setting. Areas with a higher earthquake-well ratio are located in relatively high strain regions (determined from GPS) associated with the Intermountain Seismic Belt, but cannot be attributed to any specific Quaternary-active fault. Additionally, higher ratio areas do not appear to coincide with anomalously high heat flow values, where rocks are typically thermally weakened. Incorporation of timing and volume data for well injection/production would allow for more robust temporal statistical analysis and hazard analysis.

  4. Detailed seismicity analysis revealing the dynamics of the southern Dead Sea area

    NASA Astrophysics Data System (ADS)

    Braeuer, B.; Asch, G.; Hofstetter, R.; Haberland, Ch.; Jaser, D.; El-Kelani, R.; Weber, M.

    2014-10-01

    Within the framework of the international DESIRE (DEad Sea Integrated REsearch) project, a dense temporary local seismological network was operated in the southern Dead Sea area. During 18 recording months, 648 events were detected. Based on an already published tomography study clustering, focal mechanisms, statistics and the distribution of the microseismicity in relation to the velocity models from the tomography are analysed. The determined b value of 0.74 leads to a relatively high risk of large earthquakes compared to the moderate microseismic activity. The distribution of the seismicity indicates an asymmetric basin with a vertical strike-slip fault forming the eastern boundary of the basin, and an inclined western boundary, made up of strike-slip and normal faults. Furthermore, significant differences between the area north and south of the Bokek fault were observed. South of the Bokek fault, the western boundary is inactive while the entire seismicity occurs on the eastern boundary and below the basin-fill sediments. The largest events occurred here, and their focal mechanisms represent the northwards transform motion of the Arabian plate along the Dead Sea Transform. The vertical extension of the spatial and temporal cluster from February 2007 is interpreted as being related to the locking of the region around the Bokek fault. North of the Bokek fault similar seismic activity occurs on both boundaries most notably within the basin-fill sediments, displaying mainly small events with strike-slip mechanism and normal faulting in EW direction. Therefore, we suggest that the Bokek fault forms the border between the single transform fault and the pull-apart basin with two active border faults.

  5. A multi-disciplinary approach for the structural monitoring of Cultural Heritages in a seismic area

    NASA Astrophysics Data System (ADS)

    Fabrizia Buongiorno, Maria; Musacchio, Massimo; Guerra, Ignazio; Porco, Giacinto; Stramondo, Salvatore; Casula, Giuseppe; Caserta, Arrigo; Speranza, Fabio; Doumaz, Fawzi; Giovanna Bianchi, Maria; Luzi, Guido; Ilaria Pannaccione Apa, Maria; Montuori, Antonio; Gaudiosi, Iolanda; Vecchio, Antonio; Gervasi, Anna; Bonali, Elena; Romano, Dolores; Falcone, Sergio; La Piana, Carmelo

    2014-05-01

    , synthetic aperture radar, optical, multispectral and panchromatic measurements), static and dynamic structural health monitoring analysis (e.g. screening tests with georadar, sonic instruments, sclerometers and optic fibers). The final purpose of the proposed approach is the development of an investigation methodology for short- and long-term Cultural Heritages preservation in response to seismic stress, which has specific features of scalability, modularity and exportability for every possible monitoring configuration. Moreover, it allows gathering useful information to furnish guidelines for Institution and local Administration to plan consolidation actions and therefore prevention activity. Some preliminary results will be presented for the test site of Calabria Region, where some architectural heritages have been properly selected as case studies for monitoring purposes. *The present work is supported and funded by Ministero dell'Università, dell'Istruzione e della Ricerca (MIUR) under the research project PON01-02710 "MASSIMO" - "Monitoraggio in Area Sismica di Sistemi Monumentali".

  6. How Washington got good, thrifty seismic in bad data area

    SciTech Connect

    Jarchow, C.M. ); Catchings, R.D.; Lutter, W.J. )

    1991-06-17

    Countless mature, emerging, and frontier basins remain incompletely tested for hydrocarbons because aspects of their geology make it nearly impossible to acquire clear subsurface seismic images. One need only look as far as the most productive hydrocarbon provinces in the U.S. for examples of this problem. In parts of West Texas, most particularly the Val Verde basin, carbonates severely degrade seismic images. Salt is a well known problem in the Gulf of Mexico. In Nevada, volcanics make sorting out complicated structure a daunting exercise. Permafrost is a persistent headache for explorationists working on the North Slope of Alaska. Although degraded seismic images are commonplace and the lithologies associated with them are numerous, the physical cause of the degradation is roughly the same from basin to basin and lithology to lithology. In nearly all cases, problematic lithologies introduce into a stratigraphic package an abundance of very large seismic velocity contrasts. In volcanic flows, large velocity contrasts are associated with interbeds, brecciation, and vessiculation. In carbonates, karst features play an analogous role. When seismic waves impinge upon these contrasts, multiple generation, mode conversion, and scattering occur, producing high-amplitude reverberations.

  7. "Water bombs" and seismic areas: two sides to the same problem?

    NASA Astrophysics Data System (ADS)

    Straser, Valentino; Casati, Michele; Cataldi, Gabriele

    2016-04-01

    Intensification of catastrophic events over the last few years in Northern Tuscany (Italy), caused by real "water bombs", with the ensuing risk of flooding and an increase in seismicity, may point to a cause-effect relationship between the two phenomena. A relationship between baric variations and seismic activity resulting in earthquakes with a magnitude greater than M3, has already been described by Sytinsky (1997). Studies carried out on atmospheric processes during strong earthquakes have shown that there are also strong perturbations in atmospheric circulation, which manifest as a major restructuring of the pressure fields, as with changes in meteorological parameters. Recent studies by Straser (2015) have emphasized that variations in atmospheric pressure can affect the equilibrium of the rocks in fault zones, above all if part of a distensive tectonic context like the Lunigiana and Garfagnana area, which became an open-air laboratory to carry out this current study. Interaction between tectonic thrusts, the gases emitted in areas under crust stress, the production of ions in the atmosphere, detectable instrumentally and associated with pre-seismic signals have been described by Pulinets, (2007) and Pulinets with Boyarchuk (2004), as has the formation of nano particles and filamentous structures, of varying origin, caused by a combination of meteoric phenomena associated with electrical discharges and airborne ions as highlighted by Courty and Martinez (2015). One element to bear in mind when hypothesizing variations in equilibrium in distensive faults, is water. Indeed, it has been proposed that the quantity of water that reaches the ground during the kinds of strong precipitation analysed in this study might well create pressure variations in close proximity to the faults at the same time as lowering the friction coefficient in tectonically vulnerable areas. In contrast, it has also been suggested that frequent and prolonged seismic activity in the same

  8. Crustal structure in the Kiruna area, northern Sweden, based on seismic reflection profiling

    NASA Astrophysics Data System (ADS)

    Juhojuntti, Niklas; Bergman, Stefan; Olsson, Sverker

    2013-04-01

    Northernmost Sweden is currently one of the most active mining areas in Europe. In order to better understand the regional three-dimensional crustal structure and to support deep ore exploration, we have acquired a 74 km long seismic reflection profile in the Kiruna area. The upper crust in this area is largely composed of various supracrustal units, which are dominated by metabasalts, acidic metavolcanics and clastic metasedimentary rocks, resting on an Archaean metagranitoid complex. All of these units have been intruded by plutonic rocks, and to variable degrees folded, sheared and metamorphosed, during the Svecokarelian orogeny. The profile crosses several steep ductile shear zones, some of which extend for hundreds of kilometres along strike. Many of the lithological contacts and deformation zones are expected to be seismically reflective. The profile is located only a few kilometres from the world's largest underground iron-ore mine in Kiruna, and closer to the profile there are several known ore bodies, some of which are active exploration targets. For the seismic recording we used approximately 350 geophones in split-spread configuration, at a separation of 25 m. The main seismic source was the Vibsist system (an impact source), which normally was employed at every geophone station. We also fired explosive charges (8-16 kg) at a few locations distributed along the profile to image deeper structures, although at very low resolution. Wireless seismometers were placed along and to the side of the profile, mainly in order to achieve better velocity control and to study out-of-the-plane reflections. Some mining blasts in Kiruna were also recorded. The upper crust in the area is quite reflective, most clearly demonstrated by the dynamite shot records. Some of the reflections appear to originate from steeply dipping structures. The dynamite shot records show a set of reflections at 3-4 s twt, corresponding to a depth of roughly 10 km, the explanation for which is

  9. A preliminary census of engineering activities located in Sicily (Southern Italy) which may "potentially" induce seismicity

    NASA Astrophysics Data System (ADS)

    Aloisi, Marco; Briffa, Emanuela; Cannata, Andrea; Cannavò, Flavio; Gambino, Salvatore; Maiolino, Vincenza; Maugeri, Roberto; Palano, Mimmo; Privitera, Eugenio; Scaltrito, Antonio; Spampinato, Salvatore; Ursino, Andrea; Velardita, Rosanna

    2015-04-01

    The seismic events caused by human engineering activities are commonly termed as "triggered" and "induced". This class of earthquakes, though characterized by low-to-moderate magnitude, have significant social and economical implications since they occur close to the engineering activity responsible for triggering/inducing them and can be felt by the inhabitants living nearby, and may even produce damage. One of the first well-documented examples of induced seismicity was observed in 1932 in Algeria, when a shallow magnitude 3.0 earthquake occurred close to the Oued Fodda Dam. By the continuous global improvement of seismic monitoring networks, numerous other examples of human-induced earthquakes have been identified. Induced earthquakes occur at shallow depths and are related to a number of human activities, such as fluid injection under high pressure (e.g. waste-water disposal in deep wells, hydrofracturing activities in enhanced geothermal systems and oil recovery, shale-gas fracking, natural and CO2 gas storage), hydrocarbon exploitation, groundwater extraction, deep underground mining, large water impoundments and underground nuclear tests. In Italy, induced/triggered seismicity is suspected to have contributed to the disaster of the Vajont dam in 1963. Despite this suspected case and the presence in the Italian territory of a large amount of engineering activities "capable" of inducing seismicity, no extensive researches on this topic have been conducted to date. Hence, in order to improve knowledge and correctly assess the potential hazard at a specific location in the future, here we started a preliminary study on the entire range of engineering activities currently located in Sicily (Southern Italy) which may "potentially" induce seismicity. To this end, we performed: • a preliminary census of all engineering activities located in the study area by collecting all the useful information coming from available on-line catalogues; • a detailed compilation

  10. Seismic activity in the Sunnyside mining district, Utah, during 1967

    USGS Publications Warehouse

    Barnes, Barton K.; Dunrud, C. Richard; Hernandez, Jerome

    1969-01-01

    A seismic monitoring network near Sunnyside, Utah, consisting of a triangular array of seismometer stations that encompasses most of the mine workings in the district, recorded over 50,000 local earth tremors during 1967. About 540 of the tremors were of sufficient magnitude to be accurately located. Most of these were located within 2-3 miles of mine workings and were also near known or suspected faults. The district-wide seismic activity generally consisted of two different patterns--a periodic increase in the daily number of tremors at weekly intervals, and also a less regular and longer term increase and decrease of seismic activity that occurred over a period of weeks or even months. The shorter and more regular pattern can be correlated with the mine work week and seems to result from mining. The longer term activity, however, does not correlate with known mining causes sad therefore seems to be .caused by natural stresses.

  11. Multivariable Observations of Pre and Co-Seismic Electromagnetic Activity in Peru: Past, Present and Future

    NASA Astrophysics Data System (ADS)

    Heraud, J. A.; Lira, J. A.; Montes, L.; Rosas, S.; Centa, V.; Bleier, T. E.

    2012-12-01

    The Mw8.0 earthquake in Pisco, Peru of August 15, 2007 was reported previously and shown to have produced extensive co-seismic luminescence away from the epicenter. Continued research will be presented in which a high coincidence exists between the location of the areas where the luminescence was video recorded and reported by qualified witnesses and the geological formation in the bay in which Jurassic and Cretaceous lithologic igneous components are present, a condition that contributes to the displacement of electric charges in the rock. Additionally, the San Lorenzo Island has become the focus of a new research effort due to the past record of pre-seismic EQLs reported and published in relation with the mega-earthquake of 1746, the previously reported co-seismic EQLs in 2007 and new evidence of pre-seismic EQLs reported one and a half days before a ML4.6 earthquake on July 29, 2012. New experiments are hitherto being deployed in San Lorenzo Island to pursue the identification of favorable conditions for the propagation of electric charges in connection with pressure on rocks due to seismic activity. Thus, continuously recording video cameras, charge potential measuring plates, recording of HF and VHF noise and the installation of a new magnetometer to detect pulse activity in the local magnetic field and twin (+/-) air conductivity sensors are being installed on the island. Additionally, a new rock experiment to analyze the displacement of charges with local rocks is under way. The expectation of a Mega earthquake in the Lima area is building up as we approach the third century without mayor seismic activity in the area so the deployment of a new network of five magnetometers for the Lima area has started.

  12. Estimation of the Cumulative Fault Area Under Critical State Based on Microseismic Dataset at Hydraulic Stimulation for Seismic Risk Assessment

    NASA Astrophysics Data System (ADS)

    Mukuhira, Y.; Asanuma, H.; Häring, M. O.; Ito, T.

    2014-12-01

    Occurrence of induced seismicity with large magnitude has been considered as critical environmental burden associated with fluid injection for shale gas/oil extraction, waste water disposal, and creation of engineered geothermal systems (EGS). Therefore, studies for understandings of the large events and risk assessment of induced seismicity has been activated (e.g. Ellsworth, 2013 or McGarr, 2014). Many of the risk assessment models is based on the seismological statistics and they use only basic information of the occurrence time and event magnitude. In this study, we originally developed the risk assessment model based on the more physical interpretation of microseismic events. We newly defined new index reffered to as "Slip-able area (SAA)", which describes the cumulative fault areas under critical state in a study area during/after the stimulation. The informations used in estimating SAA were given by the analysis of microseismic events. This model can provide the potentially slip-able area in semi real time nature. SAA can be directly converted into the event magnitude, therefore this model can contribute to the short (one or two days) or middle (week) term the risk assessment of the large seismic event. SAA is defined as simple product of slipped area density and stimulated volume using the equation (1). Aslip=K×Vstimu (1) where Aslip is the cumulative SAA, K is slipped area density, and Vstimuis the stimulated volume by fluid injection. K, slipped area density is defined as the summation of fault areas of the seismic events which occurred during given time step from given volume. Vstimu means the rock volume whose permeability was enhanced by the fluid stimulation. So, Vstimuis estimated by distribution of the hypocenter location. In order to verify the feasibility of this model, SAA is estimated using the microseismic data set from Basel, Switzerland and compared the observed seismic fault area. In this process, slipped area density was calculated using

  13. Effective methods for improving signal/noise ratio of seismic data collected from heavy noisy area

    SciTech Connect

    Chuankun, L. )

    1991-01-01

    This paper reports on the Jiyuan depression which is the hydrocarbon-bearing area discovered earliest in North China. Terribly complicated seismic-geological condition and very heavy multitudinous noises result in very low signal/noise ratio of seismic data in this area, which severely obstructed hydrocarbon exploration in this area. Hence, research of seismic methods for this area has been made systematically. Reasonable seismic data acquisition parameters were determined by making detailed surface-layer analysis and overall field tests, and by designing expert system with the use of spectral analysis data and field operation data. Consequently, special field method (including deep shot hole, big array length, high stacking fold and high low-cut filtering) was adopted to improve raw seismic data obviously. Furthermore, good static correction, correct stack velocity and reasonable prestack two-dimensional filtering were used to remove seismic noise in data processing. The above methods can improve signal/noise ratio and result in qualified seismic data which favor structural and lithologic interpretations.

  14. Local seismic events in area of Poland based on data from PASSEQ 2006-2008 experiment

    NASA Astrophysics Data System (ADS)

    Polkowski, Marcin; Plesiewicz, Beata; Wiszniowski, Jan; Wilde-Piórko, Monika; Passeq Working Group

    2014-05-01

    PASSEQ 2006-2008 (Passive Seismic Experiment in TESZ; Wilde-Piórko et al, 2008) was the biggest so far passive seismic experiment in the area of Central Europe (Poland, Germany, Czech Republic and Lithuania). 196 seismic stations (including 49 broadband seismometers) worked simultaneously for over two years. During experiment multiple types of data recorders and seismometers were used making analysis more complex and time consuming. Dataset was unified and repaired to start the detection of local seismic events. Two different approaches for detection were applied for stations located in Poland. One used standard STA/LTA triggers (Carl Johnson's STA/LTA algorithm) and grid search to classify and locate events. Result was manually verified. Other approach used Real Time Recurrent Network (RTRN) detection (Wiszniowski et al, 2014). Both methods gave similar results showing four previously unknown seismic events located in area of Gulf Of Gdańsk in southern Baltic Sea. The investigation of local seismicity is a good opportunity for verification of new seismic models of lithosphere in the area. In this paper we discuss both detection methods with their pros and cons (accuracy, efficiency, manual work required, scalability). We also show details of all detected and previously unknown events in discussed area. This work was partially supported by NCN grant UMO-2011/01/B/ST10/06653.

  15. Common features and peculiarities of the seismic activity at Phlegraean Fields, Long Valley, and Vesuvius

    USGS Publications Warehouse

    Marzocchi, W.; Vilardo, G.; Hill, D.P.; Ricciardi, G.P.; Ricco, C.

    2001-01-01

    We analyzed and compared the seismic activity that has occurred in the last two to three decades in three distinct volcanic areas: Phlegraean Fields, Italy; Vesuvius, Italy; and Long Valley, California. Our main goal is to identify and discuss common features and peculiarities in the temporal evolution of earthquake sequences that may reflect similarities and differences in the generating processes between these volcanic systems. In particular, we tried to characterize the time series of the number of events and of the seismic energy release in terms of stochastic, deterministic, and chaotic components. The time sequences from each area consist of thousands of earthquakes that allow a detailed quantitative analysis and comparison. The results obtained showed no evidence for either deterministic or chaotic components in the earthquake sequences in Long Valley caldera, which appears to be dominated by stochastic behavior. In contrast, earthquake sequences at Phlegrean Fields and Mount Vesuvius show a deterministic signal mainly consisting of a 24-hour periodicity. Our analysis suggests that the modulation in seismicity is in some way related to thermal diurnal processes, rather than luni-solar tidal effects. Independently from the process that generates these periodicities on the seismicity., it is suggested that the lack (or presence) of diurnal cycles is seismic swarms of volcanic areas could be closely linked to the presence (or lack) of magma motion.

  16. Modern Seismic Observations in the Tatun Volcano Region of Northern Taiwan: Seismic/Volcanic Hazard Adjacent to the Taipei Metropolitan Area

    NASA Astrophysics Data System (ADS)

    Kim, K.; Chang, C.; Ma, K.; Chiu, J.; Chen, K.

    2006-12-01

    The Tatun volcano group is located adjacent to the Taipei metropolitan area in northern Taiwan and was a result of episodic volcanisms between 2.8 and 0.2 Ma. Earthquake data collected over the last 30 years are analyzed to explore seismicity pattern and their associated mechanism of faulting in the area. Using a Joint Hypocenter Determination (JHD) method, a few sequences of relocated earthquake hypocenters are tightly clustered which seem to be blurry in the original catalog locations. Numerous earthquakes, previously unnoticed and not reported in the CWB catalog, have been identified from a careful examination of the continuous recordings from a nearby broadband seismic station. These newly identified earthquakes show similarities in waveforms and arrival time differences between the direct P- and S-waves indicating that their hypocenter locations are very close to each other and their source mechanisms are similar. A relatively high b- value of 1.22 is obtained from the analysis of crustal earthquakes (depth < 30 km) in the region, which may suggest that clustered local seismicity in the Tatun volcanic region probably resulted from subsurface hydrothermal or volcano-related activities. Focal mechanism solutions determined in this study are dominated by normal faulting. Thus, these earthquake clusters are most probably associated with hydrothermal/magmatic activities in a back-arc extensional environment. This work was funded by the Korea Meteorological Administration Research Development Program under Grant CATER 2006-5101.

  17. Seismicity, arrival time delays of the seismic phases and slowness characteristics study in Abu Dabbab area, Egypt

    NASA Astrophysics Data System (ADS)

    Sami, Mahmoud; Hassoup, Awad; Hosny, Ahmed; Mohamed, Gadelkarem A.

    2013-12-01

    The temporal variations of seismicity from the Abu Dabbab area, 25 km west of the Red Sea coast, are collected from the Egyptian national seismic network (ENSN), which has magnified the detection capability in that area to ML < 1 earthquakes. These data show a sequence of the micro earthquake swarm during 2003-2011. This area has experienced larger shocks up to M = 6 during the 20th century and its seismicity is concentrated in a narrow spatial volume. We analyze the digital waveform data of about 1000 seismograms, recorded by portable network of 10 vertical component seismographs that are employed in a temporary survey experiment in the Abu Dabbab area in 2004, and the results indicate: firstly, there are similar waveform seismograms, which are classified into three groups. In each group a master event is identified. Then, the arrival time delays of the P and S phases (Δtp and Δts, respectively) are measured between the master event and its slave events. Δtp and Δts range between -0.01 and 0.02 s, respectively. These values are used to relocate the studied events. Secondly, the slowness vector (Δs) in 3-dimensional pattern, which is estimated using the genetic algorithms, is found Δsx = 0.0153, Δsy = 0.00093 and Δsz = 0.2086 s/km in the three spatial coordinates (X, Y and Z), respectively. These analyses demonstrate the inhomogeneities within the upper crust of the study area. Also, Δs shows little dependence of lateral distances and reasonably high slowness along the depth extent, which is consistent with the seismic velocity structure variations.

  18. Seismic microzoning in the metropolitan area of Port - au-Prince - complexity of the subsoil

    NASA Astrophysics Data System (ADS)

    Gilles, R.; Bertil, D.; Belvaux, M.; Roulle, A.; Noury, G.; Prepetit, C.; Jean-Philippe, J.

    2013-12-01

    The magnitude 7.3 earthquake that struck Haiti in January 12, 2010 has caused a lot of damages in surrounding areas epicenter. These damages are due to a lack of knowledge of the Haitian subsoil. To overcome this problem, the LNBTP, the BME and BRGM have agreed to implement a project of seismic microzonation of the metropolitan area of Port-au-Prince which is financed by the Fund for the reconstruction of the country. The seismic microzonation is an important tool for knowledge of seismic risk. It is based on a collection of geological, geotechnical, geophysical and measures and recognition and the campaign of numerous sites. It describes a class of specific soils with associated spectral response. The objective of the microzoning is to identify and map the homogeneous zones of lithology, topography, liquefaction and ground movements. The zoning of lithological sites effect is to identify and map areas with geological and geomechanical consistent and homogeneous seismic response; the objective is to provide, in each area, seismic movements adapted to the ground. This zoning is done in about five steps: 1- Cross-analysis of geological, geotechnical and geophysical information; 2- Such information comprise the existing data collected and the data acquired during the project; 3- Identification of homogeneous areas. 4- Definition of one or more columns of representative soils associated with each zone; 5 - Possible consolidation of area to get the final seismic zoning. 27 zones types were considered for the study of sites effects after the analysis of all geological, geotechnical and geophysical data. For example, for the formation of Delmas, there are 5 areas with soil classes ranging from D to C. Soil columns described in the metropolitan area of Port-au-Prince are processed with the CyberQuake software, which is developed at the BRGM by Modaressi et al. in 1997, to calculate their response to seismic rock solicitation. The seismic motion is determined by 4

  19. Tracking hydrothermal feature changes in response to seismicity and deformation at Mud Volcano thermal area, Yellowstone

    NASA Astrophysics Data System (ADS)

    Diefenbach, A. K.; Hurwitz, S.; Murphy, F.; Evans, W.

    2013-12-01

    The Mud Volcano thermal area in Yellowstone National Park comprises many hydrothermal features including fumaroles, mudpots, springs, and thermal pools. Observations of hydrothermal changes have been made for decades in the Mud Volcano thermal area, and include reports of significant changes (the appearance of new features, increased water levels in pools, vigor of activity, and tree mortality) following an earthquake swarm in 1978 that took place beneath the area. However, no quantitative method to map and measure surface feature changes through time has been applied. We present an analysis of aerial photographs from 1954 to present to track temporal changes in the boundaries between vegetated and thermally barren areas, as well as location, extent, color, clarity, and runoff patterns of hydrothermal features within the Mud Volcano thermal area. This study attempts to provide a detailed, long-term (>50 year) inventory of hydrothermal features and change detection at Mud Volcano thermal area that can be used to identify changes in hydrothermal activity in response to seismicity, uplift and subsidence episodes of the adjacent Sour Creek resurgent dome, or other potential causes.

  20. Time-dependent seismic tomography and its application to the Coso geothermal area, 1996-2006

    SciTech Connect

    Julian, B.R.; G.R. Foulger; F. Monastero

    2008-04-01

    Measurements of temporal changes in Earth structure are commonly determined using localearthquake tomography computer programs that invert multiple seismic-wave arrival time data sets separately and assume that any differences in the structural results arise from real temporal variations. This assumption is dangerous because the results of repeated tomography experiments would differ even if the structure did not change, simply because of variation in the seismic ray distribution caused by the natural variation in earthquake locations. Even if the source locations did not change (if only explosion data were used, for example), derived structures would inevitably differ because of observational errors. A better approach is to invert multiple data sets simultaneously, which makes it possible to determine what changes are truly required by the data. This problem is similar to that of seeking models consistent with initial assumptions, and techniques similar to the “damped least squares” method can solve it. We have developed a computer program, dtomo, that inverts multiple epochs of arrival-time measurements to determine hypocentral parameters and structural changes between epochs. We shall apply this program to data from the seismically active Coso geothermal area, California, in the near future. The permanent network operated there by the US Navy, supplemented by temporary stations, has provided excellent earthquake arrival-time data covering a span of more than a decade. Furthermore, structural change is expected in the area as a result of geothermal exploitation of the resource. We have studied the period 1996 through 2006. Our results to date using the traditional method show, for a 2-km horizontal grid spacing, an irregular strengthening with time of a negative VP/VS anomaly in the upper ~ 2 km of the reservoir. This progressive reduction in VP/VS results predominately from an increase of VS with respect to VP. Such a change is expected to result from

  1. Explosively activated egress area

    NASA Technical Reports Server (NTRS)

    Bement, L. J.; Bailey, J. W. (Inventor)

    1983-01-01

    A lightweight, add on structure which employs linear shaped pyrotechnic charges to smoothly cut an airframe along an egress area periphery is provided. It compromises reaction surfaces attached to the exterior surface of the airframe's skin and is designed to restrict the skin deflection. That portion of the airframe within the egress area periphery is jettisoned. Retention surfaces and sealing walls are attached to the interior surface of the airframe's skin and are designed to shield the interior of the aircraft during detonation of the pyrotechnic charges.

  2. Seismic imaging of mantle transition zone discontinuities beneath the northern Red Sea and adjacent areas

    NASA Astrophysics Data System (ADS)

    Mohamed, A. A.; Gao, S. S.; Elsheikh, A. A.; Liu, K. H.; Yu, Y.; Fat-Helbary, R. E.

    2014-11-01

    The dramatic asymmetry in terms of surface elevation, Cenozoic volcanisms and earthquake activity across the Red Sea is an enigmatic issue in global tectonics, partially due to the unavailability of broad-band seismic data on the African Plate adjacent to the Red Sea. Here, we report the first comprehensive image of the mantle transition zone (MTZ) discontinuities using data from the Egyptian National Seismic Network, and compare the resulting depths of the 410 and 660-km discontinuities with those observed on the Arabian side. Our results show that when a standard earth model is used for time-to-depth conversion, the resulting depth of the discontinuities increases systematically towards the axis of the Afro-Arabian Dome (AAD) from both the west and east. Relative to the westernmost area, the maximum depression of the 410-km discontinuity is about 30 km, and that of the 660-km discontinuity is about 45 km. The observed systematic variations can best be explained by a model involving a hydrated MTZ and an upper-mantle low-velocity zone beneath the AAD. Models invoking one or more mantle plumes originated from the MTZ or the lower-mantle beneath the study area are not consistent with the observations.

  3. Study of Seismic Activity at Ceboruco Volcano, Mexico

    NASA Astrophysics Data System (ADS)

    Nunez-Cornu, F. J.; Escudero, C. R.; Rodríguez Ayala, N. A.; Suarez-Plascencia, C.

    2013-12-01

    Many societies and their economies endure the disastrous consequences of destructive volcanic eruptions. The Ceboruco stratovolcano (2,280 m.a.s.l.) is located in Nayarit, Mexico, at the west of the Mexican volcanic belt and towards the Sierra de San Pedro southeast, which is a key communication point for coast of Jalisco and Nayarit and the northwest of Mexico. It last eruptive activity was in 1875, and during the following five years it presents superficial activity such as vapor emissions, ash falls and riodacitic composition lava flows along the southeast side. Although surface activity has been restricted to fumaroles near the summit, Ceboruco exhibits regular seismic unrest characterized by both low frequency seismic events and volcano-tectonic earthquakes. From March 2003 until July 2008 a three-component short-period seismograph Marslite station with a Lennartz 3D (1Hz) was deployed in the south flank (CEBN) and within 2 km from the summit to monitoring the seismic activity at the volcano. The LF seismicity recorded was classified using waveform characteristics and digital analysis. We obtained four groups: impulsive arrivals, extended coda, bobbin form, and wave package amplitude modulation earthquakes. The extended coda is the group with more earthquakes and present durations of 50 seconds. Using the moving particle technique, we read the P and S wave arrival times and estimate azimuth arrivals. A P-wave velocity of 3.0 km/s was used to locate the earthquakes, most of the hypocenters are below the volcanic edifice within a circular perimeter of 5 km of radius and its depths are calculated relative to the CEBN elevation as follows. The impulsive arrivals earthquakes present hypocenters between 0 and 1 km while the other groups between 0 and 4 km. Results suggest fluid activity inside the volcanic building that could be related to fumes on the volcano. We conclude that the Ceboruco volcano is active. Therefore, it should be continuously monitored due to the

  4. First Arrival Seismic Tomography (FAST) vs. PStomo_eq applied to crooked line seismic data from the Siljan ring area

    NASA Astrophysics Data System (ADS)

    Rodríguez-Tablante, Johiris I.; Juhlin, Christopher; Bergman, Björn

    2006-05-01

    When seismic profiles deviate significantly from straight lines, the results from 2D traveltime inversion programs will be in error due to the inherent 3D component present in the data. Thus, it is necessary to use a program that can handle the 3D aspects of the acquisition geometry. This study compares the performance and results from two computer programs for 3D seismic tomography. These algorithms are the package for First Arrival Seismic Tomography (FAST) and a Local Earthquake tomography program, PStomo_eq. Although both codes invert for the velocity field using the conjugate gradient solver LSQR, the common smoothness constraint is handled differently. In addition, the programs do not incorporate the same options for user-specified constraints. These differences in implementation are clearly observed in the inverted velocity fields obtained in this study. Both FAST and PStomo_eq are applied to synthetic and real data sets with crooked line geometry. First arrival traveltimes from seismic data acquired in the Siljan ring impact area are used for the real data set test. The results show that FAST gives smoother models than PStomo_eq. On the real data set PStomo_eq showed a better correlation to the information at hand. Different criteria exist for what is desirable in a model; thus, the choice of which program to use will mostly depend on the particular goals of the study.

  5. The 3D crustal structure of Northeastern Tibetan area from seismic tomography

    NASA Astrophysics Data System (ADS)

    Sun, Anhui

    2015-04-01

    The Northeastern Tibetan region is located in the border area of three sub-plates in China, i.e. the Tibetan plateau, North China block and Xinjiang block. Effected simultaneously by the extrusion driven by the India-Eurasia plat collision and the blockage of the Ordos basin, this area has complex geology, strong tectonics activities and suffered from several large historic earthquakes, such as the Haiyuan earthquake (M8.6) in 1920, the Gulang earthquake (M8.0) in 1927. To enhance our understanding of the crustal structure and the interaction between different tectonic blocks of this region, we conduct a three-dimensional (3D) tomographic study by using the arrival time date recorded by regional seismic network. We used 101101 P and 103313 S wave arrival times from 11650 local earthquakes during 1970 to 2013 recorded by 154 permanent seismic stations of the local Seismic Network, installed over five provinces in China, i.e. Gansu, Ningxia, Qinghai, Shanxi, Neimenggu. We first established a 1D primary crustal model from LITHO1.0, an updated crust and lithospheric model of the Earth by weighted averaging. To better performer ray tracing, our inversion involved three discontinuities (including the Moho) with depth variation over the mantle derived from LITHO1.0. Detailed three-dimensional seismic velocity (Vp and Vs) structures of the crust of the Northeastern Tibetan are determined with a horizontal resolution of about 35 km and a depth resolution of 6-20 km. The Poisson's ratio (σ) structure was also estimated after obtained Vp and Vs structures. We detected low-velocity anomalies in the lower crust and relative high-velocity anomalies in the upper crust beneath the Longmenshan faults zone, which are in good agreement with the results of most previous geophysical studies. Our results revealed clear different velocity variation beneath both sides of different tectonic blocks. In addition, we found the correlation between our tomographic result and previous

  6. Deep seismic transect across the Tonankai earthquake area obtained from the onshore- offshore wide-angle seismic study

    NASA Astrophysics Data System (ADS)

    Nakanishi, A.; Obana, K.; Kodaira, S.; Miura, S.; Fujie, G.; Ito, A.; Sato, T.; Park, J.; Kaneda, Y.; Ito, K.; Iwasaki, T.

    2008-12-01

    In the Nankai Trough subduction seismogenic zone, M8-class great earthquake area can be divided into three segments; they are source regions of the Nankai, Tonankai and presumed Tokai earthquakes. The Nankai and Tonankai earthquakes had often occurred simultaneously, and caused a great event. Hypocenters of these great earthquakes were usually located off the cape Shiono, Kii Peninsula, and the rupture propagated westwards and eastwards, respectively. To obtain the deep structure of the down-dip limit of around the Nankai Trough seismogenic zone, the segment boundary and first break area off the Kii Peninsula, the onshore-offshore wide-angle seismic studies was conducted in the western and eastern part of the Kii Peninsula and their offshore area in 2004 and 2006, respectively. The result of the seismic study in 2004 is mainly shown here. Structural images along the onshore and offshore profiles have already been separately obtained. In this study, an onshore-offshore integrated image of the western part of the Kii Peninsula, ~400km in a total length, is obtained from first arrival tomography and traveltime mapping of reflection phases by combining dataset of 13 land explosions, 2269 land stations, 36 OBSs and 1806 offshore airgun shots. The subduction angle of the Philippine Sea plate (PSP) gradually increases landward up to ~20-25 degree. Beneath the onshore part, the subducting PSP is estimated at ~5km shallower than that previously derived from seismicity. Low frequency earthquakes (identified and picked by Japan Meteorological Agency) are relocated around the plate interface of the subducting PSP by using the deep seismic transect obtained in this study. The offshore research is part of 'Structure research on plate dynamics of the presumed rupture zone of the Tonankai-Nankai Earthquakes' funded by Ministry of Education, Culture, Sports, Science and Technology (MEXT). The onshore research carried by the Kyoto University is part of 'Special Project for

  7. Development of urban planning guidelines for improving emergency response capacities in seismic areas of Iran.

    PubMed

    Hosseini, Kambod Amini; Jafari, Mohammad Kazem; Hosseini, Maziar; Mansouri, Babak; Hosseinioon, Solmaz

    2009-10-01

    This paper presents the results of research carried out to improve emergency response activities in earthquake-prone areas of Iran. The research concentrated on emergency response operations, emergency medical care, emergency transportation, and evacuation-the most important issues after an earthquake with regard to saving the lives of victims. For each topic, some guidelines and criteria are presented for enhancing emergency response activities, based on evaluations of experience of strong earthquakes that have occurred over the past two decades in Iran, notably Manjil (1990), Bam (2003), Firouz Abad-Kojour (2004), Zarand (2005) and Broujerd (2006). These guidelines and criteria are applicable to other national contexts, especially countries with similar seismic and social conditions as Iran. The results of this study should be incorporated into comprehensive plans to ensure sustainable development or reconstruction of cities as well as to augment the efficiency of emergency response after an earthquake. PMID:19500324

  8. An active seismic experiment proposal onboard the NASA 2009 MSL

    NASA Astrophysics Data System (ADS)

    Lognonné, P.; Experiment Team

    NASA will launch in 2009 a 900 kg class rover to Mars. This rover will land with a new descent system, called the ``sky-crane''. After releasing the rover on the ground, the sky-crane will have a final flight until a hard landing about 2 km away from the rover. The science objectives of the 2009 MSL mission, among others, are to characterize the geology of the landing region at all appropriate spatial scales, to interpret the processes that have formed and modified rocks and regolith and to determine present state, distribution, and cycling of water. We propose to perform with the sky-crane an active seismic experiment for subsurface characterization. This experiment will be conducted after the rover deployment. The proposed idea is to deploy a seismic receiver line by ejecting about 10 seismic nodes from the sky-crane and then to record then the reflected signals from the impact of the sky-crane. Preliminary modeling and tests indicate that a penetration depth of several hundred meters will be reached. The experiment will be used to determine a 2D geological profile of the landing site subsurface, to determine the depth and shape of the dry regolith/icy regolith discontinuity and to identify possible layering structures in the subsurface. In addition, information on the structure of the regolith (mean size of building blocs) and on the presence of liquid water will be obtained by an analysis of the seismic coda and attenuation. The seismic high frequency noise will also be monitored, especially during windy periods, and will be used to get additional information on the subsurface. The proposed experiment is based on a consortium between academics laboratories and seismic industry and will be a first example of a resource oriented experiment on another planet than Earth. The complete mass of the experiment will be 2.5 kg. Seismic nodes will have their own acquisition/power and telemetry system and will be based on high sensitive geophones developed for seismic

  9. Testing the recent Santorini seismic activity for possible tidal triggering effect

    NASA Astrophysics Data System (ADS)

    Contadakis, Michael E.; Arabelos, Dimitrios N.; Vergos, George

    2013-04-01

    Applying the Hi(stogram)Cum(ulation) method, which was introduced recently by Cadicheanu, van Ruymbecke and Zhu (2007), we analyze the series of the earthquakes occurred in the last 50 years in seismic active areas of Greece, i.e. the areas (a) of the Mygdonian Basin(Contadakis et al. 2007), (b) of the Ionian Islands (Contadakis et al. 2012 ) and (c) of the Hellenic Arc (Vergos et al. 2012 ). The result of the analysis for all the areas indicate that the monthly variation of the frequencies of earthquake occurrence is in accordance with the period of the tidal lunar monthly and semi-monthly (Mm and Mf) variations and the same happens with the corresponding daily variations of the frequencies of earthquake occurrence with the diurnal luni-solar (K1) and semidiurnal lunar (M2) tidal variations. In addition the confidence level for the identification of such period accordance between earthquakes occurrence frequency and tidal periods varies with seismic activity, i.e. the higher confidence level corresponds to periods with stronger seismic activity. These results are in favor of a tidal triggering process on earthquakes when the stress in the focal area is near the critical level. Based on these results, we consider the confidence level of earthquake occurrence - tidal period accordance as an index of tectonic stress criticality for earthquake occurrence and we check if the recent increase in the seismic activity at the Santorini island complex indicate that the faults Kameni and Columbo (to which the seismicity is clustered) (Chouliaras et al. 2013) are mature for a stronger earthquake. In this paper we present the results of this test. References Cadicheanu, N., van Ruymbeke, M andZhu P.,2007:Tidal triggering evidence of intermediate depth earthquakes in Vrancea zone(Romania), NHESS 7,733-740. Contadakis, M. E., Arabelos, D. N., Spatalas, S., 2009, Evidence for tidal triggering on the shallow earthquakes of the seismic area of Mygdonia basin, North Greece, in

  10. Seismic sequence near Zakynthos Island, Greece, April 2006: Identification of the activated fault plane

    NASA Astrophysics Data System (ADS)

    Serpetsidaki, A.; Sokos, E.; Tselentis, G.-A.; Zahradnik, J.

    2010-01-01

    The April 2006 earthquake sequence near Zakynthos (Western Greece) is analysed to identify the fault plane(-s). The sequence (33 events) was relocated to assess physical insight into the hypocenter uncertainty. Moment tensor solution of three major events was performed, simultaneously with the determination of the centroid position. Joint analysis of the hypocenter position, centroid position and nodal planes indicated sub-horizontal fault planes. Moment tensor solutions of 15 smaller events were performed under assumption that the source positions are those of the hypocenters (without seeking centroids). Their focal mechanisms are highly similar and agree with the analysis of the three major events. The preferable seismotectonic interpretation is that the whole sequence activated a single sub-horizontal fault zone at a depth of about 13 km, corresponding to the interplate subduction boundary. Considering that the Ionian Sea is a high-seismicity area, the identification of the seismic fault is significant for the seismic hazard investigation of the region.

  11. Elevated shear strength of sediments on active margins: Evidence for seismic strengthening

    NASA Astrophysics Data System (ADS)

    Sawyer, Derek E.; DeVore, Joshua R.

    2015-12-01

    Earthquakes are a primary trigger of submarine landslides, yet some of the most seismically active areas on Earth show a surprisingly low frequency of submarine landslides. Here we show that within the uppermost 100 m below seafloor (mbsf) in previously unfailed sediment, active margins have elevated shear strength by a factor of 2-3 relative to the same interval on passive margins. The elevated shear strength is seen in a global survey of undrained shear strength with depth as well as a normalized analysis that accounts for lithology and stress state. The enhanced shear strength is highest within the uppermost 10 mbsf. These results indicate that large areas of modern day slopes on active margins have enhanced slope stability, which may explain the relative paucity of landslides. These findings lend support to the seismic strengthening hypothesis that the repeated exposure to earthquake energy gradually increases shear strength by shear-induced compaction.

  12. Seismic Hazard Analysis in EL Paso/juarez Area from Study of Young Fault Scarps

    NASA Astrophysics Data System (ADS)

    ashenfelter, K. R.

    2012-12-01

    The El Paso-Juarez metropolitan area contains a known record of active faulting, but also has one of the most poorly known paleoseismic records. The scarcity of data means that nearly 2 million people are exposed to a seismic hazard with little known on the actual risk. Active faults are known along the eastern side of the Franklin Mountains as well as young ruptures within the Hueco Bolson in East El Paso, yet the only fault with paleoseismic studies is the East Franklin's fault. Recent population increases in the El Paso region have led to a construction boom in east El Paso, and many of these construction sites cross known Quaternary fault ruptures. This research project contains two potential components: 1) An exploratory component: students can use existing fault maps and high resolution aerial photography to seek out sites where active construction sites might be unearthing exposures of young fault ruptures. The study is exploratory, and involves carefully mapping using field GIS systems to document areas for potential study, map possible faults, etc. 2) An active fault study in an urbanized environment: The east Franklins fault is a known active fault. The scarp is exposed near trans-mountain road, and along some side streets in NE El Paso. Potential studies include careful mapping of fault scarp topographic profiles, and mapping surface traces.

  13. Active Monitoring With The Use Of Seismic Vibrators: Experimental Systems And The Results Of Works

    NASA Astrophysics Data System (ADS)

    Kovalevsky, V.; Alekseev, A.; Glinsky, B.; Khairetdinov, M.; Seleznev, V.; Emanov, A.; Soloviev, V.

    2004-12-01

    -5 - 10-6 in an area of 300-400 km around the source. This makes possible the direct monitoring of the state of stresses in an area of 100 thousand km2 to detect the regions and phases of the critical stress as an earthquake precursor. In recent years, works on the use of the method of vibroseismic interferometry for the active monitoring of the lake Baikal region have been started. The method is based on the seismic sounding of the region by powerful seismic vibrators with a long radiation of narrow-band harmonic signals. The changes in the stressed-deformed state are determined through the variations of the amplitude-phase characteristics of stationary wave fields, which are excited in the medium due to a long-time radiation of harmonic signals of constant frequency from the vibrator. The method of vibroseismic interferometry has a high sensitivity to the time changes of the parameters of the medium in the case of long-distance observations. A peculiarity of the experiments is the simultaneous use of the data of regional seismic stations and mobile recording complexes.

  14. Fault Activity Investigations in the Lower Tagus Valley (Portugal) With Seismic and Geoelectric Methods

    NASA Astrophysics Data System (ADS)

    Carvalho, J. G.; Gonçalves, R.; Torres, L. M.; Cabral, J.; Mendes-Victor, L. A.

    2004-05-01

    The Lower Tagus River Valley is located in Central Portugal, and includes a large portion of the densely populated area of Lisbon. It is sited in the Lower Tagus Cenozoic Basin, a tectonic depression where up to 2,000 m of Cenozoic sediments are preserved, which was developed in the Neogene as a compressive foredeep basin related to tectonic inversion of former Mesozoic extensional structures. It is only a few hundred kilometers distant from the Eurasia-Africa plate boundary, and is characterized by a moderate seismicity presenting a diffuse pattern, with historical earthquakes having caused serious damage, loss of lives and economical problems. It has therefore been the target of several seismic hazard studies in which extensive geological and geophysical research was carried out on several geological structures. This work focuses on the application of seismic and geoelectric methods to investigate an important NW-SE trending normal fault detected on deep oil-industry seismic reflection profiles in the Tagus Cenozoic Basin. In these seismic sections this fault clearly offsets horizons that are ascribed to the Upper Miocene. However, due to the poor near surface resolution of the seismic data and the fact that the fault is hidden under the recent alluvial cover of the Tagus River, it was not clear whether it displaced the upper sediments of Holocene age. In order to constrain the fault geometry and kinematics and to evaluate its recent tectonic activity, a few high-resolution seismic reflection profiles were acquired and refraction interpretation of the reflection data was performed. Some vertical electrical soundings were also carried out. A complex fault system was detected, apparently with normal and reverse faulting. The collected data strongly supports the possibility that one of the detected faults affects the uppermost Neogene sediments and very probably the Holocene alluvial sediments of the Tagus River. The evidence of recent activity on this fault, its

  15. Near-Surface Site Characterization Using a Combination of Active and Passive Seismic Arrays

    NASA Astrophysics Data System (ADS)

    Lane, J. W.; Liu, L.; Chen, Y.; White, E. A.

    2007-12-01

    Seismic surveys with an active source are commonly used to characterize the subsurface. Increasingly, passive seismic surveys utilizing ambient seismic frequencies (microtremors) are being used to support geotechnical and hazards engineering studies. In this study, we use a combination of active and passive seismic methods to characterize a watershed site at Haddam Meadows State Park, Haddam, Connecticut. At Haddam Meadows, we employed a number of seismic arrays using both active and passive approaches to estimate the depth to rock and the seismic velocity structure of the unconsolidated sediments. The active seismic surveys included seismic refraction and multi-channel analysis of surface waves (MASW) using an accelerated weight-drop seismic source. The passive seismic surveys consisted of MASW techniques using both linear and circular geophone arrays, and a survey using a 3-component seismometer. The active seismic data were processed using conventional algorithms; the passive seismic data were processed using both the spatial autocorrelation method (SPAC) and the horizontal to vertical spectral ratio (H/V) method. The interpretations of subsurface structure from the active and passive surveys are generally in good agreement and compare favorably with ground truth information provided by adjacent boreholes. Our results suggest that a combination of active and passive seismic methods can be used to rapidly characterize the subsurface at the watershed scale.

  16. Seismicity characteristics of a potentially active Quaternary volcano: The Tatun Volcano Group, northern Taiwan

    NASA Astrophysics Data System (ADS)

    Konstantinou, Konstantinos I.; Lin, Cheng-Horng; Liang, Wen-Tzong

    2007-02-01

    The Tatun Volcano Group (TVG) is located at the northern tip of Taiwan, near the capital Taipei and close to two nuclear power plants. Because of lack of any activity in historical times it has been classified as an extinct volcano, even though more recent studies suggest that TVG might have been active during the last 20 ka. In May 2003 a seismic monitoring project at the TVG area was initiated by deploying eight three-component seismic stations some of them equipped with both short-period and broadband sensors. During the 18 months observation period local seismicity mainly consisted of high frequency earthquakes either occurring as isolated events, or as a continuous sequence in the form of spasmodic bursts. Mixed and low frequency events were also present during the same period, even though they occurred only rarely. Arrival times from events with clear P-/S-wave phases were inverted in order to obtain a minimum 1D velocity model with station corrections. Probabilistic nonlinear earthquake locations were calculated for all these events using the newly derived velocity model. Most high frequency seismicity appeared to be concentrated near the areas of hydrothermal activity, forming tight clusters at depths shallower than 4 km. Relative locations, calculated using the double-difference method and utilising catalogue and cross-correlation differential traveltimes, showed insignificant differences when compared to the nonlinear probabilistic locations. In general, seismicity in the TVG area seems to be primarily driven by circulation of hydrothermal fluids as indicated by the occurrence of spasmodic bursts, mixed/low frequency events and a b-value (1.17 ± 0.1) higher than in any other part of Taiwan. These observations, that are similar to those reported in other dormant Quaternary volcanoes, indicate that a magma chamber may still exist beneath TVG and that a future eruption or period of unrest should not be considered unlikely.

  17. Seismic Microzonation of Urban areas in India - A case study from Jabalpur, Central India (Invited)

    NASA Astrophysics Data System (ADS)

    Rao, N. P.

    2009-12-01

    The Indian subcontinent is seismically one of the most active regions in the world, having experienced four earthquakes of magnitude greater than 8.0 during the last century. This has necessitated detailed Seismic Microzonation approaches for assessment of seismic hazard and risk potential of several highly populated Indian mega-cities that face the wrath of future earthquakes. A multi-disciplinary and multi-Institutional pilot study was launched in the Jabalpur urban area in Central India for a realistic assessment of seismic hazard and the associated risk to the region. Ground amplification at local sites in the frequency range of 0.1 - 10 Hz was obtained at more than 100 sites in and around Jabalpur using the conventional Nakamura technique to estimate the predominant frequencies and the site amplification at those frequencies for each site. A strong correlation is seen between the predominant frequencies and the ground conditions, like the local geology, the composition of the top soil cover, its thickness and impedance contrast with respect to the basement, etc. To validate these results, Multichannel Analysis of Surface Waves (MASW) technique was adopted, coupled with refraction measurements over short profiles (~100m). This has resulted in detailed shear velocity images of the shallow subsurface, which are crucial for estimation of the amplification of seismic signals propagating through the medium. Based on these results synthetic seismograms were generated using a hybrid method comprising normal mode summation for the regional 1D structure and the Finite difference approach for site specific 2D structure of the medium. Local site amplifications expressed as the Response Spectral Ratios (RSR) - the ratio of 2D to 1D ground acceleration response - were estimated. In general, the RSR values correlated well with the composition and thickness of the upper soil cover. The alluvial filled region in the northwestern part of Jabalpur having soil thickness up to 30

  18. Seismic activity in the Sunnyside mining district, Carbon and Emery Counties, Utah, during 1968

    USGS Publications Warehouse

    Dunrud, C. Richard; Maberry, John O.; Hernandez, Jerome H.

    1970-01-01

    More than 20,000 local earth tremors were recorded by the seismic monitoring network in the Sunnyside mining district during 1968. This is about 40 percent of the number of tremors recorded by the network in 1967. In 1968 a total of 281 tremors were of sufficient magnitude to be located accurately--about 50 percent of the number of tremors in 1967 that were located accurately. As in previous years, nearly all the earth tremors originated near, or within a few thousand feet of, the mine workings. This distribution indicates that mine-induced stress changes caused most of the seismic activity. However, over periods of weeks and months there were significant changes in the distribution of seismic activity caused by tremors that were not directly related to mining but probably were caused by adjustment of natural stresses 6r by a complex combination of both natural and mine-induced stress changes. In 1968 the distribution of tremor hypocenters varied considerably with time, relative to active mining areas and to faults present in the mine workings. During the first 6 months, most tremors originated along or near faults that trend close to or through the active mine workings. However, in the last 6 months, the tremor hypocenters tended to concentrate in the rock mass closer to, or around, the active mining areas. This shift in concentration of seismic activity with time has been noted throughout the district many times since recording began in 1963, and is apparently caused by spontaneous releases of stored strain energy resulting from mine-induced stress changes. These spontaneous releases of strain energy, together with rock creep, apparently are the mechanism of adjustment within the rock mass toward equilibrium conditions, which are continually disrupted by mining. Although potentially hazardous bumps were rare in the Sunnyside mining district during 1968, smaller bumps and rock falls were more common in a given active mining area whenever hypocenters of larger

  19. Seismic Evidence for an Active Southern Rio Grande Rift

    NASA Astrophysics Data System (ADS)

    Thompson, L. E.; Velasco, A. A.

    2010-12-01

    Competing models exist to explain what caused the Earth’s crust to spread apart 29 million years ago to create a region known today as the Rio Grande Rift (RGR). The RGR extends from central Colorado through New Mexico to northern Mexico, near El Paso. A growing body of evidence shows that geologic activity still occurs in the RGR, with a continuation of faulting, seismicity and a small widening rate. We map of the seismic velocity structure and crustal thickness using data from the Rio Grande Rift Seismic TRAnsect (RISTRA) experiment and the EarthScope Transportable Array (USArray) dataset. In addition to the data we collected from the RISTRA experiment and USArray dataset, we also acquired receiver functions from the EarthScope Automatic Receiver Survey (EARS) website (http://www.earthscope.org/data) and waveform data from the Incorporated Research Institutes for Seismology (IRIS) Data Management Center (DMC). In particular, we requested seismograms from the IRIS DMC database where we acquired teleseismic events from Jan 2000 to Dec 2009. This includes 7,259 seismic events with a minimum magnitude of 5.5 and 106,389 continuous waveforms. This data was preprocessed (merged, rotated) using a program called Standing Order of Data (SOD). We computed receiver functions and receiver function stacks for all data in the Southern Rio Grande Rift (SRGR). We map the crustal thickness, seismic velocity, and mantle structure to better determine the nature of tectonic activity that is presently taking place and further investigate the regional extension of the Southern Rio Grande Rift (SRGR). Here we present results of the crustal and velocity structure using the kriging interpolation scheme and interpret our results in relation to southern RGR deformation and extension.

  20. A New Standard Installation Method of the Offline Seismic Observation Station in Heavy Snowfall Area of Tohoku Region

    NASA Astrophysics Data System (ADS)

    Hirahara, S.; Nakayama, T.; Hori, S.; Sato, T.; Chiba, Y.; Okada, T.; Matsuzawa, T.

    2015-12-01

    Soon after the 2011 Tohoku earthquake, seismic activity of Tohoku region, NE Japan is induced in the inland area of Akita prefecture and the border area between Fukushima and Yamagata prefectures. We plan to install a total of 80 offline seismic observation stations in these areas for studying the effect of megathrust earthquake on the activities of inland earthquakes. In our project, maintenance will be held twice-a-year for 4 years from 2015 by using 2.0Hz short-period 3-component seismometer, KVS-300 and ultra-low-power data logger, EDR-X7000 (DC12V 0.08W power supply). We installed seismometer on the rock surface or the slope of the natural ground at the possible sites confirmed with low noise level to obtain distinct seismic waveform data. We report an improvement in installation method of the offline seismic observation station in the heavy snowfall area of Tohoku region based on the retrieved data. In the conventional method, seismometer was installed in the hand-dug hole of a slope in case it is not waterproof. Data logger and battery were installed in the box container on the ground surface, and then, GPS antenna was installed on the pole fixed by stepladder. There are risks of the inclination of seismometer and the damage of equipment in heavy snowfall area. In the new method, seismometer is installed in the robust concrete box on the buried basement consists of precast concrete mass to keep its horizontality. Data logger, battery, and GPS antenna are installed on a high place by using a single pole with anchor bolt and a pole mount cabinet to enhance their safety. As a result, total costs of installation are kept down because most of the equipment is reusable. Furthermore, an environmental burden of waste products is reduced.

  1. Comparison of Active and Passive Seismic Methods for Calculating Shear-wave Velocity Profiles: An Example from Hartford County, Connecticut

    NASA Astrophysics Data System (ADS)

    Morton, S.; Lane, J. W.; Liu, L.; Thomas, M. A.

    2013-12-01

    Seismic hazard classifications have been developed for Hartford County, Connecticut based primarily on mapping of surficial materials and depositional environment using criteria specified by the National Earthquake Hazard Reduction Program (NEHRP). A study using near-surface seismic techniques to measure shear-wave velocities in Connecticut was initiated in support of broader seismic hazard mapping efforts undertaken by New England State Geologists. Thirty field sites in Hartford County representative of the range of mapped seismic hazard classes were chosen based on the availability of boring logs and adequate open space for the geophysical surveys. Because it can be difficult to acquire multi-channel seismic data in urban areas due to unwanted noise and open space restrictions, we also investigated the use of passive single-station seismometer measurements as a compact supplement and potential alternative to long-offset multi-channel measurements. Here we compare the results of active-source multi-channel analysis of surface waves (MASW) and passive horizontal-to-vertical spectral ratio (HVSR) seismic methods to determine shear-wave velocity profiles and seismic hazard classification based on Vs30 in glacial sediments throughout Hartford County, Connecticut. HVSR-derived seismic resonances were used as a constraint during inversion of the MASW dispersion curve to reduce model misfit and improve model comparison to site lithology.

  2. Seismic constraints on Late Mesozoic magmatic plumbing system in the onshore-offshore area of Hong Kong

    NASA Astrophysics Data System (ADS)

    Xia, S.; Qiu, X.; Wan, K.

    2015-12-01

    We used active source wide-angle seismic data to determine a crustal structure beneath the onshore-offshore area of Hong Kong at the southern end of a broad belt dominated by Late Mesozoic intrusive and extrusive rocks in the coastal region of Southeast China. High-resolution tomographic images provide direct seismic evidence for the magmatic plumbing system of Late Mesozoic calderas. A localized high-velocity anomaly is revealed in the lower crust offshore between Hong Kong and Dangan Island, which may reflect basaltic underplating that induced voluminous silicic eruptions and granitoid plutons in the onshore-offshore area of Hong Kong. Tilted high-velocity zones are revealed in the entire crust beneath Dangan Island and the Late Mesozoic calderas of Hong Kong, which may reflect ascending magma chambers. We propose a paleo-Pacific plate subduction model to interpret our tomographic results and the generation of strong granitic magmatism in the Hong Kong area. Combining the tomographic image beneath the Lianhuashan Fault Zone with the distribution of Late Mesozoic calderas, we infer that the Lianhuashan Fault Zone might be the dominant magmatic conduit for mantle-derived magmas ascending to the upper crust. In addition, intersecting faults with different orientations could control the distribution and geometry of the vents, calderas, dykes and plutons and play an important role in forming magma conduits for individual volcanoes. Keywords: Basaltic underplating; Magmatic plumbing; Southeast China; Calderas; Active-source seismic tomography

  3. Multidimensional analysis and probabilistic model of volcanic and seismic activities

    NASA Astrophysics Data System (ADS)

    Fedorov, V.

    2009-04-01

    A search for space and time regularities in volcanic and seismic events for the purpose of forecast method development seems to be of current concern, both scientifically and practically. The seismic and volcanic processes take place in the Earth's field of gravity which in turn is closely related to gravitational fields of the Moon, the Sun, and the planets of the Solar System. It is mostly gravity and tidal forces that exercise control over the Earth's configuration and relief. Dynamic gravitational interaction between the Earth and other celestial bodies makes itself evident in tidal phenomena and other effects in the geospheres (including the Earth's crust). Dynamics of the tidal and attractive forces is responsible for periodical changes in gravity force, both in value and direction [Darwin, 1965], in the rate of rotation and orbital speed; that implies related changes in the endogenic activity of the Earth. The Earth's rotation in the alternating gravitational field accounts to a considerable extent for regular pattern of crustal deformations and dislocations; it is among principal factors that control the Earth's form and structure, distribution of oceans and continents and, probably, continental drift [Peive, 1969; Khain, 1973; Kosygin, 1983]. The energy of gravitational interaction is transmitted through the tidal energy to planetary spheres and feeds various processes there, including volcanic and seismic ones. To determine degree, character and special features of tidal force contribution to the volcanic and seismic processes is of primary importance for understanding of genetic and dynamic aspects of volcanism and seismicity. Both volcanic and seismic processes are involved in evolution of celestial bodies; they are operative on the planets of the Earth group and many satellites [Essays…, 1981; Lukashov, 1996]. From this standpoint, studies of those processes are essential with a view to development of scenarios of the Earth's evolution as a celestial

  4. Multidimensional analysis and probabilistic model of volcanic and seismic activities

    NASA Astrophysics Data System (ADS)

    Fedorov, V.

    2009-04-01

    A search for space and time regularities in volcanic and seismic events for the purpose of forecast method development seems to be of current concern, both scientifically and practically. The seismic and volcanic processes take place in the Earth's field of gravity which in turn is closely related to gravitational fields of the Moon, the Sun, and the planets of the Solar System. It is mostly gravity and tidal forces that exercise control over the Earth's configuration and relief. Dynamic gravitational interaction between the Earth and other celestial bodies makes itself evident in tidal phenomena and other effects in the geospheres (including the Earth's crust). Dynamics of the tidal and attractive forces is responsible for periodical changes in gravity force, both in value and direction [Darwin, 1965], in the rate of rotation and orbital speed; that implies related changes in the endogenic activity of the Earth. The Earth's rotation in the alternating gravitational field accounts to a considerable extent for regular pattern of crustal deformations and dislocations; it is among principal factors that control the Earth's form and structure, distribution of oceans and continents and, probably, continental drift [Peive, 1969; Khain, 1973; Kosygin, 1983]. The energy of gravitational interaction is transmitted through the tidal energy to planetary spheres and feeds various processes there, including volcanic and seismic ones. To determine degree, character and special features of tidal force contribution to the volcanic and seismic processes is of primary importance for understanding of genetic and dynamic aspects of volcanism and seismicity. Both volcanic and seismic processes are involved in evolution of celestial bodies; they are operative on the planets of the Earth group and many satellites [Essays…, 1981; Lukashov, 1996]. From this standpoint, studies of those processes are essential with a view to development of scenarios of the Earth's evolution as a celestial

  5. Seismic Activity in the Gulf of Mexico: a Preliminary Analysis

    NASA Astrophysics Data System (ADS)

    Franco, S. I.; Canet, C.; Iglesias, A.; Valdes-Gonzales, C. M.

    2013-05-01

    The southwestern corner of Gulf of Mexico (around the northern Isthmus of Tehuantepec) is exposed to an intense deep (> 100 km) seismic activity caused by the subduction of the Cocos plate. Aside from this, the gulf has been considered as a zone of low or no-seismicity. However, a sparse shallow seismic activity is observed across the Gulf of Mexico; some of these earthquakes have been strongly felt (e.g. 23/05/2007 and 10/09/2006), and the Jaltipan, 1959 earthquake caused fatalities and severe destruction in central and southern Veracruz. In this work we analyze 5 relevant earthquakes that occurred since 2001. At the central Gulf of Mexico focal mechanisms show inverse faults oriented approximately NW-SE with dip near 45 degrees, suggesting a link to sediment loading and/or to salt tectonics. On the other hand, in the southwestern corner of the gulf we analyzed some clear examples of strike-slip faults and activity probably related to the Veracruz Fault. One anomalous earthquake, recorded in 2007 in the western margin of the gulf, shows a strike-slip mechanism indicating a transform regime probably related with the East Mexican Fault. The recent improvement of the Mexican Seismological broadband network have allowed to record small earthquakes distributed in and around the Gulf of Mexico. Although the intermediate and large earthquakes in the region are infrequent, the historic evidence indicates that the magnitudes could reach Mw~6.4. This fact could be taken in consideration to reassess the seismic hazard for oil and industrial infrastructure in the region.

  6. Improving the Detectability of the Catalan Seismic Network for Local Seismic Activity Monitoring

    NASA Astrophysics Data System (ADS)

    Jara, Jose Antonio; Frontera, Tànit; Batlló, Josep; Goula, Xavier

    2016-04-01

    The seismic survey of the territory of Catalonia is mainly performed by the regional seismic network operated by the Cartographic and Geologic Institute of Catalonia (ICGC). After successive deployments and upgrades, the current network consists of 16 permanent stations equipped with 3 component broadband seismometers (STS2, STS2.5, CMG3ESP and CMG3T), 24 bits digitizers (Nanometrics Trident) and VSAT telemetry. Data are continuously sent in real-time via Hispasat 1D satellite to the ICGC datacenter in Barcelona. Additionally, data from other 10 stations of neighboring areas (Spain, France and Andorra) are continuously received since 2011 via Internet or VSAT, contributing both to detect and to locate events affecting the region. More than 300 local events with Ml ≥ 0.7 have been yearly detected and located in the region. Nevertheless, small magnitude earthquakes, especially those located in the south and south-west of Catalonia may still go undetected by the automatic detection system (DAS), based on Earthworm (USGS). Thus, in order to improve the detection and characterization of these missed events, one or two new stations should be installed. Before making the decision about where to install these new stations, the performance of each existing station is evaluated taking into account the fraction of detected events using the station records, compared to the total number of events in the catalogue, occurred during the station operation time from January 1, 2011 to December 31, 2014. These evaluations allow us to build an Event Detection Probability Map (EDPM), a required tool to simulate EDPMs resulting from different network topology scenarios depending on where these new stations are sited, and becoming essential for the decision-making process to increase and optimize the event detection probability of the seismic network.

  7. Paleoseismic targets, seismic hazard, and urban areas in the Central and Eastern United States

    USGS Publications Warehouse

    Wheeler, R.L.

    2008-01-01

    Published geologic information from the central and eastern United States identifies 83 faults, groups of sand blows, named seismic zones, and other geological features as known or suspected products of Quaternary tectonic faulting. About one fifth of the features are known to contain faulted Quaternary materials or seismically induced liquefaction phenomena, but the origin and associated seismic hazard of most of the other features remain uncertain. Most of the features are in or near large urban areas. The largest cluster of features is in the Boston-Washington urban corridor (2005 estimated population: 50 million). The proximity of most features to populous areas identifies paleoseismic targets with potential to impact urban-hazard estimates.

  8. Study of Seismic Activity Using Geophysical and Radio Physical Equipment for Observation

    NASA Astrophysics Data System (ADS)

    Kvavadze, N.; Tsereteli, N. S.

    2015-12-01

    One of the most dangerous and destructive natural hazards are earthquakes, which is confirmed by recent earthquakes such as Nepal 2015, Japan and Turkey 2011. Because of this, study of seismic activity is important. Studying any process, it is necessary to use different methods of observation, which allows us to increase accuracy of obtained data. Seismic activity is a complex problem and its study needs different types of observation methods. Two main problems of seismic activity study are: reliable instrumental observations and earthquake short-term predictions. In case of seismic risks it is necessary to have reliable accelerometer data. One of the most promising field in earthquake short-term prediction is very low frequency (VLF) electromagnetic wave propagation in ionosphere observation. To study Seismic activity of Caucasus region, was created observation complex using Accelerometer, Velocimeter and VLF electromagnetic waves received from communication stations (located in different area of the world) reflected from low ionosphere. System is created and operates at Tbilisi State University Ionosphere Observatory, near Tbilisi in Tabakhmela 42.41'70 N, 44.80'92 E, Georgia. Data obtained is sent to a local server located at M. Nodia Institute of Geophysics, TSU, for storage and processing. Diagram for complex is presented. Also data analysis methods were created and preliminary processing was done. In this paper we present some of the results: Earthquake data from ionosphere observations as well as local earthquakes recorded with accelerometer and velocimeter. Complex is first in 6 that will be placed around Georgia this year. We plan on widening network every year.

  9. PRESS40: a project for involving students in active seismic risk mitigation

    NASA Astrophysics Data System (ADS)

    Barnaba, Carla; Contessi, Elisa; Rosa Girardi, Maria

    2016-04-01

    To memorialize the anniversary of the 1976 Friuli earthquake, the Istituto Statale di Istruzione Superiore "Magrini Marchetti" in Gemona del Friuli (NE Italy), with the collaboration of the Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS), has promoted the PRESS40 Project (Prevenzione Sismica nella Scuola a 40 anni dal terremoto del Friuli, that in English sounds like "Seismic Prevention at School 40 years later the Friuli earthquake"). The project has developed in the 2015-2016 school year, starting from the 40th anniversary of the Friuli earthquake, and it aims to disseminate historical memory, seismic culture and awareness of seismic safety in the young generations, too often unconscious of past experiences, as recent seismic hazard perception tests have demonstrated. The basic idea of the PRESS40 Project is to involve the students in experimental activities to be active part of the seismic mitigation process. The Project is divided into two main parts, the first one in which students learn-receive knowledge from researchers, and the second one in which they teach-bring knowledge to younger students. In the first part of the project, 75 students of the "Magrini Marchetti" school acquired new geophysical data, covering the 23 municipalities from which they come from. These municipalities represent a wide area affected by the 1976 Friuli earthquake. In each locality a significant site was examined, represented by a school area. At least, 127 measurements of ambient noise have been acquired. Data processing and interpretation of all the results are still going on, under the supervision of OGS researchers.The second part of the project is planned for the early spring, when the students will present the results of geophysical survey to the younger ones of the monitored schools and to the citizens in occasion of events to commemorate the 40th anniversary of the Friuli earthquake.

  10. Seismic exploration of Fuji volcano with active sources in 2003

    NASA Astrophysics Data System (ADS)

    Oikawa, J.; Kagiyama, T.; Tanaka, S.; Miyamachi, H.; Tsutsui, T.; Ikeda, Y.; Katayama, H.; Matsuo, N.; Oshima, H.; Nishimura, Y.; Yamamoto, K.; Watanabe, T.; Yamazaki, F.

    2004-12-01

    Fuji volcano (altitude 3,776 m) is the largest basaltic stratovolcano in Japan. In late August and early September 2003, seismic exploration was conducted around Fuji volcano by the detonation of 500 kg charges of dynamite to investigate the seismic structure of that area. Seismographs with an eigenfrequency of 2 Hz were used for observation, positioned along a WSW-ENE line passing through the summit of the mountain. A total of 469 observation points were installed at intervals of 250-500 m. The data were stored in memory on-site using data loggers. The sampling interval was 4 ms. Charges were detonated at 5 points, one at each end of the observation line and 3 along its length. The first arrival times at each observation point for each detonation were recorded as data. The P-wave velocity structure directly below the observation line was determined by forward calculation using the ray tracing method [Zelt and Smith, 1992]. The P-wave velocity structure below the volcano, assuming a layered structure, was found to be as follows. (1) The first layer extends for about 40 km around the summit and to a depth of 1-2 km. The P-wave velocity is 2.5 km/s on the upper surface of the layer and 3.5 km/s on the lower interface. (2) The second layer has P-wave velocities of 4.0 km/s on the top interface and 5.5 km/s at the lower interface. The layer is 25 km thick to the west of the summit and 1-2 km thick to the east, and forms a dome shape with a peak altitude of 2000 m directly below the summit. (3) The third layer is 5-12 km thick and has P-wave velocities of 5.7 km/s at the top interface and 6.5 km/s at the lower interface. This layer reaches shallower levels to the east of the summit, corresponding to the area where the second layer is thinner. Mt. Fuji is located slightly back from where the Philippine Sea Plate subducts below the Eurasian plate in association with collision with the Izu Peninsula. Matsuda (1971) suggested that Mt. Fuji lies on the same uplifted body as

  11. Spatial heterogeneities of deviatoric stress and pore-pressure in Kyushu, Japan, and their implication for seismic activity

    NASA Astrophysics Data System (ADS)

    Matsumoto, Satoshi; Chikura, Hiromi; Ohkura, Takahiro; Miyazaki, Masahiro; Shimizu, Hiroshi; Abe, Yuki; Inoue, Hiroyuki; Yoshikawa, Shin; Yamashita, Yusuke

    2013-04-01

    We investigated the spatial variation in stress fields and pore fluid pressures on Kyushu Island, southwestern Japan. High seismic activity is found not only along active faults in Kyushu Island (southwestern Japan) but also in the central area of the island where there are active volcanoes. We consider the focal mechanisms of the shallow earthquakes on Kyushu Island to determine the relative deviatoric stress field and pore fluid factor. Generally, the stress field corresponds to a strike slip regime in this area. A decline in the maximum principal compressional stress is found in the western part of the high seismicity area, in the middle of Kyushu Island; this may be caused by a thickening of the seismogenic zone, as estimated from D90 analysis. At thin seismogenic layer, strike slip faulting dominates and strain rate from GPS study is high. In the active fault zone, seismic activity along the fault is high, and the pore pressure within the zone is higher than the values observed elsewhere, suggesting a mechanism explained by the fault valve model of Sibson [1992]. The pore pressure in the high seismic area with scattered hypocenter distribution in the middle part is lower than that in the active fault zones.

  12. Variation of the Earth tide-seismicity compliance parameter during the recent seismic activity in Fthiotida, central Greece

    NASA Astrophysics Data System (ADS)

    Arabelos, Dimitrios N.; Contadakis, Michael E.; Vergos, Georgios; Spatalas, Spyrous

    2016-01-01

    Based on the results of our previous studies concerning the tidal triggering effect on the seismicity in Greece, we consider the confidence level of earthquake occurrence - tidal period accordance as an index of tectonic stress criticality, associated with earthquake occurrence. Then, we investigate whether the recent increase in the seismic activity at Fthiotida in Greek mainland indicates faulting maturity and the possible production a stronger earthquake. In this paper we present the results of this investigation

  13. Review of Natural Phenomena Hazard (NPH) Assessments for the Hanford 200 Areas (Non-Seismic)

    SciTech Connect

    Snow, Robert L.; Ross, Steven B.; Sullivan, Robin S.

    2010-09-24

    The purpose of this review is to assess the need for updating Natural Phenomena Hazard (NPH) assessments for the Hanford 200 Areas, as required by DOE Order 420.1B Chapter IV, Natural Phenomena Hazards Mitigation, based on significant changes in state-of-the-art NPH assessment methodology or site-specific information. The review includes all natural phenomena hazards with the exception of seismic/earthquake hazards, which are being addressed under a separate effort. It was determined that existing non-seismic NPH assessments are consistent with current design methodology and site specific data.

  14. Refining seismic parameters in low seismicity areas by 3D trenching: The Alhama de Murcia fault, SE Iberia

    NASA Astrophysics Data System (ADS)

    Ferrater, Marta; Ortuño, Maria; Masana, Eulàlia; Pallàs, Raimon; Perea, Hector; Baize, Stephane; García-Meléndez, Eduardo; Martínez-Díaz, José J.; Echeverria, Anna; Rockwell, Thomas K.; Sharp, Warren D.; Medialdea, Alicia; Rhodes, Edward J.

    2016-06-01

    Three-dimensional paleoseismology in strike-slip faults with slip rates less than 1 mm per year involves a great methodological challenge. We adapted 3D trenching to track buried channels offset by the Alhama de Murcia seismogenic left-lateral strike-slip fault (SE Iberia). A fault net slip of 0.9 ± 0.1 mm/yr was determined using statistical analysis of piercing lines for one buried channel, whose age is constrained between 15.2 ± 1.1 ka and 21.9-22.3 cal BP. This value is larger and more accurate than the previously published slip rates for this fault. The minimum number of five paleo-earthquakes identified since the deposition of dated layers suggests a maximum average recurrence interval of approximately 5 ka. The combination of both seismic parameters yields a maximum slip per event between 5.3 and 6.3 m. We show that accurately planned trenching strategies and data processing may be key to obtaining robust paleoseismic parameters in low seismicity areas.

  15. Seismicity studies at Moluccas area based on the result of hypocenter relocation using HypoDD

    NASA Astrophysics Data System (ADS)

    Utama, Muhammad Reza July; Nugraha, Andri Dian; Puspito, Nanang T.

    2015-04-01

    The precise hypocenter was determined location using double difference method around subduction zone in Moluccas area eastern part of Indonesia. The initial hypocenter location from MCGA data catalogue of 1,945 earthquake events. Basically the principle of double-difference algorithm assumes if the distance between two earthquake hypocenter distribution is very small compared to the distance between the station to the earthquake source, the ray path can be considered close to both earthquakes. The results show the initial earthquakes with a certain depth (fix depth 10 km) relocated and can be interpreted more reliable in term of seismicity and geological setting. The relocation of the intra slab earthquakes beneath Banda Arc are also clearly observed down to depth of about 400 km. The precise relocated hypocenter will give invaluable seismicity information for other seismological and tectonic studies especially for seismic hazard analysis in this region.

  16. Seismicity studies at Moluccas area based on the result of hypocenter relocation using HypoDD

    SciTech Connect

    Utama, Muhammad Reza July; Nugraha, Andri Dian; Puspito, Nanang T.

    2015-04-24

    The precise hypocenter was determined location using double difference method around subduction zone in Moluccas area eastern part of Indonesia. The initial hypocenter location from MCGA data catalogue of 1,945 earthquake events. Basically the principle of double-difference algorithm assumes if the distance between two earthquake hypocenter distribution is very small compared to the distance between the station to the earthquake source, the ray path can be considered close to both earthquakes. The results show the initial earthquakes with a certain depth (fix depth 10 km) relocated and can be interpreted more reliable in term of seismicity and geological setting. The relocation of the intra slab earthquakes beneath Banda Arc are also clearly observed down to depth of about 400 km. The precise relocated hypocenter will give invaluable seismicity information for other seismological and tectonic studies especially for seismic hazard analysis in this region.

  17. Seismic Hazard and Risk Assessments for Beijing-Tianjin-Tangshan, China, Area

    USGS Publications Warehouse

    Xie, F.; Wang, Z.; Liu, J.

    2011-01-01

    Seismic hazard and risk in the Beijing-Tianjin-Tangshan, China, area were estimated from 500-year intensity observations. First, we digitized the intensity observations (maps) using ArcGIS with a cell size of 0.1 ?? 0.1??. Second, we performed a statistical analysis on the digitized intensity data, determined an average b value (0.39), and derived the intensity-frequency relationship (hazard curve) for each cell. Finally, based on a Poisson model for earthquake occurrence, we calculated seismic risk in terms of a probability of I ??? 7, 8, or 9 in 50 years. We also calculated the corresponding 10 percent probability of exceedance of these intensities in 50 years. The advantages of assessing seismic hazard and risk from intensity records are that (1) fewer assumptions (i. e., earthquake source and ground motion attenuation) are made, and (2) site-effect is included. Our study shows that the area has high seismic hazard and risk. Our study also suggests that current design peak ground acceleration or intensity for the area may not be adequate. ?? 2010 Birkh??user / Springer Basel AG.

  18. A Large-N Mixed Sensor Active + Passive Seismic Array near Sweetwater, TX

    NASA Astrophysics Data System (ADS)

    Barklage, M.; Hollis, D.; Gridley, J. M.; Woodward, R.; Spriggs, N.

    2014-12-01

    A collaborative high-density seismic survey using broadband and short period seismic sensors was conducted March 7 - April 30, 2014 near Sweetwater, TX. The objective of the survey was to use a combination of controlled source shot slices and passive seismic recordings recorded by multiple types of sensors with different bandwidths and sensitivities to image the subsurface. The broadband component of the survey consisted of 25 continuously recording seismic stations comprised of 20 Trillium Compact Posthole sensors from Nanometrics and 5 Polar Trillium 120PHQs from the IRIS/PASSCAL Instrument Center (PIC). The broadband stations also utilized 25 Centaur digitizers from Nanometrics as well as 25 polar quick deploy enclosures from the PIC. The broadband array was designed to maximize horizontal traveling seismic energy for surface wave analysis over the primary target area with sufficient offset for imaging objectives at depth. The short period component of the survey consisted of 2639 receiver locations using Zland nodes from NodalSeismic. The nodes are further divided into 3 sub-arrays: 1) outlier array 2) active source array 3) backbone array. The outlier array consisted of 25 continuously recording nodes distributed around the edge of the survey at a distance of ~5 km from the survey boundary, and provided valuable constraints to passive data analysis techniques at the edge of the survey boundary. The active source patch consisted of densely spaced nodes that were designed to record signals from a Vibroseis source truck for active source reflection processing and imaging. The backbone array consisted of 292 nodes that covered the entirety of the survey area to maximize the value of the passive data analysis. By utilizing continuous recording and smartly designed arrays for measuring local and regional earthquakes we can incorporate velocity information derived from passive data analysis into the active source processing workflow to produce a superior subsurface

  19. Identification of seismically susceptible areas in western Himalaya using pattern recognition

    NASA Astrophysics Data System (ADS)

    Mridula; Sinvhal, Amita; Wason, Hans Raj

    2016-06-01

    Seismicity in the western Himalayas is highly variable. Several historical and instrumentally recorded devastating earthquakes originated in the western Himalayas which are part of the Alpine-Himalayan belt. Earthquakes cause tremendous loss of life and to the built environment. The amount of loss in terms of life and infrastructure has been rising continuously due to significant increase in population and infrastructure. This study is an attempt to identify seismically susceptible areas in western Himalaya, using pattern recognition technique. An area between latitude 29∘-36∘N and longitude 73∘-80∘E was considered for this study. Pattern recognition starts with identification, selection and extraction of features from seismotectonic data. These features are then subjected to discriminant analysis and the study area was classified into three categories, viz., Area A: most susceptible area, Area B: moderately susceptible area, and Area C: least susceptible area. Results show that almost the entire states of Himachal Pradesh and Uttarakhand and a portion of Jammu & Kashmir are classified as Area A, while most of Jammu & Kashmir is classified as Area B and the Indo-Gangetic plains are classified as Area C.

  20. Radar imaging of winter seismic survey activity in the National Petroleum Reserve-Alaska

    USGS Publications Warehouse

    Jones, Benjamin M.; Rykhus, Russ; Lu, Zhiming; Arp, C.D.; Selkowitz, D.J.

    2008-01-01

    During the spring of 2006, Radarsat-1 synthetic aperture radar (SAR) imagery was acquired on a continual basis for the Teshekpuk Lake Special Area (TLSA), in the northeast portion of the National Petroleum Reserve, Alaska (NPR-A) in order to monitor lake ice melting processes. During data processing, it was discovered that the Radarsat-1 imagery detected features associated with winter seismic survey activity. Focused analysis of the image time series revealed various aspects of the exploration process such as the grid profile associated with the seismic line surveys as well as trails and campsites associated with the mobile survey crews. Due to the high temporal resolution of the dataset it was possible to track the progress of activities over a one month period. Spaceborne SAR imagery can provide information on the location of winter seismic activity and could be used as a monitoring tool for land and resource managers as increased petroleum-based activity occurs in the TLSA and NPR-A. ?? 2008 Cambridge University Press.

  1. The Effect of Recent Volcanic Activity on the Seismic Structure of Madagascar

    NASA Astrophysics Data System (ADS)

    Wysession, M. E.; Aleqabi, G. I.; Pratt, M. J.; Shore, P.; Wiens, D. A.; Nyblade, A.; Rambolamanana, G.; Andriampenomanana Ny Ony, F. S. T.; Tsiriandrimanana, R.

    2014-12-01

    The seismic structure of Madagascar is determined using ambient-noise and two-plane-wave earthquake surface waves analyses. A deep low-velocity anomaly is seen in regions of recent volcanic activity in the central and northern regions of the island. The primary data used are from the 2011-2013 MACOMO (Madagascar, the Comoros, and Mozambique) broadband seismic array from the PASSCAL program of IRIS (Incorporated Research Institutions for Seismology), funded by the NSF. Additional data came from the RHUM-RUM project (led by G. Barruol and K. Sigloch), the Madagascar Seismic Profile (led by F. Tilmann), and the GSN. For the ambient-noise study, Rayleigh wave green's functions for all interstation paths are extracted from the broadband seismic data recorded from August 2011 until October 2013. Rayleigh wave group and phase velocity dispersion curves are extracted in the 8 - 50 s period range, identifying shallow crustal structure. For deeper structure, the two-plane-wave method is used on teleseismic earthquake data to obtain surface wave phase velocities in the 20 - 182 s period range. In the inversion, a finite-frequency kernel is used for each period, and a 1-D shear velocity structure is determined at each location. A three-dimensional S-wave velocity model of the crust and upper mantle is obtained from assembling the 1-D models. Preliminary results show a good correlation between the Rayleigh wave velocities and the geology of Madagascar, which includes areas of ancient Archaean craton. The slowest seismic velocities are associated with known volcanic regions in both the central and northern regions, which have experienced volcanic activity within the past million years.

  2. Mapping of active faults based on the analysis of high-resolution seismic reflection profiles in offshore Montenegro

    NASA Astrophysics Data System (ADS)

    Vucic, Ljiljana; Glavatovic, Branislav

    2014-05-01

    High-resolution seismic-reflection data analysis is considered as important tool for mapping of active tectonic faults, since seismic exploration methods on varied scales can image subsurface structures of different depth ranges. Mapping of active faults for the offshore area of Montenegro is performed in Petrel software, using reflection database consist of 2D profiles in length of about 3.500 kilometers and 311 square kilometers of 3D seismics, acquired from 1979 to 2003. Montenegro offshore area is influenced by recent tectonic activity with numerous faults, folded faults and over trusts. Based on reflection profiles analysis, the trust fault system offshore Montenegro is reveled, parallel to the coast and extending up to 15 kilometers from the offshore line. Then, the system of normal top carbonate fault planes is mapped and characterized on the southern Adriatic, with NE trending. The tectonic interpretation of the seismic reflection profiles in Montenegro point toward the existence of principally reverse tectonic forms in the carbonate sediments, covered by young Quaternary sandy sediments of thickness 1-3 kilometers. Also, reflective seismic data indicate the active uplifting of evaporite dome on about 10 kilometers of coastline.

  3. Deep Seismic Researches Of Seismic-Active Zones With Use Of High-Power Vibrators - Technique, Outcomes, Outlooks

    NASA Astrophysics Data System (ADS)

    Soloviev, V.; Seleznev, V.; Emanov, A.; Sal`Nikov, A.; Kashun, V.; Glinsky, B.; Kovalevsky, V.; Zhemchugova, I.; Danilov, I.; Liseikin, A.

    2004-12-01

    There are presented the materials of deep vibroseism researches, carried out in seismic active regions of Siberia with use of stationary (100-tos power) and moveable vibration sources (40-60tons power) and mobile digital recording equipment. There are given some examples of unique, have no world analogues, correlograms from high-power vibrators on distances to 400km and more. Using new vibroseismic technology of deep seismic researches, there were got detail deep sections of the Earth's crust and upper mantle, including time-sections of CDP-DSS up to depth of 80km. Materials of vibroseismic investigations on 2500km of seismic profiles in hard-to-reach regions of the Altay-Sayan region, the Baikal rift zone and Okhotsko-Chukotski regions are evidence of high cost efficiency, ecological safety, possibility to be realized in hard-to-reach region and finally of availability of deep seismic investigations with use of high-power vibration sources.

  4. Characterization and Relocation of Seismic Clusters in the Area of Bahia de Banderas, Jalisco-Nayarit, Mexico

    NASA Astrophysics Data System (ADS)

    Rutz Lopez, M.; Nunez-Cornu, F. J.; Carmona, E.

    2004-12-01

    We analysed the seismic activity that took place the year of 2003 in the area of Bahia de Banderas, between the states of Jalisco and Nayarit, registrated with a local network of 7 stations, which belongs to the Civil Defence of Jalisco and the University of Guadalajara. 400 events have been located, in these earthquakes we identified some series of a similar waveforms. For defining this similarity between seismic events and in order to classify them into clusters, we have applied the cross-correlation method of the P and S arrivals. We found a fourth part of epicentres gathered into 15 clusters of 3-25 events. For some clusters we used relocations relative to a master event. Located south of Bahia de Banderas exist clusters aligned along structures trending N-S in the area of Tuito. This trend agrees with the topographic relief of the area. Other clustes can be related with active tectonic structures at north of Cajon de Peñas dam (Tomatlan). Another cluster was identified at the East, Amatlan de Cañas-Ameca area, and one more in the center of the Bahia de Banderas.

  5. Seismic reflection imaging in the ruptured area of The Tohoku-Oki Earthquake - Results from rapid response seismic reflection surveys -

    NASA Astrophysics Data System (ADS)

    Nakamura, Y.; No, T.; Fujie, G.; Kaiho, Y.; Sato, T.; Barnes, J.; Boston, B.; Yamashita, M.; Park, J.; Miura, S.; Takahashi, N.; Kodaira, S.; Kaneda, Y.; Moore, G. F.

    2011-12-01

    The 2011 off the Pacific coast of Tohoku Earthquake is one of the largest earthquakes ever observed and generated devastating Tsunamis. Seismological analysis revealed that the large slip occurred beneath the lower trench slope area, close to the Japan trench axis, (e.g. Ide et al. 2011), which seems to be related with the Tsunami generation. We conducted rapid response reflection seismic surveys using R/V Kairei after the main shock to delineate the structure of the ruptured area off Miyagi. Ten E-W lines with at least 120 km of length were surveyed using a 6 km-long, 444 channel streamer cable and a 7800 inch^3 tuned air gun array. The line spacing was 10-20 km. Preliminary processed data and their interpretation demonstrate that the structure considerably varies from south to north in the survey area. Normal faults dominate in the deep sea terrace. Those faults cut sedimentary sequence in this area, and sometimes offset the reflector at the top of cretaceous sequence. Beneath the trench slope, there are few reflectors especially in the shallower depth below the seafloor. Low angle landward dipping reflectors are observed in most of the survey area, some of them coincides with the backstop interface pointed out by Tsuru et al. (2000), but apparent shape and location of these reflectors are not consistent through the survey area. These reflectors may represent faults, but it is difficult to determine the sense of faulting. In the northern part of the survey area, prominent seaward dipping normal faults are observed in the upper to middle slope. Similar normal faults in small scale can be also recognized in some other lines, and should be one of key features offshore Tohoku region.

  6. Subducting seamounts control interplate coupling and seismic rupture in the 2014 Iquique earthquake area

    NASA Astrophysics Data System (ADS)

    Geersen, Jacob; Ranero, César R.; Barckhausen, Udo; Reichert, Christian

    2015-09-01

    To date, the parameters that determine the rupture area of great subduction zone earthquakes remain contentious. On 1 April 2014, the Mw 8.1 Iquique earthquake ruptured a portion of the well-recognized northern Chile seismic gap but left large highly coupled areas un-ruptured. Marine seismic reflection and swath bathymetric data indicate that structural variations in the subducting Nazca Plate control regional-scale plate-coupling variations, and the limited extent of the 2014 earthquake. Several under-thrusting seamounts correlate to the southward and up-dip arrest of seismic rupture during the 2014 Iquique earthquake, thus supporting a causal link. By fracturing of the overriding plate, the subducting seamounts are likely further responsible for reduced plate-coupling in the shallow subduction zone and in a lowly coupled region around 20.5°S. Our data support that structural variations in the lower plate influence coupling and seismic rupture offshore Northern Chile, whereas the structure of the upper plate plays a minor role.

  7. Subducting seamounts control interplate coupling and seismic rupture in the 2014 Iquique earthquake area

    PubMed Central

    Geersen, Jacob; Ranero, César R.; Barckhausen, Udo; Reichert, Christian

    2015-01-01

    To date, the parameters that determine the rupture area of great subduction zone earthquakes remain contentious. On 1 April 2014, the Mw 8.1 Iquique earthquake ruptured a portion of the well-recognized northern Chile seismic gap but left large highly coupled areas un-ruptured. Marine seismic reflection and swath bathymetric data indicate that structural variations in the subducting Nazca Plate control regional-scale plate-coupling variations, and the limited extent of the 2014 earthquake. Several under-thrusting seamounts correlate to the southward and up-dip arrest of seismic rupture during the 2014 Iquique earthquake, thus supporting a causal link. By fracturing of the overriding plate, the subducting seamounts are likely further responsible for reduced plate-coupling in the shallow subduction zone and in a lowly coupled region around 20.5°S. Our data support that structural variations in the lower plate influence coupling and seismic rupture offshore Northern Chile, whereas the structure of the upper plate plays a minor role. PMID:26419949

  8. Subducting seamounts control interplate coupling and seismic rupture in the 2014 Iquique earthquake area.

    PubMed

    Geersen, Jacob; Ranero, César R; Barckhausen, Udo; Reichert, Christian

    2015-01-01

    To date, the parameters that determine the rupture area of great subduction zone earthquakes remain contentious. On 1 April 2014, the Mw 8.1 Iquique earthquake ruptured a portion of the well-recognized northern Chile seismic gap but left large highly coupled areas un-ruptured. Marine seismic reflection and swath bathymetric data indicate that structural variations in the subducting Nazca Plate control regional-scale plate-coupling variations, and the limited extent of the 2014 earthquake. Several under-thrusting seamounts correlate to the southward and up-dip arrest of seismic rupture during the 2014 Iquique earthquake, thus supporting a causal link. By fracturing of the overriding plate, the subducting seamounts are likely further responsible for reduced plate-coupling in the shallow subduction zone and in a lowly coupled region around 20.5°S. Our data support that structural variations in the lower plate influence coupling and seismic rupture offshore Northern Chile, whereas the structure of the upper plate plays a minor role. PMID:26419949

  9. Active damping performance of the KAGRA seismic attenuation system prototype

    NASA Astrophysics Data System (ADS)

    Fujii, Yoshinori; Sekiguchi, Takanori; Takahashi, Ryutaro; Aso, Yoichi; Barton, Mark; Erasmo Peña Arellano, Fabián; Shoda, Ayaka; Akutsu, Tomotada; Miyakawa, Osamu; Kamiizumi, Masahiro; Ishizaki, Hideharu; Tatsumi, Daisuke; Hirata, Naoatsu; Hayama, Kazuhiro; Okutomi, Koki; Miyamoto, Takahiro; Ishizuka, Hideki; DeSalvo, Riccardo; Flaminio, Raffaele

    2016-05-01

    The Large-scale Cryogenic Gravitational wave Telescope (formerly LCGT now KAGRA) is presently under construction in Japan. This May we assembled a prototype of the seismic attenuation system (SAS) for the beam splitter and the signal recycling mirrors of KAGRA, which we call Type-B SAS, and evaluated its performance at NAOJ (Mitaka, Toyko). We investigated its frequency response, active damping performance, vibration isolation performance and long-term stability both in and out of vacuum. From the frequency response test and the active damping performance test, we confirmed that the SAS worked as we designed and that all mechanical resonances which could disturb lock acquisition and observation are damped within 1 minute, which is required for KAGRA, by the active controls.

  10. Application of neural networks to seismic active control

    SciTech Connect

    Tang, Yu

    1995-07-01

    An exploratory study on seismic active control using an artificial neural network (ANN) is presented in which a singledegree-of-freedom (SDF) structural system is controlled by a trained neural network. A feed-forward neural network and the backpropagation training method are used in the study. In backpropagation training, the learning rate is determined by ensuring the decrease of the error function at each training cycle. The training patterns for the neural net are generated randomly. Then, the trained ANN is used to compute the control force according to the control algorithm. The control strategy proposed herein is to apply the control force at every time step to destroy the build-up of the system response. The ground motions considered in the simulations are the N21E and N69W components of the Lake Hughes No. 12 record that occurred in the San Fernando Valley in California on February 9, 1971. Significant reduction of the structural response by one order of magnitude is observed. Also, it is shown that the proposed control strategy has the ability to reduce the peak that occurs during the first few cycles of the time history. These promising results assert the potential of applying ANNs to active structural control under seismic loads.

  11. Microseismicity in the Seoul Metropolitan Area, Korea, and its implications for the seismic hazards

    NASA Astrophysics Data System (ADS)

    Kim, K.; Kim, W.; Kang, S.; Ryoo, Y.; Kim, M.; Park, Y.; Kyung, J.

    2012-12-01

    On 9 February 2010, a minor earthquake occurred in the northwest of South Korea. The earthquake was widely felt in the Seoul National Capital Area (SNCA). The earthquake attracted much attention from media, politicians, policy makers and the public, who raised concerns about seismic hazards and risks in the Korea Peninsula, in particular, to the SNCA. SNCA includes the Seoul and Incheon metropolitans and most of the Gyeonggi province. It has a population of 24.5 million (as of 2007) and is ranked as the second largest metropolitan area in the world. The SNCA has been the center of the economics, politics, and culture during the past half millennium since the city has been designated as the capital city in 1394. We applied waveform correlation detector to 2007-2010 continuously recorded seismic data to identify repeating earthquakes. We identify 9 micro-earthquakes during 2007-2010 periods which are not reported in the KNSN bulletin because their magnitudes are too small. Estimated magnitudes using amplitude ratios measured at the station SEO indicate the smallest event detected by the waveform cross correlation technique in the study is as low as 0.19. The number of events for our interpretation becomes 11 including two previously reported events and nine newly identified micro-earthquakes. All of them occur in a very small area. While there are historic documents reporting earthquakes in the SNCA, repeating earthquakes or clustered seismicity from the instrumental earthquake record have not reported before. We have determined the focal mechanism solution for the representative events (9 February 2010, ML 3.0) using the first-motion polarities. The preferred focal mechanism solution for the representative event is the WNW-ESE striking fault, which are consistent with the precisely determined earthquake hypocenter distribution. It is also consistent with the results in the previous studies of stress orientation in and around the Korean peninsula. The new list of

  12. Near-Surface Seismic Refraction Methods to Characterize Areas of Karst Geology near Carlsbad, NM

    NASA Astrophysics Data System (ADS)

    Cafferky, S.; Bonal, N. D.; Barnhart, K.

    2012-12-01

    Near-surface seismic refraction methods applied to karst geology can give some ideas as to the nature of the void spaces as well as the stratigraphy of the area. A seismic geophone array was laid out near Carlsbad, NM, an area known to contain karst features. Using an impact (sledge hammer), seismic data was collected along two intersecting lines of geophones as well as two gridded areas to get three-dimensional information. The data was picked for the first arrivals of the P-wave, which were graphed and examined for changes in slope and inconsistencies in shape. The data analyzed shows a two-layer model and some inconsistencies such as polarity reversals and delayed arrival times that may represent karst features. Additional processing is used to enhances these features and map them in three-dimensions. The mapped features are compared with known karst features in the area (e.g. sinkholes) for ground-truth information. These methods may be used in the future for detection and classification of other near-surface voids. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  13. Seismic sequence stratigraphy of Tertiary sediments, offshore Sarawak deep-water area

    SciTech Connect

    Mohammad, A.M. )

    1994-07-01

    Tectonic processes and sea level changes are the main key factors that have strongly influenced clastic and carbonate sedimentations in the Sarawak deep-water area. A seismic sequence stratigraphy of Tertiary sediments was conducted in the area with the main objective of developing a workable genetic chronostratigraphic framework that defines the sequence and system tracts boundaries within which depositional systems and lithofacies can be identified, mapped and interpreted. This study has resulted in the identification of eight major depositional sequences that are bounded by regional unconformities and correlative conformities. These sequences can generally be grouped into four megasequences, based on the main tectonic events observed in the area. Three system tracts of a type-1, third-order sequence boundary were recognized in most of the sequences: lowstand, transgressive, and highstand systems tracts. The lowstand system tract includes basin-floor fans, slope fans, and lowstand prograding wedges. Paleoenvironmental distribution maps constructed for each of the sequences using seismic facies analysis and nearby well control suggest that the sequence intervals are predominantly transgressive units that have been intermittently interrupted by regressive pulses brought about by changes in eustatic sea level. The trend of paleocoastline observed during Oligocene to Miocene times changes from northwest-southeast orientation to a position roughly parallel to the present coastline. Seismic facies maps generated from late Oligocene to early Miocene indicate the depositional environment was coastal to coastal plain in the western and the middle part of the study area, becoming more marine toward the east and northeast.

  14. Evidence for activity of the Calabrian arc system and implications for historical seismicity in Eastern Sicily

    NASA Astrophysics Data System (ADS)

    Gallais, F.; Gutscher, M.-A.; Graindorge, D.; Polonia, A.

    2009-04-01

    The Wadati-Benioff zone under Calabria and the Tyrrhenian Sea is located in the centre of the Mediterranean Sea, a region characterized by complex tectonics. The presence of deep earthquakes under the Tyrrhenian Sea to a depth of 500 km, depicting an Ionian slab dipping about 70° towards the NW (Selvaggi and Chiarabba, 95), related with an active volcanic arc (the Aeolian Islands). The Calabrian peninsula is among the most seismically active regions in the Mediterranean area. Several historical seismic events, such as 1169 and 1693 earthquakes, reached MCS intensities of XI and are associated with destructive tsunami (Piatanesi and Tinti, 1998). The source of these two strongest earthquakes has still not been identified with certainty. The 1693 earthquake struck Eastern Sicily (60000 people killed) and generated a 5-10 m high tsunami (Piatanesi and Tinti, 1998). The 1169 earthquake had similar intensities and a comparable isoseismal pattern, suggesting an equivalent source. Because of the tsunami generated in 1693 and because the isoseismals are open to the sea, the source region appears to be offshore. The subduction fault plane would then be a good candidate for the 1693 event. However, a lack of instrumentally recorded thrust earthquakes, characteristic of active subduction zone, suggests that if subduction is active, the fault plane may be locked since the instrumental period. Reported recent GPS motions suggest that the subduction of the Ionian lithosphere beneath the Tyrrhenian basin plays an minor role in controlling the active deformation of the Eurasia-Nubia plate boundary, but may be locally still active in particular in the Calabrian arc (D'Agostino et al., 08). Moreover the offshore accretionary wedge is known to include compressional anticlines and ongoing hydrological activity (mud volcanoes). We present preliminary results from reprocessed 96-channels seismic reflection profiles acquired during the French "Archimede" cruise (1997) crossing the

  15. Recent high-resolution seismic reflection studies of active faults in the Puget Lowland

    NASA Astrophysics Data System (ADS)

    Liberty, L. M.; Pratt, T. L.

    2005-12-01

    In the past four years, new high-resolution seismic surveys have filled in key gaps in our understanding of active structures beneath the Puget Lowland, western Washington State. Although extensive regional and high-resolution marine seismic surveys have been fundamental to understanding the tectonic framework of the area, these marine profiles lack coverage on land and in shallow or restricted waterways. The recent high-resolution seismic surveys have targeted key structures beneath water bodies that large ships cannot navigate, and beneath city streets underlain by late Pleistocene glacial deposits that are missing from the waterways. The surveys can therefore bridge the gap between paleoseismic and marine geophysical studies, and test key elements of models proposed by regional-scale geophysical studies. Results from these surveys have: 1) documented several meters of vertical displacement on at least two separate faults in the Olympia area; 2) clarified the relationship between the Catfish Lake scarp and the underlying kink band in the Tacoma fault zone; 3) provided a first look at the structures beneath the north portion of the western Tacoma fault zone, north of previous marine profiles; 4) documented that deformation along the Seattle fault extends well east of Lake Sammamish; 5) imaged the Seattle fault beneath the Vasa Park trench; and 6) documented multiple fault strands in and south of the Seattle fault zone south of Bellevue. The results better constrain interpretations of paleoseismic investigations of past earthquakes on these faults, and provide targets for future paleoseismic studies.

  16. Active-source seismic imaging below Lake Malawi (Nyasa) from the SEGMeNT project

    NASA Astrophysics Data System (ADS)

    Shillington, D. J.; Scholz, C. A.; Gaherty, J. B.; Accardo, N. J.; McCartney, T.; Chindandali, P. R. N.; Kamihanda, G.; Trinhammer, P.; Wood, D. A.; Khalfan, M.; Ebinger, C. J.; Nyblade, A.; Mbogoni, G. J.; Mruma, A. H.; Salima, J.; Ferdinand-Wambura, R.

    2015-12-01

    central basins offset the youngest sediments, indicating that they are active. These include faults in the area of the 2009 Karonga earthquakes.

  17. Seismic tomography of the area of the 2010 Beni-Ilmane earthquake sequence, north-central Algeria.

    PubMed

    Abacha, Issam; Koulakov, Ivan; Semmane, Fethi; Yelles-Chaouche, Abd Karim

    2014-01-01

    The region of Beni-Ilmane (District of M'sila, north-central Algeria) was the site of an earthquake sequence that started on 14 May 2010. This sequence, which lasted several months, was triggered by conjugate E-W reverse and N-S dextral faulting. To image the crustal structure of these active faults, we used a set of 1406 well located aftershocks events and applied the local tomography software (LOTOS) algorithm, which includes absolute source location, optimization of the initial 1D velocity model, and iterative tomographic inversion for 3D seismic P- and S-wave velocities (and the Vp/Vs ratio), and source parameters. The patterns of P-wave low-velocity anomalies correspond to the alignments of faults determined from geological evidence, and the P-wave high-velocity anomalies may represent rigid blocks of the upper crust that are not deformed by regional stresses. The S-wave low-velocity anomalies coincide with the aftershock area, where relatively high values of Vp/Vs ratio (1.78) are observed compared with values in the surrounding areas (1.62-1.66). These high values may indicate high fluid contents in the aftershock area. These fluids could have been released from deeper levels by fault movements during earthquakes and migrated rapidly upwards. This hypothesis is supported by vertical sections across the study area show that the major Vp/Vs anomalies are located above the seismicity clusters. PMID:25485193

  18. Seismic hazard assessment in the Catania and Siracusa urban areas (Italy) through different approaches

    NASA Astrophysics Data System (ADS)

    Panzera, Francesco; Lombardo, Giuseppe; Rigano, Rosaria

    2010-05-01

    The seismic hazard assessment (SHA) can be performed using either Deterministic or Probabilistic approaches. In present study a probabilistic analysis was carried out for the Catania and Siracusa towns using two different procedures: the 'site' (Albarello and Mucciarelli, 2002) and the 'seismotectonic' (Cornell 1968; Esteva, 1967) methodologies. The SASHA code (D'Amico and Albarello, 2007) was used to calculate seismic hazard through the 'site' approach, whereas the CRISIS2007 code (Ordaz et al., 2007) was adopted in the Esteva-Cornell procedure. According to current international conventions for PSHA (SSHAC, 1997), a logic tree approach was followed to consider and reduce the epistemic uncertainties, for both seismotectonic and site methods. The code SASHA handles the intensity data taking into account the macroseismic information of past earthquakes. CRISIS2007 code needs, as input elements, a seismic catalogue tested for completeness, a seismogenetic zonation and ground motion predicting equations. Data concerning the characterization of regional seismic sources and ground motion attenuation properties were taken from the literature. Special care was devoted to define source zone models, taking into account the most recent studies on regional seismotectonic features and, in particular, the possibility of considering the Malta escarpment as a potential source. The combined use of the above mentioned approaches allowed us to obtain useful elements to define the site seismic hazard in Catania and Siracusa. The results point out that the choice of the probabilistic model plays a fundamental role. It is indeed observed that when the site intensity data are used, the town of Catania shows hazard values higher than the ones found for Siracusa, for each considered return period. On the contrary, when the Esteva-Cornell method is used, Siracusa urban area shows higher hazard than Catania, for return periods greater than one hundred years. The higher hazard observed

  19. Three-dimensional seismic interpretation: Espoir Field area, offshore Ivory Coast

    SciTech Connect

    Grillot, L.R.; Anderton, P.W.; Haselton, T.M.; Dermargne, J.F.

    1986-05-01

    The Espoir oil field, located approximately 13 km offshore Ivory Coast, was discovered in 1980 by a joint venture comprised of Phillips Petroleum Company, AGIP, SEDCO Energy, and PETROCI. Following the discovery, a three-dimensional seismic survey was recorded by GSI in 1981-1982 to provide detailed seismic coverage of Espoir field and adjacent features. The seismic program consisted of 7700 line-km of data acquired in a single survey area that is located on the edge of the continental shelf and extends into deep water. In comparison with previous two-dimensional seismic surveys, the three-dimensional data provided several improvements in interpretation and mapping including: (1) sharper definition of structural features, (2) reliable correlations of horizons and fault traces between closely spaced tracks, (3) detailed time contour maps from time-slice sections, and (4) improved velocity model for depth conversion. The improved mapping helped us identify additional well locations; the results of these wells compared favorably with the interpretation made prior to drilling.

  20. 3-D Seismic Tomographic Modelling of the North-Western Spitsbergen Area

    NASA Astrophysics Data System (ADS)

    Czuba, W.

    2015-12-01

    Deep seismic sounding measurements were performed in the continent-ocean transition zone of the north-western Svalbard continental margin in 1976 - 1999 in an international co-operation. Seismic energy (airgun and TNT shots) was recorded by land (onshore) seismic stations, ocean bottom seismometers (OBS), and ocean bottom hydrophone systems (OBH). Data from archival and modern seismic profiles were altogether used for 3-D tomographic inversion using JIVE3D software. The modelling area was chosen to be a rectangle of 420 x 330 km (Fig.). The results are similar to the earlier 2-D modelling, supplemented by off-line information from the profiles and the SPITS permanent station, giving a 3-D image of the crustal structure and Moho interface shape. The continental crust thins to the west and north. A minimum depth of about 6 km to the Moho discontinuity was found east of the Molloy Deep and in the Knipovich Ridge. The Moho interface deepens to about 30 km beneath the continental crust of Spitsbergen.

  1. Active deformation and seismicity in the Southern Alps (Italy): The Montello hill as a case study

    NASA Astrophysics Data System (ADS)

    Danesi, Stefania; Pondrelli, Silvia; Salimbeni, Simone; Cavaliere, Adriano; Serpelloni, Enrico; Danecek, Peter; Lovati, Sara; Massa, Marco

    2015-06-01

    The Montello anticline is a morphotectonic feature of the east pede-mountain of the South Alpine Chain in northern Italy, which lies ca. 40 km northwest of Venice, Italy. The purpose of this study is to characterize the present-day crustal deformation and seismotectonics of the Montello area through multi-parametric geophysical observations. We used new data obtained from the installation of a temporary network of 12 seismic stations and 6 GPS sites. The GPS observations indicate that there is ~ 1 mm/yr shortening across the Montello thrust. Sites located north of the Montello thrust front deviate from the ~ NNW-ward Adria-Eurasia convergence direction, as they are constrained by a relative rotation pole in northwestern Italy that has a NNE-ward motion trend. Over 18 months, seismographic recordings allowed us to locate 142 local seismic events with Ml 0.5-3.5 with good reliability (rms < 0.5). After cross-correlation analysis, we classified 42 of these events into six clusters, with cross-correlation thresholds > 0.80. The source focal solutions indicate that: (i) there is thrusting seismic activity on the basal, sub-horizontal, portion of the Montello structure; and (ii) strike-slip source kinematics prevail on the western edge of the Montello hill. Our observations on the source mechanisms and the measured crustal deformation confirm that the Montello thrust is tectonically active.

  2. GeoNetGIS: a Geodetic Network Geographical Information System to manage GPS networks in seismic and volcanic areas

    NASA Astrophysics Data System (ADS)

    Cristofoletti, P.; Esposito, A.; Anzidei, M.

    2003-04-01

    This paper presents the methodologies and issues involved in the use of GIS techniques to manage geodetic information derived from networks in seismic and volcanic areas. Organization and manipulation of different geodetical, geological and seismic database, give us a new challenge in interpretation of information that has several dimensions, including spatial and temporal variations, also the flexibility and brand range of tools available in GeoNetGIS, make it an attractive platform for earthquake risk assessment. During the last decade the use of geodetic networks based on the Global Positioning System, devoted to geophysical applications, especially for crustal deformation monitoring in seismic and volcanic areas, increased dramatically. The large amount of data provided by these networks, combined with different and independent observations, such as epicentre distribution of recent and historical earthquakes, geological and structural data, photo interpretation of aerial and satellite images, can aid for the detection and parameterization of seismogenic sources. In particular we applied our geodetic oriented GIS to a new GPS network recently set up and surveyed in the Central Apennine region: the CA-GeoNet. GeoNetGIS is designed to analyze in three and four dimensions GPS sources and to improve crustal deformation analysis and interpretation related with tectonic structures and seismicity. It manages many database (DBMS) consisting of different classes, such as Geodesy, Topography, Seismicity, Geology, Geography and Raster Images, administrated according to Thematic Layers. GeoNetGIS represents a powerful research tool allowing to join the analysis of all data layers to integrate the different data base which aid for the identification of the activity of known faults or structures and suggesting the new evidences of active tectonics. A new approach to data integration given by GeoNetGIS capabilities, allow us to create and deliver a wide range of maps, digital

  3. Assessment and surveillance of active seismic regions through time series satellite data

    NASA Astrophysics Data System (ADS)

    Zoran, M. A.; Savastru, R. S.; Savastru, D. M.

    2013-08-01

    Satellite time-series data, coupled with ground based observations where available, can enable scientists to survey pre-earthquake signals in the areas of strong tectonic activity. Cumulative stress energy in seismic active regions under operating tectonic force manifests various earthquakes' precursors. Space-time anomalies of Earth's emitted radiation (radon in underground water and soil, thermal infrared in spectral range measured from satellite months to weeks before the occurrence of earthquakes etc.), and electromagnetic anomalies are considered as pre-seismic signals. This energy transformation may result in enhanced transient thermal infrared (TIR) emission, which can be detected through satellites equipped with thermal sensors like AVHRR (NOAA), MODIS (Terra/Aqua). This paper presents observations made using time series NOAA-AVHRR and MODIS satellite data-derived land surface temperature (LST) and outgoing longwave radiation (OLR) values in case of 27th 2004 earthquake recorded in seismic Vrancea region, Romania, using anomalous TIR signals as reflected in LST rise and high OLR values which followed similar growth pattern spatially and temporally. In all analyzed cases, starting with almost one week prior to a moderate or strong earthquake a transient thermal infrared rise in LST of several Celsius degrees (°C) and the increased OLR values higher than the normal have been recorded around epicentral areas, function of the magnitude and focal depth, which disappeared after the main shock. As Vrancea area has a significant regional tectonic activity in Romania and Europe, the joint analysis of geospatial and in-situ geophysical information is revealing new insights in the field of hazard assessment.

  4. High-Resolution Seismic Reflection Studies of Active Faults: a Case Study from Washington State

    NASA Astrophysics Data System (ADS)

    Liberty, L. M.; Pratt, T. L.

    2007-12-01

    In the past five years, new high-resolution seismic surveys have filled in gaps in our understanding of active structures beneath the Puget Lowland region of Washington State. The extensive forests have made recognition of active faults difficult, but new Light Distance and Ranging (LIDAR) detailed topographic data have made a major breakthrough in mapping active faults. Extensive regional and high-resolution marine seismic surveys have been fundamental to understanding the tectonic framework of the area. These marine profiles, however, lack coverage beneath water bodies that large ships cannot navigate and beneath city streets underlain by late Pleistocene glacial deposits that are missing from the waterways. Recent land surveys and profiles in restricted waterways can therefore bridge the gap between paleoseismic and marine geophysical studies, and test elements of models proposed by regional-scale geophysical studies. We have also been venturing into more congested areas to seismically image faults in key urban locations. Results from recent surveys have: 1) documented new faults that had long been suspected in the Olympia area; 2) clarified the relationship between the LIDAR scarps and observed structures across the Tacoma fault zone; 3) provided a window into structures beneath the north and eastern portions of the western Tacoma fault zone; 4) documented deformation along the Seattle fault near a paleoseismic trench; 5) mapped the eastern part the Seattle fault zone beyond its previously mapped limits; and 6) documented multiple fault strands in the Seattle fault zone in the cities of Bellevue and Seattle. The results better constrain interpretations of paleoseismic data collected on these faults, and provide targets for future paleoseismic studies.

  5. An active seismic experiment at Tenerife Island (Canary Island, Spain): Imaging an active volcano edifice

    NASA Astrophysics Data System (ADS)

    Garcia-Yeguas, A.; Ibañez, J. M.; Rietbrock, A.; Tom-Teidevs, G.

    2008-12-01

    An active seismic experiment to study the internal structure of Teide Volcano was carried out on Tenerife, a volcanic island in Spain's Canary Islands. The main objective of the TOM-TEIDEVS experiment is to obtain a 3-dimensional structural image of Teide Volcano using seismic tomography and seismic reflection/refraction imaging techniques. At present, knowledge of the deeper structure of Teide and Tenerife is very limited, with proposed structural models mainly based on sparse geophysical and geological data. This multinational experiment which involves institutes from Spain, Italy, the United Kingdom, Ireland, and Mexico will generate a unique high resolution structural image of the active volcano edifice and will further our understanding of volcanic processes.

  6. Shear wave reflection seismic surveying in the Trondheim harbour area - imaging of land slide processes

    NASA Astrophysics Data System (ADS)

    Polom, U.; Hansen, L.; L'Heureux, S.; Longva, O.; Lecomte, I.; Krawczyk, C. M.

    2008-12-01

    The harbour area of Trondheim, Norway, was build on man-made land fillings at the coast of the Trondheim Fjord in several expansions since the last 80 years. The whole area is located on the deltaic sediments of the river Nidelven, which are overlying marine sediments that reach the bed rock in nearly 150 m depth. Some submarine land slides at the border of the sediment body nearby the harbour area were reported during the last decades. Therefore, many geological and geophysical investigations were carried out in recent years to explore the structure of the sediment body and its stability onshore and offshore in detail. Whereas high-resolution marine seismic methods archieved excellent results in the offshore area, common seismic investigations for the mostly paved harbour area itself were a difficult challenge. Therefore, SH polarized shear wave reflection seismics using a land streamer combined with a newly developed shear wave vibrator buggy of 30 kN peak force was applied, because this method is advantageous for paved surfaces. Overall 4.2 km 2.5D profiling was carried out in the harbour area along roads and parking places after optimizing of the field procedure. The whole operation was done at night in time slots from midnight to 5 am by road closures due to savety reasons and to minimize the noise from surrounding heavy traffic of trains, trucks and other heavy equipment. The field measurements achieved high resolution results of the sediment body structure, clear detection of the bedrock, and probably deeper structures within the bedrock. Due to the clear and continuous reflection events, also the shear wave velocity could be calculated at least down to the bedrock to indicate the stiffness of the sediment layers. The results of these onshore seismic profiles will be integrated in a combined onshore-offshore seismic profile grid for structural interpretation. Furthermore, the derived shear wave velocities will be combined with cone penetrometer testings and

  7. Effects of fracture contact areas on seismic attenuation due to wave-induced fluid flow

    NASA Astrophysics Data System (ADS)

    Germán Rubino, J.; Müller, Tobias M.; Milani, Marco; Holliger, Klaus

    2014-05-01

    Wave-induced fluid flow (WIFF) between fractures and the embedding matrix is considered to be a predominant seismic attenuation mechanism in fractured rocks. That is, due to the strong compressibility contrast between fractures and embedding matrix, seismic waves induce strong fluid pressure gradients, followed by local fluid flow between such regions, which in turn produces significant energy dissipation. Natural fractures can be conceptualized as two surfaces in partial contact, containing very soft and highly permeable material in the inner region. It is known that the characteristics of the fracture contact areas control the mechanical properties of the rock sample, since as the contact area increases, the fracture becomes stiffer. Correspondingly, the detailed characteristics of the contact area of fractures are expected to play a major role in WIFF-related attenuation. To study this topic, we consider a simple model consisting of a horizontal fracture located at the center of a porous rock sample and represented by a number of rectangular cracks of constant height separated by contact areas. The cracks are modelled as highly compliant, porous, and permeable heterogeneities, which are hydraulically connected to the background material. We include a number of rectangular regions of background material separating the cracks, which represent the presence of contact areas of the fracture. In order to estimate the WIFF effects, we apply numerical oscillatory relaxation tests based on the quasi-static poro-elastic equations. The equivalent undrained, complex plane-wave modulus, which allows to estimate seismic attenuation and velocity dispersion for the vertical direction of propagation, is expressed in terms of the imposed displacement and the resulting average vertical stress at the top boundary. In order to explore the effects of the presence of fracture contact areas on WIFF effects, we perform an exhaustive sensitivity analysis considering different

  8. The role of the Montello hill in the seismicity and active deformation of Southern Alps

    NASA Astrophysics Data System (ADS)

    Pondrelli, S.; Serpelloni, E.; Danesi, S.; Lovati, S.; Massa, M.; Mastrolembo Ventura, B.; Danecek, P.; Cavaliere, A.; Salimbeni, S.

    2013-12-01

    The most remarkable geomorphological feature of the eastern Southern Alps (northern Italy) is the Montello anticline, a ~15km long SSW-NNE elongated hill, sited ~40km north of Venice, and offset of ~15 km to the south from the main pede-Alpine thrust front. It has been generated by the uplift and the deformation produced by a S-verging blind thrust, constrained by morphotectonic analyses of uplifted river terraces and sub-surface data. Despite it is presently considered as one of the main S-verging seismogenic segments of the tectonically active Southern Alps thrust front, its real seismogenic potential is still matter of debate. Although the area has been hit in 1695 by a Mw 6.5 earthquake, the Montello is currently characterized by slower seismicity activity than its confining segments and geodetic deformation rates are at the mm/yr level. In order to study the present day crustal deformation at the fault-scale and to improve the detection of background seismicity associated to the 'seismically silent' Montello thrust and to understand its interseismic behavior, we have installed a temporary multi-parametric geophysical network, which integrates space geodetic (GPS) and seismological observations during the 2010-2011 time-interval, running semi-continuous GPS experiments from 2009 to 2013. We recorded 142 local events (compared to the 43 events located by the Italian Seismic Network), located with good reliability (rms < 0.5) with Ml between 1.5 and 3.5. The available continuous and semi-continuous GPS data show that ~2 mm/yr of N-S convergence are accommodated across this sector of the Southern Alps, but the deformation signal appears more complex than what expected by a single thrust fault. GPS, although preliminary and not sampling optimally possible lateral variations of the strain-rate field, show a remarkable change of the kinematics across the external Montello thrust front. The GPS and seismological data collected during the experiment suggest that the

  9. Assessing low-activity faults for the seismic safety of dams

    SciTech Connect

    Page, W.D.; Savage, W.U.; McLaren, M.K.

    1995-12-31

    Dams have been a familiar construct in the northern Sierra Nevada range in California (north of the San Joaquin River) since the forty-niners and farmers diverted water to their gold mines and farms in the mid 19th century. Today, more than 370 dams dot the region from the Central Valley to the eastern escarpment. Fifty-five more dam streams on the eastern slope. The dams are of all types: 240 earth fill; 56 concrete gravity; 45 rock and earth fills; 35 rock fill; 14 concrete arch; 9 hydraulic fill; and 29 various other types. We use the northern Sierra Nevada to illustrate the assessment of low-activity faults for the seismic safety of dams. The approach, techniques, and methods of evaluation are applicable to other regions characterized by low seismicity and low-activity faults having long recurrence intervals. Even though several moderate earthquakes had shaken the Sierra Nevada since 1849 (for example, the 1875 magnitude 5.8 Honey Lake and the 1909 magnitudes 5 and 5.5 Downieville earthquakes), seismic analyses for dams in the area generally were not performed prior to the middle of this century. Following the 1971 magnitude 6.7 San Fernando earthquake, when the hydraulic-fill Lower Van Norman Dam in southern California narrowly escaped catastrophic failure, the California Division of Safety of Dams and the Federal Energy Regulatory Commission required seismic safety to be addressed with increasing rigor. In 1975, the magnitude 5.7 Oroville earthquake on the Cleveland Hill fault near Oroville Dam in the Sierra Nevada foothills, showed convincingly that earthquakes and surface faulting could occur within the range. Following this event, faults along the ancient Foothills fault system have been extensively investigated at dam sites.

  10. Seismicity, seismotectonics and crustal structure of the southern Kenya Rift-new data from the Lake Magadi area

    NASA Astrophysics Data System (ADS)

    Ibs-von Seht, M.; Blumenstein, S.; Wagner, R.; Hollnack, D.; Wohlenberg, J.

    2001-08-01

    Local seismic activity has been monitored in the southern part of the Kenya Rift in the area around Lake Magadi. An earthquake recording network consisting of 15 station sites was operated for 8months from November 1997 to June 1998. During this period, the Magadi area proved to be seismically active. Approximately 10 events per day were detected and found to be equally distributed over the rift floor. The hypocentre depth distribution shows surprisingly large depths of up to 27km in the south and much shallower depths in the northern part of the area. Apart from the background activity, swarm activity with rates of more than 300 events per day was also recorded. The epicentres are clustered and trace a linear structure lying SSW-NNE over a length of 10km north of Lake Magadi. Hypocentres in the region of the earthquake cluster are shallow and exhibit a sharp cut-off at 9km depth. A surface crack that occurred during the recording period is connected to the earthquake swarm. Analysis of the focal mechanisms of selected earthquakes indicates predominantly normal faulting in response to a WNW-ESE-directed tensional stress field. This direction corresponds to the general alignment of the southernmost part of the Kenya Rift and to the surface faulting pattern inside the rift. The crustal structure of the area has been investigated using local earthquake tomography and the spatial distribution of hypocentres. The main results of the tomography are a linear positive velocity anomaly following the rift axis and a negative anomaly at shallow depth underneath Lake Magadi. The high velocities can be explained by mafic material that has intruded into the upper crust. The negative anomaly is attributed to highly fractured rocks. Maximum hypocentre depths indicate a body of low shear strength centred at the rift axis and a general deepening of the brittle-ductile transition from north to south.

  11. Present activity and seismogenic potential of a low-angle normal fault system (Città di Castello, Italy): Constraints from surface geology, seismic reflection data and seismicity

    NASA Astrophysics Data System (ADS)

    Brozzetti, Francesco; Boncio, Paolo; Lavecchia, Giusy; Pace, Bruno

    2009-01-01

    We present new constraints on an active low-angle normal fault system in the Città di Castello-Sansepolcro basin (CSB) of the northern Apennines of Italy. New field data from the geological survey of the Carta Geologica d' Italia (CARG project) define the surface geometry of the normal fault system and lead to an interpretation of the CROP 03 deep-crust seismic reflection profile (Castiglion Fiorentino-Urbania segment), with particular attention paid to the geometry of the Plio-Quaternary extensional structures. Surface and sub-surface geological data are integrated with instrumental and historical seismicity in order to define the seismotectonics of the area. Low-angle east-dipping reflectors are the seismic expression of the well-known Altotiberina Fault (AF), a regional extensional detachment on which both east- and west-dipping high-angle faults, bounding the CSB, sole out. The AF breakaway zone is located ˜ 10 km west of the CSB. Within the extensional allochthon, synthetic east-dipping planes prevail. Displacement along the AF is ˜ 4.5 km, which agrees with the cumulative offset due to its synthetic splays. The evolution of the CSB has mainly been controlled by the east-dipping fault system, at least since Early Pleistocene time; this system is still active and responsible for the seismicity of the area. A low level of seismic activity was recorded instrumentally within the CSB, but several damaging earthquakes have occurred in historical times. The instrumental seismicity and the intensity data points of the largest historical earthquakes (5 events with maximum MCS intensity of IX to IX-X) allow us to propose two main seismogenic structures: the Monte Santa Maria Tiberina (Mmax = 5.9) and Città di Castello (Mmax up to 6.5) normal faults. Both are synthetic splays of the AF detachment, dipping to the NE at moderate (45-50°) to low (25-30°) angles and cutting the upper crust up to the surface. This study suggests that low-angle normal faults (at least

  12. Variation in harbour porpoise activity in response to seismic survey noise.

    PubMed

    Pirotta, Enrico; Brookes, Kate L; Graham, Isla M; Thompson, Paul M

    2014-05-01

    Animals exposed to anthropogenic disturbance make trade-offs between perceived risk and the cost of leaving disturbed areas. Impact assessments tend to focus on overt behavioural responses leading to displacement, but trade-offs may also impact individual energy budgets through reduced foraging performance. Previous studies found no evidence for broad-scale displacement of harbour porpoises exposed to impulse noise from a 10 day two-dimensional seismic survey. Here, we used an array of passive acoustic loggers coupled with calibrated noise measurements to test whether the seismic survey influenced the activity patterns of porpoises remaining in the area. We showed that the probability of recording a buzz declined by 15% in the ensonified area and was positively related to distance from the source vessel. We also estimated received levels at the hydrophones and characterized the noise response curve. Our results demonstrate how environmental impact assessments can be developed to assess more subtle effects of noise disturbance on activity patterns and foraging efficiency. PMID:24850891

  13. Variation in harbour porpoise activity in response to seismic survey noise

    PubMed Central

    Pirotta, Enrico; Brookes, Kate L.; Graham, Isla M.; Thompson, Paul M.

    2014-01-01

    Animals exposed to anthropogenic disturbance make trade-offs between perceived risk and the cost of leaving disturbed areas. Impact assessments tend to focus on overt behavioural responses leading to displacement, but trade-offs may also impact individual energy budgets through reduced foraging performance. Previous studies found no evidence for broad-scale displacement of harbour porpoises exposed to impulse noise from a 10 day two-dimensional seismic survey. Here, we used an array of passive acoustic loggers coupled with calibrated noise measurements to test whether the seismic survey influenced the activity patterns of porpoises remaining in the area. We showed that the probability of recording a buzz declined by 15% in the ensonified area and was positively related to distance from the source vessel. We also estimated received levels at the hydrophones and characterized the noise response curve. Our results demonstrate how environmental impact assessments can be developed to assess more subtle effects of noise disturbance on activity patterns and foraging efficiency. PMID:24850891

  14. Seismic acquisition and processing methodologies in overthrust areas: Some examples from Latin America

    SciTech Connect

    Tilander, N.G.; Mitchel, R..

    1996-08-01

    Overthrust areas represent some of the last frontiers in petroleum exploration today. Billion barrel discoveries in the Eastern Cordillera of Colombia and the Monagas fold-thrust belt of Venezuela during the past decade have highlighted the potential rewards for overthrust exploration. However the seismic data recorded in many overthrust areas is disappointingly poor. Challenges such as rough topography, complex subsurface structure, presence of high-velocity rocks at the surface, back-scattered energy and severe migration wavefronting continue to lower data quality and reduce interpretability. Lack of well/velocity control also reduces the reliability of depth estimations and migrated images. Failure to obtain satisfactory pre-drill structural images can easily result in costly wildcat failures. Advances in the methodologies used by Chevron for data acquisition, processing and interpretation have produced significant improvements in seismic data quality in Bolivia, Colombia and Trinidad. In this paper, seismic test results showing various swath geometries will be presented. We will also show recent examples of processing methods which have led to improved structural imaging. Rather than focusing on {open_quotes}black box{close_quotes} methodology, we will emphasize the cumulative effect of step-by-step improvements. Finally, the critical significance and interrelation of velocity measurements, modeling and depth migration will be explored. Pre-drill interpretations must ultimately encompass a variety of model solutions, and error bars should be established which realistically reflect the uncertainties in the data.

  15. Re-processing and interpretation of 2D seismic data from the Kristineberg mining area, northern Sweden

    NASA Astrophysics Data System (ADS)

    Ehsan, Siddique Akhtar; Malehmir, Alireza; Dehghannejad, Mahdieh

    2012-05-01

    The Kristineberg mining area in the western part of the Skellefte ore district, northern Sweden, contains the largest massive sulphide deposit in the district. In 2003, two parallel seismic lines, Profiles 1 and 5, each about 25 km long and about 8 km apart were acquired in the Kristineberg area. The initial processing results were successful in imaging the large-scale structures of the area down to 12 km of the crust, but resulted in relatively poor seismic image near the mine. In this paper, we re-processed the seismic data along Profile 1 that crosses the mine. The main objective was to improve the seismic section near the mine for further correlation with new seismic data recently acquired in the area. The crooked-line acquisition geometry, very low fold coverage of less than 17, complex geology and sparse outcrops in the area made the data re-processing and interpretation challenging. Despite these challenges, significant improvement is observed in the seismic data, in terms of event continuity and resolution. Refraction static corrections allowed high frequencies to be retained, which improved the seismic section. The refraction static solution was manually checked and adjusted at every iteration to avoid unstable solutions. 3D visualization of the re-processed data with other seismic profiles recently acquired in the area allowed the seismic reflections to be correlated. The majority of the reflections are interpreted to originate from either fault zones or lithological contacts. A very shallow reflection correlates well with the location of the Kristineberg mineralized horizon.

  16. Aftershock and induced seismic activity of the 2011 off the Pacific coast of Tohoku Earthquake in the northern part of Tohoku district, NE Japan

    NASA Astrophysics Data System (ADS)

    Kosuga, M.; Watanabe, K.

    2011-12-01

    We investigated the seismic activity around the northern neighbor of the 2011 off the Pacific coast of Tohoku Earthquake (Mw 9.0) with special attention to a potential large aftershock in the area. We obtained a combined data set by adding our manually-picked locations to the catalog locations by the Japan Meteorological Agency. The hypocenter distribution delineates active and inactive bands of seismicity. The band of low seismicity corresponds to a zone of a large seismic slip, indicating that aftershocks occurred in peripheral neighbors of the mainshock asperity. The broad band of active seismicity along the coast corresponds to the zone of a large postseismic slip, suggesting the enhancement of the aftershock activity by the slip. Although the northern neighbor of the mainshock fault is a favored region of increased seismicity, as shown from a Coulomb stress calculation, no significant seismic activity is observed within the potential source area except along the Japan Trench and the SW corner. This implies that the zone of interplate moment release by previous large earthquakes and the subsequent slow slip acted as a barrier to the migration of both the mainshock rupture and aftershock activity. However, an aftershock area in the zone may reflect inhomogeneous moment release by past seismic and aseismic sequences. Induced inland seismicity is quite high in the Akita Prefecture on the Japan Sea side apart more than 100 km from the mainshock fault. There are some active clusters including moderate earthquakes with magnitude greater than 5. They are newly formed clusters after the mainshock, while the seismicity of previously active areas decreased significantly. Focal mechanism solutions of earthquakes in the new clusters show the types of strike-slip with consistently NW-SE trending T-axes. The predominant type of focal mechanisms in the Akita area before the mainshock was E-W compressional reverse faulting. Thus the stress field in the area has changed

  17. A Multi-Step Assessment Scheme for Seismic Network Site Selection in Densely Populated Areas

    NASA Astrophysics Data System (ADS)

    Plenkers, Katrin; Husen, Stephan; Kraft, Toni

    2015-10-01

    We developed a multi-step assessment scheme for improved site selection during seismic network installation in densely populated areas. Site selection is a complex process where different aspects (seismic background noise, geology, and financing) have to be taken into account. In order to improve this process, we developed a step-wise approach that allows quantifying the quality of a site by using, in addition to expert judgement and test measurements, two weighting functions as well as reference stations. Our approach ensures that the recording quality aimed for is reached and makes different sites quantitatively comparable to each other. Last but not least, it is an easy way to document the decision process, because all relevant parameters are listed, quantified, and weighted.

  18. Geological and tectonic implications obtained from first seismic activity investigation around Lembang fault

    NASA Astrophysics Data System (ADS)

    Afnimar; Yulianto, Eko; Rasmid

    2015-12-01

    The Lembang fault located at northern part of populated Bandung basin is the most conspicuous fault that potentially capable in generating earthquakes. The first seismic investigation around Lembang fault has been done by deploying a seismic network from May 2010 till December 2011 to estimate the seismic activities around that fault. Nine events were recorded and distributed around the fault. Seven events were likely to be generated by the Lembang fault and two events were not. The events related to the Lembang fault strongly suggest that this fault has left-lateral kinematic. It shows vector movement of Australian plate toward NNE might have been responsible for the Lembang fault kinematic following its initial vertical gravitational movement. The 1-D velocity model obtained from inversion indicates the stratigraphy configuration around the fault composed at least three layers of low Vp/Vs at the top, high Vp/Vs at the middle layer and moderate Vp/Vs at the bottom. In comparison with general geology of the area, top, mid and bottom layers may consecutively represent Quaternary volcanic layer, pre-Quaternary water-filled sedimentary layer and pre-Quaternary basement. Two eastern events related to minor faults and were caused by a gravitational collapse.

  19. ActiveSeismoPick3D - automatic first arrival determination for large active seismic arrays

    NASA Astrophysics Data System (ADS)

    Paffrath, Marcel; Küperkoch, Ludger; Wehling-Benatelli, Sebastian; Friederich, Wolfgang

    2016-04-01

    We developed a tool for automatic determination of first arrivals in active seismic data based on an approach, that utilises higher order statistics (HOS) and the Akaike information criterion (AIC), commonly used in seismology, but not in active seismics. Automatic picking is highly desirable in active seismics as the number of data provided by large seismic arrays rapidly exceeds of what an analyst can evaluate in a reasonable amount of time. To bring the functionality of automatic phase picking into the context of active data, the software package ActiveSeismoPick3D was developed in Python. It uses a modified algorithm for the determination of first arrivals which searches for the HOS maximum in unfiltered data. Additionally, it offers tools for manual quality control and postprocessing, e.g. various visualisation and repicking functionalities. For flexibility, the tool also includes methods for the preparation of geometry information of large seismic arrays and improved interfaces to the Fast Marching Tomography Package (FMTOMO), which can be used for the prediction of travel times and inversion for subsurface properties. Output files are generated in the VTK format, allowing the 3D visualization of e.g. the inversion results. As a test case, a data set consisting of 9216 traces from 64 shots was gathered, recorded at 144 receivers deployed in a regular 2D array of a size of 100 x 100 m. ActiveSeismoPick3D automatically checks the determined first arrivals by a dynamic signal to noise ratio threshold. From the data a 3D model of the subsurface was generated using the export functionality of the package and FMTOMO.

  20. Active Tectonics of off-Hokuriku, Central Japan, by two ships seismic reflection profiling

    NASA Astrophysics Data System (ADS)

    Kato, Naoko; Sato, Hiroshi; Ishiyama, Tatsuya; Abe, Susumu; Shiraishi, Kazuya

    2015-04-01

    Along the southern to eastern margin of the Sea of Japan, active faults are densely distributed. These submarine active faults produced tsunami disasters, such as 1983 Nihonkai-chubu earthquake (M7.7) and 1993 Hokkaido Nansei-oki earthquake (M7.8). To estimate tsunami hazards, we performed deep seismic reflection profiling to obtain the information of tsunami source faults, off-Hokuriku area in the central part of Honshu, Japan. The survey is carried out as a part of research project named "the integrated research project on seismic and tsunami hazards around the Sea of Japan" funded by MEXT. To obtain long offset data in busy marine activity area, we used two vessels; a gun-ship with 3020 cu. inch air-gun and a cable-ship with a 2-km-long, streamer cable with 156 channels and 480 cu. inch air-gun. Common-midpoint reflection data were acquired using two ships at 4 km offset. The survey area consists of stretched continental crust associated with rifting and opening of the Sea of Japan in early Miocene and is marked by densely distributed syn-rift normal faults. Fault reactivation of normal faults as reverse faults is common. Two phases of fault reactivation are identified from the seismic sections after termination of opening of the Sea of Japan. One is the late Miocene NS trending shortening deformation. This is produced by NS-trending convergence of the Shikoku basin (15 Ma), which belongs to the Philippine Sea plate (PHS) to SW Japan at Nankai trough (Kimura et al., 2005). After the initiation of the subduction of PHS at Nankai trough, the strong shortening deformation is terminated and the fold-and-thrust belt was unconformably covered by sub-horizontal Pliocene sediments. Some horizons of unconformities represent multiple events of shortening driven from the subduction interface. Some normal faults reactivated as active strike-slip and reverse faults in Quaternary. Well observed example is the 2007 Noto peninsula earthquake (M6.8). The 2007 Noto peninsula

  1. Active faults in the deformation zone off Noto Peninsula, Japan, revealed by high- resolution seismic profiles

    NASA Astrophysics Data System (ADS)

    Inoue, T.; Okamura, Y.; Murakami, F.; Kimura, H.; Ikehara, K.

    2008-12-01

    Recently, a lot of earthquakes occur in Japan. The deformation zone which many faults and folds have concentrated exists on the Japan Sea side of Japan. The 2007 Noto Hanto Earthquake (MJMA 6.9) and 2007 Chuetsu-oki Earthquake (MJMA 6.8) were caused by activity of parts of faults in this deformation zone. The Noto Hanto Earthquake occurred on 25 March, 2007 under the northwestern coast of Noto Peninsula, Ishikawa Prefecture, Japan. This earthquake is located in Quaternary deformation zone that is continued from northern margin of Noto Peninsula to southeast direction (Okamura, 2007a). National Institute of Advanced Industrial Science and Technology (AIST) carried out high-resolution seismic survey using Boomer and 12 channels short streamer cable in the northern part off Noto Peninsula, in order to clarify distribution and activities of active faults in the deformation zone. A twelve channels short streamer cable with 2.5 meter channel spacing developed by AIST and private corporation is designed to get high resolution seismic profiles in shallow sea area. The multi-channel system is possible to equip on a small fishing boat, because the data acquisition system is based on PC and the length of the cable is short and easy to handle. Moreover, because the channel spacing is short, this cable is very effective for a high- resolution seismic profiling survey in the shallow sea, and seismic data obtained by multi-channel cable can be improved by velocity analysis and CDP stack. In the northern part off Noto Peninsula, seismic profiles depicting geologic structure up to 100 meters deep under sea floor were obtained. The most remarkable reflection surface recognized in the seismic profiles is erosion surface at the Last Glacial Maximum (LGM). In the western part, sediments about 30 meters (40 msec) thick cover the erosional surface that is distributed under the shelf shallower than 100m in depth and the sediments thin toward offshore and east. Flexures like deformation in

  2. Impact of the 2001 Tohoku-oki earthquake to Tokyo Metropolitan area observed by the Metropolitan Seismic Observation network (MeSO-net)

    NASA Astrophysics Data System (ADS)

    Hirata, N.; Hayashi, H.; Nakagawa, S.; Sakai, S.; Honda, R.; Kasahara, K.; Obara, K.; Aketagawa, T.; Kimura, H.; Sato, H.; Okaya, D. A.

    2011-12-01

    tomography of P- and S- wave structure, seismic interferometry for shallow structure and using the dense MeSO-net data. We observed the 2011 Tohoku-oki event and its aftershocks including M7.7 event off Ibaraki prefecture, which is the largest aftershock so far. We imaged source radiation energy using the MeSO-net data by the back-projection method (Honda et al., 2011). We found seismic activity in the Kanto region has been activated after the event, suggesting increased seismic hazard in Kanto region even for plate boundary events. We use a new image of PSP and Pacific plate. We evaluate potential zones of the M7+ earthquake on the plate boundary and within the PSP slab which will be used for risk mitigation study by a socio-science group. We will also discuss a future plan to continue our effort in seismic risk mitigation in Tokyo Metropolitan area, stress regime of which is seriously changed by the Tohoku-oki event. This is supported by the Special Project for Earthquake Disaster Mitigation in Tokyo Metropolitan Area

  3. Seismic Activity: Public Alert and Warning: Legal Implications

    NASA Astrophysics Data System (ADS)

    Zocchetti, D.

    2007-12-01

    As science and technology evolve in ways that increase our ability to inform the public of potentially destructive seismic activity, there are significant legal issues for consideration. Even though countries and even states within the United States have differing legal tenets that could either change or at least re-shape the outcome of specific legal questions that this session will be pondering, there are fundamental legal principals that will permeate. It is often said that the law lags behind society and in particular its technological developments. No doubt in the area of warning the public of impending destructive forces of nature or society, the law will need to do some catching up. The law is probably adequately developed for at least some preliminary discussion of the key issues. No matter the legal scheme, if there is a failure or perceived failure in the system to warn people of a pending emergencies, albeit an earthquake, tsunami, or other predictable event, those who are harmed or believe they are harmed will seek relief under the law. Every day there are situations wherein the failure to warn or to adequately warn is key, such as with faulty or defective consumer products, escaped prisoners, and police high-speed vehicle chases. With alert and warning systems for disaster, however, we have a unique set of facts. Generally, the systems and their failures occur during emergencies or at least during situations under apparently exigent circumstances when the disaster's predictability is widely recognized as less than 100 percent. The law, in particular United States tort law, has been particularly lenient when people and organizations are operating during compressed timeframes and their actions are generally considered necessary to address circumstances relative to public safety. The legal system has been forgiving when the actor that failed or appeared to fail was government. The courts have liberally applied the principal of sovereign immunity to

  4. Slope-area and stream length index analysis in the eastern Tennessee seismic zone: evidence for differential uplift?

    NASA Astrophysics Data System (ADS)

    Stearns, C.; Arroucau, P.; Vlahovic, G.

    2013-12-01

    Previous studies have shown that Digital Elevation Model (DEM) analysis could be used to quantify surface deformation in tectonically active regions, including slowly deforming areas such as intraplate continental interiors. Here, we investigate slope/area relationships and determine stream length index (SLI) spatial variations in 287 watersheds located in the Valley and Ridge physiographic province of the southern Appalachians, in a region known as the eastern Tennessee seismic zone (ETSZ). The goal is to identify possible spatial variations in drainage network characteristics that could reveal different deformation rates and styles within the study area. The ETSZ, although seismically active, does not show any evidence of recent surface deformation that could be related to tectonic activity. The earthquakes mostly occur between 5 and 25 km depth and their epicenters form a SSW-NNE trending, 300 km long by 100 km wide, band of diffuse seismicity that aligns along the New York Alabama (NYAL) magnetic lineament, a linear magnetic feature attributed to a fault affecting the Precambrian basement but without signature at the surface. DEMs with a resolution of 30 meters and watershed boundaries of 287 drainage basins were obtained from the United States Geological Survey (USGS) National Elevation Dataset (NED) and National Hydrography Dataset (NHD), respectively. After determining the local slope and drainage area for each 30 m x 30 m cell, reference concavity and steepness index values were calculated for the entire region. Then, the steepness index of each watershed was determined using the obtained reference concavity index. SLI values were also determined along extracted river profiles and average values calculated for each watershed. A good correlation is observed between steepness index and SLI, with low to mid-range values found in the Valley and Ridge province and higher values in two specific areas: at the transition between the Valley and Ridge province and

  5. Apollo 14 and 16 Active Seismic Experiments, and Apollo 17 Lunar Seismic Profiling

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Seismic refraction experiments were conducted on the moon by Apollo astronauts during missions 14, 16, and 17. Seismic velocities of 104, 108, 92, 114 and 100 m/sec were inferred for the lunar regolith at the Apollo 12, 14, 15, 16, and 17 landing sites, respectively. These data indicate that fragmentation and comminution caused by meteoroid impacts has produced a layer of remarkably uniform seismic properties moonwide. Brecciation and high porosity are the probable causes of the very low velocities observed in the lunar regolith. Apollo 17 seismic data revealed that the seismic velocity increases very rapidly with depth to 4.7 km/sec at a depth of 1.4 km. Such a large velocity change is suggestive of compositional and textural changes and is compatible with a model of fractured basaltic flows overlying anorthositic breccias. 'Thermal' moonquakes were also detected at the Apollo 17 site, becoming increasingly frequent after sunrise and reaching a maximum at sunset. The source of these quakes could possibly be landsliding.

  6. Evaluation of feasibility of mapping seismically active faults in Alaska

    NASA Technical Reports Server (NTRS)

    Gedney, L. D. (Principal Investigator); Vanwormer, J. D.

    1973-01-01

    The author has identified the following significant results. ERTS-1 imagery is proving to be exceptionally useful in delineating structural features in Alaska which have never been recognized on the ground. Previously unmapped features such as seismically active faults and major structural lineaments are especially evident. Among the more significant results of this investigation is the discovery of an active strand of the Denali fault. The new fault has a history of scattered activity and was the scene of a magnitude 4.8 earthquake on October 1, 1972. Of greater significance is the disclosure of a large scale conjugate fracture system north of the Alaska Range. This fracture system appears to result from compressive stress radiating outward from around Mt. McKinley. One member of the system was the scene of a magnitude 6.5 earthquake in 1968. The potential value of ERTS-1 imagery to land use planning is reflected in the fact that this earthquake occurred within 10 km of the site which was proposed for the Rampart Dam, and the fault on which it occurred passes very near the proposed site for the bridge and oil pipeline crossing of the Yukon River.

  7. Impacts of seismic activity on long-term repository performance at Yucca Mountain

    SciTech Connect

    Gauthier, J.H.; Wilson, M.L.; Borns, D.J.; Arnold, B.W.

    1995-12-31

    Several effects of seismic activity on the release of radionuclides from a potential repository at Yucca Mountain are quantified. Future seismic events are predicted using data from the seismic hazard analysis conducted for the Exploratory Studies Facility (ESF). Phenomenological models are developed, including rockfall (thermal-mechanical and seismic) in unbackfilled emplacement drifts, container damage caused by fault displacement within the repository, and flow-path chance caused by changes in strain. Using the composite-porosity flow model (relatively large-scale, regular percolation), seismic events show little effect on total-system releases; using the weeps flow model (episodic pulses of flow in locally saturated fractures), container damage and flow-path changes cause over an order of magnitude increase in releases. In separate calculations using, more realistic representations of faulting, water-table rise caused by seismically induced changes in strain are seen to be higher than previously estimated by others, but not sufficient to reach a potential repository.

  8. Crustal Fluid Distribution in the Source Area of the 2008 Iwate-Miyagi Nairiku Earthquake, NE Japan Inferred from Seismic Tomography

    NASA Astrophysics Data System (ADS)

    Okada, T.

    2014-12-01

    Seismic tomography is an important tool for detecting the distibution of magma and other crustal fluids. In this presentation, we show the results of seismic tomography, in an area that includes the Naruko volcano and the 2008 Iwate-Miyagi Nairiku earthquake, using data from a dense temporary seismic network, and discuss the crustal fluid distribution related to the volcanic and seismic activity. The seismic velocity structure is complex within the crust and we found distinct seismic low-velocity zones (LVZs). In the shallow crust, the LVZ is located beneath each volcano (Naruko, Onikobe, and Kurikoma) in the focal area of the 2008 Iwate-Miyagi Nairiku Earthquake.In the middle to deep crust (10-20 km), a distinct LVZ beneath the volcanic front can be observed. This LVZ seems to be continuously distributed in the NNE-SSW direction, from the Yakeishi to the Naruko volcano. The lateral extent of the LVZ in the NNE-SSW direction is almost the same as the lateral extent of the aftershock area of the 2008 Iwate-Miyagi Nairiku earthquake. Some low-V areas in the upper crust have high Vp/Vs areas. The aseismic low-V and high-Vp/Vs areas just beneath the volcanoes could correspond to an area with molten magma. We also found some low-V and high Vp/Vs areas with seismicity in the upper crust. Possible reason for this low-V and relatively high-Vp/Vs area could be the presence of overpressurized fluid. For a misoriented compressional inversion fault, reduction of fault strength by overpressurized fluid along the fault is a possible cause for reactivation (Sibson 1990; Sibson 2009). The fault plane of the 2008 Iwate-Miyagi Nairiku earthquake is thought to be as compressional inversion fault (Sibson, 2009). Compressional inversion fault is the reverse fault along the pre-existing "normal" fault. The complex distribution of the aftershock alignment (i.e. fault) has been spatially correlated with the distribution of the LVZ. This suggests that the fluid path distribution could have

  9. Seismically Articulating Kilauea Volcano's Active Conduits, Rift Zones, and Faults through HVO's Second Fifty Years

    NASA Astrophysics Data System (ADS)

    Okubo, P.; Nakata, J.; Klein, F.; Koyanagi, R.; Thelen, W.

    2011-12-01

    While seismic monitoring of active Hawaiian volcanoes began 100 years ago, the build-up of the U. S. Geological Survey's (USGS) Hawaiian Volcano Observatory (HVO) seismographic network to its current configuration began in 1955, when Jerry Eaton established remote stations that telemetered data via landline to recorders at HVO. With network expansion through the 1960's, earthquake location and cataloging capabilities have evolved to afford a computer processed seismic catalog now spanning fifty years. Location accuracy and catalog completeness to smaller magnitudes have increased. Research and insights developed using HVO's seismic record have exploited the ability to seismically monitor volcanic activity at depth, to identify active regions within the volcanoes on the basis of computed hypocentral locations, to infer regions of magma storage by recognizing different families of volcanic earthquakes, and to forecast volcanic activity in both short and longer term from seismicity patterns. HVO's seismicity catalog was central to calculations of probabilistic seismic hazards. The ability to develop and implement additional analytical and interpretive capabilities has kept pace with improvements in both field and laboratory hardware and software. While the basic capabilities continue as part of HVO's core monitoring, additional interpretive capabilities now include adding details of volcanic and earthquake source regions, and viewing seismic data in juxtaposition with other observatory data streams. As HVO looks to its next century of volcano studies, research and development continue to shape the future. Broadband seismic recording at HVO has enabled extensive study by Chouet, Dawson, and co-workers of the relationship of very-long-period seismic sources beneath Kilauea's summit caldera to magma supply and transport. Recent upgrades have improved the ability to use these data in seismic cataloging and research. Data processing upgrades have bolstered the ability to

  10. Seismic response of ore deposits in Kevitsa and Outokumpu mining areas: new insights from data mining and seismic forward modeling

    NASA Astrophysics Data System (ADS)

    Hellqvist, Niina; Koivisto, Emilia; Komminaho, Kari; Tuomi, Hilkka; Malehmir, Alireza; Kukkonen, Ilmo; Heikkinen, Pekka; Voipio, Teemu; Wijns, Chris

    2015-04-01

    The Kevitsa Ni-Cu-PGE disseminated sulfide deposit is hosted by the Kevitsa mafic to ultramafic intrusion located within the Central Lapland Greenstone Belt in northern Finland. The Outokumpu semi-massive to massive polymetallic (Cu-Co-Zn-Ni-Ag-Au) sulfide deposits are hosted by ophiolite-derived altered ultramafic rocks within the Raahe-Ladoga Belt in eastern Finland. Extensive, excellent quality 2D reflection seismic data have been collected at both sites in the 2000s. In addition, there is a 3D seismic data set available from Kevitsa. The ore deposits of Kevitsa and Outokumpu have different mineralization styles, grades and scales and thus have different kinds of seismic responses as well. Imaging disseminated ore deposits with the reflection seismic method is complicated, as, for example, the Kevitsa disseminated ore itself does not have dimensions detectable with the method. However, it has been suggested that subtle localised magmatic layering within the Kevitsa intrusion controls the sub-horizontal layering and spatial extent of the disseminated sulfides, and that this magmatic layering is detectable with the reflection seismic method. Initial results from data mining via SOM (Self-Organizing Maps) analysis and seismic forward modeling of the magmatic layering within the Kevitsa intrusion are used to test these hypotheses. In the case of Outokumpu-type deposits seismic forward modeling results confirm that the semi-massive to massive ore could potentially be seen directly in the seismic data, if the deposits meet the size, thickness, and presentation constraints required for reflection or diffraction.

  11. Seismic body wave separation in volcano-tectonic activity inferred by the Convolutive Independent Component Analysis

    NASA Astrophysics Data System (ADS)

    Capuano, Paolo; De Lauro, Enza; De Martino, Salvatore; Falanga, Mariarosaria; Petrosino, Simona

    2015-04-01

    One of the main challenge in volcano-seismological literature is to locate and characterize the source of volcano/tectonic seismic activity. This passes through the identification at least of the onset of the main phases, i.e. the body waves. Many efforts have been made to solve the problem of a clear separation of P and S phases both from a theoretical point of view and developing numerical algorithms suitable for specific cases (see, e.g., Küperkoch et al., 2012). Recently, a robust automatic procedure has been implemented for extracting the prominent seismic waveforms from continuously recorded signals and thus allowing for picking the main phases. The intuitive notion of maximum non-gaussianity is achieved adopting techniques which involve higher-order statistics in frequency domain., i.e, the Convolutive Independent Component Analysis (CICA). This technique is successful in the case of the blind source separation of convolutive mixtures. In seismological framework, indeed, seismic signals are thought as the convolution of a source function with path, site and the instrument response. In addition, time-delayed versions of the same source exist, due to multipath propagation typically caused by reverberations from some obstacle. In this work, we focus on the Volcano Tectonic (VT) activity at Campi Flegrei Caldera (Italy) during the 2006 ground uplift (Ciaramella et al., 2011). The activity was characterized approximately by 300 low-magnitude VT earthquakes (Md < 2; for the definition of duration magnitude, see Petrosino et al. 2008). Most of them were concentrated in distinct seismic sequences with hypocenters mainly clustered beneath the Solfatara-Accademia area, at depths ranging between 1 and 4 km b.s.l.. The obtained results show the clear separation of P and S phases: the technique not only allows the identification of the S-P time delay giving the timing of both phases but also provides the independent waveforms of the P and S phases. This is an enormous

  12. TOMO-ETNA MED-SUV.ISES an active seismic and passive seismic experiment at Mt. Etna volcano. An integrated marine and onland geophysical survey.

    NASA Astrophysics Data System (ADS)

    Ibáñez, Jesus. M.; Patane, Domenico; Puglisi, Guisseppe; Zuccarello, Lucciano; Bianco, Francesca; Luehr, Birger; Diaz-Moreno, Alejandro; Prudencio, Janire; Koulakov, Ivan; Del Pezzo, Edoardo; Cocina, Ornella; Coltelli, Mauro; Scarfi, Lucciano; De Gori, Pascuale; Carrion, Francisco

    2014-05-01

    An active seismic experiment to study the internal structure of Etna Volcano is going to carried out on Sicily and Aeolian islands. The main objective of the TOMO-ETNA MED-SUV.ISES experiment, beginning in summer 2014, is to perform a high resolution seismic tomography, in velocity and attenuation, in Southern Italy, by using active and passive seismic data, in an area encompassing outstanding volcanoes as Mt. Etna, and Aeolian volcanoes. The achievement of this objective is based on the integration and sharing of the in-situ marine and land experiments and observations and on the implementation of new instruments and monitoring systems. For the purpose, onshore and offshore seismic stations and passive and active seismic data generated both in marine and terrestrial environment will be used. Additionally, other geophysical data, mainly magnetic and gravimetric data will be considered to obtain a joint Upper Mantle-Crust structure that could permit to make progress in the understanding of the dynamic of the region. This multinational experiment which involves institutions from Spain, Italy, Germany, United Kingdom, Ireland, France, Malta, Portugal, Russia, USA and Mexico. During the experiment more than 6.600 air gun shots performed by the Spanish Oceanographic vessel "Sarmiento de Gamboa" will be recorder on a dense local seismic network consisting of 100 on land non-permanent stations, 70 on land permanent stations and 20-25 OBSs. Contemporaneously other marine geophysical measures will be performed using a marine Gravimeter LaCoste&Romberg Air-Sea Gravity System II and a Marine Magnetometer SeaSPY. The experiments will provide a unique data set in terms of data quantity and quality, and it will provide a detailed velocity and attenuation structural image of volcano edifice. The results will be essential in the development and interpretation of future volcanic models. It is noteworthy that this project is fully transversal, multidisciplinary and crosses several

  13. Spatial distribution of intrinsic and scattering seismic attenuation in active volcanic islands - II: Deception Island images

    NASA Astrophysics Data System (ADS)

    Prudencio, Janire; Ibáñez, Jesús M.; García-Yeguas, Araceli; Del Pezzo, Edoardo; Posadas, Antonio M.

    2013-12-01

    In this work, we present regional maps of the inverse intrinsic quality factor (Qi-1), the inverse scattering quality factor (Qs-1) and total inverse quality factor (Qt-1) for the volcanic environment of Deception Island (Antarctica). Our attenuation study is based on diffusion approximation, which permits us to obtain the attenuation coefficients for every single couple source-receiver separately. The data set used in this research is derived from an active seismic experiment using more than 5200 offshore shots (air guns) recorded at 32 onshore seismic stations and four ocean bottom seismometers. To arrive at a regional distribution of these values, we used a new mapping technique based on a Gaussian space probability function. This approach led us to create `2-D probabilistic maps' of values of intrinsic and scattering seismic attenuation. The 2-D tomographic images confirm the existence of a high attenuation body below an inner bay of Deception Island. This structure, previously observed in 2-D and 3-D velocity tomography of the region, is associated with a massive magma reservoir. Magnetotelluric studies reach a similar interpretation of this strong anomaly. Additionally, we observed areas with lower attenuation effects that bear correlation with consolidated structures described in other studies and associated with the crystalline basement of the area. Our calculations of the transport mean-free path and absorption length for intrinsic attenuation gave respective values of ≈ 950 m and 5 km, which are lower than the values obtained in tectonic regions or volcanic areas such as Tenerife Island. However, as observed in other volcanic regions, our results indicate that scattering effects dominate strongly over the intrinsic attenuation.

  14. Long Term Seismic Observation in Mariana by OBSs : Activity of Deep Earthquakes

    NASA Astrophysics Data System (ADS)

    Shiobara, H.; Mochizuki, K.; Ohki, S.; Kanazawa, T.; Fukao, Y.; Sugioka, H.; Suyehiro, K.

    2003-12-01

    In order to obtain the deep arc structural image of Mariana, a large-scale seismic observation by using 58 long-term ocean bottom seismometers (LTOBS) has been started since June 2003 for about one year. It is a part of the MARGINS program (US-JAPAN COLLABORATIVE RESEARCH: MULTI-SCALE SEISMIC IMAGING OF THE MARIANA SUBDUCTION FACTORY), and the aim of this observation is the crustal and mantle structure modeling by using passive and active seismic sources. The 50 and 8 LTOBSs are owned by LDEO and ERI, respectively, and they were deployed during the cruise of R/V Kaiyo (Jamstec), KY03-06. Prior to this experiment, we made a pilot long-term seismic array observation in the same area by using 10 LTOBSs, deployed in Oct. 2001 by R/V Yokosuka (Jamstec) and recovered in Feb. 2003 by R/V Kaiyo. This LTOBS has been developed by ERI, which has the PMD sensor (WB2023LP) and a titanium sphere housing (D=50cm) and was already used in several long-term observations (ex. trans-PHS array observation presented at the AGU fall meeting, 2000, S51B-02). Two of 10 LTOBSs could not be recovered due to malfunction of the releasing system, and one recovered had a trouble in the sensor control unit. But, seven others have obtained more than 11 months long data continuously. As passive source studies of these observations use characteristic deep earthquakes in this area, the activity of them will be introduced in this presentation, from the data obtained just above them. At the first step, difference of hypocenters of known events, listed on the PDE catalog, is examined. There are 59 events of epicenters within a circular area centered at 19° N, 145° E with radius of 1000km from the catalog during the observation. P and S arrivals are picked by using the WIN system, and the iasp91 model (only {VP} with {{VP}/{V_S}=1.732}) is used for the hypocenter determination. Station corrections are applied only for the sediment layer, estimated from several arrival time data of P and P-S converted

  15. Seismic evaluation of the Devonian Ohio Shale in the Big Ugly area, southwestern West Virginia

    SciTech Connect

    Zheng Li; Wilson, T. )

    1991-08-01

    The Devonian Ohio Shale was studied in the Big Ugly area of southwestern West Virginia by reprocessing and interpreting existing seismic and geologic data. These data suggest the presence of detached structures above three decollement zones and cross-strike discontinuities associated with the Alleghanian deformation west of Mann Mountain anticline. A basement growth structure, the Griffithsville basement high, localized detached structures along its southeast flank. High producing trends of gas from the Devonian Ohio Shale occur either near northwest-trending cross-strike structural discontinuities or in the northeast-trending detached structures where fracture density should be increased.

  16. Detecting Seismic Activity with a Covariance Matrix Analysis of Data Recorded on Seismic Arrays

    NASA Astrophysics Data System (ADS)

    Seydoux, L.; Shapiro, N.; de Rosny, J.; Brenguier, F.

    2014-12-01

    Modern seismic networks are recording the ground motion continuously all around the word, with very broadband and high-sensitivity sensors. The aim of our study is to apply statistical array-based approaches to processing of these records. We use the methods mainly brought from the random matrix theory in order to give a statistical description of seismic wavefields recorded at the Earth's surface. We estimate the array covariance matrix and explore the distribution of its eigenvalues that contains information about the coherency of the sources that generated the studied wavefields. With this approach, we can make distinctions between the signals generated by isolated deterministic sources and the "random" ambient noise. We design an algorithm that uses the distribution of the array covariance matrix eigenvalues to detect signals corresponding to coherent seismic events. We investigate the detection capacity of our methods at different scales and in different frequency ranges by applying it to the records of two networks: (1) the seismic monitoring network operating on the Piton de la Fournaise volcano at La Réunion island composed of 21 receivers and with an aperture of ~15 km, and (2) the transportable component of the USArray composed of ~400 receivers with ~70 km inter-station spacing.

  17. The performance of the stations of the Romanian seismic network in monitoring the local seismic activity

    NASA Astrophysics Data System (ADS)

    Ardeleanu, Luminita Angela; Neagoe, Cristian

    2014-05-01

    The seismic survey of the territory of Romania is mainly performed by the national seismic network operated by the National Institute for Earth Physics of Bucharest. After successive developments and upgrades, the network consists at present of 123 permanent stations equipped with high quality digital instruments (Kinemetrics K2, Quantera Q330, Quantera Q330HR, PS6-24 and Basalt digitizers) - 102 real time and 20 off-line stations - which cover the whole territory of the country. All permanent stations are supplied with 3 component accelerometers (episenzor type), while the real time stations are in addition provided with broadband (CMG3ESP, CMG40T, KS2000, KS54000, KS2000, CMG3T, STS2) or short period (SH-1, S13, Mark l4c, Ranger, GS21, L22_VEL) velocity sensors. Several communication systems are currently used for the real time data transmission: an analog line in UHF band, a line through GPRS (General Packet Radio Service), a dedicated line through satellite, and a dedicated line provided by the Romanian Special Telecommunication Service. During the period January 1, 2006 - June 30, 2013, 5936 shallow depth seismic events - earthquakes and quarry blasts - with local magnitude ML ≥ 1.2 were localized on the Romanian territory, or in its immediate vicinity, using the records of the national seismic network; 1467 subcrustal earthquakes (depth ≥ 60 km) with magnitude ML ≥ 1.9 were also localized in the Vrancea region, at the bend of the Eastern Carpathians. The goal of the present study is to evaluate the individual contribution of the real time seismic stations to the monitoring of the local seismicity. The performance of each station is estimated by taking into consideration the fraction of events that are localised using the station records, compared to the total number of events of the catalogue, occurred during the time of station operation. Taking into account the nonuniform space distribution of earthquakes, the location of the site and the recovery

  18. Mass transport deposits as witness of Holocene seismic activity on the Ligurian margin, Western Mediterranean (ASTARTE project)

    NASA Astrophysics Data System (ADS)

    Samalens, Kevin; Cattaneo, Antonio; Migeon, Sébastien

    2016-04-01

    The Ligurian Margin (Western Mediterranean) is at the transition between the Southern Alpes and the Liguro-Provençal margin and it is one of the most seismic areas of France. Several historic earthquakes have been indexed; the strongest, on February 23rd, 1887, occurred offshore Menton and Imperia and also caused a tsunami wave. Its equivalent magnitude has been estimated between 6 and 6.5. In addition, a moderate recurrent seismicity shakes the margin. The aim of this study is to understand the link between seismic activity and slope destabilization, and to identify the sedimentary deposits resulting from mass transport or turbidity currents. During Malisar (Geoazur laboratory), Prisme 2 and Prisme 3 (Ifremer) cruises, bathymetry, seafloor imagery (SAR), geophysics data (CHIRP SYSIF and high resolution seismics), and sediment cores have been acquired on the continental slope, focussing on canyons and submarine landslides, and in the basin. These data record numerous mass transport deposits (slump, debrites) in the different physiographic areas of the margin. To search for evidences of past Ligurian margin seismicity during the Holocene, we focused on the northeast part of the margin, the Finale area. We identified and sampled acoustically transparent Mass Transport Deposits up to 20-m thick in the bottom of three coaleshing canyons: Noli, Pora and Centa canyons from W to E in the area offshore Finale Ligure. We also recovered an MTD in the collecting deeper canyon system. MTDs in cores appear as sediment with different degrees of deformation (tilted blocks, slump, debrites) and are topped by hemipelagites. The radiocarbon age of the top of MTDs can be considered synchronous and centered around 4900 yr BP. Mass wasting occurring over more than 50 km of the Ligurian margin could indicate that an earthquake stroke the Finale area sector at that time.

  19. Chemical and biogeophysical impact of four-dimensional (4D) seismic exploration in sub-Saharan Africa, and restoration of dysfunctionalized mangrove forests in the prospect areas.

    PubMed

    Osuji, Leo C; Ayolagha, G; Obute, G C; Ohabuike, H C

    2007-09-01

    Four-dimensional (4D) seismic exploration, an improved geophysical technique for hydrocarbon-data acquisition, was applied for the first time in the Nembe Creek prospect area of Nigeria. The affected soils were slightly alkaline in situ when wet (pH 7.2), but extremely acidic when dry (pH 3.0). The organic carbon content (4.6-26.8%) and other physicochemical properties of soils and water (N, P, and heavy-metal contents, etc.) were higher than the baseline values obtained in 2001 before seismic profiling. Most values also exceeded the baseline compliance standards of the Department of Petroleum Resources (DPR), the World Health Organization (WHO), and the Federal Environmental Protection Agency (FEPA). Rehabilitation of the affected areas was achieved by stabilizing the mangrove floor by liming and appropriate application of nutrients, followed by replanting the cut seismic lines over a distance of 1,372 km with different mangrove species, including juvenile Rhizophora racemosa, R. mangle, and Avicennia species, which were transferred from nursery points. Quicker post-operational intervention is recommended for future 4D surveys, because the time lag between the end of seismic activity and post-impact investigation is critical in determining the relationship between activity and impact: the longer the intervening period, the more mooted the interaction. PMID:17886833

  20. Seismic Studies

    SciTech Connect

    R. Quittmeyer

    2006-09-25

    This technical work plan (TWP) describes the efforts to develop and confirm seismic ground motion inputs used for preclosure design and probabilistic safety 'analyses and to assess the postclosure performance of a repository at Yucca Mountain, Nevada. As part of the effort to develop seismic inputs, the TWP covers testing and analyses that provide the technical basis for inputs to the seismic ground-motion site-response model. The TWP also addresses preparation of a seismic methodology report for submission to the U.S. Nuclear Regulatory Commission (NRC). The activities discussed in this TWP are planned for fiscal years (FY) 2006 through 2008. Some of the work enhances the technical basis for previously developed seismic inputs and reduces uncertainties and conservatism used in previous analyses and modeling. These activities support the defense of a license application. Other activities provide new results that will support development of the preclosure, safety case; these results directly support and will be included in the license application. Table 1 indicates which activities support the license application and which support licensing defense. The activities are listed in Section 1.2; the methods and approaches used to implement them are discussed in more detail in Section 2.2. Technical and performance objectives of this work scope are: (1) For annual ground motion exceedance probabilities appropriate for preclosure design analyses, provide site-specific seismic design acceleration response spectra for a range of damping values; strain-compatible soil properties; peak motions, strains, and curvatures as a function of depth; and time histories (acceleration, velocity, and displacement). Provide seismic design inputs for the waste emplacement level and for surface sites. Results should be consistent with the probabilistic seismic hazard analysis (PSHA) for Yucca Mountain and reflect, as appropriate, available knowledge on the limits to extreme ground motion at

  1. Analysis of the seismic wavefield in the Moesian Platform (Bucharest area)

    NASA Astrophysics Data System (ADS)

    -Florinela Manea, Elena; Hobiger, Manuel-Thomas; Michel, Clotaire; Fäh, Donat; -Ortanza Cioflan, Carmen

    2016-04-01

    Bucharest is located in the center of the Moesian platform, in a large and deep sedimentary basin (450 km long, 300 km wide and in some places up to 20 km depth). During large earthquakes generated by the Vrancea seismic zone, located approximately 140 km to the North, the ground motion recorded in Bucharest area is characterized by predominant long periods and large amplification. This phenomenon has been explained by the influence of both source mechanism (azimuth and type of incident waves) and mechanical properties of the local structure (geological layering and geometry). The main goal of our study is to better characterize and understand the seismic wave field produced by earthquakes in the area of Bucharest. We want to identify the contribution of different seismic surface waves, such as the ones produced at the edges of the large sedimentary basin or multipath interference waves (Airy phases of Love and Rayleigh waves) to the ground motion. The data from a 35 km diameter array (URS experiment) installed by the National Institute for Earth Physics during 10 months in 2003 and 2004 in the urban area of Bucharest and adjacent zones was used. In order to perform the wave field characterization of the URS array, the MUSIQUE technique was used. This technique consists in a combination of the classical MUSIC and the quaternion-MUSIC algorithms and analyzes the three-component signals of all sensors of a seismic array together in order to analyze the Love and Rayleigh wave dispersion curves as well as the Rayleigh wave ellipticity curve. The analysis includes 20 regional earthquakes with Mw >3 and 5 teleseismic events with Mw> 7 that have enough energy at low frequency (0.1 - 1 Hz), i.e. in the resolution range of the array. For all events, the greatest energy is coming from the backazimuth of the source and the wave field is dominated by Love waves. The results of the array analyses clearly indicate a significant scattering corresponding to 2D or 3D effects in the

  2. Soft computing analysis of the possible correlation between temporal and energy release patterns in seismic activity

    NASA Astrophysics Data System (ADS)

    Konstantaras, Anthony; Katsifarakis, Emmanouil; Artzouxaltzis, Xristos; Makris, John; Vallianatos, Filippos; Varley, Martin

    2010-05-01

    This paper is a preliminary investigation of the possible correlation of temporal and energy release patterns of seismic activity involving the preparation processes of consecutive sizeable seismic events [1,2]. The background idea is that during periods of low-level seismic activity, stress processes in the crust accumulate energy at the seismogenic area whilst larger seismic events act as a decongesting mechanism releasing considerable energy [3,4]. A dynamic algorithm is being developed aiming to identify and cluster pre- and post- seismic events to the main earthquake following on research carried out by Zubkov [5] and Dobrovolsky [6,7]. This clustering technique along with energy release equations dependent on Richter's scale [8,9] allow for an estimate to be drawn regarding the amount of the energy being released by the seismic sequence. The above approach is being implemented as a monitoring tool to investigate the behaviour of the underlying energy management system by introducing this information to various neural [10,11] and soft computing models [1,12,13,14]. The incorporation of intelligent systems aims towards the detection and simulation of the possible relationship between energy release patterns and time-intervals among consecutive sizeable earthquakes [1,15]. Anticipated successful training of the imported intelligent systems may result in a real-time, on-line processing methodology [1,16] capable to dynamically approximate the time-interval between the latest and the next forthcoming sizeable seismic event by monitoring the energy release process in a specific seismogenic area. Indexing terms: pattern recognition, long-term earthquake precursors, neural networks, soft computing, earthquake occurrence intervals References [1] Konstantaras A., Vallianatos F., Varley M.R. and Makris J. P.: ‘Soft computing modelling of seismicity in the southern Hellenic arc', IEEE Geoscience and Remote Sensing Letters, vol. 5 (3), pp. 323-327, 2008 [2] Eneva M. and

  3. Soft computing analysis of the possible correlation between temporal and energy release patterns in seismic activity

    NASA Astrophysics Data System (ADS)

    Konstantaras, Anthony; Katsifarakis, Emmanouil; Artzouxaltzis, Xristos; Makris, John; Vallianatos, Filippos; Varley, Martin

    2010-05-01

    This paper is a preliminary investigation of the possible correlation of temporal and energy release patterns of seismic activity involving the preparation processes of consecutive sizeable seismic events [1,2]. The background idea is that during periods of low-level seismic activity, stress processes in the crust accumulate energy at the seismogenic area whilst larger seismic events act as a decongesting mechanism releasing considerable energy [3,4]. A dynamic algorithm is being developed aiming to identify and cluster pre- and post- seismic events to the main earthquake following on research carried out by Zubkov [5] and Dobrovolsky [6,7]. This clustering technique along with energy release equations dependent on Richter's scale [8,9] allow for an estimate to be drawn regarding the amount of the energy being released by the seismic sequence. The above approach is being implemented as a monitoring tool to investigate the behaviour of the underlying energy management system by introducing this information to various neural [10,11] and soft computing models [1,12,13,14]. The incorporation of intelligent systems aims towards the detection and simulation of the possible relationship between energy release patterns and time-intervals among consecutive sizeable earthquakes [1,15]. Anticipated successful training of the imported intelligent systems may result in a real-time, on-line processing methodology [1,16] capable to dynamically approximate the time-interval between the latest and the next forthcoming sizeable seismic event by monitoring the energy release process in a specific seismogenic area. Indexing terms: pattern recognition, long-term earthquake precursors, neural networks, soft computing, earthquake occurrence intervals References [1] Konstantaras A., Vallianatos F., Varley M.R. and Makris J. P.: ‘Soft computing modelling of seismicity in the southern Hellenic arc', IEEE Geoscience and Remote Sensing Letters, vol. 5 (3), pp. 323-327, 2008 [2] Eneva M. and

  4. Coherence between geodetic and seismic deformation in a context of slow tectonic activity (SW Alps, France)

    NASA Astrophysics Data System (ADS)

    Walpersdorf, A.; Sue, C.; Baize, S.; Cotte, N.; Bascou, P.; Beauval, C.; Collard, P.; Daniel, G.; Dyer, H.; Grasso, J.-R.; Hautecoeur, O.; Helmstetter, A.; Hok, S.; Langlais, M.; Menard, G.; Mousavi, Z.; Ponton, F.; Rizza, M.; Rolland, L.; Souami, D.; Thirard, L.; Vaudey, P.; Voisin, C.; Martinod, J.

    2015-04-01

    A dense, local network of 30 geodetic markers covering a 50 × 60 km2 area in the southwestern European Alps (Briançon region) has been temporarily surveyed in 1996, 2006 and 2011 by GPS. The aim is to measure the current deformation in this seismically active area. The study zone is characterized by a majority of extensional and dextral focal mechanisms, along north-south to N160 oriented faults. The combined analysis of the three measurement campaigns over 15 years and up to 16 years of permanent GPS data from the French RENAG network now enables to assess horizontal velocities below 1 mm/year within the local network. The long observation interval and the redundancy of the dense campaign network measurement help to constrain a significant local deformation pattern in the Briançon region, yielding an average E-W extension of 16 ± 11 nanostrain/year. We compare the geodetic deformation field to the seismic deformation rate cumulated over 37 years, and obtain good coherencies both in amplitude and direction. Moreover, the horizontal deformation localized in the Briançon region represents a major part of the Adriatic-European relative plate motion. However, the average uplift of the network in an extensional setting needs the presence of buoyancy forces in addition to plate tectonics.

  5. Seismic activity and water level fluctuations in the artificial lakes of Aliakmonas river (NW Greece)

    NASA Astrophysics Data System (ADS)

    Petrou, Panagiota; Chouliaras, Gerasimos; Drakatos, George

    2015-04-01

    The Public Power Corporation (PPC) of Greece has established four dammed reservoirs, downstream of each other on Aliakmonas River in North Western Greece (namely the artificial lakes of Ilarionas, Polyphyto, Sfikia and Asomata). In addition to the monitoring of the reservoir water levels the PPC has also installed a dense seismological network in the wider area. In this investigation the correlation between the local seismic activity and the water level fluctuations at the Ilarionas and Polyphyto reservoirs is studied. On October 25th, 1984, during the Asomata reservoir initial filling, a Ms=5.4 earthquake occurred in the region which was characterized by weak seismicity, until the strong earthquake of Ms=6.5 that occurred on May 13th, 1995, at a distance of 18 km from the southern edge of the Polyphyto reservoir. More recently, on July 2nd and 3rd, 2013, two moderate earthquakes (Ml=4.7 and Ml=4.6) occurred, almost a year after the filling of the Ilarionas reservoir in 2012. In addition to these events, fourteen earthquakes with magnitudes equal or greater to Ml=4 have also been detected in the wider area of the Aliakmonas reservoir.

  6. Seismic moment tensors and regional stress in the area of the December 2013-January 2014, Matese earthquake sequence (Italy)

    NASA Astrophysics Data System (ADS)

    D'Amico, Sebastiano; Cammarata, Laura; Cangemi, Marianna; Cavallaro, Danilo; Di Martino, Roberto Maria; Firetto Carlino, Marco

    2014-12-01

    The main goal of this study is to provide moment tensor solutions for small and moderate earthquakes of the Matese seismic sequence in southern Italy for the period of December 2013-January 2014. We estimate the focal mechanisms of 31 earthquakes with local magnitudes related to the Matese earthquake seismic sequence (December 2013-January 2014) in Southern-Central Italy which are recorded by the broadband stations of the Italian National Seismic Network and the Mediterranean Very Broadband Seismographic Network (MedNet) run by the Istituto Nazionale di Geofisica e Vulcanologia (INGV). The solutions show that normal faulting is the prevailing style of seismic deformation in agreement with the local faults mapped out in the area. Comparisons with already published solutions and with seismological and geological information available allowed us to properly interpret the moment tensor solutions in the frame of the seismic sequence evolution and also to furnish additional information about less energetic seismic phases. Focal data were inverted to obtain the seismogenic stress in the study area. The results are compatible with the major tectonic domain of the area.

  7. Seismic microzonation and velocity models of El Ejido area (SE Spain) from the diffuse-field H/V method

    NASA Astrophysics Data System (ADS)

    García-Jerez, Antonio; Seivane, Helena; Navarro, Manuel; Piña-Flores, José; Luzón, Francisco; Vidal, Francisco; Posadas, Antonio M.; Aranda, Carolina

    2016-04-01

    El Ejido town is located in the Campo de Dalías coastal plain (Almería province, SE Spain), emplaced in one of the most seismically active regions of Spain. The municipality has 84000 inhabitants and presented a high growth rate during the last twenty years. The most recent intense seismic activity occurred close to this town was in 1993 and 1994, with events of Mb = 4.9 and Mb = 5.0, respectively. To provide a basis for site-specific hazard analysis, we first carried out a seismic microzonation of this town in terms of predominant periods and geotechnical properties. The predominant periods map was obtained from ambient noise observations on a grid of 250 x 250 m in the main urban area, and sparser measurements on the outskirts. These broad-band records, of about 20 minutes long each, were analyzed by using the horizontal-to-vertical spectral ratio technique (H/V). Dispersion curves obtained from two array measurements of ambient noise and borehole data provided additional geophysical information. All the surveyed points in the town were found to have relatively long predominant periods ranging from 0.8 to 2.3 s and growing towards the SE. Secondary high-frequency (> 2Hz) peaks were found at about the 10% of the points only. On the other hand, Vs30 values of 550 - 650 m/s were estimated from the array records, corresponding to cemented sediments and medium-hard rocks. The local S-wave velocity structure has been inverted from the H/V curves for a subset of the measurement sites. We used an innovative full-wavefield method based on the diffuse-wavefield approximation (Sánchez-Sesma et al., 2011) combined with the simulated annealing algorithm. Shallow seismic velocities and deep boreholes data were used as constraints. The results show that the low-frequency resonances are related with the impedance contrast between several hundred meters of medium-hard sedimentary rocks (marls and calcarenites) with the stiffer basement of the basin, which dips to the SE. These

  8. Seismic modifications to the hot suspect repair area Argonne National Laboratory, West

    SciTech Connect

    Malik, L.E.; Harris, B.G.

    1993-10-01

    The ANL-W WIPP Waste Facility Enhancement Project required substantial remodeling and upgrades to the Hot Fuels Examination Facility (HFEF) building, including the Hot and Suspect Repair Area (HSRA). The HSRA is an enclosed single-stoned area inside the HFEF. It is separated into several compartments, some of which are used for handling radioactive materials. The HSRA roof consists of 18 GA steel Robertson Q decking with 1.5 in. concrete topping, and is utilized for storage. Braced steel frames support the HSRA roof, except at the north side, where the steel beams arc connected to the HFEF columns. The HSRA has hollow block masonry perimeter and interior walls. Seismic evaluations concluded that the HSRA did not have a competent seismic force resisting system. The structure was upgraded by decoupling it from the HFEF framing for N/S motions, modifying two existing braced frames, adding a now braced frame that can be removed temporarily during maintenance and strengthening the roof diaphragm by a unique modification consisting of special epoxy grout and steel plates installed over the existing concrete roof.

  9. Geoazur's contribution in instrumentation to monitor seismic activity of the Earth

    NASA Astrophysics Data System (ADS)

    Yates, B.; Hello, Y.; Anglade, A.; Desprez, O.; Ogé, A.; Charvis, P.; Deschamps, A.; Galve, A.; Nolet, G.; Sukhovich, A.

    2011-12-01

    Seismic activity in the earth is mainly located near the tectonic plate boundaries, in the deep ocean (expansion centers) or near their margins (subduction zones). Travel times and waveforms of recorded seismograms can be used to reconstruct the three-dimensional wave speed distribution in the earth with seismic tomography or to image specific boundaries in the deep earth. Because of the lack of permanent sea-bottom seismometers these observation are conducted over short period of time using portable ocean bottom seismometers. Geaozur has a long experience and strong skills in designing and deploying Ocean Bottom Seismometers all over the world. We have developed two types of ocean bottom instruments. The "Hippocampe" for long deployment and "Lady bug" for aftershock monitoring or for fast overlaps during wide angle experiments. Early warning systems for tsunamis and earthquakes have been developed in recent years but these need real time data transmission and direct control of the instrument. We have developed a permanent real time Broad Band instrument installed in the Mediterranean Sea and connected to the Antares Neutrinos telescope. This instrument offers all the advantages of a very heavy and costly installation, such as the ability to do real-time seismology on the seafloor. Such real-time seafloor monitoring is especially important for seismic hazard. Major earthquakes cause human and economic losses directly related to the strong motion of the ground or by induced phenomena such as tsunamis and landslides. Fiber optical cables provide a high-capacity lightweight alternative to traditional copper cables. Three-component sensors analyze permanently the noise signal and detect the events to record. Major events can force the network to transmit data with almost zero lag time. The optical link also allows us to retrieve events at a later date. However, OBSs alone can never provide the density and long term, homogeneous data coverage needed for local and global

  10. Three-dimensional seismic velocity structure of the San Francisco Bay area

    NASA Astrophysics Data System (ADS)

    Hole, J. A.; Brocher, T. M.; Klemperer, S. L.; Parsons, T.; Benz, H. M.; Furlong, K. P.

    2000-06-01

    Seismic travel times from the northern California earthquake catalogue and from the 1991 Bay Area Seismic Imaging Experiment (BASIX) refraction survey were used to obtain a three-dimensional model of the seismic velocity structure of the San Francisco Bay area. Nonlinear tomography was used to simultaneously invert for both velocity and hypocenters. The new hypocenter inversion algorithm uses finite difference travel times and is an extension of an existing velocity tomography algorithm. Numerous inversions were performed with different parameters to test the reliability of the resulting velocity model. Most hypocenters were relocated <2 km from their catalogue locations. Large lateral velocity variations at shallow (<4 km) depth correlate with known surface geology, including low-velocity Cenozoic sedimentary basins, high-velocity Cenozoic volcanic rocks, and outcrop patterns of the major Mesozoic geologic terranes. Salinian arc rocks have higher velocities than the Franciscan melange, which in turn are faster than Great Valley Sequence forearc rocks. The thickess of low-velocity sediment is defined, including >12 km under the Sacramento River Delta, 6 km beneath Livermore Valley, 5 km beneath the Santa Clara Valley, and 4 km beneath eastern San Pablo Bay. The Great Valley Sequence east of San Francisco Bay is 4-6 km thick. A relatively high velocity body exists in the upper 10 km beneath the Sonoma volcanic field, but no evidence for a large intrusion or magma chamber exists in the crust under The Geysers or the Clear Lake volcanic center. Lateral velocity contrasts indicate that the major strike-slip faults extend sub vertically beneath their surface locations through most of the crust. Strong lateral velocity contrasts of 0.3-0.6 km/s are observed across the San Andreas Fault in the middle crust and across the Hayward, Rogers Creek, Calaveras, and Greenville Faults at shallow depth. Weaker velocity contrasts (0.1-0.3 km/s) exist across the San Andreas, Hayward

  11. Three-dimensional seismic velocity structure of the San Francisco Bay area

    USGS Publications Warehouse

    Hole, J.A.; Brocher, T.M.; Klemperer, S.L.; Parsons, T.; Benz, H.M.; Furlong, K.P.

    2000-01-01

    Seismic travel times from the northern California earthquake catalogue and from the 1991 Bay Area Seismic Imaging Experiment (BASIX) refraction survey were used to obtain a three-dimensional model of the seismic velocity structure of the San Francisco Bay area. Nonlinear tomography was used to simultaneously invert for both velocity and hypocenters. The new hypocenter inversion algorithm uses finite difference travel times and is an extension of an existing velocity tomography algorithm. Numerous inversions were performed with different parameters to test the reliability of the resulting velocity model. Most hypocenters were relocated 12 km under the Sacramento River Delta, 6 km beneath Livermore Valley, 5 km beneath the Santa Clara Valley, and 4 km beneath eastern San Pablo Bay. The Great Valley Sequence east of San Francisco Bay is 4-6 km thick. A relatively high velocity body exists in the upper 10 km beneath the Sonoma volcanic field, but no evidence for a large intrusion or magma chamber exists in the crust under The Geysers or the Clear Lake volcanic center. Lateral velocity contrasts indicate that the major strike-slip faults extend subvertically beneath their surface locations through most of the crust. Strong lateral velocity contrasts of 0.3-0.6 km/s are observed across the San Andreas Fault in the middle crust and across the Hayward, Rogers Creek, Calaveras, and Greenville Faults at shallow depth. Weaker velocity contrasts (0.1-0.3 km/s) exist across the San Andreas, Hayward, and Rogers Creek Faults at all other depths. Low spatial resolution evidence in the lower crust suggests that the top of high-velocity mafic rocks gets deeper from west to east and may be offset under the major faults. The data suggest that the major strike-slip faults extend subvertically through the middle and perhaps the lower crust and juxtapose differing lithology due to accumulated strike-slip motion. The extent and physical properties of the major geologic units as

  12. LAND STREAMER SEISMIC DATA FROM NORTHERN DELAWARE: A VIABLE ALTERNATIVE FOR IMAGING AQUIFERS IN SUBURBAN AREAS

    NASA Astrophysics Data System (ADS)

    Velez, C. C.; McLaughlin, P. P.; McGeary, S. E.; Sargent, S. L.

    2009-12-01

    The Potomac Formation includes the most important confined aquifers in the Coastal Plain of northern Delaware. Development and a growing suburban population are increasing demand for groundwater in the area, making accurate assessment of groundwater water supply increasingly important. Previous studies of subsurface geology indicate that the Potomac Formation is characterized by laterally discontinuous fluvial sand bodies, making it difficult to precisely delineate the distribution and geometry of the aquifer facies based on well correlations alone. A 20-km high-resolution seismic reflection dataset was collected using a land-streamer system in 2008 to constrain subsurface stratigraphy between disparate well locations. The data were collected along roadways in an area of mixed development that includes suburban housing tracts, farmlands, and large industry. A 152-m-deep continuous-cored test hole was drilled in the summer of 2009 adjacent to one of the lines and a full suite of borehole geophysical logs obtained. The land-streamer data are compared to a 3-km dataset collected also in 2008 using conventional methods on farmland in the northern part of the study area. The land streamer system proved to be more effective than conventional seismic reflection methods in this area. Several advantages are evident for the land streamer: 1) overall, the conventional dataset has a higher S/N, 2) on average, collecting data with the land streamer system is four times faster, and 3) the land streamer lines can be longer and therefore more continuous than the conventional lines in a developed area. The land-streamer system has minor disadvantages: traffic control, traffic noise, and in some cases a need for larger crews. Regardless, the land streamer dataset is easier to process, of higher quality, and more cost effective. The final depth images from the land streamer data indicate that the minimum and maximum depths imaged are ~18 m and ~ 268m, with a resolution of ~4 m. This

  13. Structural design of active seismic isolation floor with a charging function

    NASA Astrophysics Data System (ADS)

    Nakakoji, Hayato; Miura, Nanako

    2016-04-01

    This study shows an optimum structure of a seismic isolation floor against horizontal ground motions. Although a seismic isolation floor is effective with vibration reduction, the response of the floor becomes larger when excited by long-period ground motions. It is shown that caster equipment move and suffer damage in a seismic isolation structure by an experiment. Moreover, the permissible displacement of the floor is limited. Therefore, the focus is on an active seismic isolation. About active control, the system cannot operate without power supply. To solve these problems an energy regeneration is considered in our previous study. These studies only analyze simple model and did not choose the suitable structure for active control and energy regeneration. This research propose a new structure which has regenerated energy exceeds the energy required for the active control by numerical simulation.

  14. Depositional history and seismic stratigraphy of Lower Cretaceous rocks in the National Petroleum Reserve in Alaska and adjacent areas

    SciTech Connect

    Molenaar, C.M.

    1989-01-01

    Lower Cretaceous rocks, which are widespread throughout the National Petroleum Reserve in Alaska (NPRA) and adjacent areas north of the Brooks Range, make up the major part of the thick sedimentary fill of the Colville basin. Much seismic and well information obtained since 1974 has aided considerably in understanding these rocks. These data include about 20,000 km of seismic lines, covering much of the NPRA with a grid spacing of 10-20 km, and 28 exploratory wells that bring the total to more than 50 wells in and adjacent to the NPRA. The purpose of this chapter is to interpret the depositional history of Lower Cretaceous rocks in the NPRA and adjacent areas on the basis of the latest seismic and well data and well data and on information from outcrops in the southern part of the Colville basin. The basin geometry and depositional history described in earlier reports are repeated here in the context of the overall Lower Cretaceous depositional history. Well data (including paleontology) and seismic data are used almost exclusively to interpret relations in the northern foothills and coastal plain areas. Surface data and some well data are used in the southern parts of the northern foothills, and surface data are used exclusively to interpret the depositional history in the southern foothills and Brooks Range. The quality of seismic data is fair to good in most of the coastal plain, where the structure is simple. In the northern foothills, tracing seismic reflections is more difficult, especially in the shallower part of the section because of structural complications in the thrust-faulted anticlines. The quality of seismic data across the structurally complex southern foothills area is inadequate to correlate stratigraphic units of the outcrop area of the southern foothills with subsurface units to the north.

  15. Time Variation of Seismic Anisotropy, Stress and Cracks on Active Volcanoes (Invited)

    NASA Astrophysics Data System (ADS)

    Savage, M. K.

    2013-12-01

    We summarize measurements of seismic anisotropy and its relation to other geophysical measurements of stress and cracks on eleven active volcanoes; Unzen (Unz), Sakurajima (Sak), Aso, Asama (Asm) and Kirishima (Kir) in Japan; Okmok (Okm) in Alaska, Ruapehu (Rua) and Tongariro (Ton) in New Zealand, Soufriere Hills (Sou) in Montserrat, Kilauea (Kil) in Hawaii and Piton de la Fournaise (PdF) in La Reunion. We used the MFAST shear wave splitting computer code, an objective code that is fully automatic except for the S arrival pick. Fast polarization directions (phi) should be parallel to cracks and hence the maximum horizontal stress direction. Time delays (dt) increase with path length and percent anisotropy, usually related to crack density. Where possible we used S waves from deep earthquakes to ensure that the movement of the earthquakes was not correlated with the volcanic activity. At some volcanoes we used families of repeating events with similar waveforms and at most volcanoes we also computed splitting at earthquakes local to the volcano. We compared the phi and dt variation in time to eruption occurrences and to other available parameters including seismicity rate, b-values, focal mechanisms, isotropic velocity changes from noise cross-correlation, Vp/Vs ratios, Geodetic measurements such as GPS and tilt, and gas flux. All volcanoes had some stations with excellent shear wave arrivals that yielded measureable splitting. Individual measurements showed scatter in most areas, but at most of the volcanoes, moving averages of phi or dt (or both) yielded time variations that correlated with other measurements related to volcanic activity or to stress changes or changes in crack-filling material such as gas flux. The multiplet studies did not yield slowly varying splitting but instead showed distinct jumps in splitting parameters at various times, which appears to be caused in part by cycle skipping. Time resolution of changes depends on the seismicity available

  16. Seismic high attenuation area beneath the 2008 Iwate-Miyagi Nairiku earthquake (M7.2) and Mt. Chokai in NE Japan

    NASA Astrophysics Data System (ADS)

    Shikasho, K.; Okada, T.; Nakajima, J.; Hayami, E.; Uchida, N.; Matsuzawa, T.; Umino, N.; Hasegawa, A.

    2011-12-01

    volcanic front of NE Japan. This anomaly seems to connect the high attenuation area just below the volcanoes of the focal area. This distribution beneath Mt. Chokai corresponds with the distribution of the seismic low velocity zone (Okada et al., 2010). The seismicity is active around the boundary with the low-Qs and high-Qs and/or in high-Qs anomaly. The low-frequency earthquakes are distributed in the edge of the high attenuation area in the lower crust below the volcanoes.

  17. Shallow water seismic surveys for site investigation in the Haifa Port Extension area, Israel

    NASA Astrophysics Data System (ADS)

    Shtivelman, Vladimir

    2001-02-01

    A shallow water seismic study was recently carried out as a part of a site investigation project in the Haifa Port Extension area near the Mediterranean coast of Israel. The objectives of the study were estimating P- and S-wave velocity distribution below the seabed and detecting recent faulting at the site. An additional target was testing the presence of a hard rock with P-wave velocity of more than 3000 m/s within the depth range down to 700 m. To achieve the objectives, specially designed refraction and high resolution reflection surveys were carried out at the site. The data acquisition was performed using bay cables and hydrophones placed at the seabed. The source of seismic energy was a single air gun for the reflection survey and explosives for the refraction survey. The P-wave velocities estimated from the shallow refraction data vary in a narrow range of 1800-2200 m/s, hampering the depth interpretation of the data. No indication of the presence of a high-velocity (hard rock) layer within the depth range of 700 m was found. The S-wave velocities were estimated on the basis of the dispersion analysis of Scholte waves contained in the refraction records. The resulting S-wave velocity distribution correlates well with the result of the land refraction survey carried out in the vicinity of the investigated site. The reflection time sections display a sequence of reflections from various stratigraphic units down to the depths of about 800 m. Although some evidence of deformation may be found in the deep part of the sections, there is no indication of the existence of faults in the shallow part of the sections (upper 250-300 m). The results of the surveys show that acquiring shallow water seismic data at the sea bottom may be a relatively simple and effective way to derive information regarding the structure and properties of the shallow subsurface below the seabed.

  18. Seismic Activity at Vailulu'u, Samoa's Youngest Volcano

    NASA Astrophysics Data System (ADS)

    Konter, J.; Staudigel, H.; Hart, S.

    2002-12-01

    Submarine volcanic systems, as a product of the Earth's mantle, play an essential role in the Earth's heat budget and in the interaction between the solid Earth and the hydrosphere and biosphere. Their eruptive and intrusive activity exerts an important control on these hydrothermal systems. In March 2000, we deployed an array of five ocean bottom hydrophones (OBH) on the summit region (625-995 m water depth) of Vailulu'u Volcano (14°12.9'S;169°03.5'W); this volcano represents the active end of the Samoan hotspot chain and is one of only a few well-studied intra-plate submarine volcanoes. We monitored seismic activity for up to 12 months at low sample rate (25 Hz), and for shorter times at a higher sample rate (125 Hz). We have begun to catalogue and locate a variety of acoustic events from this network. Ambient ocean noise was filtered out by a 4th-order Butterworth bandpass filter (2.3 - 10 Hz). We distinguish small local earthquakes from teleseismic activity, mostly identified by T- (acoustic) waves, by comparison with a nearby GSN station (AFI). Most of the detected events are T-phases from teleseismic earthquakes, characterized by their emergent coda and high frequency content (up to 30 Hz); the latter distinguishes them from low frequency emergent signals associated with the volcano (e.g. tremor). A second type of event is characterized by impulsive arrivals, with coda lasting a few seconds. The differences in arrival times between stations on the volcano are too small for these events to be T-waves; they are very likely to be local events, since the GSN station in Western Samoa (AFI) shows no arrivals close in time to these events. Preliminary locations show that these small events occur approximately once per day and are located within the volcano (the 95% confidence ellipse is similar to the size of the volcano, due to the small size of the OBH network). Several events are located relatively close to each other (within a km radius) just NW of the crater.

  19. 3D Seismic Velocity Structure in the Rupture Area of the 2010 Maule Mw=8.8 Earthquake

    NASA Astrophysics Data System (ADS)

    Hicks, S. P.; Rietbrock, A.; Ryder, I. M.; Nippress, S.; Haberland, C. A.

    2011-12-01

    The 2010 Mw=8.8 Maule, Chile earthquake is one of the largest subduction zone earthquakes ever recorded. Up to now numerous co-seismic and some post-seismic slip models have been published based entirely on seismological, geodetic, or tsunami run-up heights, or combinations of these data. Most of these models use a simplified megathrust geometry derived mainly from global earthquake catalogues, and also simplified models of seismic parameters (e.g. shear modulus). By using arrival times for a vast number of aftershocks that have been recorded on a temporary seismic array, we present a new model for the slab geometry based on earthquake locations together with a new 3D seismic velocity model of the region, for both vp and vp/vs. We analyzed 3552 aftershocks that occurred between 18 March and 24 May 2011, recorded by the International Maule Aftershock Dataset (IMAD) seismic network. Event selection from a catalogue of automatically-determined events was based on 20 or more arrival times, from which at least 10 are S-wave observations. In total over 170,000 arrival times (~125,000 and 45,000 P and S wave arrival times respectively) are used for the tomographic reconstructions. Initially, events were relocated in a 2D velocity model based on a previously published model for the southern end of the rupture area (Haberland et al., 2009). Afterwards a staggered inversion scheme is implemented, starting with a 2D inversion followed by a coarse 3D and a subsequent fine 3D inversion. Based on our preliminary inversions we conclude that aftershock seismicity is mainly concentrated between 20 and 35 km depth along the subduction interface. A second band of seismicity between 40 and 50 km depth is also observed. Low seismic velocities and an increased vp/vs ratio characterize the marine forearc. The obtained velocity model will be discussed.

  20. Geodetic Constraints on Fault Slip Rates and Seismic Hazard in the Greater Las Vegas Area

    NASA Astrophysics Data System (ADS)

    Hammond, W. C.; Kreemer, C.; Blewitt, G.; Broermann, J.; Bennett, R. A.

    2014-12-01

    We address fundamental questions about how contemporary tectonic deformation of the crust in the southern Great Basin occurs in the region around Las Vegas (LV) Nevada, western Arizona and eastern California. This area lies in the intersection of the eastern Walker Lane Belt, southern Great Basin and western Colorado Plateau (CP), sharing features of transtensional and extensional deformation associated with Pacific/North America relative motion. We use GPS data collected from 48 stations of the MAGNET semi-continuous network and 77 stations from continuous networks including BARGEN and EarthScope Plate Boundary Observatory. MAGNET stations have been observed for a minimum of 7 years, while most continuous stations have longer records. From these data we estimate the velocity of crustal motion for all stations with respect to the stable North America reference frame NA12. To correct for transients from recent large earthquakes including the 1999 Hector Mine and 2010 El Mayor-Cucapah events we use models of co- and post-seismic deformation, subtracting the predicted motions from the time series before estimating interseismic stain rates. We find approximately 2 mm/yr of relative motion distributed over 200 km centered on Las Vegas, with a mean strain accumulation rate of 10 × 10-9 yr-1, with lower rates of predominantly extensional strain to the east and higher rates of predominantly shear deformation to the west. The mean strain rate is lower than that of the western Walker Lane but about twice that of eastern Nevada where e.g., the Wells, NV MW 6.0 earthquake occurred in 2008. From this new velocity field we generated a horizontal tensor strain rate map and a crustal block motion model to portray the transition of active strain from the CP into the Walker Lane. For faults in the Las Vegas Valley, including the Eglington Fault and Frenchman Mountain Fault, the observed velocity gradients and model results are consistent with normal slip rates of 0.2 mm/yr, which

  1. Seismic hazard in the Istanbul metropolitan area: A preliminary re-evaluation

    USGS Publications Warehouse

    Kalkan, E.; Gulkan, Polat; Ozturk, N.Y.; Celebi, M.

    2008-01-01

    In 1999, two destructive earthquakes (M7.4 Kocaeli and M7.2 Duzce) occurred in the north west of Turkey and resulted in major stress-drops on the western segment of the North Anatolian Fault system where it continues under the Marmara Sea. These undersea fault segments were recently explored using bathymetric and reflection surveys. These recent findings helped to reshape the seismotectonic environment of the Marmara basin, which is a perplexing tectonic domain. Based on collected new information, seismic hazard of the Marmara region, particularly Istanbul Metropolitan Area and its vicinity, were re-examined using a probabilistic approach. Two seismic source and alternate recurrence models combined with various indigenous and foreign attenuation relationships were adapted within a logic tree formulation to quantify and project the regional exposure on a set of hazard maps. The hazard maps show the peak horizontal ground acceleration and spectral acceleration at 1.0 s. These acceleration levels were computed for 2 and 10 % probabilities of transcendence in 50 years.

  2. High resolution seismic imaging of an active normal fault in the Agri Valley, Southern Apennines, Italy

    NASA Astrophysics Data System (ADS)

    Improta, L.; Bruno, P.; di Fiore, V.; Mariani, S.

    2004-12-01

    The Agri Valley is an intermontane basin located in the Southern Apennine seismic belt (Italy) whose formation in tied to large NW-trending trastensional and extensional faults active since Early Pleistocene. Recent faulting activity in the area is documented by faulted paleosoils and suggested by a M7 earthquake that struck the basin in 1857. On the contrary, present-day background seismicity in the area is extremely low. Despite intense geomorphic investigations, the identification of the source responsible for this historical event and of further large seismogenic faults in the area is still a matter of debate. A new NW trending normal faulting system has been recently recognized based on subtle geomorphic expressions on the ridge bounding the basin westward. Recent faulting activity along this structure is locally documented by a trench. Aimed at yielding new information about the shallow structure of the fault, we conducted a high resolution seismic experiment in a small lacustrine basin, located 4 km south of the trench, in which the presence of the fault is inferred by a linear surface warping but trench excavation is impractical. Both multi-fold wide-angle data and multichannel near vertical reflection data have been collected along a 220-m-long profile in order to obtain an accurate model of the basin combining seismic velocity and reflectivity images. About 3600 first arrival traveltimes picked on 36 wide-angle record sections have been inverted by a non-linear tomographic technique that is specially designed to image complex structures. The tomographic inversion provides a high-resolution velocity model of the basin down to 60 m depth. The model is strongly heterogeneous and displays sharp lateral velocity variations. Seismic reflection processing has been applied to both data sets. Data have been edited for trace quality and first (refracted and direct) arrivals have been muted. A following FK dip filtering on the shot gathers reduced the energy

  3. FM&TI (Forward Modeling & Tomographic Inversion) approach in passive and active seismic studies

    NASA Astrophysics Data System (ADS)

    Koulakov, Ivan

    2010-05-01

    Seismic tomography is like a photography taken by a camera with deformed and blurred lenses. Amplitudes and shapes of seismic patterns derived at tomographic images are often strongly biased with respect to real structures in the Earth. In particular, tomography usually provides continuous velocity distributions, while the major velocity changes in the Earth often occur on first order interfaces. While working with noisy data, one has to apply strong damping which makes impossible retrieving realistic amplitudes of anomalies. Uneven ray sampling may cause variable damping effect: within one model, one may obtain over- and underdamped solutions in different parts of the study area. Lack of some ray orientations may cause smearing of seismic patterns. Due to these and other reasons, quantitative values reported in most tomographic studies, although supported by pseudo-formal criteria (e.g. trade-off curves), do not often represent the reality. We propose an approach which is used to construct a realistic structure of the Earth based on a combination of forward modeling and tomographic inversion. Based on available a-priori information we construct a synthetic model with realistic patterns. Then we compute synthetic times and invert them using the same tomographic code with the same parameters as in the case of observed data processing. The reconstruction result is compared with the tomographic image of observed data inversion. For the parts where discrepancy is observed, we correct the synthetic model and repeat the forward modeling and inversion again. After several trials we obtain similar results of synthetic and observed data inversion. In this case we claim that the derived synthetic model adequately represents the real structure of the Earth. In the talk, several examples of applying this approach at various scales for different data schemes are presented: (1) few real and synthetic examples of active source refraction travel time data; (2) local earthquake

  4. Wisconsinan-Holocene seismic stratigraphy of the Keathley Canyon Area and vicinity, northwestern Gulf of Mexico

    SciTech Connect

    Lee, Gwang Hoon; Bryant, W.R.; Watkins, J.S. )

    1991-03-01

    The lower continental slope of the northwestern Gulf of Mexico is characterized by a hummocky topography with shallow salt masses interspersed by numerous salt-withdrawal basins containing thick Plio-Pleistocene and older sediments. Analysis of over 7500 km of multichannel seismic reflection data from the Keathley Canyon Area and vicinity defined the Wisconsinan-Holocene sequence and its seismic facies. In interbasinal areas and in the southern part of the study area where salt is shallow, the Wisconsinan-Holocene sequence consists mainly of low-amplitude (LA) facies underlain by strong basal-reflection (SBR) facies. The LA facies occasionally show subtle onlaps against SBR facies and grade upward into a draping pattern. Onlapping LA facies are interpreted to be a lowstand systems tract deposited by widespread low-energy turbidity currents. Draping LA facies at the top may consist of hemipelagic or pelagic sediments. The SBR facies are interpreted to consist of condensed sections formed during sea-level rises and highstands. Within basins, moderate-to-high amplitude-continuous (MHC) and hummocky-to-chaotic (HC) facies occur below LA facies. The MHC facies show a pattern of flat-lying or gently dipping reflections that onlap SBR facies. Onlapping MHC facies often grade upward into a conformable pattern and are obscured by transition into LA facies. The MHC facies are interpreted as alternating coarse- and fine-grained turbidites deposited during sea-level falls and/or lowstands. The HC facies occur commonly associated with MHC facies. The HC facies may represent slope fans formed by mass-transport processes or gravity flows during sea-level falls and/or lowstands.

  5. Trace Gases - A Warning Signs of Impending Major Seismic Activity

    NASA Astrophysics Data System (ADS)

    Baijnath, J.; Freund, F.; Li, J.

    2013-12-01

    Seismological models can predict future earthquakes only with wide uncertainty windows, typically on the order of decades to centuries. To improve short-term earthquake forecasts, it is essential to understand the non-seismic processes that take place in Earth's crust during the build-up of tectonic stresses. Days prior to the January 2001 M 7.6 Gujurat earthquake in India, there was a significant increase in the regional CO concentration, reaching 240 ppbv over a 100 squared kilometers, as derived from data of the MOPITT sensor onboard the NASA Terra satellite. A possible explanation for these observations is that when stresses in Earth's crust are building, positive hole charge carriers are activated, which are highly mobile and spread from deep below the earth to the surface. Positive holes act as highly oxidizing oxygen radicals, oxidizing water to hydrogen peroxide. It is hypothesized that, as positive hole charge carriers arrive from below and traverse the soil, they are expected to oxidize soil organics, converting aliphatics to ketones, formaldehyde, CO and CO2. This is tested by using a closed chamber with a slab of gabbro rock. Ultrasound generated by a pair of 50 W, 40 kHz piezoelectric transducers, applied to one end of the gabbro slab was used to activate the positive holes. This created a high concentration of positive holes at the end of the rock that the electrical conductivity through the rock increased more than 1000-fold, while the increase in conductivity through the other end of the gabbro slab was on the order of 100-fold. On the other end of the slab, rock dust and various soils were placed. A stainless steel mesh was also placed over the soil and dust to allow a current to flow through the granular material. When the far end of the slab was subjected to the ultrasound, currents as large as 250 nA were recorded flowing through the length of the gabbro slab and through the dust/soil pile. Dry dust/soil and dust samples impregnated with

  6. Seismicity on the area of the Waste Isolation Pilot Plant (WIPP)

    SciTech Connect

    Sanford, A.; Sanford, S.; Wallace, T.; Barrows, L.; Sheldon, J.; Ward, R.; Johansen, S.; Merritt, L.

    1980-05-01

    Since April 1974, New Mexico Institute of Mining and Technology (NMIMT) has operated a short-period vertical-component seismograph 7 km from the center of the WIPP site. Peak magnifications ranged from 405 K to 1400 K. In the time period from April 1974 to February 1979, approximately 500 earthquakes were recorded by the instrument to distances as great as 660 km. With the aid of readings from stations operated by other organizations, epicenters and magnitudes for 159 earthquakes within about 300 km of the WIPP site were obtained. The greatest concentration of seismic activity is centered on the Central Basin Platform. This zone of activity, approximately 120 km in a NS direction and 100 km in an EW direction, approaches to within 60 km of the site. Other significant clusters of earthquakes occur near Synder, Big Springs and Valentine, Texas. Comparable levels of earthquake activity are observed within 100, 200, and 300 km of the site. Most reported Quaternary faulting lies to the west of 104.3/sup 0/W longitude. Comparable levels of activity were observed to the east and west of this longitude indicating the observed distribution of earthquake activity is probably not representative of the long-term (500,000 years) seismicity of the region. Several lines of evidence suggest that most earthquakes from the Delaware Basin eastward are induced by the production of hydrocarbons, but absolutely convincing proof is lacking. If due to natural tectonic forces, an extrapolation of the observed earthquake-frequency relation indicates an earthquake of magnitude 5 1/2 is possible somewhere within 300 km of the site each 100 years.

  7. Multi-level continuous active source seismic monitoring (ML-CASSM): Application to shallow hydrofracture monitoring

    NASA Astrophysics Data System (ADS)

    Ajo Franklin, J. B.; Daley, T. M.; Butler-Veytia, B.; Peterson, J.; Gasperikova, E.; Hubbard, S. S.

    2010-12-01

    Induced subsurface processes occur over a wide variety of time scales ranging from seconds (e.g. fracture initiation) to days (e.g. unsteady multiphase flow) and weeks (e.g. induced mineral precipitation). Active source seismic monitoring has the potential to dynamically characterize such alterations and allow estimation of spatially localized rates. However, even optimal timelapse seismic surveys have limited temporal resolution due to both the time required to acquire a survey and the cost of continuous field deployment of instruments and personnel. Traditional timelapse surveys are also limited by experimental repeatability due to a variety of factors including geometry replication and near-surface conditions. Recent research has demonstrated the value of semi-permanently deployed seismic systems with fixed sources and receivers for use in monitoring a variety of processes including near-surface stress changes (Silver et.al. 2007), subsurface movement of supercritical CO2 (Daley et.al. 2007), and preseismic velocity changes in fault regions (Niu et. al. 2008). This strategy, referred to as continuous active source seismic monitoring (CASSM), allows both precise quantification of traveltime changes on the order of 1.1 x 10-7 s and temporal sampling on the order of minutes. However, as previously deployed, CASSM often sacrifices spatial resolution for temporal resolution with previous experiments including only a single source level. We present results from the first deployment of CASSM with a large number of source levels under automated control. Our system is capable of autonomously acquiring full tomographic datasets (10 sources, 72 receivers) in 3 minutes without human intervention, thus allowing active source seismic imaging (rather than monitoring) of processes with short durations. Because no sources or receivers are moved in the acquisition process, signal repeatability is excellent and subtle waveform changes can be interpreted with increased confidence

  8. Active Fault Characterization in the Urban Area of Vienna

    NASA Astrophysics Data System (ADS)

    Decker, Kurt; Grupe, Sabine; Hintersberger, Esther

    2016-04-01

    The identification of active faults that lie beneath a city is of key importance for seismic hazard assessment. Fault mapping and characterization in built-up areas with strong anthropogenic overprint is, however, a challenging task. Our study of Quaternary faults in the city of Vienna starts from the re-assessment of a borehole database of the municipality containing several tens of thousands of shallow boreholes. Data provide tight constraints on the geometry of Quaternary deposits and highlight several locations with fault-delimited Middle to Late Pleistocene terrace sediments of the Danube River. Additional information is obtained from geological descriptions of historical outcrops which partly date back to about 1900. The latter were found to be particularly valuable by providing unprejudiced descriptions of Quaternary faults, sometimes with stunning detail. The along-strike continuations of some of the identified faults are further imaged by industrial 2D/3D seismic acquired outside the city limits. The interpretation and the assessment of faults identified within the city benefit from a very well constrained tectonic model of the active Vienna Basin fault system which derived from data obtained outside the city limits. This data suggests that the urban faults are part of a system of normal faults compensating fault-normal extension at a releasing bend of the sinistral Vienna Basin Transfer Fault. Slip rates estimated for the faults in the city are in the range of several hundredths of millimetres per year and match the slip rates of normal faults that were trenched outside the city. The lengths/areas of individual faults estimated from maps and seismic reach up to almost 700 km² suggesting that all of the identified faults are capable of producing earthquakes with magnitudes M>6, some with magnitudes up to M~6.7.

  9. Revision of the geological context of the Port-au-Prince metropolitan area, Haiti: implications for slope failures and seismic hazard assessment

    NASA Astrophysics Data System (ADS)

    Terrier, M.; Bialkowski, A.; Nachbaur, A.; Prépetit, C.; Joseph, Y. F.

    2014-09-01

    Following the earthquake of 12 January 2010 in the Port-au-Prince area, the Haitian government, in close cooperation with BRGM, the French geological Survey, decided to undertake a seismic microzonation study of the metropolitan area of the capital in order to take more fully into account the seismic risk in the urbanization and planning of the city under reconstruction. As the first step of the microzonation project, a geological study has been carried out. Deposits of Miocene and Pliocene formations in a marine environment have been identified. These deposits are affected by the Enriquillo-Plantain Garden N80° E fault system and N110° E faults. Tectonic observations and morphological analysis indicate Quaternary activity of several faults mapped in the area of Port-au-Prince. These faults have a N110° trend and show a reverse-sinistral strike-slip motion. Moreover, on the basis of these geological results and of new topographical data, a hazard assessment of ground movements has been made. Along with the map of active faults, the hazard map of ground movements is an integral component of the seismic microzonation study.

  10. Dating previously balanced rocks in seismically active parts of California and Nevada

    USGS Publications Warehouse

    Bell, J.W.; Brune, J.N.; Liu, T.; Zreda, M.; Yount, J.C.

    1998-01-01

    Precariously balanced boulders that could be knocked down by strong earthquake ground motion are found in some seismically active areas of southern California and Nevada. In this study we used two independent surface-exposure dating techniques - rock-varnish microlamination and cosmogenic 36Cl dating methodologies - to estimate minimum- and maximum-limiting ages, respectively, of the precarious boulders and by inference the elapsed time since the sites were shaken down. The results of the exposure dating indicate that all of the precarious rocks are >10.5 ka and that some may be significantly older. At Victorville and Jacumba, California, these results show that the precarious rocks have not been knocked down for at least 10.5 k.y., a conclusion in apparent conflict with some commonly used probabilistic seismic hazard maps. At Yucca Mountain, Nevada, the ages of the precarious rocks are >10.5 to >27.0 ka, providing an independent measure of the minimum time elapsed since faulting occurred on the Solitario Canyon fault.

  11. On dependence of seismic activity on 11 year variations in solar activity and/or cosmic rays

    NASA Astrophysics Data System (ADS)

    Zhantayev, Zhumabek; Khachikyan, Galina; Breusov, Nikolay

    2014-05-01

    It is found in the last decades that seismic activity of the Earth has a tendency to increase with decreasing solar activity (increasing cosmic rays). A good example of this effect may be the growing number of catastrophic earthquakes in the recent rather long solar minimum. Such results support idea on existence a solar-lithosphere relationship which, no doubts, is a part of total pattern of solar-terrestrial relationships. The physical mechanism of solar-terrestrial relationships is not developed yet. It is believed at present that one of the main contenders for such mechanism may be the global electric circuit (GEC) - vertical current loops, piercing and electrodynamically coupling all geospheres. It is also believed, that the upper boundary of the GEC is located at the magnetopause, where magnetic field of the solar wind reconnects with the geomagnetic field, that results in penetrating solar wind energy into the earth's environment. The effectiveness of the GEC operation depends on intensity of cosmic rays (CR), which ionize the air in the middle atmosphere and provide its conductivity. In connection with the foregoing, it can be expected: i) quantitatively, an increasing seismic activity from solar maximum to solar minimum may be in the same range as increasing CR flux; and ii) in those regions of the globe, where the crust is shipped by the magnetic field lines with number L= ~ 2.0, which are populated by anomalous cosmic rays (ACR), the relationship of seismic activity with variations in solar activity will be manifested most clearly, since there is a pronounced dependence of ACR on solar activity variations. Checking an assumption (i) with data of the global seismological catalog of the NEIC, USGS for 1973-2010, it was found that yearly number of earthquake with magnitude M≥4.5 varies into the 11 year solar cycle in a quantitative range of about 7-8% increasing to solar minimum, that qualitatively and quantitatively as well is in agreement with the

  12. Regional Characterization of Tokyo Metoropolitan area using a highly-dense seismic netwok(MeSO-net)

    NASA Astrophysics Data System (ADS)

    Hirata, N.; Nakagawa, S.; Sakai, S.; Panayotopoulos, Y.; Ishikawa, M.; Ishibe, T.; Kimura, H.; Honda, R.

    2014-12-01

    We have developed a dense seismic network, MeSO-net (Metropolitan Seismic Observation network), since 2007 in the greater Tokyo urban region under the Special Project for Earthquake Disaster Mitigation in Tokyo Metropolitan Area (FY2007-FY2011) and Special Project for Reducing Vulnerability for Urban Mega Earthquake Disasters (FY2012-FY2016)( Hirata et al., 2009). So far we have acquired more than 120TB continuous seismic data form MeSO-net which consists of about 300 seismic stations. Using MeSO-net data, we obtain clear P- and S- wave velocity tomograms (Nakagawa et al., 2010) and Qp, Qs tomograms (Panayotopoulos et al., 2014) which show a clear image of Philippine Sea Plate (PSP) and PAcific Plate (PAP). A depth to the top of PSP, 20 to 30 km beneath northern part of Tokyo bay, is about 10 km shallower than previous estimates based on the distribution of seismicity (Ishida, 1992). This shallower plate geometry changes estimations of strong ground motion for seismic hazards analysis within the Tokyo region. Based on elastic wave velocities of rocks and minerals, we interpreted the tomographic images as petrologic images. Tomographic images revealed the presence of two stepwise velocity increase of the top layer of the subducting PSP slab. Because strength of the serpentinized peridotite is not large enough for brittle fracture, if the area is smaller than previously estimated, a possible area of the large thrust fault on the upper surface of PSP can be larger than previously thought. Change of seismicity rate after the 2011 Tohoku-oki earthquake suggests change of stressing rate in greater Tokyo. Quantitative analysis of MeSO-net data shows significant increase of rate of earthquakes that have a fault orientation favorable to increasing Coulomb stress after the Tohoku-oki event.

  13. The comparative analysis of the Earth seismic activity and the variation of the Earth rotation angular velocity.

    NASA Astrophysics Data System (ADS)

    Sasorova, Elena; Levin, Boris

    2013-04-01

    It was shown [Levin, Sasorova 2012], that a cyclic increase and decrease of the seismic activity in different time intervals was observed in spatial-temporal distributions of the earthquakes (EQ) (1900-2012) with magnitude M≥7 in northwest part of the Pacific region. The spatial-temporal analysis revealed the periodic changing of the seismic activity and the depth distributions of the strong events in different time intervals. The Earth rotation angular velocity varies with time. Increasing of the angular velocity of a celestial body rotation leads to growth of oblateness of planet, and vice versa, the oblateness is decreasing with reducing of velocity of rotation. So, well-known effect of instability leads to small pulsations of the Earth surface. The Earth crust in polar areas is compressing with increasing of angular velocity of rotating planet, and it is extensible in the equator zone. The decreasing of rotation velocity leads to opposite result. The objectives of this work is the comparative spatial-temporal analysis of the seismicity regime variation (events with M>=7.0) on the whole Earth and in the Pacific region from 1900 up to date and the Earth rotation instability. The two subsets of the worldwide NEIC (USGS) catalog were used (USGS/NEIC from 1973 up to 2012 and Significant Worldwide Earthquakes (2150 B.C. - 1994 A.D.)). The preliminary standardization of magnitudes and removal of aftershocks was fulfilled for the first mentioned above subset of events. In both cases the entire range of observations was subdivided into several 5-year intervals. The temporal EQ distributions were calculated separately for six latitudinal intervals (belts): 45°-30°N, 30°-15°N, 15°-0°N, 0°-15°S, 15°-30°S, 30°-45°S. The high latitudes do not take in consideration because of very low seismic activity in these latitudes. Separately were analyzed: the EQs with M>=8 for time interval 1900-2012, and the EQs with M>=6 for time interval 1700-1900. The data base (http

  14. Evolution of earthquake rupture potential along active faults, inferred from seismicity rates and size distributions

    NASA Astrophysics Data System (ADS)

    Tormann, Thessa; Wiemer, Stefan; Enescu, Bogdan; Woessner, Jochen

    2016-04-01

    One of the major unresolved questions in seismology is the evolution in time and space of the earthquake rupture potential and thus time-dependent hazard along active faults. What happens after a major event: is the potential for further large events reduced as predicted from elastic rebound, or increased as proposed by current-state short-term clustering models? How does the rupture potential distribute in space, i.e. does it reveal imprints of stress transfer? Based on the rich earthquake record from the Pacific Plate along the Japanese coastline we investigate what information on spatial distributions and temporal changes of a normalized rupture potential (NRP) for different magnitudes can be derived from time-varying, local statistical characteristics of well and frequently observed small-to-moderate seismicity. Seismicity records show strong spatio-temporal variability in both activity rates and size distribution. We analyze 18 years of seismicity, including the massive 2011 M9 Tohoku earthquake and its aftermath. We show that the size distribution of earthquakes has significantly changed before (increased fraction of larger magnitudes) and after that mainshock (increased fraction of smaller magnitudes), strongest in areas of highest coseismic slip. Remarkably, a rapid recovery of this effect is observed within only few years. We combine this significant temporal variability in earthquake size distributions with local activity rates and infer the evolution of NRP distributions. We study complex spatial patterns and how they evolve, and more detailed temporal characteristics in a simplified spatial selection, i.e. inside and outside the high slip zone of the M9 earthquake. We resolve an immediate and strong NRP increase for large events prior to the Tohoku event in the subsequent high slip patch and a very rapid decrease inside this high-stress-release area, coupled with a lasting increase of NRP in the immediate surroundings. Even in the center of the Tohoku

  15. Application of seismic velocity tomography in underground coal mines: A case study of Yima mining area, Henan, China

    NASA Astrophysics Data System (ADS)

    Cai, Wu; Dou, Linming; Cao, Anye; Gong, Siyuan; Li, Zhenlei

    2014-10-01

    A better understanding of geological structures, stress regimes, and rock burst risks around longwall mining panels can allow for higher extraction efficiency with reduced safety concerns. In this paper, the stress change of rock mass was first examined by using ultrasonic technique into laboratory-scale rock samples. Subsequently, the active and passive seismic velocity tomograms were simultaneously applied into two study cases with field-scale. Similar characteristics can be found between the active and passive tomography results. More specifically, in the first case, a geological discontinuity was clearly indicated by a linear image in both active and passive seismic tomography results. The results of the second case suggest that seismic tomography can be used to infer stress redistribution, and assess rock burst hazard or locate high-seismicity zones. Ultimately, comparisons have been made between the results of active and passive seismic tomography. Active tomography is found to be better applied in accurately detecting stress distribution and geological structures prior to the extraction of longwall panels, while passive tomography has advantages in continuously monitoring the stress changes and assessing rock burst potential during the mining of longwall panels. This study is expected to increase the safety and efficiency of the underground mining.

  16. Three-dimensional elastic full waveform inversion using seismic data from the Sleipner area

    NASA Astrophysics Data System (ADS)

    Raknes, Espen Birger; Arntsen, Børge; Weibull, Wiktor

    2015-09-01

    In this study, we demonstrate the application of 3-D isotropic elastic full waveform inversion (FWI) to a field data set from the Sleipner area in the North sea. The field data set consists of a narrow azimuth marine towed streamer survey. The limited maximum offset of less than 2000 m poses strong challenges for the FWI technique, due to the lack of wide-angle wave phenomena, particularly for the deeper sediments. In addition, the lack of information about shear waves implies that only the P-wave velocities can be estimated with some confidence. In this work, the P-wave velocities are inverted using FWI, whereas the S-wave velocities and densities are coupled to the P-wave velocities using empirical relationships. To check the validity of this work flow, a synthetic sensitivity analysis inspired by a well log from the area is performed. In this analysis the difference between acoustic and elastic FWI is also compared. The conclusion from the sensitivity analysis is that, as long as the empirical relationships are not too far away from the true relationships, the elastic FWI is able to resolve the subsurface parameters within an acceptable error margin. Furthermore, the acoustic approximation fails due to the large differences between the elastic and acoustic reflection and transmission coefficients, meaning that elastic FWI is necessary for resolving the parameters satisfactorily. Acoustic and elastic FWI are performed for the field data. The results of the field data example show that elastic FWI produces an elastic model which accurately simulates the observed data, whereas the acoustic FWI produces an acoustic model that includes artefacts, particularly in the upper part close to the sea bottom. Elastic FWI is therefore favourable for short offset seismic streamer data. The estimated elastic P-wave velocity models were used to depth migrate the data. The depth migrated images show improved resolution and continuity compared to those migrated using a model

  17. Quaternary grabens in southernmost Illinois: Deformation near an active intraplate seismic zone

    USGS Publications Warehouse

    Nelson, W.J.; Denny, F.B.; Follmer, L.R.; Masters, J.M.

    1999-01-01

    Narrow grabens displace Quaternary sediments near the northern edge of the Mississippi Embayment in extreme southern Illinois, east-central United States. Grabens are part of the Fluorspar Area Fault Complex (FAFC), which has been recurrently active throughout Phanerozoic time. The FAFC strikes directly toward the New Madrid Seismic Zone (NMSZ), scene of some of the largest intra-plate earthquakes in history. The NMSZ and FAFC share origin in a failed Cambrian rift (Reelfoot Rift). Every major fault zone of the FAFC in Illinois exhibits Quaternary displacement. The structures appear to be strike-slip pull-apart grabens, but the magnitude and direction of horizontal slip and their relationship to the current stress field are unknown. Upper Tertiary strata are vertically displaced more than 100 m, Illinoian and older Pleistocene strata 10 to 30 m, and Wisconsinan deposits 1 m or less. No Holocene deformation has been observed. Average vertical slip rates are estimated at 0.01 to 0.03 mm/year, and recurrence intervals for earthquakes of magnitude 6 to 7 are on the order of 10,000s of years for any given fault. Previous authors remarked that the small amount of surface deformation in the New Madrid area implies that the NMSZ is a young feature. Our findings show that tectonic activity has shifted around throughout the Quaternary in the central Mississippi Valley. In addition to the NMSZ and southern Illinois, the Wabash Valley (Illinois-Indiana), Benton Hills (Missouri), Crowley's Ridge (Arkansas-Missouri), and possibly other sites have experienced Quaternary tectonism. The NMSZ may be only the latest manifestation of seismicity in an intensely fractured intra-plate region.

  18. Active Source Tomography of Stromboli Volcano (Italy): Results From the 2006 Seismic Experiment.

    NASA Astrophysics Data System (ADS)

    Zuccarello, L.; Patanè, D.; Cocina, O.; Castellano, M.; Sgroi, T.; Favali, P.; de Gori, P.

    2008-12-01

    Stromboli island, located in the Southern Tyrrhenian sea, is the emerged part (about 900 m a.s.l.) of a 3km-high strato-volcano. Its persistent Strombolian activity, documented for over 2000 years, is sometimes interrupted by lava effusions or major explosions. Despite the amount of recent published geophysical studies aimed to clarifying eruption dynamics, the spatial extend and geometrical characteristics of the plumbing system remain poorly understood. In fact, the knowledge of the inner structure and the zones of magma storage is limited to the upper few hundreds meters of the volcanic edifice and P- and S-waves velocity models are available only in restricted areas. In order to obtain a more suitable internal structural and velocity models of the volcano, from 25 November to 2 December 2006, a seismic tomography experiment through active seismics using air-gun sources was carried out and the final Vp model is here presented. The data has been inverted for the Vp structure by using the code Simulps13q, considering a 3D grid of nodes spaced 0.5 km down to 2 km depth, beneath the central part of volcano. The results show a relatively high velocity zones located both in the inner part of the volcanic structure, at about 1km b.s.l. and in the last 200-300 m a.s.l. in correspondence with the volcanic conduit. Slower zones were located around the summit craters in agreement with volcanological and petrological informations for the area. The relatively high velocity zones could suggest the presence of intrusive bodies related to the plumbing system.

  19. New inferences from spectral seismic energy measurement of a link between regional seismicity and volcanic activity at Mt. Etna, Italy

    NASA Astrophysics Data System (ADS)

    Ortiz, R.; Falsaperla, S.; Marrero, J. M.; Messina, A.

    2009-04-01

    The existence of a relationship between regional seismicity and changes in volcanic activity has been the subject of several studies in the last years. Generally, activity in basaltic volcanoes such as Villarica (Chile) and Tungurahua (Ecuador) shows very little changes after the occurrence of regional earthquakes. In a few cases volcanic activity has changed before the occurrence of regional earthquakes, such as observed at Teide, Tenerife, in 2004 and 2005 (Tárraga et al., 2006). In this paper we explore the possible link between regional seismicity and changes in volcanic activity at Mt. Etna in 2006 and 2007. On 24 November, 2006 at 4:37:40 GMT an earthquake of magnitude 4.7 stroke the eastern coast of Sicily. The epicenter was localized 50 km SE of the south coast of the island, and at about 160 km from the summit craters of Mt. Etna. The SSEM (Spectral Seismic Energy Measurement) of the seismic signal at stations at 1 km and 6 km from the craters highlights that four hours before this earthquake the energy associated with volcanic tremor increased, reached a maximum, and finally became steady when the earthquake occurred. Conversely, neither before nor after the earthquake, the SSEM of stations located between 80 km and 120 km from the epicentre and outside the volcano edifice showed changes. On 5 September, 2007 at 21:24:13 GMT an earthquake of magnitude 3.2 and 7.9 km depth stroke the Lipari Island, at the north of Sicily. About 38 hours before the earthquake occurrence, there was an episode of lava fountain lasting 20 hours at Etna volcano. The SSEM of the seismic signal recorded during the lava fountain at a station located at 6 km from the craters highlights changes heralding this earthquake ten hours before its occurrence using the FFM method (e.g., Voight, 1988; Ortiz et al., 2003). A change in volcanic activity - with the onset of ash emission and Strombolian explosions - was observed a couple of hours before the occurrence of the regional

  20. Active and long-lived permanent forearc deformation driven by the subduction seismic cycle

    NASA Astrophysics Data System (ADS)

    Aron Melo, Felipe Alejandro

    I have used geological, geophysical and engineering methods to explore mechanisms of upper plate, brittle deformation at active forearc regions. My dissertation particularly addresses the permanent deformation style experienced by the forearc following great subduction ruptures, such as the 2010 M w8.8 Maule, Chile and 2011 Mw9.0 Tohoku, Japan earthquakes. These events triggered large, shallow seismicity on upper plate normal faults above the rupture reaching Mw7.0. First I present new structural data from the Chilean Coastal Cordillera over the rupture zone of the Maule earthquake. The study area contains the Pichilemu normal fault, which produced the large crustal aftershocks of the megathrust event. Normal faults are the major neotectonic structural elements but reverse faults also exist. Crustal seismicity and GPS surface displacements show that the forearc experiences pulses of rapid coseismic extension, parallel to the heave of the megathrust, and slow interseismic, convergence-parallel shortening. These cycles, over geologic time, build the forearc structural grain, reactivating structures properly-oriented respect to the deformation field of each stage of the interplate cycle. Great subduction events may play a fundamental role in constructing the crustal architecture of extensional forearc regions. Static mechanical models of coseismic and interseismic upper plate deformation are used to explore for distinct features that could result from brittle fracturing over the two stages of the interplate cycle. I show that the semi-elliptical outline of the first-order normal faults along the Coastal Cordillera may define the location of a characteristic, long-lived megathrust segment. Finally, using data from the Global CMT catalog I analyzed the seismic behavior through time of forearc regions that have experienced great subduction ruptures >Mw7.7 worldwide. Between 61% and 83% of the cases where upper plate earthquakes exhibited periods of increased seismicity

  1. Volcanic activity observed from continuous seismic records in the region of the Klyuchevskoy group of volcanoes

    NASA Astrophysics Data System (ADS)

    Shapiro, N.; Droznin, D.; Droznina, S.; Senyukov, S.; Chebrov, V.; Gordeev, E.; Frank, W.

    2015-12-01

    We analyze continuous seismic records from 18 permanent stations operated in vicinity of the Klyuchevskoy group of volcanos (Kamchatka, Russia) during the period between 2009 and 2014. We explore the stability of the inter-station cross-correlation to detect different periods of sustained emission from seismic energy. The main idea of this approach is that cross-correlation waveforms computed from a wavefield emitted by a seismic source from a fixed position remain stable during the period when this source is acting. The detected periods of seismic emission correspond to different episodes of activity of volcanoes: Klyuchevskoy, Tolbachik, Shiveluch, and Kizimen. For Klyuchevskoy and Tolbachik whose recent eruptions are mostly effusive, the detected seismic signals correspond to typical volcanic tremor, likely caused by degassing processes. For Shiveluch and Kizimen producing more silicic lavas, the observed seismic emission often consists of many repetitive long period (LP) seismic events that might be related to the extrusion of viscous magmas. We develop an approach for automatic detection of these individual LP events in order to characterize variations of their size and recurrence in time.

  2. On causes of the low seismic activity in the Earth's polar latitudes

    NASA Astrophysics Data System (ADS)

    Levin, Boris; Sasorova, Elena; Domanski, Andrei

    2016-04-01

    The irregularity of distribution of seismic activity in the world was observed at the beginning of the era of instrumental seismology (B. Gutenberg, C. Richter, K. Kasahara). At the same time, the global nature of the symmetry of this effect has been established only in this millennium, with the participation of authors (Levin B.W., Sasorova E.V., 2010). Analysis of the global earthquake catalogs showed that almost all seismic events over the last century occurred within a limited latitudinal band contained between the 65 N and 65 S. The seismic activity in the polar regions of the planet was manifested very weakly. The reasons for such features were found by following the analysis of the characteristics associated with the theory of the figure of the Earth. In the works of the French mathematician A. Veronne (1912) was the first to introduce the concept of "critical" latitudes (φ1 = ±35°15' 22″) wherein the radius of the ellipsoid of revolution is equal to the radius of the sphere of the same volume. Variation of the radius vector of the ellipsoid at this latitude is equal to zero. There is the boundary between the compressed areas of the polar zones and equatorial region, where the rocks of the Earth are dominated by tensile forces. Analysis of the specific characteristics of the gravity force distribution on the surface of the ellipsoid has shown that there is a distribution of the same character with a singular point at latitude φ2 = ±61° 52' 12″. In case of variations in the angular velocity of the planet's rotation the variation of gravity force at the latitude φ2 is negligible, compared with variations of gravity force on the equator and pole, which exceed the previous value by 3-4 orders. Attempted analysis of the model of the ellipsoid of revolution in the theory of axisymmetric elastic shells has allowed to establish that in the elastic shell of the planet must occur meridional and ring forces. The theory shows that when the flatness (or polar

  3. Martian seismicity

    NASA Technical Reports Server (NTRS)

    Phillips, Roger J.; Grimm, Robert E.

    1991-01-01

    The design and ultimate success of network seismology experiments on Mars depends on the present level of Martian seismicity. Volcanic and tectonic landforms observed from imaging experiments show that Mars must have been a seismically active planet in the past and there is no reason to discount the notion that Mars is seismically active today but at a lower level of activity. Models are explored for present day Mars seismicity. Depending on the sensitivity and geometry of a seismic network and the attenuation and scattering properties of the interior, it appears that a reasonable number of Martian seismic events would be detected over the period of a decade. The thermoelastic cooling mechanism as estimated is surely a lower bound, and a more refined estimate would take into account specifically the regional cooling of Tharsis and lead to a higher frequency of seismic events.

  4. Shallow Seismic Reflection Study of Recently Active Fault Scarps, Mina Deflection, Western Nevada

    NASA Astrophysics Data System (ADS)

    Black, R. A.; Christie, M.; Tsoflias, G. P.; Stockli, D. F.

    2006-12-01

    During the spring and summer of 2006 University of Kansas geophysics students and faculty acquired shallow, high resolution seismic reflection data over actively deforming alluvial fans developing across the Emmigrant Peak (in Fish Lake Valley) and Queen Valley Faults in western Nevada. These normal faults represent a portion of the transition from the right-lateral deformation associated with the Walker Lane/Eastern California Shear Zone to the normal and left-lateral faulting of the Mina Deflection. Data were gathered over areas of recent high resolution geological mapping and limited trenching by KU students. An extensive GPR data grid was also acquired. The GPR results are reported in Christie, et al., 2006. The seismic data gathered in the spring included both walkaway tests and a short CMP test line. These data indicated that a very near-surface P-wave to S-wave conversion was taking place and that very high quality S-wave reflections were probably dominating shot records to over one second in time. CMP lines acquired during the summer utilized a 144 channel networked Geode system, single 28 hz geophones, and a 30.06 downhole rifle source. Receiver spacing was 0.5 m, source spacing 1.0m and CMP bin spacings were 0.25m for all lines. Surveying was performed using an RTK system which was also used to develop a concurrent high resolution DEM. A dip line of over 400m and a strike line over 100m in length were shot across the active fan scarp in Fish Lake Valley. Data processing is still underway. However, preliminary interpretation of common-offset gathers and brute stacks indicates very complex faulting and detailed stratigraphic information to depths of over 125m. Depth of information was actually limited by the 1024ms recording time. Several west-dipping normal faults downstep towards the basin. East-dipping antithetic normal faulting is extensive. Several distinctive stratigraphic packages are bound by the faults and apparent unconformitites. A CMP dip line

  5. Neogene tectonics and modern geodynamics and seismicity of Pannonia north-eastern remote area (Ukrainian Transcarpathian yield)

    NASA Astrophysics Data System (ADS)

    Lozynak, Petro; Nazarevych, Andriy; Nazarevych, Lesya

    2010-05-01

    Pannonia north-eastern remote area (Ukrainian Transcarpathian yield) joins to East (Ukrainian) Carpathians and their geodynamic mode is interdependent from the alpine stage until now. Due to the detailed study in the last few years of structures of surface of basement and sedimentary layers of the Transcarpathian yield of postalpine ages (neogene - from early Miocene to Sarmatian and farther) (see Lozynak at al., 2002-2007) we have the possibility to trace the Neogene's tectonics of the region and its connection with modern geodynamics and seismicity of Ukrainian Transcarpathians and adjoining territories of Slovakia, Hungary and Romania. These data indicate that active orogenic processes (dominance of compression caused by a plate-tectonic processes) in this region to beginning of early miocene made off and began the process of formation of the Transcarpathian yield in his modern view (due to an output on the first plan of the plum-tectonic processes caused by Pannonian asthenolite?) (see Nazarevych A. and Nazarevych L., 2000-2007). The process of formation (origin) of yield (and the proper accumulation of sedimentary layers) began in his east part (in the area of border with Romania (Siget - Solotvyno)) at the beginning of early Miocene (about 23 million years ago), continue in north-western direction (in the rear of modern Carpathians) to the border with Slovakia at first as a narrow (10-15 km) bar (roughly during 2-4 million years) and then broadened (during next 2-3 million years) in north-eastern - south-west direction on all modern territory of the Transcarpathian yield. In future (in Sarmatian epoch, approximately from 12-14 to 10-11 million years ago) east part of yield (so-called Solotvyno depression) transgress to the mode of compression and raising with ending of intensive sedimentation, and in western part (so-called Tchop-Mukatcheve depression) the process of sagging was farther displaced westward and at present he is concentrated (by geodesic and

  6. Creating realistic models and resolution assessment in tomographic inversion of wide-angle active seismic profiling data

    NASA Astrophysics Data System (ADS)

    Stupina, T.; Koulakov, I.; Kopp, H.

    2009-04-01

    We consider questions of creating structural models and resolution assessment in tomographic inversion of wide-angle active seismic profiling data. For our investigations, we use the PROFIT (Profile Forward and Inverse Tomographic modeling) algorithm which was tested earlier with different datasets. Here we consider offshore seismic profiling data from three areas (Chile, Java and Central Pacific). Two of the study areas are characterized by subduction zones whereas the third data set covers a seamount province. We have explored different algorithmic issues concerning the quality of the solution, such as (1) resolution assessment using different sizes and complexity of synthetic anomalies; (2) grid spacing effects; (3) amplitude damping and smoothing; (4) criteria for rejection of outliers; (5) quantitative criteria for comparing models. Having determined optimal algorithmic parameters for the observed seismic profiling data we have created structural synthetic models which reproduce the results of the observed data inversion. For the Chilean and Java subduction zones our results show similar patterns: a relatively thin sediment layer on the oceanic plate, thicker inhomogeneous sediments in the overlying plate and a large area of very strong low velocity anomalies in the accretionary wedge. For two seamounts in the Pacific we observe high velocity anomalies in the crust which can be interpreted as frozen channels inside the dormant volcano cones. Along both profiles we obtain considerable crustal thickening beneath the seamounts.

  7. Reflection seismic imaging of a hydraulically conductive fracture zone in a high noise area, Forsmark, Sweden

    NASA Astrophysics Data System (ADS)

    Juhlin, C.; Stephens, M. B.; Cosma, C.

    2007-05-01

    High resolution reflection seismic methods have proven to be useful tools for locating fracture zones in crystalline rock. Siting of potential high-level nuclear waste repositories is a particularly important application of these methods. By using small explosive sources (15-75 grams), high resolution images of the sub-surface have been obtained in the depth range 100 m to 2 km in Sweden, Canada and elsewhere. Although ambient noise conditions in areas such as the Fennoscandian and Canadian shields are generally low, industrial noise can be high in some areas, particularly at potential sites suitable for repositories, since these are often close to existing infrastructure. In addition, the presence of this infrastructure limits the choice of sources available to the geophysicist. Forsmark, located about 140 km north of Stockholm, is one such potential site where reflection seismics have been carried out. Existing infrastructure includes nuclear reactors for power generation and a low- level waste repository. In the vicinity of the reactors, it was not possible to use an explosive source due to permitting restrictions. Instead, a VIBSIST system consisting of a tractor mounted hydraulic hammer was used in the vicinity of the reactors. By repeatedly hitting the pavement, without breaking it, at predefined sweeps and then stacking the signals, shot records comparable to explosive data could be generated. These shot records were then processed using standard methods to produce stacked sections along 3 profiles within the reactor area. Clear reflections are seen in the uppermost 600 m along 3 of these profiles. Correlation of crossing profiles shows that the strongest reflection (B8) is generated by a gently east-southeast dipping interface. Prior to construction of the reactors, several boreholes were drilled to investigate the bedrock in the area. One of these boreholes was located close to where two of the profiles cross. Projection of the B8 reflection into the

  8. Seismic activity near the Moriyoshi-zan volcano in Akita Prefecture, northeastern Japan: implications for geofluid migration and a midcrustal geofluid reservoir

    NASA Astrophysics Data System (ADS)

    Kosuga, M.

    2014-12-01

    The 2011 off the Pacific coast of Tohoku (Tohoku-oki) earthquake caused increased seismicity in many inland areas in Japan. A triggered seismic cluster north of the Moriyoshi-zan volcano in Akita prefecture, Tohoku District, is of interest in light of the contribution of geofluids to seismic activity. We observed an active seismic cluster characterized by the migration of seismicity and reflected/scattered phases. We relocated hypocenters of the cluster using data from temporal observations and the hypoDD location technique, which significantly increased the hypocentral accuracy. We interpreted a complex spatiotemporal variation of seismicity in the cluster as the migration of pore fluid pressure from multiple pressure sources. The hydraulic diffusivity of the cluster was in the range of 0.01 to 0.7 m2/s and increased with time, implying that the migration of hypocenters accelerated after a pathway for fluids was formed by fracturing of the wall rock during the initial stage of seismic activity. A prominent feature of the seismograms is a reflected/scattered phase observed at stations around the volcano. We regard the phase as S-to-S scattered waves and estimated the location of the scatterers using a back-projection method. The scatterers are inferred to be located about 5 km northwest of the Moriyoshi-zan volcano, at an approximate depth of 13 km. The Moriyoshi-zan area is one of the source areas of deep low-frequency earthquakes that have been interpreted as events generated by the migration of geofluids. The depth of the scatterers is close to the upper depth limit of low-frequency earthquakes. Thus, we interpret the observed scatterers to be a reservoir of geofluid that came from the uppermost mantle accompanying contemporaneous low-frequency earthquakes.

  9. Stable and unstable phases of elevated seismic activity at the persistently restless Telica Volcano, Nicaragua

    NASA Astrophysics Data System (ADS)

    Rodgers, Mel; Roman, Diana C.; Geirsson, Halldor; LaFemina, Peter; McNutt, Stephen R.; Muñoz, Angelica; Tenorio, Virginia

    2015-01-01

    Telica Volcano, Nicaragua, is a persistently restless volcano with daily seismicity rates that can vary by orders of magnitude without apparent connection to eruptive activity. Low-frequency (LF) events are dominant and peaks in seismicity rate show little correlation with eruptive episodes, presenting a challenge for seismic monitoring and eruption forecasting. A short period seismic station (TELN) has been operated on Telica's summit since 1993, and in 2010 the installation of a six-station broadband seismic and eleven-station continuous GPS network (the TESAND network) was completed to document in detail the seismic characteristics of a persistently restless volcano. Between our study period of November 2009 and May 2013, over 400,000 events were detected at the TESAND summit station (TBTN), with daily event rates ranging from 5 to 1400. We present spectral analyses and classifications of ~ 200,000 events recorded by the TESAND network between April 2010 and March 2013, and earthquake locations for a sub-set of events between July 2010 and February 2012. In 2011 Telica erupted in a series of phreatic vulcanian explosions. Six months before the 2011 eruption, we observe a sudden decrease in LF events concurrent with a swarm of high-frequency (HF) events, followed by a decline in overall event rates, which reached a minimum at the eruption onset. We observe repeated periods of high and low seismicity rates and suggest these changes in seismicity represent repeated transitions between open-system and closed-system degassing. We suggest that these short- and long-term transitions between open to closed-system degassing form part of a long-term pattern of stable vs. unstable phases at Telica. Stable phases are characterised by steady high-rate seismicity and represent stable open-system degassing, whereas unstable phases are characterised by highly variable seismicity rates and represent repeated transitions from open to closed-system degassing, where the system is

  10. Coal-mining seismicity and ground-shaking hazard: A case study in the Trail Mountain area, Emery County, Utah

    USGS Publications Warehouse

    Arabasz, W.J.; Nava, S.J.; McCarter, M.K.; Pankow, K.L.; Pechmann, J.C.; Ake, J.; McGarr, A.

    2005-01-01

    We describe a multipart study to quantify the potential ground-shaking hazard to Joes Valley Dam, a 58-m-high earthfill dam, posed by mining-induced seismicity (MIS) from future underground coal mining, which could approach as close as ???1 km to the dam. To characterize future MIS close to the dam, we studied MIS located ???3-7 km from the dam at the Trail Mountain coal mine. A 12-station local seismic network (11 stations above ground, one below, combining eight triaxial accelerometers and varied velocity sensors) was operated in the Trail Mountain area from late 2000 through mid-2001 for the dual purpose of (1) continuously monitoring and locating MIS associated with longwall mining at a depth of 0.5-0.6 km and (2) recording high-quality data to develop ground-motion prediction equations for the shallow MIS. (Ground-motion attenuation relationships and moment-tensor results are reported in companion articles.) Utilizing a data set of 1913 earthquakes (M ??? 2.2), we describe space-time-magnitude distributions of the observed MIS and source-mechanism information. The MIS was highly correlated with mining activity both in space and time. Most of the better-located events have depths constrained within ??0.6 km of mine level. For the preponderance (98%) of the 1913 located events, only dilatational P-wave first motions were observed, consistent with other evidence for implosive or collapse-type mechanisms associated with coal mining in this region. We assess a probable maximum magnitude of M 3.9 (84th percentile of a cumulative distribution) for potential MIS close to Joes Valley Dam based on both the worldwide and regional record of coal-mining-related MIS and the local geology and future mining scenarios.

  11. Improved Subsurface Imaging of Deep Seismic Data in Areas with Rugged Topography and Crooked-line Geometries

    NASA Astrophysics Data System (ADS)

    Abe, S.; Ito, T.; Brown, L. D.; Ikawa, T.

    2001-12-01

    Deep seismic reflection surveying in mountainous areas imposes serious restrictions and compromises on both data processing and acquisition. In addition to complex subsurface structure, rugged acquisition topography, crookedness of seismic lines and irregular distribution of shots often result in poor data quality. High-velocity rocks at the surface can cause shot and receiver coupling problems, and produce misalignments of seismic traces due to improperly-determined statics. Furthermore back-scattered energy from off-line surfaces can get trapped in weathered layers and generate unwanted coherent noise. We have investigated the applicability and limitations of conventional processing to deal with the problems related to acquisition geometries. We evaluated and modified the following options in data processing to improve the deep seismic image: (1) Simultaneous application of Kirchhoff trace mapping and local-datum corrections (wave-equation datuming or static time shift); (2) Kirchhoff imaging to account for the crookedness of shot and receiver lines; (3) Simultaneous application of 3D DMO trace mapping and cross-dip corrections; (4) Accurate estimation of refraction/reflection statics by turning-ray tomography and global-optimization method. The seismic datasets used for this case study are a 2D seismic profile acquired in Hidaka mountains on Hokkaido, northeast Japan, and a 2D seismic profile from the INDEPTH Project in the Himalayas. The result of imaging crustal structure of the Hidaka collision zone has revealed that the Kuril arc lithosphere is delaminated at about 23km deep in the lower crust. Also, we find that the above processing strategy significantly improved imaging of structure in the upper plate of the Himalayan megathrust.

  12. Seismic activity near the Moriyoshi-zan volcano in Akita Prefecture, northeastern Japan: implications for geofluid migration and a midcrustal geofluid reservoir

    NASA Astrophysics Data System (ADS)

    Kosuga, Masahiro

    2014-12-01

    The 2011 off the Pacific coast of Tohoku (Tohoku-oki) earthquake caused increased seismicity in many inland areas in Japan. A seismic cluster north of the Moriyoshi-zan volcano in Akita prefecture, Tohoku District, is of interest in light of the contribution of geofluids to seismic activity. We observed a seismic cluster characterized by the migration of seismicity and reflected/scattered phases. We relocated hypocenters of the cluster using data from temporal observations and the hypoDD location technique, which significantly increased the hypocentral accuracy. We interpreted a complex spatiotemporal variation of seismicity in the cluster as the migration of pore fluid pressure from multiple pressure sources. The hydraulic diffusivity of the cluster was in the range of 0.01 to 0.7 m2/s and increased with time, implying that the migration of hypocenters accelerated after a pathway for fluids was formed by fracturing of the wall rock during the initial stage of seismic activity. A prominent feature of the seismograms is a reflected/scattered phase observed at stations around the volcano. We regard the phase as S-to- S scattered waves and estimated the location of the scatterers using a back-projection method. The scatterers are inferred to be located about 5 km northwest of the Moriyoshi-zan volcano, at an approximate depth of 13 km. The Moriyoshi-zan area is one of the source areas of deep low-frequency earthquakes that have been interpreted as events generated by the migration of geofluids. The depth of the scatterers is close to the upper limit of the depth at which low-frequency earthquakes occur. Thus, we interpret the observed scatterers to be a reservoir of geofluid that came from the uppermost mantle accompanying contemporaneous low-frequency earthquakes.

  13. Feasibility and Interest in Earthquake Early Warning Systems for Areas of Moderate Seismicity: Case Study for the Pyrenees

    NASA Astrophysics Data System (ADS)

    Auclair, Samuel; Goula, Xavier; Jara, Jose-Antonio; Colom, Yolanda

    2015-09-01

    Seismic risk in areas of moderate seismicity (AMS) is a reality and destructive earthquakes may occur there. This is why stakeholders and risk managers in these areas show an increasing interest in Earthquake Early Warning Systems (EEWS) and are wondering about the possibility of equipping their territories with such systems. This question of feasibility has to be broached globally: distinguishing technical feasibility from notions of opportunity and utility, an, thus, it has to involve both scientific experts and stakeholders. Moreover, it is necessary to consider each situation specifically without any preconceptions, specifically concerning potential uses that can be made of early warnings, in particular, it is clear that when applied to AMS, the EEWS principles translate into shorter lead times than the ones expected for more seismic areas and would, consequently, require considering new ways of using early warnings. Through the experience conducted for the Pyrenees (France-Spain border) as part of the SISPyr project, this study aims at identifying responses to the potential value of EEWS as real-time seismic risk mitigation tools for AMS as well as to offer a methodological framework to guide stakeholders in their assessment of opportunities to set up EEWS.

  14. Correlation Between Radon Outgassing and Seismic Activity Along the Hayward Fault Near Berkeley, California

    NASA Astrophysics Data System (ADS)

    Holtmann-Rice, D.; Cuff, K.

    2003-12-01

    Results from previous studies indicate that radon concentration values are significantly higher over selected sections of the Hayward fault than adjacent areas. This phenomenon is believed to be attributed to the presence of abundant fractures in rock associated with the fault, which act as pathways for radon as it migrates from depth towards the earth?s surface. In an attempt to determine whether or not a relationship exists between seismicity along the fault, the production of microfractures, and emanation of radon, a radon outgassing monitoring study was conducted along an active section of the Hayward fault in Berkeley, California. The study was carried out by using an alphaMETER 611, which is a device capable of accurately measuring radon concentrations every 15 minutes. The alphaMETER was placed at the bottom of a sealed one meter deep well, in close proximity to a section of the Hayward fault located along the northwestern face of the Berkeley Hills. Once per week for several months data collected by the alphaMETER was downloaded into a laptop computer. Data from the alphaMETER was then compared with seismic data recorded by local seismometers to see if any correlation existed. A general correlation between variation in radon concentration and the occurrence of small earthquakes was found. Significant peaks in radon concentration were observed within an approximately one week period before the occurrence of small earthquakes. Concentration values then decreased dramatically just prior to and during periods when the earthquakes occurred. Such correlation is very similar to that recently observed in association with a magnitude five earthquake along the Anatolian Fault, reported by geoscientists working in Turkey using similar instrumentation (Inan, 2003, personal communication). The most plausible explanation for the observed correlation is as follows: 1) prior to a given earthquake, stress build up within a particular fault region leads to the formation of

  15. Near-Surface Seismic Reflection and GPR Imaging of the Active Emigrant Peak Fault, Fish Lake Valley, NV

    NASA Astrophysics Data System (ADS)

    Black, R. A.; Christie, M. W.; Tsoflias, G. P.; Stockli, D. F.

    2007-12-01

    cumulative depth/throw history for each fault using both data sets. The seismic data allows us to quantify cumulative fault throw vs. depth at scales of meters to tens of meters. The GPR is more limited. The GPR data is, however, absolutely necessary to confidently identify the faults. The two data types are thus complimentary, especially in areas of complex 'off-fault' deformation and active sedimentation.

  16. 3D crustal seismic velocity model for the Gulf of Cadiz and adjacent areas (SW Iberia margin) based on seismic reflection and refraction profiles

    NASA Astrophysics Data System (ADS)

    Lozano, Lucía; Cantavella, Juan Vicente; Barco, Jaime; Carranza, Marta; Burforn, Elisa

    2016-04-01

    The Atlantic margin of the SW Iberian Peninsula and northern Morocco has been subject of study during the last 30 years. Many seismic reflection and refraction profiles have been carried out offshore, providing detailed information about the crustal structure of the main seafloor tectonic domains in the region, from the South Portuguese Zone and the Gulf of Cadiz to the Abyssal Plains and the Josephine Seamount. The interest to obtain a detailed and realistic velocity model for this area, integrating the available data from these studies, is clear, mainly to improve real-time earthquake hypocentral location and for tsunami and earthquake early warning. Since currently real-time seismic location tools allow the implementation of 3D velocity models, we aim to generate a full 3D crustal model. For this purpose we have reviewed more than 50 profiles obtained in different seismic surveys, from 1980 to 2008. Data from the most relevant and reliable 2D seismic velocity published profiles were retrieved. We first generated a Moho depth map of the studied area (latitude 32°N - 41°N and longitude 15°W - 5°W) by extracting Moho depths along each digitized profile with a 10 km spacing, and then interpolating this dataset using ordinary kriging method and generating the contour isodepth map. Then, a 3D crustal velocity model has been obtained. Selected vertical sections at different distances along each profile were considered to retrieve P-wave velocity values at each interface in order to reproduce the geometry and the velocity gradient within each layer. A double linear interpolation, both in distance and depth, with sampling rates of 10 km and 1 km respectively, was carried out to generate a (latitude, longitude, depth, velocity) matrix. This database of all the profiles was interpolated to obtain the P-wave velocity distribution map every kilometer of depth. The new 3D velocity model has been integrated in NonLinLoc location program to relocate several representative

  17. Predicting earthquakes by analyzing accelerating precursory seismic activity

    USGS Publications Warehouse

    Varnes, D.J.

    1989-01-01

    During 11 sequences of earthquakes that in retrospect can be classed as foreshocks, the accelerating rate at which seismic moment is released follows, at least in part, a simple equation. This equation (1) is {Mathematical expression},where {Mathematical expression} is the cumulative sum until time, t, of the square roots of seismic moments of individual foreshocks computed from reported magnitudes;C and n are constants; and tfis a limiting time at which the rate of seismic moment accumulation becomes infinite. The possible time of a major foreshock or main shock, tf,is found by the best fit of equation (1), or its integral, to step-like plots of {Mathematical expression} versus time using successive estimates of tfin linearized regressions until the maximum coefficient of determination, r2,is obtained. Analyzed examples include sequences preceding earthquakes at Cremasta, Greece, 2/5/66; Haicheng, China 2/4/75; Oaxaca, Mexico, 11/29/78; Petatlan, Mexico, 3/14/79; and Central Chile, 3/3/85. In 29 estimates of main-shock time, made as the sequences developed, the errors in 20 were less than one-half and in 9 less than one tenth the time remaining between the time of the last data used and the main shock. Some precursory sequences, or parts of them, yield no solution. Two sequences appear to include in their first parts the aftershocks of a previous event; plots using the integral of equation (1) show that the sequences are easily separable into aftershock and foreshock segments. Synthetic seismic sequences of shocks at equal time intervals were constructed to follow equation (1), using four values of n. In each series the resulting distributions of magnitudes closely follow the linear Gutenberg-Richter relation log N=a-bM, and the product n times b for each series is the same constant. In various forms and for decades, equation (1) has been used successfully to predict failure times of stressed metals and ceramics, landslides in soil and rock slopes, and volcanic

  18. Analysis of the seismic activity associated with the 2010 eruption of Merapi Volcano, Java

    NASA Astrophysics Data System (ADS)

    Budi-Santoso, Agus; Lesage, Philippe; Dwiyono, Sapari; Sumarti, Sri; Subandriyo; Surono; Jousset, Philippe; Metaxian, Jean-Philippe

    2013-07-01

    The 2010 eruption of Merapi is the first large explosive eruption of the volcano that has been instrumentally observed. The main characteristics of the seismic activity during the pre-eruptive period and the crisis are presented and interpreted in this paper. The first seismic precursors were a series of four shallow swarms during the period between 12 and 4 months before the eruption. These swarms are interpreted as the result of perturbations of the hydrothermal system by increasing heat flow. Shorter-term and more continuous precursory seismic activity started about 6 weeks before the initial explosion on 26 October 2010. During this period, the rate of seismicity increased almost constantly yielding a cumulative seismic energy release for volcano-tectonic (VT) and multiphase events (MP) of 7.5 × 1010 J. This value is 3 times the maximum energy release preceding previous effusive eruptions of Merapi. The high level reached and the accelerated behavior of both the deformation of the summit and the seismic activity are distinct features of the 2010 eruption. The hypocenters of VT events in 2010 occur in two clusters at of 2.5 to 5 km and less than 1.5 km depths below the summit. An aseismic zone was detected at 1.5-2.5 km depth, consistent with studies of previous eruptions, and indicating that this is a robust feature of Merapi's subsurface structure. Our analysis suggests that the aseismic zone is a poorly consolidated layer of altered material within the volcano. Deep VT events occurred mainly before 17 October 2010; subsequent to that time shallow activity strongly increased. The deep seismic activity is interpreted as associated with the enlargement of a narrow conduit by an unusually large volume of rapidly ascending magma. The shallow seismicity is interpreted as recording the final magma ascent and the rupture of a summit-dome plug, which triggered the eruption on 26 October 2010. Hindsight forecasting of the occurrence time of the eruption is performed

  19. Recent Seismic and Geodetic Activity at Multiple Volcanoes in the Ecuadorean Andes

    NASA Astrophysics Data System (ADS)

    Hernandez, S.; Ruiz, M. C.; McCausland, W. A.; Prejean, S. G.; Mothes, P. A.; Bell, A. F.; Hidalgo, S.; Barrington, C.; Yepez, M.; Aguaiza, S.; Plain, M.

    2015-12-01

    The state of volcanic activity often fluctuates between periods of repose and unrest. The transition time between a period of repose and unrest, or vice versa for an open system, can occur within a matter of hours or days. Because of this short time scale, real-time seismic and geodetic (e.g. tiltmeter, GPS) monitoring networks are crucial for characterizing the state of activity of a volcano. In the Ecuadorean Andes, 5 volcanoes demonstrate long-term (Tungurahua, Reventador, and Guagua Pichincha) or recently reactivated (Cotopaxi, Chiles-Cerro Negro) seismic and geodetic activity. The Instituto Geofisico regularly characterizes volcano seismicity into long period, very long period, volcano-tectonic, and tremor events. Significant recent changes at these volcanoes include: rigorous reactivation of glacier-capped Cotopaxi, drumbeat seismicity absent a dome extrusion at Tungurahua, and regularly reoccurring (~7 day recurrence interval), shallow seismic swarms at Guagua Pichincha. These volcanoes locate along both the Western and Eastern Cordillera of the Ecuadorean Andes and, where data are available, manifest important variations in chemical composition, daily gas flux, and surficial deformation. We summarize the long-term geophysical parameters measured at each volcano and place recent changes in each parameter in a larger magmatic and hydrothermal context. All of the studied volcanoes present significant societal hazards to local and regional communities.

  20. Variations of terrestrial geomagnetic activity correlated to M6+ global seismic activity

    NASA Astrophysics Data System (ADS)

    Cataldi, Gabriele; Cataldi, Daniele; Straser, Valentino

    2013-04-01

    From the surface of the Sun, as a result of a solar flare, are expelled a coronal mass (CME or Coronal Mass Ejection) that can be observed from the Earth through a coronagraph in white light. This ejected material can be compared to an electrically charged cloud (plasma) mainly composed of electrons, protons and other small quantities of heavier elements such as helium, oxygen and iron that run radially from the Sun along the lines of the solar magnetic field and pushing into interplanetary space. Sometimes the CME able to reach the Earth causing major disruptions of its magnetosphere: mashed in the region illuminated by the Sun and expanding in the region not illuminated. This interaction creates extensive disruption of the Earth's geomagnetic field that can be detected by a radio receiver tuned to the ELF band (Extreme Low Frequency 0-30 Hz). The Radio Emissions Project (scientific research project founded in February 2009 by Gabriele Cataldi and Daniele Cataldi), analyzing the change in the Earth's geomagnetic field through an induction magnetometer tuned between 0.001 and 5 Hz (bandwidth in which possible to observe the geomagnetic pulsations) was able to detect the existence of a close relationship between this geomagnetic perturbations and the global seismic activity M6+. During the arrival of the CME on Earth, in the Earth's geomagnetic field are generated sudden and intensive emissions that have a bandwidth including between 0 and 15 Hz, an average duration of 2-8 hours, that preceding of 0-12 hours M6+ earthquakes. Between 1 January 2012 and 31 December 2012, all M6+ earthquakes recorded on a global scale were preceded by this type of signals which, due to their characteristics, have been called "Seismic Geomagnetic Precursors" (S.G.P.). The main feature of Seismic Geomagnetic Precursors is represented by the close relationship that they have with the solar activity. In fact, because the S.G.P. are geomagnetic emissions, their temporal modulation depends

  1. Realistic modeling of seismic input for megacities and large urban areas

    NASA Astrophysics Data System (ADS)

    Panza, G. F.; Unesco/Iugs/Igcp Project 414 Team

    2003-04-01

    The project addressed the problem of pre-disaster orientation: hazard prediction, risk assessment, and hazard mapping, in connection with seismic activity and man-induced vibrations. The definition of realistic seismic input has been obtained from the computation of a wide set of time histories and spectral information, corresponding to possible seismotectonic scenarios for different source and structural models. The innovative modeling technique, that constitutes the common tool to the entire project, takes into account source, propagation and local site effects. This is done using first principles of physics about wave generation and propagation in complex media, and does not require to resort to convolutive approaches, that have been proven to be quite unreliable, mainly when dealing with complex geological structures, the most interesting from the practical point of view. In fact, several techniques that have been proposed to empirically estimate the site effects using observations convolved with theoretically computed signals corresponding to simplified models, supply reliable information about the site response to non-interfering seismic phases. They are not adequate in most of the real cases, when the seismic sequel is formed by several interfering waves. The availability of realistic numerical simulations enables us to reliably estimate the amplification effects even in complex geological structures, exploiting the available geotechnical, lithological, geophysical parameters, topography of the medium, tectonic, historical, palaeoseismological data, and seismotectonic models. The realistic modeling of the ground motion is a very important base of knowledge for the preparation of groundshaking scenarios that represent a valid and economic tool for the seismic microzonation. This knowledge can be very fruitfully used by civil engineers in the design of new seismo-resistant constructions and in the reinforcement of the existing built environment, and, therefore

  2. Revision of the geological context of the Port-au-Prince, Haiti, metropolitan area: implications for seismic microzonation

    NASA Astrophysics Data System (ADS)

    Terrier, M.; Bialkowski, A.; Nachbaur, A.; Prépetit, C.; Joseph, Y. F.

    2014-02-01

    A geological study has been conducted in the framework of the microzonation of Port-au-Prince, Haiti. It reveals the deposit of Miocene and Pliocene formations in a marine environment and the impact on these deposits of the Enriquillo-Plantain Garden N80° E fault system and of N110° E faults. The tectonic and morphological analysis indicates motion during the Quaternary along several mapped reverse left-lateral N110° E faults affecting the capital. Assessing ground-movement hazards represents an integral component of seismic microzonation. The geological results have provided essential groundwork for this assessment. Seismic microzonation aims to take seismic risk more fully into account in the city's urbanization and development policies. To this end, assumptions are made as to risks induced by surface rupture and ground movement from active faults.

  3. High-resolution gravity and seismic-refraction surveys of the Smoke Tree Wash area, Joshua Tree National Park, California

    USGS Publications Warehouse

    Langenheim, Victoria E.; Rymer, Michael J.; Catchings, Rufus D.; Goldman, Mark R.; Watt, Janet T.; Powell, Robert E.; Matti, Jonathan C.

    2016-01-01

    We describe high-resolution gravity and seismic refraction surveys acquired to determine the thickness of valley-fill deposits and to delineate geologic structures that might influence groundwater flow beneath the Smoke Tree Wash area in Joshua Tree National Park. These surveys identified a sedimentary basin that is fault-controlled. A profile across the Smoke Tree Wash fault zone reveals low gravity values and seismic velocities that coincide with a mapped strand of the Smoke Tree Wash fault. Modeling of the gravity data reveals a basin about 2–2.5 km long and 1 km wide that is roughly centered on this mapped strand, and bounded by inferred faults. According to the gravity model the deepest part of the basin is about 270 m, but this area coincides with low velocities that are not characteristic of typical basement complex rocks. Most likely, the density contrast assumed in the inversion is too high or the uncharacteristically low velocities represent highly fractured or weathered basement rocks, or both. A longer seismic profile extending onto basement outcrops would help differentiate which scenario is more accurate. The seismic velocities also determine the depth to water table along the profile to be about 40–60 m, consistent with water levels measured in water wells near the northern end of the profile.

  4. High-resolution marine seismic reflection data from the San Francisco Bay area

    USGS Publications Warehouse

    Childs, Jonathan R.; Hart, Patrick; Bruns, Terry R.; Marlow, Michael S.; Sliter, Ray

    2000-01-01

    Between 1993 and 1997, the U.S. Geological Survey acquired high-resolution, marine seismic-reflection profile data across submerged portions of known and inferred upper crustal fault zones throughout the greater San Francisco Bay area. Surveys were conducted oversouth San Francisco Bay in the vicinity of the San Bruno shoal (roughly between the San Francisco and Oakland airports), over the offshore extension of the San Andreas fault system west of the Golden Gate, over the Hayward fault to Rodgers Creek fault step-over in San Pablo Bay, and over the Kirby Hills fault where it crosses the western Sacramento Delta. Reconnaissance profiles were acquired elsewhere throughout the San Francisco and San Pablo Bays. These data were acquired by the U.S. Geological Survey, Western Coastal and Marine Geology Team, under the auspices of the Central California/San Francisco Bay Earthquake Hazards Project. Analysis and interpretation of some of these profiles has been published by Marlow and others (1996, 1999). Further analysis and interpretation of these data are available in a USGS. Professional Paper Crustal Structure of the Coastal and Marine San Francisco Bay Region, T. Parsons, editor, http://geopubs.wr.usgs.gov/prof-paper/pp1658/ [link added 2012 mfd].

  5. The seismicity in the L'Aquila area (Italy) with particular regard to 1985 earthquake

    NASA Astrophysics Data System (ADS)

    Bernardi, Fabrizio; Grazia Ciaccio, Maria; Palombo, Barbara

    2010-05-01

    We study moderate-magnitude earthquakes (Ml ≥3.5) occurred in the Aquila region recorded by the Istituto Nazionale di Geofisica e Vulcanologia from 1981 to 2009 (CSI, Castello et al., 2006 - http://www.ingv.it/CSI/ ; and ISIDe, http://iside.rm.ingv.it/iside/standard/index.jsp) as well as local temporary seismic networks We identify three major sequences (1985, 1994, 1996) occurring before the 6.th April 2009 Mw=6.3 earthquake. The 1985 earthquake (Ml=4.2) is the larger earthquake occurred in the investigated region till April 2009. The 1994 (Ml=3.9) and 1996 (Ml=4.1) occurred in the Campotosto area (NE to L'Aquila). We computed the source moment tensor using surface waves (Giardini et al., 1993) for the main shocks of the 1985 (Mw=4.7) and 1996 (Mw=4.4) sequences. The solutions show normal fault ruptures. We do not find a reliable solution for the major 1994 sequence earthquake. This suggests, that the magnitude of this event is probably below Mw≈4.2, which is the minimum magnitude threshold for this method.

  6. Seismic hazard assessment in central Ionian Islands area (Greece) based on stress release models

    NASA Astrophysics Data System (ADS)

    Votsi, Irene; Tsaklidis, George; Papadimitriou, Eleftheria

    2011-08-01

    The long-term probabilistic seismic hazard of central Ionian Islands (Greece) is studied through the application of stress release models. In order to identify statistically distinct regions, the study area is divided into two subareas, namely Kefalonia and Lefkada, on the basis of seismotectonic properties. Previous results evidenced the existence of stress transfer and interaction between the Kefalonia and Lefkada fault segments. For the consideration of stress transfer and interaction, the linked stress release model is applied. A new model is proposed, where the hazard rate function in terms of X(t) has the form of the Weibull distribution. The fitted models are evaluated through residual analysis and the best of them is selected through the Akaike information criterion. Based on AIC, the results demonstrate that the simple stress release model fits the Ionian data better than the non-homogeneous Poisson and the Weibull models. Finally, the thinning simulation method is applied in order to produce simulated data and proceed to forecasting.

  7. Anthropogenically-Induced Superficial Seismic Activity Modulated By Slow-Slip Events in Guerrero, Mexico

    NASA Astrophysics Data System (ADS)

    Frank, W.; Shapiro, N.; Husker, A. L.; Kostoglodov, V.; Campillo, M.

    2014-12-01

    We use the data of the MASE seismic experiment operated during 2.5 years in Guerrero, Mexico to create a large catalog of seismic multiplets. This catalog is dominated by families of Low-Frequency Earthquakes (LFE) occurring in vicinity of the main subduction interface. In addition to more than one thousand LFE families, we detected nine repeating seismic event families that are located in the upper crust and are anthropogenically induced (AI) by mining blasts. Analysis of the recurrence of these AI events in time shows that their activity significantly increases during the strong Slow-Slip Event (SSE) in 2006. Modeled static stress perturbations induced by the SSE at the surface are ~5 kPa that is on the same order of magnitude as dynamic stress perturbations observed to trigger other low stress drop phenomena, such as tectonic tremor. We propose therefore that strong SSEs in Guerrero impose an extensional regime throughout the continental crust, modifying the stress field near the surface and increasing AI activity. This modulation of the recurrence of the crustal seismic events by the SSE-induced stress might be related to another recent observation: the SSE-induced reduction of seismic velocities linked to nonlinear elastic effects caused by opening of cracks (Rivet et al., 2011, 2014).

  8. Seismic Surveys Negatively Affect Humpback Whale Singing Activity off Northern Angola

    PubMed Central

    Cerchio, Salvatore; Strindberg, Samantha; Collins, Tim; Bennett, Chanda; Rosenbaum, Howard

    2014-01-01

    Passive acoustic monitoring was used to document the presence of singing humpback whales off the coast of Northern Angola, and opportunistically test for the effect of seismic survey activity in the vicinity on the number of singing whales. Two Marine Autonomous Recording Units (MARUs) were deployed between March and December 2008 in the offshore environment. Song was first heard in mid June and continued through the remaining duration of the study. Seismic survey activity was heard regularly during two separate periods, consistently throughout July and intermittently in mid-October/November. Numbers of singers were counted during the first ten minutes of every hour for the period from 24 May to 1 December, and Generalized Additive Mixed Models (GAMMs) were used to assess the effect of survey day (seasonality), hour (diel variation), moon phase and received levels of seismic survey pulses (measured from a single pulse during each ten-minute sampled period) on singer number. Application of GAMMs indicated significant seasonal variation, which was the most pronounced effect when assessing the full dataset across the entire season (p<0.001); however seasonality almost entirely dropped out of top-ranked models when applied to a reduced dataset during the July period of seismic survey activity. Diel variation was significant in both the full and reduced datasets (from p<0.01 to p<0.05) and often included in the top-ranked models. The number of singers significantly decreased with increasing received level of seismic survey pulses (from p<0.01 to p<0.05); this explanatory variable was included among the top ranked models for one MARU in the full dataset and both MARUs in the reduced dataset. This suggests that the breeding display of humpback whales is disrupted by seismic survey activity, and thus merits further attention and study, and potentially conservation action in the case of sensitive breeding populations. PMID:24618836

  9. Seismic surveys negatively affect humpback whale singing activity off northern Angola.

    PubMed

    Cerchio, Salvatore; Strindberg, Samantha; Collins, Tim; Bennett, Chanda; Rosenbaum, Howard

    2014-01-01

    Passive acoustic monitoring was used to document the presence of singing humpback whales off the coast of Northern Angola, and opportunistically test for the effect of seismic survey activity in the vicinity on the number of singing whales. Two Marine Autonomous Recording Units (MARUs) were deployed between March and December 2008 in the offshore environment. Song was first heard in mid June and continued through the remaining duration of the study. Seismic survey activity was heard regularly during two separate periods, consistently throughout July and intermittently in mid-October/November. Numbers of singers were counted during the first ten minutes of every hour for the period from 24 May to 1 December, and Generalized Additive Mixed Models (GAMMs) were used to assess the effect of survey day (seasonality), hour (diel variation), moon phase and received levels of seismic survey pulses (measured from a single pulse during each ten-minute sampled period) on singer number. Application of GAMMs indicated significant seasonal variation, which was the most pronounced effect when assessing the full dataset across the entire season (p<0.001); however seasonality almost entirely dropped out of top-ranked models when applied to a reduced dataset during the July period of seismic survey activity. Diel variation was significant in both the full and reduced datasets (from p<0.01 to p<0.05) and often included in the top-ranked models. The number of singers significantly decreased with increasing received level of seismic survey pulses (from p<0.01 to p<0.05); this explanatory variable was included among the top ranked models for one MARU in the full dataset and both MARUs in the reduced dataset. This suggests that the breeding display of humpback whales is disrupted by seismic survey activity, and thus merits further attention and study, and potentially conservation action in the case of sensitive breeding populations. PMID:24618836

  10. Noise-based body-wave seismic tomography in an active underground mine.

    NASA Astrophysics Data System (ADS)

    Olivier, G.; Brenguier, F.; Campillo, M.; Lynch, R.; Roux, P.

    2014-12-01

    Over the last decade, ambient noise tomography has become increasingly popular to image the earth's upper crust. The seismic noise recorded in the earth's crust is dominated by surface waves emanating from the interaction of the ocean with the solid earth. These surface waves are low frequency in nature ( < 1 Hz) and not usable for imaging smaller structures associated with mining or oil and gas applications. The seismic noise recorded at higher frequencies are typically from anthropogenic sources, which are short lived, spatially unstable and not well suited for constructing seismic Green's functions between sensors with conventional cross-correlation methods. To examine the use of ambient noise tomography for smaller scale applications, continuous data were recorded for 5 months in an active underground mine in Sweden located more than 1km below surface with 18 high frequency seismic sensors. A wide variety of broadband (10 - 3000 Hz) seismic noise sources are present in an active underground mine ranging from drilling, scraping, trucks, ore crushers and ventilation fans. Some of these sources generate favorable seismic noise, while others are peaked in frequency and not usable. In this presentation, I will show that the noise generated by mining activity can be useful if periods of seismic noise are carefully selected. Although noise sources are not temporally stable and not evenly distributed around the sensor array, good estimates of the seismic Green's functions between sensors can be retrieved for a broad frequency range (20 - 400 Hz) when a selective stacking scheme is used. For frequencies below 100 Hz, the reconstructed Green's functions show clear body-wave arrivals for almost all of the 153 sensor pairs. The arrival times of these body-waves are picked and used to image the local velocity structure. The resulting 3-dimensional image shows a high velocity structure that overlaps with a known ore-body. The material properties of the ore-body differ from

  11. Tomographic image of a seismically active volcano: Mammoth Mountain, California

    USGS Publications Warehouse

    Dawson, Phillip B.; Chouet, Bernard A.; Pitt, Andrew M.

    2016-01-01

    High-resolution tomographic P wave, S wave, and VP/VS velocity structure models are derived for Mammoth Mountain, California, using phase data from the Northern California Seismic Network and a temporary deployment of broadband seismometers. An anomalous volume (5.1 × 109 to 5.9 × 1010m3) of low P and low S wave velocities is imaged beneath Mammoth Mountain, extending from near the surface to a depth of ∼2 km below sea level. We infer that the reduction in seismic wave velocities is due to the presence of CO2 distributed in oblate spheroid pores with mean aspect ratio α = 1.6 × 10−3 to 7.9 × 10−3 (crack-like pores) and mean gas volume fraction ϕ = 8.1 × 10−4 to 3.4 × 10−3. The pore density parameter κ = 3ϕ/(4πα) = na3=0.11, where n is the number of pores per cubic meter and a is the mean pore equatorial radius. The total mass of CO2 is estimated to be 4.6 × 109 to 1.9 × 1011 kg. The local geological structure indicates that the CO2 contained in the pores is delivered to the surface through fractures controlled by faults and remnant foliation of the bedrock beneath Mammoth Mountain. The total volume of CO2 contained in the reservoir suggests that given an emission rate of 500 tons day−1, the reservoir could supply the emission of CO2 for ∼25–1040 years before depletion. Continued supply of CO2 from an underlying magmatic system would significantly prolong the existence of the reservoir.

  12. Tomographic image of a seismically active volcano: Mammoth Mountain, California

    NASA Astrophysics Data System (ADS)

    Dawson, Phillip; Chouet, Bernard; Pitt, Andrew

    2016-01-01

    High-resolution tomographic P wave, S wave, and VP/VS velocity structure models are derived for Mammoth Mountain, California, using phase data from the Northern California Seismic Network and a temporary deployment of broadband seismometers. An anomalous volume (5.1 × 109 to 5.9 × 1010m3) of low P and low S wave velocities is imaged beneath Mammoth Mountain, extending from near the surface to a depth of ˜2 km below sea level. We infer that the reduction in seismic wave velocities is due to the presence of CO2 distributed in oblate spheroid pores with mean aspect ratio α = 1.6 × 10-3 to 7.9 × 10-3 (crack-like pores) and mean gas volume fraction ϕ = 8.1 × 10-4 to 3.4 × 10-3. The pore density parameter κ = 3ϕ/(4πα) = na3=0.11, where n is the number of pores per cubic meter and a is the mean pore equatorial radius. The total mass of CO2 is estimated to be 4.6 × 109 to 1.9 × 1011 kg. The local geological structure indicates that the CO2 contained in the pores is delivered to the surface through fractures controlled by faults and remnant foliation of the bedrock beneath Mammoth Mountain. The total volume of CO2 contained in the reservoir suggests that given an emission rate of 500 tons day-1, the reservoir could supply the emission of CO2 for ˜25-1040 years before depletion. Continued supply of CO2 from an underlying magmatic system would significantly prolong the existence of the reservoir.

  13. Tomographic Image of a Seismically Active Volcano: Mammoth Mountain, California

    NASA Astrophysics Data System (ADS)

    Dawson, P. B.; Chouet, B. A.; Pitt, A. M.

    2015-12-01

    High-resolution tomographic P wave, S wave, and VP /VS velocity structure models are derived for Mammoth Mountain, California using phase data from the Northern California Seismic Network and a temporary deployment of broadband seismometers. An anomalous volume (˜50 km3) of low P and low S wave velocities is imaged beneath Mammoth Mountain, extending from near the surface to a depth of ˜2 km below sea level. We infer that the reduction in seismic wave velocities is primarily due to the presence of CO2 distributed in oblate-spheroid pores with mean aspect ratio α ˜8 x 10-4 (crack-like pores) and gas volume fraction φ ˜4 x 10-4. The pore density parameter κ = 3φ / (4πα) = na3 = 0.12, where n is the number of pores per cubic meter and a is the mean pore equatorial radius. The total mass of CO2 is estimated to range up to ˜1.6 x 1010 kg if the pores exclusively contain CO2, although he presence of an aqueous phase may lower this estimate by up to one order of magnitude. The local geological structure indicates that the CO2 contained in the pores is delivered to the surface through fractures controlled by faults and remnant foliation of the bedrock beneath Mammoth Mountain. The total volume of CO2 contained in the reservoir suggests that given an emission rate of 5 x 105 kg day-1, the reservoir could supply the emission of CO2 for ˜8 to ˜90 years before depletion. Continued supply of CO2 from an underlying magmatic system would significantly prolong the existence of the reservoir.

  14. Differences in the Upper Mantle Structure between 'Hot' and 'Cold' Areas in North America based on USArray Seismic Data along California - Virginia Profile

    NASA Astrophysics Data System (ADS)

    Dec, M.; Sroda, P.; Tesauro, M.; Kaban, M. K.; Perchuc, E.

    2013-12-01

    Nowadays, United States is an area extensively studied by seismic research due to the fact that the EarthScope USArray project provides an unique opportunity to verify previous seismological models and improve our understanding of the upper mantle structure. The data from this experiment are fundamental to study the upper mantle structure because they allow us to present much more detailed analysis. In this study we use the data recorded by the Transportable Array of the USArray and data from the ISC bulletin. We refer also to data from longitudinal Early Rise project while analysing New Madrid Seismic Zone. We use the travel time data from the earthquakes recorded at a distance up to 3500 km in order to image the upper mantle down to about 600 km depth. We present P- and S-wave velocity models for the tectonically stable central part of US and for the active western part. The 1D models are constructed based on the forward modelling of traveltimes from the events located along the California - Virginia profile, for e.g. in California, Colorado or Virginia. This provides a possibility to update the previous MP-1 model (Malinowski et al., 2010). The models were corrected for the crustal effect using the crustal model of Tesauro et al. (2013). All the models have been verified by synthetic seismograms calculated using the reflectivity method. The models show significant differences in the first-arrivals observed at the 800-1800 km epicentral distance range. In the Western, tectonically active region, the 300-km discontinuity is observed. It is interpreted based on the refracted phases with the apparent velocity of 8.9-9.0 km/s and clearly observed reflections. In this area, a low-velocity zone at the bottom of the upper mantle significantly deepens the 410-km discontinuity. The stable North American Craton is characterized by blurred arrivals from the 300-km discontinuity. These 1D models of the upper mantle structure in North America served as a starting point for

  15. Multiple Seismic Array Observations for Tracing Deep Tremor Activity in Western Shikoku, Japan

    NASA Astrophysics Data System (ADS)

    Takeda, T.; Matsuzawa, T.; Shiomi, K.; Obara, K.

    2011-12-01

    Deep non-volcanic tremors become very active during episodic slow-slip events in western Japan and Cascadia. The episodic tremor and slow-slip events in western Shikoku, Japan, occur at a typical interval of 6 months. Recently, it has been reported that tremor migration activity is complex and shows different migrating directions depending on time scales (Ghosh et al., 2010). Such characteristics of tremor are important to understand the mechanism of tremor and the relationship between tremor and SSEs. However it is difficult to determine the location of tremors with high accuracy because tremors show faint signals and make the identification of P/S-wave arrivals difficult. Seismic array analysis is useful to evaluate tremor activity, especially to estimate the arrival direction of seismic energy (e.g. Ueno et al., 2010, Ghosh et al., 2010), as it can distinguish multiple tremor sources occurring simultaneously. Here, we have conducted seismic array observation and analyzed seismic data during tremor activity by applying the MUSIC method to trace tremor location and its migration in western Shikoku. We have installed five seismic arrays in western Shikoku since January 2011. One of the arrays contains 30 stations with 3-component seismometers with a natural frequency of 2 Hz (Type-L array). The array aperture size is 2 km and the mean interval between stations is approximately 200 m. Each of the other arrays (Type-S array) contains 9 seismic stations with the same type of seismometers of the Type-L array, and is deployed surrounding the Type-L array. The small array aperture size is 800 m and its mean station interval is approximately 150 m. All array stations have recorded continuous waveform data at a sampling of 200Hz. In May 2011, an episodic tremor and a short-term slip event occurred for the first time during the observation period. We could retrieve the array seismic data during the whole tremor episode. The analysis of data from the type-L array confirms

  16. Crustal seismic structure beneath the Deccan Traps area (Gujarat, India), from local travel-time tomography

    NASA Astrophysics Data System (ADS)

    Prajapati, Srichand; Kukarina, Ekaterina; Mishra, Santosh

    2016-03-01

    The Gujarat region in western India is known for its intra-plate seismic activity, including the Mw 7.7 Bhuj earthquake, a reverse-faulting event that reactivated normal faults of the Mesozoic Kachchh rift zone. The Late Cretaceous Deccan Traps, one of the largest igneous provinces on the Earth, cover the southern part of Gujarat. This study is aimed at bringing light to the crustal rift zone structure and likely origin of the Traps based on the velocity structure of the crust beneath Gujarat. Tomographic inversion of the Gujarat region was done using the non-linear, passive-source tomographic algorithm, LOTOS. We use high-quality arrival times of 22,280 P and 22,040 S waves from 3555 events recorded from August 2006 to May 2011 at 83 permanent and temporary stations installed in Gujarat state by the Institute of Seismological Research (ISR). We conclude that the resulting high-velocity anomalies, which reach down to the Moho, are most likely related to intrusives associated with the Deccan Traps. Low velocity anomalies are found in sediment-filled Mesozoic rift basins and are related to weakened zones of faults and fracturing. A low-velocity anomaly in the north of the region coincides with the seismogenic zone of the reactivated Kachchh rift system, which is apparently associated with the channel of the outpouring of Deccan basalt.

  17. Robust Satellite Techniques for monitoring earth emitted radiation in the Japanese seismic area by using MTSAT observations in the TIR spectral range

    NASA Astrophysics Data System (ADS)

    Genzano, Nicola; Filizzola, Carolina; Hattori, Katsumi; Lisi, Mariano; Paciello, Rossana; Pergola, Nicola; Tramutoli, Valerio

    2016-04-01

    Since eighties, the fluctuations of Earth's thermally emitted radiation, measured by satellite sensors operating in the thermal infrared (TIR) spectral range, have been associated with the complex process of preparation for major earthquakes. But, like other claimed earthquake precursors (seismological, physical, chemical, biological, etc.) they have been for long-time considered with some caution by scientific community. The lack of a rigorous definition of anomalous TIR signal fluctuations and the scarce attention paid to the possibility that other causes (e.g. meteorological) different from seismic activity could be responsible for the observed TIR variations were the main causes of such skepticism. Compared with previously proposed approaches the general change detection approach, named Robust Satellite Techniques (RST), showed good ability to discriminate anomalous TIR signals possibly associated to seismic activity, from the normal variability of TIR signal due to other causes. Thanks to its full exportability on different satellite packages, since 2001 RST has been implemented on TIR images acquired by polar (e.g. NOAA-AVHRR, EOS -MODIS) and geostationary (e.g. MSG-SEVIRI, NOAA-GOES/W, GMS-5/VISSR) satellite sensors, in order to verify the presence (or absence) of TIR anomalies in presence (absence) of earthquakes (with M>4) in different seismogenic areas around the world (e.g. Italy, Greece, Turkey, India, Taiwan, etc.). In this paper, the RST data analysis approach has been implemented on TIR satellite records collected over Japan by the geostationary satellite sensor MTSAT (Multifunctional Transport SATellites) and RETIRA (Robust Estimator of TIR Anomalies) index was used to identify Significant Sequences of TIR Anomalies (SSTAs) in a possible space-time relations with seismic events. Achieved results will be discussed in the perspective of a multi-parametric approach for a time-Dependent Assessment of Seismic Hazard (t-DASH).

  18. Seismic hydraulic fracture migration originated by successive deep magma pulses: The 2011-2013 seismic series associated to the volcanic activity of El Hierro Island

    NASA Astrophysics Data System (ADS)

    Díaz-Moreno, A.; Ibáñez, J. M.; De Angelis, S.; García-Yeguas, A.; Prudencio, J.; Morales, J.; Tuvè, T.; García, L.

    2015-11-01

    In this manuscript we present a new interpretation of the seismic series that accompanied eruptive activity off the coast of El Hierro, Canary Islands, during 2011-2013. We estimated temporal variations of the Gutenberg-Richter b value throughout the period of analysis, and performed high-precision relocations of the preeruptive and syneruptive seismicity using a realistic 3-D velocity model. Our results suggest that eruptive activity and the accompanying seismicity were caused by repeated injections of magma from the mantle into the lower crust. These magma pulses occurred within a small and well-defined volume resulting in the emplacement of fresh magma along the crust-mantle boundary underneath El Hierro. We analyzed the distribution of earthquake hypocenters in time and space in order to assess seismic diffusivity in the lower crust. Our results suggest that very high earthquake rates underneath El Hierro represent the response of a stable lower crust to stress perturbations with pulsatory character, linked to the injection of magma from the mantle. Magma input from depth caused large stress perturbations to propagate into the lower crust generating energetic seismic swarms. The absence of any preferential alignment in the spatial pattern of seismicity reinforces our hypothesis that stress perturbation and related seismicity, had diffusive character. We conclude that the temporal and spatial evolution of seismicity was neither tracking the path of magma migration nor it defines the boundaries of magma storage volumes such as a midcrustal sill. Our conceptual model considers pulsatory magma injection from the upper mantle and its propagation along the Moho. We suggest, within this framework, that the spatial and temporal distributions of earthquake hypocenters reflect hydraulic fracturing processes associated with stress propagation due to magma movement.

  19. Seismic Response Control Of Structures Using Semi-Active and Passive Variable Stiffness Devices

    NASA Astrophysics Data System (ADS)

    Salem, Mohamed M. A.

    Controllable devices such as Magneto-Rheological Fluid Dampers, Electro-Rheological Dampers, and controllable friction devices have been studied extensively with limited implementation in real structures. Such devices have shown great potential in reducing seismic demands, either as smart base isolation systems, or as smart devices for multistory structures. Although variable stiffness devices can be used for seismic control of structures, the vast majority of research effort has been given to the control of damping. The primary focus of this dissertation is to evaluate the seismic control of structures using semi-active and passive variable stiffness characteristics. Smart base isolation systems employing variable stiffness devices have been studied, and two semi-active control strategies are proposed. The control algorithms were designed to reduce the superstructure and base accelerations of seismically isolated structures subject to near-fault and far-field ground motions. Computational simulations of the proposed control algorithms on the benchmark structure have shown that excessive base displacements associated with the near-fault ground motions may be better mitigated with the use of variable stiffness devices. However, the device properties must be controllable to produce a wide range of stiffness changes for an effective control of the base displacements. The potential of controllable stiffness devices in limiting the base displacement due to near-fault excitation without compromising the performance of conventionally isolated structures, is illustrated. The application of passive variable stiffness devices for seismic response mitigation of multistory structures is also investigated. A stiffening bracing system (SBS) is proposed to replace the conventional bracing systems of braced frames. An optimization process for the SBS parameters has been developed. The main objective of the design process is to maintain a uniform inter-story drift angle over the

  20. Mass movements in fjords caused by seismic activity? A case study from Balsfjord, northern Norway.

    NASA Astrophysics Data System (ADS)

    Forwick, M.; Vorren, T. O.

    2003-04-01

    Fjords can provide excellent opportunities for investigating sedimentary processes related to slope failures. Balsfjord is a 46 km long and maximum 5 km wide fjord in northern Norway, about 10 km south of Tromsø. An end moraine divides the fjord into an Inner and Outer Basin. High-resolution seismic data (3.5 kHz penetration echo sounder), as well as two piston cores, one from each basin, were analysed. The objective of this study was to find submarine deposits that could be used to study the regionality and chronology of postglacial mass-movement activity in northern Norway. Various types of gravity flows were identified, i.e. slumps, debris flows and turbidites. Maximum thickness of one debris flow is c. 15 m. Two marked turbidites have a lateral extent of about 10 km. The origins of some slumps and debris flows include slope failure of the end moraine crossing the fjord, as well as in front of a river mouth. The origin of the turbidites will be studied using grain-size distribution. Three mass-movement events in both basins are correlated using radiocarbon dates. Since these events can be identified in both basins, they are suggested to indicate regional avalanche activity. The three events were bracketed between 9400 radiocarbon years BP and 9100 radiocarbon years BP. This time span fits into the period of most rapid postglacial isostatic uplift in areas adjacent to Balsfjord (Corner and Haugane, 1993). A close correlation between a steep uplift gradient and earthquake frequency/magnitude is suggested by several authors (e.g. Bøe et al., 2001). Thus, seismic activity can be regarded as a potential trigger mechanism for mass-movement activity in Balsfjord. References: Bøe, R., Hovland, M., Instanes, A., Rise, L. and Vasshus, S., 2000. Submarine slide scars and mass movements in Karmsundet and Skudenesfjorden, southwestern Norway: morphology and evolution. Marine Geology, 167(1-2): 147-165. Corner, G.D. and Haugane, E., 1993. Marine-lacustrine stratigraphy of

  1. Structural and Lithologic Characteristics of the Wenchuan Earthquake Fault Zone and its Relationship with Seismic Activity

    NASA Astrophysics Data System (ADS)

    Wang, H.; Li, H.; Pei, J.; Li, T.; Huang, Y.; Zhao, Z.

    2010-12-01

    The Wenchuan earthquake (Ms 8.0) struck the Longmen Shan area, the eastern margin of the Tibetan Plateau in Sichuan, China.It produced a large co-seismic surface rupture zone along the Yingxiu-Beichuan and Guanxian-Anxian fault zones. Our research focuses on the central fault of the Longmuanshan fault belt: the Yingxiu-Beichuan fault zone. Detailed studies were done on the coseismic surface rupture in Bajiaomiao village, Hongkou town. Combining with analyses of the cores from the No.1 Well of the Wenchuan Earthquake Fault Scientific Drilling (WFSD-1) Project, the composition features and structures of the Longmenshan fault belt are discussed. Our research indicates that the Yingxiu-Beichuan fault zone is composed of many small sub-faults (damage zone), which consist of fault breccia, cataclasite and/or fault gouge, and small amounts pseudotachylite in some faults. The thickness of the gouge in the fault zone ranges from several millimeters to 25 centimeters, which is consistent with the fault characteristics recorded in the cores of WFSD-1. Gouge is the product of the frictional effect during the earthquake, representing the principal slip zone (PSZ). The width of the Yingxiu-Beichuan fault zone is about 120 m viewed from outcrops in Bajiaomiao village. More than 80 small sub-faults that contain gouge are distributed in this area. Only several millimeters to approximately 2 centimeters gouge can be formed in one earthquake, from the results of the Taiwan Chelungpu-fault Drilling Project (TCDP) and Wenchuan Earthquake Fault Scientific Drilling (WFSD) Project, so we can infer that each layer of gouge in Yingxiu-Beichuan fault zone might be produced by at least 1 to 13 large earthquakes. The total thickness of the gouge in this area is about 150 cm, indicating at least 183 earthquake events, and suggesting that strong earthquakes repeatedly occurred along the Yingxiu-Beichuan fault zone. Each earthquake does not completely slip along the principal slip zone (PSZ) of

  2. Emergency preparedness activities during an ongoing seismic swarm: the experience of the 2011-2012 Pollino (Southern Italy) sequence

    NASA Astrophysics Data System (ADS)

    Masi, A.; Mucciarelli, M.; Chiauzzi, L.; De Costanzo, G.; Loperte, G.

    2012-04-01

    Facing natural disasters effects can be a very difficult task lacking suitable activities and tools to preventively prepare the involved community (people, authorities, professionals, …) to the expected events. Therefore, a suite of preventive actions should be carried out to mitigate natural risks, in particular working to reduce the territorial vulnerability with respect to the specific natural hazard at hand, and to increase people response capacity. In fact, building social capacity helps to increase the risk perception and the people capacity to adapt to and cope with natural hazards. Since October 2011 a seismic swarm is affecting the Pollino mountain range, Southern Italy. At present the sequence is still ongoing, with more than 500 events with M>1, at least 40 well perceived by the population and a maximum magnitude at 3.6. The area mainly affected by the seismic sequence includes 12 villages, with a total population of about 50.000 inhabitants and, according to the current seismic hazard map it has high seismicity level. Such area was hit by a magnitude Ml=5.7 event in 1998 that produced macroseismic intensity not higher that VII-VIII degree of MCS scale and caused one dead, some injured and widespread damage in at least six municipalities. During the sequence, the National Department of Civil Protection (DPC) and the Civil Protection of Basilicata Region decided to put in action some measures aimed at verifying and enhancing emergency preparedness. These actions have been carried out with a constant and fruitful collaboration among the main stakeholders involved (scientific community, local and national governmental agencies, civil protection volunteers, etc) trough the following main activities: 1. collaboration between scientific community and the local and national offices of Civil Protection especially in the relationship with local authorities (e.g. mayors, which are civil protection authorities in their municipality); 2. interaction between DPC

  3. An Idea for an Active Seismic Experiment on Mars in 2008

    NASA Technical Reports Server (NTRS)

    Lognonne, Ph.; Banerdt, B.; Giardini, D.; Costard, F.

    2001-01-01

    The detection of liquid water is of prime interest and should have deep implications in the understanding of the Martian hydrological cycle and also in exobiology. In the frame of the 2007 joint CNES-NASA mission to Mars, a set of 4 NETLANDERS developed by an European consortium is expected to be launched in June 2007. We propose to use a second spacecraft going or landing to Mars to release near one of the Netlander a series of artificial metallic meteorites, in order to perform an active seismic experiment providing a seismic profile of the crust and subsurface.

  4. Seismic activity before and after the eruption of Kuchinoerabujima in 2015

    NASA Astrophysics Data System (ADS)

    Chiba, K.

    2015-12-01

    Shindake, on Kuchinoerabujima, in the Ryukyu Islands, south of Kyusyu, Japan, erupted at 09:59 JST on 29 May 2015. This eruption is considered to have been a phreato-magmatic eruption, according to the Coordinating Committee for Prediction of Volcanic Eruption in Japan. As characteristic seismic activities before and after the eruption, an A-type event (Mw 2.3) occurred in the northwestern part of Shindake on 23 May, and numerous volcanic events occurred in and around Shindake just after the eruption. The frequency-magnitude distribution (b-value) of earthquakes is commonly high in volcanic areas. It is also known that high b-values in volcanic areas are primarily responsible for material heterogeneity, low shear strength, and high thermal gradients. These facts suggest that the b-value distribution can be used as a tool to locate active magma chambers. It is thus important to determine the distribution of hypocenters precisely and to investigate the b-value distribution on Kuchinoerabujima. We used a data set of the Japan Meteorological Agency and the National Research Institute for Earth Science and Disaster Prevention, and a half-space with Vp = 2.5 km/s as a velocity structure. For the determination of hypocenters, we used the hypomh (Hirata and Matsu'ura 1987) and hypoDD (Waldhauser and Ellsworth 2000) algorithms. This revealed that many estimated hypocenters were distributed in and around the vent at a depth of ~5 km under Shindake before and after the eruption. A volume of high b (>1.2) was locally observed in the eastern part at depths of 1.0-2.5 km below Shindake before the eruption and another was widely observed at depths of 2.0-4.0 km after the eruption. By comparing these findings with other observation results, we may be able to obtain a clear image of the active magma chamber.

  5. Seismic evidence for active underplating below the megathrust earthquake zone in Japan.

    PubMed

    Kimura, Hisanori; Takeda, Tetsuya; Obara, Kazushige; Kasahara, Keiji

    2010-07-01

    Determining the structure of subduction zones is important for understanding mechanisms for the generation of interplate phenomena such as megathrust earthquakes. The peeling off of the uppermost part of a subducting slab and accretion to the bottom of an overlying plate (underplating) at deep regions has been inferred from exhumed metamorphic rocks and deep seismic imaging, but direct seismic evidence of this process is lacking. By comparing seismic reflection profiles with microearthquake distributions in central Japan, we show that repeating microearthquakes occur along the bottom interface of the layer peeling off from the subducting Philippine Sea plate. This region coincides with the location of slow-slip events that may serve as signals for monitoring active underplating. PMID:20616277

  6. Seismic and satellite observations of calving activity at major glacier fronts in Greenland

    NASA Astrophysics Data System (ADS)

    Danesi, Stefania; Salimbeni, Simone; Urbini, Stefano; Pondrelli, Silvia; Margheriti, Lucia

    2016-04-01

    The interaction between oceans and large outlet glaciers in polar regions contributes to the budget of the global water cycle. We have observed the dynamic of sizeable outlet glaciers in Greenland by the analysis of seismic data collected by the regional seismic network Greenland Ice Sheet Monitoring Network (GLISN) trying also to find out correspondence in the glacier tongue evolution derived by the observation of satellite images. By studying the long-period seismic signals at stations located at the mouth of large fjords (e.g. ILULI, NUUG, KULLO), we identify major calving events through the detection of the ground flexure in response to seiche waves generated by iceberg detachments. 
For the time spanning the period between 2010-2014, we fill out calving-event catalogues which can be useful for the estimation of spatial and temporal variations in volume of ice loss at major active fronts in Greenland.

  7. A Predictive Model of Daily Seismic Activity Induced by Mining, Developed with Data Mining Methods

    NASA Astrophysics Data System (ADS)

    Jakubowski, Jacek

    2014-12-01

    The article presents the development and evaluation of a predictive classification model of daily seismic energy emissions induced by longwall mining in sector XVI of the Piast coal mine in Poland. The model uses data on tremor energy, basic characteristics of the longwall face and mined output in this sector over the period from July 1987 to March 2011. The predicted binary variable is the occurrence of a daily sum of tremor seismic energies in a longwall that is greater than or equal to the threshold value of 105 J. Three data mining analytical methods were applied: logistic regression,neural networks, and stochastic gradient boosted trees. The boosted trees model was chosen as the best for the purposes of the prediction. The validation sample results showed its good predictive capability, taking the complex nature of the phenomenon into account. This may indicate the applied model's suitability for a sequential, short-term prediction of mining induced seismic activity.

  8. Tsunami modeling Scenarios for the Western Black Sea, Shabla seismic area

    NASA Astrophysics Data System (ADS)

    Partheniu, Raluca; Diaconescu, Mihai; Ioane, Dumitru; Ionescu, Constantin; Marmureanu, Alexandru

    2015-04-01

    Although a rare natural phenomenon, tsunami type events in the Black Sea had been generated, past studies showing more than twenty events (Altinok Y., 1999). The western Black Sea could mostly be affected by earthquakes generated in Shabla area, the most known event being generated on 31st of March 1901, when an earthquake with Mw = 7.2 triggered tsunami waves up to 5 m height (Papadopoulos et al., 2011). In order to generate a tsunami in the Black Sea area, earthquakes should mainly follow some conditions: a) to have a magnitude Mw > 6.5; b) to have a focal depth h < 40 km and c) to have an inverse or normal fault focal mechanism. A recent earthquake generated in Shabla area on 05.08.2009, at 07:49 UTC, was taken into consideration for running tsunami scenarios. The following parameters were used as initial conditions: earthquake location (Latitude and Longitude) and one plane solution with preset fault parameters (Strike, Dip, Rake, Width, Length). A set of 18 different tsunami modeling scenarios have been run, varying the Magnitude (Mw = 7, 7.5 and 8) and the Depth (5 km, 10 km and 30 km). The software used for generating the tsunami modeling scenarios is Tsunami Analysis Tool (TAT), developed by Joint Research Centre (JRC) of the European Commission. After analyzing and comparing the generated tsunami modeling scenarios, minimum values of magnitude for tsunami waves generation were evaluated for the Shabla seismic source. For some of the scenarios no tsunami waves were generated. The worst case scenario is for a depth of 5 km, a magnitude Mw = 8, the tsunami waves heights reaching 0.8 m in Kranevo (Bulgaria). The maximum wave heights and some of the affected locations for this scenario show that at Costinesti, Mangalia, Techirghiol cities the waves will reach 0.6 m height and respectively 0.5 m at Constanta city. According to these scenarios, the tsunami generated waves can vary as follows: increasing the depth from 5 to 10 and 30 km will lead to lower heights

  9. Seismic wave-speed structure beneath the metropolitan area of Japan based on adjoint tomography

    NASA Astrophysics Data System (ADS)

    Miyoshi, T.; Obayashi, M.; Tono, Y.; Tsuboi, S.

    2015-12-01

    We have obtained a three-dimensional (3D) model of seismic wave-speed structure beneath the metropolitan area of Japan. We applied the spectral-element method (e.g. Komatitsch and Tromp 1999) and adjoint method (Liu and Tromp 2006) to the broadband seismograms in order to infer the 3D model. We used the travel-time tomography result (Matsubara and Obara 2011) as an initial 3D model and used broadband waveforms recorded at the NIED F-net stations. We selected 147 earthquakes with magnitude of larger than 4.5 from the F-net earthquake catalog and used their bandpass filtered seismograms between 5 and 20 second with a high S/N ratio. The 3D model used for the forward and adjoint simulations is represented as a region of approximately 500 by 450 km in horizontal and 120 km in depth. Minimum period of theoretical waveforms was 4.35 second. For the adjoint inversion, we picked up the windows of the body waves from the observed and theoretical seismograms. We used SPECFEM3D_Cartesian code (e.g. Peter et al. 2011) for the forward and adjoint simulations, and their simulations were implemented by K-computer in RIKEN. Each iteration required about 0.1 million CPU hours at least. The model parameters of Vp and Vs were updated by using the steepest descent method. We obtained the fourth iterative model (M04), which reproduced observed waveforms better than the initial model. The shear wave-speed of M04 was significantly smaller than the initial model at any depth. The model of compressional wave-speed was not improved by inversion because of small alpha kernel values. Acknowledgements: This research was partly supported by MEXT Strategic Program for Innovative Research. We thank to the NIED for providing seismological data.

  10. Characterising Seismicity at Alutu, an Actively Deforming Volcano in the Main Ethiopian Rift

    NASA Astrophysics Data System (ADS)

    Wilks, M.; Nowacki, A.; Kendall, J. M.; Wookey, J. M.; Biggs, J.; Bastow, I. D.; Ayele, A.; Bedada, T.

    2013-12-01

    The Main Ethiopian Rift (MER) provides a unique example of the tectonic and volcanic processes occuring during the transition from continental rifting to oceanic spreading. Situated 100 km south of Addis Ababa along the eastern rift margin, Alutu is a silicic stratovolcano that geodetic measurements (InSAR and GPS) have shown is actively deforming. Though the volcano has received relatively little scientific attention it is also a site of economic significance as a geothermal power plant resides within the caldera. As part of ARGOS (Alutu Research Geophysical ObservationS), a multi-disciplinary project aiming to investigate the magmatic and hydrothermal processes occuring at Alutu, a seismic network of 12 broadband seismometers was deployed in January 2012. Other components of ARGOS include InSAR, GPS, geologic mapping and magnetotellurics. From the seismic dataset, P- and S-wave arrivals across the array were manually picked and used to locate events using a non-linear earthquake location algorithm (NonLinLoc) and a predefined 1D velocity model. Perturbations were later applied to this velocity model to investigate the sensitivity of the locations and evaluate the true uncertainties of the solutions. Over 1000 events were successfully located during 2012, where picks were possible at 4 or more stations. Seismicity clusters at both shallow depths (z<2 km) beneath the caldera and at deeper depths of 5-15 km. There is a significant increase in seismicity during the rainy months, suggesting the shallow events may be related to the hydrothermal system. We interpret the deeper events as being magmatic in origin. Events are also located along the eastern border faults that bound the outer edges of the MER and highlights that seismicity arises concurrently via tectonic processes. An adapted version of Richter's original local magnitude scale (ML) to account for attenuation within the MER (Keir et al., 2006) was then used to compute magnitudes for the best located events

  11. Temporal variation of mass-wasting activity in Mount St. Helens crater, Washington, U. S. A. indicated by seismic activity

    SciTech Connect

    Mills, H.H. )

    1991-11-01

    In the crater of Mount St. Helens, formed during the eruption of 18 May 1980, thousands of rockfalls may occur in a single day, and some rock and dirty-snow avalanches have traveled more than 1 km from their source. Because most seismic activity in the crater is produced by mass wasting, the former can be used to monitor the latter. The number and amplitude of seismic events per unit time provide a generalized measure of mass-wasting activity. In this study 1-min averages of seismic amplitudes were used as an index of rockfall activity during summer and early fall. Plots of this index show the diurnal cycle of rockfall activity and establish that the peak in activity occurs in mid to late afternoon. A correlation coefficient of 0.61 was found between daily maximum temperature and average seismic amplitude, although this value increases to 0.72 if a composite temperature variable that includes the maximum temperature of 1 to 3 preceding days as well as the present day is used. Correlation with precipitation is much weaker.

  12. Seismic characterization of the j-reflector near the meizoseismal area of the 1886 Charleston earthquake for lithologic constraint

    NASA Astrophysics Data System (ADS)

    Cunningham, Craig

    Investigations into the relationship between geologic structure and seismicity in and around the meizoseismal area of the 1886 Charleston earthquake have been ongoing since the 1970s. Seismic reflection profiles collected in this area display a prominent, laterally continuous, high amplitude, low frequency, two cycle reflection at ~0.7-1.2 s TWT, termed the "J" reflector, which has been correlated with Lower to Middle Jurassic tholeiitic basalt flows encountered in the Clubhouse Crossroads wells. The "J" reflector was also extended offshore onto the continental shelf. Recent reevaluation of sub Coastal Plain wells within the South Georgia Rift (SGR) Basin, including wells around the meizoseismal area of the 1886 Charleston earthquake, has shown most do not encounter basalt rising suspicions as to the true lithology of the "J"-reflector. Moreover, this same reflector has been interpreted to be the unconformity at the base of the Cretaceous-age Coastal Plain sediments. In order to define the regional extent of the Clubhouse Crossroads basalt, seismic inversion and attribute analysis were performed on two recently acquired reflection profiles, SC02_1 and SC02_5. Beginning in December 2010 through February 2011, seven 2D reflection profiles: SC02_1 - SC02_7 (total length 240 km) were acquired to the immediate west and northwest of the Charleston meizoseismal zone and legacy seismic data as part of DOE Award DE-FE0001965: Geologic Characterization of the South Georgia Rift Basin for Source Proximal C02 Storage project. The first profile, SC02_1, passes Norris Lightsey #1 and Rizer #1, two wells that never encountered basalt at the base of coastal plain. SC02_5, passes Dorchester 211, a well that bottomed into basalt at the base of the coastal plain. Variations in seismic attributes provides evidence for a western termination of the clubhouse crossroads basalt flow on SC02_1 and key support for visible amplitude variations at the contact between coastal plain

  13. Asymmetric active seismicity along the ultra-slow spreading Gakkel Ridge

    NASA Astrophysics Data System (ADS)

    Hopper, John R.; Voss, Peter H.; Lavier, Luc L.

    2015-04-01

    Ultra-slow spreading ridges are frequently characterised by spreading segments that are largely magma starved. Spreading along such segments does not occur by crustal creation/accretion processes such as intrusions, diking and volcanism, but rather by mechanical extension of the lithosphere, exposing the mantle to seafloor where it interacts with seawater to form serpentinite. Such exhumation is thought to occur along detachment faults that form concave down surfaces and produce an extensional geometry that is highly asymmetric. A consequence of all models that have been developed to simulate this type of extension is that stress and strain is focused primarily on the footwall block of the spreading system. This would predict that at any given time, only one side of the system should show active seismicity. In 2001, the Gakkel Ridge was extensively sampled by dredging during the AMORE cruise. These samples showed that the ridge is divided into distinct segments that today are either magmatically robust (only basalts recovered) or magmatically starved (dominantly serpentinised peridotite and gabbros recovered). We extracted earthquake data along the Gakkel Ridge from the global catalogs to investigate if these distinct segments exhibit any differences in active seismicity. We show that the western volcanic zone shows symmetric active seismicity, with earthquakes occurring on both sides of the ridge axis along a relatively restricted region. In contrast, the sparsely magmatic zone shows active seismicity dominantly along along the southern half of the ridge, with comparatively little seismicity to the north. These results are consistent with the proposed models for the formation of amagmatic spreading centers.

  14. Limestones as a paleobathymeter for reconstructing past seismic activities: Muroto-misaki, Shikoku, southwestern Japan

    NASA Astrophysics Data System (ADS)

    Iryu, Y.; Maemoku, H.; Yamada, T.; Maeda, Y.

    2009-03-01

    Muroto-misaki (Cape Muroto) is located at the southern tip of the eastern half of Shikoku, southwestern Japan and is ~ 100 km north of the Nankai Trough where the Philippine Sea Plate is being subducted beneath the Eurasian Plate. Therefore, the Muroto-misaki area has been seismically uplifted. Sedimentologic analyses were conducted on Holocene limestones that occur along the coast from Muroto-misaki to Meoto-iwa, located ~ 13 km north of the cape. The limestones are limited to less than 9.2 m in elevation. The limestones are up to 4.4 m in mean diameter, up to 0.5 m in thickness, and consist mainly of fossilized sessile organisms, including annelids, corals, bryozoans, encrusting foraminifers, barnacles, nongeniculate coralline algae, and, to a lesser extent, molluscs and peyssonneliacean algae. Acicular and equant cements are minor components. Acicular cements are found in semi-closed spaces between coralline algal crusts and their substrates. The modal composition of limestones was determined by a point-counting technique. Based on the biotic composition, the Holocene limestones can be classified into six types (Types I to VI). A comparison of the vertical distribution of these rock types with that of modern sessile organisms indicates that the top of Type I limestone, which is characterized by the occurrence of hermatypic corals, corresponds approximately to the mean low water springs when the limestones formed. A difference in the highest occurrence of Type I limestone between two sites may represent the variation in the total amount of uplift over the last 1000 to 1500 years, which resulted in an apparent northward decline of paleo-mean low water springs at a rate of ~ 10 cm/km. Therefore, the Holocene limestones are a good paleobathymeter to reconstruct past seismic activities in this area. This study shows that warm temperate carbonate deposits are as excellent recorders of geologic events, such as the timing and scale of repeated coseismic uplifts and

  15. Elevated Seismic Activity Beneath the Slumbering Morne aux Diables Volcano, Northern Dominica and the Monitoring Role of the Seismic Research Centre

    NASA Astrophysics Data System (ADS)

    Watts, R. B.; Robertson, R. E.; Abraham, W.; Cole, P.; de Roche, T.; Edwards, S.; Higgins, M.; Johnson, M.; Joseph, E. P.; Latchman, J.; Lynch, L.; Nath, N.; Ramsingh, C.; Stewart, R. C.

    2012-12-01

    Since June 2009, periods of elevated seismic activity have been experienced around the flanks of Morne Aux Diables Volcano in northern Dominica. This long-dormant volcano is a complex of 7 andesitic lava domes with a central depression where a cold soufrière is evident. Prior to this activity, seismicity was very quiet except for a short period in 2000 and an intense short-lived swarm in April 2003. The most recent earthquake activity has been regularly felt by residents in villages on all flanks of the complex. In Dec 09/Jan10, scientists from the Seismic Research Centre (SRC), based in Trinidad & Tobago, in collaboration with staff of the Office of Disaster Management (ODM) and Dominica Public Seismic Network (DPSN) improved the monitoring capacity around this volcano from 1 to 7 seismic stations. Earthquakes are determined to be volcano-tectonic in nature and located at shallow depths (<4 km) beneath the central depression. Additionally, in Jan/Feb 10 geothermal sampling was undertaken and 2 permanent GPS sites were deployed. Public information leaflets prepared by SRC scientists using a "Question & Answer" format have been distributed to concerned citizens whilst many public meetings were carried out by ODM staff. Field investigations indicate that the previous Late Pleistocene activity of Morne Aux Diables switched from Pelèan dome growth and gravitational collapse to more explosive pumice-falls and associated ignimbrites, both styles forming extensive pyroclastic fans around the central complex. The town of Portsmouth is located on one of these fans ~5 km southwest of the central depression. Sporadic, short bursts of seismic activity continue at the time of writing.

  16. The Sasquatch Hydrothermal Field: Linkages Between Seismic Activity, Hydrothermal Flow, and Geology

    NASA Astrophysics Data System (ADS)

    Glickson, D. A.; Kelley, D. S.; Delaney, J. R.

    2006-12-01

    The Sasquatch Hydrothermal Field is the most northern known vent field along the central Endeavour Segment of the Juan de Fuca Ridge, located 6 km north of the Main Endeavour Field (MEF) near 47° 59.8'N, 129° 4.0'W. It was discovered in 2000, after two large earthquake swarms in June 1999 and January 2000 caused increased venting temperatures in the MEF and significant changes in volatile composition along the entire axis [Johnson et al., 2000; Lilley et al., 2003; Proskurowski et al., 2004]. From 2004-2006, Sasquatch and the surrounding axial valley were comprehensively mapped with SM2000 multibeam sonar system and Imagenex scanning sonar at a resolution of 1-5 m. These data were combined with visual imagery from Alvin and ROV dives to define the eruptive, hydrothermal, and tectonic characteristics of the field and distal areas. Based on multibeam sonar results, bathymetric relief of the segment near Sasquatch is subdued. The broad axial valley is split by a central high that rises 30-40 m above the surrounding seafloor. Simple pattern analysis of the valley shows two fundamentally different regions, distinguished by low and high local variance. Areas of low variance correspond to a collapse/drainback landscape characterized by ropy sheet flow, basalt pillars, and bathtub rings capped by intact and drained lobate flows. Areas of high variance generally correspond to three types of ridge structures: 1) faulted basalt ridges composed of truncated pillow basalt, rare massive flows, and widespread pillow talus; 2) constructional basalt ridges composed of intact pillow flow fronts; and 3) extinct sulfide ridges covered by varying amounts of sulfide talus and oxidized hydrothermal sediment. Sasquatch is located in a depression among truncated pillow ridges, and is comprised of ~10, 1-6 m high, fragile sulfide chimneys that vent fluids up to 289°C. The active field extends only ~25 x 25 m, although a linear, N-S trending ridge of nearly continuous extinct sulfide

  17. Seismic structure of southern margin of the 2011 Tohoku-Oki Earthquake aftershocks area: slab-slab contact zone beneath northeastern Kanto, central Japan

    NASA Astrophysics Data System (ADS)

    Kurashimo, E.; Sato, H.; Abe, S.; Mizohata, S.; Hirata, N.

    2011-12-01

    The 2011 Tohoku-Oki Earthquake (Mw9.0) occurred on the Japan Trench off the eastern shore of northern Honshu, Japan. The southward expansion of the afterslip area has reached the Kanto region, central Japan (Ozawa et al., 2011). The Philippine Sea Plate (PHS) subducts beneath the Kanto region. The bottom of the PHS is in contact with the upper surface of the Pacific Plate (PAC) beneath northeastern Kanto. Detailed structure of the PHS-PAC contact zone is important to constrain the southward rupture process of the Tohoku-Oki Earthquake and provide new insight into the process of future earthquake occurrence beneath the Kanto region. Active and passive seismic experiments were conducted to obtain a structural image beneath northeastern Kanto in 2010 (Sato et al., 2010). The geometry of upper surface of the PHS has been revealed by seismic reflection profiling (Sato et al., 2010). Passive seismic data set is useful to obtain a deep structural image. Two passive seismic array observations were conducted to obtain a detailed structure image of the PHS-PAC contact zone beneath northeastern Kanto. One was carried out along a 50-km-long seismic line trending NE-SW (KT-line) and the other was carried out along a 65-km-long seismic line trending NW-SE (TM-line). Sixty-five 3-component portable seismographs were deployed on KT-line with 500 to 700 m interval and waveforms were continuously recorded during a four-month period from June, 2010. Forty-five 3-component portable seismographs were deployed on TM-line with about 1-2 km spacing and waveforms were continuously recorded during the seven-month period from June, 2010. Arrival times of earthquakes were used in a joint inversion for earthquake locations and velocity structure, using the iterative damped least-squares algorithm, simul2000 (Thurber and Eberhart-Phillips, 1999). The relocated hypocenter distribution shows that the seismicity along the upper surface of the PAC is located at depths of 45-75 km beneath

  18. Investigation of the relationships between seismic activities and radon level in western Turkey.

    PubMed

    Tarakçı, M; Harmanşah, C; Saç, M M; İçhedef, M

    2014-01-01

    The distribution of radon activity is determined from pre-earthquake data. Analysis using Normal, Gamma, Weibull and Rayleigh distributions indicates that the variation of radon levels in seismically active regions is best described by a normal distribution. It was observed that radon levels would change in compressive fault lines prior to earthquake. Besides that it tended to increase before the earthquake and then decrease towards the time of earthquake occurrences. PMID:24215813

  19. The contribution of activated processes to Q. [stress corrosion cracking in seismic wave attenuation

    NASA Technical Reports Server (NTRS)

    Spetzler, H. A.; Getting, I. C.; Swanson, P. L.

    1980-01-01

    The possible role of activated processes in seismic attenuation is investigated. In this study, a solid is modeled by a parallel and series configuration of dashpots and springs. The contribution of stress and temperature activated processes to the long term dissipative behavior of this system is analyzed. Data from brittle rock deformation experiments suggest that one such process, stress corrosion cracking, may make a significant contribution to the attenuation factor, Q, especially for long period oscillations under significant tectonic stress.

  20. Analysis of Seismic Activity of the last 15 Years Nearby Puerto Rico and Caribbean Region.

    NASA Astrophysics Data System (ADS)

    Huerta-Lopez, C. I.; Torres-Ortíz, D. M.; Fernández-Heredia, A. I.; Martínez-Cruzado, J. A.

    2015-12-01

    An earthquake catalog of the seismicity occurred during the last 15 years in the Caribbean region, nearby the vicinity of Puerto Rico Island (PRI) was compiled in order to capture the big picture of the regional seismic activity ratio and in particular at the epicentral regions of several historical and instrumentally recorded (during 2008-20015) large to moderate magnitude earthquakes occurred nearby PRI in onshore and offshore, which include the M6.4 earthquake of 01/13/2014, the largest earthquake recorded instrumentally nearby PRI. From the point of view of joint temporal-spatial distribution of epicenters, episodic temporal-spatial seismic activity is clearly seen as temporal-spatial concentrations during certain time intervals in different regions. These localized concentrations of epicenters that occur during certain time intervals in well localized/concentrated regions may suggest "seismic gaps" that shows no regular time interval, neither spatial pattern. In the epicentral region of the M6.4 01/13/2014 earthquake and the historical Mona Passage M7.5 earthquake of 10/11/1918, episodic concentrations in time and space of small magnitude earthquakes epicenters is evident, however do not show temporal pattern. Preliminary results of statistical analysis of an ongoing research in terms of the parameter b (Gutenberg-Richter relationship), and the Omori's law with the aim to relate the tectonic framework of the region (or sub-regions) such as structural heterogeneity stress are here presented/discussed.

  1. Seismic Spatial Autocorrelation as a Technique to Track Changes in the Permafrost Active Layer

    NASA Astrophysics Data System (ADS)

    Abbott, R. E.

    2013-12-01

    We present preliminary results from an effort to continuously track freezing and thawing of the permafrost active layer using a small-aperture seismic array. The 7-element array of three-component posthole seismometers is installed on permafrost at Poker Flat Research Range, near Fairbanks, Alaska. The array is configured in two three-station circles with 75 and 25 meter radii that share a common center station. This configuration is designed to resolve omnidirectional, high-frequency seismic microtremor (i.e. ambient noise). Microtremor is continuously monitored and the data are processed using the spatial autocorrelation (SPAC) method. The resulting SPAC coefficients are then inverted for shear-wave velocity structure versus depth. Thawed active-layer soils have a much slower seismic velocity than frozen soils, allowing us to track the depth and intensity of thawing. Persistent monitoring on a permanent array would allow for a way to investigate year-to-year changes without costly site visits. Results from the seismic array will compared to, and correlated with, other measurement techniques, such as physical probing and remote sensing methods. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  2. Local slope, hillslope length and upslope unstable area as 1st order controls on co-seismic landslide hazard.

    NASA Astrophysics Data System (ADS)

    Milledge, D.; Densmore, A. L.; Petley, D. N.; Bellugi, D. G.; Li, G.

    2015-12-01

    Many communities in mountainous areas have limited access to and/or understanding of co-seismic landslide hazard maps. Furthermore these maps rarely provide the information that a community seeks: Where is safest? How big could the landslide be? Geomorphic intuition suggests that: 1) on the ridges one is less likely to be hit by a landslide than elsewhere in the landscape; 2) hazard increases with the amount of upslope unstable area; 3) longer slopes contain more candidate landslides and are also capable of producing larger landslides thus they constitute a more severe hazard. These observations could help communities in siting infrastructure or making earthquake plans but have not, to our knowledge, been tested against past landslide inventories. Co-seismic landslide models make no attempt to predict landslide size and focus on initiation, ignoring the runout which is critical in the slope length control on hazard. Here we test our intuitive hypotheses using an inventory of co-seismic landslides from the 2008 Wenchuan earthquake. The inventory is mapped from high-resolution remote imagery using an automated algorithm and manual delineation and does not distinguish between source and runout zones. Discretizing the study area into 30 m cells we define landslide hazard as the probability that a cell is within a mapped landslide polygon (p(ls)). We find that p(ls) increases rapidly with increasing slope and upslope area. Locations with low local slope (<10˚) or upslope area (<900 m2/m) have p(ls) less than one third of the areal average. The joint p(ls) conditional on local slope and upslope area identifies long steep slopes as particularly hazardous and ridges (where slope and upslope area are both low) as particularly low hazard. Examining the slope lengths associated with each landslide in the inventory we find that hillslope length sets an upper limit on landslide size but that its influence on the detailed size distribution is more difficult to untangle. Finally

  3. Seismicity and active tectonics in the Alboran Sea, Western Mediterranean: Constraints from an offshore-onshore seismological network and swath bathymetry data

    NASA Astrophysics Data System (ADS)

    Grevemeyer, Ingo; Gràcia, Eulàlia; Villaseñor, Antonio; Leuchters, Wiebke; Watts, Anthony B.

    2015-12-01

    Seismicity and tectonic structure of the Alboran Sea were derived from a large amphibious seismological network deployed in the offshore basins and onshore in Spain and Morocco, an area where the convergence between the African and Eurasian plates causes distributed deformation. Crustal structure derived from local earthquake data suggests that the Alboran Sea is underlain by thinned continental crust with a mean thickness of about 20 km. During the 5 months of offshore network operation, a total of 229 local earthquakes were located within the Alboran Sea and neighboring areas. Earthquakes were generally crustal events, and in the offshore domain, most of them occurred at crustal levels of 2 to 15 km depth. Earthquakes in the Alboran Sea are poorly related to large-scale tectonic features and form a 20 to 40 km wide NNE-SSW trending belt of seismicity between Adra (Spain) and Al Hoceima (Morocco), supporting the case for a major left-lateral shear zone across the Alboran Sea. Such a shear zone is in accord with high-resolution bathymetric data and seismic reflection imaging, indicating a number of small active fault zones, some of which offset the seafloor, rather than supporting a well-defined discrete plate boundary fault. Moreover, a number of large faults known to be active as evidenced from bathymetry, seismic reflection, and paleoseismic data such as the Yusuf and Carboneras faults were seismically inactive. Earthquakes below the Western Alboran Basin occurred at 70 to 110 km depth and hence reflected intermediate depth seismicity related to subducted lithosphere.

  4. Flow Dynamics and Stability of the NE Greenland Ice Stream from Active Seismics and Radar

    NASA Astrophysics Data System (ADS)

    Riverman, K. L.; Alley, R. B.; Anandakrishnan, S.; Christianson, K. A.; Peters, L. E.; Muto, A.

    2015-12-01

    We find that dilatant till facilitates rapid ice flow in central Greenland, and regions of dryer till limit the expansion of ice flow. The Northeast Greenland Ice Stream (NEGIS) is the largest ice stream in Greenland, draining 8.4% of the ice sheet's area. Fast ice flow initiates near the ice sheet summit in a region of high geothermal heat flow and extends some 700km downstream to three outlet glaciers along the NE Coast. The flow pattern and stability mechanism of this ice stream are unique to others in Greenland and Antarctica, and merit further study to ascertain the sensitivity of this ice stream to future climate change. In this study, we present the results of the first-ever ground-based geophysical survey of the initiation zone of NEGIS. Based on radar and preliminary seismic data, Christianson et al. (2014, EPSL) propose a flow mechanism for the ice stream based on topographically driven hydropotential lows which generate 'sticky' regions of the bed under the ice stream margins. We further test this hypothesis using a 40km reflection seismic survey across both ice stream margins. We find that regions of 'sticky' bed as observed by the radar survey are coincident with regions of the bed with seismic returns indicating drier subglacial sediments. These findings are further supported by five amplitude-verses-offset seismic surveys indicating dilatant till within the ice stream and consolidated sediments within its margins.

  5. Active fault segmentation and seismic hazard in Hoa-Binh reservoir, Vietnam

    NASA Astrophysics Data System (ADS)

    Trinh, Phan; Vinh, Hoang; Huong, Nguyen; Liem, Ngo

    2013-06-01

    Based on remote sensing, geological data, geomorphologic analysis, and field observations, we determine the fault system which is a potential source of earthquakes in Hoa-Binh reservoir. It is the sub-meridian fault system composed of fault segments located in the central part of the eastern and western flanks of the Quaternary Hoa-Binh Graben: the Hoa-Binh 1 fault is east-dipping (75-80°), N-S trending, 4 km long, situated in the west of the Hoa-Binh Graben, and the Hoa-Binh 2 is a west-dipping (75-80°), N-S trending; 8.4 km long fault, situated in the east of the Hoa-Binh Graben. The slip rate of normal fault in Hoa-Binh hydropower dam was estimated at 0.3-1.1 mm/yr. The Maximum Credible Earthquake (MCE) and Peak Ground Acceleration (PGA) in the Hoa-Binh hydropower dam have been assessed. The estimated MCE of HB.1 and HB.2 is 5.6 and 6.1 respectively, and the maximum PGA at Hoa-Binh dam is 0.30 g and 0.40 g, respectively. The assessment of seismic hazard in Hoa-Binh reservoir is a typical example of seismic hazards of a large dam constructed in an area of low seismicity and lack of law of seismic attenuation.

  6. Delineating Potential Quick-clay Areas Using High-resolution Seismic Methods: Towards a 3D Model of an Area Prone to Slide in SW Sweden

    NASA Astrophysics Data System (ADS)

    Salas Romero, S.; Malehmir, A.; Snowball, I.

    2015-12-01

    Quick clay can liquefy under increased stress and is responsible for major landslides in Sweden, Norway and Canada, but despite extensive investigations delineating quick clay remains a challenge. As part of a large multidisciplinary project, this study focuses on an area prone to quick-clay landslides in SW Sweden. P- and S-wave seismic, electrical resistivity tomography, and RMT (radio-magnetotelluric) data obtained in 2011 (Malehmir et al. 2013) suggested the presence of a coarse-grained layer of variable thickness sandwiched between clays, with quick clay above. The coarse-grained layer was assumed to accelerate the formation of quick clay, influencing its thickness. Additional geophysical data (reflection and refraction seismic, and RMT) and studies of three boreholes drilled in 2013, with the aim to intersect the coarse-grained layer, extended the area covered in 2011. Here we report on four seismic profiles (total length 3.5 km) acquired in 2013, combined with side-scan and single channel reflection seismic data along a river, which was believed to be important in the context of quick-clay landslides. Wireless (50-1C-10 Hz and 24-3C-broadband) and cabled sensors (323-28 Hz), 4-10 m apart, were used for the data acquisition of the longest profile (nearly 2 km long). Dynamite, accelerated weight-drop and sledgehammer were used as seismic sources. Simultaneous data acquisition for two parallel profiles, about 300 m apart, provides additional information. Preliminary results delineate the bedrock and its undulation near and in the river. We believe that overlying reflections are caused by the coarse-grained materials, whose lateral extension is considerably larger than previously thought. This may imply a wider area containing quick clay and hence at risk of slope failure. The new data and previous results are combined to construct a high-resolution 3D subsurface model that focuses on the coarse-grained layer and potential quick-clay areas. Malehmir A, Bastani M

  7. Seismic time-frequency analysis of the recent 2015 eruptive activity of Volcán de Colima, Mexico

    NASA Astrophysics Data System (ADS)

    Vargas-Bracamontes, D. M.; Nava Pichardo, F. A.; Reyes Dávila, G. A.; Arámbula-Mendoza, R.; Martínez Fierros, A.; Ramírez Vázquez, A.; González Amezcua, M.

    2015-12-01

    Volcán de Colima is an andesitic stratovolcano located in western Mexico. It is considered the most active volcano in Mexico, with activity characterized mainly by intermittent effusive and explosive episodes. On July 10th-12th 2015, Volcán de Colima underwent its most intense eruptive phase since its Plinian eruption in 1913. A partial collapse of the dome and of the crater wall generated several pyroclastic flows, the largest of which reached almost 10 km to the south of the volcano. Lava flows along with incandescent rockfalls descended through various flanks of the volcanic edifice. Ashfall affected people up to 40 km from the volcano's summit. Inhabitants from the small villages closest to the volcano were evacuated and authorities sealed off a 12 km area. We present an overview of the seismic activity that preceded and accompanied this eruptive phase, with data from the closest broadband and short period seismic stations of the Volcán de Colima monitoring network. We focus on the search of temporal information within the spectral content of the seismic signals. We first employ common time-frequency representations such as Fourier and wavelet transforms, but we also apply more recent techniques proposed for the analysis of non-stationary signals, such as empirical mode decomposition and the synchrosqueezing transform. We present and discuss the performances of these various methods characterizing and quantifying spectral changes which could be used to forecast future eruptive events and to evaluate the course of volcanic processes during ongoing eruptions.

  8. Seismic analysis of safety class 1 incinerator glovebox in building 232-Z 200 W Area

    SciTech Connect

    Ocoma, E.C.

    1994-09-01

    This report documents the seismic evaluation for the existing safety class 1 incinerator glovebox in 232Z Building. The glovebox is no longer in use and most of the internal mechanical equipment have been removed. However, the insulation firebricks are still in the glovebox for proper disposal.

  9. High resolution seismic survey of the Hanna, Wyoming underground coal gasification area

    SciTech Connect

    Youngberg, A.D.; Berkman, E.; Orange, A.

    1982-01-01

    In November 1980 a high resolution seismic survey was conducted at the Department of Energy, Laramie Energy Technology Center's underground coal gasification test site near Hanna, Wyoming. The objectives of the survey were to determine the feasibility of utilizing high resolution seismic technology to locate and characterize underground coal burn zones and to identify shallow geologic faults at the test site. Seismic data acquisition and processing parameters were specifically designed to emphasize reflections at the shallow, 61 to 91 meter (200 to 300 foot) depths of interest. A three-dimensional grid of data was obtained over the Hanna II, Phases 2 and 3 burn zone. Processing included time varying filters, deconvolution, trace composition, and two-dimensional, areal stacking of the data in order to identify burn zone anomalies. An anomaly was clearly discernable resulting from the rubble-collapse void above the burn zone which was studied in detail and compared to synthetic models. It is felt, based on these results, that the seismic method can be used to define similar burns if great care is taken in both acquisition and processing phases of an investigation. The fault studies disclosed faults at the test site of hitherto unsuspected complexity. The fault system was found to be a graben complex with numerous antithetic faults. The antithetic faults also contain folded beds. One of the faults discovered may be responsible for the unexpected problems experienced in some of the early in-situ gasification tests at the site. A series of anomalies were discovered on the northeast end of one of the seismic lines, and these reflections have been identified as adits from the old Hanna No. 1 Coal Mine.

  10. Seismicity and eruptive activity at Fuego Volcano, Guatemala: February 1975 -January 1977

    USGS Publications Warehouse

    Yuan, A.T.E.; McNutt, S.R.; Harlow, D.H.

    1984-01-01

    We examine seismic and eruptive activity at Fuego Volcano (14??29???N, 90?? 53???W), a 3800-m-high stratovolcano located in the active volcanic arc of Guatemala. Eruptions at Fuego are typically short-lived vulcanian eruptions producing ash falls and ash flows of high-alumina basalt. From February 1975 to December 1976, five weak ash eruptions occurred, accompanied by small earthquake swarms. Between 0 and 140 (average ??? 10) A-type or high-frequency seismic events per day with M > 0.5 were recorded during this period. Estimated thermal energies for each eruption are greater by a factor of 106 than cumulative seismic energies, a larger ratio than that reported for other volcanoes. Over 4000 A-type events were recorded January 3-7, 1977 (cumulative seismic energy ??? 109 joules), yet no eruption occurred. Five 2-hour-long pulses of intense seismicity separated by 6-hour intervals of quiescence accounted for the majority of events. Maximum likelihood estimates of b-values range from 0.7 ?? 0.2 to 2.1 ?? 0.4 with systematically lower values corresponding to the five intense pulses. The low values suggest higher stress conditions. During the 1977 swarm, a tiltmeter located 6 km southeast of Fuego recorded a 14 ?? 3 microradian tilt event (down to SW). This value is too large to represent a simple change in the elastic strain field due to the earthquake swarm. We speculate that the earthquake swarm and tilt are indicative of subsurface magma movement. ?? 1984.

  11. Locadiff with ambient seismic noise : theoretical background and application to monitoring volcanoes and active faults.

    NASA Astrophysics Data System (ADS)

    Larose, Eric; Obermann, Anne; Planes, Thomas; Rossetto, Vincent; Margerin, Ludovic; Sens-Schoenfelder, Christoph; Campillo, Michel

    2015-04-01

    This contribution will cover recent theoretical, numerical, and field data processing developments aiming at modeling how coda waves are perturbed (in phase and amplitude) by mechanical changes in the crust. Using continuous ambient seismic noise, we cross-correlate data every day and compare the coda of the correlograms. We can relative velocity changes and waveform decorrelation along the year, that are related to mechanical changes in the shallow crust, associated to the seismic or volcanic activity, but also to environmental effects such as hydrology. Bibliography : Anne Obermann, Thomas Planes, Eric Larose and Michel Campillo, Imaging pre- and co-eruptive structural changes of a volcano with ambient seismic noise, J. Geophys. Res. 118 6285-6294 (2013). A. Obermann, B. Froment, M. Campillo, E. Larose, T. Planès, B. Valette, J. H. Chen, and Q. Y. Liu, Seismic noise correlations to image structural and mechanical changes associated with the Mw7.9 2008-Wenchuan earthquake, J. Geophys. Res. Solid Earth, 119, 1-14,(2014). Thomas Planès, Eric Larose, Ludovic Margerin, Vincent Rossetto, Christoph Sens-Schoenfelder, Decorrelation and phase-shift of coda waves induced by local changes : Multiple scattering approach and numerical validation, Waves in Random and Complex Media 24, 99-125, (2014)

  12. Seismicity on the western Greenland Ice Sheet: Surface fracture in the vicinity of active moulins

    SciTech Connect

    Carmichael, Joshua D.; Joughin, Ian; Behn, Mark D.; Das, Sarah; King, Matt A.; Stevens, Laura; Lizarralde, Dan

    2015-06-25

    We analyzed geophone and GPS measurements collected within the ablation zone of the western Greenland Ice Sheet during a ~35 day period of the 2011 melt season to study changes in ice deformation before, during, and after a supraglacial lake drainage event. During rapid lake drainage, ice flow speeds increased to ~400% of winter values, and icequake activity peaked. At times >7 days after drainage, this seismicity developed variability over both diurnal and longer periods (~10 days), while coincident ice speeds fell to ~150% of winter values and showed nightly peaks in spatial variability. Approximately 95% of all detected seismicity in the lake basin and its immediate vicinity was triggered by fracture propagation within near-surface ice (<330 m deep) that generated Rayleigh waves. Icequakes occurring before and during drainage frequently were collocated with the down flow (west) end of the primary hydrofracture through which the lake drained but shifted farther west and outside the lake basin after the drainage. We interpret these results to reveal vertical hydrofracture opening and local uplift during the drainage, followed by enhanced seismicity and ice flow on the downstream side of the lake basin. This region collocates with interferometric synthetic aperture radar-measured speedup in previous years and could reflect the migration path of the meltwater supplied to the bed by the lake. The diurnal seismic signal can be associated with nightly reductions in surface melt input that increase effective basal pressure and traction, thereby promoting elevated strain in the surficial ice.

  13. Seismic activity, inferred crustal stresses and seismotectonics in the Rana region, Northern Norway

    NASA Astrophysics Data System (ADS)

    Hicks, Erik C.; Bungum, Hilmar; Lindholm, Conrad D.

    2000-10-01

    The seismotectonic significance of the Rana region is known both from the fact that this was the location of the largest known earthquake in Fennoscandia in recent times, the MS 5.8-6.2 earthquake of August 31, 1819, and from its relatively high, constant seismic activity also in the 20th century. In order to study this region in more detail, a local seismic network has been in operation there since July 1997, as part of the NEONOR (Neotectonics in Norway) project. The network was primarily designed to detect possible activity on the Båsmoen fault which runs ˜50 km subparallel to the Rana fjord, and which shows signs of likely post glacial activity. The results have revealed a quite complex spatio-temporal distribution of seismic activity, and has also shown no activity on the Båsmoen fault itself. During the first 18 months of operation (July 1997-January 1999), the network has detected 373 locatable seismic events, of which 267 were local earthquakes. Most of these earthquakes occurred in five groups in the western parts of the network. All five groups had similar NNW-ESW trends in epicenter locations, and all have shallow foci (2-12 km), similar to what has also been found earlier for other concentrated earthquake zones in Northern Norway, and the magnitude range is between ML 0.1 and 2.8. Earthquake focal mechanism solutions within the network reveal a predominance for normal faulting with the tensional stress axis perpendicular do the coastline (implying an unusual coast-parallel orientation of the principal horizontal compressive stress). The earthquakes occur in a region of maximum post-glacial uplift gradients, which supports deglaciation flexure as a viable explanation for these earthquakes. A certain influence from more local factors, however, tied in general to crustal in homogeneities, cannot be ruled out.

  14. Occurrence of anomalous seismic activity preceding large to great earthquakes in northeast India region with special reference to 6 August 1988

    NASA Astrophysics Data System (ADS)

    Singh, H. N.; Shanker, D.; Singh, V. P.

    2005-02-01

    Seismicity database from 1860 to 1985 of northeast India region bounded by the area 20°-32°N and 82°-100°E have been analyzed for the identification of precursory swarm/anomalous seismic activity preceding large to great earthquakes with M ≥ 7.5. It is observed that with the exception of three earthquakes (1908, 1912 and 1918), the large earthquakes of 1897, 1946, 1947, 1950 and 1951/1952 were preceded by well-developed epoch of swarm/anomalous seismic activity in space and time well before their occurrence. The seismicity is observed to fluctuate in the order of low-high-low ranging from 0-0.5, 01-33 to 0-0.7 events/year prior to these mainshocks during the epochs of normal/background, swarm/anomalous and gap/quiescence, respectively. The duration of precursory gap is observed to vary from 11 to 17 years for mainshocks of M 7.5-8.0, and from 23 to 27 years for M 8.7 and this period is dependent on the magnitude of the mainshocks. Using the values of magnitude of mainshock ( Mm), average magnitude of swarm ( Mp) and the precursory time gap ( Tp), the following predictive equations are established for the region: M=1.37M-1.40 M=3log⁡T-3.27 All the major earthquakes with mb ≥ 6.1 occurred during 1963-1988 have been investigated for their association with anomalous seismicity/precursory swarms using the events with cutoff magnitude mb ≥ 4.5. Eleven such events have occurred in the region during the period except one earthquake of 29 May 1976. All the remaining 10 earthquakes were associated in some forms of anomalous seismicity epochs. Well-defined patterns of anomalous seismicity are observed prior to 1964-1965, 12 August 1976 and 30 December 1984 ( mb 5.6). All these mainshocks are preceded by seismicity patterns in the order of low-high-low similar to that observed prior to the mainshocks from 1897 to 1962. The anomalous seismicity epoch is delineated with extremely high annual earthquake frequency, which was preceded and followed by extremely low

  15. Fault activation after vigorous eruption: the December 8, 2015 seismic swarm at Mt. Etna

    NASA Astrophysics Data System (ADS)

    Alparone, Salvatore; Bonforte, Alessandro; Guglielmino, Francesco; Maiolino, Vincenza; Puglisi, Giuseppe; Ursino, Andrea

    2016-04-01

    From December 2, 2015, volcanic activity suddenly occurred on Mt. Etna with very violent fire fountaining at central crater, known also as "Voragine". This activity continued with other intense episodes at the same crater during the three following days and involving also, in turn, all the other three summit craters. This sudden eruption produced a rapid deflation of the volcano and was followed, from December 8, by a seismic swarm, with almost eighty earthquakes during this day, located on the uppermost segment of the Pernicana-Provenzana fault system (PFS). This seismicity was characterized by shallow foci (from few hundred meters until 1.5 km below the sea level) and mainshock with 3.6 magnitude. In order to investigate and measure the dynamics controlling and accompanying the PFS activation, a dataset composed of C-Band Sentinel-1A data has been used for SAR Interferometry (InSAR) analysis. Some interferograms have been generated from ascending and descending orbits in order to analyze both short- and long-term deformation. The availability of GPS data allowed comparing and integrating them with InSAR for ground truth and modeling aims. The surface kinematics and modeling obtained by DInSAR and GPS data and integration have been compared to the distribution of the seismicity and related focal mechanisms in order to define the fault geometry and motion. Moreover, essential constraints have been achieved about the PFS dynamic and its relationship with the intense volcanic activity occurred.

  16. Studies of the Correlation Between Ionospheric Anomalies and Seismic Activities in the Indian Subcontinent

    SciTech Connect

    Sasmal, S.; Chakrabarti, S. K.; Chakrabarti, S.

    2010-10-20

    The VLF (Very Low Frequency) signals are long thought to give away important information about the Lithosphere-Ionosphere coupling. It is recently established that the ionosphere may be perturbed due to seismic activities. The effects of this perturbation can be detected through the VLF wave amplitude. There are several methods to find this correlations and these methods can be used for the prediction of these seismic events. In this paper, first we present a brief history of the use of VLF propagation method for the study of seismo-ionospheric correlations. Then we present different methods proposed by us to find out the seismo-ionospheric correlations. At the Indian Centre for Space Physics, Kolkata we have been monitoring the VTX station at Vijayanarayanam from 2002. In the initial stage, we received 17 kHz signal and latter we received 18.2 kHz signal. In this paper, first we present the results for the 17 kHz signal during Sumatra earthquake in 2004 obtained from the terminator time analysis method. Then we present much detailed and statistical analysis using some new methods and present the results for 18.2 kHz signal. In order to establish the correlation between the ionospheric activities and the earthquakes, we need to understand what are the reference signals throughout the year. We present the result of the sunrise and sunset terminators for the 18.2 kHz signal as a function of the day of the year for a period of four years, viz, 2005 to 2008 when the solar activity was very low. In this case, the signal would primarily be affected by the Sun due to normal sunrise and sunset effects. Any deviation from this standardized calibration curve would point to influences by terrestrial (such as earthquakes) and extra-terrestrial (such as solar activities and other high energy phenomena). We present examples of deviations which occur in a period of sixteen months and show that the correlations with seismic events is significant and typically the highest deviation

  17. Geophysical characterization of areas prone to quick-clay landslides using radio-magnetotelluric and seismic methods

    NASA Astrophysics Data System (ADS)

    Wang, Shunguo; Malehmir, Alireza; Bastani, Mehrdad

    2016-05-01

    Landslides attributed to quick clays have not only considerable influences on surface geomorphology, they have caused delays in transportation systems, environmental problems and human fatalities, especially in Scandinavia and North America. If the subsurface distributions of quick clays are known, potential damages can be mitigated and the triggers of landslides can better be studied and understood. For this purpose, new radio-magnetotelluric (RMT) and seismic data were acquired in an area near the Göta River in southwest Sweden that contains quick clays and associated landslides. High-resolution data along 4 new lines, in total 3.8 km long, were acquired and merged with earlier acquired data from the site. Velocity and resistivity models derived from first breaks and RMT data were used to delineate subsurface geology, in particular the bedrock surface and coarse-grained materials that overlay the bedrock. The latter often are found underlying quick clays at the site. Comparably high-resistivity and sometimes high-velocity regions within marine clays are attributed to a combination of leached salt from marine clays or potential quick clays and coarse-grained materials. The resistivity and tomographic velocity models suggest a much larger role of the coarse-grained materials at the site than previously thought, but they also suggest two different scenarios for triggering quick-clay landslides at the site. These scenarios are related to the erosion of the riverbank, increased pore-pressure and surface topography when close to the river and human activity when away from the river and where bowl-shaped bedrock surrounds the sediments.

  18. Diagnosing Non-Meteorically Induced Variations in the Chemistry of Saline Springs of the Vrancea Seismic Area (Romania)

    NASA Astrophysics Data System (ADS)

    Mitrofan, Horia; Marin, Constantin; Tudorache, Alin; Vişan, Mădălina

    2014-09-01

    A monitoring operation conducted over more than seven years has been addressing chemical fluctuations displayed by several cool, low-discharge springs located close to the highly seismic Vrancea area (Romania). Those outflows compositions proved to be strongly controlled by binary, essentially isochemical mixing between a deep-origin brine and meteoric freshwater. By taking advantage of this particular setting, there have been constructed diagrams aimed at investigating how the groundwater-discharges Na-K-Mg geothermometric parameters fluctuated as a function of the chloride content (taken to be an estimator of the freshwater-induced dilution). We made use of the reciprocal algebraic relationships existing between the equations describing the Na-K-Mg geothermometric parameters "Na-K temperature" and "K-Mg temperature" on the one hand, and the so-called "maturity index" (MI) on the other. In an accordingly derived plot of MI against the logarithm of the chloride concentration, a series of data-points being quite uniformly off-set from the MI dilution-curve constructed for an apparently "regular" period, suggested that, episodically, all concerned springwaters were simultaneously subject to some similar changes in the controlling geochemical processes. One such modification intervened 3-4 months before the occurrence of the strongest earthquake () of the hydrochemical monitoring period. The consequently derived interpretation was that then, the numerical values of certain geothermometric coefficients were likely altered: such a process could be consistent with changes in the alkali feldspars solubility relationships, possibly in response to episodic Al-Si complexing which might develop within a hypothesised, still active, exhumation-channel.

  19. A method for producing digital probabilistic seismic landslide hazard maps; an example from the Los Angeles, California, area

    USGS Publications Warehouse

    Jibson, Randall W.; Harp, Edwin L.; Michael, John A.

    1998-01-01

    The 1994 Northridge, California, earthquake is the first earthquake for which we have all of the data sets needed to conduct a rigorous regional analysis of seismic slope instability. These data sets include (1) a comprehensive inventory of triggered landslides, (2) about 200 strong-motion records of the mainshock, (3) 1:24,000-scale geologic mapping of the region, (4) extensive data on engineering properties of geologic units, and (5) high-resolution digital elevation models of the topography. All of these data sets have been digitized and rasterized at 10-m grid spacing in the ARC/INFO GIS platform. Combining these data sets in a dynamic model based on Newmark's permanent-deformation (sliding-block) analysis yields estimates of coseismic landslide displacement in each grid cell from the Northridge earthquake. The modeled displacements are then compared with the digital inventory of landslides triggered by the Northridge earthquake to construct a probability curve relating predicted displacement to probability of failure. This probability function can be applied to predict and map the spatial variability in failure probability in any ground-shaking conditions of interest. We anticipate that this mapping procedure will be used to construct seismic landslide hazard maps that will assist in emergency preparedness planning and in making rational decisions regarding development and construction in areas susceptible to seismic slope failure.

  20. Fault mirrors in seismically active fault zones: A fossil of small earthquakes at shallow depths

    NASA Astrophysics Data System (ADS)

    Kuo, Li-Wei; Song, Sheng-Rong; Suppe, John; Yeh, En-Chao

    2016-03-01

    Fault mirrors (FMs) are naturally polished and glossy fault slip surfaces that can record seismic deformation at shallow depths. They are important for investigating the processes controlling dynamic fault slip. We characterize FMs in borehole samples from the hanging wall damage zone of the active Hsiaotungshi reverse fault, Taiwan. Here we report the first documented occurrence of the combination of silica gel and melt patches coating FMs, with the silica gel resembling those observed on experimentally formed FMs that were cataclastically generated. In addition, the melt patches, which are unambiguous indicators of coseismic slip, suggest that the natural FMs were produced at seismic rates, presumably resulting from flash heating at asperities on the slip surfaces. Since flash heating is efficient at small slip, we propose that these natural FMs represent fossils of small earthquakes, formed in either coseismic faulting and folding or aftershock deformation in the active Taiwan fold-and-thrust belt.

  1. Seismic structure and origin of active intraplate volcanoes in Northeast Asia

    NASA Astrophysics Data System (ADS)

    Duan, Yonghong; Zhao, Dapeng; Zhang, Xiankang; Xia, Shaohong; Liu, Zhi; Wang, Fuyun; Li, Li

    2009-05-01

    Three-dimensional P-wave velocity structure beneath the Changbai and other intraplate volcanic areas in Northeast Asia is determined by inverting 1378 high-quality P-wave arrival times from 186 teleseismic events recorded by 61 broadband seismic stations. Low-velocity (low-V) anomalies are revealed beneath the Changbai, Longgan, Xianjindao volcanoes. High-velocity (high-V) anomalies are found in the mantle transition zone, where deep-focus earthquakes under Hunchun occur at depths of 500-600 km. The high-V anomaly reflects the deep subduction of the Pacific slab under NE Asia which may have contributed to the formation of the Changbai, Longgang, Xianjindao and Jingpohu intraplate volcanoes. A low-V anomaly is also revealed in the mantle transition zone, which may have a close relationship with the occurrence of deep earthquakes under the Hunchun area. Our results support the Big Mantle Wedge (BMW) model by Zhao et al. [Zhao, D., Lei, J., Tang, Y., 2004. Origin of the Changbai volcano in northeast China: evidence from seismic tomography, Chin. Sci. Bull. 49, 1401-1408; Zhao, D., Maruyama, S., Omori, S., 2007. Mantle dynamics of western Pacific and East Asia: insight from seismic tomography and mineral physics. Gondwana Res. 11, 120-131.] who proposed that the intraplate volcanoes in NE Asia are caused by the back-arc magmatism associated with the deep dehydration process of the subducting slab and convective circulation process in the BMW above the stagnant Pacific slab.

  2. First seismic shear wave velocity profile of the lunar crust as extracted from the Apollo 17 active seismic data by wavefield gradient analysis

    NASA Astrophysics Data System (ADS)

    Sollberger, David; Schmelzbach, Cedric; Robertsson, Johan O. A.; Greenhalgh, Stewart A.; Nakamura, Yosio; Khan, Amir

    2016-04-01

    We present a new seismic velocity model of the shallow lunar crust, including, for the first time, shear wave velocity information. So far, the shear wave velocity structure of the lunar near-surface was effectively unconstrained due to the complexity of lunar seismograms. Intense scattering and low attenuation in the lunar crust lead to characteristic long-duration reverberations on the seismograms. The reverberations obscure later arriving shear waves and mode conversions, rendering them impossible to identify and analyze. Additionally, only vertical component data were recorded during the Apollo active seismic experiments, which further compromises the identification of shear waves. We applied a novel processing and analysis technique to the data of the Apollo 17 lunar seismic profiling experiment (LSPE), which involved recording seismic energy generated by several explosive packages on a small areal array of four vertical component geophones. Our approach is based on the analysis of the spatial gradients of the seismic wavefield and yields key parameters such as apparent phase velocity and rotational ground motion as a function of time (depth), which cannot be obtained through conventional seismic data analysis. These new observables significantly enhance the data for interpretation of the recorded seismic wavefield and allow, for example, for the identification of S wave arrivals based on their lower apparent phase velocities and distinct higher amount of generated rotational motion relative to compressional (P-) waves. Using our methodology, we successfully identified pure-mode and mode-converted refracted shear wave arrivals in the complex LSPE data and derived a P- and S-wave velocity model of the shallow lunar crust at the Apollo 17 landing site. The extracted elastic-parameter model supports the current understanding of the lunar near-surface structure, suggesting a thin layer of low-velocity lunar regolith overlying a heavily fractured crust of basaltic

  3. From high quality seismic data acquisition in remote volcanic area to fast data distribution to scientific community: The UnderVolc project on Piton de la Fournaise volcano

    NASA Astrophysics Data System (ADS)

    Brenguier, Florent; Kowalski, Philippe; Pequegnat, Catherine; Lauret, Frédéric; Cougoulat, Glenn; Boissier, Patrice; Catherine, Philippe

    2010-05-01

    Piton de la Fournaise basaltic volcano (La Réunion island, France) is one of the most active volcano in the world with an average of one eruption every year. This volcano is thus an ideal case study for research projects focusing on studying magmatic, seismic and deformation processes occurring in volcanic areas. The UNDERVOLC (UNDERstanding VOLCanic Processes) research project main goal is to provide high quality 3-component broadband continuous seismic data to an amount of about 30 volcano-seismologists from different international research teams (including Japan and New-Zealand). This data acquisition system is moreover dedicated to the monitoring of Piton de la Fournaise volcano by providing real-time seismic data to the Piton de la Fournaise volcanological Observatory/IPGP. The network consists of 21 fully autonomous stations composed of CMG40-T seismometers associated to high dynamic digitizers and linked to wireless digital radio stations. The seismic signal is sent by UDP protocol to the observatory through a network of wireless LAN over large distances (~10 km) and possibly through the internet to the Observatory. The acquisition system at the observatory is composed of: 1-An Earthworm system (USGS - ISTI - CERI) with a Q330 to Earthworm data acquisition module (6 permanent stations from the observatory) 2-An Apollo server system (Nanometrics) for 15 stations (for which seismometers and digitizers belong to the French national pool of portable seismic instruments Sismob, INSU-CNRS) In both case, requests are sent back to the stations in case of loss of udp packets. This system allows us producing miniseed files every hour. Since September 2009, the full dataset has less then 1 % of gaps. In order to provide a fast data access to the scientific community, we synchronize our dataset every night with the SISMOB datacenter located in France (LGIT, Grenoble). After a quality check, seed data volumes are produced and distributed by standard NETDC requests from

  4. Patterns of criticality in the recent seismic activity in the vicinity of Athens, Greece

    NASA Astrophysics Data System (ADS)

    Dologlou, Elizabeth

    2016-04-01

    New data from the Mw 5.4 earthquake on 17 November 2014 in the vicinity of Athens and its seismic electric signal (SES) precursor confirm patterns of criticality in the pre-seismic region during the last preparatory phase. In detail, the stress drop of the main shock and the lead time of the associated SES are interconnected through a power law with an exponent a = 0.327 falling in the range of critical exponents for fracture. We note that this exponent is derived from a large amount of data and successfully passes the z-score statistical test. This fact supports the hypothesis that upon the emission of the SES the pre-focal area enters a critical stage where nonlinear dynamic processes dominate.

  5. Indications for different types of brittle failure due to active coal mining using waveform similarities of induced seismic events

    NASA Astrophysics Data System (ADS)

    Wehling-Benatelli, S.; Becker, D.; Bischoff, M.; Friederich, W.; Meier, T.

    2013-05-01

    Longwall mining activity in the Ruhr-coal mining district leads to mining-induced seismicity. For detailed studies seismicity of a single longwall panel beneath the town of Hamm-Herringen in the eastern Ruhr area was monitored between June 2006 and July 2007 with a dense temporary array of 15 seismic stations. More than 7000 seismic events with magnitudes between -1.7 ≤ ML ≤ 2.0 were detected and localized in this period. Most of the events occurred in the vicinity of the moving longwall face. In order to find possible differences in the brittle failure types of these events an association of the events to distinct clusters based on their waveform characteristics is performed. This task is carried out using a new clustering algorithm utilizing a network similarity matrix which is created by combining all available 3-component single station similarity matrices. The resultant network matrix is then sorted with respect to the similarity of its rows leading to a sorted matrix immediately indicating the clustering of the event catalogue. Finally, clusters of similar events are extracted by visual inspection. This approach results in the identification of several large clusters which are distinct with respect to their spatial and temporal characteristics as well as their frequency magnitude distributions. Comparable clusters are also found with a conventional single linkage approach, however, the new routine seems to be able to associate more events to specific clusters without merging the clusters. The nine largest observed clusters can be tentatively divided into three different groups that indicate different types of brittle failure. The first group consists of the two largest clusters which constitute more than half of all recorded events. Results of a relative relocation using cross correlation data suggest that these events are confined to the extent of the mined out longwall and cluster close to the edges of the active longwall at the depth of active

  6. Indications for different types of brittle failure due to active coal mining using waveform similarities of induced seismic events

    NASA Astrophysics Data System (ADS)

    Wehling-Benatelli, S.; Becker, D.; Bischoff, M.; Friederich, W.; Meier, T.

    2013-10-01

    Longwall mining activity in the Ruhr coal mining district leads to mining-induced seismicity. For detailed studies the seismicity of a single longwall panel beneath the town of Hamm-Herringen in the eastern Ruhr area was monitored between June 2006 and July 2007 with a dense temporary network of 15 seismic stations. More than 7000 seismic events with magnitudes between -1.7 ≤ ML ≤ 2.0 were detected and localized in this period. Most of the events occurred in the vicinity of the moving longwall face. In order to find possible differences in the brittle failure types of these events an association of the events to distinct clusters is performed based on their waveform characteristics. This task is carried out using a new clustering algorithm utilizing a network similarity matrix which is created by combining all available 3-component single station similarity matrices. The resultant network matrix is then sorted with respect to the similarity of its rows leading to a sorted matrix immediately indicating the clustering of the event catalogue. Finally, clusters of similar events are extracted by visual inspection. This approach results in the identification of several large clusters which are distinct with respect to their spatial and temporal characteristics as well as their frequency magnitude distributions. Comparable clusters are also found with a conventional single linkage approach, however, the new routine seems to be able to associate more events to specific clusters without merging the clusters. The nine largest observed clusters can be tentatively divided into three different groups that indicate different types of brittle failure. The first group consists of the two largest clusters which constitute more than half of all recorded events. Results of a relative relocation using cross-correlation data suggest that these events are confined to the extent of the mined out longwall and cluster close to the edges of the active longwall at the depth of active

  7. Precursory Seismic Activity Surrounding the High-Slip Patches of the 2011 Mw9.0 Tohoku-Oki Earthquake

    NASA Astrophysics Data System (ADS)

    Sato, T.; Hiratsuka, S.; Mori, J. J.

    2013-12-01

    The 11 March 2011 Tohoku-Oki earthquake (Mw9.0) occurred on the megathrust along the western margin of the Pacific Ocean where the Pacific plate is being subducted beneath the island of Honshu, Japan. The slip near the Japan Trench was estimated to be enormous; it averaged about 40 m over the upper 100 km of the megathrust and peaked at 60-80 m close to the trench (Lay et al., 2011; Ozawa et al., 2012; Iinuma et al., 2012). Nearly a thousand years are required to accumulate such a large slip for the convergence rate of 8-9 cm/yr along this plate boundary zone. Two days before the Tohoku-Oki earthquake, foreshock activity (largest event M7.3) occurred north of the main-shock epicenter. The epicentral area of the foreshock activity is similar to a M7.0 earthquake in 1981 (Shao et al., 2011). The question arises, why did the 1981 event not trigger a great earthquake? A time difference of 30 years is negligible in comparison with the long time required for the slip deficit of more than 40 m. In order to address this question, we investigated the seismic activity prior to the Tohoku-Oki earthquake using the earthquake catalogue compiled by the Japan Meteorological Agency (JMA) since 1923. For the purpose of the present study, we independently determined the slip distribution of the Tohoku-Oki earthquake, using the coseismic displacements derived from the GEONET GPS stations on land (Ozawa et al., 2011) and those from the offshore GPS stations and ocean-bottom water pressure gauges (Sato et al., 2011; Iinuma et al., 2012). The slip distribution is characterized by two high-slip ( 20m) patches separated by a zone of relatively low slip. The peak of the northern high-slip patch is located near the trench while the peak of the southern high-slip patches are situated about 40 km southeast of the main-shock epicenter, about 70 km away from the trench. Combined with the analyses of main-shock rupture process by Ide et al. (2011) and Shao et al. (2011), it is estimated that the

  8. Offshore active faults of the Mikata fault zone in Fukui, Japan, revealed by high-resolution seismic profiles

    NASA Astrophysics Data System (ADS)

    Inoue, T.; Sugiyama, Y.; Sakamoto, I.; Takino, Y.; Murakami, F.; Hosoya, T.; Usami, T.

    2014-12-01

    The Mikata fault zone are located in coastal and shallow sea area off Fukui Prefecture, West Japan. National Institute of Advanced Industrial Science and Technology (AIST) and Tokai University conducted, as part of MEXT 2013 nearshore active fault survey project, a high-resolution multi-channel seismic survey using Boomer and a 12-channel streamer cable, acoustic profiling survey using parametric sub-bottom profiler and shallow-sea offshore drilling, in order to clarify distribution and activity of the Mikata fault zone. The seismic reflection surveys identified four reflection surfaces as vertical displacement markers in the post-glacial deposits at a depth ranging from ca. 4.5m to ca. 17m below the sea bottom on the downthrown side. We estimated the age of each marker reflection surface by using the C14 age and others from 4m-long core obtained on the downthrown side of fault and the sea level change in the latest Pleistocene and early Holocene around Japan. The results of these surveys have revealed that the fault system was reactivated three times since the latest Pleistocene. The vertical slip rate and average recurrence interval of the fault system are estimated at ca. 0.8-1.0 m/ky and 2,000-3,800 years, respectively.

  9. Exploring a long-lasting volcanic eruption by means of in-soil radon measurements and seismic activity

    NASA Astrophysics Data System (ADS)

    Falsaperla, Susanna; Neri, Marco; Di Grazia, Giuseppe; Langer, Horst; Spampinato, Salvatore

    2016-04-01

    We analyze in-soil radon (Rn) emission and ambient parameters (barometric pressure and air temperature measurements) along with seismic activity during the longest flank eruption of this century at Mt. Etna, Italy. This eruption occurred between 14 May 2008 and 6 July 2009, from a N120-140°E eruptive fissure extending between 3050 and 2620 m above sea level. It was heralded by a short-lived (~5 hours) episode of lava fountaining three days before a dike-forming intrusion fed a lava emission, which affected the summit area of the volcano over ~15 months. The peculiar position of the station for the Rn measurement, which was at an altitude of 2950 m above sea level and near (~1 km) the summit active craters, offered us the uncommon chance: i) to explore the temporal development of the gas emission close (<2 km) to the 2008-2009 eruptive vents in the long term, and ii) to analyze the relationship between in-soil Rn fluxes and seismic signals (in particular, local earthquakes and volcanic tremor) during the uninterrupted lava emission. This approach reveals important details about the recharging phases characterizing the 2008-2009 eruption, which are not visible with other methods of investigation. Our study benefitted from the application of methods of pattern classification developed in the framework of the European MEDiterrranean Supersite Volcanoes (MED­SUV) project.

  10. High-resolution seismic monitoring of rockslide activity in the Illgraben, Switzerland

    NASA Astrophysics Data System (ADS)

    Burtin, Arnaud; Hovius, Niels; Dietze, Michael; McArdell, Brian

    2014-05-01

    Rockfalls and rockslides are important geomorphic processes in landscape dynamics. They contribute to the evolution of slopes and supply rock materials to channels, enabling fluvial incision. Hillslope processes are also a natural hazard that we need to quantify and, if possible, predict. For these reasons, it is necessary to determine the triggering conditions and mechanisms involved in rockfalls. Rainfall is a well-known contributor since water, through soil moisture or pore pressure, may lead to the inception and propagation of cracks and can induce slope failure. Water can also affect slope stability through effects of climatic conditions such as the fluctuations of temperature around the freezing point. During the winter of 2012, we have recorded with a seismic array of 8 instruments substantial rockslide activity that affected a gully in the Illgraben catchment in the Swiss Alps. Three stations were positioned directly around the gully with a nearest distance of 400 m. The period of intense activity did not start during a rainstorm as it is common in summer but during a period of oscillation of temperatures around the freezing point. The activity did not occur in a single event but lasted about a week with a decay in time of the event frequency. Many individual events had two distinct seismic signals, with first, a short duration phase of about 10 s at frequencies below 5 Hz that we interpret as a slope failure signature, followed by a second long duration signal of > 60 s at frequencies above 10 Hz that we attribute to the propagation of rock debris down the slope. Thanks to the array of seismic sensors, we can study the fine details of this rockslide sequence by locating the different events, determining their distribution in time, and systematic quantification of seismic metrics (energy, duration, intensity...). These observations are compared to independent meteorological constrains and laser scan data to obtain an estimate of the volume mobilized by the

  11. Seismic evidence of active strike-slip faulting in the external Gulf of Cadiz (SW Iberian Margin)

    NASA Astrophysics Data System (ADS)

    Bartolome, R.; Gràcia, E.; Stich, D.; Martinez-Loriente, S.; Klaeschen, D.; Masana, E.; Diez, S.; Lo Iacono, C.; Moreno, X.; Zitellini, N.; Manuel, A.; Dañobeitia, J.

    2009-12-01

    The Gulf of Cadiz (GC) hosts the present-day NW-SE plate convergence between Eurasia and Africa Plates west of the Straits of Gibraltar at a rate about 4 mm/yr. The convergence is accommodated over a wide and diffuse deformation zone with moderate magnitude seismic activity. Nevertheless, some of the largest events in Western Europe occurred in the GC, such as the 1755 Lisbon (Mw 8.5) and 1969 Horseshoe (Mw 7.0) earthquakes. Recently published swath-bathymetric compilation in the GC area allowed the identification of several WNW-ESE trending SWIM lineaments (SL), extending over a total length of 600 km. Analogue modelling of topographic features along the SL indicates that the structures are compatible with a dextral strike-slip movement. The concentration of these dextral strike-slip faults along a wide band, the SWIM Fault Zone (SFZ), has been proposed as the present-day EUR-AFR plate boundary. This contribution seeks to: 1) characterizing the active SL seismically; 2) establishing the dextral movement of the SL; 3) identifying new WNW-ESE active dextral strike-slip faults off the SFZ; and 4) providing additional constraints on the tectonics and dynamics of the GC. Two different datasets have been used in this work: 1) 5 multichannel (3 of them pre-stack depth migrated) and ultra-high resolution (parametric sounder TOPAS) seismic profiles, acquired in 2006 within the framework of the SWIM project, and 2) moment tensor inversion of 4 earthquakes (Mw 3.8 to 6.0), ranging from 8 to 50 km depth, from the Spanish IGN catalogue. We present 4 transects of MCS and TOPAS data crossing the SL showing detailed images of the shallow and deep crustal structure. TOPAS images provide evidence of recent activity in a “flower structure” morphology associated with strike-slip faults in the SL. MCS data suggest that the Neogene and Quaternary convergence between African and Eurasian plates has also been absorbed by lateral strike-slip faults going at least up to 10 km depth

  12. Vertical Seismic Profiling at riser drilling site in the rupture area of the 1944 Tonankai Earthquake, Japan (Invited)

    NASA Astrophysics Data System (ADS)

    Hino, R.; Kinoshita, M.; Araki, E.; Byrne, T. B.; McNeill, L. C.; Saffer, D. M.; Eguchi, N. O.; Takahashi, K.; Toczko, S.

    2009-12-01

    A series of scientific drilling expeditions is in operation in the Nankai Trough to reveal the faulting mechanism of the magathrust earthquakes, through clarifying composition, fine structure, mechanical behavior, and environmental variables of the seismogenic faults. In the studied area, extensive seismic surveys for site characterization have been made to image detailed geometry of the fault complex in the accretionary prism as well as Vp distribution around the faults. Although these previous surveys provided invaluable information for understanding seismotectonic processes in this subduction zone, more complete knowledge is needed to be acquired to predict dynamic behavior of the faults, such as geometrical irregularities in short wavelength, Vs and seismic attenuation which are sensitive to fluid distribution in and around fault zones. It is expected that estimation of these parameters would be improved considerably by a seismic exploration using a vertical array of seismographs installed in a deep borehole (VSP: vertical seismic profiling). In July 2009, we made a VSP at one of the drilling sites located just above the rupture area of the 1994 Tonankai Earthquake (M 8.1), during the IODP Exp.319. The well site of our VSP was made by the riser drilling of D/V Chikyu. The seismic array, lowered from Chikyu into the hole, was composed of a three-component accelerometer and vertical separation of the array elements was 15.12 m. The VSP was composed of offset VSP and zero-offset VSP. In the offset VSP, a tuned airgun array towed by R/V Kairei was shot along one straight line (walk-away VSP) and another circular line (walk-around VSP) and seismic signals were recorded by an array consisting of 16 elements installed from 907 to 1,135 m in depth from seafloor. The object of the walk-away VSP is to obtain fine image of the faults using reflection arrivals with less attenuation. It is also expected to obtain spatial variation of Vs from arrival time tomography of

  13. Vernal Point and Seismic Activity in Tibet Mountains and Andes Mountains

    NASA Astrophysics Data System (ADS)

    Chavez-Sumarriva, Israel; Chavez-Campos, Teodosio; Chavez S, Nadia

    2014-05-01

    The gravitational influence of the sun and moon on the equatorial bulges of the mantle of the rotating earth causes the precession of the earth. The retrograde motion of the vernal point through the zodiacal band is 26,000 years and passes through each constellation in an average of 2000 years (Milankovitch subcycle). The vernal point retrogrades one precessional degree approximately in 72 years (Gleissberg-cycle), and approximately enters into the Aquarius constellation (declination 11.5° S) on March 20, 1940. On earth this entry was verify through: a) stability of the magnetic equator in the south central zone of Peru and in the north zone of Bolivia (11.5º South latitude) since 1940 b) the greater intensity of equatorial electrojet (EEJ) in Peru and Bolivia since 1940. Besides, there was a long history of studies of coupling between earthquake-ionosphere. In IUGG (Italy-2007), Cusco was proposed as a prime meridian that was based on: (1) the new prime meridian (72º W == 0º) was parallel to the Andes and its projection the meridian (108° E == 180º) intersects the Tibetan plate (Asia). (2) On earth these two areas present the greatest thickness of the crust with an average depth of 70 kilometers. The aim was to synchronize the earth sciences phenomena (e.g. geology, geophysics, etc.). The coordinate system had the vernal point from meridian (72º W== 0º) and March 20, 1940. The retrograde movement of the vernal point was the first precessional degree (2012 = 1940 + 72). The west coast of South America (parallel to meridian 72º W== 0º) was a segment of the circum-pacific seismic belt where more than two thirds of major earthquakes in the world happened. During the first precessional degree (1940 +72 ==2012) seismic activity were: (a) near the new prime meridian (72° W == 0°) occurs in: (a1) Haiti (18.4° N, 72.5° W), January 12, 2010 with magnitude of 7.0 Mw. (a2) Chile (36.28° S, 73.23° W), February 27, 2010 with Magnitude of 8.8 Mw. (a3) Chile (35

  14. Ion density variation during seismic activity as measured by SROSS-C2 satellite

    NASA Astrophysics Data System (ADS)

    Bardhan, Ananna; Sharma, Dinesh Kumar; Kumar, Sarvesh

    ABSTRACT Ion density (O+ and H+) as a precursory parameter to seismic activity has been analysed from year 1995-1998, using RPA payload aboard SROSS-C2 satellite at an average altitude range of ~ 500 km over the Indian region. The details of seismic events during this period are downloaded from United State Geological Survey (USGS) website. Total of six events from the period of 1995-1998 are analyzed which are free from other perturbing phenomena like solar flares and thunderstorms/ lighting. It has been observed that there is considerable enhancement in average values of heavier ion - O+ density and decrease in lighter ion - H+ ion density during seismic affected time over the normal days. The increase in O+ ion density varies from 1.4 to 8.1 times and decrease in H+ ion density varies from 1.4 to 19.9 times compared to normal day's ion densities respectively. VLF emissions generated due to anomalous electric field during seimogenic activity could plausible candidature of change in ion concentration values during these events.

  15. Peculiarities of ULF electromagnetic disturbances before strong earthquakes in seismic active zone of Kamchatka peninsula

    NASA Astrophysics Data System (ADS)

    Kopytenko, Y. A.; Ismagilov, V. S.; Schekotov, A.; Molchanov, O.; Chebrov, V.; Raspopov, O. M.

    2006-12-01

    Regular observations of ULF electromagnetic disturbances and acoustic emissions at st. Karymshino in seismic active zone of Kamchatka peninsula were carried out during 2001-2003 years. Five seismic active periods with strong earthquakes (M>5) were displayed during this period. These EQs occurred at the Pacific at 20-60 km depth at 100-140 km distances to the East from the st. Karymshino. Analysis of normalized dynamic power spectra of data of high-sensitive (0.2 pT/sqrt(Hz)) three-component induction magnetometer achieved a significant disorder of daily variation and increasing of the magnetic disturbance intensities (from 0.2 to ~1 pT) in the whole investigated frequency range (0.2-5 Hz). The anomaly intensity increasing was observed during the 12-18 hours before main seismic shocks. Maximum of the increasing occurred during 4-6 hours before the EQs. An increasing of acoustic emissions (F=30 Hz) was observed during the same period. A sharp decreasing of the magnetic disturbance intensities was observed 2-4 hours before the EQs. We suppose that physical processes in a hearth of forthcoming EQ lead to an irreversible avalanche-like formation of cracks and stimulation of the acoustic and ULF electromagnetic disturbances.

  16. Forearc oceanic crust in the Izu-Bonin arc - new insights from active-source seismic survey -

    NASA Astrophysics Data System (ADS)

    Kodaira, S.; Noguchi, N.; Takahashi, N.; Ishizuka, O.; Kaneda, Y.

    2009-12-01

    Petrological studies have suggested that oceanic crust is formed in forearc areas during the initial stage of subduction. However, there is little geophysical evidence for the formation of oceanic crust in those regions. In order to examine crustal formation process associated with a subduction initiation process, we conducted an active-source seismic survey at a forearc region in the Izu-Bonin intra-oceanic arc. The resultant seismic image shows a remarkably thin crust (less than 10 km) at the northern half of the Bonin ridge (at the north of the Chichi-jima) and abrupt thickening the crust (~ 20 km thick) toward the south (at the Haha-jima). Comparison of velocity-depth profiles of the thin forearc crust of the Bonin ridge with those of typical oceanic crusts showed them to be seismologically identical. The observed structural variation also well corresponds to magmatic activities along the forearc. Boninitic magmatism is evident in the area of thin crust and tholeiitic-calcalkaline andesitic volcanism in the area of thick crust. Based on high precision dating studies of those volcanic rocks, we interpreted that the oceanic-type thin crust associated with boninitic volcanism has been created soon after the initiation of subduction (45-48 Ma) and and that the nonoceanic thick crust was created by tholeiitic-calcalkaline andesitic magmatism after the boninitic magmatism was ceased. The above seismological evidences strongly support the idea of forearc oceanic crust (or phiolite) created by forearc spreading in the initial stage of subduction along the intra-oceanic arc.

  17. Active fault mapping in Karonga-Malawi after the December 19, 2009 Ms 6.2 seismic event

    NASA Astrophysics Data System (ADS)

    Macheyeki, A. S.; Mdala, H.; Chapola, L. S.; Manhiça, V. J.; Chisambi, J.; Feitio, P.; Ayele, A.; Barongo, J.; Ferdinand, R. W.; Ogubazghi, G.; Goitom, B.; Hlatywayo, J. D.; Kianji, G. K.; Marobhe, I.; Mulowezi, A.; Mutamina, D.; Mwano, J. M.; Shumba, B.; Tumwikirize, I.

    2015-02-01

    The East African Rift System (EARS) has natural hazards - earthquakes, volcanic eruptions, and landslides along the faulted margins, and in response to ground shaking. Strong damaging earthquakes have been occurring in the region along the EARS throughout historical time, example being the 7.4 (Ms) of December 1910. The most recent damaging earthquake is the Karonga earthquake in Malawi, which occurred on 19th December, 2009 with a magnitude of 6.2 (Ms). The earthquake claimed four lives and destroyed over 5000 houses. In its effort to improve seismic hazard assessment in the region, Eastern and Southern Africa Seismological Working Group (ESARSWG) under the sponsorship of the International Program on Physical Sciences (IPPS) carried out a study on active fault mapping in the region. The fieldwork employed geological and geophysical techniques. The geophysical techniques employed are ground magnetic, seismic refraction and resistivity surveys but are reported elsewhere. This article gives findings from geological techniques. The geological techniques aimed primarily at mapping of active faults in the area in order to delineate presence or absence of fault segments. Results show that the Karonga fault (the Karonga fault here referred to as the fault that ruptured to the surface following the 6th-19th December 2009 earthquake events in the Karonga area) is about 9 km long and dominated by dip slip faulting with dextral and insignificant sinistral components and it is made up of 3-4 segments of length 2-3 km. The segments are characterized by both left and right steps. Although field mapping show only 9 km of surface rupture, maximum vertical offset of about 43 cm imply that the surface rupture was in little excess of 14 km that corresponds with Mw = 6.4. We recommend the use or integration of multidisciplinary techniques in order to better understand the fault history, mechanism and other behavior of the fault/s for better urban planning in the area.

  18. Stress-strain sensor for monitoring seismic precursors and fault activities in the sand

    NASA Astrophysics Data System (ADS)

    Du, Qiujiao; Sun, Wei; Zeng, Zuoxun

    2016-04-01

    In this paper, a sensor to monitor stress-strain signals in a granular medium is used to detect seismic precursory information. Compared with the widely used sensors of borehole stress in the rock, the sensor has more convenient operation, higher output sensitivity, compactness and farther propagation effect. The stress and strain changes before Pu'er Ms6.4 earthquake in China are recorded by Beijing and Xinmin stations, and its corresponding fault activities are analyzed. Study indicates anomalous amplitude of strain signal reaches 10 times higher than that of ordinary background, and compressive oscillation and extensional oscillation occurred constantly before the earthquake. The method and results presented in the paper provide a new way for investigating seismic precursors for shallow-source earthquakes.

  19. Crustal root beneath the Rif Cordillera as imaged from both active seismic data and teleseismic receiver functions.

    NASA Astrophysics Data System (ADS)

    Diaz, Jordi; Gil, Alba; Gallart, Josep; Carbonell, Ramon; Harnafi, Mimoun; Levander, Alan

    2015-04-01

    The Rif cordillera forms, together with the Betic ranges, one of the tightest orogenic arcs on Earth. This continental boundary zone is dominated now by the slow convergence between Nubia and Eurasia, but with clear evidences of extensional tectonics. One of the missing elements to constrain the complex geodynamics of the Gibraltar Arc System is the knowledge of the crustal architecture beneath northern Morocco. In the last decade a major effort has been done in this sense, from active and passive seismics. We compile here the recent results available from the Rif domains. Two 330 km long wide angle DSS profiles were recorded end of 2011 across the Rif in NS and EW transects within the Rifsis project, complemented by onshore recordings of the Gassis-WestMed marine profiles. At the same period, BB seismic arrays were deployed in the area within Topo-Iberia and Picasso projects, allowing receiver function analyses of crustal depths. The ray-tracing modeling of the Rifsis profiles reveal a large Moho step and an area of crustal thickening both in EW and NS directions, grossly coincident with the Bouguer gravity anomalies. The deployment logistics allowed that all the stations recorded all the shots, thus providing useful offline data. We will use here all available in-line and offline data to provide a map of the crustal thickness in northern Morocco. We combined two approaches: i) a hyperbolic time reduction applied to the seismic data, resulting in low-fold stacks in which the reflections from the Moho should appear as subhorizontal lines; ii) the arrival times of the observed PmP phases allow, assuming a mean crustal velocity, to assign a midpoint crustal thickness to each lecture. Although some uncertainties may be inherent to those approaches, a large crustal root, reaching more than 50 km, is well documented in the central part of the Rif Cordillera, close to the zone where the Alboran slab may still be attached to the lithosphere. We also compared these results

  20. 4D Time-Lapse Seismic Analysis of Active Gas Seepage Systems on the Vestnesa Ridge, Offshore W-Svalbard

    NASA Astrophysics Data System (ADS)

    Bunz, S.; Hurter, S.; Plaza-Faverola, A. A.; Mienert, J.

    2014-12-01

    Active gas venting occurs on the Vestnesa Ridge, an elongated sediment drift north of the Molloy Transform and just east of the Molloy Ridge, one of the shortest segments of the slow spreading North-Atlantic Ridge system. The crest of the Vestnesa Ridge at water depth between 1200-1300 m is pierced with fluid-flow features. Seafloor pockmarks vary in size up to 1 km in diameter with significant morphological features consisting of small ridges, diapiric structures and small pits. Detailed hydro-acoustic surveying shows that gas mostly emanates from the small-scale pits, where also hydrates have been recovered by sediment sampling. High-resolution P-Cable 3D seismic data acquired in 2012 show vertical focused fluid flow features beneath the seafloor pockmarks. These co-called chimneys extend down to the free-gas zone underneath a bottom-simulating reflection (BSR). Here, they link up with small fault systems that might provide pathways to the deeper subsurface. The chimney features show a high variability in their acoustic characteristics with alternating blanked or masked zones and high-amplitude anomalies scattered through the whole vertical extent of the chimneys. The amplitude anomalies indicate high-impedance contrasts due to the likely presence of gas or a high-velocity material like gas hydrates or carbonates. In most cases, the high-amplitude anomalies line up along specific vertical pathways that connect nicely with the small-scale pits at the surface where gas bubbles seep from the seafloor. We re-acquired the 3D seismic survey in 2013 for time-lapse seismic studies in order to better understand the origin of the amplitude anomalies and in order to track potentially migrating gas fronts up along the chimney structure. The time-lapse seismic analysis indicates several areas, where gas migration may have led to changes in acoustic properties of the subsurface. These areas are located along chimney structures and the BSR. This work provides a basis for better

  1. Managing the Risk of Triggered Seismicity: Can We Identify (and Avoid) Potentially Active Faults? - A Practical Case Study in Oklahoma

    NASA Astrophysics Data System (ADS)

    Zoback, M. D.; Alt, R. C., II; Walsh, F. R.; Walters, R. J.

    2014-12-01

    It is well known that throughout the central and eastern U.S. there has been a marked increase in seismicity since 2009, at least some of which appears to increased wastewater injection. No area has seen a greater increase in seismicity than Oklahoma. In this paper, we utilize newly available information on in situ stress orientation and relative magnitudes, the distribution of high volume injection wells and knowledge of the intervals used for waste water disposal to identify the factors potentially contributing to the occurrence of triggered seismicity. While there are a number of sites where in situ stress data has been successfully used to identify potentially active faults, we are investigating whether this methodology can be implemented throughout a state utilizing the types of information frequently available in areas of oil and gas development. As an initial test of this concept, we have been compiling stress orientation data from wells throughout Oklahoma provided by private industry. Over fifty new high quality data points, principally drilling-induced tensile fractures observed in image logs, result in a greatly improved understanding of the stress field in much of the state. A relatively uniform ENE direction of maximum compressive stress is observed, although stress orientations (and possibly relative stress magnitudes) differ in the southern and southwestern parts of the state. The proposed methodology can be tested in the area of the NE-trending fault that produced the M 5+ earthquakes in the Prague, OK sequence in 2011, and the Meers fault in southwestern OK, that produced a M~7 reverse faulting earthquake about 1100 years ago. This methodology can also be used to essentially rule out slip on other major faults in the area, such as the ~N-S trending Nemaha fault system. Additional factors leading to the occurrence of relatively large triggered earthquakes in Oklahoma are 1) the overall increase in injection volumes throughout the state in recent

  2. Seismic properties of fluid bearing formations in magmatic geothermal systems: can we directly detect geothermal activity with seismic methods?

    NASA Astrophysics Data System (ADS)

    Grab, Melchior; Scott, Samuel; Quintal, Beatriz; Caspari, Eva; Maurer, Hansruedi; Greenhalgh, Stewart

    2016-04-01

    Seismic methods are amongst the most common techniques to explore the earth's subsurface. Seismic properties such as velocities, impedance contrasts and attenuation enable the characterization of the rocks in a geothermal system. The most important goal of geothermal exploration, however, is to describe the enthalpy state of the pore fluids, which act as the main transport medium for the geothermal heat, and to detect permeable structures such as fracture networks, which control the movement of these pore fluids in the subsurface. Since the quantities measured with seismic methods are only indirectly related with the fluid state and the rock permeability, the interpretation of seismic datasets is difficult and usually delivers ambiguous results. To help overcome this problem, we use a numerical modeling tool that quantifies the seismic properties of fractured rock formations that are typically found in magmatic geothermal systems. We incorporate the physics of the pore fluids, ranging from the liquid to the boiling and ultimately vapor state. Furthermore, we consider the hydromechanics of permeable structures at different scales from small cooling joints to large caldera faults as are known to be present in volcanic systems. Our modeling techniques simulate oscillatory compressibility and shear tests and yield the P- and S-wave velocities and attenuation factors of fluid saturated fractured rock volumes. To apply this modeling technique to realistic scenarios, numerous input parameters need to be indentified. The properties of the rock matrix and individual fractures were derived from extensive literature research including a large number of laboratory-based studies. The geometries of fracture networks were provided by structural geologists from their published studies of outcrops. Finally, the physical properties of the pore fluid, ranging from those at ambient pressures and temperatures up to the supercritical conditions, were taken from the fluid physics

  3. Spatial distribution of intrinsic and scattering seismic attenuation in active volcanic islands - I: model and the case of Tenerife Island

    NASA Astrophysics Data System (ADS)

    Prudencio, Janire; Del Pezzo, Edoardo; García-Yeguas, Araceli; Ibáñez, Jesús M.

    2013-12-01

    The complex volcanic system of Tenerife Island is known to have a highly heterogeneous character, as recently confirmed by velocity tomography. We present new information derived from intrinsic quality factor inverse maps (Qi-1), scattering quality factor inverse maps (Qs-1) and total quality factor inverse maps (Qt-1) obtained for the same region. The data set used in this work is the result of the analysis of an active seismic experiment carried out, using offshore shots (air guns) recorded at over 85 onshore seismic stations. The estimates of the attenuation parameters are based on the assumption that the seismogram energy envelopes are determined by seismic energy diffusion processes occurring inside the island. Diffusion model parameters, proportional to Qi-1 and to Qs-1, are estimated from the inversion of the energy envelopes for any source-receiver couple. They are then weighted with a new graphical approach based on a Gaussian space probability function, which allowed us to create `2-D probabilistic maps' representing the space distribution of the attenuation parameters. The 2-D images obtained reveal the existence of a zone in the centre of the island characterized by the lowest attenuation effects. This effect is interpreted as highly rigid and cooled rocks. This low-attenuation region is bordered by zones of high attenuation, associated with the recent historical volcanic activity. We calculate the transport mean free path obtaining a value of around 4 km for the frequency range 6-12 Hz. This result is two orders of magnitude smaller than values calculated for the crust of the Earth. An absorption length between 10 and 14 km is associated with the average intrinsic attenuation parameter. These values, while small in the context of tectonic regions, are greater than those obtained in volcanic regions such as Vesuvius or Merapi. Such differences may be explained by the magnitude of the region of study, over three times larger than the aforementioned study

  4. Seismic Survey Report for Central Nevada Test Area, Subsurface, Correction Action Unit 443, Revision 1

    SciTech Connect

    2008-12-19

    The seismic survey was successful in imaging the water table and underlying structures at the site. The configuration of the water table reflector confirms the general southeast horizontal flow direction in the alluvial aquifer. Offsets in the water table reflector, both at known faults that reach the surface and at subsurface faults not previously recognized, indicate that both extension and blast-related faults are barriers to lateral groundwater flow. The results from this study have been used to optimally locate two new wells designed to monitor head levels and possible contaminant migration in the alluvial aquifer at CTNA.

  5. Seismic design spectra 200 West and East Areas DOE Hanford Site, Washington

    SciTech Connect

    Tallman, A.M.

    1995-12-31

    This document presents equal hazard response spectra for the W236A project for the 200 East and West new high-level waste tanks. The hazard level is based upon WHC-SD-W236A-TI-002, Probabilistic Seismic Hazard Analysis, DOE Hanford Site, Washington. Spectral acceleration amplification is plotted with frequency (Hz) for horizontal and vertical motion and attached to this report. The vertical amplification is based upon the preliminary draft revision of Standard ASCE 4-86. The vertical spectral acceleration is equal to the horizontal at frequencies above 3.3Hz because of near-field, less than 15 km, sources.

  6. 78 FR 28411 - Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-14

    ... Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to Marine Seismic... Marine Seismic Survey in the Chukchi Sea, Alaska AGENCY: National Marine Fisheries Service (NMFS... occur in the seismic survey area include nine cetacean species, beluga whale (Delphinapterus...

  7. Seismic velocity discontinuities in the crust and uppermost mantle beneath the Tokyo metropolitan area inferred from receiver function analysis

    NASA Astrophysics Data System (ADS)

    Igarashi, T.; Sakai, S.; Hirata, N.

    2010-12-01

    We apply receiver function (RF) analyses to estimate the seismic velocity structure and seismic velocity discontinuities in the crust and uppermost mantle beneath the Tokyo metropolitan area, central Japan. Destructive earthquakes often occurred at various places including the subducting Philippine Sea plate (PSP), the subducting Pacific plate (PAP), and inland earthquake in this area. Investigation on the crustal structure and configurations of the subducting plates is the key to understanding the stress and strain concentration process and important to mitigate future earthquake disasters. A RF analysis is widely used to estimate velocity discontinuities in the crust and mantle beneath each seismic station. However, crustal structure beneath the Kanto plain could not be analyzed for lack of applicable seismic stations. Recently, comprehensive surveys are conducted as the Special Project for Earthquake Disaster Mitigation in the Tokyo Metropolitan area from 2007. The Metropolitan Seismic Observation network (MeSO-net) is constructed under this project. In this study, we searched for the best correlated velocity structure model between an observed RF at each station and synthetic ones by using a grid search method. Synthetic RFs calculated from assumed many one-dimensional velocity structures which consisting of four layers. We further constructed the vertical cross-sections of depth converted RF images transformed the lapse time of time series to depth by using the estimated structure models. MeSO-net data and telemetric seismographic network data operated by NIED, JMA and ERI are used. We used events with magnitudes greater or equal to 5.0 and epicentral distances between 30 and 90 degrees based on USGS catalogues. As a result, we clarify spatial distributions of the crustal S-wave velocities. The Boso Peninsula and Kanto plain are covered in the thick low-velocity sediment layers. We image standard velocity distributions in the deep crust of the Boso Peninsula

  8. Deducing the subsurface geological conditions and structural framework of the NE Gulf of Suez area, using 2-D and 3-D seismic data

    NASA Astrophysics Data System (ADS)

    Zahra, Hesham Shaker; Nakhla, Adel Mokhles

    2015-06-01

    An interpretation of the seismic data of Ras Budran and Abu Zenima oil fields, northern central Gulf of Suez, is carried out to evaluate its subsurface tectonic setting. The structural configuration, as well as the tectonic features of the concerned area is criticized through the study of 2D and 3D seismic data interpretation with the available geological data, in which the geo-seismic depth maps for the main interesting levels (Kareem, Nukhul, Matulla, Raha and Nubia Formations) are depicted. Such maps reflect that, the Miocene structure of Ras Budran area is a nearly NE-SW trending anticlinal feature, which broken into several panels by a set of NWSE and NE-SW trending faults. The Pre-Miocene structure of the studied area is very complex, where Ras Budran area consists of step faults down stepping to the south and southwest, which have been subjected to cross faults of NE-SW trend with lateral and vertical displacements.

  9. Earth's magnetic field anomalies that precede the M6+ global seismic activity

    NASA Astrophysics Data System (ADS)

    Cataldi, Gabriele; Cataldi, Daniele; Straser, Valentino

    2014-05-01

    In this work has been analyzed the Earth's magnetic field variations and the M6+ global seismic activity to verify if M6+ earthquakes are preceded by a change of the Earth's magnetic field. The data of Earth's magnetic field used to conduct the study of correlation are provided by the induction magnetometer of Radio Emissions Project's station (Lat: 41°41'4.27"N, Long: 12°38'33,60"E, Albano Laziale, Rome, Italy), equipped with a ELF receiver prototype (with a vertically aligned coil antenna) capable to detect the variations of the intensity of the Earth's magnetic field on Z magnetic component. The M6+ global seismic activity data are provided in real-time by USGS, INGV and CSEM. The sample of data used to conduct the study refers to the period between 1 January 2012 and 31 December 2012. The Earth's magnetic field variations data set has been marked with the times (time markers) of M6+ earthquakes occurred on a global scale and has been verified the existence of disturbances of the Earth's geomagnetic field in the time interval that preceded the M6+ global seismic activity. The correlation study showed that all M6+ earthquakes recorded on 2012 were preceded by an increase of the Earth's magnetic field, detected in the Z magnetic component. The authors measured the time lag elapsed between the maximum increment of the Earth's magnetic field recorded before an earthquake M6+ and the date and time at which this occurred, and has been verified that the minimum time lag recorded between the Earth's magnetic field increase and the earthquake M6+ has been 1 minute (9 October 2012, Balleny Islands, M6,4); while, the maximum time lag recorded has been 3600 minutes (26 June 2012, China, M6,3). The average time lag has been 629.47 minutes. In addition, the average time lag is deflected in relation to the magnitude increase. Key words: Seismic Geomagnetic Precursor (SGP), Interplanetary Seismic Precursor (ISP), Earth's magnetic field variations, earthquakes, prevision.

  10. Reno Area Basin Seismic Response: Ground Motion Simulation in Reno, Nevada

    NASA Astrophysics Data System (ADS)

    Pancha, A.; Louie, J.; Anderson, J. G.

    2002-12-01

    A three-dimensional seismic velocity model is being constructed for the Reno Basin and surrounding region for the purpose of modeling basin effects on the ground motion from potential earthquakes. The model specifies seismic velocities, density, and attenuation on a three dimensional grid (120 km x133 km), down to a depth of 40 km. The background model is based on Western Great Basin geology. Published velocity models and new geophysical data are incorporated to constrain the model. Ground motions from recent earthquakes (Mw4.4 12/02/2000 Truckee event; Mw5.2 08/10/2001 Mohawk Valley) are simulated by a fourth order, 3D staggered grid elastic finite difference code (e3d; Larsen, Schultz, and Grieger), and compared with data recorded by local network and nearby broadband IRIS instruments. These e3d synthetics have an upper frequency limit of 0.3 to 0.6 Hz. 1D synthetic Green's functions, computed in a layered elastic solid using the generalized reflection and transmission coefficients, are also compared to both the real seismogram data and the e3d synthetics. Depending on the station, data are above the noise level at frequencies as low as 0.2 Hz, giving a lower frequency limit for comparison. Success is achieved in matching arrival times. Current work focuses on validating and improving the velocity model.

  11. Integration of Seismic Sequence Analysis and High Resolution Sequence Stratigraphy for Delineating the Sedimentation Characteristics and Modeling of Baltim Area, Off-Shore Nile Delta, Egypt

    NASA Astrophysics Data System (ADS)

    Nasr El-Deen Badawy, A. M. E. S.; Abu El-Ata, A. S. A.; El-Gendy, N. H.

    2014-12-01

    The current study is aiming to discuss the Messinian Prospectivity of the concerned area, which is located in the offshore Nile Delta, about 25 Km from the Mediterranean Sea shoreline. An integrated exploration approach applied, using a variety of the 2D/3D seismic data, subsurface borehole geologic and log data of the selected wells distributed in the study area, as well as the geophysical and biostratigraphic data. The well data comprise well markers, and electric logs, where the geological data represented by litho-stratigraphic information, as well as ditch samples analysis of the studied interval. The geophysical data include check shots, VSP, velocity cubes and 3D seismic lines. Biostratigraphic data include biozones, benthonic to planktonic ratios, nannofossils and foraminiferal data. Seismic interpretation and seismic stratigraphic analysis, in the form of seismic sequence analysis, seismic facies analysis, seismic unit analysis and geologic confirmation have been done by the aid of Petrel and Kingdom computer softwares. The seismic lines were interpreted for defining the different parasequences and picking the various smaller sequences for mapping, after picking each sequence from the seismic correlation, it is facilitated the mapping of every sequence laterally. In addition, the interpretation of structures and isopach of every sequence has been carried out, and the seismic attributes for every sequence were possible, to extract the sands present in each sequence, and to study the extensions of these sands that act as a reservoir. The integration of all results was taken as a base to produce the various models for the study area. The first one was the depositional environmental model, which showed that, the area varies from intertidal-littoral southward at Nidoco wells to inner-middle neritic at Baltim East wells then to outer neritic, and changes to bathyal and then to abyssal at the extreme north. The geologic model for the area was constructed

  12. High-resolution seismic stratigraphy of the late Neogene of the central sector of the Colombian Pacific continental shelf: A seismic expression of an active continental margin

    NASA Astrophysics Data System (ADS)

    Martínez, Jaime Orlando; López Ramos, Eduardo

    2011-02-01

    The sedimentary prism of the central Pacific continental shelf of Colombia was affected by regional folding and faulting, and probably later mud diapirism, from the Late Miocene to the Holocene. Interpretation of high-resolution seismic lines (2 s/dt) revealed that the prism consists of 13 high-resolution seismic units, that can be separated into 5 seismic groups. Deposition of the prism and the associated stacking pattern, are probably the response to variable uplift and subsidence in a fore-arc basin that underwent important tectonic events by the end of the Miocene. Throughout the Pliocene, the continental shelf sedimentation was affected by the growing of a dome structure probable due to mud diapirism. This fact caused peripheral faults both normal and reverse that controlled the distribution of some of the seismic units. During the Late Pleistocene (Wisconsin stage?) a eustatic sea level fall caused the shoreline to advance about 50 km westward of its present position. Because of this eustatic sea level change, a strong fluvial dissection took place and is interpreted as the probable extension of the San Juan River to the south of the present day river mouth. Within this framework it is believed that the Malaga and Buenaventura Bays were the passageways of branches of the old drainage system of the San Juan River. The inner branch circulated through the present Buenaventura Bay and runs southward leaving the mark of an apparent valley identified in the seismic information in the eastern sector of the study area. This old fluvial valley and its filling material located in the present day inner continental shelf front of Buenaventura are postulated as important targets to find placer minerals such as gold and platinum.

  13. Geomorphology, active duplexing, and earthquakes within the Central Himalayan seismic gap

    NASA Astrophysics Data System (ADS)

    Morell, K. D.; Sandiford, M.; Rajendran, C. C.; Rajendran, K.

    2013-12-01

    The ~500 km long 'Central Himalayan seismic gap' of northwest India, is the largest section of the Himalaya that has not experienced a very large earthquake (Mw > 7.0) in the past 200-500 years. The slip deficit associated with this seismic quiescence has led many to suggest that the region is overdue for a great earthquake (Mw >8), an event which could be potentially devastating given the region's high population (>10 million). Despite the recognition that the region is under considerable seismic risk, the geometry of active fault structures that could potentially fail during large earthquakes remains poorly defined. This has arisen, to a certain extent, because moderate earthquakes, such as the Mw 6.3 1999 event near the city of Chamoli and the Mw 7.0 1991 earthquake near Uttarkashi (responsible for ~1000 deaths), have not produced obvious surface ruptures and do not appear to coincide with surficially mapped faults. We present new geomorphic and river longitudinal profile data that define a prominent ~400 km long distinctive geomorphic transition at the base of the high Himalaya in the seismic gap, defined as a sharp dividing line north of which there are significant increases in normalized river steepness (ksn), hillslope angles, and local relief. We interpret the morphologic changes across the geomorphic boundary to be produced due to a northward increase in rock uplift rate, given that the boundary cross-cuts mapped structures and lithologic contacts, yet coincides exactly with: 1) the axial trace of the geophysically-imaged ramp-flat transition in the Main Himalayan Thrust, 2) significant northward increases in instrumentally-recorded seismicity, and 3) an order of magnitude change in published Ar-Ar bedrock cooling ages. The available datasets suggest that such an increase in rock uplift rate is best explained by a ~400 km long by ~50 km wide active duplex along the Main Himalayan Thrust ramp, with the leading edge of the duplex giving rise to the

  14. Temporal Variations of Magnetic Field Associated with Seismic Activity at Cerro Machin Volcano, Colombia

    NASA Astrophysics Data System (ADS)

    Londono, J. M.; Serna, J. P.; Guzman, J.

    2011-12-01

    A study of magnetic variations was carried out at Cerro Machin Volcano, Colombia for the period 2009 -2010, with two permanent magnetometers located at South and North of the central dome, separated about 2.5 km each other. After corrections, we found that there is no clear correlation between volcanic seismicity and temporal changes of magnetic field for each magnetometer station, if they are analyzed individually. On the contrary, when we calculated the residual Magnetic field (RMF), for each magnetometer, and then we made the subtraction between them, and plot it vs time, we found a clear correlation of changes in local magnetic field with the occurrence of volcanic seismicity (ML >1.6). We found a change in the RMF between 1584 nT and 1608 nT, each time that a volcano-tectonic earthquake occurred. The máximum lapse time between the previous change in RMF and the further occurrence of the earthquake is 24 days, with an average of 11 days. This pattern occurred more than 9 times during the studied period. Based on the results, we believed that the simple methodology proposed here, is a good tool for monitoring changes in seismicity associated with activity at Cerro Machín volcano. We suggest that the temporal changes of RMF at Cerro Machín Volcano, are associated with piezo-magnetic effects, due to changes in strain-stress inside the volcano, produced by the interaction between local faulting and magma movement.

  15. Seismic intrusion detector system

    DOEpatents

    Hawk, Hervey L.; Hawley, James G.; Portlock, John M.; Scheibner, James E.

    1976-01-01

    A system for monitoring man-associated seismic movements within a control area including a geophone for generating an electrical signal in response to seismic movement, a bandpass amplifier and threshold detector for eliminating unwanted signals, pulse counting system for counting and storing the number of seismic movements within the area, and a monitoring system operable on command having a variable frequency oscillator generating an audio frequency signal proportional to the number of said seismic movements.

  16. Characterising volcanic activity of Piton de la Fournaise volcano by the spatial distribution of seismic velocity changes

    NASA Astrophysics Data System (ADS)

    Sens-Schoenfelder, C.; Pomponi, E.

    2013-12-01

    We apply Passive Image Interferometry to investigate the seismic noise recorded from October 2009 until December 2011 by 21 stations of the IPGP/OVPF seismic network installed on Piton de la Fournaise volcano within the UnderVolc project. The analyzed period contains three eruptions in 2009 and January 2010, two eruptions plus one dyke intrusion in late 2010, and a seismic crises in 2011. Seismic noise of vertical and horizontal components is cross-correlated to measure velocity changes as apparent stretching of the coda. For some station pairs the apparent velocity changes exceed 1% and a decorrelation of waveforms is observed at the time of volcanic activity. This distorts monitoring results if changes are measured with respect to a global reference. To overcome this we present a method to estimate changes using multiple references that stabilizes the quality of estimated velocity changes. We observe abrupt changes that occur coincident with volcanic events as well as long term transient signals. Using a simple assumption about the spatial sensitivity of our measurements we can map the spatial distribution of velocity changes for selected periods. Comparing these signals with volcanic activity and GPS derived surface deformation we can identify patterns of the velocity changes that appear characteristic for the type of volcanic activity. We can differentiate intrusive processes associated with inflation and increased seismic activity, periods of relaxation without seismicity and eruptions solely based on the velocity signal. This information can help to assess the processes acting in the volcano.

  17. Physical modeling of the formation and evolution of seismically active fault zones

    USGS Publications Warehouse

    Ponomarev, A.V.; Zavyalov, A.D.; Smirnov, V.B.; Lockner, D.A.

    1997-01-01

    Acoustic emission (AE) in rocks is studied as a model of natural seismicity. A special technique for rock loading has been used to help study the processes that control the development of AE during brittle deformation. This technique allows us to extend to hours fault growth which would normally occur very rapidly. In this way, the period of most intense interaction of acoustic events can be studied in detail. Characteristics of the acoustic regime (AR) include the Gutenberg-Richter b-value, spatial distribution of hypocenters with characteristic fractal (correlation) dimension d, Hurst exponent H, and crack concentration parameter Pc. The fractal structure of AR changes with the onset of the drop in differential stress during sample deformation. The change results from the active interaction of microcracks. This transition of the spatial distribution of AE hypocenters is accompanied by a corresponding change in the temporal correlation of events and in the distribution of event amplitudes as signified by a decrease of b-value. The characteristic structure that develops in the low-energy background AE is similar to the sequence of the strongest microfracture events. When the AR fractal structure develops, the variations of d and b are synchronous and d = 3b. This relation which occurs once the fractal structure is formed only holds for average values of d and b. Time variations of d and b are anticorrelated. The degree of temporal correlation of AR has time variations that are similar to d and b variations. The observed variations in laboratory AE experiments are compared with natural seismicity parameters. The close correspondence between laboratory-scale observations and naturally occurring seismicity suggests a possible new approach for understanding the evolution of complex seismicity patterns in nature. ?? 1997 Elsevier Science B.V. All rights reserved.

  18. Decoupling of deformation in the Upper Rhine Graben sediments. Seismic reflection and diffraction on 3-component Vertical Seismic Profiling (Soultz-sous-Forêts area)

    NASA Astrophysics Data System (ADS)

    Place, Joachim; Diraison, Marc; Naville, Charles; Géraud, Yves; Schaming, Marc; Dezayes, Chrystel

    2010-07-01

    A contribution to the definition of the structural pattern of the Soultz-sous-Forêts EGS (Enhanced Geothermal System) is presented here. After reprocessing, the PHN84J seismic reflection profile highlights the tilted blocks of the Merkwiller-Péchelbronn oilfield. In the Soultz-sous-Forêts horst, complex fault patterns are observed: the Hermerswiller normal fault flattens at depth and is rooted in decollements occurring in Triassic salt or clay series, while other steep normal faults affect underlying sedimentary formations and basement. Some methods for the exploitation of a seismic diffraction recorded by multi-component Vertical Seismic Profiling (VSP) are also illustrated to locate the diffractor without specific data processing. Polarisation and travel time analysis of a diffraction event recorded in the GPK1 borehole are analysed, and its exploitation combined with seismic reflection helps defining a tilted block geometry.

  19. Deep Seismic Reflection Profiles Reveal The Crust Structures Beneath Xing'an-Mongolian Orogenic Belt and Its Neighboring Area

    NASA Astrophysics Data System (ADS)

    Hou, H.; Gao, R.; Keller, R. G.; Li, Q.; Li, W.; Li, H.; Xiong, X.; Guo, L.

    2012-12-01

    The Xing'an-Mongolia orogenic belt (XMOB) as the eastern part of the CAOB (Central Asian Orogenic Belt) is one of the remarkably reworked and crustal accretionary belts during the Phanerozoic in the world. It is located between the northern margin of the North China craton and the southern margin of the Siberia craton and is characterized by large-scale Mesozoic magmatism, and forms a key part of the NE-trending Mesozoic magmatic belt in East China. Therefore, it will be of great importance to study the contact relationship between these blocks, which will prodive important information on the study of mineralization and assessment of earthquake disaster. A major problem with all previous publications on Xing'an-Mongolian Orogenic belt was the lack of a seismic section which could potentially image the zone or the dominant vergence of crustal structures at depth. In the view of above, deep seismic profiling data acquisition finished in last three years and the newly processing seismic reflection profiles in this belt were possible under the support of SinoProbe project and China Geological Survey. As we not only focuse on the deep structures of crust, but also carry about the relationships between the shallow reflection fabrics with surface geology. Therefore, different with oil industrial data accquistion, we develop some deep seismic reflection techniques such as three levels of explosive shots were adopted for enough energy reflected from all crust, long offset with single side length of 15 km on symmetrical for the modeling of shallow crust by use of tomographic method, meanwhile we share the shots large than 500 kg with seismic refraction survey line providing more rays for modeling deep velocity strucutre. The seismic reflection data were mainly using the seismic processing package ProMAX and the CGG processing system, following the processing steps with special methods such as tomographic inversion static corrections, surface-consistent amplitude compensation

  20. Melt-Triggered Seismic Response in Hydraulically-Active Polar Ice: Observations and Methods

    NASA Astrophysics Data System (ADS)

    Carmichael, Joshua D.

    occurrence at night relative to that in the day. Contrary to our expectations, we find that the timing of GPS-derived surface speeds do not clearly indicate this seismic activity on any given day. Rather, these icequakes are best explained by peaks in localized strain gradients that develop at night when decreased subglacial water flux likely increases variability in basal traction. Additionally, our results appear comprise the first detailed seismic observations targeted at an actively draining lake. Our last study addresses the apparent deficiency in observed basal icequakes detected from Greenland lake site. To explain the lack of deep icequakes, we compute thresholds on the magnitude of detectable basal events within the network and thereby illustrate that surficial icequakes with similar magnitudes and spectral content are more likely to be observed. By restricting our attention to seismic events that produce lower frequency waveforms, we find a population of nearly monochromatic, sub-1Hz, large magnitude ( M w ≤ 3) seismic events borne from remote glaciogenic sources. In contrast to surficial icequakes, these events occur without significant bias between day and/or night periods and are best explained as glacial earthquakes generated by sliding episodes or iceberg calving events in the vicinity of Jakobshavn Glacier. These events occur daily and not correlate with the presence of local, surficial seismicity. We conclude with three general assertions regarding melt-triggered response characteristics of polar ice. First, hydraulic connections established by fracture events do not necessarily result in seismogenic basal stick slip, and therefore cannot necessarily be observed with conventional GPS monitoring. This was demonstrated at Taylor Glacier. Here, meltwater input to a hydraulic pathway led to fracture growth deep within a cold glacier without any change in surface speed. Second, the presence of melt-triggered basal sliding does not necessarily induce a clear

  1. Structural and thermal control of seismic activity and megathrust rupture dynamics in subduction zones: Lessons from the Mw 9.0, 2011 Tohoku earthquake

    NASA Astrophysics Data System (ADS)

    Satriano, Claudio; Dionicio, Viviana; Miyake, Hiroe; Uchida, Naoki; Vilotte, Jean-Pierre; Bernard, Pascal

    2014-10-01

    The 2011 Tohoku megathrust earthquake ruptured a vast region of the northeast Japan Trench subduction zone in a way that had not been enough anticipated by earthquake and tsunami risk scenarios. We analyzed the Tohoku rupture combining high-frequency back-projection analysis with low frequency kinematic inversion of the co-seismic slip. Results support the to-day well-accepted broadband characteristics of this earthquake. Most of the seismic moment is released during the first 100 s, with large co-seismic slip (up to 55 m) offshore Miyagi in a compact region on the landward side of the trench. Coherent high-frequency radiation areas and relatively low co-seismic slip are a distinctive signature of the slab-mantle interface. The broadband characteristics of the Tohoku rupture are interpreted, integrating the seismic activity and structure information on the NE Japan forearc region, as a signature of along-dip segmentation and segment interactions, that result from thermal structure, plate geometry, material composition and fracture heterogeneities along the plate boundary interface. Deep mantle corner flow and low dehydration rates along the cold subduction slab interface lead to an extended seismogenic slab-mantle interface, with strong bi-material contrast controlling larger propagation distance in the downdip preferred rupture direction. Off Miyagi, plate bending below the mantle wedge, ∼142.3°E at ∼25 km depth, is associated with the eastern limit of the deep M7-8-class thrust-earthquakes, and of the strongest coherent high-frequency generation areas. The region of the slab-crust interface between the mantle wedge limit, ∼142.7°E at ∼20 km depth, and a trenchward plate bending, ∼143.2°E at ∼15 km, acted as an effective barrier resisting for many centuries to stress-loading gradient induced by deep stable sliding and large earthquakes along the slab-mantle interface. The 2011 Tohoku earthquake, whose hypocenter is located on the east side of the

  2. Broadband seismic monitoring of active volcanoes using deterministic and stochastic approaches

    NASA Astrophysics Data System (ADS)

    Kumagai, H.; Nakano, M.; Maeda, T.; Yepes, H.; Palacios, P.; Ruiz, M. C.; Arrais, S.; Vaca, M.; Molina, I.; Yamashina, T.

    2009-12-01

    We systematically used two approaches to analyze broadband seismic signals observed at active volcanoes: one is waveform inversion of very-long-period (VLP) signals in the frequency domain assuming possible source mechanisms; the other is a source location method of long-period (LP) and tremor using their amplitudes. The deterministic approach of the waveform inversion is useful to constrain the source mechanism and location, but is basically only applicable to VLP signals with periods longer than a few seconds. The source location method uses seismic amplitudes corrected for site amplifications and assumes isotropic radiation of S waves. This assumption of isotropic radiation is apparently inconsistent with the hypothesis of crack geometry at the LP source. Using the source location method, we estimated the best-fit source location of a VLP/LP event at Cotopaxi using a frequency band of 7-12 Hz and Q = 60. This location was close to the best-fit source location determined by waveform inversion of the VLP/LP event using a VLP band of 5-12.5 s. The waveform inversion indicated that a crack mechanism better explained the VLP signals than an isotropic mechanism. These results indicated that isotropic radiation is not inherent to the source and only appears at high frequencies. We also obtained a best-fit location of an explosion event at Tungurahua when using a frequency band of 5-10 Hz and Q = 60. This frequency band and Q value also yielded reasonable locations for the sources of tremor signals associated with lahars and pyroclastic flows at Tungurahua. The isotropic radiation assumption may be valid in a high frequency range in which the path effect caused by the scattering of seismic waves results in an isotropic radiation pattern of S waves. The source location method may be categorized as a stochastic approach based on the nature of scattering waves. We further applied the waveform inversion to VLP signals observed at only two stations during a volcanic crisis

  3. The Influence of Seismic Amplification and Distanced Surcharge on the Active Thrust on Earth-Reinforced Walls

    SciTech Connect

    Biondi, Giovani; Grassi, Francesco; Maugeri, Michele

    2008-07-08

    The paper describes a closed form pseudo-static solution for the estimation of the active earth-pressure coefficient for an earth-reinforced wall assuming a non-uniform profile of the seismic coefficients along the wall height and a distanced uniformly-distributed surcharge on the backfill surface. The static and seismic hydraulic conditions of the backfill are also accounted for. A parametric analysis is carried out and the obtained results are discussed.

  4. Annual Hanford Seismic Report for Fiscal Year 2002

    SciTech Connect

    Hartshorn, Donald C.; Reidel, Steve P.; Rohay, Alan C.

    2002-11-15

    This report summarizes the earthquake activity on Hanford for FY 2002. Hanford Seismic Monitoring provides an uninterrupted collection of high-quality raw and processed seismic data from the Hanford Seismic Network for the U.S. Department of Energy and its contractors. Hanford Seismic Monitoring also locates and identifies sources of seismic activity and monitors changes in the historical pattern of seismic activity at the Hanford Site. The data are compiled, archived, and published for use by the Hanford Site for waste management, Natural Phenomena Hazards assessments, and engineering design and construction. In addition, the seismic monitoring organization works with the Hanford Site Emergency Services Organization to provide assistance in the event of a significant earthquake on the Hanford Site. The Hanford Seismic Network and the Eastern Washington Regional Network consist of 41 individual sensor sites and 15 radio relay sites maintained by the Hanford Seismic Monitoring staff. For the Hanford Seismic Network, there were 1,177 triggers during fiscal year 2002. Of these triggers, 553 were earthquakes. Two earthquakes were located in the Hanford Seismic Network area. Stratigraphically 13 occurred in the Columbia River basalt, 12 were earthquakes in the pre-basalt sediments, and 17 were earthquakes in the crystalline basement. Geographically, 13 earthquakes occurred in swarm areas, 1 earthquake was associated with major structures, and 28 were random events. There were no earthquake triggers of the Hanford Strong Motion Accelerometers during fiscal year 2002.

  5. Investigations On Historic Centers In Seismic Areas: Guidelines For The Diagnosis

    SciTech Connect

    Binda, Luigia; Cardani, Giuliana; Modena, Claudio; Valluzzi, Maria Rosa; Saisi, Antonella

    2008-07-08

    After the earthquake that hit central Italy in 1979, many small historic centers were restored. A subsequent seismic event occurred in 1997 in Umbria-Marche regions revealed that some techniques used in the previous interventions were not successful due to low durability of new materials and/or incompatibility between the new and the existing materials and structures. An extensive investigation on four small typical historic centers in Umbria was carried out. The objectives of the research were: (i) to define a methodology for the vulnerability analysis of historic buildings at the level of the historic centre, (ii) to collect information on the effectiveness of the repair techniques both traditional and new, (iii) to set up Databases storing the information useful to prepare rescue plans, (iv) to use the collected knowledge for the implementation of reliable models for the vulnerability analysis, (v) to prepare guidelines for investigation and vulnerability analysis.

  6. An Evaluation of Seismic Reflection Studies in the Yucca Mountain Area, Nevada Test Site

    USGS Publications Warehouse

    McGovern, Thomas F.; Introduction by Pankratz, L. W.; Ackermann, H.D.

    1983-01-01

    As part of a total geophysical evaluation of Yucca Mountain for use as a Nuclear Waste Repository the seismic reflection technique has been applied. This study has been conducted to analyze the historical and technical efforts which have been used by three geophysical contractors employing a wide variety of techniques ranging from the most simple to very elaborate 3-D surveys. In each case elaborate noise studies were conducted, and based upon their evaluation parameters were chosen for multifold CDP recording. In every case, the signal-to-noise ratio was such that no reflections were discernable. Since the reflections cannot be separated from the noise even using very elaborate noise suppression techniques and up to 384 fold multiplicity it is apparent that in this volcanic terrain reflection surveys, can not work.

  7. Analysis of the seismicity activity of the volcano Ceboruco, Nayarit, Mexico

    NASA Astrophysics Data System (ADS)

    Rodriguez-Ayala, N. A.; Nunez-Cornu, F. J.; Escudero, C. R.; Zamora-Camacho, A.; Gomez, A.

    2014-12-01

    The Ceboruco is a stratovolcano is located in the state of Nayarit,Mexico (104 ° 30'31 .25 "W, 21 ° 7'28 .35" N, 2280msnm). This is an volcano active, as part of the Trans-Mexican Volcanic Belt, Nelson (1986) reports that it has had activity during the last 1000 years has averaged eruptions every 125 years or so, having last erupted in 1870, currently has fumarolic activity. In the past 20 years there has been an increase in the population and socio-economic activities around the volcano (Suárez Plascencia, 2013); which reason the Ceboruco study has become a necessity in several ways. Recent investigations of seismicity (Rodríguez Uribe et al., 2013) have classified the earthquakes in four families Ceboruco considering the waveform and spectral features. We present analysis included 57 days of seismicity from March to October 2012, in the period we located 97 events with arrivals of P and S waves clear, registered in at least three seasons, three components of the temporal network Ceboruco volcano.

  8. Recent upper mantle structure beneath Siberia and surrounding areas according to a seismic tomography and numerical thermogravitational convection modeling data

    NASA Astrophysics Data System (ADS)

    Bushenkova, N.; Chervov, V.; Koulakov, I.

    2012-04-01

    We investigate the interaction between the recent lithosphere structure and dynamics of the upper mantle beneath a big segment of Asia. This study is based on the results of seismic tomography using travel times from the ISC catalog (1964-2007) and numerical thermogravitational modeling. The model contains thick lithosphere blocks of the Siberian Craton, the Tarim plate, and remnant parts of the Mongol-Tuva microcontinent. These blocks are alternated with weaker younger lithosphere corresponding to the West-Siberian plate, orogenic belts in southern Siberia and the Arctic shelves to the north. In the tomography part, we have updated a previously published model by Koulakov and Bushenkova (2010) based on a larger dataset including reflected PP and teleseismic P travel times from global catalogues. The lithosphere thickness has been estimated based on seismic anomalies at 250 km depth according to a technique described in (Bushenkova et al., 2008). These estimates were used to define the lithosphere thickness which is then implemented for setting the boundary conditions in numerical modeling and for joint interpretation of the final results. When computing the mantle dynamics, we consider the viscosity which is depends from temperature and pressure. Calculations are performed in the spherical coordinates. To minimize the boundary effects and to take into account the effect of the outside features, we considerably enlarged the calculation area by including the Russian, North- and South China Cratons and the Indian Plate. The modeling results demonstrate formation of steady ascending flows caused by overheating under the cratons (the average temperature of the upper mantle under a craton increases to ~100°) and descending flows on their periphery. The ascending flows spread along the bottom of the cratonic lithosphere and propagate towards its edges which cause smaller-scale convection cells nearly the borders of the cratons. The computed temperature distribution is

  9. Seismic structure beneath the Gulf of Aqaba and adjacent areas based on the tomographic inversion of regional earthquake data

    NASA Astrophysics Data System (ADS)

    El Khrepy, Sami; Koulakov, Ivan; Al-Arifi, Nassir; Petrunin, Alexey G.

    2016-06-01

    We present the first 3-D model of seismic P and S velocities in the crust and uppermost mantle beneath the Gulf of Aqaba and surrounding areas based on the results of passive travel time tomography. The tomographic inversion was performed based on travel time data from ˜ 9000 regional earthquakes provided by the Egyptian National Seismological Network (ENSN), and this was complemented with data from the International Seismological Centre (ISC). The resulting P and S velocity patterns were generally consistent with each other at all depths. Beneath the northern part of the Red Sea, we observed a strong high-velocity anomaly with abrupt limits that coincide with the coastal lines. This finding may indicate the oceanic nature of the crust in the Red Sea, and it does not support the concept of gradual stretching of the continental crust. According to our results, in the middle and lower crust, the seismic anomalies beneath the Gulf of Aqaba seem to delineate a sinistral shift (˜ 100 km) in the opposite flanks of the fault zone, which is consistent with other estimates of the left-lateral displacement in the southern part of the Dead Sea Transform fault. However, no displacement structures were visible in the uppermost lithospheric mantle.

  10. The Seismic Broad Band Western Mediterranean (wm) Network and the Obs Fomar Pool: Current state and Obs activities.

    NASA Astrophysics Data System (ADS)

    Pazos, Antonio; Davila, Jose Martin; Buforn, Elisa; Bezzeghoud, Mourad; Harnafi, Mimoun; Mattesini, Mauricio; Caldeira, Bento; Hanka, Winfried; El Moudnib, Lahcen; Strollo, Angelo; Roca, Antoni; Lopez de Mesa, Mireya; Dahm, Torsten; Cabieces, Roberto

    2016-04-01

    The Western Mediterranean (WM) seismic network started in 1996 as an initiative of the Royal Spanish Navy Observatory (ROA) and the Universidad Complutense de Madrid (UCM), with the collaboration of the GeoForschungsZentrum (GFZ) of Potsdam. A first broad band seismic station (SFUC) was installed close to Cádiz (South Spain). Since then, additional stations have been installed in the Ibero-Moghrebian region. In 2005, the "WM" code was assigned by the FDSN and new partners were jointed: Evora University (UEVO, Portugal), the Scientifique Institute of Rabat (ISRABAT, Morocco), and GFZ. Now days, the WM network is composed by 15 BB stations, all of them with Streckaisen STS-2 or STS-2.5 sensors, Quanterra or Earthdata digitizers and SeiscomP. Most them have co-installed a permanent geodetic GPS stations, and some them also have an accelerometer. There are 10 stations deployed in Spanish territory (5 in the Iberian peninsula, 1 in Balearic islands and 4 in North Africa Spanish places) with VSAT or Internet communications, 2 in Portugal (one of them without real time), and 3 in Morocco (2 VSAT and 1 ADSL). Additionally, 2 more stations (one in South Spain and one in Morocco) will be installed along this year. Additionally ROA has deployed a permanent real time VBB (CMG-3T: 360s) station at the Alboran Island. Due to the fact that part of the seismic activity is located at marine areas, and also because of the poor geographic azimuthal coverage at some zones provided by the land stations (specially in the SW of the San Vicente Cape area), ROA and UCM have acquired six broad band "LOBSTERN" OBS, manufactured by KUM (Kiel, Germany), conforming the OBS FOMAR pool. Three of them with CMG-40T sensor and the other with Trillium 120. These OBS were deployed along the Gibraltar strait since January to November 2014 to study the microseismicity in the Gibraltar strait area. In September 2015 FOMAR network has been deployed in SW of the San Vicente Cape for 8 months as a part of

  11. The Mw4.8 Norris Geyser Basin Earthquake of 30 March, 2014 and its Relationship to Crustal Deformation and Seismic Activity of the Yellowstone Volcanic System

    NASA Astrophysics Data System (ADS)

    Farrell, J.; Shelly, D. R.; Smith, R. B.; Puskas, C. M.; Chang, W. L.

    2014-12-01

    The largest earthquake to be recorded in Yellowstone in over 30 years, a magnitude 4.8 earthquake, occurred on March 30, 2014 near the Norris Geyser Basin on the NW side of the 0.64 Ma Yellowstone caldera. The earthquake was felt throughout Yellowstone and the surrounding region. We analyze this unusual event using data from the Yellowstone Seismic and Geodetic networks in the context of active volcanic-tectonic processes of the Yellowstone volcanic system and its relationship to regional swarm seismicity and crustal deformation. Moment tensor analysis of the March 30 earthquake revealed a strike-slip, double-couple source mechanism with no isotropic contribution. This earthquake was part of a larger sequence of earthquake swarm activity in the Norris Geyser Basin area that began in September 2013 and continued into June 2014. During that period, 50-60% of the total seismicity recorded in Yellowstone, including nearly all of the swarm seismicity (earthquakes clustered in time and space), occurred in the Norris Geyser Basin area. In addition, GPS derived deformation data revealed unusually high uplift rates at ~15 cm/yr in the Norris area prior to the MW4.8 event, while a dramatic reversal to subsidence at rates of ~20 cm/yr occurred after the event. Regionally, the much larger Yellowstone caldera had experienced subsidence since January 2010 at rates of ~1.5 cm/yr prior to the MW4.8 event. After March 30, 2014 the caldera reversed to regional uplift at rates of ~10 cm/yr, similar to accelerated uplift rates observed in mid-2004.

  12. Movement of the Earth pole and the seismic activity in 2001-2012

    NASA Astrophysics Data System (ADS)

    Andreev, Aleksey; Zabbarova, Regina; Lapaeva, Valentina; Nefedyev, Yuri

    2014-05-01

    The relationship between the parameters which characterize the movement of the Earth pole and seismic activity are considered. The correlation of the considered parameters is studied. The discussions about the relationship of poles movement and irregularity in speed of Earth rotation with seismic activity were actively performed in 60- 70th years of last century. Mainly, the influence of seismicity on pole movement was considered in this works. In particular, the question about excitation of a pole by earthquakes chandler's fluctuations was studied. An interest in the similar researches continues till now. The chandler's movements investigations and their relation with rotation of the Earth and seismicity were proceeded. The correlation between appearance of earthquakes and abnormal evasion of time and latitude for the observatories located near an epicenter was also discussed. What changes in position of the Earth pole do occur as a result of the strongest earthquakes? To answer on this question it is necessary to study variations of "an average pole", where the basic periodic components in movement of a pole having amplitude 0.1"-0.3" are accepted. To perform the analysis of the pole co-ordinates (X and Y) the International service of the Earth rotation for 1995-2012 have been considered. Linear Orlov-Saharov transformation has been applied to an exception of the periodic movement. On the basis of this positions changes of an average pole (aperiodicity displacement and long periodical variations of an axis of rotation in a Earth body) have been calculated with an interval of 0.1 years. Was found the changes of position of an average pole of the Earth was preceded the most considerable seismic events of the beginning of 21 century. As a whole, the increase of seismic activity has begun after 2002 only. For example, there were 2 strong earthquakes with magnitude 7 and more (Salvador, India) in 2001 , 2 earthquakes (Tajikistan, Taiwan) occurred in 2002, and 5

  13. The 2013 earthquake swarm in Helike, Greece: seismic activity at the root of old normal faults

    NASA Astrophysics Data System (ADS)

    Kapetanidis, V.; Deschamps, A.; Papadimitriou, P.; Matrullo, E.; Karakonstantis, A.; Bozionelos, G.; Kaviris, G.; Serpetsidaki, A.; Lyon-Caen, H.; Voulgaris, N.; Bernard, P.; Sokos, E.; Makropoulos, K.

    2015-09-01

    The Corinth Rift in Central Greece has been studied extensively during the past decades, as it is one of the most seismically active regions in Europe. It is characterized by normal faulting and extension rates between 6 and 15 mm yr-1 in an approximately N10E° direction. On 2013 May 21, an earthquake swarm was initiated with a series of small events 4 km southeast of Aigion city. In the next days, the seismic activity became more intense, with outbursts of several stronger events of magnitude between 3.3 and 3.7. The seismicity migrated towards the east during June, followed by a sudden activation of the western part of the swarm on July 15th. More than 1500 events have been detected and manually analysed during the period between 2013 May 21 and August 31, using over 15 local stations in epicentral distances up to 30 km and a local velocity model determined by an error minimization method. Waveform similarity-based analysis was performed, revealing several distinct multiplets within the earthquake swarm. High-resolution relocation was applied using the double-difference algorithm HypoDD, incorporating both catalogue and cross-correlation differential traveltime data, which managed to separate the initial seismic cloud into several smaller, densely concentrated spatial clusters of strongly correlated events. Focal mechanism solutions for over 170 events were determined using P-wave first motion polarities, while regional waveform modelling was applied for the calculation of moment tensors for the 18 largest events of the sequence. Selected events belonging to common spatial groups were considered for the calculation of composite mechanisms to characterize different parts of the swarm. The solutions are mainly in agreement with the regional NNE-SSW extension, representing typical normal faulting on 30-50° north-dipping planes, while a few exhibit slip in an NNE-SSW direction, on a roughly subhorizontal plane. Moment magnitudes were calculated by spectral analysis

  14. Preliminary Results from the iMUSH Active Source Seismic Experiment

    NASA Astrophysics Data System (ADS)

    Levander, Alan; Kiser, Eric; Palomeras, Imma; Zelt, Colin; Schmandt, Brandon; Hansen, Steve; Harder, Steven; Creagar, Kenneth; Vidale, John; Abers, Geoffrey

    2015-04-01

    iMUSH (imaging Magma Under Saint Helens) is a US NSF sponsored multi-disciplinary investigation of Mount Saint Helens (MSH), currently the most active volcano in the Cascades arc in the northwestern United States. The project consists of active and passive seismic experiments, extensive magnetotelluric sounding, and geological/geochemical studies involving scientists at 7 institutions in the U.S. and Europe. The long-term goal of the seismic project is to combine analysis of the active source data with that of data from the 70 element broadband seismograph operating from summer 2014 until 2016. Combining seismic and MT analyses with other data, we hope to image the MSH volcanic plumbing system from the surface to the subducting Juan de Fuca slab. Here we describe preliminary results of the iMUSH active source seismic experiment, conducted in July and August 2014. The active source experiment consisted of twenty-three 454 or 908 kg weight shots recorded by ~3500 seismographs deployed at ~6,000 locations. Of these instruments, ~900 Nodal Seismic instruments were deployed continuously for two weeks in an areal array within 10 km of the MSH summit. 2,500 PASSCAL Texan instruments were deployed twice for five days in 3 areal arrays and 2 dense orthogonal linear arrays that extended from MSH to distances > 80 km. Overall the data quality from the shots is excellent. The seismograph arrays also recorded dozens of micro-earthquakes beneath the MSH summit and along the MSH seismic zone, and numerous other local and regional earthquakes. In addition, at least one low frequency event beneath MSH was recorded during the experiment. At this point we have begun various types of analysis of the data set: We have determined an average 1D Vp structure from stacking short-term/long-term average ratios, we have determined the 2-D Vp structure from ray-trace inversions along the two orthogonal profiles (in the NW-SE and NE-SW directions), and we have made low-fold CMP stacks of the

  15. Field Report on the iMUSH Active Source Seismic Experiment

    NASA Astrophysics Data System (ADS)

    Kiser, E.; Levander, A.; Schmandt, B.; Palomeras, I.; Harder, S. H.; Creager, K. C.; Vidale, J. E.; Malone, S. D.

    2014-12-01

    In the second half of July we completed the iMUSH active source seismic experiment, one component of the Imaging Magma Under Saint Helens project. A team of ~75 volunteers deployed 3500 seismographs to ~5920 locations on and around Mount St. Helens over the course of 3 weeks. This instrument deployment was accompanied by 23 shots distributed around the volcano. Instrumentation consisted of ~2550 Reftek 125A (Texan) seismographs with 4.5 Hz geophones, and 920 Nodal Seismic recorders with 10 Hz geophones. The shots were also recorded by the permanent stations of the Pacific Northwest Seismograph Network and 70 iMUSH broadband seismographs. Fifteen of the shots, 424 kg each, formed two rings around Mount Saint Helens at 15 km and 30 km radius from the summit. Eight of the shots, 828 kg each, were fired at distances of 50 to 80 km from MSH on NW-SE and NE-SW azimuths. The deployment geometry consisted of two lines oriented NW/SE and NE/SW, and three arrays. The offset of the lines ranged from 150 km to 190 km with an average spacing of 200 m. The first array was centered on the volcano with a radius of 30 km, and required both driving and hiking to deploy. Arrays two and three were set out with, and centered on, the NW/SE line. These arrays had a distance range from MSH of 30-75 km and an azimuth range of about 100 degrees. In addition to this large-scale deployment, we set out 7 beamforming arrays approximately collocated with iMUSH broadband seismographs, and above clusters of seismicity in the region. The aperture of these arrays was about 1 km with an instrument spacing of 100 m. The final deployment ended only days before the AGU abstract deadline, so we have not yet examined all of the data. However, the preliminary indications are that signal to noise is excellent: The shots, several of which registered on PNSN as ML>2.1, carried across the entire array, and were recorded as far away as Seattle and Corvallis on permanent stations. The array also recorded a

  16. Fault mirrors of seismically active faults: A fossil of small earthquakes at shallow depths

    NASA Astrophysics Data System (ADS)

    Kuo, L.; Song, S.; Suppe, J.

    2013-12-01

    Many faults are decorated with naturally polished and glossy surfaces named fault mirrors (FMs) formed during slips. The characterization of FMs is of paramount importance to investigate physico-chemical processes controlling dynamic fault mechanics during earthquakes. Here we present detailed microstructural and mineralogical observations of the FMs from borehole cores of seismically active faults. The borehole cores were recovered from 600 to 800 m depth located in the hanging wall of the Hsiaotungshi fault in Taiwan which ruptured during 1935 Mw7.1 Hsinchu-Taichung earthquake. Scanning electron microscope (SEM) images of FMs show that two distinct textural domains, fault gouge and coated materials (nanograins, melt patchs, and graphite), were cut by a well-defined boundary. Melt patches and graphite, determined by X-ray diffraction (XRD), Transmission electron microscope (TEM), and SEM-EDS analysis, were found to be distributed heterogeneously on the slip surfaces. On the basis of the current kinematic cross section of the Hsiaotungshi fault, all the FMs were exhumed less than 5 km, where ambient temperatures are less than 150°C. It seems that the amorphous materials on the FMs were generated by seismic slips. The sintering nanograins coating the slip surfaces was also suggested to be produced at high slip rates from both natural observation and recent rock deformation experiments. In addition, graphite could be produced by seismic slips and lubricate the fault based on the rock deformation experiments. Our observation suggests that the FMs were composed of several indicators of coseismic events (melt patches, sintering nanograins, and graphite) corresponding to small thermal perturbation generated by seismic slips. Although the contribution of these coseismic indicators on frictional behavior remains largely unknown, it suggests that multiple dynamic weakening mechanisms such as flash heating, powder lubrication and graphitization may be involved during

  17. Crustal Structure in the Imperial Valley Region of California From Active-Source Seismic Investigations

    NASA Astrophysics Data System (ADS)

    Fuis, G. S.; Mooney, W. D.

    2008-12-01

    New crust is being generated by rifting in the Salton Trough. As the rift opens, mafic intrusive rocks fill it from below as young sedimentary rocks fill it from above. Rifting and intrusion produce high heat flow and temperatures that metamorphose the sedimentary rocks to shallow depths, forming a metasedimentary basement in the central part of the Trough, or Imperial Valley, thus consolidating the new crust. The U.S. Geological Survey conducted an extensive seismic-refraction survey in the Imperial Valley region of California in 1979, and recorded additional data in 1992. Profile data were modeled using a combination of forward and inverse modeling techniques. First arrivals on profiles and arrays from all shots were combined in an inversion for a basement-depth model. Finally an an existing gravity profile across the Salton Trough was modeled. Results are as follows: (1) No first-order velocity discontinuity is observed between sedimentary and "basement" rocks in the Imperial Valley; whereas such a discontinuity is observed on West Mesa, west of the Imperial Valley. In the Imperial Valley, basement velocity is 5.65 km/s, and basement is as much as 6 km deep. On West Mesa, basement velocity is 5.9 km/s and is at most 2 km deep. In the Imperial Valley, basement shoals beneath known geothermal areas, and the deepest wells (approx. 4 km) have penetrated only the upper part of the known Cenozoic stratigraphic column in the Salton Trough. Based on these results, we interpret basement in the Imperial Valley to be sedimentary rocks metamorphosed to lower greenschist facies and basement on West Mesa to be crystalline rocks. (2) The Imperial fault offsets basement in a normal sense by as much as 1 km down to the northeast, and there is an irregular basement scarp as high as 3.5 km between West Mesa and the Imperial Valley, which we interpret as a rift suture between old crystalline and young metasedimentary basement. (3) "Subbasement" (Vp 6.9 km/s) is seen at depths as

  18. The seismic traffic footprint: Tracking trains, aircraft, and cars seismically

    NASA Astrophysics Data System (ADS)

    Riahi, Nima; Gerstoft, Peter

    2015-04-01

    Although naturally occurring vibrations have proven useful to probe the subsurface, the vibrations caused by traffic have not been explored much. Such data, however, are less sensitive to weather and low visibility compared to some common out-of-road traffic sensing systems. We study traffic-generated seismic noise measured by an array of 5200 geophones that covered a 7 × 10 km area in Long Beach (California, USA) with a receiver spacing of 100 m. This allows us to look into urban vibrations below the resolution of a typical city block. The spatiotemporal structure of the anthropogenic seismic noise intensity reveals the Blue Line Metro train activity, departing and landing aircraft in Long Beach Airport and their acceleration, and gives clues about traffic movement along the I-405 highway at night. As low-cost, stand-alone seismic sensors are becoming more common, these findings indicate that seismic data may be useful for traffic monitoring.

  19. Broadband seismology and small regional seismic networks

    USGS Publications Warehouse

    Herrmann, Robert B.

    1995-01-01

    In the winter of 1811-12, three of the largest historic earthquakes in the United States occurred near New Madrid, Missouri. Seismicity continues to the present day throughout a tightly clustered pattern of epicenters centered on the bootheel of Missouri, including parts of northeastern Arkansas, northwestern Tennessee, western Kentucky, and southern Illinois. In 1990, the New Madrid seismic zone/Central United States became the first seismically active region east of the Rocky Mountains to be designated a priority research area within the National Earthquake Hazards Reduction Program (NEHRP). This Professional Paper is a collection of papers, some published separately, presenting results of the newly intensified research program in this area. Major components of this research program include tectonic framework studies, seismicity and deformation monitoring and modeling, improved seismic hazard and risk assessments, and cooperative hazard mitigation studies.

  20. Combined Active and Passive Seismic Methods To Characterize Strongmotion Sites in Washington and Oregon, United States

    NASA Astrophysics Data System (ADS)

    Pileggi, D.; Cakir, R.; Lunedei, E.; Albarello, D.; Walsh, T. J.

    2011-12-01

    Knowledge of the shear-wave velocity profile at strongmotion station sites is important for calibrating accelerograms in terms of local site effects. Surface-wave seismic prospecting methods (both in active and passive configurations) provide an effective tool for an inexpensive and deep penetrating seismic characterization of subsoil. We used a combination of active (Multi-channel Analysis of Surface Waves, MASW) and passive (Extended Spectral AutoCorrelation, ESAC) array techniques along with the single-station ambient vibration measurement