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Sample records for active seismic surveys

  1. 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.

  2. 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

  3. 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.

  4. 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

  5. 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

  6. 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.

  7. Active and passive seismic methods for characterization and monitoring of unstable rock masses: field surveys, laboratory tests and modeling.

    NASA Astrophysics Data System (ADS)

    Colombero, Chiara; Baillet, Laurent; Comina, Cesare; Jongmans, Denis; Vinciguerra, Sergio

    2016-04-01

    Appropriate characterization and monitoring of potentially unstable rock masses may provide a better knowledge of the active processes and help to forecast the evolution to failure. Among the available geophysical methods, active seismic surveys are often suitable to infer the internal structure and the fracturing conditions of the unstable body. For monitoring purposes, although remote-sensing techniques and in-situ geotechnical measurements are successfully tested on landslides, they may not be suitable to early forecast sudden rapid rockslides. Passive seismic monitoring can help for this purpose. Detection, classification and localization of microseismic events within the prone-to-fall rock mass can provide information about the incipient failure of internal rock bridges. Acceleration to failure can be detected from an increasing microseismic event rate. The latter can be compared with meteorological data to understand the external factors controlling stability. On the other hand, seismic noise recorded on prone-to-fall rock slopes shows that the temporal variations in spectral content and correlation of ambient vibrations can be related to both reversible and irreversible changes within the rock mass. We present the results of the active and passive seismic data acquired at the potentially unstable granitic cliff of Madonna del Sasso (NW Italy). Down-hole tests, surface refraction and cross-hole tomography were carried out for the characterization of the fracturing state of the site. Field surveys were implemented with laboratory determination of physico-mechanical properties on rock samples and measurements of the ultrasonic pulse velocity. This multi-scale approach led to a lithological interpretation of the seismic velocity field obtained at the site and to a systematic correlation of the measured velocities with physical properties (density and porosity) and macroscopic features of the granitic cliff (fracturing, weathering and anisotropy). Continuous

  8. Seismic Vulnerability Evaluations Within The Structural And Functional Survey Activities Of The COM Bases In Italy

    SciTech Connect

    Zuccaro, G.; Cacace, F.; Albanese, V.; Mercuri, C.; Papa, F.; Pizza, A. G.; Sergio, S.; Severino, M.

    2008-07-08

    The paper describes technical and functional surveys on COM buildings (Mixed Operative Centre). This activity started since 2005, with the contribution of both Italian Civil Protection Department and the Regions involved. The project aims to evaluate the efficiency of COM buildings, checking not only structural, architectonic and functional characteristics but also paying attention to surrounding real estate vulnerability, road network, railways, harbours, airports, area morphological and hydro-geological characteristics, hazardous activities, etc. The first survey was performed in eastern Sicily, before the European Civil Protection Exercise 'EUROSOT 2005'. Then, since 2006, a new survey campaign started in Abruzzo, Molise, Calabria and Puglia Regions. The more important issue of the activity was the vulnerability assessment. So this paper deals with a more refined vulnerability evaluation technique by means of the SAVE methodology, developed in the 1st task of SAVE project within the GNDT-DPC programme 2000-2002 (Zuccaro, 2005); the SAVE methodology has been already successfully employed in previous studies (i.e. school buildings intervention programme at national scale; list of strategic public buildings in Campania, Sicilia and Basilicata). In this paper, data elaborated by SAVE methodology are compared with expert evaluations derived from the direct inspections on COM buildings. This represents a useful exercise for the improvement either of the survey forms or of the methodology for the quick assessment of the vulnerability.

  9. Astor Pass Seismic Surveys Preliminary Report

    SciTech Connect

    Louie, John; Pullammanappallil, Satish; Faulds, James; Eisses, Amy; Kell, Annie; Frary, Roxanna; Kent, Graham

    2011-08-05

    In collaboration with the Pyramid Lake Paiute Tribe (PLPT), the University of Nevada, Reno (UNR) and Optim re-processed, or collected and processed, over 24 miles of 2d seismic-reflection data near the northwest corner of Pyramid Lake, Nevada. The network of 2d land surveys achieved a near-3d density at the Astor Pass geothermal prospect that the PLPT drilled during Nov. 2010 to Feb. 2011. The Bureau of Indian Affairs funded additional seismic work around the Lake, and an extensive, detailed single-channel marine survey producing more than 300 miles of section, imaging more than 120 ft below the Lake bottom. Optim’s land data collection utilized multiple heavy vibrators and recorded over 200 channels live, providing a state-of-the-art reflection-refraction data set. After advanced seismic analysis including first-arrival velocity optimization and prestack depth migration, the 2d sections show clear fault-plane reflections, in some areas as deep as 4000 ft, tying to distinct terminations of the mostly volcanic stratigraphy. Some lines achieved velocity control to 3000 ft depth; all lines show reflections and terminations to 5000 ft depth. Three separate sets of normal faults appear in an initial interpretation of fault reflections and stratigraphic terminations, after loading the data into the OpendTect 3d seismic visualization system. Each preliminary fault set includes a continuous trace more than 3000 ft long, and a swarm of short fault strands. The three preliminary normal-fault sets strike northerly with westward dip, northwesterly with northeast dip, and easterly with north dip. An intersection of all three fault systems documented in the seismic sections at the end of Phase I helped to locate the APS-2 and APS-3 slimholes. The seismic sections do not show the faults connected to the Astor Pass tufa spire, suggesting that we have imaged mostly Tertiary-aged faults. We hypothesize that the Recent, active faults that produced the tufa through hotspring

  10. 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

  11. 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

    2016-08-01

    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.

  12. Vertical Cable Seismic Survey for Hydrothermal Deposit

    NASA Astrophysics Data System (ADS)

    Asakawa, E.; Murakami, F.; Sekino, Y.; Okamoto, T.; Ishikawa, K.; Tsukahara, H.; Shimura, T.

    2012-04-01

    The vertical cable seismic is one of the reflection seismic methods. It uses hydrophone arrays vertically moored from the seafloor to record acoustic waves generated by surface, deep-towed or ocean bottom sources. Analyzing the reflections from the sub-seabed, we could look into the subsurface structure. This type of survey is generally called VCS (Vertical Cable Seismic). Because VCS is an efficient high-resolution 3D seismic survey method for a spatially-bounded area, we proposed the method for the hydrothermal deposit survey tool development program that the Ministry of Education, Culture, Sports, Science and Technology (MEXT) started in 2009. We are now developing a VCS system, including not only data acquisition hardware but data processing and analysis technique. Our first experiment of VCS surveys has been carried out in Lake Biwa, JAPAN in November 2009 for a feasibility study. Prestack depth migration is applied to the 3D VCS data to obtain a high quality 3D depth volume. Based on the results from the feasibility study, we have developed two autonomous recording VCS systems. After we carried out a trial experiment in the actual ocean at a water depth of about 400m and we carried out the second VCS survey at Iheya Knoll with a deep-towed source. In this survey, we could establish the procedures for the deployment/recovery of the system and could examine the locations and the fluctuations of the vertical cables at a water depth of around 1000m. The acquired VCS data clearly shows the reflections from the sub-seafloor. Through the experiment, we could confirm that our VCS system works well even in the severe circumstances around the locations of seafloor hydrothermal deposits. We have, however, also confirmed that the uncertainty in the locations of the source and of the hydrophones could lower the quality of subsurface image. It is, therefore, strongly necessary to develop a total survey system that assures a accurate positioning and a deployment techniques

  13. 75 FR 39335 - Incidental Takes of Marine Mammals During Specified Activities; Marine Seismic Survey in the...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-08

    ... Tracklines for USGS and Geological Survey of Canada (GSC) 2010 Extended Continental Shelf Survey in the.... Laurent and Healy Extended Continental Shelf expeditions in the Arctic Ocean, August 3 to September 16... Icebreaking Effort for USGS/GSC 2010 Extended Continental Shelf Survey in the Northern Beaufort Sea and...

  14. 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.

  15. 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

  16. Seismic Survey Challenges and Solutions in Industrial And Urban Environments

    NASA Astrophysics Data System (ADS)

    Coueslan, M. L.; El-Kaseeh, G.; Totten, S.

    2011-12-01

    Carbon storage projects are often located in close proximity to anthropogenic sources of CO2. This means that the storage site location may be near industrial power plants, mining activity, or urban centers. Proximity to these environments can present unique challenges for the seismic survey design, acquisition, and processing teams in terms of acquiring surface seismic data that meets the site characterization objectives for a CO2 storage site. Seismic surveys in urban and industrial environments may have acquisition footprints that are severely constrained by surrounding infrastructure. The acquisition crew and survey design team must work closely together in real-time to add in-fill source and receiver locations to surveys in order to ensure that high fold coverage is maintained over the survey. High levels of seismic noise may be generated by the industrial plants themselves. Local and industrial traffic, as well as electrical noise may also be a cause for concern. Near surface conditions, such as water saturated soils, unconsolidated mine tailings, and mining cavities, may accelerate attenuation of the seismic signal and become sources of noise in the survey and further impact data quality. When dealing with such conditions, the acquisition and survey design teams must stay in constant communication to optimize survey parameters to account for noise issues. In some cases, the raw data can be so contaminated with noise that no coherent signal can be seen in the data. However, the use of high density-single sensors is one of the most effective options to deal with noisy acquisition environments as this method allows the recorded noise to be sampled without aliasing so that that it can be removed from the data without impacting the seismic signal. Removing noise and optimizing the final images obtained from the data is the job of the survey design and data processing teams. A final consideration when acquiring seismic surveys in urban areas is the visibility of

  17. Elements of the Seismic Structure and Activity of the Lesser Antilles Subduction Zone (Guadeloupe and Martinique Islands) from the SISMANTILLES Seismic Survey

    NASA Astrophysics Data System (ADS)

    Laigle, M.; Roux, E.; Sapin, M.; Hirn, A.; de Voogd, B.; Charvis, P.; Hello, Y.; Murai, Y.; Nishimura, Y.; Shimamura, H.; Galve, A.; Lepine, J.; Lebrun, J.; Diaz, J.; Gallart, J.; Beauducel, F.; Viode, J.

    2005-12-01

    The Lesser Antilles is an active subduction zone, prone to future major earthquakes as it has experienced in the past with the occurrence in 1843 of a M>7.5 probably mega-thrust earthquake that destroyed Pointe-a-Pitre city on Guadeloupe Island. The SISMANTILLES project was carried out at a regional scale for a first reconnaissance of the seismic structure and activity from northern Guadeloupe to Martinique islands. The project focused more particularly on the detection, mapping and characterisation of the potentially seimogenic part of the interplate subduction fault. The french N/O Nadir vessel acquired 2500 km of deep-penetration multichannel reflection seismic (MCS) profiles. Up to 37 3-components Ocean Bottom Seismometers (OBS) were deployed offshore over several weeks together with a set of 3-components broadened-band stations on the islands (Martinique, Dominica, Guadeloupe and Antigua). These instruments recorded continuously both the MCS shots that provided wide angle reflexion and refraction (WARR) data as well as the local, regional and teleseismic earthquakes. On MCS profiles, reflections from the top of the subducting oceanic crust and decollement can be followed down to several km depth beneath the thick accretionary prism. Detailed velocity analysis provided depth structural sections that are used as an input for the forward modeling of WARR data. Thanks to these data, we can constrain on 3 transects to the arc, the part where the forearc deep crust is in contact with the subducting oceanic plate, considered as a proxy for the seismogenic part. Its location with respect to the deformation front and the volcanic arc and its downdip size appear significantly variable along the arc. The local earthquakes now reliably located in map and depth thanks to the high-quality P and S observations of the OBS network can be discussed with respect to these imaged structures. Local earthquakes P & S tomography as well as receiver functions analysis will bring more

  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. Vertical Cable Seismic Survey for SMS exploration

    NASA Astrophysics Data System (ADS)

    Asakawa, Eiichi; Murakami, Fumitoshi; Tsukahara, Hotoshi; Mizohata, Shigeharu

    2014-05-01

    The Vertical Cable Seismic (VCS) survey is one of the reflection seismic methods. It uses hydrophone arrays vertically moored from the seafloor to record acoustic waves generated by sea-surface, deep-towed or ocean bottom sources. Analyzing the reflections from the sub-seabed, we could look into the subsurface structure. Because the VCS is an efficient high-resolution 3D seismic survey method for a spatially-bounded area, we proposed it for the SMS survey tool development program that the Ministry of Education, Culture, Sports, Science and Technology (MEXT) started in 2009. We have been developing the VCS survey system, including not only data acquisition hardware but data processing and analysis technique. We carried out several VCS surveys combining with surface towed source, deep towed source and ocean bottom source. The water depths of these surveys are from 100m up to 2100 m. Through these experiments, our VCS data acquisition system has been also completed. But the data processing techniques are still on the way. One of the most critical issues is the positioning in the water. The uncertainty in the positions of the source and of the hydrophones in water degraded the quality of subsurface image. GPS navigation system is available on sea surface, but in case of deep-towed source or ocean bottom source, the accuracy of shot position with SSBL/USBL is not sufficient for the very high-resolution imaging. We have developed a new approach to determine the positions in water using the travel time data from the source to VCS hydrophones. In 2013, we have carried out the second VCS survey using the surface-towed high-voltage sparker and ocean bottom source in the Izena Cauldron, which is one of the most promising SMS areas around Japan. The positions of ocean bottom source estimated by this method are consistent with the VCS field records. The VCS data with the sparker have been processed with 3D PSTM. It gives the very high resolution 3D volume deeper than two

  20. Vertical cable surveys deliver additional seismic data

    SciTech Connect

    1995-12-01

    Texaco and a Norwegian seismic firm have patented a new system for deploying hydrophones on vertical cables for offshore surveys. The system was used in Texaco North Sea UK Ltd.`s Strathspey field during the summer. The new technique was introduced in the article, ``Peaceful use for war technology,`` published in Texaco UK`s Agenda monthly news magazine, October 1995. That article is summarized here. Using technology developed by the US Navy for antisubmarine warfare, the vertical-cable survey relies on hydrophones attached at regular intervals vertically along cables secured to the ocean floor and held taut by a buoy. The shooting vessel fires the airguns in a pattern over a large area on the surface, over and around the cables. The cables are then moved to a new location and the process is repeated, up to six times in the Strathspey application described here.

  1. Feeding of western gray whales during a seismic survey near Sakhalin Island, Russia.

    PubMed

    Yazvenko, S B; McDonald, T L; Blokhin, S A; Johnson, S R; Melton, H R; Newcomer, M W; Nielson, R; Wainwright, P W

    2007-11-01

    Exxon Neftegas Limited, as operator of the Sakhalin-1 consortium, is developing oil and gas reserves on the continental shelf off northeast Sakhalin Island, Russia. DalMorNefteGeofizika (DMNG) on behalf of the Sakhalin-1 consortium conducted a 3-D seismic survey of the Odoptu license area during 17 August-9 September 2001. A portion of the primary feeding area of the endangered western gray whale (Eschrichtius robustus) is located in the vicinity of the seismic survey. This paper presents data to assess whether western gray whale bottom feeding activity, as indicated by visible mud plumes, was affected by seismic operations. The mitigation and monitoring program associated with the seismic survey included aerial surveys during 19 July-19 November 2001. These aerial surveys documented the local and regional distribution, abundance, and bottom feeding activity of western gray whales. Data on gray whale feeding activity before, during and after the seismic survey were collected, with the whales assumed to be feeding on the benthos if mud plumes were observed on the surface. The data were used to assess the influence of seismic survey and other factors (including environmental) on feeding activity of western gray whales. A stepwise multiple regression analysis failed to find a statistically significant effect (alpha = 0.05) of the seismic survey on frequency of occurrence of mud plumes of western gray whales used as a proxy to evaluate bottom feeding activity in Piltun feeding area. The regression indicated that transect number (a proxy for water depth, related to distance from shore) and swell height (a proxy for sea state) were the only variables that had a significant effect on frequency of whale mud plumes. It is concluded that the 2001 seismic survey had no measurable effect (alpha = 0.05) on bottom feeding activity of western gray whales off Sakhalin Island.

  2. Quantifying seismic survey reverberation off the Alaskan North Slope.

    PubMed

    Guerra, Melania; Thode, Aaron M; Blackwell, Susanna B; Michael Macrander, A

    2011-11-01

    Shallow-water airgun survey activities off the North Slope of Alaska generate impulsive sounds that are the focus of much regulatory attention. Reverberation from repetitive airgun shots, however, can also increase background noise levels, which can decrease the detection range of nearby passive acoustic monitoring (PAM) systems. Typical acoustic metrics for impulsive signals provide no quantitative information about reverberation or its relative effect on the ambient acoustic environment. Here, two conservative metrics are defined for quantifying reverberation: a minimum level metric measures reverberation levels that exist between airgun pulse arrivals, while a reverberation metric estimates the relative magnitude of reverberation vs expected ambient levels in the hypothetical absence of airgun activity, using satellite-measured wind data. The metrics are applied to acoustic data measured by autonomous recorders in the Alaskan Beaufort Sea in 2008 and demonstrate how seismic surveys can increase the background noise over natural ambient levels by 30-45 dB within 1 km of the activity, by 10-25 dB within 15 km of the activity, and by a few dB at 128 km range. These results suggest that shallow-water reverberation would reduce the performance of nearby PAM systems when monitoring for marine mammals within a few kilometers of shallow-water seismic surveys.

  3. Quantifying seismic survey reverberation off the Alaskan North Slope.

    PubMed

    Guerra, Melania; Thode, Aaron M; Blackwell, Susanna B; Michael Macrander, A

    2011-11-01

    Shallow-water airgun survey activities off the North Slope of Alaska generate impulsive sounds that are the focus of much regulatory attention. Reverberation from repetitive airgun shots, however, can also increase background noise levels, which can decrease the detection range of nearby passive acoustic monitoring (PAM) systems. Typical acoustic metrics for impulsive signals provide no quantitative information about reverberation or its relative effect on the ambient acoustic environment. Here, two conservative metrics are defined for quantifying reverberation: a minimum level metric measures reverberation levels that exist between airgun pulse arrivals, while a reverberation metric estimates the relative magnitude of reverberation vs expected ambient levels in the hypothetical absence of airgun activity, using satellite-measured wind data. The metrics are applied to acoustic data measured by autonomous recorders in the Alaskan Beaufort Sea in 2008 and demonstrate how seismic surveys can increase the background noise over natural ambient levels by 30-45 dB within 1 km of the activity, by 10-25 dB within 15 km of the activity, and by a few dB at 128 km range. These results suggest that shallow-water reverberation would reduce the performance of nearby PAM systems when monitoring for marine mammals within a few kilometers of shallow-water seismic surveys. PMID:22087932

  4. Exposure to seismic survey alters blue whale acoustic communication.

    PubMed

    Di Iorio, Lucia; Clark, Christopher W

    2010-02-23

    The ability to perceive biologically important sounds is critical to marine mammals, and acoustic disturbance through human-generated noise can interfere with their natural functions. Sounds from seismic surveys are intense and have peak frequency bands overlapping those used by baleen whales, but evidence of interference with baleen whale acoustic communication is sparse. Here we investigated whether blue whales (Balaenoptera musculus) changed their vocal behaviour during a seismic survey that deployed a low-medium power technology (sparker). We found that blue whales called consistently more on seismic exploration days than on non-exploration days as well as during periods within a seismic survey day when the sparker was operating. This increase was observed for the discrete, audible calls that are emitted during social encounters and feeding. This response presumably represents a compensatory behaviour to the elevated ambient noise from seismic survey operations. PMID:19776059

  5. Exposure to seismic survey alters blue whale acoustic communication.

    PubMed

    Di Iorio, Lucia; Clark, Christopher W

    2010-02-23

    The ability to perceive biologically important sounds is critical to marine mammals, and acoustic disturbance through human-generated noise can interfere with their natural functions. Sounds from seismic surveys are intense and have peak frequency bands overlapping those used by baleen whales, but evidence of interference with baleen whale acoustic communication is sparse. Here we investigated whether blue whales (Balaenoptera musculus) changed their vocal behaviour during a seismic survey that deployed a low-medium power technology (sparker). We found that blue whales called consistently more on seismic exploration days than on non-exploration days as well as during periods within a seismic survey day when the sparker was operating. This increase was observed for the discrete, audible calls that are emitted during social encounters and feeding. This response presumably represents a compensatory behaviour to the elevated ambient noise from seismic survey operations.

  6. Distribution and abundance of western gray whales during a seismic survey near Sakhalin Island, Russia.

    PubMed

    Yazvenko, S B; McDonald, T L; Blokhin, S A; Johnson, S R; Meier, S K; Melton, H R; Newcomer, M W; Nielson, R M; Vladimirov, V L; Wainwright, P W

    2007-11-01

    Exxon Neftegas Limited, operator of the Sakhalin-1 consortium, is developing oil and gas reserves on the continental shelf off northeast Sakhalin Island, Russia. DalMorNefteGeofizika (DMNG), on behalf of the Sakhalin-1 consortium, conducted a 3-D seismic survey of the Odoptu license area during 17 August-9 September 2001. A portion of the primary known feeding area of the endangered western gray whale (Eschrichtius robustus) is located adjacent to the seismic block. The data presented here were collected as part of daily monitoring to determine if there was any measurable effect of the seismic survey on the distribution and abundance of western gray whales. Mitigation and monitoring program included aerial surveys conducted between 19 July and 19 November using the methodology outlined by the Southern California High Energy Seismic Survey team (HESS). These surveys provided documentation of the distribution, abundance and bottom feeding activity of western gray whales in relation to seismic survey sounds. From an operations perspective, the aerial surveys provided near real-time data on the location of whales in and outside the feeding area, and documented whether whales were displaced out of an area normally used as feeding habitat. The objectives of this study were to assess (a) temporal changes in the distribution and abundance of gray whales in relation to seismic survey, and (b) the influence of seismic survey, environmental factors, and other variables on the distribution and abundance of gray whales within their preferred feeding area adjacent to Piltun Bay. Multiple regression analysis revealed a limited redistribution of gray whales southward within the Piltun feeding area when the seismic survey was fully operational. A total of five environmental and other variables unrelated to seismic survey (date and proxies of depth, sea state and visibility) and one seismic survey-related variable (seg3d, i.e., received sound energy accumulated over 3 days) had

  7. Seismic Forecasting of Solar Activity

    NASA Technical Reports Server (NTRS)

    Braun, Douglas; Lindsey, Charles

    2001-01-01

    We have developed and improved helioseismic imaging techniques of the far-side of the Sun as part of a synoptic monitor of solar activity. In collaboration with the MIDI team at Stanford University we are routinely applying our analysis to images within 24 hours of their acquisition by SOHO. For the first time, real-time seismic maps of large active regions on the Sun's far surface are publicly available. The synoptic images show examples of active regions persisting for one or more solar rotations, as well as those initially detected forming on the solar far side. Until recently, imaging the far surface of the Sun has been essentially blind to active regions more than about 50 degrees from the antipode of disk center. In a paper recently accepted for publication, we have demonstrated how acoustic travel-time perturbations may be mapped over the entire hemisphere of the Sun facing away from the Earth, including the polar regions. In addition to offering significant improvements to ongoing space weather forecasting efforts, the procedure offers the possibility of local seismic monitoring of both the temporal and spatial variations in the acoustic properties of the Sun over the entire far surface.

  8. Bayesian spatial modeling of cetacean sightings during a seismic acquisition survey.

    PubMed

    Vilela, Raul; Pena, Ursula; Esteban, Ruth; Koemans, Robin

    2016-08-15

    A visual monitoring of marine mammals was carried out during a seismic acquisition survey performed in waters south of Portugal with the aim of assessing the likelihood of encountering Mysticeti species in this region as well as to determine the impact of the seismic activity upon encounter. Sightings and effort data were assembled with a range of environmental variables at different lags, and a Bayesian site-occupancy modeling approach was used to develop prediction maps and evaluate how species-specific habitat conditions evolved throughout the presence or not of seismic activity. No statistical evidence of a decrease in the sighting rates of Mysticeti by comparison to source activity was found. Indeed, it was found how Mysticeti distribution during the survey period was driven solely by environmental variables. Although further research is needed, possible explanations may include anthropogenic noise habituation and zone of seismic activity coincident with a naturally low density area.

  9. Development of Vertical Cable Seismic System for Hydrothermal Deposit Survey

    NASA Astrophysics Data System (ADS)

    Asakawa, Eiichi; Okamoto, Taku; Sekino, Yoshihiro; Murakami, Fumitoshi; Mikada, Hitoshi; Takekawa, Junichi; Shimura, Takuya

    2010-05-01

    Hydrothermal vents are commonly found near volcanically active places, areas where tectonic plates are moving apart, ocean basins, and hotspots. Potential new deposits of lead-zinc-copper sulfide are generated by cooling hot water around the vents. There are about ten hydrothermal deposits founded around the water depth of 1000m along Izu-Ogasawara Trench and Okinawa-Trough in Japan. The deposits often exists in very thin layer and spatially limited area surrounded by complex seabottom feature like volcanic caldera. Some hydrothermal vents form roughly cylindrical chimney structures. In order to evaluate hydrothermal deposit, we have proposed the reflection seismic survey with vertical cable recording geometry, which is named as VCS (Vertical Cable Seismic). VCS has great advantages over conventional seismic method as follows: 1. It achieves 3D image within limited area. The target of hydrothermal deposit is within 1km x 1km around the depth of 1000m. The conventional 3D seismic is not effective. 3D image is necessary for the estimate the complex hydrothermal area. 2. Seabottom condition is too rough to deploy ocean bottom sensors, such as OBC or OBS. Vertical cables are located on the seabottom, but the sensors are in the marine water. It avoids the coupling problems. The vertical hydrophone array can separate the wavefield. It can separate upgoing (reflection) and downgoing wave (direct wave and ghost) and distinguish the scattered waves in complex feature in hydrothermal area. 3. Various types of marine source are applicable with VCS such as sea-surface source (air gun, water gun etc.), marine vibrator or ocean bottom source. These features imply that VCS is suitable for the hydrothermal deposit exploration. Our first experiment has been carried out in November in Lake Biwa, JAPAN. At first we are interested in geometry of source and receiver distribution and the resultant target coverage, then we did survey planning (2D and 3D) and data simulation. We used the

  10. Barren Acidic Soil Assessment using Seismic Refraction Survey

    NASA Astrophysics Data System (ADS)

    Tajudin, S. A. A.; Abidin, M. H. Z.; Madun, A.; Zawawi, M. H.

    2016-07-01

    Seismic refraction method is one of the geophysics subsurface exploration techniques used to determine subsurface profile characteristics. From past experience, seismic refraction method is commonly used to detect soil layers, overburden, bedrock, etc. However, the application of this method on barren geomaterials remains limited due to several reasons. Hence, this study was performed to evaluate the subsurface profile characteristics of barren acidic soil located in Ayer Hitam, Batu Pahat, Johor using seismic refraction survey. The seismic refraction survey was conducted using ABEM Terraloc MK 8 (seismograph), a sledge hammer weighing 7 kg (source) and 24 units of 10 Hz geophones (receiver). Seismic data processing was performed using OPTIM software which consists of SeisOpt@picker (picking the first arrival and seismic configureuration data input) and SeisOpt@2D (generating 2D image of barren acidic soil based on seismic velocity (primary velocity, Vp) distribution). It was found that the barren acidic soil profile consists of three layers representing residual soil (Vp= 200-400 m/s) at 0-2 m, highly to completely weathered soil (Vp= 500-1800 m/s) at 3-8 m and shale (Vp= 2100-6200 m/s) at 9-20 m depth. Furthermore, result verification was successfully done through the correlation of seismic refraction data based on physical mapping and the geological map of the study area. Finally, it was found that the seismic refraction survey was applicable for subsurface profiling of barren acidic soil as it was very efficient in terms of time, cost, large data coverage and sustainable.

  11. Seismic surveys test on Innerhytta Pingo, Adventdalen, Svalbard Islands

    NASA Astrophysics Data System (ADS)

    Boaga, Jacopo; Rossi, Giuliana; Petronio, Lorenzo; Accaino, Flavio; Romeo, Roberto; Wheeler, Walter

    2015-04-01

    We present the preliminary results of an experimental full-wave seismic survey test conducted on the Innnerhytta a Pingo, located in the Adventdalen, Svalbard Islands, Norway. Several seismic surveys were adopted in order to study a Pingo inner structure, from classical reflection/refraction arrays to seismic tomography and surface waves analysis. The aim of the project IMPERVIA, funded by Italian PNRA, was the evaluation of the permafrost characteristics beneath this open-system Pingo by the use of seismic investigation, evaluating the best practice in terms of logistic deployment. The survey was done in April-May 2014: we collected 3 seismic lines with different spacing between receivers (from 2.5m to 5m), for a total length of more than 1 km. We collected data with different vertical geophones (with natural frequency of 4.5 Hz and 14 Hz) as well as with a seismic snow-streamer. We tested different seismic sources (hammer, seismic gun, fire crackers and heavy weight drop), and we verified accurately geophone coupling in order to evaluate the different responses. In such peculiar conditions we noted as fire-crackers allow the best signal to noise ratio for refraction/reflection surveys. To ensure the best geophones coupling with the frozen soil, we dug snow pits, to remove the snow-cover effect. On the other hand, for the surface wave methods, the very high velocity of the permafrost strongly limits the generation of long wavelengths both with these explosive sources as with the common sledgehammer. The only source capable of generating low frequencies was a heavy drop weight system, which allows to analyze surface wave dispersion below 10 Hz. Preliminary data analysis results evidence marked velocity inversions and strong velocity contrasts in depth. The combined use of surface and body waves highlights the presence of a heterogeneous soil deposit level beneath a thick layer of permafrost. This is the level that hosts the water circulation from depth controlling

  12. Seismic refraction survey of the ANS preferred site

    SciTech Connect

    Davis, R.K. ); Hopkins, R.A. ); Doll, W.E. )

    1992-02-01

    Between September 19, 1991 and October 8, 1991 personnel from Martin Marietta Energy Systems, Inc. (Energy Systems), Automated Sciences Group, Inc., and Marrich, Inc. performed a seismic refraction survey at the Advanced Neutron Source (ANS) preferred site. The purpose of this survey was to provide estimates of top-of-rock topography, based on seismic velocities, and to delineate variations in rock and soil velocities. Forty-four seismic refraction spreads were shot to determine top-of-rock depths at 42 locations. Nine of the seismic spreads were shot with long offsets to provide 216 top-of-rock depths for 4 seismic refraction profiles. The refraction spread locations were based on the grid for the ANS Phase I drilling program. Interpretation of the seismic refraction data supports the assumption that the top-of-rock surface generally follows the local topography. The shallow top-of-rock interface interpreted from the seismic refraction data is also supported by limited drill information at the site. Some zones of anomalous data are present that could be the result of locally variable weathering, a localized variation in shale content, or depth to top-of-rock greater than the site norm.

  13. Development of Vertical Cable Seismic System for Hydrothermal Deposit Survey

    NASA Astrophysics Data System (ADS)

    Asakawa, E.; Sekino, Y.; Okamoto, T.; Murakami, F.; Mikada, H.; Takekawa, J.; Shimura, T.; Watanabe, Y.; Asakawa, K.

    2009-12-01

    Hydrothermal vents are commonly found near volcanically active places, areas where tectonic plates are moving apart, ocean basins, and hotspots. Potential new deposits of lead-zinc-copper sulfide are generated by cooling hot water around the vents. There are about ten hydrothermal deposits founded around the water depth of 1000m along Izu-Ogasawara Trench and Okinawa-Trough in Japan. The deposits often exists in very thin layer and spatially limited area surrounded by complex seabottom feature like volcanic caldera. Some hydrothermal vents form roughly cylindrical chimney structures. In order to evaluate hydrothermal deposit, we have proposed the reflection seismic survey with vertical cable recording geometry, which is named as VCS (Vertical Cable Seismic). With this VCS, the following advantages will be provided for hydrothermal deposit survey. (1) It achieves 3D image within limited area which is necessary for estimating the complex hydrothermal deposit Typical hydrothermal deposit extend horizontally within 1km x 1km at the water depth of around 1000m. The conventional 3D seismic is not efficient for such limited target. (2) Seabottom condition is too rough to deploy ocean bottom sensors, such as OBC or OBS. Vertical cables are located on the seabottom, but the sensors are in the marine water. This is to avoid the coupling problems. With the use of the vertical hydrophone array, wavefield is able be separated. It can separate upgoing (reflection) and downgoing wave (direct wave and ghost) and distinguish the scattered waves in complex feature in hydrothermal area. (3) Various types of marine source are applicable with VCS such as sea-surface source (air gun, water gun etc.) or marine vibrator or ocean bottom source. This paper discusses the design of the surveys that can be the best for the 3D image of the target in the most economic way. We are interested in geometry of source and receiver distribution and the resultant target coverage. The first experiment is

  14. Making Waves: Seismic Waves Activities and Demonstrations

    NASA Astrophysics Data System (ADS)

    Braile, S. J.; Braile, L. W.

    2011-12-01

    The nature and propagation of seismic waves are fundamental concepts necessary for understanding the exploration of Earth's interior structure and properties, plate tectonics, earthquakes, and seismic hazards. Investigating seismic waves is also an engaging approach to learning basic principles of the physics of waves and wave propagation. Several effective educational activities and demonstrations are available for teaching about seismic waves, including the stretching of a spring to demonstrate elasticity; slinky wave propagation activities for compressional, shear, Rayleigh and Love waves; the human wave activity to demonstrate P- and S- waves in solids and liquids; waves in water in a simple wave tank; seismic wave computer animations; simple shake table demonstrations of model building responses to seismic waves to illustrate earthquake damage to structures; processing and analysis of seismograms using free and easy to use software; and seismic wave simulation software for viewing wave propagation in a spherical Earth. The use of multiple methods for teaching about seismic waves is useful because it provides reinforcement of the fundamental concepts, is adaptable to variable classroom situations and diverse learning styles, and allows one or more methods to be used for authentic assessment. The methods described here have been used effectively with a broad range of audiences, including K-12 students and teachers, undergraduate students in introductory geosciences courses, and geosciences majors.

  15. Seismic survey probes urban earthquake hazards in Pacific Northwest

    USGS Publications Warehouse

    Fisher, M.A.; Brocher, T.M.; Hyndman, R.D.; Trehu, A.M.; Weaver, C.S.; Creager, K.C.; Crosson, R.S.; Parsons, T.; Cooper, A. K.; Mosher, D.; Spence, G.; Zelt, B.C.; Hammer, P.T.; Childs, J. R.; Cochrane, G.R.; Chopra, S.; Walia, R.

    1999-01-01

    A multidisciplinary seismic survey earlier this year in the Pacific Northwest is expected to reveal much new information about the earthquake threat to U.S. and Canadian urban areas there. A disastrous earthquake is a very real possibility in the region. The survey, known as the Seismic Hazards Investigation in Puget Sound (SHIPS), engendered close cooperation among geologists, biologists, environmental groups, and government agencies. It also succeeded in striking a fine balance between the need to prepare for a great earthquake and the requirement to protect a coveted marine environment while operating a large airgun array.

  16. 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

  17. 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

  18. 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.

  19. A comparative study between a rectilinear 3-D seismic survey and a concentric-circle 3-D seismic survey

    SciTech Connect

    Maldonado, B.; Hussein, H.S.

    1994-12-31

    Due to the rectilinear nature of the previous 3D seismic survey, the details necessary for proper interpretation were absent. Theoretically, concentric 3D seismic technology may provide an avenue for gaining more and higher quality data coverage. Problems associated with recording a rectilinear 3D seismic grid over the salt dome in this area have created the need to investigate the use of such procedures as the concentric-circle 3D seismic acquisition technique. The difficulty of imaging salt dome flanks with conventional rectilinear 3D seismic may be a result of the inability to precisely predict the lateral velocity-field variation adjacent to both salt and sediments. The dramatic difference in the interval velocities of salt and sediments causes the returning ray to severely deviate from being a hyperbolic path. This hampers the ability to predict imaging points near the salt/sediment interface. Perhaps the most difficult areas to image with rectilinear seismic surveys are underneath salt overhangs. Modeling suggests that a significant increase in the number of rays captured from beneath a salt overhang can be achieved with the concentric-circle method. This paper demonstrates the use of the ``circle shoot`` on a survey conducted over a salt dome in the Gulf of Mexico. A total of 80 concentric circles cover an area which is equivalent to 31,000 acres. The final post-stack data were sorted into bins with dimensions of 25 meters by 25 meters. A comparison of 3D rectilinear shooting vs. 3D concentric circle shooting over the same area will show an improvement in data quality and signal-to-noise characteristics.

  20. 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.

  1. 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.

  2. 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.

  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. 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.

  5. Effects of Large and Small-Source Seismic Surveys on Marine Mammals and Sea Turtles

    NASA Astrophysics Data System (ADS)

    Holst, M.; Richardson, W. J.; Koski, W. R.; Smultea, M. A.; Haley, B.; Fitzgerald, M. W.; Rawson, M.

    2006-05-01

    L-DEO implements a marine mammal and sea turtle monitoring and mitigation program during its seismic surveys. The program consists of visual observations, mitigation, and/or passive acoustic monitoring (PAM). Mitigation includes ramp ups, powerdowns, and shutdowns of the seismic source if marine mammals or turtles are detected in or about to enter designated safety radii. Visual observations for marine mammals and turtles have taken place during all 11 L-DEO surveys since 2003, and PAM was done during five of those. Large sources were used during six cruises (10 to 20 airguns; 3050 to 8760 in3; PAM during four cruises). For two interpretable large-source surveys, densities of marine mammals were lower during seismic than non- seismic periods. During a shallow-water survey off Yucatán, delphinid densities during non-seismic periods were 19x higher than during seismic; however, this number is based on only 3 sightings during seismic and 11 sightings during non-seismic. During a Caribbean survey, densities were 1.4x higher during non-seismic. The mean closest point of approach (CPA) for delphinids for both cruises was significantly farther during seismic (1043 m) than during non-seismic (151 m) periods (Mann-Whitney U test, P < 0.001). Large whales were only seen during the Caribbean survey; mean CPA during seismic was 1722 m compared to 1539 m during non-seismic, but sample sizes were small. Acoustic detection rates with and without seismic were variable for three large-source surveys with PAM, with rates during seismic ranging from 1/3 to 6x those without seismic (n = 0 for fourth survey). The mean CPA for turtles was closer during non-seismic (139 m) than seismic (228 m) periods (P < 0.01). Small-source surveys used up to 6 airguns or 3 GI guns (75 to 1350 in3). During a Northwest Atlantic survey, delphinid densities during seismic and non-seismic were similar. However, in the Eastern Tropical Pacific, delphinid densities during non-seismic were 2x those during

  6. Ross Ice Shelf Seismic Survey and Future Drilling Recommendation

    NASA Astrophysics Data System (ADS)

    van Haastrecht, Laurine; Ohneiser, Christian; Gorman, Andrew; Hulbe, Christina

    2016-04-01

    The Ross Ice Shelf (RIS) is one of three gateways through which change in the ocean can be propagated into the interior of West Antarctica. Both the geologic record and ice sheet models indicate that it has experienced widespread retreat under past warm climates. But inland of the continental shelf, there are limited data available to validate the models. Understanding what controls the rate at which the ice shelf will respond to future climate change is central to making useful climate projections. Determining the retreat rate at the end of the last glacial maximum is one part of this challenge. In November 2015, four lines of multi-channel seismic data, totalling over 45 km, were collected on the Ross Ice Shelf, approximately 300 km south of Ross Island using a thumper seismic source and a 96 channel snow streamer. The seismic survey was undertaken under the New Zealand Antarctic Research Institute (NZARI) funded Aotearoa New Zealand Ross Ice Shelf Programme to resolve bathymetric details and to image sea floor sediments under a proposed drilling site on the ice shelf, at about 80.7 S and 174 E. The thumper, a purpose-built, trailer mounted, weight-drop seismic source was towed behind a Hägglund tracked vehicle to image the bathymetry and sediments underneath the RIS. Seismic data collection on an ice shelf has unique challenges, in particular strong attenuation of the seismic energy by snow and firn, and complex multiple ray paths. The thumper, which consists of a heavy weight (250kg) that is dropped on a large, ski mounted steel plate, produced a consistent, repeatable higher energy signal when compared to sledge hammer source and allowed for a greater geographic coverage and lower environmental impact than an explosive source survey. Our survey revealed that the seafloor is smooth and that there may be up to 100 m of layered sediments beneath the seafloor and possibly deeper, more complex structures. A multiple generated by internally reflected seismic energy

  7. Repeatability observations from a time-lapse seismic survey

    USGS Publications Warehouse

    Walters, S.L.; Miller, R.D.; Raef, A.E.

    2006-01-01

    Time-lapse seismic surveys have proven extremely valuable in recent years, having numerous economical and environmental applications. To fully utilize this monitoring technique, problems associated with recording repeatability must be minimized. Much work has been done to equalize data from one survey to the next via processing techniques (Huang et al., 1998). The purpose of this study is to investigate the potential for minimized processing, allowing study of extremely small changes in subsurface characteristics. The goal is to evaluate source and receiver terrain combination to optimize signal repeatability, and to improve deconvolution with the ground force to suppress different types of noise and increase repeatability. ?? 2005 Society of Exploration Geophysicists.

  8. Seismic monitoring at Deception Island volcano (Antarctica): the 2010-2011 survey

    NASA Astrophysics Data System (ADS)

    Martín, R.; Carmona, E.; Almendros, J.; Serrano, I.; Villaseñor, A.; Galeano, J.

    2012-04-01

    As an example of the recent advances introduced in seismic monitoring of Deception Island volcano (Antarctica) during recent years, we describe the instrumental network deployed during the 2010-2011 survey by the Instituto Andaluz de Geofísica of University of Granada, Spain (IAG-UGR). The period of operation extended from December 19, 2010 to March 5, 2011. We deployed a wireless seismic network composed by four three-component seismic stations. These stations are based on 24-bit SL04 SARA dataloggers sampling at 100 sps. They use a PC with embedded linux and SEISLOG data acquisition software. We use two types of three-component seismometers: short-period Mark L4C with natural frequency of 1 Hz and medium-period Lennartz3D/5s with natural frequency of 0.2 Hz. The network was designed for an optimum spatial coverage of the northern half of Deception, where a magma chamber has been reported. Station locations include the vicinity of the Spanish base "Gabriel de Castilla" (GdC), Obsidianas Beach, a zone near the craters from the 1970 eruptions, and the Chilean Shelter located south of Pendulum Cove. Continuous data from the local seismic network are received in real-time in the base by wifi transmission. We used Ubiquiti Networks Nanostation2 antennas with 2.4 GHz, dual-polarity, 10 dBi gain, and 54 Mbps transmission rate. They have shown a great robustness and speed for real-time applications. To prioritize data acquisition when the battery level is low, we have designed a circuit that allows independent power management for the seismic station and wireless transmission system. The reception antenna located at GdC is connected to a computer running SEISCOMP. This software supports several transmission protocols and manages the visualization and recording of seismic data, including the generation of summary plots to show the seismic activity. These twelve data channels are stored in miniseed format and displayed in real time, which allows for a rapid evaluation of

  9. Seismic Risk Assessment of Active Faults in Japan in Terms of Population Exposure to Seismic Intensity

    NASA Astrophysics Data System (ADS)

    Nojima, Nobuoto; Fujiwara, Hiroyuki; Morikawa, Nobuyuki; Ishikawa, Yutaka; Okumura, Toshihiko; Miyakoshi, Junichi

    This study evaluates and compares seismic risks associated with inland crustal earthquakes in Japan on the basis of published data available on the Japan Seismic Hazard Information Station (J-SHIS). First, taking account of prediction uncertainty of the attenuation law of seismic intensity, the evaluation method for population exposure (PEX) to seismic intensity is presented. The method is applied to 333 seismic events potentially caused by main active faults (154 cases) and other active faults (179 cases). The relationship between population exposure and the probability of occurrence of seismic events ("P-PEX relation") and the resultant seismic risk curves are obtained. Generalized risk index which incorporates the effects of focusing on urgency (probability) or significance (PEX) is defined, producing various risk rankings of active faults.

  10. Understanding the Long-Term Deformation in the Mississippi Embayment: the Mississippi River Seismic Survey

    NASA Astrophysics Data System (ADS)

    Magnani, M.; McIntosh, K.; Waldron, B.; Mitchell, L.; Saustrup, S.; Towle, M.

    2008-12-01

    The Central US hosts one of the most active intraplate seismic areas in the world, the New Madrid seismic zone (NMSZ). Here the high level of historic and instrumental seismicity clashes with the subdued topography of the Mississippi embayment, minimal geodetic vectors and a puzzling lack of substantial deformation in the post Late-Cretaceous sediments. To explain this apparent paradox it has been proposed that the seismicity in the NMSZ is either 1) very young (at least in its present form), 2) episodic, or 3) migrates throughout a broad region. In order to test these hypotheses and to understand how the deformation is partitioned within the Mississippi embayment, we collected a 300 km-long high-resolution seismic reflection profile along the Mississippi river, from Helena, Arkansas to Caruthersville, Missouri. The profile images a portion of the embayment outside the area of influence of the NMSZ in a region where evidence has been mounting of a seismic source, predating the NMSZ, for which no corresponding structure has yet been identified. The seismic survey exploited the advantages of marine acqui9sition (time effective, low cost) using a 245/245 cm3 (15/15 in3) mini-GI airgun fired at 13.790MPa (2000 psi), a 24-channel 75 m-long active streamer, with 3.125 m group and 12 m nominal shot interval. The high quality data image the Cretaceous and younger sedimentary section, from the top of the Paleozoic unconformity to the Quaternary deposits. Preliminary interpretation of the dataset confirms the general deepening of the Paleozoic basement from ~800 ms at Caruthersville, to ~1 s at the southern end of Crowley's Ridge. In addition, the data reveal prominent recent deformation coincident with the Blytheville arch, the Eastern Reelfoot Rift margin and the White river Fault zone, accommodated by folding and faulting that extend from the top of the Paleozoic through the sedimentary section, and that involves the Quaternary deposits.

  11. 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.

  12. A seismic survey in Antarctica, parallel schemes for seismic migration and target oriented velocity analysis

    NASA Astrophysics Data System (ADS)

    Sen, Vikramaditya

    This dissertation comprises three different studies. The first part describes the acquisition and data processing techniques utilized during a seismic survey conducted in the austral summer of 1994--95 in the interior of Antarctica. Three multichannel seismic reflection profiles and two wide-angle profiles were collected over the central-west Antarctica ice sheet to investigate methods to obtain a shallow to mid-crustal section of the lithosphere below the Byrd subglacial basin. The multichannel seismic data were analysed to develop images of the shallow crustal structure, the base of ice, and intra-ice reflections that (with minor exceptions) conform to the ice-floor topography. The high energy, low frequency seismic energy generated by the larger charges of the wide angle data was more successful in imaging the deep crustal section. The upper crust in this area was determined to be fairly non-reflective. Along the main traverse, the base of ice has significant topographical undulation in both inline and crossline directions and several half grabens and localized basins can be identified. More efficient surveys can be conducted and better signal quality can be obtained by using longer streamers (˜4.5 km) and larger and buried charges. The second part describes a parallel implementation of 3D pre-stack Kirchhoff depth migration using the Parallel Virtual Machine (PVM) environment of message passing and clustering. A simple yet robust strategy has been proposed to distribute the computation load among the nodes of a virtual parallel machine and the performance of the parallel method has been compared with conventional sequential schemes. A near linear speedup was achieved in this implementation which implies that the reduction in computation time (compared to the sequential run time) was almost directly proportional to the number of nodes in the virtual machine. The third part of this dissertation describes an approach for target oriented migration velocity

  13. 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.

  14. 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. 

  15. 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

  16. Seismic activity in the Transantarctic Mountains recorded by the TAMSEIS seismic array.

    NASA Astrophysics Data System (ADS)

    Anandakrishnan, S.; Stapley, N.; Lawrence, J. F.; Winberry, J. P.; Shore, P. J.; Voigt, D. E.; Wiens, D.; Nyblade, A.

    2004-12-01

    To investigate the links between glaciation and tectonics, we conducted a large-scale seismic deployment in Antarctica that measured local and regional seismicity of both the glaciated terrain of East Antarctica and the non-glaciated Transantarctic Mountains (TAM). The TAM are hypothesized to have formed by rift-flank uplift of the southwestern margin of the West Antarctic Rift System. Active extension of this rift and/or continued uplift of the TAM would likely result in relatively high levels of seismicity along the mountain front. In addition to seismicity from tectonic activity, we suggest that the flow of glaciers, particularly where they accelerate through the TAM, could result in glacier-induced seismicity. We recorded relatively high levels of local seismicity in the TAM. The majority of the seismicity was close to and slightly west of the TAM, beneath the East Antarctic Ice Sheet. We used the double-difference hypocenter location method (Waldhauser and Ellsworth, 2000; Waldhauser 2001) to better image clusters of events. Many of the events are shallow and cluster beneath the David Glacier (which leads to the Drygalski Ice Tongue) and the Darwin Glacier. We suggest that these events are due to fracture at the base of the glaciers, as they steepen towards the coast. We continue to investigate the possibility of surface crevassing and TAM uplift-induced seismicity (along faults which the glaciers have exploited) as the cause of the seismicity.

  17. Sound source localization technique using a seismic streamer and its extension for whale localization during seismic surveys.

    PubMed

    Abadi, Shima H; Wilcock, William S D; Tolstoy, Maya; Crone, Timothy J; Carbotte, Suzanne M

    2015-12-01

    Marine seismic surveys are under increasing scrutiny because of concern that they may disturb or otherwise harm marine mammals and impede their communications. Most of the energy from seismic surveys is low frequency, so concerns are particularly focused on baleen whales. Extensive mitigation efforts accompany seismic surveys, including visual and acoustic monitoring, but the possibility remains that not all animals in an area can be observed and located. One potential way to improve mitigation efforts is to utilize the seismic hydrophone streamer to detect and locate calling baleen whales. This study describes a method to localize low frequency sound sources with data recoded by a streamer. Beamforming is used to estimate the angle of arriving energy relative to sub-arrays of the streamer which constrains the horizontal propagation velocity to each sub-array for a given trial location. A grid search method is then used to minimize the time residual for relative arrival times along the streamer estimated by cross correlation. Results from both simulation and experiment are shown and data from the marine mammal observers and the passive acoustic monitoring conducted simultaneously with the seismic survey are used to verify the analysis.

  18. A western gray whale mitigation and monitoring program for a 3-D seismic survey, Sakhalin Island, Russia.

    PubMed

    Johnson, S R; Richardson, W J; Yazvenko, S B; Blokhin, S A; Gailey, G; Jenkerson, M R; Meier, S K; Melton, H R; Newcomer, M W; Perlov, A S; Rutenko, S A; Würsig, B; Martin, C R; Egging, D E

    2007-11-01

    The introduction of anthropogenic sounds into the marine environment can impact some marine mammals. Impacts can be greatly reduced if appropriate mitigation measures and monitoring are implemented. This paper concerns such measures undertaken by Exxon Neftegas Limited, as operator of the Sakhalin-1 Consortium, during the Odoptu 3-D seismic survey conducted during 17 August-9 September 2001. The key environmental issue was protection of the critically endangered western gray whale (Eschrichtius robustus), which feeds in summer and fall primarily in the Piltun feeding area off northeast Sakhalin Island. Existing mitigation and monitoring practices for seismic surveys in other jurisdictions were evaluated to identify best practices for reducing impacts on feeding activity by western gray whales. Two buffer zones were established to protect whales from physical injury or undue disturbance during feeding. A 1 km buffer protected all whales from exposure to levels of sound energy potentially capable of producing physical injury. A 4-5 km buffer was established to avoid displacing western gray whales from feeding areas. Trained Marine Mammal Observers (MMOs) on the seismic ship Nordic Explorer had the authority to shut down the air guns if whales were sighted within these buffers. Additional mitigation measures were also incorporated: Temporal mitigation was provided by rescheduling the program from June-August to August-September to avoid interference with spring arrival of migrating gray whales. The survey area was reduced by 19% to avoid certain waters <20 m deep where feeding whales concentrated and where seismic acquisition was a lower priority. The number of air guns and total volume of the air guns were reduced by about half (from 28 to 14 air guns and from 3,390 in(3) to 1,640 in(3)) relative to initial plans. "Ramp-up" (="soft-start") procedures were implemented. Monitoring activities were conducted as needed to implement some mitigation measures, and to assess

  19. Three-axis accelerometer package for slimhole and microhole seismic monitoring and surveys

    SciTech Connect

    Hunter, S.L.; Harben, P.E.

    1997-01-07

    The development of microdrilling technology, nominally defined as drilling technology for 1-in.-diameter boreholes, shows potential for reducing the cost of drilling monitoring wells. A major question that arises in drilling microholes is if downhole logging and monitoring in general--and downhole seismic surveying in particular--can be conducted in such small holes since the inner working diameter of such a seismic tool could be as small as 0.31 in. A downhole three-component accelerometer package that fits within a 031-in. inner diameter tube has been designed, built, and tested. The package consists of three orthogonally mounted Entran EGA-125-5g piezoresistive silicon micromachined accelerometers with temperature compensation circuitry, downhole amplification, and line drivers mounted in a thin-walled aluminum tube. Accelerometers are commercially available in much smaller package sizes than conventional geophones, but the noise floor is significantly higher than that for the geophones. Cross-well tests using small explosives showed good signal-to-noise ratio in the recorded waveform at various receiver depths with a 1,50-ft source-receiver well separation. For some active downhole surveys, the accelerometer unit would clearly be adequate. It can be reasonably assumed, however, that for less energetic sources and for greater well separations, the high accelerometer noise floor is not acceptable. By expanding the inner working diameter of a microhole seismic tool to 0.5 in., other commercial accelerometers can be used with substantially lower noise floors.

  20. Shallow Seismic Reflection Survey at Garner Valley Digital Array

    NASA Astrophysics Data System (ADS)

    Lawrence, Z. S.; Brackman, T. B.; Bodin, P.; Stephenson, W. J.; Steidl, J. H.; Gomberg, J.

    2004-12-01

    The Garner Valley Digital Array (GVDA) site is a NEES-sponsored facility in a small, sediment-filled, intermountain valley in Southern California, established for the purpose of investigating ground motion site response and soil-structure interaction, in situ. The site has been well-characterized geotechnically, and is thoroughly instrumented with both surface and downhole instrumentation of various types. Nevertheless, a borehole recently drilled into lake bed sediments and deeply weathered granitic rocks that comprise the valley fill at GVDA encountered hard, unweathered bedrock at an unexpected depth, suggesting an apparent 38 meter offset in the unweathered bedrock between two wells 40 meters apart. The apparent offset can be most easily explained either by faulting, or as a buried erosional surface. The Hot Springs fault, a strand of the San Jacinto fault zone, runs through Garner Valley, although its inferred location is several hundred meters east of GVDA. To better characterize the subsurface strata, particularly the existence and configuration of faulting that may disturb them; we conducted a 120-meter long, 12-fold shallow seismic reflection common midpoint (CMP) survey at GVDA using a 24-channel seismograph, vertical 4.5 Hz geophones at 2-meter intervals and a sledgehammer seismic source. Preliminary processing reveals strong refractors and surface waves that may mask reflections, although reflections are visible in some raw shot records. Semi-continuous reflections seen in the CMP section from a shallow reflector may coincide with the water table. There are also deeper, discontinuous reflectors obscured by bands of coherent noise. We plan to present a fully migrated and interpreted CMP record section.

  1. Erosion influences the seismicity of active thrust faults.

    PubMed

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

    2014-11-21

    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.

  2. 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.

  3. Review of the Effects of Offshore Seismic Surveys in Cetaceans: Are Mass Strandings a Possibility?

    PubMed

    Castellote, Manuel; Llorens, Carlos

    2016-01-01

    Displacement of cetaceans is commonly reported during offshore seismic surveys. Speculation concerning possible links between seismic survey noise and cetacean strandings is available for a dozen events but without convincing causal evidence. This lack of evidence should not be considered conclusive but rather as reflecting the absence of a comprehensive analysis of the circumstances. Current mitigation guidelines are inadequate for long-range effects such as displacements and the potential for strandings. This review presents the available information for ten documented strandings that were possibly linked to seismic surveys and recommends initial measures and actions to further evaluate this potential link.

  4. 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

  5. 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

  6. 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.

  7. Near-surface velocity structure from borehole and refraction seismic surveys

    SciTech Connect

    Parry, D.; Lawton, D.C.

    1994-12-31

    Seismic refraction and borehole reflection data have been used in conjunction with other geophysical tools to characterize the near-surface geology in the vicinity of a shallow well near Calgary, Alberta. The investigated section is comprised primarily of glacial tills and gravels. Seismic waves generated in the lower gravel units travel as compressional waves up to the till/gravel interface, where they are converted to shear waves upon transmission. Velocity structure from a reverse vertical seismic profile (RVSP) survey agrees closely with that from refraction surveying.

  8. Vertical Cable Seismic Survey for SMS Exploration in Izena Cauldron, Okinawa-Trough

    NASA Astrophysics Data System (ADS)

    Asakawa, E.; Murakami, F.; Tsukahara, H.; Mizohata, S.; Tara, K.

    2014-12-01

    The VCS survey is one of the reflection seismic methods. It uses hydrophone arrays vertically moored from the seafloor to record acoustic waves generated by seismic sources. Because the VCS is an efficient high-resolution 3D seismic survey method for a spatially-bounded area, we proposed it for the SMS survey tool development program started by Japanese government. In 2010, we manufactured the autonomous VCS data acquisition systems. Through several experimental surveys, our VCS is successfully completed. In 2011 and 2013, we carried out the two VCS surveys using GI gun and high-voltage sparker respectively in the Izena Cauldron, Okinawa Trough, which is one of the most promising SMS areas around Japan. Because seismic survey is not proven to be effective for SMS exploration, no seismic surveys have been conducted there so far. Our strategy for SMS exploration consists of two stages. In the first stage, we carried out VCS survey with the lower frequency GI gun (but higher compared to the convebtional oil/gas exploration) and explored deeper (up to 1,500m) structure to obtain the fault system of hydrothermal flow. Next, using a high frequency (about 1 kHz higher) and high-voltage sparker, we explored very shallow (up to 200m) part to delineate the very thin SMS deposits. These two VCS dataset have been processed with 3D Prestack Depth Migration. These results are consistent with geological information from the borehole drilled nearby and give useful information to SMS exploration.

  9. 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.

  10. 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

  11. Pen Branch fault program: Interim report on the High Resolution, Shallow Seismic Reflection surveys

    SciTech Connect

    Stieve, A.L.

    1991-01-31

    The Pen Branch fault was identified in the subsurface at the Savannah River Site in 1989 based upon the interpretation of earlier seismic reflection surveys and other geologic investigations. A program was initiated at that time to further define the fault in terms of its capability to release seismic energy. The High-Resolution, Shallow Seismic Reflection survey recently completed at SRS was initiated to determine the shallowest extent of the fault and to demonstrate the presence of flat-lying sediments in the top 300 feet of sediments. Conclusions at this time are based upon this shallow seismic survey and the Conoco deep seismic survey (1988--1989). Deformation related to the Pen Branch fault is at least 200 milliseconds beneath the surface in the Conoco data and at least 150 milliseconds in the shallow seismic reflection data. This corresponds to approximately 300 feet below the surface. Sediments at that depth are lower Tertiary (Danian stage) or over 60 million years old. This indicates that the fault is not capable.

  12. First results of a high resolution reflection seismic survey of the Central Northern Venezuelan Shelf

    NASA Astrophysics Data System (ADS)

    Avila, J.; van Welden, A.; Audemard, F.; de Batist, M.; Beck, C.; Scientific Party, G.

    2008-05-01

    In September - November 2007 the first high resolution marine seismic campaign on the North-Central coast of Venezuela was carried out between Cabo Codera and Golfo Triste. The principal aim of this work was to characterize the active San Sebastian Fault (SSF) and to analyze Cenozoic sedimentation on the Venezuela shelf focusing on: i) effects of active tectonics and ii) coastal landslides/flashflood deposits related to 1999 Vargas catastrophic event or to similar phenomena. Data were acquired onboard R/V GUAIQUERI II from the Oceanographic Institute of the Oriente University. The seismic source was a "CENTIPEDE" sparker (RCGM) operated between 300 and 600 J, 1.3 kHz main frequency. We used a single-channel streamer with 10 hydrophones. In total, 49 seismic profiles were collected, with a cumulative length of 1000 km approximately. In these seismic profiles we identified and separated the deposits into three main units. Unit (U1) comprises low energy reflectors mainly dipping in southward direction (i.e. toward the coast bounded by the San Sebastian Fault). This unit also includes a number of isolated acoustic anomalies, which we tentatively interpret as coral reefs. Its top is defined as Basal Erosional Discontinuity (BED) onto which Unit 2 (U2) deposits are onlapping. U2 is acoustically well-stratified, with strong reflectors. Gradual variations in thickness and a wavy configuration allow us to interpret U2 as probably Quaternary current-related deposits. Last Unit (U3) was defined on the Venezuela shelf and corresponds to prograding sequences probably related to the terrigenous input of the Tuy River. Impact of eustatic fluctuations on these deposits are discussed. The data were also used to construct a simplified bathymetry of the studied area. The lateral transition from the western Cariaco-Tuy pull-apart basin to the (single) SSF was clearly imaged (mostly folds and gravity faults). The survey also displayed prograding sediments bodies in La Tortuga Shelf

  13. A Three-dimensional Reflection Seismic Survey In The Earstern Nankai Accretionary Prism.

    NASA Astrophysics Data System (ADS)

    Ike, T.; Tokuyama, H.; Kuramoto, S.; Matsushima, J.; Yokota, T.; Pascal, G.; Lalememant, S.

    The Three-Dimensional Multi-Channel Seismic (3D-MCS) reflection survey using a tuned air gun source was held in the eastern Nankai accretionary prism from June to July 2000. The crustal deformation of the eastern Nankai accretionary prism is affected by a nearby collision between the Izu-Bonin arc and the central Japan. Sev- eral active fault systems were described by many high-resolution seismic data, and proposed that the Tokai and Kodaiba fault systems were derived from a decollement plane. From the deformation style in the Nankai Trough, we concern about the oc- currence of a great earthquake in recent years. The main objective of our experiment is to resolve the structural image of the plate boundary and identify the up-dip limit of seismogenic zone. The 3-D survey covers 45km long and 5km wide area with 51 seismic lines, located about 50km southwest from Omaezaki. We applied the non- iterative Kirchhoff pre-stack time migration method (Matsushima et.,al 2001) with stacking velocity analysis to our 3-D data. The derived 3-D prestack time migra- tion profile shows a better development at the deep structure on the top of oceanic crust, compared with preliminary 2-D prestack time migration processed profile. The processed 3-D data gives us a significantly clear image of the thrust faults and the relationship between sediment deformation and thrust activity. A preliminary 3-D in- terpretation was conducted and leaded the following results.1) The Tokai and Kodaiba thrusts are confirmed to be sets of out-of-sequence thrusts. 2) Both thrusts are ac- tive fault that revealed by the structure of the deformation of surface sediments. 3) A strong and low frequency reflector can be identified in the entire profile at two-way- time 7-7.5sec that should be a decollement plane. 4)Tokai and Kodaiba fault systems merged to the decollement plane at same depth. The contact area of the thrust faults to the decollement corresponds to south end of seismic coupling region presumed

  14. Seismic activity of the San Francisco Bay region

    USGS Publications Warehouse

    Bakun, W.H.

    1999-01-01

    Moment magnitude M with objective confidence-level uncertainties are estimated for felt San Francisco Bay region earthquakes using Bakun and Wentworth's (1997) analysis strategy for seismic intensity observations. The frequency-magnitude distribution is well described for M ???5.5 events since 1850 by a Gutenberg-Richter relation with a b-value of 0.90. The seismic moment rate ??M0/yr since 1836 is 2.68 X 1018 N-m/yr (95% confidence range = 1.29 X 1018 N-m/yr to 4.07 X 1018 N-m/yr); the seismic moment rate since 1850 is nearly the same. ??M0/yr in the 56 years before 1906 is about 10 times that in the 70 years after 1906. In contrast, ??M0/yr since 1977 is about equal that in the 56 years before 1906. 80% (1?? = 14%) of the plate-motion moment accumulation rate is available for release in earthquakes. The historical ??M0/yr and the portion of the plate-motion moment accumulation rate available for release in earthquakes are used in a seismic cycle model to estimate the rate of seismic activity in the twenty-first century. High and low rates of future seismic activity are both permissible given the range of possible seismic-cycle recurrence times T and the uncertainties in the historical ??M0 and in the percentage of plate motion available for release in earthquakes. If the historical seismic moment rate is not greater than the estimated 2.68 X 1018 N-m/yr and the percentage of the plate-motion moment accumulation available for release in earthquakes is not less than the estimated 80%, then for all T, the rate of seismic moment release from now until the next 1906-sized shock will be comparable to the rate from 1836 to 1905 when M 6 1/2 shocks occurred every 15 to 20 years.

  15. A combined surface and borehole seismic survey at the COSC-1 borehole

    NASA Astrophysics Data System (ADS)

    Simon, Helge; Krauß, Felix; Hedin, Peter; Buske, Stefan; Giese, Rüdiger; Juhlin, Christopher

    2015-04-01

    The ICDP project COSC (Collisional Orogeny in the Scandinavian Caledonides) focuses on the mid Paleozoic Caledonide Orogen in Scandinavia in order to better understand orogenic processes, from the past and in recent active mountain belts. The Scandinavian Caledonides provide a well preserved example of a Paleozoic continent-continent collision. Surface geology in combination with geophysical data provide control of the geometry of the Caledonian structure, including the allochthon and the underlying autochthon, as well as the shallow W-dipping décollement surface that separates the two and consist of a thin skin of Cambrian black shales. During spring/summer 2014 the COSC-1 borehole was drilled to approx. 2.5 km depth near the town of Åre (western Jämtland/Sweden) with nearly 100 % of core recovery and cores in best quality. After the drilling was finished, a major seismic survey was conducted in and around the COSC-1 borehole which comprised both seismic reflection and transmission experiments. Besides a high resolution zero-offset VSP (Vertical Seismic Profiling) experiment also a multi-azimuthal walkaway VSP survey took place. For the latter the source points were distributed along three profile lines centered radially around the borehole. For the central part up to 2.5 km away from the borehole, a hydraulic hammer source was used, which hits the ground for about 20 s with an linear increasing hit rate. For the far offset shots up to 5 km, explosive sources were used. The wavefield of both source types was recorded in the borehole using an array of 15 three-component receivers with a geophone spacing of 10 m. This array was deployed at 7 different depth levels during the survey. At the same time the wavefield was also recorded at the surface by 180 standalone three-component receivers placed along each of the three up to 10 km long lines, as well as with a 3D array of single-component receivers in the central part of the survey area around the borehole. Here

  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. Seismic Activity offshore Martinique and Dominique islands (Lesser Antilles subduction zone)

    NASA Astrophysics Data System (ADS)

    Ruiz Fernandez, Mario; Galve, Audrey; Monfret, Tony; Charvis, Philippe; Laigle, Mireille; Flueh, Ernst; Gallart, Josep; Hello, Yann

    2010-05-01

    In the framework of the European project Thales was Right, two seismic surveys (Sismantilles II and Obsantilles) were carried out to better constrain the lithospheric structure of the Lesser Antilles subduction zone, its seismic activity and to evaluate the associated seismic hazards. Sismantilles II experiment was conducted in January, 2007 onboard R/V Atalante (IFREMER). A total of 90 OBS belonging to Géoazur, INSU-CNRS and IFM-Geomar were deployed on a regular grid, offshore Antigua, Guadeloupe, Dominique and Martinique islands. During the active part of the survey, more than 2500 km of multichannel seismic profiles were shot along the grid lines. Then the OBS remained on the seafloor continuously recording for the seismic activity for approximately 4 months. On April 2007 Obsantilles experiment, carried out onboard R/V Antea (IRD), was focused on the recovery of those OBS and the redeployment of 28 instruments (Géoazur OBS) off Martinique and Dominica Islands for 4 additional months of continuous recording of the seismicity. This work focuses on the analysis of the seismological data recorded in the southern sector of the study area, offshore Martinique and Dominique. During the two recording periods, extending from January to the end of August 2007, more than 3300 seismic events were detected in this area. Approximately 1100 earthquakes had enough quality to be correctly located. Station corrections, obtained from multichannel seismic profiles, were introduced to each OBS to take in to account the sedimentary cover and better constrain the hypocentral determinations. Results show events located at shallower depths in the northern sector of the array, close to the Tiburon Ridge, where the seismic activity is mainly located between 20 to 40 km depth. In the southern sector, offshore Martinique, hypocenters become deeper, ranging to 60 km depth and dipping to the west. Focal solutions have also been obtained using the P wave polarities of the best azimuthally

  18. Tectonics Of Eastern Offshore Trinidad Based On Integration Of BOLIVAR 2D Seismic Lines With Industry 3D Seismic Surveys

    NASA Astrophysics Data System (ADS)

    Soto, M. D.; Mann, P.; Wood, L. J.

    2004-12-01

    New MCS lines in the eastern offshore area of Trinidad augmented by existing 3D seismic surveys by industry provide new insights into complex, strain partitioning produced along this segment of the South America-Caribbean plate boundary. Two major tectonosequences are imaged separated by a Middle Miocene angular unconformity known from wells and mapping in Trinidad. A thick section of deep-marine carbonate and clastic rocks are cleanly truncated by the Middle Miocene unconformity and are chaotically deformed along vertical to northwest-dipping thrust faults. This shortening event reflects a major pulse of pre-Middle Miocene southeastward overthrusting of the Caribbean arc over the passive margin of South America. An upper 2-7-km-thick tectonosequence consisting of late Miocene-Quaternary shelf-related sandstone and shale was deposited by the nearby Orinoco delta. This section is folded to lesser degree and deformed by the sub-vertical, right-lateral Central Range fault zone (CRFZ), known from GPS studies to accommodate 12 mm/yr, of the total 20 mm/yr of interplate motion. Deep, continuous reflec-tors are observed at a depth of 12-17 km beneath eastern Trinidad are correlated with authochthonous, late Cretaceous-early Tertiary carbonate and clastic rocks of the South American passive margin. The Darien fault southeast of the CRFZ accommodates active shortening, elevates passive margin rocks to the surface in Trinidad, and forms the northeastern limit of a large, 12-km-thick foreland basin (Columbus basin) that extends onshore.

  19. The Salton Seismic Imaging Project (SSIP): Active Rift Processes in the Brawley Seismic Zone

    NASA Astrophysics Data System (ADS)

    Han, L.; Hole, J. A.; Stock, J. M.; Fuis, G. S.; Rymer, M. J.; Driscoll, N. W.; Kent, G.; Harding, A. J.; Gonzalez-Fernandez, A.; Lazaro-Mancilla, O.

    2011-12-01

    The Salton Seismic Imaging Project (SSIP), funded by NSF and USGS, acquired seismic data in and across the Salton Trough in southern California and northern Mexico in March 2011. The project addresses both rifting processes at the northern end of the Gulf of California extensional province and earthquake hazards at the southern end of the San Andreas Fault system. Seven lines of onshore refraction and low-fold reflection data were acquired in the Coachella, Imperial, and Mexicali Valleys, two lines and a grid of airgun and OBS data were acquired in the Salton Sea, and onshore-offshore data were recorded. Almost 2800 land seismometers and 50 OBS's were used in almost 5000 deployments at almost 4300 sites, in spacing as dense as 100 m. These instruments received seismic signals from 126 explosive shots up to 1400 kg and over 2300 airgun shots. In the central Salton Trough, North American lithosphere appears to have been rifted completely apart. Based primarily on a 1979 seismic refraction project, the 20-22 km thick crust is apparently composed entirely of new crust added by magmatism from below and sedimentation from above. Active rifting of this new crust is manifested by shallow (<10km depth) seismicity in the oblique Brawley Seismic Zone (BSZ), small Salton Buttes volcanoes aligned perpendicular to the transform faults, very high heat flow (~140 mW/m2), and geothermal energy production. This presentation is focused on an onshore-offshore line of densely sampled refraction and low-fold reflection data that crosses the Brawley Seismic Zone and Salton Buttes in the direction of plate motion. At the time of abstract submission, data analysis was very preliminary, consisting of first-arrival tomography of the onshore half of the line for upper crustal seismic velocity. Crystalline basement (>5 km/s), comprised of late-Pliocene to Quaternary sediment metamorphosed by the high heat flow, occurs at ~2 km depth beneath the Salton Buttes and geothermal field and ~4 km

  20. 3-Component Reflection Seismic Survey Across the Seismogenic Coupling Zone in Chile (Project TIPTEQ)

    NASA Astrophysics Data System (ADS)

    Micksch, U.; Gross, K.; Buske, S.; Krawczyk, C. M.; Stiller, M.; Wigger, P.; Araneda, M.; Bataille, K.; Bribach, J.; Lüth, S.; Mechie, J.; Schulze, A.; Shapiro, S. A.; Ziegenhagen, T.

    2005-12-01

    The TIPTEQ project (from The Incoming Plate to mega-Thrust EarthQuake processes) studies processes which generate mega-thrust earthquakes at convergent plate margins, with the Chilean subduction zone as natural laboratory. The seismogenic coupling zones at convergent margin plate interfaces harbour some 90% of the global seismicity, and in the case of Chile, the hypocenter of the largest historically recorded earthquake in 1960 (Mw = 9.5). The rupture started at 38° S with a hypocentral depth of some 30 km below the continental forearc and continued towards the south for approximately 1000 km. The active seismic experiment component of TIPTEQ crosses the 1960 earthquake hypocenter. The survey consists of a 95 km long near-vertical reflection seismic profile shot in January 2005. 180 three-component geophones were deployed along an 18 km long spread, moving 4.5 km in a daily roll-along. Explosive shots, with a spacing of 1.5 km, allow an up to 8-fold CDP coverage. The W-E trending line runs across part of the Central Valley and continues over the coastal cordillera towards the Pacific. The seismic line shows good reflectivity and internal structures of the accretionary wedge and the plate interface. The down-going plate is clearly visible at c. 8 s TWT near the coast, reaching 17 s TWT at the eastern end of the profile. Two more experiment configurations were applied in addition: An expanding spread profiling setup aims at the down-dip limit of the seismogenic coupling zone at 30-50 km depth to image the hypocenter of the 1960 earthquake in more detail (10-fold coverage); a SH experiment configuration (1-fold coverage) served as a pilot study to test SH-wave generation in a crustal regime. Using the three component data, S-wave images could yield an improved picture of the petrophysical contrasts within the subduction zone. We present the results from poststack- and prestack-migration of the near-vertical reflection experiment, as well as a first interpretation of

  1. Fault and dyke detectability in high resolution seismic surveys for coal: a view from numerical modelling*

    NASA Astrophysics Data System (ADS)

    Zhou, Binzhong 13Hatherly, Peter

    2014-10-01

    Modern underground coal mining requires certainty about geological faults, dykes and other structural features. Faults with throws of even just a few metres can create safety issues and lead to costly delays in mine production. In this paper, we use numerical modelling in an ideal, noise-free environment with homogeneous layering to investigate the detectability of small faults by seismic reflection surveying. If the layering is horizontal, faults with throws of 1/8 of the wavelength should be detectable in a 2D survey. In a coal mining setting where the seismic velocity of the overburden ranges from 3000 m/s to 4000 m/s and the dominant seismic frequency is ~100 Hz, this corresponds to a fault with a throw of 4-5 m. However, if the layers are dipping or folded, the faults may be more difficult to detect, especially when their throws oppose the trend of the background structure. In the case of 3D seismic surveying we suggest that faults with throws as small as 1/16 of wavelength (2-2.5 m) can be detectable because of the benefits offered by computer-aided horizon identification and the improved spatial coherence in 3D seismic surveys. With dykes, we find that Berkhout's definition of the Fresnel zone is more consistent with actual experience. At a depth of 500 m, which is typically encountered in coal mining, and a 100 Hz dominant seismic frequency, dykes less than 8 m in width are undetectable, even after migration.

  2. Geothermal Potential of the Siǧacik Gulf (Seferihisar) and Preliminary investigations with Seismic and Magnetic Surveys

    NASA Astrophysics Data System (ADS)

    Bakak, Özde; Özel, Erdeniz; Ergün, Mustafa

    2015-04-01

    . Penetration depth is maximum 90 meter from the seafloor. The seismic sections reveal both the lens structures represented as current accumulation areas, and deformation areas located in upper unit. At the same time, the marine magnetic survey was applied using SDM 4000 magnetometer of Shark Marine Technologies Company. The magnetic measurements were collected along the same seismic lines, and magnetic anomaly map shows the low magnetic anomaly value which is between -50nT and -90 nT, in east of Sığacık Gulf. In the light of shallow seismic and magnetic surveys, it is thought that the east of gulf may have geothermal activity on seafloor.

  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. Predictive habitat modelling of humpback (Megaptera novaeangliae) and Antarctic minke (Balaenoptera bonaerensis) whales in the Southern Ocean as a planning tool for seismic surveys

    NASA Astrophysics Data System (ADS)

    Bombosch, Annette; Zitterbart, Daniel P.; Van Opzeeland, Ilse; Frickenhaus, Stephan; Burkhardt, Elke; Wisz, Mary S.; Boebel, Olaf

    2014-09-01

    Seismic surveys are frequently a matter of concern regarding their potentially negative impacts on marine mammals. In the Southern Ocean, which provides a critical habitat for several endangered cetacean species, seismic research activities are undertaken at a circumpolar scale. In order to minimize impacts of these surveys, pre-cruise planning requires detailed, spatio-temporally resolved knowledge on the likelihood of encountering these species in the survey area. In this publication we present predictive habitat modelling as a potential tool to support decisions for survey planning. We associated opportunistic sightings (2005-2011) of humpback (Megaptera novaeangliae, N=93) and Antarctic minke whales (Balaenoptera bonaerensis, N=139) with a range of static and dynamic environmental variables. A maximum entropy algorithm (Maxent) was used to develop habitat models and to calculate daily basinwide/circumpolar prediction maps to evaluate how species-specific habitat conditions evolved throughout the spring and summer months. For both species, prediction maps revealed considerable changes in habitat suitability throughout the season. Suitable humpback whale habitat occurred predominantly in ice-free areas, expanding southwards with the retreating sea ice edge, whereas suitable Antarctic minke whale habitat was consistently predicted within sea ice covered areas. Daily, large-scale prediction maps provide a valuable tool to design layout and timing of seismic surveys as they allow the identification and consideration of potential spatio-temporal hotspots to minimize potential impacts of seismic surveys on Antarctic cetacean species.

  5. U. S. Geological Survey begins seismic ground response experiments in Washington State

    USGS Publications Warehouse

    Tarr, A.C.; King, K.W.

    1987-01-01

    The men were Denver-based U.S Geological Survey (USGS) geophysicists working on the Urban Hazards Field Investigations project. On the previous day they had recorded two events on their seismographs-a distant nuclear explosion in Nevada and a blast at amine near Centralia, Washington. On another day, they used seismic refraction equipment to locate the depth of bedrock and seismic velocity to it at several locations in West Seattle and in the Seward Park-Brighton district of southeast Seattle. 

  6. High-resolution seismic reflection survey near SPR surface collapse feature at Weeks Island, Louisiana

    SciTech Connect

    Miller, R.D.; Xia, J.; Harding, R.S. Jr.; Steeples, D.W.

    1994-12-31

    Shallow high resolution 2-D and 3-D seismic reflection techniques are assisting in the subsurface delineation of a surface collapse feature (sinkhole) at Weeks Island, Louisiana. Seismic reflection surveys were conducted in March 1994. Data from walkaway noise tests were used to assist selection of field recording parameters. The top of the salt dome is about 180 ft below ground surface at the sinkhole. The water table is an estimated 90 ft below the ground surface. A single coherent reflection was consistently recorded across the entire area of the survey, although stacking velocity and spectral content of the event varied. On the basis of observed travel times and stacking velocities, the coherent reflection event appears to originate above the top of the salt, possibly at or near the water table. Identification of this reflector will be made form borehole investigations currently planned for the sinkhole site. A depression or time sag in this reflection event is clearly evident in both the 2-D and 3-D seismic data in the immediate vicinity of the sinkhole. The time sag appears to be related to the subsurface structure of the reflector and not to near surface topography or velocity effects. Elsewhere in the survey area, observed changes in reflection travel times and wavelet character appear to be related to subsurface geologic structure. These seismic observations may assist in predicting where future sinkholes will develop after they have been tied to borehole data collected at the site.

  7. Suspended ceiling system survey and seismic bracing recommendations for Lawrence Livermore National Laboratory

    SciTech Connect

    Not Available

    1985-08-01

    In response to the Laboratory's concern that suspended ceilings, installed without proper engineering consideration for earthquake resistance, can be potential source of damage, LLNL commissioned ED2 International Architects and Planners to provide a guide and survey for the installation commercially available suspended ceiling systems. The Survey was to include select ceiling types, their relative costs, and recommendations for seismic design. This Survey is in the format of a handbook with seven major headings: Generic types of suspended ceiling systems; functional comparative analysis of the various system; relative costs of the various ceiling systems; seismic considerations and recommendations; detailed drawings and suggested methods of assembly; code references; and listing of material suppliers, representatives, and available product lines and selection check lists.

  8. Suspended ceiling system survey and seismic bracing recommendations for Lawrence Livermore National Laboratory

    SciTech Connect

    Not Available

    1985-08-01

    In response to the Laboratory's concern that suspended ceilings, installed without proper engineering consideration for earthquake resistance, can be potential source of damage, LLNL commissioned ED2 International Architects and Planners to provide a guide and survey for the installation commercially available suspended ceiling systems. The Survey was to include select ceiling types, their relative costs, and recommendations for seismic design. This Survey is in the format of a handbook with seven major headings: Generic types of suspended ceiling systems; Functional Comparative Analysis of the various systems; Relative costs of various ceiling systems; Seismic considerations and recommendations; Detailed drawings and suggested methods of assembly; Code References; and Listing of Material Suppliers, representatives, and available product lines and selection check lists.

  9. Seismic reflection survey in the geothermal field of the Rotorua Caldera, New Zealand

    SciTech Connect

    Lamarche, G. )

    1992-04-01

    This paper discusses a seismic reflection survey conducted in the southern part of the Rotorua geothermal field (New Zealand). Geological structures were interpreted along the two profiles to a depth of about 300 m. A seismic image of the Mamaku Ignimbrite is obtained and appears to show normal faulting. Depth of the top of the Mamaku Ignimbrite corroborates data from boreholes. Thickness of the Ignimbrite sheet may reach 280 m near Rotorua City. It is suggested that the Rotorua caldera boundary is not a single fault but a fault zone consisting of at least 4 faults. The displacement on any one fault is no greater than 30 m. The near surface cold-warm thermal boundary, at the northern boundary of the Whakarewarewa thermal area, is also shown in the seismic section.

  10. Structure and Tectonics of the Cheb Basin (NW-Bohemia) from a shallow reflection seismic survey

    NASA Astrophysics Data System (ADS)

    Halpaap, Felix; Paschke, Marco; Bleibinhaus, Florian

    2015-04-01

    In the seismically active region of Northwest Bohemia, we imaged structural characteristics of the Cenozoic Cheb Basin with a shallow 3.5 km reflection seismic survey to find proof of faulting along the Počatky-Plesná shear zone (PPZ). Previously, the shear zone's existence has been inferred from earthquakes that occur in swarms and concentrate in the focal zone of Nový Kostel, below the Cheb Basin, along a plane striking at 170°. The difference in strike between the planar focal zone and the 145° oriented, crustal-scale eastern border fault of the Cheb Basin, which forms the northern termination of the geomorphologically dominant Mariánské Lazně fault, was interpreted to hint to the existence of a second major crustal fault zone. With additional interpretations of river drainage patterns, a distinct 25 m terrain escarpment and the distribution of Quaternary sediments around the Plesná river, the surface outcrop of the PPZ was thought to be found. A P-velocity model which we obtained from tomographic inversion of the first arrivals revealed an uppermost layer of very slow seismic velocities (about 1 km/s) that varies strongly in thickness. We interpret this layer as unconsolidated Quaternary sediments, which impacted the quality of our recorded shot gathers negatively with increasing thickness of the layer. The result of our standard reflection seismic processing, challenged by strong ground roll, is an image of the eastern Cheb Basin's layers and several tectonic features along a cross-strike profile with varying resolution. Our seismic image shows undisturbed younger sediments of the upper neogene Vildštejn and Cypris Formation, overlying the early miocene Main Coal Seam Formation and a structured basement. The imaged maximum basin depth of 300 m and unconformities below and above the Vildštejn Formation correspond well with litostratigraphic borehole data and previous sedimentological and tectonic models. We observe reverse faults in the lower

  11. Seismicity surveys with ocean bottom seismographs off Western Canada

    SciTech Connect

    Hyndman, R.D.; Rogers, G.C.

    1981-05-10

    Three arrays of ocean bottom seismographs have been deployed to study the seismicity at the northern end of the Juan de Fuca ridge system off western Canada. Nearly 100 events were located with estimated accuracies generally better than +- 10 km, all lying on or near the en echelon ridge-transform fault plate boundaries as defined in this area by the magnetic anomalies, the seafloor morphology and by other geophysical data. The depths of 12 events were determined to lie between 2 and 6 km below the top of the crust. The seismograms exhibit clear P and S wave arrivals along with phases that involve P to S and sometimes S to P conversion probably at the base of the sediments beneath the instruments. The event magnitudes have been estimated from signal duration using four calibration events that were well recorded by a land station. The magnitude estimates permit the determination of rough magnitude-frequency of occurrence relations over the magnitude range of 1 to 3 that are in surprisingly good agreement with the recurrence relations for the area at larger magnitudes from 75 years of land station data. The mean P wave velocity in the uppermost mantle from the earthquake data recorded by the sea floor arrays is 7.6 km s/sup -1/ and the mean V/sub p//V/sub s/ ratio is 1.71 or a Poisson's ratio of 0.24.

  12. Rapid geo-acoustic characterization from a seismic survey

    NASA Astrophysics Data System (ADS)

    Heaney, Kevin D.; Sternlicht, Daniel; Teranishi, Arthur; Castille, Brett; Hamilton, Michael

    2002-05-01

    A recent transmission loss experiment was conducted in Long Beach Harbor for the THUMS Long Beach Company. The objective of the experiment was to measure the range at which the received level was 160 dB for compliance with Marine Mammal regulations. This short experiment provided the opportunity to test the rapid geo-acoustic characterization (RGC) algorithm and perform real-time geo-acoustic inversions from a seismic source. The airgun source transmitted pulses every 20 s corresponding to every 45 m. The water depth was 10-15 m and the water was assumed to be iso-velocity. The data quality was excellent, providing clear striation patterns in the broadband frequency display. The RGC algorithm matches the observed time-spread, striation slope, and TL slope to precomputed values using a normal mode algorithm and parametric geo-acoustic profiles based on Hamilton and Bachman's model. Precomputation of the acoustic observables, combined with real-time signal processing permits real time geo-acoustic characterization.

  13. 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.

  14. Combined microbial, seismic surveys predict oil and gas occurrences in Bolivia

    SciTech Connect

    Lopez, J.P. ); Hitzman, D.; Tucker, J. )

    1994-10-24

    Microbial and geophysical surveys in the jungles of Bolivia's extensive Sub-Andean region have combined for three successful predictions of deep oil and gas reserves in as many tries. Hydrocarbon microseepage measured by microbial soil samples predicted the Carrasco, Katari, and Surubi structures of Bolivia's Chapare region in 1991--92, detecting traps with reserves at depths exceeding 4,500 m. Approximately 800 km of seismic lines covering 3,500 sq km was completed by Yacimientos Petroliferos Fiscales Bolivianos (YPFB) for evaluation of the YPFB reserve block. For 1 month each year at the end of the field season, seismic lines were quickly traversed by several microbial sampling teams. Using hand augers or shovels, the teams collected more than 3,200 samples approximately 20 cm (8 in.) deep at intervals of 250 m next to staked seismic locations. Microbial results were directly compared with seismic profiles for identification and ranking of traps and structures. The paper discusses the survey predictions and the microbial approach.

  15. Downhole seismic logging for high-resolution reflection surveying in unconsolidated overburden

    SciTech Connect

    Hunter, J.A.; Pullan, S.E.; Burns, R.A.; Good, R.L.; Harris, J.B.; Pugin, A.; Skvortsov, A.; Goriainov, N.N.

    1998-07-01

    Downhole seismic velocity logging techniques have been developed and applied in support of high-resolution reflection seismic surveys. Data obtained from downhole seismic logging can provide accurate velocity-depth functions and directly correlate seismic reflections to depth. The methodologies described in this paper are designed for slimhole applications in plastic-cased boreholes (minimum ID of 50 mm) and with source and detector arrays that yield similar frequency ranges and vertical depth resolutions as the surface reflection surveys. Compressional- (P-) wave logging uses a multichannel hydrophone array with 0.5-m detector spacings in a fluid-filled borehole and a high-frequency, in-hole shotgun source at the surface. Overlapping array positions downhole results in redundant first-arrival data which can be processed to provide accurate interval velocities. The data also can be displayed as a record suite, showing reflections and directly correlating reflection events with depths. Example applications include identification of gas zones, lithological boundaries within unconsolidated sediments, and the overburden-bedrock interface. Shear- (S-) wave logging uses a slimhole, well-locked, three-component (3-C) geophone pod and a horizontally polarized, hammer-and-loaded-plate source at ground surface. In unconsolidated sediments, shear-wave velocity contrasts can be associated with changes in material density or dynamic shear modulus, which in turn can be related to consolidation. Example applications include identification of a lithological boundary for earthquake hazard applications and mapping massive ice within permafrost materials.

  16. Pen Branch fault program: Consolidated report on the seismic reflection surveys and the shallow drilling

    SciTech Connect

    Stieve, A.L.; Stephenson, D.E.; Aadland, R.K.

    1991-03-23

    The Pen Branch fault was identified in the subsurface at the Savannah River Site (SRS) in 1989 based upon interpretation of earlier seismic reflection surveys and other geologic investigations (Seismorgraph Services Incorp., 1973; Chapman and DiStefano, 1989; Snipes, Fallaw and Price, 1989). A program was initiated at that time to determine the capability of the fault to release seismic energy (Price and others, 1989) as defined in the Nuclear Regulatory Commission regulatory guidelines, 10 CFR 100 Appendix A. This report presents the results of the Pen Branch fault investigation based on data acquired from seismic reflection surveys and shallow drilling across the fault completed at this time. The Earth Science Advisory Committee (ESAC) has reviewed the results of these investigations and unanimously agrees with the conclusion of Westinghouse Savannah River Company (WSRC) that the Pen Branch fault is a non-capable fault. ESAC is a committee of 12 earth science professionals from academia and industry with the charter of providing outside peer review of SRS geotechnical, seismic, and ground water modeling programs.

  17. 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

  18. Earthquake emergency plans and seismic criteria for their activation

    NASA Astrophysics Data System (ADS)

    Roca, A.; Gasulla, N.; Susagna, T.; Goula, X.; Romeu, N.

    2003-04-01

    The organization of human and material resources to face up to an earthquake crisis is established through emergency plans at different scales (national, regional and local). National plans often establish the criteria for preparing regional and local plans mainly based on intensity of ground shaking. However, in order to decide which counties or municipalities need to prepare a specific emergency plan, vulnerability and risk should be assessed and damage scenarios generated. The emergency plans include various levels of intervention depending of the severity of the event in order to bring out the adequate amount of resources, and can be activated by early warnings based on rapid detection provided by seismic networks. These activation levels should be defined taking into account not only the ground shaking but also many other factors related to the physical, human and societal vulnerability. An approach developed for the area of Catalonia, NE Spain, in which earthquake risk and damage scenarios were estimated and activation levels were defined in function of the focal parameters of the seismic event and the population distribution is presented. An automatic system for implementing these concepts linked to the existing real time VSAT based seismic network of Catalonia is under development.

  19. Structure of the San Andreas fault zone at SAFOD from a seismic refraction survey

    USGS Publications Warehouse

    Hole, J.A.; Ryberg, T.; Fuis, G.S.; Bleibinhaus, F.; Sharma, A.K.

    2006-01-01

    Refraction traveltimes from a 46-km long seismic survey across the San Andreas Fault were inverted to obtain two-dimensional velocity structure of the upper crust near the SAFOD drilling project. The model contains strong vertical and lateral velocity variations from <2 km/s to ???6 km/s. The Salinian terrane west of the San Andreas Fault has much higher velocity than the Franciscan terrane east of the fault. Salinian basement deepens from 0.8 km subsurface at SAFOD to ???2.5 km subsurface 20 km to the southwest. A strong reflection and subtle velocity contrast suggest a steeply dipping fault separating the Franciscan terrane from the Great Valley Sequence. A low-velocity wedge of Cenozoic sedimentary rocks lies immediately southwest of the San Andreas Fault. This body is bounded by a steep fault just northeast of SAFOD and approaches the depth of the shallowest earthquakes. Multiple active and inactive fault strands complicate structure near SAFOD. Copyright 2006 by the American Geophysical Union.

  20. 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

  1. Crustal structure of the western Yamato Basin, Japan Sea, revealed from seismic survey

    NASA Astrophysics Data System (ADS)

    No, T.; Sato, T.; Kodaira, S.; Miura, S.; Ishiyama, T.; Sato, H.

    2015-12-01

    The Yamato Basin is the second largest basin of the Japan Sea. This basin is important to clarify its formation process. Some studies of crustal structure had been carried out in the Yamato Basin (e.g. Ludwig et al., 1975; Katao, 1988; Hirata et al., 1989; Sato et al., 2006). However, the relationship between formation process and crustal structure is not very clear, because the amount of seismic exploration data is very limited. In addition, since there is ODP Leg 127 site 797 (Tamaki et al., 1990) directly beneath our seismic survey line, we contributed to the study on the formation of the Yamato Basin by examining the relation between the ODP results and our results. During July-August 2014, we conducted a multi-channel seismic (MCS) survey and ocean bottom seismometer (OBS) survey to study the crustal structure of the western Yamato Basin. We present an outline of the data acquisition and results of the data processing and preliminary interpretations from this study. As a result of our study, the crust, which is about 12 km thick, is thicker than standard oceanic crust (e.g., Spudich and Orcutt, 1980; White et al., 1992) revealed from P-wave velocity structure by OBS survey. A clear reflector estimated to be the Moho can be identified by MCS profiles. The characteristics of the sedimentary layer are common within the survey area. For example, a strong coherent reflector that is estimated to be an opal-A/opal-CT BSR (bottom simulating reflector) (Kuramoto et al., 1992) was confirmed in the sediment of all survey lines. On the other hand, a coherent reflector in the crust was confirmed in some lines. It is identified as this reflector corresponding with the deformation structure in the sediment and basement.

  2. 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

  3. Near-surface seismic surveys at Rifle, Colorado for shallow groundwater contamination risk assessment

    NASA Astrophysics Data System (ADS)

    Chen, J.; Zelt, C. A.; Levander, A.

    2013-12-01

    In August 2012, we carried out a series of seismic surveys at a site located approximately 0.3 mile east of the city of Rifle in Garfield County, Colorado. The ground water beneath this site was contaminated by former vanadium and uranium ore-processing operations from 1924 through 1958. The site is on an alluvial terrace created by a flood-plain meander of the Colorado River. On the south side, the terrace is bounded by a steep descending slope to the Colorado River; on the other sides, it is bounded by ascending slopes of the more resistant sedimentary rocks of the Wasatch Formation. Although remedial actions have been taken to remove the contaminated surface materials, there are still potential risks from residual materials and redistribution of the contaminated water harming human health. This seismic project, funded by The U.S. Department of Energy, was designed to provide hydrogeologic information through sub-surface velocity model building and imaging of the water aquifer. A 3D compressional wave seismic survey covers an area that is 96 m in the N-S direction by 60 m in the E-W direction. An orthogonal, symmetric receiver and source template was used with 24 receiver lines, 96 channels per receiver line, and 2.5 m between lines. The inline shot and receiver spacing is 2 m and 1 m, respectively. The source was an accelerated weight drop striking a metal plate. The source has a dominant frequency at ~60 Hz, and is down by 20 db at 20 Hz and 150 Hz, providing data suitable for seismic tomography and seismic migration methods. Besides this 3D survey, three other seismic experiments were performed: (1) a 2D multi-component source and receiver survey, (2) a 3D surface wave experiment using 4.5 Hz geophones, and (3) an ambient noise experiment using 4.5 Hz geophones to record passing vehicles and trains. Preliminary results of the data analysis will be presented.

  4. 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.

  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. 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.

  7. An updated active structure database of Taiwan for seismic hazard assessments

    NASA Astrophysics Data System (ADS)

    Shyu, J. B. H.; Chuang, Y. R.; Chen, Y. L.; Lee, Y.; Cheng, T. C. T.

    2014-12-01

    In order to build a complete seismogenic source model to assess future seismic hazards in Taiwan, we have constructed an updated active structure database for the island. We reviewed existing active structure databases, and obtained new information for structures that have not been thoroughly analyzed before. For example, the Central Geological Survey of Taiwan has published a comprehensive database of active faults in Taiwan, including all of the historically ruptured faults. Many other active structures, such as blind faults or folds that can be identified from geomorphic or structural analysis, have also been mapped and reported in several previous investigations. We have combined information from these existing databases to build an updated and digitized three-dimensional active structure map for Taiwan. Furthermore, for detailed information of individual structure such as long-term slip rates and potential recurrence intervals, we have collected the data from existing publications, as well as calculated from results of our own field surveys and investigations. We hope this updated database would become a significant constraint for the calculations of seismic hazard assessments in Taiwan, and would provide important information for engineers and hazard mitigation agencies.

  8. Toward long-term all-sky time domain surveys-SINDICS: a prospective concept for a Seismic INDICes Survey of half a million red giants

    NASA Astrophysics Data System (ADS)

    Michel, Eric; Haywood, Misha; Mosser, Benoit; García, Rafael A.; Babusiaux, Carine; Ballot, Jérôme; Samadi, Reza; Katz, David; Belkacem, Kevin; Bernardi, Pernelle; Buey, Tristan

    2015-09-01

    CoRoT and Kepler have brought a new and deep experience in long-term photometric surveys and how to use them. This is true for exoplanets characterizing, stellar seismology and beyond for studying several other phenomena, like granulation or activity. Based on this experience, it has been possible to propose new generation projects, like TESS and PLATO, with more specific scientific objectives and more ambitious observational programs in terms of sky coverage and/or duration of the observations. In this context and as a prospective exercise, we explore here the possibility to set up an all-sky survey optimized for seismic indices measurement, providing masses, radii and evolution stages for half a million solar-type pulsators (subgiants and red giants), in our galactic neighborhood and allowing unprecedented stellar population studies.

  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. Vertical Cable Seismic (VCS) Survey for SMS exploration in Izena Cauldron, Okinawa-Trough

    NASA Astrophysics Data System (ADS)

    Asakawa, Eiichi; Murakami, Fumitoshi; Tsukahara, Hitoshi; Mizohata, Shigeharu; Tara, Kenji

    2015-04-01

    In 2014, the Japanese government started the Cross-ministerial Strategic Innovation Promotion Program (SIP), which includes 'New-generation Offshore Exploration Techniques' as an area of interest. We proposed the Vertical Cable Seismic (VCS) survey technique for this program, especially for the exploration of Seafloor Massive Sulfides (SMS). VCS is a reflection seismic method that uses hydrophone arrays vertically moored from the seafloor to record acoustic waves generated by various acoustic sources. This method is useful to delineate detailed structures in a spatially-limited area below the seabed in the deep sea where conventional surface seismic is not effective. We have been developing an autonomous VCS system with the financial support of the Japanese government since 2009. We have carried out several VCS surveys and completed our VCS system. Izena Cauldron, Okinawa Trough is one of the most promising SMS areas around Japan. There are two high potential areas, the north and south mound. We carried out the first VCS survey around the north mound in 2011 and the second survey around the south mound in 2013 respectively. The first VCS survey in Izena Cauldron was carried out using a GI gun in September, 2011, with the objective of surveying the large-scale and deeper structure of the hydrothermal system. The water depth was 1,500-1,600m. Four VCS systems were deployed. The shooting lines covered an area of 9 km x 9 km with a shooting interval of about 25m and line spacing of 200m to 400m. In the second survey, we used a high-voltage sparker. The objective is to explore very shallow parts to delineate very thin SMS deposits. The survey area was about 4 km x 4km with a 12.5 m shooting interval and 100m to 200m line spacing. Three VCS systems were deployed in this survey. The result of the first GI gun VCS survey was a 3D PSDM volume of the subsurface structure. It extends 2,000m horizontally and down to 1,500m in depth. Further, by re-processing the data with a

  11. Application of uphole data from petroleum seismic surveys to groundwater investigations, Abu Dhabi (United Arab Emirates)

    USGS Publications Warehouse

    Woodward, D.; Menges, C.M.

    1991-01-01

    Velocity data from uphole surveys were used to map the water table and the contact at the base dune sand/top alluvium as part of a joint National Drilling Company-United States Geological Survey Ground Water Research Project in the Emirate of Abu Dhabi. During 1981-1983, a reconnaissance seismic survey was conducted for petroleum exploration in the eastern region of Abu Dhabi. Approximately 2800 kilometers of seismic data, consisting of 92 lines, were acquired in the 2500 km2 concession area near Al Ain. Uphole surveys were conducted about 2 km apart along each seismic line, and were used to calculate weathering corrections required to further process in the seismic data. Approximately 1300 uphole surveys were completed in the concession area between March 1981 and June 1983. Reinterpretation of the velocity profiles derived from the uphole surveys provided data for determining the following subsurface layers, listed in descending order: (1) a surficial, unconsolidated weathering layer with a velocity from 300 to 450 m/s; (2) surficial dune sand, from 750 to 900 m/s; (3) unsaturated, unconsolidated alluvium, from 1000 to 1300 m/s; and (4) saturated, unconsolidated alluvium, from 1900 to 2200 m/s. Two interfaces-the water table and the base dune sand/top alluvium - were identified and mapped from boundaries between these velocity layers. Although the regional water table can fluctuate naturally as much as 3 m per year in this area and the water-table determinations from the uphole data span a 27-month period, an extremely consistent and interpretable water-table map was derived from the uphole data throughout the entire concession area. In the northern part of the area, unconfined groundwater moves northward and northwestward toward the Arabian Gulf; and in the central and southern parts of the area, groundwater moves westward away from the Oman Mountains. In the extreme southern area east of Jabal Hafit, groundwater moves southward into Oman. The map of the base

  12. Global thunderstorm activity research survey

    NASA Technical Reports Server (NTRS)

    Coroniti, S. C.

    1982-01-01

    The published literature on the subject of the monitoring of global thunderstorm activity by instrumented satellites was reviewed. A survey of the properties of selected physical parameters of the thunderstorm is presented. The concepts used by satellites to identify and to measure terrestrial lightning pulses are described. The experimental data acquired by satellites are discussed. The scientific achievements of the satellites are evaluated against the needs of scientists and the potential requirements of user agencies. The performances of the satellites are rated according to their scientific and operational achievements.

  13. 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 measurements (Horizontal-to-Vertical Spectral Ratios - HVSR) to characterize strong-motion sites in Washington and Oregon. The MASW analysis was used to better constrain the shallowest part of the Vs profile, while effective dispersion curve provided by ESAC and HVSR data allow us to extend the survey downwards (up to hundred meters of depth). The combined use of these data in the frame of global-search inversion algorithms (Genetic Algorithms) allows us to manage the extreme non-linearity of the inverse problem and mitigate problems associated with the non-uniqueness of the solution. A strict synergy between geologic surveys, boreholes (when the latter was available) and seismic surveys allows a further reduction of relevant uncertainties. Preliminary results show that; i) this combined methodology is a practical, inexpensive, and fast way to characterize multiple strong motion sites; ii) local geology and/or borehole information was combined to better constrain the inversion and to reduce the uncertainty in velocity profiles; and, iii) this combined methodology gives additional information of shear-wave velocities at greater depths.

  14. Modeling acoustic wave propagation in the Southern Ocean to estimate the acoustic impact of seismic surveys on marine mammals

    NASA Astrophysics Data System (ADS)

    Breitzke, M.; Bohlen, T.

    2007-12-01

    According to the Protocol on Environmental Protection to the Antarctic Treaty, adopted 1991, seismic surveys in the Southern Ocean south of 60°S are exclusively dedicated to academic research. The seismic surveys conducted by the Alfred-Wegener-Institute for Polar and Marine Research, Bremerhaven, Germany during the last 20 years focussed on two areas: The Wedell Sea (60°W - 0°W) and the Amundsen/Bellinghausen Sea (120°W - 60°W). Histograms of the Julian days and water depths covered by these surveys indicate that maximum activities occurred in January and February, and most lines were collected either in shallow waters of 400 - 500 m depth or in deep waters of 2500 - 4500 m depth. To assess the potential risk of future seismic research on marine mammal populations an acoustic wave propagation modeling study is conducted for the Wedell and the Amundsen/ Bellinghausen Sea. A 2.5D finite-difference code is used. It allows to simulate the spherical amplitude decay of point sources correctly, considers P- and S-wave velocities at the sea floor and provides snapshots of the wavefield at any spatial and temporal resolution. As source signals notional signatures of GI-, G- and Bolt guns, computed by the NUCLEUS software (PGS) are used. Based on CTD measurements, sediment core samplings and sediment echosounder recordings two horizontally-layered, range-independent generic models are established for the Wedell and the Amundsen/Bellinghausen Sea, one for shallow (500 m) and one for deep water (3000 m). They indicate that the vertical structure of the water masses is characterized by a 100 m thick, cold, low sound velocity layer (~1440 - 1450 m/s), centered in 100 m depth. In the austral summer it is overlain by a warmer, 50 m thick surface layer with slightly higher sound velocities (~1447 - 1453 m/s). Beneath the low-velocity layer sound velocities increase rapidly to ~1450 - 1460 m/s in 200 m depth, and smoothly to ~1530 m/s in 4700 m depth. The sea floor is mainly

  15. Approaching a more Complete Picture of Rockfall Activity: Seismic and LiDAR Detection, Loaction and Volume Estimates

    NASA Astrophysics Data System (ADS)

    Dietze, Michael; Mohadjer, Solmaz; Turowski, Jens; Ehlers, Todd; Hovius, Niels

    2016-04-01

    Rockfall activity in steep alpine landscapes is often difficult to survey due to its infrequent nature. Classic approaches are limited by temporal and spatial resolution. In contrast, seismic monitoring provides access to catchment-wide analysis of activity patterns in rockfall-dominated environments. The deglaciated U-shaped Lauterbrunnen Valley in the Bernese Oberland, Switzerland, is a perfect example of such landscapes. It was instrumented with up to six broadband seismometers and repeatedly surveyed by terrestrial LiDAR to provide independent validation data. During August-October 2014 and April-June 2015 more than 23 (LiDAR) to hundred (seismic) events were detected. Their volumes range from < 0.01 to 5.80 cubic metres as detected by LiDAR. The evolution of individual events (i.e., precursor activity, detachment, falling phase, impact, talus cone activity) can be quantified in terms of location and duration. For events that consist of single detachments rather than a series of releases, volume scaling relationships are possible. Seismic monitoring approaches are well-suited for studying not only the rockfall process but also for understanding the geomorphic framework and boundary conditions that control such processes in a comprehensive way. Taken together, the combined LiDAR and seismic monitoring approach provides high fidelity spatial and temporal resolution of individual events.

  16. 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.

  17. Seismic activity offshore Martinique and Dominica islands (Central Lesser Antilles subduction zone) from temporary onshore and offshore seismic networks

    NASA Astrophysics Data System (ADS)

    Ruiz, M.; Galve, A.; Monfret, T.; Sapin, M.; Charvis, P.; Laigle, M.; Evain, M.; Hirn, A.; Flueh, E.; Gallart, J.; Diaz, J.; Lebrun, J. F.

    2013-09-01

    This work focuses on the analysis of a unique set of seismological data recorded by two temporary networks of seismometers deployed onshore and offshore in the Central Lesser Antilles Island Arc from Martinique to Guadeloupe islands. During the whole recording period, extending from January to the end of August 2007, more than 1300 local seismic events were detected in this area. A subset of 769 earthquakes was located precisely by using HypoEllipse. We also computed focal mechanisms using P-wave polarities of the best azimuthally constrained earthquakes. We detected earthquakes beneath the Caribbean forearc and in the Atlantic oceanic plate as well. At depth seismicity delineates the Wadati-Benioff Zone down to 170 km depth. The main seismic activity is concentrated in the lower crust and in the mantle wedge, close to the island arc beneath an inner forearc domain in comparison to an outer forearc domain where little seismicity is observed. We propose that the difference of the seismicity beneath the inner and the outer forearc is related to a difference of crustal structure between the inner forearc interpreted as a dense, thick and rigid crustal block and the lighter and more flexible outer forearc. Seismicity is enhanced beneath the inner forearc because it likely increases the vertical stress applied to the subducting plate.

  18. 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.

  19. High resolution seismic survey, Pen Branch Fault, Savannah River Site, South Carolina

    SciTech Connect

    Berkman, E. )

    1991-04-01

    An investigation of the Pen Branch Fault at the Savannah River Site by a series of short, high resolution seismic reflection lines was conducted. The purpose was to acquire, process, and interpret 19.9 miles of data, optimized for the upper 300 ft of geologic strata, in sufficient density such that processing performed in the conventional stepwise approach, followed by detailed interpretation, would define small scale spatial variability and structural features in the vicinity of the fault leading to definition of the location of the fault, the shallowest extent of the fault, and the quantification of the sense and magnitude of motion. The depth of optimization for the last two lines was modified to the 300 ft of geologic strata immediately above basement. Three older seismic surveys, other geophysical data, and associated borehole and geologic data were reviewed. The equipment and the acquisition, processing, and interpretation procedures are discussed in the report. The report includes a detailed line by line description and discussion of the interpretation. Figures include reference maps, contour displays of the stacking and interval velocities, diagrammatic references sketches of the interpreted layering and sedimentary features, index sketches, and specific color prints made on the workstation during the course of the interpretation. A volume of manuals on seismic devices and related equipment is included.

  20. High resolution seismic survey, Pen Branch Fault, Savannah River Site, South Carolina. Final report

    SciTech Connect

    Berkman, E.

    1991-04-01

    An investigation of the Pen Branch Fault at the Savannah River Site by a series of short, high resolution seismic reflection lines was conducted. The purpose was to acquire, process, and interpret 19.9 miles of data, optimized for the upper 300 ft of geologic strata, in sufficient density such that processing performed in the conventional stepwise approach, followed by detailed interpretation, would define small scale spatial variability and structural features in the vicinity of the fault leading to definition of the location of the fault, the shallowest extent of the fault, and the quantification of the sense and magnitude of motion. The depth of optimization for the last two lines was modified to the 300 ft of geologic strata immediately above basement. Three older seismic surveys, other geophysical data, and associated borehole and geologic data were reviewed. The equipment and the acquisition, processing, and interpretation procedures are discussed in the report. The report includes a detailed line by line description and discussion of the interpretation. Figures include reference maps, contour displays of the stacking and interval velocities, diagrammatic references sketches of the interpreted layering and sedimentary features, index sketches, and specific color prints made on the workstation during the course of the interpretation. A volume of manuals on seismic devices and related equipment is included.

  1. Angola Seismicity MAP

    NASA Astrophysics Data System (ADS)

    Neto, F. A. P.; Franca, G.

    2014-12-01

    The purpose of this job was to study and document the Angola natural seismicity, establishment of the first database seismic data to facilitate consultation and search for information on seismic activity in the country. The study was conducted based on query reports produced by National Institute of Meteorology and Geophysics (INAMET) 1968 to 2014 with emphasis to the work presented by Moreira (1968), that defined six seismogenic zones from macro seismic data, with highlighting is Zone of Sá da Bandeira (Lubango)-Chibemba-Oncócua-Iona. This is the most important of Angola seismic zone, covering the epicentral Quihita and Iona regions, geologically characterized by transcontinental structure tectono-magmatic activation of the Mesozoic with the installation of a wide variety of intrusive rocks of ultrabasic-alkaline composition, basic and alkaline, kimberlites and carbonatites, strongly marked by intense tectonism, presenting with several faults and fractures (locally called corredor de Lucapa). The earthquake of May 9, 1948 reached intensity VI on the Mercalli-Sieberg scale (MCS) in the locality of Quihita, and seismic active of Iona January 15, 1964, the main shock hit the grade VI-VII. Although not having significant seismicity rate can not be neglected, the other five zone are: Cassongue-Ganda-Massano de Amorim; Lola-Quilengues-Caluquembe; Gago Coutinho-zone; Cuima-Cachingues-Cambândua; The Upper Zambezi zone. We also analyzed technical reports on the seismicity of the middle Kwanza produced by Hidroproekt (GAMEK) region as well as international seismic bulletins of the International Seismological Centre (ISC), United States Geological Survey (USGS), and these data served for instrumental location of the epicenters. All compiled information made possible the creation of the First datbase of seismic data for Angola, preparing the map of seismicity with the reconfirmation of the main seismic zones defined by Moreira (1968) and the identification of a new seismic

  2. Results from a new seismic survey around the JFAST drill site

    NASA Astrophysics Data System (ADS)

    Nakamura, Y.; Kodaira, S.; Yamamoto, Y.; Fujie, G.; Obana, K.; Miura, S.; Takahashi, N.; Cook, B.; Conin, M.; Chester, F. M.; Mori, J. J.; Eguchi, N.; Toczko, S.

    2013-12-01

    After the 2011 Tohoku earthquake, we have carried out several seismic surveys in the Japan Trench region. A high-resolution seismic survey collected in 2011 using a 1300-m-long streamer cable and a gun array with volume of 320 inch3 played an important role for choosing the site location and its results showed detailed structure in the Japan Trench axis area. Due to the short offset of the streamer cable, however, the seismic velocity could not be accurately determined.. Furthermore, the regional structural profiles were not obtained because of the small volume of the sounding source from the high resolution seismic survey. In January 2013, we conducted a seismic survey around the IODP Site C0019 drilled during the IODP Expedition 343 (JFAST) with air gun arrays with volume of 7800 inch3 by R/V Kairei. We used a 6000-m-long streamer cable and 4 OBSs as receivers. The shot interval was 50 m along the survey lines. The primary survey line JFD1 runs across the Japan Trench in WNW-ESE direction and the length of the line is ~ 100 km centered at the Site C0019. The data obtained by the streamer cable were processed through the Pre-stack time migration (PrSTM) technique. On the PrSTM section of the line JFD1, a relatively strong reflection is observed at ~ 1 s two-way travel time (TWT) below the seafloor in the landward part of the section through ~20 km landward from the trench axis, which corresponds to the 'Cretaceous unconformity'. Landward-dipping reflections observed 15-30 km landward of the trench axis could be a 'backstop interface'. Several landward dipping reflections are imaged within the frontal prism. In the vicinity of the trench axis, imbricated structure of incoming sediments is imaged on the PrSTM profile as previously observed on the high resolution profiles. A seaward dipping reflection, which was interpreted as a part of decollement at the landward part of the trench graben, is also observed in the PrSTM section. The top of the subducting oceanic

  3. Crustal nature and seismic structure of the geological provinces offshore the SW Iberia: Highlights of the NEAREST-SEIS wide-angle seismic survey

    NASA Astrophysics Data System (ADS)

    Martínez-Loriente, S.; Sallares, V.; Gailler, A.; Bartolome, R.; Gracia, E.; Gutscher, M.; Diaz, J.

    2011-12-01

    The SW Iberian margin hosts the present day NW-SE plate convergence between the European and African Plates at a rate of 4.5 mm/yr causing seismic activity of moderate magnitude. During fall 2008 and in the frame of the EU-funded NEAREST project, was carried out a wide-angle seismic survey (NEAREST-SEIS cruise) consisting in 2 profiles. The main objectives of the survey were to gather information about the geometry of the crust-mantle boundary, identify the nature of the different geological provinces, obtain the physical properties of the crust, and unveil the deep geometry of the interfaces between main faults. A total of 30 OBS were deployed along profile P1, which is 356 km long and trends NW-SE running from the Tagus Abyssal Plain (TAP), Gorringe Bank (GB), Horseshoe Abyssal Plain (HAP), Coral Patch Ridge (CPR), and finally reaching the thrust-and-fold belt of the Seine Abyssal Plain (SAP). The inverted model shows four well-differentiated domains in terms of seismic structure. In the TAP there is a 3-4 km-thick sediment layer with low velocity, lying above a basement showing a remarkably high velocity (< 7 km/s), similar to that of the basement outcropping in the GB. In the HAP the sedimentary cover is thicker, showing an uppermost unit with very low velocity corresponding to the Upper Miocene Horseshoe Gravitational Unit, on top of a higher velocity lower unit, which corresponds to the Mesozoic sedimentary sequence, with a total thickness of 5 km. The basement shows the same velocity distribution as in TAP and GB, suggesting a common nature and origin. According to its seismic structure, we interpret this basement as very serpentinized, exhumed upper mantle. In contrast, the CPR and SAP show evidence for the presence of a well-developed, 6-7 km-thick oceanic crust, underlying the 2-3 km thick Mesozoic and Neogene sedimentary sequence. Profile P2 is 256 km long and trends N-S, across the Iberian margin shelf, Portimao Bank, Gulf of Cadiz imbricated wedge and

  4. Simulation of complete seismic surveys for evaluation of experiment design and processing

    SciTech Connect

    Oezdenvar, T.; McMechan, G.A.; Chaney, P.

    1996-03-01

    Synthesis of complete seismic survey data sets allows analysis and optimization of all stages in an acquisition/processing sequence. The characteristics of available survey designs, parameter choices, and processing algorithms may be evaluated prior to field acquisition to produce a composite system in which all stages have compatible performance; this maximizes the cost effectiveness for a given level of accuracy, or for targets with specific characteristics. Data sets synthesized for three salt structures provide representative comparisons of time and depth migration, post-stack and prestack processing, and illustrate effects of varying recording aperture and shot spacing, iterative focusing analysis, and the interaction of migration algorithms with recording aperture. A final example demonstrates successful simulation of both 2-D acquisition and processing of a real data line over a salt pod in the Gulf of Mexico.

  5. 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

  6. Seismic activity of the East Sea, Korea offshore earthquake sequence

    NASA Astrophysics Data System (ADS)

    PARK, E.; Park, S.; Hahm, I.; Kim, Y.

    2013-12-01

    Seismicity in Korea is known to be relatively low compared to China and Japan. But it seems to be more active historically, according to historical documents on earthquake. The magnitudes of historical earthquakes were estimated to be about 4 - 6 by previous studies and there were several events with magnitude over 6. Instrumental earthquakes recorded in 1978 - 2012 seem to be smaller than historical earthquakes, according to the Korea Meteorological Administration (KMA) catalog. Their magnitudes are smaller than 4 in general. Although epicenters of instrumental earthquakes seem to be randomly distributed on the entire Korean Peninsula, some earthquakes occur intensively in several specific areas in the East Sea and the eastern region of Jeju Island. The areas having intensive seismic activity in the East Sea are offshore regions of Uljin (Region A), Yeongdeok (Region B), and Ulsan (Region C) from north to south. Eleven earthquakes of ML 2.0 - 3.2 occurred in Region A on April 2006. The epicenters were distributed within a radius of about 0.7 km. And the focal depths were in the range of 1.6 - 13.0 km (Kang and Shin, 2006). Kang and Shin (2006) propose that the sequence is closely related to the marginal geometry of the Ulleung Basin and the regional stress regime. Seven events with ML 2.1 - 3.0 occurred between September 12 and October 17 in 2007, and four events with ML 2.3 - 3.5 did between 07 December 2008 and 13 January 2009 in Region B. The relocations of eleven events greatly improved the epicenter locations that fall within an area with a radius of about 4 km. The relocated depths are in a range of 8 km to 14 km. According to Shin et al. (2012), the distribution of epicenters and fault plane solution of the largest earthquake in the sequences implied that the earthquake sequences are closely related to the Hupo fault at the eastern margin of Hupo basin. The sequences have been considered to have swarm seismicity pattern. In this study, we analyzed the

  7. 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

  8. 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.

  9. Abundance, behavior, and movement patterns of western gray whales in relation to a 3-D seismic survey, Northeast Sakhalin Island, Russia.

    PubMed

    Gailey, Glenn; Würsig, Bernd; McDonald, Trent L

    2007-11-01

    A geophysical seismic survey was conducted in the summer of 2001 off the northeastern coast of Sakhalin Island, Russia. The area of seismic exploration was immediately adjacent to the Piltun feeding grounds of the endangered western gray whale (Eschrichtius robustus). This study investigates relative abundance, behavior, and movement patterns of gray whales in relation to occurrence and proximity to the seismic survey by employing scan sampling, focal follow, and theodolite tracking methodologies. These data were analyzed in relation to temporal, environmental, and seismic related variables to evaluate potential disturbance reactions of gray whales to the seismic survey. The relative numbers of whales and pods recorded from five shore-based stations were not significantly different during periods when seismic surveys were occurring compared to periods when no seismic surveys were occurring and to the post-seismic period. Univariate analyses indicated no significant statistical correlation between seismic survey variables and any of the eleven movement and behavior variables. Multiple regression analyses indicated that, after accounting for temporal and environmental variables, 6 of 11 movement and behavior variables (linearity, acceleration, mean direction, blows per surfacing, and surface-dive blow rate) were not significantly associated with seismic survey variables, and 5 of 11 variables (leg speed, reorientation rate, distance-from-shore, blow interval, and dive time) were significantly associated with seismic survey variables. In summary, after accounting for environmental variables, no correlation was found between seismic survey variables and the linearity of whale movements, changes in whale swimming speed between theodolite fixes, mean direction of whale movement, mean number of whale exhalations per minute at the surface, mean time at the surface, and mean number of exhalations per minute during a whales surface-to-dive cycle. In contrast, at higher

  10. The mechanics of intermittent methane venting at South Hydrate Ridge inferred from 4D seismic surveying

    NASA Astrophysics Data System (ADS)

    Bangs, Nathan L. B.; Hornbach, Matthew J.; Berndt, Christian

    2011-10-01

    Sea floor methane vents and seeps direct methane generated by microbial and thermal decompositions of organic matter in sediment into the oceans and atmosphere. Methane vents contribute to ocean acidification, global warming, and providing a long-term (e.g. 500-4000 years; Powell et al., 1998) life-sustaining role for unique chemosynthetic biological communities. However, the role methane vents play in both climate change and chemosynthetic life remains controversial primarily because we do not understand long-term methane flux and the mechanisms that control it ( Milkov et al., 2004; Shakhova et al., 2010; Van Dover, 2000). Vents are inherently dynamic and flux varies greatly in magnitude and even flow direction over short time periods (hours-to-days), often tidally-driven ( Boles et al., 2001; Tryon et al., 1999). But, it remains unclear if flux changes at vents occur on the order of the life-cycle of various species within chemosynthetic communities (months, years, to decades Leifer et al., 2004; Torres et al., 2001) and thus impacts their sustainability. Here, using repeat high-resolution 3D seismic surveys acquired in 2000 and 2008, we demonstrate in 4D that Hydrate Ridge, a vent off the Oregon coast has undergone significant reduction of methane flow and complete interruption in just the past few years. In the subsurface, below a frozen methane hydrate layer, free gas appears to be migrating toward the vent, but currently there is accumulating gas that is unable to reach the seafloor through the gas hydrate layer. At the same time, abundant authigenic carbonates show that the system has been active for several thousands of years. Thus, it is likely that activity has been intermittent because gas hydrates clog the vertical flow pathways feeding the seafloor vent. Back pressure building in the subsurface will ultimately trigger hydrofracturing that will revive fluid-flow to the seafloor. The nature of this mechanism implies regular recurring flow interruptions

  11. Seismically active area monitoring by robust TIR satellite techniques: a sensitivity analysis on low magnitude earthquakes in Greece and Turkey

    NASA Astrophysics Data System (ADS)

    Corrado, R.; Caputo, R.; Filizzola, C.; Pergola, N.; Pietrapertosa, C.; Tramutoli, V.

    2005-01-01

    Space-time TIR anomalies, observed from months to weeks before earthquake occurrence, have been suggested by several authors as pre-seismic signals. Up to now, such a claimed connection of TIR emission with seismic activity has been considered with some caution by scientific community mainly for the insufficiency of the validation data-sets and the scarce importance attached by those authors to other causes (e.g. meteorological) that, rather than seismic activity, could be responsible for the observed TIR signal fluctuations. A robust satellite data analysis technique (RAT) has been recently proposed which, thanks to a well-founded definition of TIR anomaly, seems to be able to identify anomalous space-time TIR signal transients even in very variable observational (satellite view angle, land topography and coverage, etc.) and natural (e.g. meteorological) conditions. Its possible application to satellite TIR surveys in seismically active regions has been already tested in the case of several earthquakes (Irpinia: 23 November 1980, Athens: 7 September 1999, Izmit: 17 August 1999) of magnitude higher than 5.5 by using a validation/confutation approach, devoted to verify the presence/absence of anomalous space-time TIR transients in the presence/absence of seismic activity. In these cases, a magnitude threshold (generally M<5) was arbitrarily chosen in order to identify seismically unperturbed periods for confutation purposes. In this work, 9 medium-low magnitude (4

  12. 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

  13. Use of Preoperation Acoustic Modeling Combined with Real-Time Sound Level Monitoring to Mitigate Behavioral Effects of Seismic Surveys.

    PubMed

    Racca, Roberto; Austin, Melanie

    2016-01-01

    Underwater acoustic modeling is often used to estimate the injury radius around a seismic exploration source; only occasionally has it been applied to the mitigation of behavioral effects, where the safety boundary may extend to many kilometers. Such a mitigation strategy requires precise estimation of the sound field for many source locations and likely entails field validation over the course of the operation to ensure that mitigation regions are accurate. This article reviews the enactment of such an approach for a seismic survey off Sakhalin Island and examines how similar principles may be applied to other surveys under suitable conditions.

  14. 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.

  15. 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.

  16. The ancient harbour system of Terracina (Latium, Italy) obtained by gravity and seismic surveys.

    NASA Astrophysics Data System (ADS)

    di Nezza, Maria; di Filippo, Michele

    2010-05-01

    Historical research has shown that Terracina (Latina, Latium) played a fundamental role in the maritime and land traffic since before the foundation of the colony. The settlement was established where the organized system of maritime, land, coastal, and fluvial transport had the most ideal conditions to constitute an important commercial crossroads, apparently since the beginning of recorded history. In order to reconstruction the buried archaeological structures attributed to the ancient Roman port, traditionally attributed to Traiano, in the current area of the harbour of Terracina, it was carried out a gravity survey, more than 380 gravity stations. The gravity method enables to recognize the cavity and the structures of the buildings underground through the results of variations density in the subsoil. Seismic tomography treats the problem of identifying a buried structure as a wave propagation process by inverting the linearized wave equation to compute the spatial distribution of the slowness of the velocity. The purpose of our tomographic study is to further test the method and to guide archaeologists in their future excavations by locating and identifying buried structures. In the residual gravity anomaly map a series of positive anomalies are visible which confirm the round structures and the pier of the buried foundations of the Imperial harbour. Unfortunately, little remains of the functioning facilities of the harbour's activities. The modern construction of the harbour, in fact, has to be developed around the new inhabitable commercial area, know today as Terracina Bassa or Borgo alla Marina. It had to be developed with a modern infrastructure of a harbor area, as in the construction of the rooms for storage of goods, warehouses, as well as for the thermal baths, hotels and amphitheatre. Furthermore, there are always the positive anomalies that characterize the area to the north-east of "Montone" hill where archaeological remains are easily visible

  17. Crosswell acoustic surveying in gas sands: travel-time pattern recognition, seismic Q and channel waves

    SciTech Connect

    Albright, J.N.; Johnson, P.A.

    1985-01-01

    The application of crosswell acoustic measurements to gas sands research has been explored through surveys conducted in the Mesa Verde formation at the Department of Energy Multi-Well Experiment (MWX) site near Rifle, Colorado. The borehole tools used in the survey are similar in concept to those used in commercial service for sonic logging, but they are especially adapted for the stringent requirements of crosswell shooting in hot gas wells. Important information about the geologic structure between wells can be extracted from crosswell scans without resorting to elaborate processing. A useful representation is a display of the travel time of P-waves in terms of the cylindrical coordinates of the transmitter referenced to the receiver. This is known as a gamma-depth (..gamma..-Z) plot. Such a representation may yield distinctive patterns, which can be interpreted based on the successful replication of the pattern through computer simulations. The apparent seismic Q of P-waves transmitted through the sands at the MWX site is derived using two methods. The first applies to crosswell surveys in which signals can be acquired over a significant range of source-receiver distances. A Q of 15 between well pair MWX 1/2 is derived in this manner. The second method makes use of signals transmitted between wells in a three-well complex and provides an estimate of seismic Q for the rocks bounded by each well pair. Q estimates derived from this technique are 18, 30, and 28 for well bores MWX-1/2, MWX-2/3 and MWX-3/1, respectively. Channel waves propagate through the MWX coals. Evidence suggests that tube waves launched in the transmitter well give rise, under appropriate conditions, to channel waves, which in turn excite tube waves in nearby wells that penetrate the same channel. Although the sequence of conversions is weak, the resulting waveforms are coherent enough to resolve the channel waves through stacking. 8 refs., 10 figs.

  18. Incipient extension along the active convergent margin of Nubia in Sicily, Italy: Cefalù-Etna seismic zone

    NASA Astrophysics Data System (ADS)

    Billi, Andrea; Presti, Debora; Orecchio, Barbara; Faccenna, Claudio; Neri, Giancarlo

    2010-08-01

    Recent geodetic data are compatible with NNE-SSW tectonic extension at a rate of ˜5 mm/yr in Sicily, southern Italy, within a broader region of net active compression along the Nubian plate margin (northern Africa). The structures that accommodate such extensional regime and its cause are still unknown. From field structural surveys and seismological analyses, the geometry, kinematics, structural architecture, and seismic potential of an extensional seismic zone linking Cefalù and Mount Etna in central eastern Sicily are defined. The zone includes high-angle WNW striking normal and right-lateral strike-slip faults and subordinate north and NNE striking strike-slip faults either right or left lateral. The occurrence of small discontinuous faults and the absence of related depressions and sedimentary basins suggest that the extensional regime is still in an incipient stage. The ongoing seismic activity possibly reactivates preexisting faults. Instrumentally and historically recorded earthquakes are lower than about 6 in magnitude, and destructive events are historically unknown since at least 1300 A.D. This apparent upper bound of earthquake magnitudes is consistent with the maximum magnitude values estimated from the length of the longest mapped faults and sources of seismic swarms, which all together suggest a value between 6 and 6.5 as the maximum expected magnitude that can be proposed at the present stage of investigation for earthquakes in the study area. Lateral extension on preexisting faults and upwelling of melt mantle material beneath Mount Etna are considered viable processes to explain, at least in part, the active extensional tectonics along the Cefalù-Etna seismic zone. Strike-slip seismic faulting beneath Mount Etna may be part of a previously proposed diffuse transfer zone affecting northeastern Sicily and including the Tindari Fault.

  19. A High-resolution Seismic Reflection Survey at the Hanford Nuclear Site Using a Land Streamer

    NASA Astrophysics Data System (ADS)

    Hyde, E. R.; Speece, M. A.; Link, C. A.; Repasky, T.; Thompson, M.; Miller, S.; Cummins, G.

    2009-12-01

    From the 1940s through the mid 1990s, radioactively and chemically contaminated effluent waste was released into the ground at the Hanford Nuclear Site. Currently, Hanford is the site of a large-scale and ongoing environmental cleanup effort which includes the remediation of contaminated ground water. Identifying preferential pathways of groundwater contaminant flow is critical for the groundwater cleanup effort. During the summer of 2009, Montana Tech, in collaboration with the Confederated Tribes of the Umatilla Indian Reservation, collected a high resolution shallow seismic survey on the Hanford Central Plateau near the Gable Gap area of the Hanford Nuclear site. The goal of the survey was to demonstrate the feasibility of using a land streamer/gimbaled geophone acquisition approach to image the basalt bedrock topography. The survey objective is to improve the understanding of the subsurface water flow by identifying the topography of the basement basalt and possible erosional channels created during the Missoula flood events. Data was collected for a total of eight 2D lines with a combined length of about 11 km with a coverage area of approximately 6 sq.km. The profiles were aligned in north-south and east-west intersecting lines with a total of 5 profile intersections. The survey used a 227 kg accelerated weight drop and a 96-channel land streamer. The land streamer used gimbaled geophones with 2 m spacing. Source spacing was also 2 m for a nominal fold of 48. The rapid deployment land streamer, compared to conventional spiked geophones, significantly increased production in this off-road application. Typically, between 45 and 55 stations could be shot per hour in a pull and shoot approach. Deployment of the land streamer required about 45 minutes and about 30 minutes was required to shut down the survey. The survey successfully imaged the top of the basalt and demonstrated that a land streamer can produce quality seismic data in this area. The basalt bedrock

  20. Electrical Resistivity and Seismic Surveys at the Nevada Test Site, Nevada, April 2007

    USGS Publications Warehouse

    Haines, Seth S.; Burton, Bethany L.; Sweetkind, Donald S.; Asch, Theodore H.

    2008-01-01

    In April 2007, the USGS collected direct-current (DC) electrical resistivity data and shear- (S) and compressional- (P) wave seismic data to provide new detail of previously mapped, overlapping fault splays at two administrative areas in the Nevada Test Site (NTS). In NTS Area 7, we collected two-dimensional DC resistivity data along a transect crossing the Yucca Fault parallel to, and between, two transects along which resistivity data were collected in a previous study in 2006. In addition, we collected three-dimensional DC resistivity data in a grid that overlies part of the 2007 transect. The DC resistivity data show that the fault has a footwall that is more conductive than the hanging wall and an along-strike progression of the fault in a location where overlapping splays are present. Co-located with the northernmost of the two 2006 DC resistivity transects, we acquired S- and P-wave seismic data for both reflection and refraction processing. The S-wave data are corrupted by large amounts of converted (P-wave) energy likely due to the abundance of fractured caliche in the shallow subsurface. The P-wave data show minimal reflected energy, but they show clear refracted first arrivals. We have inverted these first arrival times to determine P-wave seismic velocity models. The seismic model for the transect in Area 7 shows low velocities extending to the base of the model at the location of the Yucca Fault, as well as low velocities at the eastern end of the transect, in the vicinity of the adjacent crater. These new surveys provide further detail about the geometry of the Yucca Fault in this location where it shows two overlapping splays. We collected P- and S-wave seismic data along a transect in the southern part of NTS Area 2, corresponding with the location of a 2006 DC resistivity transect that targeted a set of small faults identified with field mapping. Again, the S-wave data are difficult to interpret. The P-wave data show clear first arrivals that we

  1. Electrical Resistivity and Seismic Surveys at the Nevada Test Site, Nevada, April 2007

    SciTech Connect

    Seth S. Haines; Bethany L. Burton; Donald S. Sweetkind; Theodore H. Asch

    2009-03-30

    In April 2007, the USGS collected direct-current (DC) electrical resistivity data and shear- (S) and compressional- (P) wave seismic data to provide new detail of previously mapped, overlapping fault splays at two administrative areas in the Nevada Test Site (NTS). In NTS Area 7, we collected two-dimensional DC resistivity data along a transect crossing the Yucca Fault parallel to, and between, two transects along which resistivity data were collected in a previous study in 2006. In addition, we collected three-dimensional DC resistivity data in a grid that overlies part of the 2007 transect. The DC resistivity data show that the fault has a footwall that is more conductive than the hanging wall and an along-strike progression of the fault in a location where overlapping splays are present. Co-located with the northernmost of the two 2006 DC resistivity transects, we acquired S- and P-wave seismic data for both reflection and refraction processing. The S-wave data are corrupted by large amounts of converted (P-wave) energy likely due to the abundance of fractured caliche in the shallow subsurface. The P-wave data show minimal reflected energy, but they show clear refracted first arrivals. We have inverted these first arrival times to determine P-wave seismic velocity models. The seismic model for the transect in Area 7 shows low velocities extending to the base of the model at the location of the Yucca Fault, as well as low velocities at the eastern end of the transect, in the vicinity of the adjacent crater. These new surveys provide further detail about the geometry of the Yucca Fault in this location where it shows two overlapping splays. We collected P- and S-wave seismic data along a transect in the southern part of NTS Area 2, corresponding with the location of a 2006 DC resistivity transect that targeted a set of small faults identified with field mapping. Again, the S-wave data are difficult to interpret. The P-wave data show clear first arrivals that we

  2. Wide-angle seismic survey in the trench-outer rise region of the central Japan Trench

    NASA Astrophysics Data System (ADS)

    Fujie, G.; Kodaira, S.; Iwamaru, H.; Shirai, T.; Dannowski, A.; Thorwart, M.; Grevemeyer, I.; Morgan, J. P.

    2015-12-01

    Dehydration process within the subducting oceanic plate and expelled water from there affect various subduction-zone processes, including arc volcanism and generation of earthquakes. This implies that the degree of hydration within the incoming oceanic plate just prior to subduction might be a key control factor on the regional variations in subduction zone processes like interplate earthquakes and arc volcanism. Recent advances in seismic structure studies in the trench-outer rise region of the Japan Trench have revealed that seismic velocities within the incoming oceanic plate become lower owing to the plate bending-related faulting, suggesting the hydration of the oceanic plate. If the degree of the oceanic plate hydration is one of key factors controlling the regional variations of the interplate earthquakes, the degree of the oceanic plate hydration just prior to subduction is expected to show the along-trench variation because the interplate seismicity in the forearc region of the Japan Trench show along-trench variations. However, we cannot discuss the along-trench variation of the incoming plate structure because seismic structure studies have been confined only to the northern Japan Trench so far.In 2014 and 2015, JAMSTEC and GEOMAR conducted wide-angle seismic surveys in the trench-outer rise region of the central Japan Trench to reveal the detailed seismic structure of the incoming oceanic plate. The western extension of our survey line corresponds to the epicenter of the 2011 M9 Tohoku earthquakes. We deployed 88 Ocean Bottom Seismometers (OBSs) at intervals of 6 km and shot a tuned air-gun array of R/V Kairei at 200 m spacing. In this presentation, we will show the overview of our seismic survey and present seismic structure models obtained by the data of mainly 2014 seismic survey together with the several OBS data from 2015 survey. The preliminary results show P-wave velocity (Vp) within the oceanic crust and mantle decreases toward the trench axis

  3. 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.

  4. Annual Hanford seismic report -- fiscal year 1996

    SciTech Connect

    Hartshorn, D.C.; Reidel, S.P.

    1996-12-01

    Seismic monitoring (SM) at the Hanford Site was established in 1969 by the US Geological Survey (USGS) under a contract with the US Atomic Energy Commission. Since 1980, the program has been managed by several contractors under the US Department of Energy (USDOE). Effective October 1, 1996, the Seismic Monitoring workscope, personnel, and associated contracts were transferred to the USDOE Pacific Northwest National Laboratory (PNNL). SM is tasked to provide an uninterrupted collection and archives of high-quality raw and processed seismic data from the Hanford Seismic Network (HSN) located on and encircling the Hanford Site. SM is also tasked to locate and identify sources of seismic activity and monitor changes in the historical pattern of seismic activity at the Hanford Site. The data compiled are used by SM, Waste Management, and engineering activities at the Hanford Site to evaluate seismic hazards and seismic design for the Site.

  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. Neotectonic and seismotectonic investigation of seismically active regions in Tunisia: a multidisciplinary approach

    NASA Astrophysics Data System (ADS)

    Bahrouni, N.; Bouaziz, S.; Soumaya, A.; Ben Ayed, N.; Attafi, K.; Houla, Y.; El Ghali, A.; Rebai, N.

    2014-04-01

    Due to its key position within the Africa-Europe convergence zone, Tunisia is marked by thrusting, folding, and faulting and has a major rupture zones associated with active faults. Consequently, most of Tunisian land is seismically active with significant active deformations, showing recent seismic events and their relative surface effects. This paper reports on several aspects of the seismotectonics, historical, and present-day seismicity and places them in the general tectonic and geodynamic framework of Tunisia. Field investigations, based on an integrated multidisciplinary approach, included (1) the identification of active faults, their motion and displacement, geomorphic aspects, and scarps and their relation with the general structural map of Tunisia and (2) an extensive analysis of brittle tectonic deformation affecting Quaternary deposits in several sites throughout Tunisia. The integration of field data within the existing data related to the seismic events that took place during the last decades allowed the establishment of an earthquake distribution map, as well as major seismic zones for better understanding of the seismicity database of Tunisia. To establish microzonation maps in seismic regions such as Gafsa and its surroundings, we have analyzed surface effects and secondary structures associated with active faults and correlated them with deformation rates, reconstructed for significant seismic events. Most faults exhibited typical left-stepping en-echelon with strike-slip component pattern suggesting that Tunisia is presently subjected to NNW-SSE compression. The focal mechanism of most Tunisia earthquakes combined with the existing tectonic and structural information and reconstruction of the Quaternary stress tensor allowed (a) better understanding of seismic zoning, (b) provided better assessment of the seismic hazard, and (c) facilitated the interpretation of the relationship between seismic zones and the geodynamic African-Eurasian plate

  7. Seismic site survey investigations in urban environments: The case of the underground metro project in Copenhagen, Denmark.

    NASA Astrophysics Data System (ADS)

    Martínez, K.; Mendoza, J. A.; Colberg-Larsen, J.; Ploug, C.

    2009-05-01

    Near surface geophysics applications are gaining more widespread use in geotechnical and engineering projects. The development of data acquisition, processing tools and interpretation methods have optimized survey time, reduced logistics costs and increase results reliability of seismic surveys during the last decades. However, the use of wide-scale geophysical methods under urban environments continues to face great challenges due to multiple noise sources and obstacles inherent to cities. A seismic pre-investigation was conducted to investigate the feasibility of using seismic methods to obtain information about the subsurface layer locations and media properties in Copenhagen. Such information is needed for hydrological, geotechnical and groundwater modeling related to the Cityringen underground metro project. The pre-investigation objectives were to validate methods in an urban environment and optimize field survey procedures, processing and interpretation methods in urban settings in the event of further seismic investigations. The geological setting at the survey site is characterized by several interlaced layers of clay, till and sand. These layers are found unevenly distributed throughout the city and present varying thickness, overlaying several different unit types of limestone at shallow depths. Specific results objectives were to map the bedrock surface, ascertain a structural geological framework and investigate bedrock media properties relevant to the construction design. The seismic test consisted of a combined seismic reflection and refraction analyses of a profile line conducted along an approximately 1400 m section in the northern part of Copenhagen, along the projected metro city line. The data acquisition was carried out using a 192 channels array, receiver groups with 5 m spacing and a Vibroseis as a source at 10 m spacing. Complementarily, six vertical seismic profiles (VSP) were performed at boreholes located along the line. The reflection

  8. 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.

  9. Information system evolution at the French National Network of Seismic Survey (BCSF-RENASS)

    NASA Astrophysics Data System (ADS)

    Engels, F.; Grunberg, M.

    2013-12-01

    The aging information system of the French National Network of Seismic Survey (BCSF-RENASS), located in Strasbourg (EOST), needed to be updated to satisfy new practices from Computer science world. The latter means to evolve our system at different levels : development method, datamining solutions, system administration. The new system had to provide more agility for incoming projects. The main difficulty was to maintain old system and the new one in parallel the time to validate new solutions with a restricted team. Solutions adopted here are coming from standards used by the seismological community and inspired by the state of the art of devops community. The new system is easier to maintain and take advantage of large community to find support. This poster introduces the new system and choosen solutions like Puppet, Fabric, MongoDB and FDSN Webservices.

  10. High resolution, shallow seismic reflection survey of the Pen Branch fault

    SciTech Connect

    Stieve, A.

    1991-05-15

    The purpose of this project, at the Savannah River River Site (SRS) was to acquire, process, and interpret 28 km (17.4 miles) of high resolution seismic reflection data taken across the trace of the Pen Branch fault and other suspected, intersecting north-south trending faults. The survey was optimized for the upper 300 ft of geologic strata in order to demonstrate the existence of very shallow, flat lying horizons, and to determine the depth of the fault or to sediments deformed by the fault. Field acquisition and processing parameters were selected to define small scale spatial variability and structural features in the vicinity of the Pen Branch fault leading to the definition and the location of the Pen Branch fault, the shallowest extent of the fault, and the quantification of the sense and magnitude of motion. Associated geophysical, borehole, and geologic data were incorporated into the investigation to assist in the determination of optimal parameters and aid in the interpretation.

  11. 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.

  12. Ground penetrating radar and active seismic investigation of stratigraphically verified pyroclastic deposits

    NASA Astrophysics Data System (ADS)

    Gase, A.; Bradford, J. H.; Brand, B. D.

    2015-12-01

    We conducted ground-penetrating radar (GPR) and active seismic surveys in July and August, 2015 parallel to outcrops of the pyroclastic density current deposits of the May 18th, 1980 eruption of Mount St. Helens (MSH), Washington. The primary objective of this study is to compare geophysical properties that influence electromagnetic and elastic wave velocities with stratigraphic parameters in the un-saturated zone. The deposits of interest are composed of pumice, volcanic ash, and lava blocks comprising a wide range of intrinsic porosities and grain sizes from sand to boulders. Single-offset GPR surveys for reflection data were performed with a Sensors and Software pulseEKKO Pro 100 GPR using 50 MHz, 100 MHz, and 200 MHz antennae. GPR data processing includes time-zero correction, dewow filter, migration, elevation correction. Multi-offset acquisition with 100 MHz antennae and offsets ranging from 1 m to 16 m are used for reflection tomography to create 2 D electromagnetic wave velocity models. Seismic surveys are performed with 72 geophones spaced at two meters using a sledge hammer source with shot points at each receiver point. We couple p- wave refraction tomography with Rayleigh wave inversion to compute Vp/Vs ratios. The two geophysical datasets are then compared with stratigraphic information to illustrate the influence of lithological parameters (e.g. stratification, grain-size distribution, porosity, and sorting) on geophysical properties of unsaturated pyroclastic deposits. Future work will include joint petrophysical inversion of the multiple datasets to estimate porosity and water content in the unsaturated zone.

  13. Fault Architecture of the Salton Sea through multi-scale Seismic Reflection Surveys

    NASA Astrophysics Data System (ADS)

    Kell, A. M.; Driscoll, N. W.; Kent, G.; Harding, A. J.; Baskin, R. L.

    2011-12-01

    Two sets of seismic reflection images collected in the Salton Sea, California in May 2010 and April 2011 highlight a longstanding episode of extension-related deformation within the Salton Sea pull-apart system. These data are part of a continued multi-scale network of seismic studies of the faults within the Salton Trough. In 2010, we collected ~350 line-km of data using a 75-m-long, 24-channel streamer and a 1.6kJ "sparker" source fired at 1.2 sec intervals. These images document a series of south-east dipping normal faults that are related to the current pull-apart geometry; this configuration appears to persist for only the past 20-40 ka. Newly acquired low fold images (~150 line-km) collected using a 300-m-long, 48-channel streamer and a Generator Injector (GI) airgun source firing at 1 min intervals show that the same structures seen in the higher resolution (2010) data as well as high-resolution seismic CHIRP images collected in 2007 (Brothers et al., 2009, 2010) continue to depths of >2.5 km. From this deeper imagery, we infer that the structures seen in the very shallow CHIRP data are through-going to seismogenic depths and play a dominant role in strain partitioning from the Imperial Fault to the San Andreas Fault through the Brawley Seismic Zone. The 2011 reflection and refraction data are part of a larger collaborative project involving Cal Tech, Virginia Tech, the USGS, University of Nevada, Reno and Scripps Institution of Oceanography. Within this study we seek to understand the mechanisms of how crustal thinning and rifting develops. The fault dip imaged at both scales is ~50-60° and show vertical offsets (sub-meter to tens of meters) distinguishable to the limits of our imaging resolution. These multi-scale data offer a unique opportunity to calculate the timing and mode of motion in the most actively deforming portion of the Salton Trough. The insights gained through these data allow a greater understanding of the tectonics and seismic hazards

  14. Seismic Refraction Surveys in Devils Lane and Cyclone Grabens, Canyonlands National Park, Utah

    NASA Astrophysics Data System (ADS)

    Kroeger, G. C.; Grosfils, E. B.; Schultz, R. A.; Reno, B. L.; Godchaux, J. D.

    2002-12-01

    Bounding fault offsets in the geologically young (60-70 ka) grabens of Canyonlands National Park have been estimated previously by adding measured scarp topography to estimates of sediment fill thickness beneath the graben floor. Published values of sediment fill thickness have ranged from 5-50 m with most estimates less than 20 m and most previous measured thickness in the 3-10 m range. We have conducted shallow seismic refraction surveys in two grabens, Devils Lane and Cyclone. Geophysical work in this remote area is difficult due to the lack of power or water supplies, the difficulty of vehicle transport over one of the most technical 4-wheel drive roads in Utah, and the environmentally sensitive nature of the cryptobiotic soils in the grabens. In Devils Lane graben, 10 24-channels spreads were employed in a 2 km long line along the axis of this 3 km long graben. A 15-station gravity survey was also conducted along the axis of this graben. Three separate seismic lines were used to sample the ends and center of Cyclone graben that is nearly twice as large as Devils Lane. The seismic data were modeled using iterative ray tracing. Our results from Devils Lane (Grosfils et al., JSG, in press) show a well-defined layer of basin sediment that deepens rapidly from the end of the graben, from depths of 30 m to over 90 m. Typical depths in the center of the graben range from 70-80 m. Under some portions of the line, the sediment thickness is so large that our cable lengths were not long enough to record the bedrock refraction, suggesting sediment thickness of over 100 m. Sediment velocities range from 700-900 m/s with underlying bedrock velocities averaging 3000 m/s. Our results from Cyclone graben are similar, with typical sediment thickness of 70-80 m in the center of the graben and abrupt shallowing at the ends of the graben. Our results indicate significantly thicker sediment fill than assumed in most previous studies and may necessitate revising estimates of both

  15. Constraining Subsurface Structure and Composition Using Seismic Refraction Surveys of Proglacial Valleys in the Cordillera Blanca, Peru

    NASA Astrophysics Data System (ADS)

    Glas, R. L.; Lautz, L.; McKenzie, J. M.; Mark, B. G.; Baker, E. A.; Aubry-Wake, C.; Somers, L. D.; Wigmore, O.

    2015-12-01

    As tropical glaciers rapidly recede in response to climate change, the storage and discharge of groundwater will play an increasing role in regulating river baseflow, particularly during the dry season, when stream flow is currently sustained predominantly by glacial melt. Little is understood regarding the hydrogeologic processes controlling base flow characteristics of low-gradient proglacial valleys of the Cordillera Blanca in Northwestern Peru, which has the world's highest density of tropical glaciers. To better understand the processes of groundwater storage and discharge in proglacial meadows, we completed seismic refraction surveys in three representative valleys of the Cordillera Blanca range: the Quilcayhuanca, Yanamarey, and Pachacoto valleys. The locations of survey transects were chosen based on locations of previous sediment core sampling, GPR lines, and quantification of groundwater-surface water interaction derived from dye and temperature tracing experiments. The seismic surveys consisted of 48 vertical component geophones with 2.5 m spacing. Across the three representative valleys a total of 15 surveys were conducted, covering a distance of 1800 m in cross, down, and oblique-valley directions. Preliminary interpretation of the seismic refraction data indicates a maximum imaging depth of 16 m below land surface, and a transition from glacio-lacustrine sediments to buried saturated talus at a depth of 6 m in the Quilcayhuanca valley. The organic-rich glacio-lacustrine sediments in the Yanamarey valley have seismic velocities ranging from 300 to 800 m/s and are >16 m in thickness at mid- valley. Weathered metasedimentary bedrock in the Pachacoto valley was imaged at ~5 m below the valley surface, exhibiting a p-wave velocity of 3400 m/s. The knowledge of hydrogeologic structure derived from seismic refraction surveys will provide crucial boundary conditions for future groundwater models of the valleys of the Cordillera Blanca.

  16. Reflection seismic survey across a fault zone in the Leinetal Graben, Germany, using P- and SH-waves

    NASA Astrophysics Data System (ADS)

    Musmann, P.; Polom, U.; Buness, H.; Thomas, R.

    2012-04-01

    Fault systems are considered as a valuable hydro-geothermal reservoir for heat and energy extraction, as permeability may be enhanced compared to the surrounding host rock. Seismic measurements are a well established tool to reveal their structure at depth. Apart from structural parameters like dip, extent and throw, they allow us to derive lithologic parameters, e.g. seismic velocities and impedance. Usually, only compressional waves have been used so far. In the context of the "gebo" Collaborative Research Program, seismic methods are revised to image and characterize geological fault zones in order to minimize the geological and technical risk for geothermal projects. In doing so, we evaluate and develop seismic acquisition, processing and interpretation techniques both for compressional and shear wave surveys to estimate the geothermal potential of fault zones. Here, we present results from high-resolution P- and SH-wave reflection seismic surveys along one and the same profile. They were carried out across the eastern border of the Leinetal Graben, Lower Saxony, Germany. At this survey site, primarily Triassic units crop out that are disrupted by major fault system probably extending down into Permian Zechstein. The seismic P-wave measurements (2.5 m CDP spacing, 20 - 180 Hz sweep sent out by a small vibrator) imaged the structure of the subsurface and its fault inventory with high resolution. Imaging ranges from approximately 50 m (base Keuper) to approximately 1.8 km (within Zechstein) depth. The profiles reveal that the area has undergone multiphase tectonics. This becomes manifest in a complex seismic reflection pattern. In addition the P-wave velocity model shows several features that can be related to folding and faulting. Preliminary results of the SH-wave measurements (0.5 m CDP spacing, 10 - 100 Hz sweep) show that the complex structural geological settings in the subsurface, as imaged by the P-wave survey, can also be imaged by a reflection shear

  17. Crustal seismicity and subduction morphology around Antofagasta, Chile: preliminary results from a microearthquake survey

    NASA Astrophysics Data System (ADS)

    Comte, D.; Pardo, M.; Dorbath, L.; Dorbath, C.; Haessler, H.; Rivera, L.; Cisternas, A.; Ponce, L.

    1992-04-01

    During September-October 1988, 13 analog and 16 digital seismographs were installed in northern Chile within 100 km around the city of Antofagasta (22.5-24.5°S; 68.5-70.5°W). The purposes of this study were to observe the microseismicity, to describe the morphology of the subducting slab near the southern edge of the rupture of the last great 1877 earthquake ( Mw= 8.8) in the northern Chile seismic gap, and to monitor the seismic activity probably associated with the Atacama fault system that is roughly parallel to the coast. The analysis of the analog records provides a total of 552 reliable events (2.0 < M < 5.0), whose hypocentres delineate the morphology of the subducting plate in the region. The Nazca plate subducts to the east with a dip of 10° along the trench from 22°S to 25°S down to 30 km depth. At 30-60 km depth a slight variation in the dip angle is observed from 17° (22-23.5°S) to 14° (24-25°S). Downplate, from 60 to 100 km in depth, the dip angle increases more rapidly to the north of 23.5°S than to the south of this latitude, where an almost constant dip (14-16°) is observed and the subducting plate becomes more subhorizontal. For greater depths (100-150 km), the dip of the subducting Nazca plate gradually varies from 36° to 18° between 22°S and 24.5°S. South of 24°S and below 100 km depth, an absence of seismicity is observed. However, a cluster of intermediate depth activity is located near the hypocentre of the December 9, 1950 ( Mw= 8.2) intraplate normal fault earthquake, around 500 km inland from the trench. Shallow seismicity (depth ⩽ 30 km) is located near the Atacama fault system. Focal mechanisms show normal faulting with slight left-lateral motion along an average strike in the north-northeast-south-southwest direction, which is in agreement with the observed superficial orientation of the fault. Shallow seismicity is also observed on the Mejillones Peninsula, the main irregularity along the coastline. Focal mechanisms of

  18. Site study plan for EDBH (Engineering Design Boreholes) seismic surveys, Deaf Smith County site, Texas: Revision 1

    SciTech Connect

    Hume, H.

    1987-12-01

    This site study plan describes seismic reflection surveys to run north-south and east-west across the Deaf Smith County site, and intersecting near the Engineering Design Boreholes (EDBH). Both conventional and shallow high-resolution surveys will be run. The field program has been designed to acquire subsurface geologic and stratigraphic data to address information/data needs resulting from Federal and State regulations and Repository program requirements. The data acquired by the conventional surveys will be common-depth- point, seismic reflection data optimized for reflection events that indicate geologic structure near the repository horizon. The data will also resolve the basement structure and shallow reflection events up to about the top of the evaporite sequence. Field acquisition includes a testing phase to check/select parameters and a production phase. The field data will be subjected immediately to conventional data processing and interpretation to determine if there are any anamolous structural for stratigraphic conditions that could affect the choice of the EDBH sites. After the EDBH's have been drilled and logged, including vertical seismic profiling, the data will be reprocessed and reinterpreted for detailed structural and stratigraphic information to guide shaft development. The shallow high-resulition seismic reflection lines will be run along the same alignments, but the lines will be shorter and limited to immediate vicinity of the EDBH sites. These lines are planned to detect faults or thick channel sands that may be present at the EDBH sites. 23 refs. , 7 figs., 5 tabs.

  19. Assessing risk of baleen whale hearing loss from seismic surveys: The effect of uncertainty and individual variation.

    PubMed

    Gedamke, Jason; Gales, Nick; Frydman, Sascha

    2011-01-01

    The potential for seismic airgun "shots" to cause acoustic trauma in marine mammals is poorly understood. There are just two empirical measurements of temporary threshold shift (TTS) onset levels from airgun-like sounds in odontocetes. Considering these limited data, a model was developed examining the impact of individual variability and uncertainty on risk assessment of baleen whale TTS from seismic surveys. In each of 100 simulations: 10000 "whales" are assigned TTS onset levels accounting for: inter-individual variation; uncertainty over the population's mean; and uncertainty over weighting of odontocete data to obtain baleen whale onset levels. Randomly distributed whales are exposed to one seismic survey passage with cumulative exposure level calculated. In the base scenario, 29% of whales (5th/95th percentiles of 10%/62%) approached to 1-1.2 km range were exposed to levels sufficient for TTS onset. By comparison, no whales are at risk outside 0.6 km when uncertainty and variability are not considered. Potentially "exposure altering" parameters (movement, avoidance, surfacing, and effective quiet) were also simulated. Until more research refines model inputs, the results suggest a reasonable likelihood that whales at a kilometer or more from seismic surveys could potentially be susceptible to TTS and demonstrate that the large impact uncertainty and variability can have on risk assessment.

  20. Sourcebook of locations of geophysical surveys in tunnels and horizontal holes including results of seismic-refraction surveys: Rainier Mesa, Aqueduct Mesa, and Area 16, Nevada Test Site

    SciTech Connect

    Carroll, R.D.; Kibler, J.E.

    1983-01-01

    Seismic refraction surveys have been obtained sporadically in tunnels in zeolitized tuff at the Nevada Test Site since the late 1950's. Commencing in 1967 and continuing to date (1982), extensive measurements of shear- and compressional-wave velocities have been made in five tunnel complexes in Rainier and Aqueduct Mesas and in one tunnel complex in Shoshone Mountain. The results of these surveys to 1980 are compiled in this report. In addition, extensive horizontal drilling was initiated in 1967 in connection with geologic exploration in these tunnel complexes for sites for nuclear weapons tests. Seismic and electrical surveys were conducted in the majority of these holes. The type and location of these tunnel and borehole surveys are indexed in this report. Synthesis of the seismic refraction data indicates a mean compressional-wave velocity near the nuclear device point (WP) of 23 tunnel events of 2430 m/s (7970 f/s) with a range of 1846 to 2753 m/s (6060 to 9030 f/s). The mean shear-wave velocity of 17 tunnel events is 1276 m/s (4190 f/s) with a range of 1140 to 1392 m/s (3740 to 4570 f/s). Experience indicates that these velocity variations are due chiefly to the extent of fracturing and (or) the presence of partially saturated rock in the region of the survey.

  1. Sourcebook of locations of geophysical surveys in tunnels and horizontal holes, including results of seismic refraction surveys, Rainier Mesa, Aqueduct Mesa, and Area 16, Nevada Test Site

    USGS Publications Warehouse

    Carroll, R.D.; Kibler, J.E.

    1983-01-01

    Seismic refraction surveys have been obtained sporadically in tunnels in zeolitized tuff at the Nevada Test Site since the late 1950's. Commencing in 1967 and continuing to date (1982), .extensive measurements of shear- and compressional-wave velocities have been made in five tunnel complexes in Rainier and Aqueduct Mesas and in one tunnel complex in Shoshone Mountain. The results of these surveys to 1980 are compiled in this report. In addition, extensive horizontal drilling was initiated in 1967 in connection with geologic exploration in these tunnel complexes for sites for nuclear weapons tests. Seismic and electrical surveys were conducted in the majority of these holes. The type and location of these tunnel and borehole surveys are indexed in this report. Synthesis of the seismic refraction data indicates a mean compressional-wave velocity near the nuclear device point (WP) of 23 tunnel events of 2,430 m/s (7,970 f/s) with a range of 1,846-2,753 m/s (6,060-9,030 f/s). The mean shear-wave velocity of 17 tunnel events is 1,276 m/s (4,190 f/s) with a range of 1,140-1,392 m/s (3,740-4,570 f/s). Experience indicates that these velocity variations are due chiefly to the extent of fracturing and (or) the presence of partially saturated rock in the region of the survey.

  2. Seismic reflection survey of the crustal structure beneath Unzen volcano, Kyushu, Japan

    NASA Astrophysics Data System (ADS)

    Matsumoto, Satoshi; Shimizu, Hiroshi; Onishi, Masazumi; Uehira, Kenji

    2012-05-01

    Unzen volcano is located in the western part of Kyushu, Japan. We carried out a seismic reflection survey at Unzen volcano in order to elucidate the structure of the volcano. Although the survey was conducted in a volcanic area under difficult conditions, such as artificial noises and a complex structure, we were able to resolve the structure beneath the profile using vibrator sources and a large number of stacking signals. The processed depth sections confirmed that Unzen volcano developed in a graben structure, as has been suggested in other geological studies. We imaged many subsurface normal faults shallower than 1 km. These faults, mostly covered with volcanic lava and deposits, were identified at the surface. Strong reflectors were found at a depth of approximately 3 km. They were located just above the pressure source of the latest eruption, as inferred from geodetic data. The geometric relationship between the reflection image, the pressure source location, and the lava dome suggests that the conduit from the lava dome could connect to the magma chamber located 4 km away from the lava dome.

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

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

    The author has identified the following significant results. The sharp bend in the Alaska Range near 65 deg N, 150 deg W in now thought to enclose a corner of the northwesterly migrating north Pacific lithospheric plate. Subduction of the plate beneath the continent is believed, on the basis of hypocentral distribution, to occur along Cook Inlet and the eastern flanks of the Aleutian and Alaska Ranges as far northward as Mt. McKinley. The nature of tectonic deformation here, particularly in the area of the bend in the Alaska Range, is understandably complex. The Denali fault is thought to be a transform character in the vicinity of Mt. McKinley (i.e., it is thought to be the surface along which the oceanic plate separates from the continental plate). On the ERTS-1 imagery, however, it appears that there are a number of sub-parallel faults which branch off of the Denali fault in a southwesterly direction. Slippage along these would tend to squeeze material around the inside of the band rather than the plate being directly underthrust. All of these sub-parallel faults are seismically active. The right-lateral fault-plane solution obtained for this event is consistent with the concept of slippage around the bend on a set of sub-parallel faults in the manner postulated. The best images to show these features are 1066-20444 and 1266-20572.

  4. Archive of digital boomer seismic reflection data collected during USGS field activity 04SGI01 in the Withlacoochee River of West-Central Florida, March 2004

    USGS Publications Warehouse

    Calderon, Karynna; Dadisman, Shawn V.; Yobbi, Dann K.; McBride, W. Scott; Flocks, James G.; Wiese, Dana S.

    2006-01-01

    In March of 2004, the U.S. Geological Survey conducted a geophysical survey in the Withlacoochee River of west-central Florida. This report serves as an archive of unprocessed digital boomer seismic reflection data, trackline maps, navigation files, GIS information, Field Activity Collection System (FACS) logs, observer's logbook, and FGDC metadata. Filtered and gained digital images of the seismic profiles are also provided. Refer to the Acronyms page for expansion of all acronyms and abbreviations used in this report. The archived trace data are in standard Society of Exploration Geophysicists (SEG) SEG-Y format (Barry and others, 1975) and may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU). Example SU processing scripts and USGS software for viewing the SEG-Y files (Zihlman, 1992) are also provided.

  5. Deep crustal structure of the North-West African margin from combined wide-angle and reflection seismic data (MIRROR seismic survey)

    NASA Astrophysics Data System (ADS)

    Biari, Y.; Klingelhoefer, F.; Sahabi, M.; Aslanian, D.; Schnurle, P.; Berglar, K.; Moulin, M.; Mehdi, K.; Graindorge, D.; Evain, M.; Benabdellouahed, M.; Reichert, C.

    2015-08-01

    The structure of the Moroccan and Nova Scotia conjugate rifted margins is of key importance for understanding the Mesozoic break-up and evolution of the northern central Atlantic Ocean basin. Seven combined multichannel reflection (MCS) and wide-angle seismic (OBS) data profiles were acquired along the Atlantic Moroccan margin between the latitudes of 31.5° and 33° N during the MIRROR seismic survey in 2011, in order to image the transition from continental to oceanic crust, to study the variation in crustal structure, and to characterize the crust under the West African Coast Magnetic Anomaly (WACMA). The data were modeled using a forward modeling approach. The final models image crustal thinning from 36 km thickness below the continent to approximately 8 km in the oceanic domain. A 100 km wide zone characterized by rough basement topography and high seismic velocities up to 7.4 km/s in the lower crust is observed westward of the West African Coast Magnetic Anomaly. No basin underlain by continental crust has been imaged in this region, as has been identified north of our study area. Comparison to the conjugate Nova Scotian margin shows a similar continental crustal thickness and layer geometry, and the existence of exhumed and serpentinized upper mantle material on the Canadian side only. The oceanic crustal thickness is lower on the Canadian margin.

  6. 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.

  7. Urban Reflection Seismics: A High-resolution Shear-wave Survey in the Trondheim harbour area, Norway

    NASA Astrophysics Data System (ADS)

    Krawczyk, Charlotte; Polom, Ulrich; L'Heureux, Jean-Sebastien; Hansen, Louise; Lecomte, Isabelle; Longva, Oddva

    2010-05-01

    A shallow reflection shear-wave seismic survey was carried out in mid summer 2008 in the harbour area of Trondheim, Norway, that suffers from prominent landslide events in the last decades. The harbour has been built on man-made land fillings at the coast of the Trondheim Fjord in several expansions implicated in some submarine landslides, which are reported since about 100 years. Whereas high-resolution marine seismic methods mapped the fjord area in detail in the range of decimeters, the seismic investigation below the infilled and paved harbour area was a difficult challenge. Therefore, SH-polarized shear-wave reflection seismics was applied experimentally, and the field configuration was especially adapted for the application on paved surfaces with underlying soft soil of estimated more than 150 m thickness. A land streamer system of 120 channels (geophone interval of 1 m) was used in combination with LIAG's newly developed shear-wave vibrator buggy of 30 kN peak force. This mini truck is designed for full environment-friendly urban use and enables fast and sensitive operation within a seismic survey area. The sweep parameters were configured to 25-100 Hz range, 10 s duration, using 14 s recording time sampled by 1 ms interval. Shear wave frequencies above the used frequency range, which can also be generated by the seismic source, were avoided consciously to prevent disturbing air wave reflections during operation. For an advantageous solution for the seismic imaging of the subsoil down to the bedrock a grid of 4.2 profile-km was gathered. The data recorded experimentally in the initial seismic survey stage achieved finally a highly resolved image of the structure of the sediment body with ca. 1 m vertical resolution, clear detection of the bedrock, and probably deeper structures. The profiles were processed up to FD time migration, and indicate that slip planes, turbidity masses and other features relevant for geohazards are present within the top of the

  8. Urban Shear-wave Reflection Seismics: A High-resolution Survey in the Landslide-affected Trondheim Harbour Area, Norway

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

    A shallow reflection shear-wave seismic survey was carried out in mid summer 2008 in the harbour area of Trondheim, Norway, that suffers from prominent landslide events in the last decades. The harbour has been built on man-made land fillings at the coast of the Trondheim Fjord in several expansions implicated in some submarine landslides. Whereas high-resolution marine seismic methods mapped the fjord area in detail, common seismic investigation of the infilled, paved harbour area was a difficult challenge. Therefore, SH-polarized shear-wave reflection seismics was applied experimentally, and the field configuration was especially adapted for the application on paved surfaces with underlying soft soil of more than 100 m thickness. A land streamer system of 120 channels (geophone interval of 1 m) was used in combination with LIAG's newly developed shear-wave vibrator buggy of 30 kN peak force. This mini truck is full environment-friendly for urban use and enables fast operation within a seismic survey area. The sweep parameters were configured to 25-100 Hz range, 10 s duration, using 14 s recording time sampled by 1 ms interval. Shear wave frequencies above the used frequency range, which can also be generated by the seismic source, were avoided consciously to prevent disturbing air wave reflections during operation. For an advantageous solution for the seismic imaging of the subsoil down to the bedrock ca. 4 km of 2.5-D profiles were gathered. The data recorded experimentally in the initial seismic survey stage achieved finally a highly resolved image of the structure of the sediment body with 1 m vertical resolution, clear detection of the bedrock, and probably deeper structures. These were processed up to FD time migration, and indicate that slip planes are present within the top of 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 dynamic stiffness of the

  9. Three dimensional marine seismic survey has no measurable effect on species richness or abundance of a coral reef associated fish community.

    PubMed

    Miller, Ian; Cripps, Edward

    2013-12-15

    Underwater visual census was used to determine the effect of a three dimensional seismic survey on the shallow water coral reef slope associated fish community at Scott Reef. A census of the fish community was conducted on six locations at Scott Reef both before and after the survey. The census included small site attached demersal species belonging to the family Pomacentridae and larger roving demersal species belonging to the non-Pomacentridae families. These data were combined with a decade of historical data to assess the impact of the seismic survey. Taking into account spatial, temporal, spatio-temporal and observer variability, modelling showed no significant effect of the seismic survey on the overall abundance or species richness of Pomacentridae or non-Pomacentridae. The six most abundant species were also analysed individually. In all cases no detectable effect of the seismic survey was found on the abundance of these fish species at Scott Reef.

  10. 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

  11. 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.

    2016-03-02

    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.

  12. 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.

  13. Active Source Seismic Experiment Peers Under Soufrière Hills Volcano

    NASA Astrophysics Data System (ADS)

    Voight, Barry; Sparks, R. S. J.; Hammond, J.; Shalev, E.; Malin, P.; Kenedi, C.; Minshull, T. A.; Paulatto, M.; Mattioli, G.; Hidayat, D.; Widiwijayanti, C.

    2010-07-01

    Characterizing internal structures of active volcanoes remains an enigmatic issue in geosciences. Yet studies of such structures can greatly improve hazard assessments, helping scientists to better monitor seismic signatures, geodetic deformation, and gas emissions, data that can be used to improve models and forecasts of future eruptions. Several passive seismic tomography experiments—which use travel times of seismic waves from natural earthquakes to image underground structures—have been conducted at active volcanoes (Hawaii's Kilauea, Washington's Mount St. Helens, Italy's Etna, and Japan's Unzen), but an inhomogeneous distribution of earthquakes compromises resolution. Further, if volcanic earthquakes are dominantly shallow at a given location, passive methods are limited to studying only shallow features. Thus, active source experiments—where seismic waves from the explosion of deliberately set charges are used to image below the surface—hold great potential to illuminate structures not readily seen through passive measures.

  14. Delineation of Active Basement Faults in the Eastern Tennessee and Charlevoix Intraplate Seismic Zones

    NASA Astrophysics Data System (ADS)

    Powell, C. A.; Langston, C. A.; Cooley, M.

    2013-12-01

    Recognition of distinct, seismogenic basement faults within the eastern Tennessee seismic zone (ETSZ) and the Charlevoix seismic zone (CSZ) is now possible using local earthquake tomography and datasets containing a sufficiently large number of earthquakes. Unlike the New Madrid seismic zone where seismicity clearly defines active fault segments, earthquake activity in the ETSZ and CSZ appears diffuse. New arrival time inversions for hypocenter relocations and 3-D velocity variations using datasets in excess of 1000 earthquakes suggest the presence of distinct basement faults in both seismic zones. In the ETSZ, relocated hypocenters align in near-vertical segments trending NE-SW, parallel to the long dimension of the seismic zone. Earthquakes in the most seismogenic portion of the ETSZ delineate another set of near-vertical faults trending roughly E-ESE. These apparent trends and steep dips are compatible with ETSZ focal mechanism solutions. The solutions are remarkably consistent and indicate strike-slip motion along the entire length of the seismic zone. Relocated hypocenter clusters in the CSZ define planes that trend and dip in directions that are compatible with known Iapitan rift faults. Seismicity defining the planes becomes disrupted where the rift faults encounter a major zone of deformation produced by a Devonian meteor impact. We will perform a joint statistical analysis of hypocenter alignments and focal mechanism nodal plane orientations in the ETSZ and the CSZ to determine the spatial orientations of dominant seismogenic basement faults. Quantifying the locations and dimensions of active basement faults will be important for seismic hazard assessment and for models addressing the driving mechanisms for these intraplate zones.

  15. On interrelation between seismic activity and the Earth crust deformations of Vrancea zone

    NASA Astrophysics Data System (ADS)

    Dultsev, A.; Pronyshyn, R.; Siejka, Z.; Serant, O.; Tretyak, K.; Zablotskyj, F.

    2009-04-01

    An investigated territory covers the whole seismically active zone of Vrancea mountains (Romania). It is located between 43° and 47° parallels in latitude and 23° and 29° meridians in longitude. The weekly solutions of coordinates of six permanent stations (BACA, BAIA, BUCU, COST, DEVA, IGEO) allocated on the territories of Romania and Moldova have been used as the initial data for carrying out of the investigations. These initial data were obtained during 2007-2008. The results of determination of the earthquake parameters (coordinates, focal depth, magnitude and energy) have been obtained from a network of seismic stations. An analysis of the temporal earthquake distribution in 2007-2008 showed the alternation of the periods of seismic activity and its absence. The duration of these periods ranges from one to three weeks. The Earth crust deformation parameters between the recurrent periods of seismic activity and its absence have been calculated on basis of weekly solutions for the territory bounded by GPS-permanent stations. The accumulative values of the earthquake energy and magnitude were calculated for the periods of seismic activity. It had been ascertained that the territory of Vrancea zone undergoes the permanent stretching into northeast and southwest directions as well as the compressing into northwest and southeast ones. In fact, the more fast attenuation of the seismic waves occurs in the direction of the contraction axis and the slowest attenuation of ones occurs in the direction of the axis of elongation. The parameters of total amplitude and earthquake energy in the periods of seismic activity have high-degree correlation with difference of the deformations of next periods of seismic activity and its absence. It enables to predict a change of the deformation increment in the zone of earthquake focuses of Vrancea territory by means of the earthquake total force.

  16. Balancing Mitigation Against Impact: A Case Study From the 2005 Chicxulub Seismic Survey

    NASA Astrophysics Data System (ADS)

    Barton, P.; Diebold, J.; Gulick, S.

    2006-05-01

    In early 2005 the R/V Maurice Ewing conducted a large-scale deep seismic reflection-refraction survey offshore Yucatan, Mexico, to investigate the internal structure of the Chicxulub impact crater, centred on the coastline. Shots from a tuned 20 airgun, 6970 cu in array were recorded on a 6 km streamer and 25 ocean bottom seismometers (OBS). The water is exceptionally shallow to large distances offshore, reaching 30 m about 60 km from the land, making it unattractive to the larger marine mammals, although there are small populations of Atlantic and spotted dolphins living in the area, as well as several turtle breeding and feeding grounds on the Yucatan peninsula. In the light of calibrated tests of the Ewing's array (Tolstoy et al., 2004, Geophysical Research Letters 31, L14310), a 180 dB safety radius of 3.5 km around the gun array was adopted. An energetic campaign was organised by environmentalists opposing the work. In addition to the usual precautions of visual and listening watches by independent observers, gradual ramp-ups of the gun arrays, and power-downs or shut-downs for sightings, constraints were also placed to limit the survey to daylight hours and weather conditions not exceeding Beaufort 4. The operations were subject to several on-board inspections by the Mexican environmental authorities, causing logistical difficulties. Although less than 1% of the total working time was lost to shutdowns due to actual observation of dolphins or turtles, approximately 60% of the cruise time was taken up in precautionary inactivity. A diver in the water 3.5 km from the profiling ship reported that the sound in the water was barely noticeable, leading us to examine the actual sound levels recorded by both the 6 km streamer and the OBS hydrophones. The datasets are highly self-consistent, and give the same pattern of decay with distance past about 2 km offset, but with different overall levels: this may be due to geometry or calibration differences under

  17. 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

  18. Method of attenuating sea ice flexure noise during seismic surveys of permafrost regions involving a precursor aerial and/or satellite mapping step

    SciTech Connect

    Ostrander, W.J.

    1986-11-04

    This patent describes a method of improving resolution of seismic data collected in a transition zone of a permafrost region between a frozen land mass and an adjacent sea-ice region. The data is collected by common midpoint (CMP) collection methods including sequentially activating at least one conventional vibratory source at a series of sourcepoint locations across the surface of the permafrost region. In this region the amplitude and phase spectra of the generated energy are controlled so that the generated energy changes smoothly as a function of time, and redundantly collection reflections thereof via a series of receivers at receiver stations provide 2-dimensional multifold coverage of the subsurface along a survey line. The method comprises: (a) adopting a survey strategy wherein the sourcepoint locations established for the at least one vibratory source, are always separated from the receiver stations by one or more ice fracture areas formed on or about the surface of the along the survey line; and (b) generating seismic field records by positioning and employing the at least one vibratory source and the series of receivers in accordance with the collection strategy of step (a) such that individual sourcepoint-receiver station locations can be redundantly associated with a selected number of traces to form a series of CMP gathers.

  19. Structure and Velocities of the Northeastern Santa Cruz Mountains and the Western Santa Clara Valley, California, from the SCSI-LR Seismic Survey

    USGS Publications Warehouse

    Catchings, R.D.; Goldman, M.R.; Gandhok, G.

    2006-01-01

    Introduction: The Santa Clara Valley is located in the southern San Francisco Bay area of California and generally includes the area south of the San Francisco Bay between the Santa Cruz Mountains on the southwest and the Diablo Ranges on the northeast. The area has a population of approximately 1.7 million including the city of San Jose, numerous smaller cities, and much of the high-technology manufacturing and research area commonly referred to as the Silicon Valley. Major active strands of the San Andreas Fault system bound the Santa Clara Valley, including the San Andreas fault to the southwest and the Hayward and Calaveras faults to the northeast; related faults likely underlie the alluvium of the valley. This report focuses on subsurface structures of the western Santa Clara Valley and the northeastern Santa Cruz Mountains and their potential effects on earthquake hazards and ground-water resource management in the area. Earthquake hazards and ground-water resources in the Santa Clara Valley are important considerations to California and the Nation because of the valley's preeminence as a major technical and industrial center, proximity to major earthquakes faults, and large population. To assess the earthquake hazards of the Santa Clara Valley better, the U.S. Geological Survey (USGS) has undertaken a program to evaluate potential earthquake sources and potential effects of strong ground shaking within the valley. As part of that program, and to better assess water resources of the valley, the USGS and the Santa Clara Valley Water District (SCVWD) began conducting collaborative studies to characterize the faults, stratigraphy, and structures beneath the alluvial cover of the Santa Clara Valley in the year 2000. Such geologic features are important to both agencies because they directly influence the availability and management of groundwater resources in the valley, and they affect the severity and distribution of strong shaking from local or regional

  20. Sensing network for electromagnetic fields generated by seismic activities

    NASA Astrophysics Data System (ADS)

    Gershenzon, Naum I.; Bambakidis, Gust; Ternovskiy, Igor V.

    2014-06-01

    The sensors network is becoming prolific and play now increasingly more important role in acquiring and processing information. Cyber-Physical Systems are focusing on investigation of integrated systems that includes sensing, networking, and computations. The physics of the seismic measurement and electromagnetic field measurement requires special consideration how to design electromagnetic field measurement networks for both research and detection earthquakes and explosions along with the seismic measurement networks. In addition, the electromagnetic sensor network itself could be designed and deployed, as a research tool with great deal of flexibility, the placement of the measuring nodes must be design based on systematic analysis of the seismic-electromagnetic interaction. In this article, we review the observations of the co-seismic electromagnetic field generated by earthquakes and man-made sources such as vibrations and explosions. The theoretical investigation allows the distribution of sensor nodes to be optimized and could be used to support existing geological networks. The placement of sensor nodes have to be determined based on physics of electromagnetic field distribution above the ground level. The results of theoretical investigations of seismo-electromagnetic phenomena are considered in Section I. First, we compare the relative contribution of various types of mechano-electromagnetic mechanisms and then analyze in detail the calculation of electromagnetic fields generated by piezomagnetic and electrokinetic effects.

  1. National Archive of Marine Seismic Surveys (NAMSS): Status Report on U.S. Geological Survey Program Providing Access to Proprietary Data

    NASA Astrophysics Data System (ADS)

    Hart, P. E.; Childs, J. R.

    2005-05-01

    During the last four decades, hundreds of thousands of line kilometers of 2D marine seismic reflection data have been collected by the hydrocarbon exploration industry within the United States Exclusive Economic Zone. The commercial value of much of these data has decreased significantly because of drilling moratoria and new technology such as 3D acquisition. However, these data still have tremendous value for scientific research and education purposes. The U.S. Geological Survey has recently made agreements with two commercial owners of large data holdings to transfer to the public domain over 250,000 line kilometers of marine data from off the eastern, western, and Alaskan coasts of the United States. In order to provide access to the data, the USGS has developed the National Archive of Marine Seismic Surveys (NAMSS) program. For a small fraction of the money that would be required to collect new data, work is underway to organize and recover digital data currently stored on tens of thousands of 9-track tapes. Even where new data collection efforts could be funded, current environmental restrictions on marine seismic exploration could preclude operations. The NAMSS web site at http://walrus.wr.usgs.gov/NAMSS/ has trackline maps of surveys that are now or will soon be available for downloading in SEG-Y format. As more owners and users become aware of this new data resource, it is hoped that additional partners in will join this data rescue effort.

  2. 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.

  3. Evidence of a possible NNE-trending fault zone in the Summerville, South Carolina, area from shallow seismic reflection surveys

    SciTech Connect

    Marple, R.T.; Talwani, P. . Geology Dept.)

    1994-03-01

    Five high-resolution seismic-reflection surveys trending approximately WNW-ESE and totaling about 31 km were acquired in the Summerville, South Carolina, area. The surveys trend across the postulated Woodstock fault zone. These newly acquired data together with earlier data revealed the existence of an [approximately]50-km-long feature associated with gentle warping of the shallow sediments that lies along a recently described zone of river anomalies (ZRA). The first ([approximately]5.9-km-long) seismic reflection profile located about 14 km NNE of Summerville revealed that the J reflector (basalt) at about 670 m depth is offset about 30--40 m with the west side up. The overlying sediments displayed upwarping rather than brittle offset. A second ([approximately]6.7-km-long) survey located along interstate Highway 26 revealed as much as 30--40 m of upwarping of the sediments above about 450 m depth. A third ([approximately]7.3-km-long) profile acquired through the town of Summerville revealed four, [approximately]200--300 m wide, nearly vertical zones in which the reflectors are noncoherent. Away from these zones the reflectors are relatively flat and are slightly higher on the west side of each zone. The fourth (3-km-long) survey was located about 5 km SW of Middleton Gardens and indicated minor faulting at about 500 m depth. The fifth ([approximately]6.4-km-long) seismic survey acquired just north of Ravenel revealed an [approximately]0.5-km-wide zone in which the reflectors in the top 350 m displayed as much as 20 m of upwarping. On all the surveys, except for the first, the basalt was at too great a depth to be resolved.

  4. A Seismic Reflection Profiling Survey of Lake Toba, Sumatra, Indonesia: Preliminary Findings from the Field

    NASA Astrophysics Data System (ADS)

    Chesner, C. A.; Dolan, M. T.; Halsor, S. P.; Bohnenstiehl, D. R.; Liu, J.; Nasution, A.

    2012-12-01

    Lake Toba lies within the giant Toba Caldera that last erupted 74,000 years ago. In its early history, Lake Toba may have covered about 1800 km2, possibly reaching depths of 750 m. The central portion of the 100 x 30 km caldera has since been uplifted to form the asymmetrical Samosir Island resurgent dome (60 x 20 km). Its upper surface dips gently to the west while its eastern margin consists of a series of parallel normal faults with total displacement of at least 1100 m. Several lava domes have been emplaced along these faults as well as the southwestern caldera ring fracture. At least 30 m of laminated tuffaceous sand and silt, diatomaceous clay, diatomites, and volcanic ash cover Samosir Island and sediments up to 100 m have been reported. In an effort to understand the post-collapse sedimentation, structural, volcanic, and resurgent histories of the caldera, we conducted a 14 day seismic reflection profiling survey of Lake Toba in July/August 2012. An EdgeTech SB-512i "chirp" sonar unit was towed across about 900 km of transect lines. Signal penetration was not affected by water depth, which sometimes exceeded 500 m, but was often reduced by adverse tow conditions or strong stratigraphic reflectors, and occasionally lost altogether possibly due to gas pockets in the sediments. In areas of flat-lying or gently sloping lake bottom, about 10-30 m of lake sediments was typically detected. Along the steep caldera bounding faults and the faulted eastern margin of the Samosir resurgent dome virtually no sediments were detected. However, up to 90 m of laminated sediments were apparent on the crest and gently sloping submerged portions of Samosir. These thick sedimentary sequences showed distinct marker horizons with evidence of faulting, folding, sliding, and slumping. Local unconformities or onlapping sequences demonstrated discrete sedimentary episodes. Several subaqueous lava domes were discovered that uplifted, folded, and sometimes truncated the sedimentary

  5. Seismic investigation of gas hydrates in the Gulf of Mexico: Results from 2013 high-resolution 2D and multicomponent seismic surveys

    NASA Astrophysics Data System (ADS)

    Haines, S. S.; Hart, P. E.; Shedd, W. W.; Frye, M.; Agena, W.; Miller, J. J.; Ruppel, C. D.

    2013-12-01

    In the spring of 2013, the U.S. Geological Survey led a 16-day seismic acquisition cruise aboard the R/V Pelican in the Gulf of Mexico to survey two established gas hydrate study sites. We used a pair of 105/105 cubic inch generator/injector airguns as the seismic source, and a 450-m 72-channel hydrophone streamer to record two-dimensional (2D) data. In addition, we also deployed at both sites an array of 4-component ocean-bottom seismometers (OBS) to record P- and S-wave energy at the seafloor from the same seismic source positions as the streamer data. At lease block Green Canyon 955 (GC955), we acquired 400 km of 2-D streamer data, in a 50- to 250-m-spaced grid augmented by several 20-km transects that provide long offsets for the OBS. The seafloor recording at GC955 was accomplished by a 2D array of 21 OBS at approximately 400-m spacing, including instruments carefully positioned at two of the three boreholes where extensive logging-while-drilling data is available to characterize the presence of gas hydrate. At lease block Walker Ridge 313 (WR313), we acquired 450 km of streamer data in a set of 11-km, 150- to 1,000-m-spaced, dip lines and 6- to 8-km, 500- to 1000-m-spaced strike lines. These were augmented by a set of 20-km lines that provide long offsets for a predominantly linear array of 25 400- to 800-m spaced OBS deployed in the dip direction in and around WR313. The 2D data provide at least five times better resolution of the gas hydrate stability zone than the available petroleum industry seismic data from the area; this enables considerably improved analysis and interpretation of stratigraphic and structural features including previously unseen faults and gas chimneys that may have considerable impact on gas migration. Initial processing indicates that the OBS data quality is good, and we anticipate that these data will yield estimates of P- and S-wave velocities, as well as PP (reflected) and PS (converted wave) images beneath each sensor location.

  6. Pacific Upper Mantle Seismic Anisotropy from the Active-Source Seismic Component of the NoMelt Experiment

    NASA Astrophysics Data System (ADS)

    Mark, H. F.; Lizarralde, D.; Gaherty, J. B.; Collins, J. A.; Hirth, G.; Evans, R. L.

    2014-12-01

    We will present a measurement of azimuthal seismic anisotropy of Pacific-plate upper mantle based on Pn travel times from the active-source seismic component of the NoMelt experiment. The NoMelt experiment was conducted in 2012 on ~70-m.y.-old lithosphere, in the center of the spreading segment between the Clarion and Clipperton fracture zones, with the goal of delineating the detailed seismic and electrical structure of "normal," mature oceanic lithosphere. The seismic component of the experiment consisted of a 600x400 km array of 27 broad-band (BB) ocean bottom seismometers (OBS); 31 short period (SP) OBS, spaced at 20 km, deployed along the long axis of the array (the main transect), oriented along a plate-kinematic flow line; and 3 SP OBS deployed along a line normal to the main transect, at 50 km spacing, extending to 200 km southeast of the center of the main transect. The SP OBS array was deployed to record airgun shots fired by the R/V M.G. Langseth's 36-element array. Airgun shots were fired along the two perpendicular lines and also along a semi-circular arc with a 75-km radius centered at the line intersection at the center of the main transect. Pn (upper mantle refraction) arrivals from shots fired along the semicircle and recorded by OBS within the semicircle's arc span 180 degrees of azimuth and an offset range of ~40-150 km. Preliminary analyses of these Pn arrival travel times indicate an azimuthal dependence of P-wave speeds, which range from ~8.6 km/s to ~7.6 km/s. These preliminary results suggest a pattern of azimuthal wave-speed dependence that requires depth-dependent seismic anisotropy and/or a dipping mantle fabric, with the latter being more likely given the limited range of source/receiver offsets spanned by the Pn arrivals used in this analysis. We will present results that include these observations as well as Pn arrivals from a much more comprehensive set of source/receiver pairs from the NoMelt experiment.

  7. US Geological Survey begins seismic ground response experiments in Washington State

    USGS Publications Warehouse

    Tarr, A.C.; King, K.W.

    1988-01-01

    This article briefly describes the experimental monitoring of minor seismic features caused by distant nuclear explosions, mining blasts and rhythmic human pushing against wooden homes. Some means of response prediction are outlined in Washington State and some effects of seismic amplification by weak clayey sediments are described. The results of several experiments are described. -A.Scarth

  8. 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

  9. 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.

  10. A preliminary summary of a seismic-refraction survey in the vicinity of the Tonto Forest Observatory, Arizona

    USGS Publications Warehouse

    Roller, J.C.; Jackson, W.H.; Warren, D.H.; Healy, J.H.

    1964-01-01

    The U.S. Geological Survey complete d a seismic-refraction survey in the vicinity of the Tonto Forest Seismological Observatory (T.F.S.O.) in April and May 1964. More than 1200 km of reversed profiles were surveyed to determine the crustal structure and crustal and upper mantle velocities in this area. The purpose of this work was to provide information on wave-propagation paths of seismic events recorded at T.F.S.O. and to improve the performance of the Observatory in locating and identifying these events. First arrivals indicate that the Mohorovicic discontinuity dips to the northeast by as much as 6 degrees under T.F.S.O., and may even be displaced vertically by as much as 5 km immediately north of the Observatory near the boundary of the Basin and Range a n d t he Colorado Plateau Provinces. A preliminary examination of the first arrivals indicates that the crust at T.F.S.O. is at least 30 km thick and is made up of at least two seismic layers. A thin veneer at the surface with a velocity of approximately 4 km/sec is underlain by a layer with a velocity of approximately 5.9 km/sec to 6.1 km/sec. An intermediate layer with velocity of 6.6 to 7.0 km/sec is probably present in the lower crust, but is not revealed by first arrivals. The velocity of seismic waves in the upper mantle is about 7.9 km/sec.

  11. Seismic Activity at tres Virgenes Volcanic and Geothermal Field

    NASA Astrophysics Data System (ADS)

    Antayhua, Y. T.; Lermo, J.; Quintanar, L.; Campos-Enriquez, J. O.

    2013-05-01

    The volcanic and geothermal field Tres Virgenes is in the NE portion of Baja California Sur State, Mexico, between -112°20'and -112°40' longitudes, and 27°25' to 27°36' latitudes. Since 2003 Power Federal Commission and the Engineering Institute of the National Autonomous University of Mexico (UNAM) initiated a seismic monitoring program. The seismograph network installed inside and around the geothermal field consisted, at the beginning, of Kinemetrics K2 accelerometers; since 2009 the network is composed by Guralp CMG-6TD broadband seismometers. The seismic data used in this study covered the period from September 2003 - November 2011. We relocated 118 earthquakes with epicenter in the zone of study recorded in most of the seismic stations. The events analysed have shallow depths (≤10 km), coda Magnitude Mc≤2.4, with epicentral and hypocentral location errors <2 km. These events concentrated mainly below Tres Virgenes volcanoes, and the geothermal explotation zone where there is a system NW-SE, N-S and W-E of extensional faults. Also we obtained focal mechanisms for 38 events using the Focmec, Hash, and FPFIT methods. The results show normal mechanisms which correlate with La Virgen, El Azufre, El Cimarron and Bonfil fault systems, whereas inverse and strike-slip solutions correlate with Las Viboras fault. Additionally, the Qc value was obtained for 118 events. This value was calculated using the Single Back Scattering model, taking the coda-waves train with window lengths of 5 sec. Seismograms were filtered at 4 frequency bands centered at 2, 4, 8 and 16 Hz respectively. The estimates of Qc vary from 62 at 2 Hz, up to 220 at 16 Hz. The frequency-Qc relationship obtained is Qc=40±2f(0.62±0.02), representing the average attenuation characteristics of seismic waves at Tres Virgenes volcanic and geothermal field. This value correlated with those observed at other geothermal and volcanic fields.

  12. Adapting Industry Multiple Attenuation Techniques to Crustal-Scale Marine Seismic Surveys

    NASA Astrophysics Data System (ADS)

    Gunther, R. H.; Levin, S. A.; Taylor, B. L.; Klemperer, S. L.; Goodliffe, A. M.; Oakley, A. J.; Taylor, B.

    2004-12-01

    Academic marine seismic surveys often focus on crustal targets situated in areas with deep water and rough topography. Thinly-sedimented seafloor creates strong and late-arriving water-column reverberations, often termed multiples, that can completely obscure deeper primary reflections. In a 2002 survey of the Mariana back-arc, arc, and fore-arc regions, large topographic variations produced strong multiples which were not significantly attenuated by stacking or migration. Using swath bathymetry, collected by the onboard multi-beam sonar system, we adapt industry multiple attenuation tools to extract useable data from below the water-bottom multiple. Standard approaches to multiple removal either take advantage of differences in move-out velocities between primary and multiple arrivals in order to filter out multiples or attempt to model multiples so that they can be adaptively subtracted from the data. Until recently, most modeling tools were restricted to 2D but still performed effectively against the well-behaved multiples often encountered in commercially important areas. But these algorithms have limited effectiveness against multiples generated from 3D structures such as salt domes, so the petroleum industry has recently made a strong push for 3D algorithms. In academic surveys, out-of-plane effects are all-too-often too large for successful application of 2D models, but due to the large regions of interest and budget constraints, 3D surveys are typically out of reach. Surface-Related Multiple Elimination (SRME) is a powerful approach that predicts multiples that reflect at least once off the free surface and can model any multiples that bounce off the surface along the source-receiver line. Developed from 1D theory laid down in the late `70s at Stanford University and extended to 2D in the `80s by Delft University, it has become widely used in commercial hydrocarbon exploration. The version of SRME we adapt to the Marianas survey convolves field shot gathers

  13. 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

  14. Assessing the deep drilling potential of Lago de Tota, Colombia, with a seismic survey

    NASA Astrophysics Data System (ADS)

    Bird, B. W.; Wattrus, N. J.; Fonseca, H.; Velasco, F.; Escobar, J.

    2015-12-01

    Reconciling orbital-scale patterns of inter-hemispheric South American climate during the Quaternary requires continuous, high-resolution paleoclimate records that span multiple glacial cycles from both hemispheres. Southern Andean Quaternary climates are represented by multi-proxy results from Lake Titicaca (Peru-Bolivia) spanning the last 400 ka and by pending results from the Lago Junin Drilling Project (Peru). Although Northern Andean sediment records spanning the last few million years have been retrieved from the Bogota and Fúquene Basins in the Eastern Cordillera of the Colombian Andes, climatic reconstructions based on these cores have thus far been limited to pollen-based investigations. When viewed together with the Southern Hemisphere results, these records suggest an anti-phased hemispheric climatic response during glacial cycles. In order to better assess orbital-scale climate responses, however, independent temperature and hydroclimate proxies from the Northern Hemisphere are needed in addition to vegetation histories. As part of this objective, an effort is underway to develop a paleoclimate record from Lago de Tota (3030 m asl), the largest lake in Colombia and the third largest lake in the Andes. One of 17 highland tectonic basins in Eastern Cordillera, Lago de Tota formed during Tertiary uplift that deformed pre-foreland megasequences, synrift and back-arc megasequences. The precise age and thickness of sediments in the Lago de Tota basin has not previously been established. Here, we present results from a recent single-channel seismic reflection survey collected with a small (5 cubic inch) air gun and high-resolution CHIRP sub-bottom data. With these data, we examine the depositional history and sequence stratigraphy of Lago de Tota and assess its potential as a deep drilling target.

  15. Personality Correlates of the Jenkins Activity Survey.

    ERIC Educational Resources Information Center

    Schiraldi, Glenn R.; Beck, Kenneth H.

    1988-01-01

    Administered Jenkins Activity Survey (JAS) and 11 other personality scales to over 700 college students to identify JAS personality correlates. Results revealed that, relative to subjects identified as Type B, those classified as Type A exhibited significantly greater status concern, less alexithymia, more misanthropy, and greater life…

  16. High resolution (chirp) survey in the Ionian sea (Italy, central Maditerranean): seismic evidence of mud diapirism and coral colonies

    NASA Astrophysics Data System (ADS)

    Fusi, N.; Savini, A.; Corselli, C.

    2003-04-01

    A CHIRP survey in the Ionian Sea between Calabria and Puglia (Italy) investigated: 1) the Calabrian margin, characterized by Eward dipping dip slip faults, which offset the sea bottom for a total throw of about 1200, and interested by diffuse mass-flow phenomena (slides and slumps); 2) the accretionary wedge, chiefly characterised by creep deposits; a flat plateau, identified in this area, is interpreted as the outcrop of coarse grained turbidites, coming from the steep Calabrian margin; 3) the Taranto Trench, affected by slumps in its upper part and by sedimentation of coarse grained sediments in the lower one; 4) the Apulian foreland, which rises from the Taranto trench through some appeninic (NNW-SSE) dip slip faults, with a total throw of about 1500 m; some anticlines, probably formed by Neogene-Pleistocene sediments and partly eroded, are interpreted on the basis of other seismic data (Doglioni et al., 1999; Merlini et al., 2000) as a local compression in a general extensive context. The identified echo characters have been compared with those described by Lee et al. (2002) and, on the basis of cores collected on some particular sites, they have been related to different kinds of sediments. In particular two echo characters have an interesting interpretation: 1) On the Apulian plateau we found a widespread presence of mounds, up to 50 m high, occurring as isolated mounds in the deepest zones (1600-800 m) and in groups in the shallower ones (800-600 m); they have been interpreted as coral mounds, in according to a recent discovery of living deep water coral colonies in this zone (Tursi A., Mastrototaro F., in press) and on the basis of their acoustic and morphological characters; in fact, due to high porosity and high water content, reef structures represent a poor seismic reflectors, appearing thus transparent (Hovland and Thomsen, 1997). Those coral mounds could be related to the intense fracturation of this area as a main via for fluid flow uprising. 2) Some

  17. The effect of deformation after backarc spreading between the rear arc and current volcanic front in Shikoku Basin obtained by seismic reflection survey

    NASA Astrophysics Data System (ADS)

    Yamashita, M.; Takahashi, N.; Nakanishi, A.; Kodaira, S.; Tamura, Y.

    2012-12-01

    Detailed crustal structure information of a back-arc basin must be obtained to elucidate the mechanism of its opening. Especially, the Shikoku Basin, which occupies the northern part of the Philippine Sea Plate between the Kyushu-Palau Ridge and the Izu-Bonin (Ogasawara) Arc, is an important area to understand the evolution of the back-arc basins as a part of the growth process of the Philippine Sea. Especially, the crustal structure oft the east side of Shikoku Basin is complicated by colliding to the Izu Peninsula Japan Agency for Marine-Earth Science and Technology has been carried out many multi-channel seismic reflection surveys since 2004 in Izu-Bonin region. Kodaira et al. (2008) reported the results of a refraction seismic survey along a north-south profile within paleoarc in the rear arc (i.e., the Nishi-shichito ridge) about 150 km west of current volcanic front. According to their results, the variation relationship of crustal thickness between the rear arc and volcanic front is suggested the evidence of rifting from current volcanic arc. There is the en-echelon arrangement is located in the eastern side of Shikoku Basin from current arc to rear arc, and it is known to activate after ceased spreading at 15 Ma (Okino et al., 1994) of Shikoku Basin by geologic sampling of Ishizuka et al. (2003). Our MCS results are also recognized the recent lateral fault zone is located in east side of Shikoku Basin. We carried out high density grid multi-channel seismic reflection (MCS) survey using tuned airgun in order to obtain the relationship between the lateral faults and en-echelon arrangement in KR08-04 cruise. We identified the deformation of sediments in Shikoku Basin after activity of Kanbun seamount at 8 Ma in MCS profile. It is estimated to activate a part of the eastern side of Shikoku Basin after construction of en-echelon arrangement and termination of Shikoku Basin spreading. Based on analyses of magnetic and gravity anomalies, Yamazaki and Yuasa (1998

  18. 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

  19. Seismic texture and amplitude analysis of large scale fluid escape pipes using time lapses seismic surveys: examples from the Loyal Field (Scotland, UK)

    NASA Astrophysics Data System (ADS)

    Maestrelli, Daniele; Jihad, Ali; Iacopini, David; Bond, Clare

    2016-04-01

    Fluid escape pipes are key features of primary interest for the analysis of vertical fluid flow and secondary hydrocarbon migration in sedimentary basin. Identified worldwide (Løset et al., 2009), they acquired more and more importance as they represent critical pathways for supply of methane and potential structure for leakage into the storage reservoir (Cartwright & Santamarina, 2015). Therefore, understanding their genesis, internal characteristics and seismic expression, is of great significance for the exploration industry. Here we propose a detailed characterization of the internal seismic texture of some seal bypass system (e.g fluid escape pipes) from a 4D seismic survey (released by the BP) recently acquired in the Loyal Field. The seal by pass structure are characterized by big-scale fluid escape pipes affecting the Upper Paleogene/Neogene stratigraphic succession in the Loyal Field, Scotland (UK). The Loyal field, is located on the edge of the Faroe-Shetland Channel slope, about 130 km west of Shetland (Quadrants 204/205 of the UKCS) and has been recently re-appraised and re developed by a consortium led by BP. The 3D detailed mapping analysis of the full and partial stack survey (processed using amplitude preservation workflows) shows a complex system of fluid pipe structure rooted in the pre Lista formation and developed across the paleogene and Neogene Units. Geometrical analysis show that pipes got diameter varying between 100-300 m and a length of 500 m to 2 km. Most pipes seem to terminate abruptly at discrete subsurface horizons or in diffuse termination suggesting multiple overpressured events and lateral fluid migration (through Darcy flows) across the overburden units. The internal texture analysis of the large pipes, (across both the root and main conduit zones), using near, medium and far offset stack dataset (processed through an amplitude preserved PSTM workflow) shows a tendency of up-bending of reflection (rather than pulls up artefacts

  20. 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

  1. Reactivation of Stromboli's summit craters at the end of the 2007 effusive eruption detected by thermal surveys and seismicity

    NASA Astrophysics Data System (ADS)

    Marotta, E.; Calvari, S.; Cristaldi, A.; D'Auria, L.; Di Vito, M. A.; Moretti, R.; Peluso, R.; Spampinato, L.; Boschi, E.

    2015-11-01

    This work arises from the field observations made during the civil protection emergency period connected to the 2007 Stromboli eruption. We observed changes in the shallow feeding system of the volcano to which we give a volcanological interpretation and the relative implications. Here we describe the processes that occurred in the upper feeding system from the end of the 2007 effusive eruption on 3 April to the renewal of the strombolian explosive activity at the summit craters (30 June), interpreted using multidisciplinary data. We used thermal camera data collected both from helicopter and from a fixed station at 400 m to retrieve the evolving summit crater activity. These data, compared with seismic signals and published geochemical records, allowed us to detail the shifting of the degassing activity within the crater terrace from NE to SW, occurred between 15 and 25 April 2007 prior to the resumption of the strombolian activity. In particular, from mid-April, a gradual SW displacement in the maximum apparent temperatures was recorded at the vents within the summit craters, together with a change in the very long period location and confirmed by variations in geochemical indicators (CO2/SO2 plume ratios and CO2 fluxes) from literature. The shallow feeding system experienced a major readjustment after the end of the effusive activity, determining variations in the pressure leakage of the source, slowly deepening and shifting toward SW. All these data, together with the framework supplied by previous structural surveys, allowed us to propose that the compaction of debris accumulated in the uppermost conduit by inward crater collapses, occurred in early March, produced the observed anomalies. At Stromboli, major morphology changes, taking place in the following years, were anticipated by these small and apparently minor processes occurred in the upper feeding system. Other studies are relating similar changes to modifications of the eruptive activity also at other

  2. 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.

  3. Continuous seismic-reflection survey of the Great Salt Lake, Utah- east of Antelope and Fremont Islands

    USGS Publications Warehouse

    Lambert, P.M.; West, J.C.

    1989-01-01

    A continuous seismic-reflection survey of the Great Salt Lake, Utah, was conducted east of Fremont and Antelope Islands in 1984 by the U.S. Geological Survey in cooperation with the Utah Department of Natural Resources and produced data along approximately 80 miles of seismic lines. The survey was conducted to determine depth to consolidated rock, and definition and continuity of overlying basin fill under the lake. Interpretation of the data indicates the presence of faulted rock dipping away from Fremont and Antelope Islands. A north-south-trending consolidated-rock ridge is identified 200 ft below lake bottom, 275 miles east of Fremont Island. Shallow rock is also inferred 380 ft below lake bottom, near Hooper Hot Springs, and 520 ft below lake bottom approximately 4 miles east of the south end of Antelope Island. Interpretation of reflections from overlying basin fill indicates fine-grained, thinly-bedded deposits that become coarser with depth. Strong reflectors in the basin fill can be correlated with water-bearing strata penetrated by wells near the north end of Antelope Island and along the east shore of the lake. Many continuous, high-amplitude reflections can be identified in data from basin fill and may represent sedimentary sections or aquifer boundaries but cannot be defined because of a lack of subsurface control in the area. (USGS)

  4. 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

  5. Some possible correlations between electro magnetic emission and seismic activity during West Bohemia 2008 earthquake swarm

    NASA Astrophysics Data System (ADS)

    Kolář, Petr; R寎ek, Bohuslav; Jedlička, Petr; Horálek, Josef; Boušková, Alena; Hruška, František; Baše, Jiří; Chum, Jaroslav

    2010-05-01

    There are long lasting speculations about electro-magnetic phenomena (hereafter EME) connected with seismic activity. In the present contribution we study such relation in West Bohemia region (hereafter W.B.) during 2008 earthquake swarm. Seismic activity in W.B. region is the most important seismic phenomenon in Czech Republic. It is characterized by occurrence of seismic swarms (it was most recently confirmed by 2008 swarm, the strongest one for the last 3 decades. High activity lasted approximately from October 10 to November 5, more than 20.000 events (Ml > -0.5), about 100 events with Ml > 2.0, the strongest event with Ml=3.7). In addition to ongoing standard seismic measurement performed by WEBNET seismic network, we recorded experimentally also electro-magnetic emission (detected by an antenna and digitized, we observed in range cca 0.1-10 Hz with sampling 25 Hz, continuous registration practically in the epicentrum of the swarm). Analysis of the data showed, that in the region there is no direct link between EME signal and seismic events neither for individual events nor statistically. However statistical analysis indicates that it could be some increase of EME activity in time 60 to 30 minutes before an event on periods 17-14 minutes, some gap in EME activity approximately 2 hours after the event and a maximum 4 hours after the events (only events with Ml > 1.8 were considered in the analysis). We practically excluded possibility that the effect could be caused by particular timing of prevent(s) and/or after event(s) - i.e. there is no correlation between observed extremes in EME signal and swarm energy flux or standard seismic signal. Also global decrease of EME activity with the decay of the swarm activity was observed. However due to incomplete EME data and short time of observation these results must be understand rather as indication of possible correlation rather than reliable relation. Further EME observations in the region are intended.

  6. Seismic activity response as observed in mantled howlers (Alouatta palliata), Cuero y Salado Wildlife Refuge, Honduras.

    PubMed

    Snarr, Kymberley Anne

    2005-10-01

    This report documents the response of wild mantled howlers (Alouatta palliata) to coseismic activity (seismic activity at the time of an earthquake). During field work on the north coast of Honduras, data were collected on a habituated troop of mantled howlers as they responded to coseismic activity. The seismic event occurred on 13 February 2001 at 0822 hours local time with a magnitude of Richter scale 6.6, focus depth of approximately 15 km at a distance of 341 km from the epicentre to the field site, Cuero y Salado. At the field site, based upon Jeffreys and Bullen (1988), body waves, noted as P and S waves, arrived at 60 and 87 s, respectively, with surface waves arriving approximately 103 s post-origin time of the seismic event. While there are three reports on non-human primate response to coseismic activity in the literature, they report on captive non-human primates. This is the first documented response on a non-captive troop. In addition, this report compares the intensity measure encountered by a wild troop of howlers and one captive group of orangutans as set out by the Modified Mercalli Intensity scale. The Modified Mercalli measure of intensity is one of two standard measures of seismic activity and rates what a person sees and feels at their location (Wood and Neumann 1931; Richter 1958). Thus, arboreal nonhuman primates are found to respond to coseismic activity ranging from Level IV to Level VI as based upon the modified Mercalli intensity scale.

  7. Data report for seismic refraction surveys conducted from 1980 to 1982 in the Livermore Valley and the Santa Cruz Mountains, California

    USGS Publications Warehouse

    Williams, Angela J.; Brocher, Thomas M.; Mooney, Walter D.; Boken, Annette

    1999-01-01

    We provide documentation for two seismic refraction profiles acquired by the U.S. Geological Survey in the San Francisco Bay area between 1980 and 1982 in Livermore Valley and the Santa Cruz Mountains. We also include the waveforms and travel times from five aftershocks of the April 1980 Livermore earthquake that were recorded on temporary seismic stations and that have not been published. Although seismic refraction profiles from the 1980 Livermore study have been published, none of the other data for this experiment, including shot times and locations, receiver locations, data quality, and travel times, have been reported. Similarly, such data from the 1981 to 1982 seismic refraction survey in the Santa Cruz Mountains included here have not been published. The first-arrival travel times from these profiles are reported in the hope that they can be used for three-dimensional velocity models in the San Francisco Bay area, particularly for the Livermore Valley and Santa Cruz Mountains.

  8. 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

  9. New seismic study begins in Puerto Rico

    USGS Publications Warehouse

    Tarr, A.C.

    1974-01-01

    A new seismological project is now underway in Puerto Rico to provide information needed for accurate assessment of the island's seismic hazard. The project should also help to increase understanding of the tectonics and geologic evolution of the Caribbean region. The Puerto Rico Seismic Program is being conducted by the Geological Survey with support provided by the Puerto Rico Water Resources Authority, an agency responsible for generation and distribution of electric power throughout the Commonwealth. The Program will include the installation of a network of high quality seismograph stations to monitor seismic activity on and around Puerto Rico. These stations will be distributed across the island to record the seismicity as uniformly as possible. The detection and accurate location of small earthquakes, as well as moderate magnitude shocks, will aid in mapping active seismic zones and in compiling frequency of occurrence statistics which ultimately wil be useful in seismic risk-zoning of hte island. 

  10. 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.

  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, 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.

  13. Airgun inter-pulse noise field during a seismic survey in an Arctic ultra shallow marine environment.

    PubMed

    Guan, Shane; Vignola, Joseph; Judge, John; Turo, Diego

    2015-12-01

    Offshore oil and gas exploration using seismic airguns generates intense underwater pulses that could cause marine mammal hearing impairment and/or behavioral disturbances. However, few studies have investigated the resulting multipath propagation and reverberation from airgun pulses. This research uses continuous acoustic recordings collected in the Arctic during a low-level open-water shallow marine seismic survey, to measure noise levels between airgun pulses. Two methods were used to quantify noise levels during these inter-pulse intervals. The first, based on calculating the root-mean-square sound pressure level in various sub-intervals, is referred to as the increment computation method, and the second, which employs the Hilbert transform to calculate instantaneous acoustic amplitudes, is referred to as the Hilbert transform method. Analyses using both methods yield similar results, showing that the inter-pulse sound field exceeds ambient noise levels by as much as 9 dB during relatively quiet conditions. Inter-pulse noise levels are also related to the source distance, probably due to the higher reverberant conditions of the very shallow water environment. These methods can be used to quantify acoustic environment impacts from anthropogenic transient noises (e.g., seismic pulses, impact pile driving, and sonar pings) and to address potential acoustic masking affecting marine mammals. PMID:26723302

  14. Airgun inter-pulse noise field during a seismic survey in an Arctic ultra shallow marine environment.

    PubMed

    Guan, Shane; Vignola, Joseph; Judge, John; Turo, Diego

    2015-12-01

    Offshore oil and gas exploration using seismic airguns generates intense underwater pulses that could cause marine mammal hearing impairment and/or behavioral disturbances. However, few studies have investigated the resulting multipath propagation and reverberation from airgun pulses. This research uses continuous acoustic recordings collected in the Arctic during a low-level open-water shallow marine seismic survey, to measure noise levels between airgun pulses. Two methods were used to quantify noise levels during these inter-pulse intervals. The first, based on calculating the root-mean-square sound pressure level in various sub-intervals, is referred to as the increment computation method, and the second, which employs the Hilbert transform to calculate instantaneous acoustic amplitudes, is referred to as the Hilbert transform method. Analyses using both methods yield similar results, showing that the inter-pulse sound field exceeds ambient noise levels by as much as 9 dB during relatively quiet conditions. Inter-pulse noise levels are also related to the source distance, probably due to the higher reverberant conditions of the very shallow water environment. These methods can be used to quantify acoustic environment impacts from anthropogenic transient noises (e.g., seismic pulses, impact pile driving, and sonar pings) and to address potential acoustic masking affecting marine mammals.

  15. Seismic Evidence for Neogene and Active Shortening Offshore Lebanon (SHALIMAR Cruise)

    NASA Astrophysics Data System (ADS)

    Carton, H.; Singh, S. C.; Tapponnier, P.; Elias, A.; Briais, A.; Sursock, A.; Jomaa, R.; King, G. C.; Daeron, M.; Jacques, E.; Barrier, L.

    2007-12-01

    Lebanon is located on a 160 km long transpressional bend of the left-lateral Levant (Dead Sea) Fault. The main objective of the SHALIMAR (2003) marine survey was to characterize and map active deformation offshore Lebanon using a range of geophysical techniques, particularly seismic reflection profiling. The cruise results clearly establish the presence of submarine thrust faults - likely the source of one of the most devastating submarine historical earthquakes that happened along the Levantine shores - and clarify the structure of this part of the Levant margin. A submarine fold-belt, bounded by thrusts and lateral ramps and extending in places to at least 30 km from the shoreline, is interpreted as the foreland thrust system of the actively growing Mount Lebanon range. There is no large fault extending into the Levant Basin towards Cyprus, which indicates that thrusting only absorbs local transpression resulting from the Lebanese restraining bend. Both the Miocene and Plio-Quaternary sedimentary sequences are affected by shortening, with landward-dipping blind thrusts and associated growth strata. The presence of the Messinian evaporites creates complex deformation patterns, including normal faults due both to folding accommodation and gravity spreading, all well imaged in the seismic reflection profiles. Because the evaporite layer acts as a decollement level, deformation extends farther out seawards through a series of thrust imbricates or duplexes. Shortening is strongest between Beyrut and Batroun and decreases towards the south between Saida and Tyre. North of Tripoli, the passive margin is not affected by Neogene deformation, and is well preserved. We propose that, since the Miocene, the northward propagating Levant Fault interacted with margin structures inherited from the Mesozoic rifting phase, and was deviated away from the more rigid oceanic crust flooring the Levant basin, a process which led to the formation of the Lebanese restraining bend, and

  16. Seismic Evidence for Neogene and Active Shortening Offshore Lebanon (SHALIMAR Cruise)

    NASA Astrophysics Data System (ADS)

    Carton, H.; Singh, S. C.; Tapponnier, P.; Elias, A.; Briais, A.; Sursock, A.; Jomaa, R.; King, G. C.; Daeron, M.; Jacques, E.; Barrier, L.

    2004-12-01

    Lebanon is located on a 160 km long transpressional bend of the left-lateral Levant (Dead Sea) Fault. The main objective of the SHALIMAR (2003) marine survey was to characterize and map active deformation offshore Lebanon using a range of geophysical techniques, particularly seismic reflection profiling. The cruise results clearly establish the presence of submarine thrust faults - likely the source of one of the most devastating submarine historical earthquakes that happened along the Levantine shores - and clarify the structure of this part of the Levant margin. A submarine fold-belt, bounded by thrusts and lateral ramps and extending in places to at least 30 km from the shoreline, is interpreted as the foreland thrust system of the actively growing Mount Lebanon range. There is no large fault extending into the Levant Basin towards Cyprus, which indicates that thrusting only absorbs local transpression resulting from the Lebanese restraining bend. Both the Miocene and Plio-Quaternary sedimentary sequences are affected by shortening, with landward-dipping blind thrusts and associated growth strata. The presence of the Messinian evaporites creates complex deformation patterns, including normal faults due both to folding accommodation and gravity spreading, all well imaged in the seismic reflection profiles. Because the evaporite layer acts as a decollement level, deformation extends farther out seawards through a series of thrust imbricates or duplexes. Shortening is strongest between Beyrut and Batroun and decreases towards the south between Saida and Tyre. North of Tripoli, the passive margin is not affected by Neogene deformation, and is well preserved. We propose that, since the Miocene, the northward propagating Levant Fault interacted with margin structures inherited from the Mesozoic rifting phase, and was deviated away from the more rigid oceanic crust flooring the Levant basin, a process which led to the formation of the Lebanese restraining bend, and

  17. Seismic evidence for Neogene and active shortening offshore of Lebanon (Shalimar cruise)

    NASA Astrophysics Data System (ADS)

    Carton, H.; Singh, S. C.; Tapponnier, P.; Elias, A.; Briais, A.; Sursock, A.; Jomaa, R.; King, G. C. P.; DaëRon, M.; Jacques, E.; Barrier, L.

    2009-07-01

    Lebanon, located on a 160-km-long transpressional bend of the left-lateral Levant (Dead Sea) fault system (LFS), has been the site of infrequent but large earthquakes, including one submarine, tsunamigenic event. The main objective of the Shalimar marine survey was to characterize and map active deformation offshore of Lebanon using a range of geophysical techniques, particularly seismic reflection profiling. The cruise results clearly establish the presence of young submarine thrust faults and folds and clarify the structure of this part of the Levant margin. A submarine fold belt, bounded by thrusts and lateral ramps and extending up to 30 km from the shoreline, is interpreted as the foreland thrust system of the actively growing Mount Lebanon range. There is no large fault extending into the Levant basin toward Cyprus, which indicates that thrusting only absorbs local transpression resulting from the Lebanese restraining bend. Both the Miocene and Plio-Quaternary sedimentary sequences are affected by shortening, with landward dipping blind thrusts and associated growth strata. The presence of the Messinian evaporites creates complex deformation patterns, including normal faults due both to folding accommodation and to gravity spreading, all well imaged in the seismic reflection profiles. Because the evaporite layer acts as a décollement level, shortening extends farther out seaward through a series of thrust imbricates or duplexes. The strongest shortening, observed between Beirut and Batroun, decreases toward the south between Saida and Tyre. North of Tripoli, the passive margin is not affected by Neogene deformation and is well preserved. We propose that since the Miocene, the northward propagating LFS interacted with margin structures inherited from the Mesozoic rifting phase and was deviated along the more rigid oceanic crust flooring the Levant basin, a process which led to the formation of the Lebanese restraining bend of the LFS and consequently to the

  18. Integrated Seismic Survey for Detecting Landslide Effects on High Speed Rail Line at Istanbul-Turkey

    NASA Astrophysics Data System (ADS)

    Grit, Mert; Kanli, Ali Ismet

    2016-02-01

    In this study, Multichannel Analysis of Surface Waves Method (MASW), seismic refraction tomography and seismic reflection methods are used together at Silivri district in Istanbul - a district with a landslide problem because of the high speed rail line project crossing through the area. The landslide structure, border and depth of the slip plane are investigated and correlated within the local geology. According to the obtained 2D seismic sections, the landslide occurs through the East-West direction in the study area and the landslide slip plane with its border are clearly obtained under the subsurface. The results prove that the study area is suitable enough for the landslide development and this evolution also affects the high speed rail line project.

  19. Contributions to a shallow aquifer study by reprocessed seismic sections from petroleum exploration surveys, eastern Abu Dhabi, United Arab Emirates

    USGS Publications Warehouse

    Woodward, D.

    1994-01-01

    The US Geological Survey, in cooperation with the National Drilling Company of Abu Dhabi, is conducting a 4-year study of the fresh and slightly saline groundwater resources of the eastern Abu Dhabi Emirate. Most of this water occurs in a shallow aquifer, generally less than 150 m deep, in the Al Ain area. A critical part of the Al Ain area coincides with a former petroleum concession area where about 2780 km of vibroseis data were collected along 94 seismic lines during 1981-1983. Field methods, acquistion parameters, and section processing were originally designed to enhance reflections expected at depths ranging from 5000 to 6000 m, and subsurface features directly associated with the shallow aquifer system were deleted from the original seismic sections. The original field tapes from the vibroseis survey were reprocessed in an attempt to extract shallow subsurface information (depths less than 550 m) for investigating the shallow aquifer. A unique sequence of reproccessing parameters was established after reviewing the results from many experimental tests. Many enhancements to the resolution of shallow seismic reflections resulted from: (1) application of a 20-Hz, low-cut filter; (2) recomputation of static corrections to a datum nearer the land surface; (3) intensive velocity analyses; and (4) near-trace muting analyses. The number, resolution, and lateral continuity of shallow reflections were greatly enhanced on the reprocessed sections, as was the delineation of shallow, major faults. Reflections on a synthetic seismogram, created from a borehole drilled to a depth of 786 m on seismic line IQS-11, matcheddprecisely with shallow reflections on the reprocessed section. The 33 reprocessed sections were instrumental in preparing a map showing the major structural features that affect the shallow aquifer system. Analysis of the map provides a better understanding of the effect of these shallow features on the regional occurrence, movement, and quality of

  20. Firn air-content of Larsen C Ice Shelf, Antarctic Peninsula, from seismic velocities, borehole surveys and firn modelling

    NASA Astrophysics Data System (ADS)

    Kulessa, Bernd; Brisbourne, Alex; Booth, Adam; Kuipers Munneke, Peter; Bevan, Suzanne; Luckman, Adrian; Hubbard, Bryn; Gourmelen, Noel; Palmer, Steve; Holland, Paul; Ashmore, David; Shepherd, Andrew

    2016-04-01

    The rising surface temperature of Antarctic Peninsula ice shelves is strongly implicated in ice shelf disintegration, by exacerbating the compaction of firn layers. Firn compaction is expected to warm the ice column and, given sufficiently wet and compacted layers, to allow meltwater to penetrate into surface crevasses and thus enhance hydrofracture potential. Integrating seismic refraction surveys with borehole neutron and firn core density logging, we reveal vertical and horizontal changes in firn properties across Larsen C Ice Shelf. Patterns of firn air-content derived from seismic surveys are broadly similar to those estimated previously from airborne radar and satellite data. Specifically, these estimates show greater firn compaction in the north and landward inlets compared to the south, although spatial gradients in seismic-derived air-contents are less pronounced than those previously inferred. Firn thickness is less than 10 m in the extreme northwest of Larsen C, in Cabinet Inlet, yet exceeds 40 m in the southeast, suggesting that the inlet is a focus of firn compaction; indeed, buried layers of massive refrozen ice were observed in 200 MHz GPR data in Cabinet and Whirlwind Inlets during a field campaign in the 2014-15 austral summer. Depth profiles of firn density provide a reasonable fit with those derived from closely-located firn cores and neutron probe data. Our model of firn structure is driven by RACMO and includes a 'bucket'-type hydrological implementation, and simulates the depth-density profiles in the inlets well. Discrepancies between measured and modelled depth-density profiles become progressively greater towards the ice-shelf front. RACMO incorrectly simulates the particular leeward (sea-ice-influenced) microclimate of the shallow boundary layer, leading to excess melt and/or lack of snowfall. The spatial sampling density of our seismic observations will be augmented following a further field campaign in the 2016-17 austral summer

  1. Local Ambient Seismic Noise Survey in Dixie Valley, NV for Engineered Geothermal System Favorability Assessment

    NASA Astrophysics Data System (ADS)

    Tibuleac, I. M.; Iovenitti, J. L.; von Seggern, D. H.; Sainsbury, J.

    2013-12-01

    The primary objective of this study is to develop and test the seismic component of a calibrated exploration method that integrated geological, geophysical, and geochemical data to identify potential drilling targets for Engineered Geothermal Systems (EGS). In exploring for EGS sites, the selection criteria identified by the AltaRock Energy, Inc. (AltaRock) and University of Nevada, Reno teams are, in order of importance, (1) temperature greater than 200C at 1.5 km depth, (2) rock type at the depth of interest (porous rocks at 1-3 km); and (3) favorable stress regime (tensional environment). To improve spatial resolution, a dense seismic array (21 three-component, broadband sensors, with an overall array aperture of 45km) was installed in two deployments in Dixie Valley, NV, each deployment having a three-month duration Ambient seismic noise and signal were used to retrieve inter-station and same-station Green's Functions (GFs), to be used for subsurface imaging. We used ambient seismic noise interferometry to extract GFs from crosscorrelation of continuous records. An innovative aspect of the seismic work was estimating the receiver functions beneath the stations using noise auto-correlation which was used to image the substructure. We report results of applying the technique to estimate a P/S velocity model from the GF surface wave components and from the GF body-wave reflection component, retrieved from ambient noise and signal cross-correlation and auto-correlation beams. We interpret our results in terms of temperature, pressure and rock composition. The estimated seismic velocity model capability to infer temperature is statistically assessed, in combination with other geophysical technique results.

  2. Structure of the deep oceanic lithosphere in the Northwestern Pacific ocean basin derived from active-source seismic data

    NASA Astrophysics Data System (ADS)

    Ohira, A.; Kodaira, S.; Nakamura, Y.; Fujie, G.; Arai, R.; Miura, S.

    2015-12-01

    Many seismological studies have detected the sharp seismic discontinuities in the upper mantle, some of which are interpreted the lithosphere-asthenosphere boundary (LAB). However there are few data at the old Pacific plate, in particular at ocean basin, which is critical information for understanding nature of the oceanic LAB. In 2014 we conducted an active-source refraction/reflection survey along a 1130-km-long line in southeast of the Shatsky Rise. Five ocean bottom seismometers (OBSs) were deployed and recovered by R/V Kairei of JAMSTEC. We used an airgun array with a total volume of 7,800 cubic inches with firing at intervals of 200 m. Multi-channel seismic reflection (MCS) data were also collected with a 444-channel, 6,000-m-long streamer cable. In OBS records the apparent velocity of the refraction waves from the uppermost mantle was high (< 8.6 km/sec), and considered to be caused by preferred orientation of olivine (e.g., Kodaira et al., 2014). Another remarkable feature is wide-angle reflection waves from the deep lithosphere at large (150-500 km) offsets. We applied the traveltime mapping method (Fujie et al., 2006), forward analysis (Zelt and Smith, 1992) and the amplitude modeling (Larsen and Grieger, 1998) to the OBS data. The results show that deep mantle reflectors exist at the depths from 35 to 60 km, and one possible explanation is that these reflectors correspond to patched low velocity zones around the base of the lithosphere. On MCS sections the clear and sharp Moho was imaged only at the southwestern end of the profile, but Moho was ambiguous or even not imaged in the most part of the profile. Since our seismic line covers the oceanic lithosphere with different ages that correspond to different stages of the Shatsky activity, the Moho appearance may reflect the variation of the Shatsky activity.

  3. Seismic monitoring of geomorphic processes

    NASA Astrophysics Data System (ADS)

    Burtin, A.; Hovius, N.; Turowski, J. M.

    2014-12-01

    In seismology, the signal is usually analysed for earthquake data, but these represent less than 1% of continuous recording. The remaining data are considered as seismic noise and were for a long time ignored. Over the past decades, the analysis of seismic noise has constantly increased in popularity, and this has led to develop new approaches and applications in geophysics. The study of continuous seismic records is now open to other disciplines, like geomorphology. The motion of mass at the Earth's surface generates seismic waves that are recorded by nearby seismometers and can be used to monitor its transfer through the landscape. Surface processes vary in nature, mechanism, magnitude and space and time, and this variability can be observed in the seismic signals. This contribution aims to give an overview of the development and current opportunities for the seismic monitoring of geomorphic processes. We first describe the common principles of seismic signal monitoring and introduce time-frequency analysis for the purpose of identification and differentiation of surface processes. Second, we present techniques to detect, locate and quantify geomorphic events. Third, we review the diverse layout of seismic arrays and highlight their advantages and limitations for specific processes, like slope or channel activity. Finally, we illustrate all these characteristics with the analysis of seismic data acquired in a small debris-flow catchment where geomorphic events show interactions and feedbacks. Further developments must aim to fully understand the richness of the continuous seismic signals, to better quantify the geomorphic activity and improve the performance of warning systems. Seismic monitoring may ultimately allow the continuous survey of erosion and transfer of sediments in the landscape on the scales of external forcing.

  4. National Archive of Marine Seismic Surveys (NAMSS): A USGS-Boem Partnership to Provide Free and Easy Access to Previously Proprietary Seismic Reflection Data on the U.S. Outer Continental Shelf

    NASA Astrophysics Data System (ADS)

    Triezenberg, P. J.; Hart, P. E.; Childs, J. R.

    2014-12-01

    The National Archive of Marine Seismic Surveys (NAMSS) was established by the USGS in 2004 in an effort to rescue marine seismic reflection profile data acquired largely by the oil exploration industry throughout the US outer continental shelf (OCS). It features a Web interface for easy on-line geographic search and download. The commercial value of these data had decreased significantly because of drilling moratoria and newer acquisition technology, and large quantities were at risk of disposal. But, the data still had tremendous value for scientific research and education purposes, and an effort was undertaken to ensure that the data were preserved and publicly available. More recently, the USGS and Bureau of Ocean Energy Management (BOEM) have developed a partnership to make similarly available a much larger quantity of 2D and 3D seismic data acquired by the U.S. government for assessment of resources in the OCS. Under Federal regulation, BOEM is required to publicly release all processed geophysical data, including seismic profiles, acquired under an exploration permit, purchased and retained by BOEM, no sooner than 25 years after issuance of the permit. Data acquired prior to 1989 are now eligible for release. Currently these data are distributed on CD or DVD, but data discovery can be tedious. Inclusion of these data within NAMSS vastly increases the amount of seismic data available for research purposes. A new NAMSS geographical interface provides easy and intuitive access to the data library. The interface utilizes OpenLayers, Mapnik, and the Django web framework. In addition, metadata capabilities have been greatly increased using a PostgresSQL/PostGIS database incorporating a community-developed ISO-compliant XML template. The NAMSS database currently contains 452 2D seismic surveys comprising 1,645,956 line km and nine 3D seismic surveys covering 9,385 square km. The 2D data holdings consist of stack, migrated and depth sections, most in SEG-Y format.

  5. 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.

  6. 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

  7. 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

  8. Structure of the Palomares margin from preliminary results of the TOPOMED-GASSIS seismic survey (Algero-Balearic basin, Western Mediterranean)

    NASA Astrophysics Data System (ADS)

    Giaconia, F.; Guzman Vendrell, M.; Booth-Rea, G.; Ranero, C. R.; Grácia, E.; Lo Iacono, C.

    2012-04-01

    We present two deep seismic reflection lines acquired during the TOPOMED-GASSIS seismic survey across the Palomares margin at the northwestern side of the Algero-Balearic basin. Simultaneously 3.5 kHz multi parametric echo-sounder profiles and bathymetric data were acquired, in order to obtain information of the most recent sedimentary/tectonic records, to relate tectonic structure with seafloor features and find out a possible tectonic control on them. The deep seismic reflection and the 3.5 kHz multi parametric echo-sounder profiles evidence anticlines and synclines affecting the Quaternary sediments. The southeastern limbs of the anticlines are cut by reverse faults suggesting a fault propagation origin for the folds. The recent to present character of these structures is confirmed by the congruence between structural and bathymetric highs and lows. Indeed, the submarine channels that cut across the margin are deflected by the folds flowing parallel to the major synclines, although cutting and incising into one of the anticlines. The folds have a N40-50°E orientation oblique to the Palomares active N20°E sinistral strike-slip fault zone. The data obtained from the TOPOMED-GASSIS seismic survey highlight the presence of contractive structures along the Palomares margin oriented perpendicular to the present NW-SE shortening stress field and according with the present GPS geodetic displacements. This preliminary result depicts a contractive Palomares margin where NW-SE shortening is accommodated by Quaternary NE-SW folds and thrusts. In the coastline and on land the shortening is also accommodated by reverse faults that cut both limbs of the Sierra Cabrera anticline. These faults and folds accommodate the sinistral displacement of the more northerly striking Palomares fault zone. Thus, the Palomares fault zone probably terminates close to the coast line to the south of the Vera basin by merging into these more northeasterly oriented structures. These folds

  9. 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

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. Comparison of microbial and sorbed soil gas surgace geochemical techniques with seismic surveys from the Southern Altiplano, Bolivia

    SciTech Connect

    Aranibar, O.R.; Tucker, J.D.; Hiltzman, D.C.

    1995-12-31

    Yacimientos Petroliferos Fiscales Bolivianos (YPFB) undertook a large seismic evaluation in the southern Altiplano, Bolivia in 1994. As an additional layer of information, sorbed soil gas and Microbial Oil Survey Technique (MOST) geochemical surveys were conducted to evaluate the hydrocarbon microseepage potential. The Wara Sara Prospect had 387 sorbed soil gas samples, collected from one meter depth, and 539 shallow soil microbial samples, collected from 15 to 20 centimeter depth. The sorbed soil gas samples were collected every 500 meters and microbial samples every 250 meters along geochemical traverses spaced 1 km apart. The presence of anmalous hydrocarbon microseepage is indicated by (1) a single hydrocarbon source identified by gas crossplots, (2) the high gas values with a broad range, (3) the high overall gas average, (4) the clusters of elevated samples, and (5) the right hand skewed data distributions.

  17. A groundwater model for the Spruce Hole aquifer, Durham, NH, based on a detailed seismic refraction survey

    SciTech Connect

    Kerwin, R.A. . Dept. of Earth Sciences)

    1993-03-01

    The town of Durham and the University of New Hampshire are interested in using the Spruce Hole aquifer as a municipal pumping well site. The goals of this project were to determine the approximate thickness and areal extent of the aquifer, to determine the hydrologic characteristics and capabilities of the aquifer (groundwater flow directions and transmissivities), and to simulate the effect that pumping of the aquifer may have on the delicate ecosystem of Spruce Hole bog. The Spruce Hole aquifer is a drift deposit composed of glacial till and stratified sand and gravel and is underlain by metasedimentary bedrock. A kettlehole bog with a unique ecosystem with rare plants and insects is located near the center of the deposit. The author conducted a 65 site seismic refraction survey of the Spruce Hole aquifer to estimate water table elevation, bedrock depth, and saturated thickness, as well as till elevations (seismic velocities between 1.9 km/s and 2.6 km/s) at many of the locations. One-dimensional (cross section) and two-dimensional (map view) transmissivity based finite-difference groundwater models were developed to simulate the groundwater flow of the system and to determine transmissivity values for the stratified drift. An average transmissivity for the aquifer at each grid point in the model was determined through data from wells, the seismic refraction survey, and by matching estimated water table values with those calculated by the model. This model has produced simulations that are plausible representations of the ground-water system of the aquifer. A better understanding of kettlehole bog/groundwater system can be gotten from this work.

  18. A critique of the UK's JNCC seismic survey guidelines for minimising acoustic disturbance to marine mammals: best practise?

    PubMed

    Parsons, E C M; Dolman, Sarah J; Jasny, Michael; Rose, Naomi A; Simmonds, Mark P; Wright, Andrew J

    2009-05-01

    The United Kingdom's statutory conservation agency, the Joint Nature Conservation Committee (JNCC), developed guidelines in 1995 to minimise acoustic disturbance of marine mammals by oil and gas industry seismic surveys. These were the first national guidelines to be developed and have subsequently become the standard, or basis, of international mitigation measures for noise pollution during seismic surveys. However, relatively few aspects of these measures have a firm scientific basis or proven efficacy. Existing guidelines do not offer adequate protection to marine mammals, given the complex propagation of airgun pulses; the difficulty of monitoring in particular the smaller, cryptic, and/or deep-diving species, such as beaked whales and porpoises; limitations in monitoring requirements; lack of baseline data; and other biological and acoustical complications or unknowns. Current guidelines offer a 'common sense' approach to noise mitigation, but in light of recent research and ongoing concerns, they should be updated, with broader measures needed to ensure adequate species protection and to address data gaps.

  19. 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

  20. The preglacial sediment record of Lake Ladoga, Russia - first results from a seismic survey and sediment coring in 2013

    NASA Astrophysics Data System (ADS)

    Melles, Martin; Krastel, Sebastian; Fedorov, Grigory; Subetto, Dmitry A.; Savelieva, Larisa A.; Andreev, Andrej; Wagner, Bernd

    2014-05-01

    The new German-Russian project PLOT (Paleolimnological Transect) aims at investigating the Late Quaternary climatic and environmental history along a more than 6000 km long longitudinal transect crossing northern Eurasia. Special emphasis is put on the preglacial history. For this purpose shallow and deep seismic surveys shall be carried out on five lakes, which potentially host preglacial sediment records, followed by sediment coring based on the results of the seismic campaigns. The well-studied Lake El'gygytgyn represents the eastern-most location of the transect and acts as reference site. Within the scope of a pilot phase for the PLOT project, funded by the German Federal Ministry of Education and Research, we were able to investigate Lake Ladoga, which is located close to St. Petersburg at the western end of the transect. Lake Ladoga is the largest lake in Europe, covering an area of almost 18.000 km2. The modern sedimentation as well as the late glacial and Holocene history of the lake were already studied in detail over the past decades. The older, preglacial lake history, however, is only rudimentary known from a core transect drilled in the southern lake in the 1930th. The cores of up to about 60 m length were only briefly described and are not existing any more. The results from these cores, known from unpublished reports only, suggest the existence of marine sediments of presumably Eemian age, representing a time when Lake Lagoga was part of a precursor of the Baltic Sea, which had a connection via Ladoga and Onega Lakes to the White Sea and further to the Arctic Ocean. In late August/early September 2013 we carried out a seismic survey on Lake Ladoga using a Mini-GI-Gun and a 32-channel seismic streamer. In total, 1500 km of seismic profiles were measured, covering most parts of the lake. The seismic lines typically show acoustically well stratified Holocene muds overlaying rather transparent postglacial varves. These sediment successions can reach

  1. 78 FR 11821 - Takes of Marine Mammals Incidental to Specified Activities; Low-Energy Marine Geophysical Survey...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-20

    ... Seismic Survey by the U.S. Geological Survey in the Deepwater Gulf of Mexico, April-May 2013'' (EA). USGS... the U.S. Geological Survey in the Northwestern Gulf of Mexico, April-May 2013,'', prepared by LGL Ltd... conducting a low-energy marine seismic survey within the U.S. Exclusive Economic Zone in the deep water...

  2. 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.

  3. 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.

  4. 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.

  5. Application of disturbance theory to assess impacts associated with a three-dimensional seismic survey in a freshwater marsh in southwest Louisiana

    NASA Astrophysics Data System (ADS)

    Bass, Aaron Stuard

    This study examined various practical and theoretical aspects of disturbance in a coastal wetland marsh in southern Louisiana. A literature review approached disturbance ecology from both practical and theoretical perspectives and assessed its applicability to developing broad predictive models. However, specific knowledge of environmental variables, competitive relationships, and the interactive effects of multiple disturbances are required for meaningful usage of these models. The Lacassine National Wildlife Refuge (LNWR) proved to be an ideal laboratory to test various aspects of ecological disturbance theory. I found that the primary disturbances affecting the LNWR have been hurricanes, droughts, water-level manipulations, prescribed burning, oil and gas recovery activities, grazing by Myocastor coypus (nutria), and managed cattle grazing. The 1990's application of three-dimensional (3-D) seismic technology used in the oil and gas recovery business challenged landowners, government regulators, and industry to develop ways to recover these resources without damaging surface features. I developed a conservative estimate that an area exceeding 2.5 times the area of Louisiana's coastal wetlands was covered by overlapping seismic surveys in southern Louisiana from 1997 through 2002, equal to 22.5 km2/year. I provided a general overview of 3-D seismic survey programs, potential adverse impacts, and management and restoration strategies. I also conducted a field study at the LNWR on vegetation in control and treatment transects before, and for two years after, a 3-D survey. I found vegetative cover and the amount of dead plant biomass were significantly lower in treatment plots, but live biomass was not different in treatment and control plots. Species richness was higher in treatment plots compared to control plots, but the live biomass and cover of the dominant species ( Panicum hemitomon) was lower. The live biomass and cover of Eleocharis spp., a colonizing

  6. 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

  7. 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

    , Italian Institute of Geophysics and Vulcanology (INGV) in order to transfer information to the population to enhance self-protection capability and decrease its state of worry ("what to do" in case of an earthquake); 3. review of local plans of emergency, where available, using ad hoc inspection forms to collect data for verifying and updating the emergency plan content and requirements. Specifically, in order to prepare seismic scenarios of building damage and effects on population for emergency planning and civil defense drills to be organized, two more activities have been carried out: 4. collection of current vulnerability data on the building stock and the strategic infrastructures located in the area; 5. accurate survey of data on post earthquake retrofitting and microzonation actions carried out after the 1998 Pollino earthquake that struck the same involved villages. In some cases, as a consequence of the position of the involved area, the activities were carried out also in collaboration with Calabria Region authorities. Several points have arisen in carrying out the activities, mostly due to the interaction between risk governance and risk perception in the pre-event emergency management. At the abstract submission date the seismic sequence, and thus the activities here described, are still ongoing. Therefore, analysis and discussion of pro's and con's of the actions taken are currently in progress on a week-by-week basis.

  8. 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.

  9. New methods for engineering site characterization using reflection and surface wave seismic survey

    NASA Astrophysics Data System (ADS)

    Chaiprakaikeow, Susit

    This study presents two new seismic testing methods for engineering application, a new shallow seismic reflection method and Time Filtered Analysis of Surface Waves (TFASW). Both methods are described in this dissertation. The new shallow seismic reflection was developed to measure reflection at a single point using two to four receivers, assuming homogeneous, horizontal layering. It uses one or more shakers driven by a swept sine function as a source, and the cross-correlation technique to identify wave arrivals. The phase difference between the source forcing function and the ground motion due to the dynamic response of the shaker-ground interface was corrected by using a reference geophone. Attenuated high frequency energy was also recovered using the whitening in frequency domain. The new shallow seismic reflection testing was performed at the crest of Porcupine Dam in Paradise, Utah. The testing used two horizontal Vibroseis sources and four receivers for spacings between 6 and 300 ft. Unfortunately, the results showed no clear evidence of the reflectors despite correction of the magnitude and phase of the signals. However, an improvement in the shape of the cross-correlations was noticed after the corrections. The results showed distinct primary lobes in the corrected cross-correlated signals up to 150 ft offset. More consistent maximum peaks were observed in the corrected waveforms. TFASW is a new surface (Rayleigh) wave method to determine the shear wave velocity profile at a site. It is a time domain method as opposed to the Spectral Analysis of Surface Waves (SASW) method, which is a frequency domain method. This method uses digital filtering to optimize bandwidth used to determine the dispersion curve. Results from testings at three different sites in Utah indicated good agreement with the dispersion curves measured using both TFASW and SASW methods. The advantage of TFASW method is that the dispersion curves had less scatter at long wavelengths as a

  10. Mapping Subsea Permafrost, Relict Methane Hydrate, and Gas Migration: New Cross-Shelf Multichannel Seismic Surveys on the Central US Beaufort Shelf

    NASA Astrophysics Data System (ADS)

    Ruppel, C. D.; Hart, P. E.; Moore, E.; Worley, C.; Brothers, L.

    2012-12-01

    In August 2012, the USGS Gas Hydrates Project, with support from DOE's Methane Hydrates R&D Program, conducted the first research-oriented multichannel seismic survey in 35 years across the Alaskan Beaufort Sea continental shelf. Our Central Beaufort margin study area stretches from Camden Bay on the west to Harrison Bay on the east and lies offshore some of the North Slope's most important petroleum systems. The new MCS data were collected in the eastern part of the Alaskan passive margin terrane, near the transition zone to the compressional Canning Mackenzie Deformed Margin described by Houseknecht and Bird. The Central Beaufort shelf was mostly exposed subaerially during Late Pleistocene time, leading to the formation of continuous permafrost and associated gas hydrates at depths greater than ~225 m. As Holocene sea level rise inundated the present-day shelf, the now-subsea permafrost began to thaw and associated gas hydrates would have begun to dissociate. The new surveys constitute the shelf component of site survey activities for Integrated Ocean Drilling pre-proposal 797, which outlines a multiplatform drilling program at 9 sites from the innermost shelf to the upper continental slope of the Alaskan Beaufort margin. The proposed drilling program will elucidate Late Pleistocene to contemporary climate history by accessing sediments currently or formerly hosting subsea permafrost and permafrost-associated methane hydrates on the shelf and sediments in which gas hydrate dynamics are driven by warming of impinging intermediate waters on the upper continental slope. Using a 24-channel digital streamer and a 2 kJ sparker source, the new MCS surveys provided up to several hundred meters of subseafloor penetration and were complemented by 4-24 kHz Chirp surveys for the shallowmost section, high frequency water column imaging for gas plumes, and Swathplus bathymetric mapping at water depths less than 60 to 80 m. The new MCS data, which in part reoccupy 30-year

  11. 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

  12. Statistical study of quasi-static electric field anomalies in the upper ionosphere related to seismic activity above different tectonic structures of the Earth

    NASA Astrophysics Data System (ADS)

    Gousheva, Mariyana; Danov, Dimitar; Hristov, Plamen; Matova, Margarita

    2010-05-01

    The satellite observation of vertical quasi- static electric fields allows the study of upper ionospheric anomalies that could be related to the seismic activity of different Earth tectonic structures. The quasi-static electric fields were recorded by IESP-1 instrument installed on the INTERCOSMOS-BULGARIA-1300 satellite. Forty eight orbits situated over Europe, Atlantic, North America, Central America, South America, Africa, Indian ocean, Asia, North Pacific, South Pacific, Australia, Arctic and Antarctic were chosen for the research when they pass above sources of 114 light, moderate or strong earthquakes. The time period of observation spanned between 17 August and 8 December 1981. The seismic data of earthquakes, their origin time, epicentre locations, magnitudes, depths and other details for this time period were obtained from United State Geological Survey (USGS) website. The main goal of this statistical study is to generalize the results about possible relationships between of the ionospheric quasi- static electric field anomalies and the seismic activity. The study proposes also evaluation of some peculiarities in the analyzed quasi-static electric field disturbances such as their appearance time before and after the main shock, amplitudes, sizes, forms and time duration. Present research focuses on four main topics: (i) interrelations among the satellite information, the seismic data and the plate tectonic position of the earthquake sources, (ii) satellite observations of the quasi-static electric field in satellite's orbits above the sources of earthquakes with magnitude M 4.8-7.9 respectively 5-15 days before and 5-15 days after the seismic manifestations, (iii) summary of the statistical study and (iiii) conclusion. In case of small values of Kp index several observation results were used for a correlation analysis between the quasi-static electric field anomalies and the seismic activity. An exciting process of increase of about 2-10 mV/m in the

  13. Deciphering lake and maar geometries from seismic refraction and reflection surveys in Laguna Potrok Aike (southern Patagonia, Argentina)

    NASA Astrophysics Data System (ADS)

    Gebhardt, A. C.; De Batist, M.; Niessen, F.; Anselmetti, F. S.; Ariztegui, D.; Haberzettl, T.; Kopsch, C.; Ohlendorf, C.; Zolitschka, B.

    2011-04-01

    Laguna Potrok Aike is a bowl-shaped maar lake in southern Patagonia, Argentina, with a present mean diameter of ~ 3.5 km and a maximum water depth of ~ 100 m. Seismic surveys were carried out between 2003 and 2005 in order to get a deeper knowledge on the lake sediments and the deeper basin geometries. A raytracing model of the Laguna Potrok Aike basin was calculated based on refraction data while sparker data were additionally used to identify the crater-wall discordance and thus the upper outer shape of the maar structure. The combined data sets show a rather steep funnel-shaped structure embedded in the surrounding Santa Cruz Formation that resembles other well-known maar structures. The infill consists of up to 370 m lacustrine sediments underlain by probably volcanoclastic sediments of unknown thickness. The lacustrine sediments show a subdivision into two sub-units: (a) the upper with seismic velocities between 1500 and 1800 m s - 1 , interpreted as unconsolidated muds, and (b) the lower with higher seismic velocities of up to 2350 m s - 1 , interpreted as lacustrine sediments intercalated with mass transport deposits of different lithology and/or coarser-grained sediments. The postulated volcanoclastic layer has acoustic velocities of > 2400 m s - 1 . The lake sediments were recently drilled within the PASADO project in the framework of the International Continental Scientific Drilling Program (ICDP). Cores penetrated through lacustrine unconsolidated sediments down to a depth of ~ 100 m below lake floor. This minimal thickness for the unconsolidated and low-velocity lithologies is in good agreement with our raytracing model.

  14. 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.

  15. Chromospherically Active Stars in the RAVE Survey

    NASA Astrophysics Data System (ADS)

    Žerjal, M.; Zwitter, T.; Matijevič, G.; Strassmeier, K. G.

    2014-01-01

    We present a qualitative characterization of activity levels of a large database of ~44,000 candidate RAVE stars (unbiased, magnitude limited medium resolution survey) that show chromospheric emission in the Ca II infrared triplet and this vastly enlarges previously known samples. Our main motivation to study these stars is the anti-correlation of chromospheric activity and stellar ages that could be calibrated using stellar clusters with known ages. Locally linear embedding used for a morphological classification of spectra revealed 53,347 cases with a suggested emission component in the calcium lines. We analyzed a subsample of ~44,000 stars with S/N>20 using a spectral subtraction technique where observed reference spectra of inactive stars were used as templates instead of synthetic ones. Both the equivalent width of the excess emission for each calcium line and their sum is derived for all candidate active stars with no respect to the origin of their emission flux. ~17,800 spectra show a detectable chromospheric flux with at least 2 σ confidence level. The overall distribution of activity levels shows a bimodal shape, with the first peak coinciding with inactive stars and the second with the pre-main-sequence cases.

  16. Seismic activity in the transitional segment of Southern Andes after Maule 2010 megathrust earthquake

    NASA Astrophysics Data System (ADS)

    González, Diego; Lupi, Matteo; Bataille, Klaus

    2016-04-01

    It has been shown that after large magnitude earthquakes the region of volcanic arc affected by the megathrust slip is marked by an increase of volcanic activity in the following decades. The Mw = 8.8 Maule 2010 earthquake induced a rupture zone about 500 km long spanning from 33.5°S to 38.5°S. GPS and InSar data show that several volcanic edifices in the Southern Andes underwent a rapid subsidence (from days to months) after the Maule earthquake. To identify the post seismic deformation taking place in the volcanic arc after the Maule earthquake we deployed 20 seismic stations from November 2013 to March 2015 from 35°S to 39°S. We recorded ˜ 600 seismic events larger than Mw = 2.0, concentrated along the slab and beneath the volcanic chain. No events were detected at depths greater than 60 km beneath the volcanic arc. After a preliminary localization, the crustal events were relocated using an improved 1D velocity model. For the largest seismic events we inverted for moment tensor solutions. The moment tensor solution suggest a dominant N-NNE dextral strike-slip local stress field regime. This is in agreement with the direction of ancient geological structures inferred in the basement that were suggested to be reactivated by supra-lithostatic fluid pressures.

  17. 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.

  18. 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

  19. 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.

  20. Recent Results from Crosswell CASSM (Continuous Active-Source Seismic Monitoring)

    NASA Astrophysics Data System (ADS)

    Daley, T. M.; Ajo Franklin, J. B.; Niu, F.

    2011-12-01

    The precision in-situ measurement of seismic properties has been previously demonstrated by crosswell CASSM surveys utilizing piezoelectric seismic sources and various seismic sensors. The underlying precision of travel time measurement (and hence velocity measurement) is shown to be a function of signal-to-noise ratio (S/N), and therefore the semi-permanent CASSM deployment allows massive stacking to provide very large S/N. With high precision data, properties such as the velocity-stress dependence can be resolved. In this presentation, data from three recent CASSM deployments will be shown. First, we will present the recent measurement of stress dependence at 1 km depth in the San Andreas Fault Observatory at Depth (SAFOD). This work follows on the published observation of preseismic stress changes (Niu, et al, 2008) with a redeployment of instrumentation at SAFOD. The latest SAFOD deployment, in which we collected ~40-days of data, from February 19, 2010 to March 31, 2010, suffered from instrumentation failure before observation of seismicity, but data for velocity-stress calibration was acquired using barometric pressure, and the stress sensitivity result of ~2.5 x 10-7 Pa-1 is in agreement with our previous measurement. Secondly, we show a measurement of effective stress dependence in a 3 km deep reservoir used for CO2 sequestration in Cranfield, MS. This experiment uses a fluid pump test, with downhole pressure gauge, to demonstrate a velocity-stress sensitivity of ~5 x 10-6 MPa-1 . In the third CASSM experiment, the methodology was expanded to multi-level measurement (ML-CASSM) of hydrofracture growth in a shallow (~30 m) bioremediation project. In this experiment we demonstrate the first fully automated multi-source/multi-sensor CASSM system capable of tomographic velocity imaging with temporal resolution of 3-4 minutes. This temporal sampling allowed quantitative imaging of velocity changing in response to fracture growth.

  1. Methods and apparatus of suppressing tube waves within a bore hole and seismic surveying systems incorporating same

    DOEpatents

    West, Phillip B.; Haefner, Daryl

    2005-12-13

    Methods and apparatus for attenuating waves in a bore hole, and seismic surveying systems incorporating the same. In one embodiment, an attenuating device includes a soft compliant bladder coupled to a pressurized gas source. A pressure regulating system reduces the pressure of the gas from the gas source prior to entering the bladder and operates in conjunction with the hydrostatic pressure of the fluid in a bore hole to maintain the pressure of the bladder at a specified pressure relative to the surrounding bore hole pressure. Once the hydrostatic pressure of the bore hole fluid exceeds that of the gas source, bore hole fluid may be admitted into a vessel of the gas source to further compress and displace the gas contained therein. In another embodiment, a water-reactive material may be used to provide gas to the bladder wherein the amount of gas generated by the water-reactive material may depend on the hydrostatic pressure of the bore hole fluid.

  2. Methods and apparatus of suppressing tube waves within a bore hole and seismic surveying systems incorporating same

    DOEpatents

    West, Phillip B.; Haefner, Daryl

    2004-08-17

    Methods and apparatus for attenuating waves in a bore hole, and seismic surveying systems incorporating the same. In one embodiment, an attenuating device includes a soft compliant bladder coupled to a pressurized gas source. A pressure regulating system reduces the pressure of the gas from the gas source prior to entering the bladder and operates in conjunction with the hydrostatic pressure of the fluid in a bore hole to maintain the pressure of the bladder at a specified pressure relative to the surrounding bore hole pressure. Once the hydrostatic pressure of the bore hole fluid exceeds that of the gas source, bore hole fluid may be admitted into a vessel of the gas source to further compress and displace the gas contained therein. In another embodiment, a water-reactive material may be used to provide gas to the bladder wherein the amount of gas generated by the water-reactive material may depend on the hydrostatic pressure of the bore hole fluid.

  3. JNCC guidelines for minimising the risk of injury and disturbance to marine mammals from seismic surveys: We can do better.

    PubMed

    Wright, Andrew J; Cosentino, A Mel

    2015-11-15

    The U.K.'s Joint Nature Conservation Committee 1998 guidelines for minimising acoustic impacts from seismic surveys on marine mammals were the first of their kind. Covering both planning and operations, they included various measures for reducing the potential for damaging hearing - an appropriate focus at the time. Since introduction, the guidelines have been criticised for, among other things: the arbitrarily-sized safety zones; the lack of shut-down provisions; the use of mitigation measures that introduce more noise into the environment (e.g., soft-starts); inadequate observer training; and the lack of standardised data collection protocols. Despite the concerns, the guidelines have remained largely unchanged. Moreover, increasing scientific recognition of the scope and magnitude of non-injurious impacts of sound on marine life has become much more widespread since the last revisions in 2010. Accordingly, here we present feasible and realistic recommendations for such improvements, in light of the current state of knowledge.

  4. 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

  5. Multisensor surveys of historical buildings before, during and after a seismic sequence: the leaning bell tower of Ficarolo (Rovigo)

    NASA Astrophysics Data System (ADS)

    Teza, Giordano; Pesci, Arianna; Trevisani, Sebastiano

    2014-05-01

    Three regions of Northern Italy (Emilia Romagna, Veneto and Lombardy) were struck in May-June 2012 by a seismic sequence that included a moment magnitude 5.9 earthquake. Such a sequence caused significant damage to several historical buildings; in some cases complete structural collapse occurred. The 69-m high bell tower of Ficarolo (Rovigo province, Northern Italy) leans at a significant angle (~3° in the shaft). Because the combination of height and leaning angle is visually impressive, Ficarolo is also known as the 'Pisa of Polesine' (Polesine is the Venetian bank of the Po River), referring to the well-known 55-m high, 4° leaning tower of Pisa. A project aimed at studying the geometry of the tower, by means of terrestrial laser scanning (TLS), possible local seismic amplification and soil-structure interaction (SSI), by means of low-cost operational modal analysis (OMA) and geophysical measurements, began in early 2012, before the earthquake. In particular, the first series of data were taken in February 2012 (OMA) and April 2012 (TLS). The distance from Ficarolo of the epicenters of the six events with moment magnitude higher than 5.0 ranged from 9 km to 37 km. Several cracks appeared in the bell tower belfry and cusp. An inclinometer installed in 2003 showed that the base was unchanged, but the upper part of the shaft had moved by 2.5 cm after the main shock. No further displacements were detected as a result of the aftershocks. The repetition of the TLS and OMA surveys during and after the seismic sequence, together with infrared thermal imaging (IRT) measurements, allowed an evaluation of the changes caused by the earthquake. Two main results were obtained: (1) an estimate of earthquake induced damage to the Ficarolo's bell tower, which were relatively limited thanks to absence of SSI, and (2) it was demonstrated that fast measurements can be repeated during earthquake emergencies and that preventive measures can be carried out under reasonable time and

  6. 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.

  7. 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

    Little is known about the controls on the initiation and development of magmatism and segmentation in young rift systems. The northern Lake Malawi (Nyasa) rift in the East African Rift System is an early stage rift exhibiting pronounced tectonic segmentation, which is defined in the upper crust by ~100-km-long border faults. Very little volcanism is associated with rifting; the only surface expression of magmatism occurs in an accommodation zone between segments to the north of the lake in the Rungwe Volcanic Province. The SEGMeNT (Study of Extension and maGmatism in Malawi aNd Tanzania) project is a multidisciplinary, multinational study that is acquiring a suite of geophysical, geological and geochemical data to characterize deformation and magmatism in the crust and mantle lithosphere along 2-3 segments of this rift. As a part of the SEGMeNT project, we acquired seismic reflection and refraction data in Lake Malawi (Nyasa) in March-April 2015. Over 2000 km of seismic reflection data were acquired with a 500 to 2580 cu in air gun array from GEUS/Aarhus and a 500- to 1500-m-long seismic streamer from Syracuse University over a grid of lines across and along the northern and central basins. Air gun shots from MCS profiles and 1000 km of additional shooting with large shot intervals were also recorded on 27 short-period and 6 broadband lake bottom seismometers from Scripps Oceanographic Institute as a part of the Ocean Bottom Seismic Instrument Pool (OBSIP) as well as the 55-station onshore seismic array. The OBS were deployed along one long strike line and two dip lines. We will present preliminary data and results from seismic reflection and refraction data acquired in the lake and their implications for crustal deformation within and between rift segments. Seismic reflection data image structures up to ~5-6 km below the lake bottom, including syntectonic sediments, intrabasinal faults and other complex horsts. Some intrabasinal faults in both the northern and

  8. Seismic reflection survey at Ayer Hangat site to investigate shallow subsurface structures

    NASA Astrophysics Data System (ADS)

    Khalil, Amin E.; Nawawi, Mohd; Kamel, Rami

    2016-01-01

    Ayer Hangat site is located in the island of Langkawi, northwest Malaysia. The site is characterized by the presence of hot spring. This hot spring is believed to be related to granitic intrusion nearby. Hence the present work is focusing on defining the shallow subsurface structures that control the migration of hot water to the surface. Seismic reflection method is used to achieve the goal of the present study. Forty three shot points were used with an offset of 5m of the nearest geophone. The shot-points interval is set to 1m. Seismograms were recorded on 24 channel TERRALOC instrument. The Geophone interval used was 1m. Conventional seismic data processing scheme was adopted. However, due to the fact that TERRALOC produce SEG2 data files, a script based on Obspy was written and used to convert to SEG-Y format. Afterwards, analyses were carried out using SU Package. The processed data is used to develop a model for the subsurface controlling structures. Such model will help in the understanding of the geothermal hot spring system in the area.

  9. Archive of digital boomer seismic reflection data collected during USGS field activities 95LCA03 and 96LCA02 in the Peace River of West-Central Florida, 1995 and 1996

    USGS Publications Warehouse

    Calderon, Karynna; Dadisman, Shawn V.; Tihansky, Ann B.; Lewelling, Bill R.; Flocks, James G.; Wiese, Dana S.; Kindinger, Jack G.; Harrison, Arnell S.

    2006-01-01

    In October and November of 1995 and February of 1996, the U.S. Geological Survey, in cooperation with the Southwest Florida Water Management District, conducted geophysical surveys of the Peace River in west-central Florida from east of Bartow to west of Arcadia. This report serves as an archive of unprocessed digital boomer seismic reflection data, trackline maps, navigation files, GIS files, Field Activity Collection System (FACS) logs, observers' logbooks, and formal FGDC metadata. Filtered and gained digital images of the seismic profiles are also provided. Refer to the Acronyms page for expansion of acronyms and abbreviations used in this report. The archived trace data are in standard Society of Exploration Geophysicists (SEG) SEG-Y format (Barry and others, 1975) and may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU). Example SU processing scripts and USGS software for viewing the SEG-Y files (Zihlman, 1992) are also provided.

  10. Land 3D-seismic data: Preprocessing quality control utilizing survey design specifications, noise properties, normal moveout, first breaks, and offset

    USGS Publications Warehouse

    Raef, A.

    2009-01-01

    The recent proliferation of the 3D reflection seismic method into the near-surface area of geophysical applications, especially in response to the emergence of the need to comprehensively characterize and monitor near-surface carbon dioxide sequestration in shallow saline aquifers around the world, justifies the emphasis on cost-effective and robust quality control and assurance (QC/QA) workflow of 3D seismic data preprocessing that is suitable for near-surface applications. The main purpose of our seismic data preprocessing QC is to enable the use of appropriate header information, data that are free of noise-dominated traces, and/or flawed vertical stacking in subsequent processing steps. In this article, I provide an account of utilizing survey design specifications, noise properties, first breaks, and normal moveout for rapid and thorough graphical QC/QA diagnostics, which are easy to apply and efficient in the diagnosis of inconsistencies. A correlated vibroseis time-lapse 3D-seismic data set from a CO2-flood monitoring survey is used for demonstrating QC diagnostics. An important by-product of the QC workflow is establishing the number of layers for a refraction statics model in a data-driven graphical manner that capitalizes on the spatial coverage of the 3D seismic data. ?? China University of Geosciences (Wuhan) and Springer-Verlag GmbH 2009.

  11. Summary of workshops concerning regional seismic source zones of parts of the conterminous United States, convened by the U.S. Geological Survey, 1979-1980, Golden, Colorado

    USGS Publications Warehouse

    Thenhaus, Paul C.

    1983-01-01

    Workshops were convened by the U.S. Geological Survey to obtain the latest information and concepts relative to defining seismic source zones for five regions of the United States. The zones, with some modifications, have been used in preparation of new national probabilistic ground motion hazard maps by the U.S. Geological Survey. The five regions addressed are the Great Basin, the Northern Rocky Mountains, the Southern Rocky Mountains, the Central Interior, and' the northeastern United States. Discussions at the workshops focussed on possible temporal and spatial variations of seismicity within the regions, latest ages of surface-fault displacements, most recent uplift or subsidence, geologic structural provinces as they relate to seismicity, and speculation on earthquake causes. Within the Great Basin region, the zones conform to areas characterized by a predominance of faults that have certain ages of latest surface displacements. In the Northern and Southern Rocky Mountain regions, zones primarily conform to distinctive structural terrane. In the Central Interior, primary emphasis was placed on an interpretation of the areal distribution of historic seismicity, although geophysical studies in the Reelfoot rift area provided data for defining zones in the New Madrid earthquake area. An interpretation of the historic seismicity also provided the basis for drawing the zones of the New England region. Estimates of earthquake maximum magnitudes and of recurrence times for these earthquakes are given for most of the zones and are based on either geologic data or opinion.

  12. The application of active-source seismic imaging techniques to transtensional problems the Walker Lane and Salton Trough

    NASA Astrophysics Data System (ADS)

    Kell, Anna Marie

    The plate margin in the western United States is an active tectonic region that contains the integrated deformation between the North American and Pacific plates. Nearly focused plate motion between the North American and Pacific plates within the northern Gulf of California gives way north of the Salton Trough to more diffuse deformation. In particular a large fraction of the slip along the southernmost San Andreas fault ultimately bleeds eastward, including about 20% of the total plate motion budget that finds its way through the transtensional Walker Lane Deformation Belt just east of the Sierra Nevada mountain range. Fault-bounded ranges combined with intervening low-lying basins characterize this region; the down-dropped features are often filled with water, which present opportunities for seismic imaging at unprecedented scales. Here I present active-source seismic imaging from the Salton Sea and Walker Lane Deformation Belt, including both marine applications in lakes and shallow seas, and more conventional land-based techniques along the Carson range front. The complex fault network beneath the Salton Trough in eastern California is the on-land continuation of the Gulf of California rift system, where North American-Pacific plate motion is accommodated by a series of long transform faults, separated by small pull-apart, transtensional basins; the right-lateral San Andreas fault bounds this system to the north where it carries, on average, about 50% of total plate motion. The Salton Sea resides within the most youthful and northerly "spreading center" in this several thousand-kilometer-long rift system. The Sea provides an ideal environment for the use of high-data-density marine seismic techniques. Two active-source seismic campaigns in 2010 and 2011 show progression of the development of the Salton pull-apart sub-basin and the northerly propagation of the Imperial-San Andreas system through time at varying resolutions. High fidelity seismic imagery

  13. Borehole-explosion and air-gun data acquired in the 2011 Salton Seismic Imaging Project (SSIP), southern California: description of the survey

    USGS Publications Warehouse

    Rose, Elizabeth J.; Fuis, Gary S.; Stock, Joann M.; Hole, John A.; Kell, Annie M.; Kent, Graham; Driscoll, Neal W.; Goldman, Mark; Reusch, Angela M.; Han, Liang; Sickler, Robert R.; Catchings, Rufus D.; Rymer, Michael J.; Criley, Coyn J.; Scheirer, Daniel S.; Skinner, Steven M.; Slayday-Criley, Coye J.; Murphy, Janice M.; Jensen, Edward G.; McClearn, Robert; Ferguson, Alex J.; Butcher, Lesley A.; Gardner, Max A.; Emmons, Iain; Loughran, Caleb L.; Svitek, Joseph R.; Bastien, Patrick C.; Cotton, Joseph A.; Croker, David S.; Harding, Alistair J.; Babcock, Jeffrey M.; Harder, Steven H.; Rosa, Carla M.

    2013-01-01

    The Imperial and Coachella Valleys are being formed by active plate-tectonic processes. From the Imperial Valley southward into the Gulf of California, plate motions are rifting the continent apart. In the Coachella Valley, the plates are sliding past one another along the San Andreas and related faults (fig. 1). These processes build the stunning landscapes of the region, but also produce damaging earthquakes. Rupture of the southern section of the San Andreas Fault (SAF), from the Coachella Valley to the Mojave Desert, is believed to be the greatest natural hazard that California will face in the near future. With an estimated magnitude between 7.2 and 8.1, such an event would result in violent shaking, loss of life, and disruption of infrastructure (freeways, aqueducts, power, petroleum, and communication lines) that might bring much of southern California to a standstill. As part of the nation’s efforts to avert a catastrophe of this magnitude, a number of projects have been undertaken to more fully understand and mitigate the effects of such an event. The Salton Seismic Imaging Project (SSIP), funded jointly by the National Science Foundation (NSF) and the U.S. Geological Survey (USGS), seeks to understand, through seismic imaging, the structure of the Earth surrounding the SAF, including the sedimentary basins on which cities are built. The principal investigators (PIs) of this collaborative project represent the USGS, Virginia Polytechnic Institute and State University (Virginia Tech), California Institute of Technology (Caltech), Scripps Institution of Oceanography (Scripps), University of Nevada, Reno (UNR), and Stanford University. SSIP will create images of underground structure and sediments in the Imperial and Coachella Valleys and adjacent mountain ranges to investigate the earthquake hazards posed to cities in this area. Importantly, the images will help determine the underground geometry of the SAF, how deep the sediments are, and how fast

  14. Deep seismic survey images crustal structure of Tornquist Zone beneath southern Baltic Sea

    SciTech Connect

    Not Available

    1991-06-01

    The Tornquist Zone is Europe's longest tectonic lineament and bisects the continent in a NW-SE direction from the North Sea (off NW Denmark) to the Black Sea. New deep seismic reflection and coincident refraction data have been collected across its 50 km wide, intensely faulted and inverted NW part. The marine reflection profile in the area north of Bornholm Island shows a tilted block structure in the rigid upper crust, whereas the lower crust seems to be more gently uplifted. A complex transition from the highly reflective lower crust to the mantle is indicated by mantle reflections and a curious wide-angle event recorded by a landstation on Bornholm Island. The authors suggest that deep-reaching inversion tectonics, induced by Alpine and Carpathian orogeny, were responsible for the development of the gross crust-mantle structure of the Tornquist Zone in the study area, which seems to be similar to that in Poland.

  15. High-resolution seismic reflection survey at the Manson crater, Iowa

    NASA Technical Reports Server (NTRS)

    Keiswetter, D. A.; Black, R.; Steeples, D. W.; Anderson, R. R.

    1993-01-01

    Approximately 17.4 km of high-resolution reflection data were acquired along an east-west radius of the Manson Impact Structure (MIS) to delineate the shallow (upper 300 m) subsurface structural configuration. The geometry of the shallow structure is poorly known due to a 30-90 m thick Pleistocene till cover. The resolution of the new seismic data is roughly 5-10 times that of existing Vibroseis data. Data quality varies rapidly along the line from exceptional to poor, due primarily to velocity variations associated with the geological complexity of the area. Preliminary results indicate subsurface structural blocks previously envisioned to be several hundreds of meters in size are actually an order of magnitude smaller and more complex. A seismogram-by-seismogram analysis is necessary to confidently identify intricate stratigraphic and structural relationships seen on preliminary CDP sections, as numerous faults, diffractions, and complicated reflection patterns create potential pitfalls.

  16. 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

  17. 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.

  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. Probabilistic seismic hazard study based on active fault and finite element geodynamic models

    NASA Astrophysics Data System (ADS)

    Kastelic, Vanja; Carafa, Michele M. C.; Visini, Francesco

    2016-04-01

    We present a probabilistic seismic hazard analysis (PSHA) that is exclusively based on active faults and geodynamic finite element input models whereas seismic catalogues were used only in a posterior comparison. We applied the developed model in the External Dinarides, a slow deforming thrust-and-fold belt at the contact between Adria and Eurasia.. is the Our method consists of establishing s two earthquake rupture forecast models: (i) a geological active fault input (GEO) model and, (ii) a finite element (FEM) model. The GEO model is based on active fault database that provides information on fault location and its geometric and kinematic parameters together with estimations on its slip rate. By default in this model all deformation is set to be released along the active faults. The FEM model is based on a numerical geodynamic model developed for the region of study. In this model the deformation is, besides along the active faults, released also in the volumetric continuum elements. From both models we calculated their corresponding activity rates, its earthquake rates and their final expected peak ground accelerations. We investigated both the source model and the earthquake model uncertainties by varying the main active fault and earthquake rate calculation parameters through constructing corresponding branches of the seismic hazard logic tree. Hazard maps and UHS curves have been produced for horizontal ground motion on bedrock conditions VS 30 ≥ 800 m/s), thereby not considering local site amplification effects. The hazard was computed over a 0.2° spaced grid considering 648 branches of the logic tree and the mean value of 10% probability of exceedance in 50 years hazard level, while the 5th and 95th percentiles were also computed to investigate the model limits. We conducted a sensitivity analysis to control which of the input parameters influence the final hazard results in which measure. The results of such comparison evidence the deformation model and

  20. 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.

  1. 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

  2. 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.

  3. The Crustal Structure of Northern Continental Margin of South China Sea: Revealed by Joint Onshore-Offshore Wide-Angle Seismic Survey

    NASA Astrophysics Data System (ADS)

    Cao, J.; Sun, J.; Xia, S.; Xu, H.

    2015-12-01

    The northern margin of South China Sea (SCS) is a rifted margin which located in the jointing area between South China Block and SCS Basin, it not only preserved the information about intensive tectonic deformation and magmatism generated by the west Pacific subducted to Eurasian Plate in late Mesozoic, but also recorded the process from continental margin rifting to seafloor spreading of SCS in Cenozoic for the same mechanical property. To investigate crustal structure of northern margin of SCS, a wide-angle onshore-offshore seismic experiment and a coincident multi-channel seismic (MCS) profile were carried out in the northern margin of SCS, 2010. A total of 14 stations consisted of ocean bottom seismometers, portable and permanent land stations were deployed during the survey. The two-dimensional precise crustal structure model of Pearl River Estuary (PRE) region was constructed from onshore to offshore. The model reveals that South mainland of China is a typical continental crust with a 30-32 km Moho depth, and a localized high-velocity anomaly in middle-lower crust under land area near Hong Kong was imaged, which may reflect magma underplating caused by subduction of paleo-Pacific plate in late Mesozoic. The Littoral Fault Zone (LFZ) lies 12 km south of Dangan Island with a width of 18-20 km low-velocity fracture zone from surface to Moho discontinuity. The shelf zone south of LFZ was consisted of a differential thinning upper and lower continental crust, which indicate stretch thinning of passive continent margin during the Cenozoic spreading of the SCS. All these results appear to further confirm that the northern margin of SCS experienced a transition from active margin to passive one from late Mesozoic to Cenozoic.

  4. Seismic investigations of ancient Lake Ohrid (Macedonia/Albania): a pre-site survey for the SCOPSCO ICDP-drilling campaign

    NASA Astrophysics Data System (ADS)

    Lindhorst, K.; Krastel, S.; Schwenk, T.; Kurschat, S.; Daut, G.; Wessel, M.; Wagner, B.

    2009-04-01

    Lake Ohrid (Macedonia/Albania) is probably the oldest lake in Europe (2-5 Ma), and has been found as an important archive to study the sedimentary evolution of a graben system over several million years. Lake Ohrid has a length of 30 km (N-S) and a width of 15 km (W-E) and covers an area of 360 sqkm. Two major mountain chains surround the lake, on the west side the Mocra Mountains (app. 1500 m) and on the east side the Galicica Mountain (app. 2250 m). With more than 210 endemic species described, the lake is a unique aquatic ecosystem that is of worldwide importance. An international group of scientists has recently submitted a full drilling proposal entitled SCOPSCO (Scientific Collaboration On Past Speciation Conditions in Lake Ohrid) to ICDP in order to (i) to obtain more precise information about the age and origin of the lake, (ii) to unravel the seismotectonic history of the lake area including effects of major earthquakes and associated mass wasting events, (iii) to obtain a continuous record containing information on volcanic activities and climate changes in the central northern Mediterranean region, and (iv) to better understand the impact of major geological/environmental events on general evolutionary patterns and shaping an extraordinary degree of endemic biodiversity as a matter of global significance. The lake was the target of several geophysical pre-site surveys starting with a first shallow seismic campaign in spring 2004 using a high resolution parametric sediment echosounder (INNOMAR SES-96 light). Airgun multichannel seismic data were collected during two surveys in 2007 and 2008, resulting in a dense grid of seismic lines over the entire lake. In total 650 km of shallow seismic lines 400 km of airgun multichannel seismics demonstrates the potential of Lake Ohrid as target for ICDP. Seismic profiles show that the lake can be divided into slope areas and a large central basin. The slope areas are characterized by a dense net of faults

  5. 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.

  6. Crustal Thickness Variations Along the Southeastern Caribbean Plate Boundary From Teleseismic and Active Source Seismic Data

    NASA Astrophysics Data System (ADS)

    Bezada, M. J.; Niu, F.; Baldwin, T. K.; Pavlis, G.; Vernon, F.; Rendón, H.; Zelt, C. A.; Schmitz, M.; Levander, A.

    2006-12-01

    Insight into the topography of the Moho discontinuity beneath Venezuela has been progressively gained since the 1990's through seismic refraction studies carried out in the south and east of the country. More recently, both active and passive, land and marine seismic data were acquired by the U.S. BOLIVAR and Venezuelan GEODINOS projects to understand accretion processes and mechanisms for continental growth. The passive component includes an 18-month deployment of 27 PASSCAL broadband seismographs, a 12-month deployment of 15 OBSIP broadband instruments and an ongoing deployment of 8 Rice broadband seismometers. Additionally, data from the 34 BB stations of the national seismic network of Venezuela and the GSN SDV station, give a seismic dataset from 84 stations covering an area of ~750,000 km2. The active component includes 4 onshore-offshore refraction/wide angle reflection profiles as well as the recording of airgun blasts from offshore seismic lines by BB stations in mainland Venezuela and the Leeward Antilles. This abundance of datasets allows us to estimate Moho depths using different methods such as receiver functions, and forward and inverse modeling of wide-angle datasets, but also poses the challenge of reconciling the different values obtained to achieve robust results. Generally the active source and receiver function estimates are close to one another. We present a composite crustal thickness map showing a highly variable crustal thicknesses ranging from 15 km beneath the Caribbean LIP, to ~55 km beneath eastern Venezuela. Crustal thickness is strongly correlated with geologic terranes, but not always as expected. The thickest crust is found to exist in the east of the country, beneath the sedimentary basins north of the Orinoco River where depth to Moho exceeds 50 km. Crustal thickness beneath most of the Precambrian Guayana Shield is fairly constant at ~38 km . In contrast, we observe relatively thin (~25-30 km) crust in the eastern and western

  7. Solar-terrestrial effect controls seismic activity to a large extent (Invited)

    NASA Astrophysics Data System (ADS)

    Duma, G.

    2010-12-01

    Several observational results and corresponding publications in the 20 century indicate that earthquakes in many regions happen systematically in dependence on the time of day and on the season as well. In the recent decade, studies on this topic have also been intensively performed at the Central Institute for Meteorology and Geodynamics (ZAMG), Vienna. Any natural effect on Earth which systematically appears at certain hours of the day or at a special season can solely be caused by a solar or lunar influence. And actually, statistic results on seismic activity reveal a correlation with the solar cycles. Examples of this seismic performance are shown. To gain more clarity about these effects, the three-hour magnetic index Kp, which characterizes the magnetic field disturbances, mainly caused by the solar particle radiation, the solar wind, was correlated with the seismic energy released by earthquakes over decades. Kp is determined from magnetic records of 13 observatories worldwide and continuously published by ISGI, France. It is demonstrated that a highly significant correlation between the geomagnetic index Kp and the annual seismic energy release in regions at latitudes between 35 and 60° N exists. Three regions of continental size were investigated, using the USGS (PDE) earthquake catalogue data. In the period 1974-2009 the Kp cycle periods range between 9 and 12 years, somewhat different to the sunspot number cycles of 11 years. Seismicity follows the Kp cycles with high coincidence. A detailed analysis of this correlation for N-America reveals, that the sum of released energy by earthquakes per year changes by a factor up to 100 with Kp. It is shown that during years of high Kp there happen e.g. 1 event M7, 4 events M6 and 30 events M5 per year, instead of only 10 events M5 in years with lowest Kp. Almost the same relation appears in other regions of continental size, with the same significance. The seismicity in S-America clearly follows the Kp cycles

  8. 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

  9. Motif Discovery on Seismic Amplitude Time Series: The Case Study of Mt Etna 2011 Eruptive Activity

    NASA Astrophysics Data System (ADS)

    Cassisi, Carmelo; Aliotta, Marco; Cannata, Andrea; Montalto, Placido; Patanè, Domenico; Pulvirenti, Alfredo; Spampinato, Letizia

    2013-04-01

    Algorithms searching for similar patterns are widely used in seismology both when the waveforms of the events of interest are known and when there is no a priori-knowledge. Such methods usually make use of the cross-correlation coefficient as a measure of similarity; if there is no a-priori knowledge, they behave as brute-force searching algorithms. The disadvantage of these methods, preventing or limiting their application to very large datasets, is computational complexity. The Mueen-Keogh (MK) algorithm overcomes this limitation by means of two optimization techniques—the early abandoning concept and space indexing. Here, we apply the MK algorithm to amplitude time series retrieved from seismic signals recorded during episodic eruptive activity of Mt Etna in 2011. By adequately tuning the input to the MK algorithm we found eight motif groups characterized by distinct seismic amplitude trends, each related to a different phenomenon. In particular, we observed that earthquakes are accompanied by sharp increases and decreases in seismic amplitude whereas lava fountains are accompanied by slower changes. These results demonstrate that the MK algorithm, because of its particular features, may have wide applicability in seismology.

  10. 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.

  11. 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.

  12. 2008 United States National Seismic Hazard Maps

    USGS Publications Warehouse

    Petersen, M.D.; ,

    2008-01-01

    The U.S. Geological Survey recently updated the National Seismic Hazard Maps by incorporating new seismic, geologic, and geodetic information on earthquake rates and associated ground shaking. The 2008 versions supersede those released in 1996 and 2002. These maps are the basis for seismic design provisions of building codes, insurance rate structures, earthquake loss studies, retrofit priorities, and land-use planning. Their use in design of buildings, bridges, highways, and critical infrastructure allows structures to better withstand earthquake shaking, saving lives and reducing disruption to critical activities following a damaging event. The maps also help engineers avoid costs from over-design for unlikely levels of ground motion.

  13. Seismic response of torsionally coupled building with passive and semi-active stiffness dampers

    NASA Astrophysics Data System (ADS)

    Mevada, Snehal V.; Jangid, R. S.

    2015-03-01

    The seismic response of single-storey, one-way asymmetric building with passive and semi-active variable stiffness dampers is investigated. The governing equations of motion are derived based on the mathematical model of asymmetric building. The seismic response of the system is obtained by numerically solving the equations of motion using state-space method under different system parameters. The switching and resetting control laws are considered for the semi-active devices. The important parameters considered are eccentricity ratio of superstructure, uncoupled lateral time period and ratio of uncoupled torsional to lateral frequency. The effects of these parameters are investigated on peak lateral, torsional and edge displacements and accelerations as well as on damper control forces. The comparative performance is investigated for asymmetric building installed with passive stiffness and semi-active stiffness dampers. It is shown that the semi-active stiffness dampers reduce the earthquake-induced displacements and accelerations significantly as compared to passive stiffness dampers. Also, the effects of torsional coupling on effectiveness of passive dampers in reducing displacements and accelerations are found to be more significant to the variation of eccentricity as compared to semi-active stiffness dampers.

  14. The Evolution of the Campi Flegrei caldera (Italy): High- and low-frequency multichannel 2.5D seismic surveying for an amphibian IODP/ICDP drilling approach

    NASA Astrophysics Data System (ADS)

    Steinmann, Lena; Spiess, Volkhard; Sacchi, Marco

    2016-04-01

    Caldera-forming eruptions are considered as one of the most catastrophic natural events to affect the Earth's surface and human society. The half-submerged Campi Flegrei caldera, located in southern Italy, belongs to the world's most active calderas and, thus, has received particular attention in scientific communities and governmental institutions. Therefore, it has also become subject to a joint approach in the IODP and ICDP programmes. Despite ample research, no scientific consensus regarding the formation history of the Campi Flegrei caldera has been reached yet. So far, it is still under debate whether the Campi Flegrei caldera was formed by only one ignimbritic eruption, namely the Neapolitan Yellow Tuff (NYT) eruption at 15 ka or, if it is a nested-caldera system related to the NYT and the Campanian Ignimbrite (CI) eruption at 39 ka. In the last decades, the Campi Flegrei caldera has been characterized by short-term episodes of unrest involving considerable ground deformation (uplift and subsidence of several meters), seismicity and increased temperature at fumaroles. Furthermore, long-term deformation can be observed in the central part of the caldera with uplift rates of several tens of meters within a few thousand years. Recently, it has been proposed that the long-term deformation may be related to caldera resurgence, while short-term uplift episodes are probably triggered by the injection of magmatic fluids into a shallow hydrothermal system at ~2 km depth. However, both long-term and short term uplift could be interpreted as eruption precursor, thereby posing high-concern for a future eruption, which would expose more than 1.5 million people living in the surroundings of the volcanic district to extreme volcanic risks. During a joint Italian-German research expedition in 2008, a semi-3D grid (100-150 m profile spacing) of high-frequency (up to 1000 Hz) multichannel seismic data were acquired to support both the ongoing onshore ICDP and a proposed

  15. Deformation across the seismic cycle in tectonically active regions: Imaging, modeling, and interpretations

    NASA Astrophysics Data System (ADS)

    Barnhart, William Douglas

    Images of surface displacements in response to tectonic forces can provide independent, spatially dense observations that assist in understanding sub-surface processes. When considered independently or augmented with more traditional observations of active tectonics such as seismicity and ground mapping, these measurements provide constraints on spatially and temporally variable fault behavior across the seismic cycle. Models of fault behavior inferred from these observations in turn allow us to address topics in geologic hazards assessment, the long- and short-term character of strain in deforming regions, and the interactions between faults throughout the crust. In this dissertation, I use remotely sensed observations of ground displacements from interferometric synthetic aperture radar (InSAR) to approach several problems related to earthquake and aseismic fault slip. I establish image processing and inverse methods for better detailing subsurface fault slip and apply these to the 2010-2011 Canterbury, New Zealand sequence. Then, I focus on the active tectonics of the Zagros Mountains in southern Iran. There, I show through orogen-wide InSAR time series analysis that active strain is accommodated across the width of the mountain belt. I also use a combination of InSAR, local seismicity, and structural modeling to demonstrate that strain is vertically partitioned within the Zagros fold-and-thrust belt, with earthquakes controlling deformation in the underlying basement while the overlying sedimentary section shortens in transient, earthquake-triggered aseismic slip events. In certain examples, these aseismic slip events directly contribute to the growth of fault-bend folds. I use these inferences to explore a previously noted discrepancy between observed shortening and that which is expected from known earthquakes. I show that the earthquakes and short-term aseismic slip cannot account for this discrepancy, and that additional deformation mechanisms must be

  16. 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

  17. Preliminary study for active monitoring of the plate boundary using ACROSS: Synthetic and observed seismic records

    NASA Astrophysics Data System (ADS)

    Tsuruga, K.; Kasahara, J.; Hasada, Y.; Kunitomo, T.; Ikuta, R.; Watanabe, T.; Yamaoka, K.; Fujii, N.; Kumazawa, M.; Nagao, H.; Nakajima, T.; Saiga, A.; Satomura, M.

    2005-12-01

    ACROSS (Accurately-Controlled Routinely-Operated Signal System) has been developed for active monitoring of a dynamic state in the Earth's structure (Kumazawa et al., 2000). Since November 2004, we have conducted an array observation of ACROSS signals in Tokai area, central Japan, to identify any seismic reflection (and hopefully its temporal change) from the lower crust and/or subducting Philippine Sea plate (Kasahara et al., 2004). In this report, we show the recent results and discuss the relevance of several arrivals of wave groups to underground structures using the theoretical travel times and synthetic waveforms. The frequency-modulated ACROSS signals (10-20 Hz) have been continuously transmitted from the sources located in Toki city, central Japan (Kunitomo et al., 2005) and received at 22 temporal seismic stations at the offset distance of 40-75 km from the source. We define the transfer function between a source and a receiver as a nine-element second-order tensor, Hjk, where j and k denote directional components of the observed displacement and the excitation force, and r, t and v represent the radial, transverse and vertical components, respectively. We recognized the significant wave groups within the travel time ranges of 10-18 and of 15-23 seconds at 54-74 km offset distance through stacking the data for about 60 days. Such wave groups also appear on the records of a Hi-net station at 57.4km by stacking for 30 days (Yoshida et al., 2004). A 2-D velocity structure model was made for our observation area using seismic exploration records across the central Japan (Iidaka et al., 2003). We calculated both travel times by ray tracing method (Fujie et al., 2000; Kubota et al., 2005), and synthetic seismograms by FDM simulation (Larsen and Schultz, 1995). Comparing the observed time series of Hrr and Hzr to the theoretical travel times and synthetic seismograms, we noticed that the wave groups observed at 61-73 km are well corresponding to the theoretical

  18. 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.

  19. Results of a shallow seismic-refraction survey in the Little Valley area near Hemet, Riverside County, California

    USGS Publications Warehouse

    Duell, L.F., Jr.

    1995-01-01

    Little Valley, a small locally named valley southeast of the city of Hemet in Riverside County, California, is being evaluated for development of a constructed wetland and infiltration area as part of a water-resources management program in the area. The valley is a granitic basin filled with unconsolidated material. In August 1993 and June and July 1994, the U.S. Geological Survey conducted a seismic-refraction survey consisting of four lines northwest of the valley, eight lines in the valley, and six lines northeast of the valley. Two interpretations were made for the lines: a two-layer model yielded an estimate of the minimum depths to bedrock and a three-layer model yielded the most likely depths to bedrock. Results of the interpretation of the three-layer model indicate that the unsaturated unconsolidated surface layer ranges in thickness from 12 to 83 feet in the valley and 24 to 131 feet northeast of the valley. The mean compressional velocity for this layer was about 1,660 feet per second. A saturated middle layer was detected in some parts of the study area, but not in others--probably because of insufficient thickness in some places; however, in order to determine the "most likely" depths to bedrock, it was assumed that the layer was present throughout the valley. Depths to this layer were verified on three seismic lines using the water level from the only well in the valley. Data for additional verification were not available for wells near Little Valley. The bedrock slope from most of Little Valley is down toward the northeast. Bedrock profiles show that the bedrock surface is very uneven in the study area. The interpreted most likely depth to bedrock in the valley ranged from land surface (exposed) to a depth of 176 feet below land surface, and northeast of the valley it ranged from 118 to 331 feet below land surface. Bedrock depths were verified using lithologic logs from test holes drilled previously in the area. On the basis of a measured mean

  20. Crosswell acoustic surveying in gas sands: Travel-time pattern recognition, seismic Q and channel waves

    NASA Astrophysics Data System (ADS)

    Albright, J. N.; Johnson, P. A.

    The application of crosswell acoustic measurements to gas sands research has been explored through surveys conducted in the Mesa Verde formation at the Department of Energy Multi-Well Experiment (MWX) site near Rifle, Colorado. The borehole tools used in the survey are similar in concept to those used in commercial service for sonic logging, but they are especially adapted for the stringent requirements of crosswell shooting in hot gas wells. Important information about the geologic structure between wells can be extracted from crosswell scans without resorting to elaborate processing. A useful representation is a display of the travel time of P-waves in terms of the cylindrical coordinates of the transmitter referenced to the receiver. This is known as a gamma-depth ((GAMMA)-Z) plot. Such a representation may yield distinctive patterns, which can be interpreted based on the successful replication of the pattern through computer simulations.

  1. 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

  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. 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.

  4. Seismic anisotropy across the Longmen Shan mountain range from a passive seismological survey.

    NASA Astrophysics Data System (ADS)

    Herquel, G.; Robert, A.; Vergne, J.; Zhu, J.

    2008-12-01

    Located between the eastern margin of the Tibetan plateau and the Yangtze craton, the Longmen Shan mountains range is a key area for understanding mechanisms that control the deformation and the eastward extrusion of the Tibetan plateau. This context motivated several French institutes and the University of Chengdu to set up a seismic network across the Longmen Shan to determine the patterns of the lithospheric deformation in this region. The profile, composed of 36 stations with a mean inter-station spacing of 10km, was deployed in several phases from November 2005 to April 2007 and ran from the Sichuan basin, across the Longmen Shan fold belt, the Songpan Garze terrane and up to the Xianshuhe fault. Here, we present the first results from this experiment about the anisotropy within the lithosphere based on shear wave splitting measurements. 41 clear SKS and SKKS phases from 23 teleseismic events were recorded during the two periods of deployment and selected through visual inspection. We used the cross- correlation method to calculate the splitting parameters, that is, the azimuth of the past polarization direction and the delay time between the split phases arrivals. We show that 1) The polarization directions are coherent in all the studied zone. They are compatible with previous observations, GPS measurements and with the main known surface features like the Xianshuhe strike-slip fault. Strikingly, no significant change is observed between the Longmen Shan region and the eastern part of the Yangtze craton; 2) The measured delays are small and don't reflect important asthenospheric flow. Some measurements of S splitting near the Beichuan-Weichuan fault system show normal anisotropy for the crust (around 0.05 to 0.1s). Based on these results, the origin of anisotropy seems to be confined to the lithosphere and coherent deformation of the crust and mantle lithosphere cannot be excluded.

  5. Worksite Health Promotion Activities. 1992 National Survey. Summary Report.

    ERIC Educational Resources Information Center

    Public Health Service (DHHS), Rockville, MD. Office of Disease Prevention and Health Promotion.

    The survey reported in this document examined worksite health promotion and disease prevention activities in 1,507 private worksites in the United States. Specificlly, the survey assessed policies, practices, services, facilities, information, and activities sponsored by employers to improve the health of their employees, and assessed health…

  6. 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.

  7. Application of 3D reflection seismic methods to mineral exploration

    NASA Astrophysics Data System (ADS)

    Urosevic, Milovan

    2013-04-01

    Seismic exploration for mineral deposits is often tested by excessively complex structures, regolith heterogeneity, intrinsically low signal to noise ratio, ground relief and accessibility. In brown fields, where the majority of the seismic surveys have been conducted, existing infrastructure, old pits and tailings, heavy machinery in operation, mine drainage and other mine related activities are further challenging the application of seismic methods and furthermore increasing its cost. It is therefore not surprising that the mining industry has been reluctant to use seismic methods, particularly 3D for mineral exploration, primarily due to the high cost, but also because of variable performance, and in some cases ambiguous interpretation results. However, shallow mineral reserves are becoming depleted and exploration is moving towards deeper targets. Seismic methods will be more important for deeper investigations and may become the primary exploration tool in the near future. The big issue is if we have an appropriate seismic "strategy" for exploration of deep, complex mineral reserves. From the existing case histories worldwide we know that massive ore deposits (VMS, VHMS) constitute the best case scenario for the application of 3D seismic. Direct targeting of massive ore bodies from seismic has been documented in several case histories. Sediment hosted deposits could, in some cases, can also produce a detectable seismic signature. Other deposit types such as IOCG and skarn are much more challenging for the application of seismic methods. The complexity of these deposits requires new thinking. Several 3D surveys acquired over different deposit types will be presented and discussed.

  8. A one year long continuous record of seismic activity and surface motion at the tongue of Rhonegletscher (Valais, Switzerland)

    NASA Astrophysics Data System (ADS)

    Dalban Canassy, Pierre; Röösli, Claudia; Walter, Fabian; Gabbi, Jeannette

    2014-05-01

    A critical gap in our current understanding of glaciers is how high sub-glacial water pressure controls the coupling of the glacier to its bed. Processes at the base of a glacier are inherently difficult to investigate due to their remoteness. Investigation of the sub-glacial environment with passive seismic methods is an innovative, rapidly growing interdisciplinary and promising endeavor. In combination with observations of surface motion and basal water pressure, this method is ideally suited to localize and quantify frictional and fracture processes which occur during periods of rapidly changing sub-glacial water pressure with consequent stress redistribution at the contact interface between ice and bed. Here we present the results of the first one-year-long glacier seismic monitoring performed on an Alpine glacier to our knowledge. Together with records of surface motion and hydrological measurements, we examine whether seasonal changes can be captured by seismic recording. Experiments were carried out from June 2012 to July 2013 on Rhonegletscher (Valais, Switzerland), by means of 3 three-components seismometers settled close to the tongue in 2 meters boreholes. An additional array of eleven sensors installed at the ice surface was also maintained during September 2012, in order to achieve more accurate icequakes locations. A high seismic emission is observed on Rhonegletscher, with icequakes located close to the surface or in the vicinity of the bedrock. The temporal distribution of seismic activity is shown to nicely reflect the seasonal evolution of the glacier hydrology, with a dramatic seismic release in early spring. During summer, released seismic activity is generally driven by diurnal ice/snow melting cycle. In winter, snow-cover conditions are associated with a reduced seismic release, with nevertheless some unexpected activity possibly related to snow-pack metamorphism. Based on icequake locations derived from data recorded in September, we discuss

  9. 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

  10. 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

  11. 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

  12. Method for inverting reflection trace data from 3-D and 4-D seismic surveys and identifying subsurface fluid and pathways in and among hydrocarbon reservoirs based on impedance models

    DOEpatents

    He, Wei; Anderson, Roger N.

    1998-01-01

    A method is disclosed for inverting 3-D seismic reflection data obtained from seismic surveys to derive impedance models for a subsurface region, and for inversion of multiple 3-D seismic surveys (i.e., 4-D seismic surveys) of the same subsurface volume, separated in time to allow for dynamic fluid migration, such that small scale structure and regions of fluid and dynamic fluid flow within the subsurface volume being studied can be identified. The method allows for the mapping and quantification of available hydrocarbons within a reservoir and is thus useful for hydrocarbon prospecting and reservoir management. An iterative seismic inversion scheme constrained by actual well log data which uses a time/depth dependent seismic source function is employed to derive impedance models from 3-D and 4-D seismic datasets. The impedance values can be region grown to better isolate the low impedance hydrocarbon bearing regions. Impedance data derived from multiple 3-D seismic surveys of the same volume can be compared to identify regions of dynamic evolution and bypassed pay. Effective Oil Saturation or net oil thickness can also be derived from the impedance data and used for quantitative assessment of prospective drilling targets and reservoir management.

  13. Method for inverting reflection trace data from 3-D and 4-D seismic surveys and identifying subsurface fluid and pathways in and among hydrocarbon reservoirs based on impedance models

    DOEpatents

    He, W.; Anderson, R.N.

    1998-08-25

    A method is disclosed for inverting 3-D seismic reflection data obtained from seismic surveys to derive impedance models for a subsurface region, and for inversion of multiple 3-D seismic surveys (i.e., 4-D seismic surveys) of the same subsurface volume, separated in time to allow for dynamic fluid migration, such that small scale structure and regions of fluid and dynamic fluid flow within the subsurface volume being studied can be identified. The method allows for the mapping and quantification of available hydrocarbons within a reservoir and is thus useful for hydrocarbon prospecting and reservoir management. An iterative seismic inversion scheme constrained by actual well log data which uses a time/depth dependent seismic source function is employed to derive impedance models from 3-D and 4-D seismic datasets. The impedance values can be region grown to better isolate the low impedance hydrocarbon bearing regions. Impedance data derived from multiple 3-D seismic surveys of the same volume can be compared to identify regions of dynamic evolution and bypassed pay. Effective Oil Saturation or net oil thickness can also be derived from the impedance data and used for quantitative assessment of prospective drilling targets and reservoir management. 20 figs.

  14. 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

  15. 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

  16. Using Vertical electrical sounding survey and refraction seismic survey for determining the geological layers depths, the structural features and assessment groundwater in Aqaba area in South Jordan.

    NASA Astrophysics Data System (ADS)

    Akawwi, Emad; Alzoubi, Abdallah; Ben Abraham, Zvi; Rahamn Abo Alades, Abdel; Alrzouq, Rami; Tiber, Gidon; Neimi, Tina

    2010-05-01

    The study area is the Aqaba region (Southern wadi Araba basin). Aqaba region area located at 87900 and 89000 North and 147000 and 158000 East (Palestine grid). Tectonically Aqaba area lies within the tectonic plate boundary along the Arabian and African plate slide. This plate boundary comprises numerous and shot fault segments. The main aims of this study are to assessing the groundwater potential and its quality, to explain the subsurface geological conditions and support the ongoing geological, environmental and hydrogeological studies. Therefore, it was anticipated that the results of the geophysical surveying will give many different important parameters as The subsurface geological features, thicknesses of the different lithological units, depth to the bed rocks and depth to the water table. The groundwater can apply an important role in ensuring sustainable water supply in the area. This study was carried out in order to assess groundwater condition, geological layers thicknesses and structural features in Aqaba area by using vertical electrical sounding (VES) surveys and refraction seismic techniques. There are three geoelectrical cross section were carried out at different sites by using the Schlumberger array. The first cross section indicated three layers of different resistivity. The second cross section indicated four layers of different resistivity. The third geoelectrical cross sections indicated three layers. The refraction seismic method also has been conducted in the same area as VES. About 12 refraction seismic profiles have been carried out in the study area. The length of the first profile was 745 m at the direction N-S. This profile indicated two different layers with a different velocities. The length of the second profile was 1320 m with E-W direction. This profile indicated two different layers. The length of the third profile was about 515 m with a direction SE-NW. It recognized two different layers with a different velocities. The fourth

  17. Archive of Digital Boomer Seismic Reflection Data Collected During USGS Field Activity 96LCA04 in Lakes Mabel and Starr, Central Florida, August 1996

    USGS Publications Warehouse

    Harrison, Arnell S.; Dadisman, Shawn V.; Swancar, Amy; Tihansky, Ann B.; Flocks, James G.; Wiese, Dana S.

    2008-01-01

    In August of 1996, the U.S. Geological Survey conducted geophysical surveys of Lakes Mabel and Starr, central Florida, as part of the Central Highlands Lakes project, which is part of a larger USGS Lakes and Coastal Aquifers (LCA) study. This report serves as an archive of unprocessed digital boomer seismic reflection data, trackline maps, navigation files, Geographic Information System (GIS) files, observer's logbook; and formal Federal Geographic Data Committee (FGDC) metadata. Filtered and gained (a relative increase in signal amplitude) digital images of the seismic profiles are also provided. Refer to the Acronyms page for expansions of acronyms and abbreviations used in this report. For detailed information about the hydrologic setting of Lake Starr and the interpretation of some of these seismic reflection data, see Swancar and others (2000) at http://fl.water.usgs.gov/publications/Abstracts/wri00_4030_swancar.html. The archived trace data are in standard Society of Exploration Geophysicists (SEG) SEG-Y format (Barry and others, 1975) and may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU). Example SU processing scripts and USGS software for viewing the SEG-Y files (Zihlman, 1992) are also provided. The USGS Florida Integrated Science Center (FISC) - St. Petersburg assigns a unique identifier to each cruise or field activity. For example, 96LCA04 tells us the data were collected in 1996 for the Lakes and Coastal Aquifers (LCA) study and the data were collected during the fourth field activity for that project in that calendar year. Refer to http://walrus.wr.usgs.gov/infobank/programs/html/definition/activity.html for a detailed description of the method used to assign the field activity ID. The boomer plate is an acoustic energy source that consists of capacitors charged to a high voltage and discharged through a transducer in the water. The transducer is towed on a sled floating on the water surface and when

  18. Seismic monitoring of torrential and fluvial processes

    NASA Astrophysics Data System (ADS)

    Burtin, Arnaud; Hovius, Niels; Turowski, Jens M.

    2016-04-01

    In seismology, the signal is usually analysed for earthquake data, but earthquakes represent less than 1 % of continuous recording. The remaining data are considered as seismic noise and were for a long time ignored. Over the past decades, the analysis of seismic noise has constantly increased in popularity, and this has led to the development of new approaches and applications in geophysics. The study of continuous seismic records is now open to other disciplines, like geomorphology. The motion of mass at the Earth's surface generates seismic waves that are recorded by nearby seismometers and can be used to monitor mass transfer throughout the landscape. Surface processes vary in nature, mechanism, magnitude, space and time, and this variability can be observed in the seismic signals. This contribution gives an overview of the development and current opportunities for the seismic monitoring of geomorphic processes. We first describe the common principles of seismic signal monitoring and introduce time-frequency analysis for the purpose of identification and differentiation of surface processes. Second, we present techniques to detect, locate and quantify geomorphic events. Third, we review the diverse layout of seismic arrays and highlight their advantages and limitations for specific processes, like slope or channel activity. Finally, we illustrate all these characteristics with the analysis of seismic data acquired in a small debris-flow catchment where geomorphic events show interactions and feedbacks. Further developments must aim to fully understand the richness of the continuous seismic signals, to better quantify the geomorphic activity and to improve the performance of warning systems. Seismic monitoring may ultimately allow the continuous survey of erosion and transfer of sediments in the landscape on the scales of external forcing.

  19. Overdeepened glacigenic landforms in Lake Thun (Switzerland) revealed by a multichannel reflection seismic survey

    NASA Astrophysics Data System (ADS)

    Fabbri, Stefano; Herwegh, Marco; Schlunegger, Fritz; Hübscher, Christian; Weiss, Benedikt J.; Schmelzbach, Cédric; Horstmeyer, Heinrich; Buechi, Marius W.; Anselmetti, Flavio S.

    2016-04-01

    Recently acquired high-resolution multibeam bathymetry, in combination with a 2D multichannel reflection seismic campaign on perialpine Lake Thun (Switzerland) reveals new insights into the diverse geometry of the lake basin and a so far unknown subaquatic moraine crest with unprecedented clarity. These new data will improve our comprehension concerning the retreat phases of the Aare glacier, the morphology of its proximal deposits and the facies architecture of the subglacial units. The overdeepened basin of Lake Thun was formed by a combination of tectonically predefined weak zones and glacial erosion during the last glacial periods. The new data indicate that below the outermost edge of a morphologically distinct platform in the south eastern part of the lake basin, a ridge structure marked by strong reflection amplitudes occurs. This structure is interpreted as a subaquatic terminal moraine crest, most likely created by a slightly advancing or stagnant grounded Aare glacier during its major retreating phase. The terminal moraine smoothly transforms downstream into well distinguishable foresets with internally recognisable layering, which dip steeply towards the deepest part of the basin, eventually transforming into bottomsets. This depositional sequence formed by the fore- and bottomsets represents ˜50% of the overall sediment volume that fills the basin and was deposited while the glacier was stagnant, interpreted to represent a rather short period of time of a few hundreds of years. This sequence is overlain by lacustrine deposits formed by late-glacial and Holocene laminated muds comprising intercalated turbidites (Wirth et al. 2011). Little is known about the exact timing and behaviour of retreating glaciers between their recessional phase from the Alpine foreland to the deglaciation of the inner-Alpine ice cap, mostly due to the lack of well-developed moraines that indicate glacial stabilization or slight readvance. Findings from pollen analyses by

  20. Improving active seismic isolation in aLIGO using a ground rotation sensor

    NASA Astrophysics Data System (ADS)

    Venkateswara, Krishna; Hagedorn, Charles; Ross, Michael; Gundlach, Jens

    2016-03-01

    The active seismic isolation in Advanced LIGO achieves a factor of 10 -104 isolation from ground displacement in the frequency range from 0.1-10 Hz enabling stable low noise interferometer operation. It uses seismometers on the ground and the optics platform in feedback loops to reduce the transmission of ground motion to the platform. However, due to the inability of a seismometer to distinguish between horizontal acceleration and rotation (coupling through gravity), wind-induced tilt limits the performance of the active isolation in the 10-500 mHz frequency range, thereby reducing the duty-cycle of the detectors. We describe a ground rotation sensor, consisting of a low frequency beam-balance and an autocollimator readout with better than 0.4 nrad/rt(Hz) sensitivity above 10 mHz, which can be used to subtract tilt-noise from a horizontal seismometer, thus improving the active seismic isolation system. This work was supported by NSF Grant: 1306613.

  1. Reflection seismic mapping of shallow quick-clay landslides in Sweden - new insights from shear-wave surveying

    NASA Astrophysics Data System (ADS)

    Polom, U.; Krawczyk, C. M.; Malehmir, A.; Bastani, M.

    2012-04-01

    As part of a joint project studying clay-related landslides in Nordic countries, we successfully tested the use of shear wave reflection seismics to survey shallow structures that are known to be related to quick-clay landslide processes. Co-sponsored via the Society of Exploration Geophysicists (SEG) program 'Geoscientists Without Borders (GWB)', several international groups apply a suite of applied geophysical and geotechnical methods to understand structural and physical conditions and the conditioning of this type of liquefaction. For this purpose, three 2D profiles were recorded in Frastadt, southern Sweden, above the main slide plane area. Using a 120 m long streamer of 120 SH-geophones at 1 m spacing, and the ELVIS micro-vibrator as source, shear-wave data of very high quality were gathered. The longest profile along a paved road shows clear internal structuring of the up to 50 m thick marine sediments as well as strong undulations of top basement underneath. The sedimentary shear wave velocities suggest extremely low values of 100-120 m/s, which geotechnically prohibits building areas. In addition, test measurements on a stubble field showed the first time that the suppression of Love waves is not only restricted to paved surfaces and may also be achieved if reflection contrasts and low dispersion allow a suitable data processing. This opens new possibilities for a wide range of applications and specialized equipment adaptions.

  2. Gpr and Seismic Based Non-Destructive Geophysical Survey for Reinforcement of Historical Fire Tower of Sopron-Hungary

    NASA Astrophysics Data System (ADS)

    Kanli, A. I.; Taller, G.; Nagy, P.; Tildy, P.; Pronay, Z.; Toros, E.

    2013-12-01

    The Fire-Tower which is located in the main square at the hearth of Sopron is the symbol of the city. The museum of Sopron exists in the Storno-house west from the tower. The new city hall stands next to the tower to the east. Funds are from the roman age while the tower was first mentioned in writing in 1409. In 1676, it was burned down to the ground, but re-constructed. In 1894, the old City Hall was deconstucted, but the tower became unstable. István Kiss and Frigyes Schulek saved it by the walling up of the gate. In the year 1928, the scuptures of the main gate which symbolizes the fidelity of the town was sculpted by Zsigmond Kisfaludy Strobl. The old building was deconstructed from its west side, a new concrate museum was built in 1970. After years, important renovation and reinforcement studies had to be needed. For this aim, during the renovation and reinforcement studies, GPR and Seismic based non-destructive geophysical surveys were carried out before and after cement injection to observe the changes of the wall conditions of the historical tower located in Sopron-Hungary for understanding the success of the reinforcements studies. In the GPR survey, 400 MHz and 900 MHz antennas were used. The space between each profiles were taken as 0.5 m for 400 MHz and 0.25m for 900 MHz respectively. After the injection process, reflections from the fractured and porous zones were weakened imaged clearly by GPR data and significant rise of the p-wave velocities were observed.

  3. Thermal anomalies in fumaroles at Vulcano island (Italy) and their relationship with seismic activity and stress-induced permeability changes

    NASA Astrophysics Data System (ADS)

    Madonia, Paolo; Cusano, Paola; Diliberto, Iole Serena; Cangemi, Marianna

    2016-04-01

    Fumarole thermal monitoring is a useful tool in the evaluation of volcanic activity, since temperatures strongly relate to the upward flux of magmatic volatiles. Once depurated from meteorological noise, their variations can reflect permeability changes due to crustal stress dynamics eventually associated to seismic activity. In this work, we discuss a fumarole temperature record acquired in the period September 2009 - May 2012 at Vulcano island (Italy), during which changes of volcanic state, local seismic activity and teleseisms occurred. Apart from positive thermal anomalies driven by increments in volcanic activity, we observed 3 episodes at least of concurrence between tectonic earthquakes and fumarole temperature increments, with particular reference to the local August 16th, 2010 Lipari earthquake, the March 11th, 2011 Sendai-Honshu (Japan) earthquake and a seismic swarm occurred along the Tindari-Letojanni fault in July-August 2011. We interpreted the seismic-related anomalies as "crustal fluid transients", i.e. signals of volcanogenic vapour flow variations induced by stress-induced permeability changes. From this perspective fumarolic activity can be considered as a tracer of geodynamic instability but, since seismic and volcanic phenomena are in mutual cause-effect relationships, a multidisciplinary observation system is mandatory for correctly addressing thermal data interpretation.

  4. 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

  5. Finding Large Aperture Fractures in Geothermal Resource Areas Using a Three-Component Long-Offset Surface Seismic Survey, PSInSAR and Kinematic Structural Analysis

    SciTech Connect

    Teplow, William J.; Warren, Ian

    2015-08-12

    The DOE cost-share program applied innovative and cutting edge seismic surveying and processing, permanent scatter interferometry-synthetic aperture radar (PSInSAR) and structural kinematics to the exploration problem of locating and mapping largeaperture fractures (LAFs) for the purpose of targeting geothermal production wells. The San Emidio geothermal resource area, which is under lease to USG, contains production wells that have encountered and currently produce from LAFs in the southern half of the resource area (Figure 2). The USG lease block, incorporating the northern extension of the San Emidio geothermal resource, extends 3 miles north of the operating wellfield. The northern lease block was known to contain shallow thermal waters but was previously unexplored by deep drilling. Results of the Phase 1 exploration program are described in detail in the Phase 1 Final Report (Teplow et al., 2011). The DOE cost shared program was completed as planned on September 30, 2014. This report summarizes results from all of Phase 1 and 2 activities.

  6. Shallow sediment and upper crustal structure beneath the Salton Sea as imaged by active source marine seismic refraction in conjunction with the Salton Seismic Imaging Project

    NASA Astrophysics Data System (ADS)

    Kell, A. M.; Sahakian, V. J.; Harding, A. J.; Kent, G.; Driscoll, N. W.

    2012-12-01

    In the spring of 2011 we expanded a campaign of marine seismic reflection efforts in the Salton Sea in conjunction with the Salton Seismic Imaging Project (SSIP) to collect active-source marine refraction data using Ocean Bottom Seismometers (OBSs) and a marine airgun. The Salton Trough presents an opportunity to study rifting processes similar to those seen in the Gulf of California, as well as the seismic hazards associated with the southern terminus of the San Andreas Fault (SAF). An areal array, comprised of 78 OBS deployments, was focused in the southern part of the sea but also included a line parallel to the San Andreas Fault (SAF) , line 1, extending then length of the sea, and a line perpendicular to the SAF, crossing the northern basin, line 7. These lines are collinear with high-resolution reflection profiles and existing chirp profiles. The OBS array was concentrated in the southern Salton Sea to investigate the pull-apart deformation reported by Brothers et al. (2009). Using the methods of Van Avendonk (2004) we seek to constrain upper crustal velocities in this region by travel-time tomography. Beginning with P-wave arrival times we trace the ray paths through the model space and invert for seismic velocities. By iterating from the forward picking to the inversion, we reduce the chi-squared error to produce a 2D depth profile of the seismic velocities while maintaining a stable model. Line 1 uses 38 OBSs and 470 shots from a 210 cu. in. airgun to model the upper 4 km beneath the Salton Sea. Velocities vary from 1.5 km/s in the upper 1 km to an apparent 4 km deep basement velocity of 5.5 km/s. Velocity variations with depth agree with major boundaries in the co-linear seismic reflection profiles and the divergence toward the south/fault structure is also captured in these early models. Preliminary results for line 7 show similarly varying velocities - 1.5 to 3 km/s in the upper 2 kilometers of the crust, to slightly over 4 km/s at 4 km depth. Further

  7. Structure of the active rift zone and margins of the northern Imperial Valley from Salton Seismic Imaging Project (SSIP) data

    NASA Astrophysics Data System (ADS)

    Livers, A.; Han, L.; Delph, J. R.; White-Gaynor, A. L.; Petit, R.; Hole, J. A.; Stock, J. M.; Fuis, G. S.

    2012-12-01

    First-arrival refraction data were used to create a seismic velocity model of the upper crust across the actively rifting northern Imperial Valley and its margins. The densely sampled seismic refraction data were acquired by the Salton Seismic Imaging Project (SSIP) , which is investigating rift processes in the northern-most rift segment of the Gulf of California extensional province and earthquake hazards at the southern end of the San Andreas Fault system. A 95-km long seismic line was acquired across the northern Imperial Valley, through the Salton Sea geothermal field, parallel to the five Salton Butte volcanoes and perpendicular to the Brawley Seismic Zone and major strike-slip faults. Nineteen explosive shots were recorded with 100 m seismometer spacing across the valley and with 300-500 m spacing into the adjacent ranges. First-arrival travel times were picked from shot gathers along this line and a seismic velocity model was produced using tomographic inversion. Sedimentary basement and seismic basement in the valley are interpreted to be sediment metamorphosed by the very high heat flow. The velocity model shows that this basement to the west of the Brawley Seismic Zone is at ~4-km depth. The basement shallows to ~2-km depth in the active geothermal field and Salton Buttes volcanic field which locally coincide with the Brawley Seismic Zone. At the eastern edge of the geothermal field, the basement drops off again to ~3.5-km depth. The eastern edge of the valley appears to be fault bounded by the along-strike extension of the Sand Hills Fault, an inactive strike-slip fault. The seismic velocities to the east of the fault correspond to metamorphic rock of the Chocolate Mountains, different from the metamorphosed basement in the valley. The western edge of the valley appears to be fault bounded by the active Superstition Hills Fault. To the west of the valley, >4-km deep valley basement extends to the active Superstition Hills Fault. Basement then shallows

  8. Overview and early highlights of the TAIGER project marine, active-source seismic program (Invited)

    NASA Astrophysics Data System (ADS)

    McIntosh, K. D.; van Avendonk, H. J.; Liu, C.; Hsu, S.; Lee, C.; Wang, T. K.; Wu, F. T.

    2009-12-01

    The marine active-source portion of the TAIGER (TAIwan GEodynamic Research) project took place during April-July 2009 using the R/V Marcus Langseth with support from a variety of Taiwanese ships used to deploy and recover ocean bottom seismographs (OBSs). Due to Taiwanese shiptime (Langseth) contribution, the active-source program was doubled from our original proposal. Over the course of three, ~month-long cruises, the Langseth produced seismic source points along >13,000 km of track line. This includes > 11,000 km of deep-penetration multichannel seismic reflection data (MCS), shots to ~269 OBS stations (Taiwanese and U.S.), and shots to ~280 temporary land seismic stations across Taiwan. During this comprehensive project the Langseth circled Taiwan and ventured far to the south and east. TAIGER data cover the passive margin SW of Taiwan to provide a “pre-collision” structural configuration of the subducting plate, while TAIGER MCS and OBS data acquired on transects south of Taiwan will provide an idea of the “pre-collision” structural configuration of the Manila trench subduction zone. We will compare these areas to the evolving crustal structure of the Taiwan collision, which will be analyzed with onshore/offshore seismic data recorded during TAIGER legs 1 and 2. These TAIGER crustal transects will elucidate crucial components and stages of the southwestward advancing collision. We were able to process all the MCS data during the acquisition cruises to preliminary stack and FK migration. In much of the area SW of Taiwan we observe deep reflections, likely marking Moho. Surprisingly, even at distances > 250 km south of the shelf edge, apparent basement crustal thickness is frequently 3+ s (two-way travel time) or about 9-11 km. We also obtained exciting results across both the Manila/Luzon and Ryukyu arc-trench systems. These subduction systems are primarily characterized by ample sediment supply and relatively fast convergence leading to young, rapidly

  9. 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

  10. Possibilities for Observations of Electromagnetic Perturbations Related to Seismic Activity with Swarm Satellites

    NASA Astrophysics Data System (ADS)

    De Santis, A.; Mandea, M.; Balasis, G.

    2014-12-01

    It has been suggested that intense seismic activity might generate upward electromagnetic (EM) perturbations that can be detected by ground-based and low altitude spaceborne measurements. For instance, DEMETER satellite (2004-2010) very low frequency (VLF) wave observations pointed out a statistically significant decrease of the measured ionospheric wave intensity a few hours before large shallow earthquakes (EQs). This result would confirm the existence of a lithosphere-atmosphere-ionosphere coupling before the occurrence of an impending significant EQ. Swarm offers a great opportunity to study EM perturbations possibly related to seismic activity because it is a multi-satellite low Earth orbit (LEO) mission with a unique space-time configuration able to measure both electric and magnetic fields at various altitudes in the topside ionosphere. Here, we are analyzing, using various signal processing techniques, Swarm measurements shortly before and after large shallow EQs (magnitude above 7 and depth < 40 km) that occurred in the first year of the mission and report on the initial results of our analysis.

  11. Seismic protection of frame structures via semi-active control: modeling and implementation issues

    NASA Astrophysics Data System (ADS)

    Gattulli, Vincenzo; Lepidi, Marco; Potenza, Francesco

    2009-12-01

    Theoretical and practical issues concerning the multi-faceted task of mitigating the latero-torsional seismic response of a prototypal frame structure with asymmetric mass distribution are approached. Chevron braces with embedded magnetorheological dampers acting on the interstory drift are used to ensure additional energy dissipation. The semi-active control strategy employed to govern the modification of the damper characteristics via feedback is based on the selection of optimal forces according to a H2/LQG criterion, with respect to which the actual forces are regulated by a clipped-optimal logic. A dynamic observer is used to estimate the state through a non-collocated placement of the acceleration sensors. Several aspects to be addressed throughout the complex process including the design, modelization, and implementation phases of semi-active protection systems are discussed. Finally, experimental results obtained to mitigate the motion induced by ground excitation in a large-scale laboratory prototype, simulating the seismic response of a two-story building, are summarized.

  12. Quantification of depositional changes and paleo-seismic activities from laminated sediments using outcrop data

    NASA Astrophysics Data System (ADS)

    Weidlich, O.; Bernecker, M.

    2004-04-01

    Measurements of laminations from marine and limnic sediments are commonly a time-consuming procedure. However, the resulting quantitative proxies are of importance for the interpretation of both, climate changes and paleo-seismic activities. Digital image analysis accelerates the generation and interpretation of large data sets from laminated sediments based on contrasting grey values of dark and light laminae. Statistical transformation and correlation of the grey value signals reflect high frequency cycles due to changing mean laminae thicknesses, and thus provide data monitoring climate change. Perturbations (e.g., slumping structures, seismites, and tsunamites) of the commonly continuous laminae record seismic activities and obtain proxies for paleo-earthquake frequency. Using outcrop data from (i) the Pleistocene Lisan Formation of Jordan (Dead Sea Basin) and (ii) the Carboniferous-Permian Copacabana Formation of Bolivia (Lake Titicaca), we present a two-step approach to gain high-resolution time series based on field data for both purposes from unconsolidated and lithified outcrops. Step 1 concerns the construction of a continuous digital phototransect and step 2 covers the creation of a grey density curve based on digital photos along a line transect using image analysis. The applied automated image analysis technique provides a continuous digital record of the studied sections and, therefore, serves as useful tool for the evaluation of further proxy data. Analysing the obtained grey signal of the light and dark laminae of varves using phototransects, we discuss the potential and limitations of the proposed technique.

  13. Co-seismic displacement of the 11 March 2011 Tohoku-Oki Earthquake detected by differential multi-narrow beam bathymetric survey

    NASA Astrophysics Data System (ADS)

    Fujiwara, T.; Kodaira, S.; No, T.; Kaiho, Y.; Fujie, G.; Nakamura, Y.; Takahashi, T.; Yamamoto, Y.; Takahashi, N.; Kaneda, Y.

    2011-12-01

    The large tsunami that followed the 2011 Tohoku-Oki Earthquake is believed to have been caused by a fault rupture extending to a shallow part of the subduction zone at the Japan Trench. This is indicated by the results obtained by primary seismic and geodetic inversion procedures; however, an accurate up-dip limit of the co-seismic displacement has not yet been determined. In order to estimate the co-seismic displacement around the trench axis, which is a key to understand the tsunami generation, we carried out post-earthquake, multi-channel seismic reflection and multi-narrow beam bathymetric surveys [Kodaira et al.; Nakamura et al., this AGU meeting] along the survey lines obtained before the earthquake [e.g. Tsuru et al., 2002; Ito et al., 2005]. We analyzed the difference in bathymetry before and after the earthquake, and the results revealed that in a large slip area (~38°N), the seafloor on the landward side of the trench moved by 50 m horizontally to the SE to ESE direction and 10 m upward. Our results show the co-seismic displacement increasing toward the trench axis [for landward side results, refer to Kido et al., 2011; Sato et al., 2011], and the displacement reaches immediately at the trench axis, and also topographic changes were probably caused by land sliding at the axial seafloor. This observation suggests that the plate-coupled zone between earthquakes does extend at the shallowest part of the subduction zone, which was believed to be a stable sliding region. The landward slope near the Japan Trench has steep angle (~5°). Therefore the resultant large horizontal displacement effectively lifted the steep slope area in addition to the actual uplift. Together, these uplifts have caused the massive tsunami.

  14. 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.

  15. Borehole-explosion and air-gun data acquired in the 2011 Salton Seismic Imaging Project (SSIP), southern California: description of the survey

    USGS Publications Warehouse

    Rose, Elizabeth J.; Fuis, Gary S.; Stock, Joann M.; Hole, John A.; Kell, Annie M.; Kent, Graham; Driscoll, Neal W.; Goldman, Mark; Reusch, Angela M.; Han, Liang; Sickler, Robert R.; Catchings, Rufus D.; Rymer, Michael J.; Criley, Coyn J.; Scheirer, Daniel S.; Skinner, Steven M.; Slayday-Criley, Coye J.; Murphy, Janice M.; Jensen, Edward G.; McClearn, Robert; Ferguson, Alex J.; Butcher, Lesley A.; Gardner, Max A.; Emmons, Iain; Loughran, Caleb L.; Svitek, Joseph R.; Bastien, Patrick C.; Cotton, Joseph A.; Croker, David S.; Harding, Alistair J.; Babcock, Jeffrey M.; Harder, Steven H.; Rosa, Carla M.

    2013-01-01

    The Imperial and Coachella Valleys are being formed by active plate-tectonic processes. From the Imperial Valley southward into the Gulf of California, plate motions are rifting the continent apart. In the Coachella Valley, the plates are sliding past one another along the San Andreas and related faults (fig. 1). These processes build the stunning landscapes of the region, but also produce damaging earthquakes. Rupture of the southern section of the San Andreas Fault (SAF), from the Coachella Valley to the Mojave Desert, is believed to be the greatest natural hazard that California will face in the near future. With an estimated magnitude between 7.2 and 8.1, such an event would result in violent shaking, loss of life, and disruption of infrastructure (freeways, aqueducts, power, petroleum, and communication lines) that might bring much of southern California to a standstill. As part of the nation’s efforts to avert a catastrophe of this magnitude, a number of projects have been undertaken to more fully understand and mitigate the effects of such an event. The Salton Seismic Imaging Project (SSIP), funded jointly by the National Science Foundation (NSF) and the U.S. Geological Survey (USGS), seeks to understand, through seismic imaging, the structure of the Earth surrounding the SAF, including the sedimentary basins on which cities are built. The principal investigators (PIs) of this collaborative project represent the USGS, Virginia Polytechnic Institute and State University (Virginia Tech), California Institute of Technology (Caltech), Scripps Institution of Oceanography (Scripps), University of Nevada, Reno (UNR), and Stanford University. SSIP will create images of underground structure and sediments in the Imperial and Coachella Valleys and adjacent mountain ranges to investigate the earthquake hazards posed to cities in this area. Importantly, the images will help determine the underground geometry of the SAF, how deep the sediments are, and how fast

  16. Updated Colombian Seismic Hazard Map

    NASA Astrophysics Data System (ADS)

    Eraso, J.; Arcila, M.; Romero, J.; Dimate, C.; Bermúdez, M. L.; Alvarado, C.

    2013-05-01

    The Colombian seismic hazard map used by the National Building Code (NSR-98) in effect until 2009 was developed in 1996. Since then, the National Seismological Network of Colombia has improved in both coverage and technology providing fifteen years of additional seismic records. These improvements have allowed a better understanding of the regional geology and tectonics which in addition to the seismic activity in Colombia with destructive effects has motivated the interest and the need to develop a new seismic hazard assessment in this country. Taking advantage of new instrumental information sources such as new broad band stations of the National Seismological Network, new historical seismicity data, standardized global databases availability, and in general, of advances in models and techniques, a new Colombian seismic hazard map was developed. A PSHA model was applied. The use of the PSHA model is because it incorporates the effects of all seismic sources that may affect a particular site solving the uncertainties caused by the parameters and assumptions defined in this kind of studies. First, the seismic sources geometry and a complete and homogeneous seismic catalog were defined; the parameters of seismic rate of each one of the seismic sources occurrence were calculated establishing a national seismotectonic model. Several of attenuation-distance relationships were selected depending on the type of seismicity considered. The seismic hazard was estimated using the CRISIS2007 software created by the Engineering Institute of the Universidad Nacional Autónoma de México -UNAM (National Autonomous University of Mexico). A uniformly spaced grid each 0.1° was used to calculate the peak ground acceleration (PGA) and response spectral values at 0.1, 0.2, 0.3, 0.5, 0.75, 1, 1.5, 2, 2.5 and 3.0 seconds with return periods of 75, 225, 475, 975 and 2475 years. For each site, a uniform hazard spectrum and exceedance rate curves were calculated. With the results, it is

  17. Seismicity on the western Greenland Ice Sheet: Surface fracture in the vicinity of active moulins

    DOE PAGES

    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 seismicitymore » 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.« less

  18. 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.

  19. Geodynamics of the Dead Sea Fault: Do active faulting and past earthquakes determine the seismic gaps?

    NASA Astrophysics Data System (ADS)

    Meghraoui, Mustapha

    2014-05-01

    The ~1000-km-long North-South trending Dead Sea transform fault (DSF) presents structural discontinuities and includes segments that experienced large earthquakes (Mw>7) in historical times. The Wadi Araba and Jordan Valley, the Lebanese restraining bend, the Missyaf and Ghab fault segments in Syria and the Ziyaret Fault segment in Turkey display geometrical complexities made of step overs, restraining and releasing bends that may constitute major obstacles to earthquake rupture propagation. Using active tectonics, GPS measurements and paleoseismology we investigate the kinematics and long-term/short term slip rates along the DSF. Tectonic geomorphology with paleoseismic trenching and archeoseismic investigations indicate repeated faulting events and left-lateral slip rate ranging from 4 mm/yr in the southern fault section to 6 mm/yr in the northern fault section. Except for the northernmost DSF section, these estimates of fault slip rate are consistent with GPS measurements that show 4 to 5 mm/yr deformation rate across the plate boundary. However, recent GPS results showing ~2.5 mm/yr velocity rate of the northern DSF appears to be quite different than the ~6 mm/yr paleoseismic slip rate. The kinematic modeling that combines GPS and seismotectonic results implies a complex geodynamic pattern where the DSF transforms the Cyprus arc subduction zone into transpressive tectonics on the East Anatolian fault. The timing of past earthquake ruptures shows the occurrence of seismic sequences and a southward migration of large earthquakes, with the existence of major seismic gaps along strike. In this paper, we discuss the role of the DSF in the regional geodynamics and its implication on the identification of seismic gaps.

  20. Short-term disturbance by a commercial two-dimensional seismic survey does not lead to long-term displacement of harbour porpoises.

    PubMed

    Thompson, Paul M; Brookes, Kate L; Graham, Isla M; Barton, Tim R; Needham, Keith; Bradbury, Gareth; Merchant, Nathan D

    2013-11-22

    Assessments of the impact of offshore energy developments are constrained because it is not known whether fine-scale behavioural responses to noise lead to broader-scale displacement of protected small cetaceans. We used passive acoustic monitoring and digital aerial surveys to study changes in the occurrence of harbour porpoises across a 2000 km(2) study area during a commercial two-dimensional seismic survey in the North Sea. Acoustic and visual data provided evidence of group responses to airgun noise from the 470 cu inch array over ranges of 5-10 km, at received peak-to-peak sound pressure levels of 165-172 dB re 1 µPa and sound exposure levels (SELs) of 145-151 dB re 1 µPa(2) s(-1). However, animals were typically detected again at affected sites within a few hours, and the level of response declined through the 10 day survey. Overall, acoustic detections decreased significantly during the survey period in the impact area compared with a control area, but this effect was small in relation to natural variation. These results demonstrate that prolonged seismic survey noise did not lead to broader-scale displacement into suboptimal or higher-risk habitats, and suggest that impact assessments should focus on sublethal effects resulting from changes in foraging performance of animals within affected sites. PMID:24089338

  1. Short-term disturbance by a commercial two-dimensional seismic survey does not lead to long-term displacement of harbour porpoises

    PubMed Central

    Thompson, Paul M.; Brookes, Kate L.; Graham, Isla M.; Barton, Tim R.; Needham, Keith; Bradbury, Gareth; Merchant, Nathan D.

    2013-01-01

    Assessments of the impact of offshore energy developments are constrained because it is not known whether fine-scale behavioural responses to noise lead to broader-scale displacement of protected small cetaceans. We used passive acoustic monitoring and digital aerial surveys to study changes in the occurrence of harbour porpoises across a 2000 km2 study area during a commercial two-dimensional seismic survey in the North Sea. Acoustic and visual data provided evidence of group responses to airgun noise from the 470 cu inch array over ranges of 5–10 km, at received peak-to-peak sound pressure levels of 165–172 dB re 1 µPa and sound exposure levels (SELs) of 145–151 dB re 1 µPa2 s−1. However, animals were typically detected again at affected sites within a few hours, and the level of response declined through the 10 day survey. Overall, acoustic detections decreased significantly during the survey period in the impact area compared with a control area, but this effect was small in relation to natural variation. These results demonstrate that prolonged seismic survey noise did not lead to broader-scale displacement into suboptimal or higher-risk habitats, and suggest that impact assessments should focus on sublethal effects resulting from changes in foraging performance of animals within affected sites. PMID:24089338

  2. United States National Seismic Hazard Maps

    USGS Publications Warehouse

    Petersen, M.D.; ,

    2008-01-01

    The U.S. Geological Survey?s maps of earthquake shaking hazards provide information essential to creating and updating the seismic design provisions of building codes and insurance rates used in the United States. Periodic revisions of these maps incorporate the results of new research. Buildings, bridges, highways, and utilities built to meet modern seismic design provisions are better able to withstand earthquakes, not only saving lives but also enabling critical activities to continue with less disruption. These maps can also help people assess the hazard to their homes or places of work and can also inform insurance rates.

  3. [Correlation between the microbiological (S. aureus) and seismic activities with regard to the sun-earth interactions and neutron flux generation].

    PubMed

    Shestopalov, I P; Rogozhin, Iu A

    2005-01-01

    The study searched for interactions between the solar activity, seismic energy of the Earth and microbiological processes in the period from 1969 to 1997. Microbiological processes were found dependent on as the solar, so intraterrestrial (e.g. seismic) activity. The 11-year seismic on biological cycles on Earth display a positive inter-correlation and a negative one with the solar activity (sun-spots cycles). There is also correlation between the Earth's seismic energy and neutron fluxes generated at the times of earthquakes on our planet, and microbiological parameters.

  4. 1516 meters inside the earth - observations of seismic activity in the Dead Sea basin using borehole seismometer

    NASA Astrophysics Data System (ADS)

    Hofstetter, A.; Malin, P.; Shalev, E.; Ben-Avraham, Z.; Sagy, A.; Shalev, E.; Bariudin, V.

    2013-12-01

    Seismological measurements, conducted at great depths of several hundred of meters or even a few km, can provide useful information that one cannot get while conducting the measurements on the surface. We take advantage of Masada Deep borehole, an abandoned oil well, for the installation of a seismometer at a large depth of 1516 m. Seismological observations since 1983, using permanent and portable stations, revealed earthquake activity along the Dead Sea fault and its proximity, which is in good agreement with geological observations of young faulting age (> 30 KY). The operation of such station will enrich the seismological database with high quality data. The study has a few goals: 1) improving the detection capabilities of small earthquakes in the Dead Sea basin; 2) improving characterization of seismic activity in the Dead Sea basin; 3) better identification of seismic activity on the Dead Sea fault and observe earthquake nucleation and rupture processes in the near field; 4) extending the Gutenberg-Richter of frequency-magnitude relationship of earthquakes into smaller magnitudes below the threshold of the Israel Seismic Network catalog. The borehole seismometer was installed in Dec. 2012. We present seismic observations of small events conducted at a depth of 1516 m, many of them were not recorded by the Israel Seismic Network.

  5. A geophysical survey of active volcanism in the Central and Southern Andes

    NASA Astrophysics Data System (ADS)

    Jay, Jennifer Ann

    The subduction of the Nazca plate beneath the South American plate results in great earthquakes and active volcanism along the Andean margin. The Central Volcanic Zone (CVZ) between 15°S and 28°S and the Southern Volcanic Zone (SVZ) between 33°S and 46°S are separated by a zone of flat slab subduction and differ significantly in the manifestation of current volcanic activity. The CVZ has been considered less hazardous due to the few number of historical volcanic eruptions compared to the SVZ, yet it contains the largest mid-crustal magma body on Earth and erupted at least 10,000 km 3 of ignimbrite in the Late Miocene (10-1 Ma). In this dissertation, I use InSAR (interferometric synthetic aperture radar), thermal remote sensing, and seismology to investigate active volcanism in the Central and Southern Andes. InSAR and thermal remote sensing provide synoptic coverage along the volcanic arc, and seismic experiments allow further examination of selected volcanoes. I establish the first catalog of seismicity at Uturuncu volcano in Bolivia, where InSAR has observed continuous uplift since 1992, and find an unusually high seismicity rate for a Pleistocene volcano as well as swarm activity and triggered earthquakes. I then conduct a survey using satellite thermal infrared data to detect thermal hotspots related to volcanic activity throughout the CVZ and SVZ. I find hotspots at many volcanoes that had not previously been documented, with the CVZ containing more volcanoes with hotspots than the SVZ. One of the most thermally active volcanoes in the SVZ, Cordon Caulle volcano, experienced a large rhyodacitic eruption from 2011-2012. I use InSAR and petrology to model the pre-eruptive conditions at depth and co-eruptive processes and find that a large, long-lived crustal magma reservoir must be present beneath Cordon Caulle. Finally, I carry out an InSAR survey of volcanoes in southern Peru, completing a regional study of volcano deformation in the CVZ and allowing for a

  6. High-resolution seismic surveys in the Lake Balaton to image the stratigraphic architecture of Late Miocene basin fill beneath the lake

    NASA Astrophysics Data System (ADS)

    Visnovitz, Ferenc; Balázs, Attila; Horváth, Ferenc

    2013-04-01

    the Pannonian Lake. The shoreline clinoforms can offer evidence of climatically-driven cyclic lake level oscillations with maximum amplitude of 20 to 40 meters that are below the resolution of the hydrocarbon exploration land seismic. Periods of dryland conditions are suggested by occurrence of many mounded features which are interpreted as freshwater limestone banks. Morphology showed by seismic sections hint to volcanic features which can be corroborated by magnetic surveys and correlated with basaltic butes with known ages around the lake. This gives us the chance to date the time and rate of tectonic deformations, particularly determine the slip rate of the major left-lateral strike-slip fault parallel with the longitudinal axis (WSW-ENE) of the lake. This could be an essential information for the whole Pannonian basin as its neotectonic activity is controlled by this and other similar strike-slip faults.

  7. 75 FR 27563 - Agency Information Collection Activities: Voluntary Customer Survey

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-17

    ... SECURITY U.S. Customs and Border Protection Agency Information Collection Activities: Voluntary Customer... Voluntary Customer Survey. This request for comment is being made pursuant to the Paperwork Reduction Act of... following information collection: Title: Voluntary Customer Survey. OMB Number: Will be assigned...

  8. 77 FR 36566 - Agency Information Collection Activities: Voluntary Customer Survey

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-19

    ... SECURITY U.S. Customs and Border Protection Agency Information Collection Activities: Voluntary Customer... Voluntary Customer Survey. This request for comment is being made pursuant to the Paperwork Reduction Act of...: Voluntary Customer Survey. OMB Number: 1651-0135. Abstract: Customs and Border Protection (CBP) plans...

  9. 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

  10. Seismic Activity in Northern Izu-Bonin arc by Ocean Bottom Seismograph Observations

    NASA Astrophysics Data System (ADS)

    Obana, K.; Kamiya, S.; Kodaira, S.; Suetsugu, D.; Takahashi, N.; Sakaguchi, H.

    2006-12-01

    The Izu-Bonin Island arc is an oceanic island arc, where the Pacific plate subducts beneath the Philippine Sea plate. Suyehiro et al. (1996) found a thick andesitic middle crust with velocity of 6 km/s in northern Izu arc. Recent active seismic experiments in the Izu-Bonin arc show significant variations of the thickness of the middle crust along the volcanic front (Kodaira et al, 2005). The thickness of the middle crust shows an inverse correlation with the average P-wave crustal velocity and the SiO2 composition of the Quaternary volcanoes along the arc. Crustal evolution in the oceanic island arc is a process including magma evolution in the mantle wedge. To understand the nature of the crustal evolution in the oceanic island arc, we have to clarify structures in the mantle wedge along the arc in addition to the oceanic island arc crust. We conducted seismicity observations by a temporal ocean bottom seismograph (OBS) network in northern Izu-Bonin arc between Tori-shima and Hachijo-jima (30° to 34°N) to investigate structures of the oceanic island arc crust and the mantle wedge in northern Izu-Bonin arc by seismic tomography. The OBS network consists of 40 pop-up type OBSs with a three-component short-period seismometer. The OBSs were deployed in April 2006 and retrieved in July after about 80-day observations. The OBS data were processed with seismic data recorded at island stations on Hachijo-jima and Aoga-shima. These island stations are operated by National Research Institute for Earth Science and Disaster Prevention. From the preliminary results of the hypocenters, many earthquakes were located along the subducting Pacific plate. Along the volcanic front, shallow earthquake clusters were observed around Tori-shima and Sumisu-Jima islands. Another shallow earthquake cluster was observed near a seamount of echelon chains in the back-arc region of the Izu-Bonin arc. Earthquakes in the fore-arc region show strong attenuation at OBSs in the back-arc region

  11. 3D elastic full waveform inversion: case study from a land seismic survey

    NASA Astrophysics Data System (ADS)

    Kormann, Jean; Marti, David; Rodriguez, Juan-Esteban; Marzan, Ignacio; Ferrer, Miguel; Gutierrez, Natalia; Farres, Albert; Hanzich, Mauricio; de la Puente, Josep; Carbonell, Ramon

    2016-04-01

    Full Waveform Inversion (FWI) is one of the most advanced processing methods that is recently reaching a mature state after years of solving theoretical and technical issues such as the non-uniqueness of the solution and harnessing the huge computational power required by realistic scenarios. BSIT (Barcelona Subsurface Imaging Tools, www.bsc.es/bsit) includes a FWI algorithm that can tackle with very complex problems involving large datasets. We present here the application of this system to a 3D dataset acquired to constrain the shallow subsurface. This is where the wavefield is the most complicated, because most of the wavefield conversions takes place in the shallow region and also because the media is much more laterally heterogeneous. With this in mind, at least isotropic elastic approximation would be suitable as kernel engine for FWI. The current study explores the possibilities to apply elastic isotropic FWI using only the vertical component of the recorded seismograms. The survey covers an area of 500×500 m2, and consists in a receivers grid of 10 m×20 m combined with a 250 kg accelerated weight-drop as source on a displaced grid of 20 m×20 m. One of the main challenges in this case study is the costly 3D modeling that includes topography and substantial free surface effects. FWI is applied to a data subset (shooting lines 4 to 12), and is performed for 3 frequencies ranging from 15 to 25 Hz. The starting models are obtained from travel-time tomography and the all computation is run on 75 nodes of Mare Nostrum supercomputer during 3 days. The resulting models provide a higher resolution of the subsurface structures, and show a good correlation with the available borehole measurements. FWI allows to extend in a reliable way this 1D knowledge (borehole) to 3D.

  12. Dissolution of bedded rock salt: A seismic profile across the active eastern margin of the Hutchinson Salt Member, central Kansas

    USGS Publications Warehouse

    Anderson, N.L.; Hopkins, J.; Martinez, A.; Knapp, R.W.; Macfarlane, P.A.; Watney, W.L.; Black, R.

    1994-01-01

    Since late Tertiary, bedded rock salt of the Permian Hutchinson Salt Member has been dissolved more-or-less continuously along its active eastern margin in central Kansas as a result of sustained contact with unconfined, undersaturated groundwater. The associated westward migration of the eastern margin has resulted in surface subsidence and the contemporaneous sedimentation of predominantly valley-filling Quarternary alluvium. In places, these alluvium deposits extend more than 25 km to the east of the present-day edge of the main body of contiguous rock salt. The margin could have receded this distance during the past several million years. From an environmental perspective, the continued leaching of the Hutchinson Salt is a major concern. This predominantly natural dissolution occurs in a broad zone across the central part of the State and adversely affects groundwater and surface-water quality as nonpoint source pollution. Significant surface subsidence occurs as well. Most of these subsidence features have formed gradually; others developed in a more catastrophic manner. The latter in particular pose real threats to roadways, railways, and buried oil and gas pipelines. In an effort to further clarify the process of natural salt dissolution in central Kansas and with the long-term goal of mitigating the adverse environmental affects of such leaching, the Kansas Geological Survey acquired a 4-km seismic profile across the eastern margin of the Hutchinson Salt in the Punkin Center area of central Kansas. The interpretation of these seismic data (and supporting surficial and borehole geologic control) is consistent with several hypotheses regarding the process and mechanisms of dissolution. More specifically these data support the theses that: 1. (1) Dissolution along the active eastern margin of the Hutchinson Salt Member was initiated during late Tertiary. Leaching has resulted in the steady westward migration of the eastern margin, surface subsidence, and the

  13. Dissolution of bedded rock salt: A seismic profile across the active eastern margin of the Hutchinson Salt Member, central Kansas

    NASA Astrophysics Data System (ADS)

    Anderson, Neil L.; Hopkins, John; Martinez, Alex; Knapp, Ralph W.; Macfarlane, P. Allan; Watney, W. Lynn; Black, Ross

    1994-06-01

    Since late Tertiary, bedded rock salt of the Permian Hutchinson Salt Member has been dissolved more-or-less continuously along its active eastern margin in central Kansas as a result of sustained contact with unconfined, undersaturated groundwater. The associated westward migration of the eastern margin has resulted in surface subsidence and the contemporaneous sedimentation of predominantly valley-filling Quarternary alluvium. In places, these alluvium deposits extend more than 25 km to the east of the present-day edge of the main body of contiguous rock salt. The margin could have receded this distance during the past several million years. From an environmental perspective, the continued leaching of the Hutchinson Salt is a major concern. This predominantly natural dissolution occurs in a broad zone across the central part of the State and adversely affects groundwater and surface-water quality as nonpoint source pollution. Significant surface subsidence occurs as well. Most of these subsidence features have formed gradually; others developed in a more catastrophic manner. The latter in particular pose real threats to roadways, railways, and buried oil and gas pipelines. In an effort to further clarify the process of natural salt dissolution in central Kansas and with the long-term goal of mitigating the adverse environmental affects of such leaching, the Kansas Geological Survey acquired a 4-km seismic profile across the eastern margin of the Hutchinson Salt in the Punkin Center area of central Kansas. The interpretation of these seismic data (and supporting surficial and borehole geologic control) is consistent with several hypotheses regarding the process and mechanisms of dissolution. More specifically these data support the theses that: (1) Dissolution along the active eastern margin of the Hutchinson Salt Member was initiated during late Tertiary. Leaching has resulted in the steady westward migration of the eastern margin, surface subsidence, and the

  14. Tectonic expression of an active slab tear from high-resolution seismic and bathymetric data offshore Sicily (Ionian Sea)

    NASA Astrophysics Data System (ADS)

    Gutscher, Marc-André; Dominguez, Stephane; Lepinay, Bernard Mercier; Pinheiro, Luis; Gallais, Flora; Babonneau, Nathalie; Cattaneo, Antonio; Le Faou, Yann; Barreca, Giovanni; Micallef, Aaron; Rovere, Marzia

    2016-01-01

    Subduction of a narrow slab of oceanic lithosphere beneath a tightly curved orogenic arc requires the presence of at least one lithospheric scale tear fault. While the Calabrian subduction beneath southern Italy is considered to be the type example of this geodynamic setting, the geometry, kinematics and surface expression of the associated lateral, slab tear fault offshore eastern Sicily remain controversial. Results from a new marine geophysical survey conducted in the Ionian Sea, using high-resolution bathymetry and seismic profiling reveal active faulting at the seafloor within a 140 km long, two-branched fault system near Alfeo Seamount. The previously unidentified 60 km long NW trending North Alfeo Fault system shows primarily strike-slip kinematics as indicated by the morphology and steep-dipping transpressional and transtensional faults. Available earthquake focal mechanisms indicate dextral strike-slip motion along this fault segment. The 80 km long SSE trending South Alfeo fault system is expressed by one or two steeply dipping normal faults, bounding the western side of a 500+ m thick, 5 km wide, elongate, syntectonic Plio-Quaternary sedimentary basin. Both branches of the fault system are mechanically capable of generating magnitude 6-7 earthquakes like those that struck eastern Sicily in 1169, 1542, and 1693.

  15. The analysis of interseismic GPS observation and its implication to seismic activity in Taiwan area

    NASA Astrophysics Data System (ADS)

    Tsai, M. C.; Yu, S. B.; Shin, T. C.

    2015-12-01

    Taiwan is an active tectonic area with about 80 mm/yr plate convergence rate. To understand the crustal deformation and seismic potential in Taiwan area. We derived 2009-2014 interseismic GPS velocity field and strain rate, implicate to seismic activity of 2005-2014. Data collected by 281 sites of Taiwan Continuous GPS (cGPS) Array and processed with GAMIT/GLOBK software. Stacking of power spectral densities from cGPS data in Taiwan, we found the errors type can be described as a combination of white noise and flicker noise. The common errors are removed by stacking 50 cGPS sites with data period larger than 5 years. By removing the common errors, the precision of GPS data has been further improved to 2.3 mm, 1.9 mm, and 6.9 mm in the E, N, U components, respectively. After strictly data quality control, time series analysis and noise analysis, we derive an interseismic ITRF2008 velocity field from 2009 to 2014 in the Taiwan area. The general pattern is quite similar with previous studies, but the station density is much larger and spatial coverage better. Based on this interseismic velocity field, we estimate the crustal strain rate in Taiwan area. Approximately half of plate convergence strain rate is accommodated on the fold and thrust belt of western Taiwan and another half is taken up in the Longitudinal Valley and the Coastal Range in eastern Taiwan. The maximum dilatation rates is about -0.75~-0.9 μstrain/yr in WNW-ESE direction. The velocities in western Taiwan generally show a fan-shaped pattern, consistent with the direction of maximum compression tectonic stress. Extension in the E-W direction is observed at the Central Range area, the focal mechanism results also indicate the earthquake type here most are normal faults. In northern Taiwan, the velocity vectors reveal clockwise rotation, indicating the on-going extensional deformation related to the back-arc extension of the Okinawa Trough. In southern Taiwan, the horizontal velocity increases from

  16. Tectonic history and thrust-fold deformation style of seismically active structures near Coalinga

    SciTech Connect

    Namson, J.S. ); Davis, T.L.; Lagoe, M.B.

    1990-01-01

    The stratigraphy of the Coalinga region can be divided into tectostratigraphic facies whose boundaries delineate two major tectonic events - one in the mid-Cenozoic (38-17 Ma) and one in the late Cenozoic (less than 3 Ma). The succession of these tectostratigraphic facies, and an integration of geology, subsurface well data, a seismic-reflection profile, and earthquake seismicity on a retrodeformable cross section, yield a model for the tectonic evolution of the Coalinga region. This model suggests that the structural style of both deformational events is characteristic of fold and thrust belts. The model also indicates that the causative fault of the May 2 earthquake is a ramped thrust. The results of this study, in combination with regional geologic relations, suggest that the Coalinga region is part of an active fold and thrust belt which borders the west and south sides of the San Joaquin Valley. The potential for future earthquakes due to movement of other blind thrust faults within this belt should be evaluated.

  17. 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.

  18. 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

  19. An developing ICDP drilling project on intraplate seismicity: Drilling Active Faults in Northern Europe (DAFNE)

    NASA Astrophysics Data System (ADS)

    Ask, M. V.; Kukkonen, I. T.; Olesen, O.; Steffen, H.; Schmitt, D.

    2011-12-01

    The combined effects of reduced ice load and glacially affected rock stresses are believed to have generated dramatic postglacial fault (PGF) structures in northern Europe, reflecting a special type of intraplate seismicity. A total of 14 PGFs have been identified up to date, with fault scarps up to 160 km in length and 30 m in height. They are usually SE dipping, SW-NE oriented thrusts that represent reactivated, pre-existing crustal discontinuities. Local and national seismic networks reveal that, at least some of the faults are still very active, with several hundreds of microseismic events each year. It is evident that if they were formed in single events, they would imply massive intraplate earthquakes (up to M 7-8). Hence, PGFs may generate larger intraplate earthquakes than generally assumed. Similar structures in North America have not been reported yet. Currently, an International Continental Drilling Program (ICDP) project on Drilling Active Faults in Northern Europe (DAFNE) is under development. The aim of the project is to investigate tectonic and structural characteristics of PGFs in northern Fennoscandia, including their hydrogeology and associated deep biosphere. The research is anticipated to advance science in neotectonics, hydrogeology and deep biosphere studies, and provide important information for nuclear waste and CO2 disposal, petroleum exploration on the Norwegian continental shelf and studies of mineral resources in PG fault areas. We expect that multidisciplinary research applying shallow and deep drilling of PGFs would provide significant scientific results through generating new data and models, namely: 1. Understanding PGF genesis and controls of their locations; 2. Deep structure and depth extent of PGFs; 3. Textural, mineralogical and physical alteration of rocks in the PGFs; 4. State of stress and estimates of paleostress of PGFs; 5. Hydrogeology, hydrochemistry and hydraulic properties of PGFs; 6. Dating of tectonic reactivation

  20. 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

  1. Long-Term Soil Gas Surveys in the Northern Part of the Modena Province Pre, During and After the 2012 Seismic Sequence

    NASA Astrophysics Data System (ADS)

    Sciarra, A.; Cantucci, B.; Galli, G.; Cinti, D.; Quattrocchi, F.

    2014-12-01

    Three geochemical surveys of soil gas (CO2 and CH4 flux measurements, He, H2, CO2, CH4 and C2H6 concentrations) and isotopic analyses (δ13C-CH4, δD-CH4, δ13C-CO2) were carried out as part of a feasibility study for a natural gas storage site in the Modena Province (Northern Italy), during the 2006-2009 period. In May-June 2012, a seismic sequence (main shocks of ML 5.9 and 5.8) was occurred closely to the investigated area. Chemical and isotopic analysis were repeated in May 2012, September 2012, June 2013 and July 2014. In the 2006-2009 period, at the pre-seismic conditions, chemical composition of soil gas showed that the southern part of the studied area is CH4-dominated, whereas the northern part is CO2-dominated. Relatively anomalous fluxes and concentrations were recorded with a spotted areal distribution. Anyway, CO2 and CH4 values are within the typical range of vegetative and of organic exhalation of the cultivated soil. 2012-2013 soil gas results show CO2 values essentially unvaried with respect to pre-earthquake surveys, while the 2014 values highlight an increasing of CO2 flux in the whole study area. On the contrary, CH4 values seem to be on average higher after the seismic sequence, although with a decreasing trend in the last survey (2014). Isotopic analysis were carried out only on samples with anomalous values. The δ13C-CO2 value suggests a prevalent shallow origin of CO2 (i.e. organic and/or soil-derived) probably related to anaerobic oxidation of heavy hydrocarbons. Methane isotopic data (δ13C-CH4) indicate a typical biogenic origin (i.e. microbial hydrocarbon production) of the CH4, as recognized elsewhere in the Po Plain and surroundings. Obtained results highlight a different CO2 and CH4 behaviour before, during and after the seismic events. These variations could be produced by increasing of bacterial (e.g. peat strata) and methanogenic fermentation processes in the first meters of the soil. No hints of deep degassing can be inferred for

  2. Combined analysis of passive and active seismic measurements using additional geologic data for the determination of shallow subsurface structures

    NASA Astrophysics Data System (ADS)

    Horstmann, Tobias; Brüstle, Andrea; Spies, Thomas; Schlittenhardt, Jörg; Schmidt, Bernd

    2016-04-01

    A detailed knowledge of subsurface structure is essential for geotechnical projects and local seismic hazard analyses. Passive seismic methods like microtremor measurements are widely used in geotechnical practice, but limitations and developments are still in focus of scientific discussion. The presentation outlines microtremor measurements in the context of microzonation in the scale of districts or small communities. H/V measurements are used to identify zones with similar underground properties. Subsequently a shear wave velocity (Vs) depth profile for each zone is determined by array measurements at selected sites. To reduce possible uncertainties in dispersion curve analyses of passive array measurements and ambiguities within the inversion process, we conducted an additional active seismic experiment and included available geological information. The presented work is realized in the framework of the research project MAGS2 ("Microseismic Activity of Geothermal Systems") and deals with the determination of seismic hazard analysis at sites near deep geothermal power plants in Germany. The measurements were conducted in the Upper Rhine Graben (URG) and the Bavarian molasses, where geothermal power plants are in operation. The results of the H/V- and array-measurements in the region of Landau (URG) are presented and compared to known geological-tectonic structures. The H/V measurements show several zones with similar H/V-curves which indicate homogenous underground properties. Additionally to the passive seismic measurements an active refraction experiment was performed and evaluated using the MASW method („Multichannel Analysis of Surface Waves") to strengthen the determination of shear-wave-velocity depth profile. The dispersion curves for Rayleigh-waves of the active experiment support the Rayleigh-dispersion curves from passive measurements and therefore provide a valuable supplement. Furthermore, the Rayleigh-wave ellipticity was calculated to reduce

  3. 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

  4. General aviation activity survey. Annual summary report for 1992

    SciTech Connect

    Not Available

    1992-01-01

    This report presents the results of the annual General Aviation Activity Survey. The survey is conducted by the FAA to obtain information on the flight activity of the United States registered general aviation aircraft fleet. The report contains breakdowns of active aircraft, annual flight hours, average flight hours and other statistics by manufacturer/model group, aircraft type, state and region of based aircraft, and primary use. Also included are fuel consumption, lifetime airframe hours, engine hours, miles flown estimates, estimates of the number of landings, IFR hours flown, and grade of fuel consumed by the general aviation fleet. Aircraft, Aircraft activity, Aircraft use, Fuel consumption, General aviation, Hours flown, Miles flown.

  5. 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

  6. Micro-seismicity survey of a seismic gap caused by the subduction of the Louisville seamount chain in the Tonga trench, 25°30’S to 28°S

    NASA Astrophysics Data System (ADS)

    Grevemeyer, I.; Dannowski, A.; Flueh, E. R.; Moeller, S.

    2009-12-01

    The distribution of teleseismically recorded earthquakes in the Kermadec-Tonga subduction zone reveals a major seismic gap centered roughly at 26°S. The gap parallels the trench axis and stretches for approximately 250 km. The seismic gap coincides with the area, where the Louisville hotspot chain enters the Tonga trench. Subducting seamounts may therefore control seismic coupling and hence define seismogenic asperities in subduction zones. Louisville seamounts rise 3 to 4 km above the regional seafloor. Seamounts and guyots are between 10 to 40 km in diameter and hence smaller than the width of the seismic gap, suggesting that other features - like the hotspot swell, crustal underplating or the flexural may contribute or control seismic locking. We deployed a network of 21 ocean-bottom-seismometers (OBS) and 2 ocean-bottom-hydrophones (OBH), including 9 broadband OBS with Guralp CMG-40T sensors. The network covered the southern portion of the seismic gap and the transition zone to “normal” seismic behavior. The ocean bottom seismic stations provided data from July 9, 2007 to December 31, 2007. For the earthquake location procedure we derived a minimum 1-D velocity model from active seismic wide-angle profiling in the uppermost 6 km of the fore-arc crust and earthquake arrival time data at greater depths. In total 1523 local and regional earthquake could be located. Within the network, 383 events have been recorded with a gap of <230 degree at 4 stations, and 160 events with a gap of <180 degree at 6 stations. It is interesting to note that local earthquakes (M < 4) did not mimic the teleseismic gap. Overall, seismicity seems to be randomly distributed within the network. Furthermore, in contrast to other subduction zones, where earthquakes occur predominantly along the subduction megathrust fault, we observed only a few events along the plate boundary. Thus, most local earthquakes occur in the uppermost mantle, perhaps caused by extension related to the slab

  7. Active rifting processes in the central Salton Trough, California, constrained by the Salton Seismic Imaging Project (SSIP)

    NASA Astrophysics Data System (ADS)

    Han, L.; Hole, J. A.; Stock, J. M.; Fuis, G. S.; Driscoll, N. W.; Kell, A. M.; Kent, G.; Harding, A. J.

    2012-12-01

    Seismic refraction and reflection travel times from the Salton Seismic Imaging Project (SSIP) are being used to constrain crustal structure during active continental rifting in the central Salton Trough, California. SSIP, funded by NSF and USGS, acquired seismic data in and across the Salton Trough in 2011 to investigate rifting processes at the northern end of the Gulf of California extensional province and earthquake hazards at the southern end of the San Andreas Fault system. Seven lines of refraction and low-fold reflection data were acquired onshore, two lines and a grid of airgun and OBS data were acquired in the Salton Sea, and onshore-offshore data were recorded. Based on prior studies of the central Salton Trough, North American lithosphere appears to have been rifted completely apart and replaced by entirely new crust added by magmatism from below and sedimentation from above. Ongoing active rifting of this new crust is manifested by shallow (<10km depth) seismicity in the oblique Brawley Seismic Zone (BSZ; connecting the Imperial and San Andreas faults), the small Salton Buttes volcanoes (aligned perpendicular to the direction of plate motion), and very high heat flow. Analyses of the onshore-offshore seismic line that extends along the axis of the valley, parallel to the direction of plate motion, constrain crustal structure in the valley. Crystalline basement (~5 km/s) generally occurs at ~4 km depth, but is at 2-3 km depth in a localized region beneath the Salton Buttes and Salton Sea geothermal field. This crystalline rock is interpreted to be late Pliocene to Quaternary sediment metamorphosed by high heat flow. The shallower basement under the volcanic and geothermal field is due to more intense metamorphism and hydrothermal alteration in this region. The seismic velocity of basement is slower in the BSZ than to the south and north, which may be due to seismicity-related fracturing. The basement velocity beneath the Salton Buttes and geothermal

  8. 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.

  9. 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.

  10. Exhumed analogues of seismically active carbonate-bearing thrusts: fault architecture and deformation mechanisms

    NASA Astrophysics Data System (ADS)

    Tesei, T.; Collettini, C.; Viti, C.; Barchi, M. R.

    2012-12-01

    In May 2012 a M = 5.9 earthquake followed by a long aftershock sequence struck the Northern Italy. The sequence occurred at 4-10 km depth within the active front of Northern Apennines Prism and the major events nucleate within, or propagate through, a thick sequence of carbonates. In an inner sector of the Northern Apennines, ancient carbonate-bearing thrusts exposed at the surface, represent exhumed analogues of structures generating seismicity in the active front. Here we document fault architecture and deformation mechanisms of three regional carbonate bearing thrusts with displacement of several kilometers and exhumation in the range of 1-4 km. Fault zone structure and deformation mechanisms are controlled by the lithology of the faulted rocks. In layered limestones and marly-limestones the fault zone is up to 200 m thick and is characterized by intense pressure solution. In massive limestones the deformation generally occurs along thin and sharp slip planes that are in contact with fault portions affected by either cataclasis or pressure solution. SEM and TEM observations show that pressure solution surfaces, made of smectite lamellae, with time tend to form an interconnected network affected by frictional sliding. Sharp slipping planes along massive limestones show localization along Y shear planes that separate an extremely comminuted cataclasites from an almost undeformed protolith. The comparison of the three shear zones depicts a fault zone structure extremely heterogeneous as the result of protolith lithology, geometrical complexities and the presence of inherited structures. We observe the competition between brittle (cataclasis, distributed frictional sliding along phyllosilicates and extremely localized slip within carbonates) and pressure solution processes, that suggest a multi-mode of slip behaviour. Extreme localization along carbonate-bearing Y shear planes is our favorite fault zone feature representing past seismic ruptures along the studied

  11. Experimental investigation on seismic response control of adjacent buildings using semi-active MR dampers

    NASA Astrophysics Data System (ADS)

    Ni, Yi-Qing; Liu, H. J.; Ko, Jan Ming

    2002-06-01

    This paper reports an experimental study on semi-active seismic response control of adjacent building structures using magneto-rheological (MR) dampers. A 1:15 scaled adjacent structural system consisting of a 12-story building model and an 8-story building model was tested on shaking table with MR damper passive and semi-active control. An MR damper with large stroke is specifically designed for this study. After experimentally identifying dynamic characteristics of the individual MR damper and the uncontrolled structural models, the two building models are interconnected with the MR damper at different floors and semi-active control is implemented using the dSPACE DS1005 real-time control system. The structures are excited on their base by a shaking table imposing sweep sine excitation and El Centro earthquake excitation. A stochastic optimal control strategy proposed by the authors is applied through the dSPACE system and its MATLAB environment to accomplish real-time semi-active control from the measurement of displacement and velocity responses at each floor. This control strategy results in a dissipative energy control with its feedback control force being a nonlinear generalized damping force. The structural response under semi-active control is compared with that by using the MR damper as a passive device without voltage input. Different MR damper installation locations are addressed in the experimental study to search for maximum response mitigation capability.

  12. 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

  13. Periods of the Earth's seismicity activation and their relationship to variations in the Earth's rotation velocity

    NASA Astrophysics Data System (ADS)

    Sasorova, Elena; Levin, Boris

    2015-04-01

    It is known that Earth's seismic activity (SA) demonstrates distinct roughness (nonuniformity) in time. Periods of intensification of the SA followed by periods of its decaying. For strong earthquakes these periods are continued several decades. It was also noted that there is a pronounced periodic amplification and attenuation of the SA with a period of about 30 years, which is manifested mainly in two latitudinal belts 50°N-30°N and 0°-30°S [Levin, Sasorova, 2014, 2015]. This work deals with the hypothesis that it is the properties of rotating non-uniform rate of the planet may be the cause of the periodicity of manifestations SA. The objective of this work is the searching of the spatial-temporal interconnection between the Earth rotation irregularity and the observed cyclic increasing and decreasing of the Earth's SA. This requires preparation a long series of observations of seismic events with representative data sets (EQ selected from 1895 up to date with a magnitude M> = 7.5, based on the catalog NEIC). Two sources of data on the angular velocity of the Earth's rotation of (length of day, LOD) were adapted: the world-known database IERS (Annual Report, International Earth Rotation Service) and the data, which were presented in the work (McCarthy, D.D., and Babcock A.K., 1986). The first one contains daily observations from 1962 to 2013, the second one was identified semi-annual observations from 1720 to 1984. It was prepared concatenated data set (CLOD) for the period from 1720 to 2013. Characteristic periods in the time series CLOD: 62, 32, and 23 years have been isolated by the use of spectral analysis. Next, it were used a band-pass filters for the four frequency bands from 124 to 45 years, from 37 do 25 years, from 25 to 19 years, and in the range of less than 19 years. In the frequency bands 37-25 years and 25-19 years marked clear periodic oscillations close to a sine wave. The amplitude of the oscillations with the 1720 to 1790 gradually

  14. Installation of a digital, wireless, strong-motion network for monitoring seismic activity in a western Colorado coal mining region

    SciTech Connect

    Peter Swanson; Collin Stewart; Wendell Koontz

    2007-01-15

    A seismic monitoring network has recently been installed in the North Fork Valley coal mining region of western Colorado as part of a NIOSH mine safety technology transfer project with two longwall coal mine operators. Data recorded with this network will be used to characterize mining related and natural seismic activity in the vicinity of the mines and examine potential hazards due to ground shaking near critical structures such as impoundment dams, reservoirs, and steep slopes. Ten triaxial strong-motion accelerometers have been installed on the surface to form the core of a network that covers approximately 250 square kilometers (100 sq. miles) of rugged canyon-mesa terrain. Spread-spectrum radio networks are used to telemeter continuous streams of seismic waveform data to a central location where they are converted to IP data streams and ported to the Internet for processing, archiving, and analysis. 4 refs.

  15. Archive of Digital Boomer Seismic Reflection Data Collected During USGS Field Activity 02LCA02 in Lakes Ada, Crystal, Jennie, Mary, Rice, and Sylvan, Central Florida, July 2002

    USGS Publications Warehouse

    Harrison, Arnell S.; Dadisman, Shawn V.; Davis, Jeffrey B.; Wiese, Dana S.

    2008-01-01

    In July of 2002, the U.S. Geological Survey and St. Johns River Water Management District (SJRWMD) conducted geophysical surveys in Lakes Ada, Crystal, Jennie, Mary, Rice, and Sylvan, central Florida, as part of the USGS Lakes and Coastal Aquifers (LCA) study. This report serves as an archive of unprocessed digital boomer seismic reflection data, trackline maps, navigation files, Geographic Information System (GIS) files, and formal Federal Geographic Data Committee (FGDC) metadata. Filtered and gained (a relative increase in signal amplitude) digital images of the seismic profiles are also provided. Refer to the Acronyms page for expansions of acronyms and abbreviations used in this report. The archived trace data are in standard Society of Exploration Geophysicists (SEG) SEG-Y format (Barry and others, 1975) and may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU). Example SU processing scripts and USGS software for viewing the SEG-Y files (Zihlman, 1992) are also provided. The USGS Florida Integrated Science Center (FISC) - St. Petersburg assigns a unique identifier to each cruise or field activity. For example, 02LCA02 tells us the data were collected in 2002 for the Lakes and Coastal Aquifers (LCA) study and the data were collected during the second field activity for that study in that calendar year. Refer to http://walrus.wr.usgs.gov/infobank/programs/html/definition/activity.html for a detailed description of the method used to assign the field activity ID. The boomer plate is an acoustic energy source that consists of capacitors charged to a high voltage and discharged through a transducer in the water. The transducer is towed on a sled floating on the water surface and when discharged emits a short acoustic pulse, or shot, which propagates through the water, sediment column, or rock beneath. The acoustic energy is reflected at density boundaries (such as the seafloor, sediment, or rock layers beneath the

  16. 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

  17. Deep Seismic Imaging of an Active Foreland Basin: Implications for Flexural Models

    NASA Astrophysics Data System (ADS)

    White, N.

    2003-12-01

    The South Falkland basin is a partially filled, active, foreland basin located at the southern edge of the Falkland Plateau. It was formed by flexure of the South American plate as a result of loading by the northern edge of the Scotia plate. Flexure probably started in the Paleogene and continues to the present day. The entire region is submarine and the detailed structure of this basin is clearly imaged on shallow reflection data. Admittance analysis of free-air gravity and bathymetry together with gravity and basement profile modelling suggest that the elastic thickness is 10--20 km. Recently, we have acquired and processed a deep seismic reflection profile which crosses the foreland basin and the zone of active collision. This line was shot to 18 seconds two-way travel time using a 5600 cubic inch airgun array and a 6 km streamer. These new data have yielded spectacular images of the active foreland basin and of the adjacent plateaux. The most striking features are a clearly imaged Moho and a set of highly reflective normal faults which penetrate to about 20 km depth. We can show that these normal faults were active during the process of plate flexure. Their existence, depth of penetration and reflectivity raise important questions about the applicability of elastic models to foreland basin formation. Here we explore alternative models which can account for these new observations without requiring the existence of large elastic stresses.

  18. Ambient seismic noise levels: A survey of the permanent and temporary seismographic networks in Morocco, North Africa

    NASA Astrophysics Data System (ADS)

    El Fellah, Y.; Khairy Abd Ed-Aal, A.; El Moudnib, L.; Mimoun, H.; Villasenor, A.; Gallart, J.; Thomas, C.; Elouai, D.; Mimoun, C.; Himmi, M.

    2013-12-01

    Abstract The results, of a conducted study carried out to analyze variations in ambient seismic noise levels at sites of the installed broadband stations in Morocco, North Africa, are obtained. The permanent and the temporary seismic stations installed in Morocco of the Scientific Institute ( IS, Rabat, Morocco), institute de Ciencias de la Tierra Jaume almera (ICTJA, Barcelona, Spain) and Institut für Geophysik (Munster, Germany) were used in this study. In this work, we used 23 broadband seismic stations installed in different structural domains covering all Morocco from south to north. The main purposes of the current study are: 1) to present a catalog of seismic background noise spectra for Morocco obtained from recently installed broadband stations, 2) to assess the effects of experimental temporary seismic vault construction, 3) to determine the time needed for noise at sites to stabilize, 4) to establish characteristics and origin of seismic noise at those sites. We calculated power spectral densities of background noise for each component of each broadband seismometer deployed in the different investigated sites and then compared them with the high-noise model and low-noise Model of Peterson (1993). All segments from day and night local time windows were included in the calculation without parsing out earthquakes. The obtained results of the current study could be used forthcoming to evaluate permanent station quality. Moreover, this study could be considered as a first step to develop new seismic noise models in North Africa not included in Peterson (1993). Keywords Background noise; Power spectral density; Model of Peterson; Scientific Institute; Institute de Ciencias de la Tierra Jaume almera; Institut für Geophysik

  19. Investigating possible influence of solar activity on some reported seismic-induced ionospheric precursors via VLF wave propagation in Earth-ionosphere waveguide

    NASA Astrophysics Data System (ADS)

    Nwankwo, Victor U. J.; Chakrabarti, Sandip Kumar; Sasmal, Sudipta; Ray, Suman

    2016-07-01

    The diurnal propagation characteristic of VLF radio signal have been widely used to study pre-seismic ionospheric anomalies, some of which are often reported to be associated with the event. On the other hand, Solar particle events and geomagnetic activity also drive changes in the magnetosphere, which modify ionospheric parameters through the Earth's magnetic field. There are also effects originating from planetary and tidal waves, thermospheric tides and stratospheric warming. Distinguishing or separating seismically induced ionospheric fluctuations from those of other origin remain vital and challenging. In this work, we investigated the influence of solar and geomagnetic origin on some reported 'seismic ionospheric precursors' before a few major earthquakes. We also investigated anomalies in VLF day-length signal during period of low solar and geomagnetic activity (in relation to seismic activity), to understand the occurrence of VLF anomaly that are unrelated to seismicity and solar activity.

  20. Bias in Student Survey Findings from Active Parental Consent Procedures

    ERIC Educational Resources Information Center

    Shaw, Thérèse; Cross, Donna; Thomas, Laura T.; Zubrick, Stephen R.

    2015-01-01

    Increasingly, researchers are required to obtain active (explicit) parental consent prior to surveying children and adolescents in schools. This study assessed the potential bias present in a sample of actively consented students, and in the estimates of associations between variables obtained from this sample. Students (n = 3496) from 36…

  1. Monitoring and Characterizing the Geysering and Seismic Activity at the Lusi Mud Eruption Site, East Java, Indonesia

    NASA Astrophysics Data System (ADS)

    Karyono, Karyono; Obermann, Anne; Mazzini, Adriano; Lupi, Matteo; Syafri, Ildrem; Abdurrokhim, Abdurrokhim; Masturyono, Masturyono; Hadi, Soffian

    2016-04-01

    The Lusi eruption began on May 29, 2006 in the northeast of Java Island, Indonesia, and to date is still active. Lusi is a newborn sedimentary-hosted hydrothermal system characterized by continuous expulsion of liquefied mud and breccias and geysering activity. Lusi is located upon the Watukosek fault system, a left lateral wrench system connecting the volcanic arc and the bakarc basin. This fault system is still periodically reactivated as shown by field data. In the framework of the Lusi Lab project (ERC grant n° 308126) we conducted several types of monitoring. Based on camera observations, we characterized the Lusi erupting activity by four main behaviors occurring cyclically: (1) Regular activity, which consists in the constant emission of water and mud breccias (i.e. viscous mud containing clay, silt, sand and clasts) associated with the constant expulsion of gas (mainly aqueous vapor with minor amounts of CO2 and CH4) (2) Geysering phase with intense bubbling, consisting in reduced vapor emission and more powerful bursting events that do not seem to have a regular pattern. (3) Geysering phase with intense vapor and degassing discharge and a typically dense plume that propagates up to 100 m height. (4) Quiescent phase marking the end of the geysering activity (and the observed cycle) with no gas emissions or bursts observed. To investigate the possible seismic activity beneath Lusi and the mechanisms controlling the Lusi pulsating behaviour, we deployed a network of 5 seismic stations and a HD camera around the Lusi crater. We characterize the observed types of seismic activity as tremor and volcano-tectonic events. Lusi tremor events occur in 5-10 Hz frequency band, while volcano tectonic events are abundant in the high frequencies range from 5 Hz until 25 Hz. We coupled the seismic monitoring with the images collected with the HD camera to study the correlation between the seismic tremor and the different phases of the geysering activity. Key words: Lusi

  2. 2D Time-lapse Seismic Tomography Using An Active Time Constraint (ATC) Approach

    EPA Science Inventory

    We propose a 2D seismic time-lapse inversion approach to image the evolution of seismic velocities over time and space. The forward modeling is based on solving the eikonal equation using a second-order fast marching method. The wave-paths are represented by Fresnel volumes rathe...

  3. Evaluation and developmental studies of possible active seismic experiments during the post-Apollo period

    NASA Technical Reports Server (NTRS)

    Kovach, R. L.

    1974-01-01

    Seismic velocity studies pertinent to the lunar crust and mantle are briefly summarized. The compressional and shear wave velocities in loose aggregates are discussed along with the effects of temperature on seismic velocity in compacted powders. Abstracts of papers concerning the lunar structure are included.

  4. Geophysical Surveys of the San Andreas and Crystal Springs Reservoir System Including Seismic-Reflection Profiles and Swath Bathymetry, San Mateo County, California

    USGS Publications Warehouse

    Finlayson, David P.; Triezenberg, Peter J.; Hart, Patrick E.

    2010-01-01

    This report describes geophysical data acquired by the U.S. Geological Survey (USGS) in San Andreas Reservoir and Upper and Lower Crystal Springs Reservoirs, San Mateo County, California, as part of an effort to refine knowledge of the location of traces of the San Andreas Fault within the reservoir system and to provide improved reservoir bathymetry for estimates of reservoir water volume. The surveys were conducted by the Western Coastal and Marine Geology (WCMG) Team of the USGS for the San Francisco Public Utilities Commission (SFPUC). The data were acquired in three separate surveys: (1) in June 2007, personnel from WCMG completed a three-day survey of San Andreas Reservoir, collecting approximately 50 km of high-resolution Chirp subbottom seismic-reflection data; (2) in November 2007, WCMG conducted a swath-bathymetry survey of San Andreas reservoir; and finally (3) in April 2008, WCMG conducted a swath-bathymetry survey of both the upper and lower Crystal Springs Reservoir system. Top of PageFor more information, contact David Finlayson.

  5. A Precursory Phase to a Sudden Enhanced Activity at Yasur volcano (Vanuatu) : Insights from Simultaneous Infrasonic and Seismic Records

    NASA Astrophysics Data System (ADS)

    Vergniolle, S.; Zielinski, C.; Battaglia, J.; Metaxian, J. P.; Bani, P.; LE Pichon, A.; Lardy, M.; Millier, P.; Frogneux, M.; Gallois, F.; Herry, P.; Todman, S.; Garaebiti, E.

    2015-12-01

    The permanent activity at Yasur (Vanuatu), characterised by a close series of Strombolian explosions, is analysed using simultaneous infrasonic and seismic recordings (6-25 Nov 2008) close to the vents. The RMS amplitudes per hour, the number of explosions and the peak-to-peak amplitudes of each signal show that the initial quiet phase (11 days) is followed by a precursory phase (7 days) prior to an enhanced activity (17 hours). Three periods exist during the strong activity: (1) a rapid increase leading to the paroxysm (3 hours), (2) a first (5 hours) and (3) a second decrease (9 hours), each having an excellent correlation between seismic and infrasonic RMS amplitudes per hour (correlation coefficient > 0.96) when using the band associated to explosions (1-5 Hz and 1.8-4 Hz for seismic and infrsonic recordings, respectively). The ratio between infrasonic and seismic RMS amplitudes, assumed to be a proxy for the magma level, increases strongly during the week before the paroxysm. This is explained by the arrival of an additional gas flux at the top of the reservoir. The foam accumulated there, whose partial coalescence and spreading towards the conduit are responsible for the permanent Strombolian activity, thickens. This enhances both the viscous massive foam coalescence and the foam spreading. This leads to an increase in the gas flux in the conduit, ultimately responsible for the formation of a shallow foam at the surface. This foam acts as a viscous cap overlying the magma column, thereby increasing the radiated infrasonic pressure and the strength of the explosions. The first decrease in the relationship between infrasonic and seismic RMS amplitudes is associated with the stopping of the additionnal gas flux in the magma reservoir and the rapid decrease of the top of the magma column due to the previous intense degassing. The second decrease corresponds to the time neccessary to restore the convective motions in the conduit at their normal velocities.

  6. High-resolution single-channel seismic reflection surveys of Orange Lake and other selected sites of north central Florida

    USGS Publications Warehouse

    Kindinger, Jack G.; Davis, Jeffrey B.; Flocks, James G.

    1994-01-01

    The potential fluid exchange between lakes of north central Florida and the Floridan aquifer and the process by which exchange occurs is of critical concern to the St. Johns Water Management District. High-resolution seismic tools with relatively new digital technology were utilized in collecting geophysical data from Orange, Kingsley, Lowry and Magnolia Lakes, and the Drayton Island area of St. Johns River. The data collected shows the application of these techniques in understanding the formation of individual lakes, thus aiding in the management of these natural resources by identifying breaches or areas where the confining units are thin or absent between the water bodies and the Floridan aquifer. Orange Lake, the primary focus of the study, is a shallow flooded plain that was formed essentially as an erosional depression in the clayey Hawthorn formation. The primary karstic features identified in the lake were cover subsidence, cover collapse and buried sinkholes structures in various sizes and stages of development. Orange Lake was divided into three areas southeast, southwest, and north-central. Karst features within the southeast area of Orange Lake are mostly cover subsidence sinkholes and associated features. Many of the subsidence features found are grouped together to form larger composite sinkholes, some greater than 400 m in diameter. The size of these composite sinkholes and the number of buried subsidence sinkholes distinguish the southeast area from the others. The potential of lake waters leaking to the aquifer in the southeast area is probably controlled by the permeability of the cover sediments or by fractures that penetrate the lake floor. The lake bottom and subsurface of the north-central areas are relatively subsidence sinkholes that have no cover sediments overlying them, implying that the sinks have been actively subsiding with some seepage into the aquifer from the lake in this area due to the possible presence of the active subsidence

  7. 1990 Nationwide Truck Activity and Commodity Survey selected tabulations

    SciTech Connect

    Not Available

    1993-06-01

    The Nationwide Truck Activity and Commodity Survey (NTACS) provides detailed activity data for a sample of trucks covered in the 1987 Truck Inventory and Use Survey (TIUS) for days selected at random over a 12-month period ending in 1990. The NTACS was conducted by the US Bureau of the Census for the US Department of Transportation (DOT). A Public Use File for the NTACS was developed by Oak Ridge National Laboratory (ORNL) under a reimbursable agreement with the DOT. The content of the Public Use File and the detailed design of the NTACS are described in the ORNL Report [open quotes]Technical Documentation for the 1990 Nationwide Truck Activity and Commodity Survey Public Use File[close quotes]. (1992). ORNL Technical Report No. TM-12188, Oak Ridge National Laboratory, Oak Ridge, TN 37831. The main purpose of this summary report is to provide selected tables based on the public use file.

  8. Microearthquake--array studies of the seismicity in Southeast Missouri

    USGS Publications Warehouse

    Stauder, W.

    1977-01-01

    Supported by the U.S Geological Survey, my colleagues Mark Kramer, Gerard Fischer, Stephen Schaefer, Sean Morrissey, and I have recently established a microearthquake network in the New Madrid seismic zone. The network has been in operation for only 21 months, yet we have already been able to show, from the hypocenters located so far, that earthquakes in this region occur along linear zones, which we believe corespond to seismically active faults. 

  9. Active optics system of the VLT Survey Telescope.

    PubMed

    Schipani, Pietro; Noethe, Lothar; Magrin, Demetrio; Kuijken, Konrad; Arcidiacono, Carmelo; Argomedo, Javier; Capaccioli, Massimo; Dall'Ora, Massimo; D'Orsi, Sergio; Farinato, Jacopo; Fierro, Davide; Holzlöhner, Ronald; Marty, Laurent; Molfese, Cesare; Perrotta, Francesco; Ragazzoni, Roberto; Savarese, Salvatore; Rakich, Andrew; Umbriaco, Gabriele

    2016-03-01

    This paper describes the active optics system of the VLT Survey Telescope, the 2.6-m survey telescope designed for visible wavelengths of the European Southern Observatory at Cerro Paranal, in the Atacama desert. The telescope is characterized by a wide field of view (1.42 deg diameter), leading to tighter active optics than in conventional telescopes, in particular for the alignment requirements. We discuss the effects of typical error sources on the image quality and present the specific solutions adopted for wavefront sensing and correction of the aberrations, which are based on the shaping of a monolithic primary mirror and the positioning of the secondary in five degrees of freedom.

  10. Insights into induced earthquakes and aftershock activity with in-situ measurements of seismic velocity variations in an active underground mine

    NASA Astrophysics Data System (ADS)

    Brenguier, F.; Olivier, G.; Campillo, M.; Roux, P.; Shapiro, N.; Lynch, R.

    2015-12-01

    The behaviour of the crust shortly after large earthquakes has been the subject of numerous studies, but many co- and post-seismic processes remain poorly understood. Damage and healing of the bulk rock mass, post-seismic deformation and the mechanisms of earthquake triggering are still not well understood. These processes are important to properly model and understand the behaviour of faults and earthquake cycles.In this presentation, we will show how in-situ measurements of seismic velocity variations have given new insights into these co- and post-seismic processes. An experiment was performed where a blast was detonated in a tunnel in an underground mine, while seismic velocity variations were accurately (0.005 %) measured with ambient seismic noise correlations. Additionally, aftershock activity was examined and the influence of the removal of a piece of solid rock was estimated with elastic static stress modelling. The majority of the aftershocks were delayed with respect to the passing of the dynamic waves from the blast, while the locations of the aftershocks appeared clustered and not homogeneously spread around the blast location. A significant velocity drop is visible during the time of the blast, which is interpreted as co-seismic damage and plastic deformation. These non-elastic effects are healed by the confining stresses over a period of 5 days until the seismic velocity converges to a new baseline level. The instantaneous weakening and gradual healing observed from the velocity variations are qualitatively similar to results reported in laboratory studies. The change in the baseline level of the seismic velocity before and after the blast indicate a change in the static stress that is comparable to the results of elastic static stress modelling. The differences between the elastic model predictions and the seismic velocity variations could be due to zones of fractured rock, indicated by the spatial clustering of the aftershocks, that are not

  11. Using RST approach and EOS-MODIS radiances for monitoring seismically active regions: a study on the 6 April 2009 Abruzzo earthquake

    NASA Astrophysics Data System (ADS)

    Pergola, N.; Aliano, C.; Coviello, I.; Filizzola, C.; Genzano, N.; Lacava, T.; Lisi, M.; Mazzeo, G.; Tramutoli, V.

    2010-02-01

    In the last few years, Robust Satellite data analysis Techniques (RST) have been proposed and successfully applied for monitoring major natural and environmental risks. Among the various fields of application, RST analysis has been used as a suitable tool for satellite TIR surveys in seismically active regions, devoted to detect and monitor thermal anomalies possibly related to earthquake occurrence. In this work, RST has been applied, for the first time, to thermal infrared observations collected by MODIS (Moderate Resolution Imaging Spectroradiometer) - the sensor onboard EOS (Earth Observing System) satellites - in the case of Abruzzo (Italy) earthquake occurred on 6 April 2009 (ML~5.8). First achievements, shown in this work, seem to confirm the sensitivity of the proposed approach in detecting perturbations of the Earth's emission thermal field few days before the event. The reliability of such results, based on the analysis of 10 years of MODIS observations, seems to be supported by the results achieved analyzing the same area in similar observation conditions but in seismically unperturbed periods (no earthquakes with ML≥5) that will be also presented.

  12. Shear-wave reflection seismics as bridge between georadar and deeper subsurface surveying - a case study for quick-clay landslides in Sweden

    NASA Astrophysics Data System (ADS)

    Krawczyk, Charlotte M.; Polom, Ulrich; Malehmir, Alireza; Bastani, Mehrdad

    2013-04-01

    As part of a joint project studying clay-related landslides in Nordic countries, we successfully tested the use of shear-wave reflection seismics to survey shallow structures that are known to be related to quick-clay landslide processes. Co-sponsored via the Society of Exploration Geophysicists (SEG) program 'Geoscientists Without Borders (GWB)', several international groups apply a suite of applied geophysical and geotechnical methods to understand structural and physical conditions and the conditioning of this type of liquefaction. For this purpose, three 2D profiles were recorded in Frastad, southern Sweden, above the main slide plane area. Using a 120 m long streamer of 120 SH-geophones at 1 m spacing, and the ELVIS micro-vibrator as source, shear-wave data of very high quality were gathered, allowing a vertical resolution of 1 m and less. The longest profile along a paved road shows clear internal structuring of the up to 50 m thick marine sediments as well as strong undulations of top basement underneath. Different sedimentary sequences can be distinguished, and the quick clay sequence is interpreted in 15-20 m depth, which correlates well with the height of the most recent scarp. The sedimentary shear wave velocities suggest extremely low values of 100-120 m/s, which geotechnically prohibits building areas. In addition, test measurements on a stubble field showed the first time that the suppression of Love waves is not only restricted to paved surfaces and may also be achieved if reflection contrasts and low dispersion allow a suitable data processing. This opens new possibilities for a wide range of applications and specialized equipment adaptions with respect to reflection seismic surveying. In addition, the gap between structural data from georadar and P-wave seismic can be closed.

  13. 77 FR 58255 - Takes of Marine Mammals Incidental to Specified Activities; Marine Geophysical Survey off the...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-09-19

    ... National Environmental Policy Act, 42 U.S.C. 4321 et seq. Marine Seismic Survey in the Pacific Ocean off Central California, 2012'' (EA). NSF's EA incorporates a draft ``Environmental Assessment of Marine... (Lissodelphis borealis). waters. California/Oregon/ Washington stock. Risso's dolphin (Grampus Deep water,...

  14. 76 FR 37066 - Takes of Marine Mammals Incidental to Specified Activities; Marine Geophysical Survey in the...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-24

    ... August 2011 (76 FR 33246; June 8, 2011) contained errors in Table 2 regarding the occurrence and... in Federal Register document 76 FR 33246 (pages 33250-33251) has been revised to read as follows... in or near the proposed seismic survey areas. This document presents a new table with...

  15. U.S. Geological Survey land remote sensing activities

    USGS Publications Warehouse

    Frederick, Doyle G.

    1983-01-01

    The U.S. Geological Survey (USGS) and the Department of the Interior (DOI) were among the earliest to recognize the potential applications of satellite land remote sensing for management of the country's land and water resources…not only as a user but also as a program participant responsible for final data processing, product generation, and data distribution. With guidance from Dr. William T. Pecora, who was the Survey's Director at that time and later Under Secretary of Interior, the Earth Resources Observation Systems (EROS) Program was established in 1966 as a focal point for these activities within the Department. Dr. Pecora was among the few who could envision a role for the Survey and the Department as active participants in programs yet to come--like the Landsat, Magsat, Seasat and, most recently, Shuttle Imaging Radar programs.

  16. Observed inflation-deflation cycles at Popocatepetl volcano using tiltmeters and its possible correlation with regional seismic activity in Mexico

    NASA Astrophysics Data System (ADS)

    Contreras Ruiz Esparza, M. G., Sr.; Jimenez Velazquez, J. C., Sr.; Valdes Gonzalez, C. M., Sr.; Reyes Pimentel, T. A.; Galaviz Alonso, S. A.

    2014-12-01

    Popocatepetl, the smoking mountain, is a stratovolcano located in central Mexico with an elevation of 5450 masl. The active volcano, close to some of the largest urban centers in Mexico - 60 km and 30 km far from Mexico City and Puebla, respectively - poses a high hazard to an estimated population of 500 thousand people living in the vicinity of the edifice. Accordingly, in July 1994 the Popocatepetl Volcanological Observatory (POVO) was established. The observatory is operated and supported by the National Center for Disaster Prevention of Mexico (CENAPRED), and is equipped to fully monitor different aspects of the volcanic activity. Among the instruments deployed, we use in this investigation two tiltmometers and broad-band seismometers at two sites (Chipiquixtle and Encinos), which send the information gathered continuously to Mexico City.In this research, we study the characteristics of the tiltmeters signals minutes after the occurrence of certain earthquakes. The Popocatepetl volcano starts inflation-deflation cycles due to the ground motion generated by events located at certain regions. We present the analysis of the tiltmeters and seismic signals of all the earthquakes (Mw>5) occurred from January 2013 to June 2014, recorded at Chipiquixtle and Encinos stations. First, we measured the maximum tilt variation after each earthquake. Next, we apply a band-pass filter for different frequency ranges to the seismic signals of the two seismic stations, and estimated the total energy of the strong motion phase of the seismic record. Finally, we compared both measurements and observed that the maximum tilt variations were occurring when the maximum total energy of the seismic signals were in a specific frequency range. We also observed that the earthquake records that have the maximum total energy in that frequency range were the ones with a epicentral location south-east of the volcano. We conclude that our observations can be used set the ground for an early

  17. Use of Seismic and Magnetic Surveys in a Regional Geophysical Study for Geothermal Exploration in NE Alberta, Canada

    NASA Astrophysics Data System (ADS)

    Poureslami Ardakani, E.; Schmitt, D. R.; Moeck, I.

    2012-12-01

    NE Alberta hosts many producing oil sand projects. These projects require large amounts of thermal energy to produce most of which is currently provided by burning natural gas; and this increases the greenhouse gas footprint to producing such hydrocarbons. One possible solution is to instead use geothermal heat directly with hot fluids produced using Engineered Geothermal Systems (EGS). Geothermal exploration always starts with broad geological structure reconnaissance of the area. Unfortunately, the larger geological context particularly beneath those relatively shallow depths (typically less than 400 m) of interest to hydrocarbon exploration, is still poorly understood. As such, we have selected a rectangular area of 22000 km2 extending across 56.25 to 57.12N and 111.92 to 113.52W that we refer to as the Athabasca region. . The main two categories of data which are in used consist of over 600 km seismic reflection profiles and 22,000 km2 high resolution aeromagnetic (HRAM) data. Also there is a large amount of available well-logs from 1,000 boreholes in this area that have a key role in interpretation of seismic profiles. These integrated data sets are used for outlining sedimentary basin, mapping geological formation tops, locating fault zones and other structural lineaments, finding true depth of metamorphic basement and Curie point, and finally building a geological model of the region. To date all the formation tops are mapped through the area and picked on the seismic profiles. HRAM data is gridded using minimum curvature method. Some structural lineaments are picked on the HRAM data including a great NE-SW fault zone which is in agreement with seismic and well-logs. Additionally, the region hosts interesting geological features such as channels, pinnacle reefs and unconformities that are distinguishable on seismic profiles. Any of these findings help us to get a better view of the region for geothermal exploration.

  18. 2013 East Bay Seismic Experiment (EBSE): implosion data, Hayward, Calif

    USGS Publications Warehouse

    Catchings, Rufus D.; Strayer, Luther M.; Goldman, Mark R.; Criley, Coyn J.; Garcia, Susan; Sickler, Robert R.; Catchings, Marisol K.; Chan, Joanne; Gordon, Leslie C.; Haefner, Scott; Blair, James Luke; Gandhok, Gini; Johnson, Michaela R.

    2015-01-01

    In August 2013, the California State University, East Bay (CSUEB) in Hayward, California imploded a 13-story building (Warren Hall) that was deemed unsafe because of its immediate proximity to the active trace of the Hayward Fault. The U.S. Geological Survey (USGS) and the CSUEB collaborated on a program to record the seismic waves generated by the collapse of the building. We refer to this collaboration as the East Bay Seismic Experiment (EBSE). The principal objective of recording the seismic energy was to observe ground shaking as it radiated from the source, but the data also may be useful for other purposes. For example, the seismic data may be useful in evaluating the implosion process as it relates to structural engineering purposes. This report provides the metadata needed to utilize the seismic data.

  19. Modelling Active Faults in Probabilistic Seismic Hazard Analysis (PSHA) with OpenQuake: Definition, Design and Experience

    NASA Astrophysics Data System (ADS)

    Weatherill, Graeme; Garcia, Julio; Poggi, Valerio; Chen, Yen-Shin; Pagani, Marco

    2016-04-01

    The Global Earthquake Model (GEM) has, since its inception in 2009, made many contributions to the practice of seismic hazard modeling in different regions of the globe. The OpenQuake-engine (hereafter referred to simply as OpenQuake), GEM's open-source software for calculation of earthquake hazard and risk, has found application in many countries, spanning a diversity of tectonic environments. GEM itself has produced a database of national and regional seismic hazard models, harmonizing into OpenQuake's own definition the varied seismogenic sources found therein. The characterization of active faults in probabilistic seismic hazard analysis (PSHA) is at the centre of this process, motivating many of the developments in OpenQuake and presenting hazard modellers with the challenge of reconciling seismological, geological and geodetic information for the different regions of the world. Faced with these challenges, and from the experience gained in the process of harmonizing existing models of seismic hazard, four critical issues are addressed. The challenge GEM has faced in the development of software is how to define a representation of an active fault (both in terms of geometry and earthquake behaviour) that is sufficiently flexible to adapt to different tectonic conditions and levels of data completeness. By exploring the different fault typologies supported by OpenQuake we illustrate how seismic hazard calculations can, and do, take into account complexities such as geometrical irregularity of faults in the prediction of ground motion, highlighting some of the potential pitfalls and inconsistencies that can arise. This exploration leads to the second main challenge in active fault modeling, what elements of the fault source model impact most upon the hazard at a site, and when does this matter? Through a series of sensitivity studies we show how different configurations of fault geometry, and the corresponding characterisation of near-fault phenomena (including

  20. Increasing background seismicity and dynamic triggering behaviors with nearby mining activities around Fangshan Pluton in Beijing, China

    NASA Astrophysics Data System (ADS)

    Wang, Weijun; Meng, Xiaofeng; Peng, Zhigang; Chen, Qi-Fu; Liu, Ning

    2015-08-01

    Dynamic triggering in western Fangshan Pluton, Beijing, China, has been repeatedly identified, but previous studies are limited by sparse seismic station coverage. Here we systematically analyze continuous waveforms recorded by both permanent stations and a temporary seismic network 40 days before and after the 11 March 2011 Mw 9.1 Tohoku-Oki and the 14 April 2012 Mw 8.6 Indian Ocean earthquakes. We first build a template database using a short-term average to long-term average method. Next, we apply the matched filter technique that cross correlates the template waveforms with continuous data to detect additional seismic events. Overall, we detect 1956 and 950 seismic events around the Tohoku-Oki and Indian Ocean main shocks, respectively. Most detected events are shallow (<5 km) and clustered at Beiling Syncline in western Fangshan Pluton, which is adjacent to a running coalmine. Seven and 10 events are detected during the large-amplitude surface waves of the two main shocks, respectively, but no similar burst is detected following their major foreshock and aftershocks. Multiple statistical tests indicate that the short-term bursts after the two main shocks are dynamically triggered. We suggest that mining-related activities may perturb the subsurface stress conditions and hence make the region more susceptible for dynamic triggering than other places.

  1. Crustal structure during active rifting in the central Salton Trough, California, constrained by the Salton Seismic Imaging Project (SSIP)

    NASA Astrophysics Data System (ADS)

    Han, L.; Hole, J. A.; Stock, J. M.; Fuis, G. S.; Driscoll, N. W.; Kell, A. M.; Kent, G.; Harding, A. J.; Gonzalez-Fernandez, A.; Lazaro-Mancilla, O.

    2013-12-01

    Seismic refraction and reflection travel times from the Salton Seismic Imaging Project (SSIP) were used to constrain crustal structure during active continental rifting in the central Salton Trough, California. SSIP, funded by NSF and USGS, acquired seismic data in and across the Salton Trough in 2011 to investigate rifting processes at the northern end of the Gulf of California extensional province and earthquake hazards at the southern end of the San Andreas Fault system. Seven lines of refraction and low-fold reflection data were acquired onshore, two lines and a grid of airgun and OBS data were acquired in the Salton Sea, and onshore-offshore data were recorded. North American lithosphere in the central Salton Trough appears to have been rifted apart and replaced by new crust added by magmatism from below and sedimentation from above. Ongoing active rifting of this new crust is manifested by shallow (<10km depth) seismicity in the oblique Brawley Seismic Zone (connecting the Imperial and San Andreas transform faults), the small Salton Buttes volcanoes, and very high heat flow that enables geothermal energy production. Analyses of the onshore-offshore seismic line that extends along the axis of the Salton Trough, parallel to the direction of plate motion, constrains rifted crustal structure. Crystalline basement (~5 km/s) generally occurs at ~4 km depth, but is at 2-3 km depth in a localized region beneath the Salton Buttes and Salton Sea geothermal field. This crystalline rock is interpreted to be late Pliocene to Quaternary Colorado River sediment that has been metamorphosed by high heat flow to a depth of at least 10km. The shallower basement under the volcanic and geothermal field is due to more intense metamorphism and hydrothermal alteration in this region of extreme heat flow. Faster velocity (6.2-6.4 km/s) observed at 10-13 km depth might be the remains of ruptured pre-existing crust or might be produced by deeper magmatism. Seismic travel times indicate

  2. Marketing Universities: A Survey of Student Recruitment Activities

    ERIC Educational Resources Information Center

    Murphy, Patrick E.; McGarrity, Richard A.

    1978-01-01

    Admissions officers of 350 private colleges and universities were surveyed to ascertain their understanding of the term "marketing," current use of promotional (advertising and personal selling) activities, market segmentation approaches, and their product (i.e., academic programs) development and differentiation strategies. The mail questionnaire…

  3. 77 FR 55487 - Agency Information Collection Activities; Voluntary Customer Survey

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-09-10

    ... SECURITY U.S. Customs and Border Protection Agency Information Collection Activities; Voluntary Customer Survey AGENCY: U.S. Customs and Border Protection, Department of Homeland Security. ACTION: 30-Day notice.... Customs and Border Protection (CBP) of the Department of Homeland Security will be submitting...

  4. Jenkins Activity Survey Scores among Women of Different Occupations.

    ERIC Educational Resources Information Center

    Morell, Marie A.; Katkin, Edward S.

    1982-01-01

    Studied prevalence of Type A behavior of female professionals, nonprofessionals, homemakers and students. Professionals had significantly higher scores than homemakers on Type A, Job Involvement, Speed and Impatience, and Hard-Driving and Competitive scales of the Jenkins Activity Survey. Type A behavior was not related to family history. (Author)

  5. 75 FR 47607 - Agency Information Collection Activities: Voluntary Customer Survey

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-06

    ... agencies. This proposed information collection was previously published in the Federal Register (75 FR... SECURITY U.S. Customs and Border Protection Agency Information Collection Activities: Voluntary Customer... accordance with the Paperwork Reduction Act: Voluntary Customer Survey. This is a new collection...

  6. Survey of City/County Drug Abuse Activities 1972.

    ERIC Educational Resources Information Center

    Drug Abuse Council, Inc., Washington, DC.

    This monograph is the second of a two-part report delineating state and local government activities and programs in the area of drug abuse. Presented here are the efforts of cities and counties to control drug abuse, accompanied by comparisons with state actions where appropriate. A survey instrument was developed by the Drug Abuse Council, Inc.…

  7. Report for borehole explosion data acquired in the 1999 Los Angeles Region Seismic Experiment (LARSE II), Southern California: Part I, description of the survey

    USGS Publications Warehouse

    Fuis, Gary S.; Murphy, Janice M.; Okaya, David A.; Clayton, Robert W.; Davis, Paul M.; Thygesen, Kristina; Baher, Shirley A.; Ryberg, Trond; Benthien, Mark L.; Simila, Gerry; Perron, J. Taylor; Yong, Alan K.; Reusser, Luke; Lutter, William J.; Kaip, Galen; Fort, Michael D.; Asudeh, Isa; Sell, Russell; Van Schaack, John R.; Criley, Edward E.; Kaderabek, Ronald; Kohler, Will M.; Magnuski, Nickolas H.

    2001-01-01

    The Los Angeles Region Seismic Experiment (LARSE) is a joint project of the U.S. Geological Survey (USGS) and the Southern California Earthquake Center (SCEC). The purpose of this project is to produce seismic images of the subsurface of the Los Angeles region down to the depths at which earthquakes occur, and deeper, in order to remedy a deficit in our knowledge of the deep structure of this region. This deficit in knowledge has persisted despite over a century of oil exploration and nearly 70 years of recording earthquakes in southern California. Understanding the deep crustal structure and tectonics of southern California is important to earthquake hazard assessment. Specific imaging targets of LARSE include (a) faults, especially blind thrust faults, which cannot be reliably detected any other way; and (b) the depths and configurations of sedimentary basins. Imaging of faults is important in both earthquake hazard assessment but also in modeling earthquake occurrence. Earthquake occurrence cannot be understood unless the earthquake-producing "machinery" (tectonics) is known (Fuis and others, 2001). Imaging the depths and configurations of sedimentary basins is important because earthquake shaking at the surface is enhanced by basin depth and by the presence of sharp basin edges (Wald and Graves, 1998, Working Group on California Earthquake Probabilities, 1995; Field and others, 2001). (Sedimentary basins are large former valleys now filled with sediment eroded from nearby mountains.) Sedimentary basins in the Los Angeles region that have been investigated by LARSE include the Los Angeles, San Gabriel Valley, San Fernando Valley, and Santa Clarita Valley basins. The seismic imaging surveys of LARSE include recording of earthquakes (both local and distant earthquakes) along several corridors (or transects) through the Los Angeles region and also recording of man-made sources along these same corridors. Man-made sources have included airguns offshore and borehole

  8. Seismicity study of volcano-tectonic in and around Tangkuban Parahu active volcano in West Java region, Indonesia

    NASA Astrophysics Data System (ADS)

    Ry, Rexha V.; Priyono, A.; Nugraha, A. D.; Basuki, A.

    2016-05-01

    Tangkuban Parahu is one of the active volcano in Indonesia located about 15 km northern part of Bandung city. The objective of this study is to investigate the seismic activity in the time periods of January 2013 to December 2013. First, we identified seismic events induced by volcano-tectonic activities. These micro-earthquake events were identified as having difference of P-wave and S-wave arrival times less than three seconds. Then, we constrained its location of hypocenter to locate the source of the activities. Hypocenter determination was performed using adaptive simulated annealing method. Using these results, seismic tomographic inversions were conducted to image the three-dimensional velocity structure of Vp, Vs, and the Vp/Vs ratio. In this study, 278 micro-earthquake events have been identified and located. Distribution of hypocenters around Tangkuban Parahu volcano forms an alignment structure and may be related to the stress induced by magma below, also movement of shallow magma below Domas Crater. Our preliminary tomographic inversion results indicate the presences of low Vp, high Vs, and low Vp/Vs ratio that associate to accumulated young volcanic eruption products and hot material zones.

  9. 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

  10. 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 older earthquake, but rather along the edge of the gouge. According to the gouge statistics of the whole fault zone, seismic events have the obvious tendency towards the foot wall, and the thickness of gouge is proportional to the activity of the fault, indicating that the width of fault zone is directly related to the number and evolution history of earthquakes . Repeated earthquakes maybe the main cause for the formation of the Longmenshan Moutains

  11. Understanding seismic design criteria for Japanese Nuclear Power Plants

    SciTech Connect

    Park, Y.J.; Hofmayer, C.H.; Costello, J.F.

    1995-04-01

    This paper summarizes the results of recent survey studies on the seismic design practice for nuclear power plants in Japan. The seismic design codes and standards for both nuclear as well as non-nuclear structures have been reviewed and summarized. Some key documents for understanding Japanese seismic design criteria are also listed with brief descriptions. The paper highlights the design criteria to determine the seismic demand and component capacity in comparison with U.S. criteria, the background studies which have led to the current Japanese design criteria, and a survey of current research activities. More detailed technical descriptions are presented on the development of Japanese shear wall equations, design requirements for containment structures, and ductility requirements.

  12. Understanding seismic design criteria for Japanese nuclear power plants

    SciTech Connect

    Park, Y.J.; Hofmayer, C.H.; Costello, J.F.

    1994-12-31

    This paper summarizes the results of recent survey studies on the seismic design practice for nuclear power plants in Japan. The seismic design codes and standards for both nuclear as well as non-nuclear structures have been reviewed and summarized. Some key documents for understanding Japanese seismic design criteria are also listed with brief descriptions. The paper highlights the design criteria to determine the seismic demand and component capacity in comparison with US criteria, the background studies which have led to the current Japanese design criteria, and a survey of current research activities. More detailed technical descriptions are presented on the development of Japanese shear wall equations, design requirements for containment structures, and ductility requirements.

  13. 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.

  14. Results From NICLAKES Survey of Active Faulting Beneath Lake Nicaragua, Central American Volcanic Arc

    NASA Astrophysics Data System (ADS)

    Funk, J.; Mann, P.; McIntosh, K.; Wulf, S.; Dull, R.; Perez, P.; Strauch, W.

    2006-12-01

    In May of 2006 we used a chartered ferry boat to collect 520 km of seismic data, 886 km of 3.5 kHz subbottom profiler data, and 35 cores from Lake Nicaragua. The lake covers an area of 7700 km2 within the active Central American volcanic arc, forms the largest lake in Central America, ranks as the twentieth largest freshwater lake in the world, and has never been previously surveyed or cored in a systematic manner. Two large stratovolcanoes occupy the central part of the lake: Concepcion is presently active, Maderas was last active less than 2000 years ago. Four zones of active faulting and doming of the lake floor were mapped with seismic and 3.5 kHz subbottom profiling. Two of the zones consist of 3-5-km-wide, 20-30-km-long asymmetric rift structures that trend towards the inactive cone of Maderas Volcano in a radial manner. The northeastern rift forms a 20-27-m deep depression on the lake bottom that is controlled by a north-dipping normal fault. The southwestern rift forms a 25-35-m deep depression controlled by a northeast-dipping normal fault. Both depressions contain mound-like features inferred to be hydrothermal deposits. Two zones of active faulting are associated with the active Concepcion stratovolcano. A 600-m-wide and 6-km-long fault bounded horst block extends westward beneath the lake from a promontory on the west side of the volcano. Like the two radial rift features of Maderas, the horst points roughly towards the active caldera of Concepcion. A second north-south zone of active faulting, which also forms a high, extends off the north coast of Concepcion and corresponds to a localized zone of folding and faulting mapped by previous workers and inferred by them to have formed by gravitational spreading of the flank of the volcano. The close spatial relation of these faults to the two volcanic cones in the lake suggests that the mechanism for faulting is a result of either crustal movements related to magma intrusion or gravitational sliding and is

  15. Electric and magnetic phenomena observed before the volcano-seismic activity in 2000 in the Izu Island Region, Japan

    PubMed Central

    Uyeda, S.; Hayakawa, M.; Nagao, T.; Molchanov, O.; Hattori, K.; Orihara, Y.; Gotoh, K.; Akinaga, Y.; Tanaka, H.

    2002-01-01

    Significant anomalous changes in the ultra low frequency range (≈0.01 Hz) were observed in both geoelectric and geomagnetic fields before the major volcano-seismic activity in the Izu Island region, Japan. The spectral intensity of the geoelectric potential difference between some electrodes on Niijima Island and the third principal component of geomagnetic field variations at an array network in Izu Peninsula started to increase from a few months before the onset of the volcano-seismic activity, culminating immediately before nearby magnitude 6 class earthquakes. Appearance of similar changes in two different measurements conducted at two far apart sites seems to provide information supporting the reality of preseismic electromagnetic signals. PMID:12032286

  16. Tsujal Marine Survey: Crustal Characterization of the Rivera Plate-Jalisco Block Boundary and its Implications for Seismic and Tsunami Hazard Assessment

    NASA Astrophysics Data System (ADS)

    Bartolome, R.; Danobeitia, J.; Barba, D. C., Sr.; Nunez-Cornu, F. J.; Cameselle, A. L.; Estrada, F.; Prada, M.; Bandy, W. L.

    2014-12-01

    During the spring of 2014, a team of Spanish and Mexican scientists explored the western margin of Mexico in the frame of the TSUJAL project. The two main objectives were to characterize the nature and structure of the lithosphere and to identify potential sources triggering earthquakes and tsunamis at the contact between Rivera plate-Jalisco block with the North American Plate. With these purposes a set of marine geophysical data were acquired aboard the RRS James Cook. This work is focus in the southern part of the TSUJAL survey, where we obtain seismic images from the oceanic domain up to the continental shelf. Thus, more than 800 km of MCS data, divided in 7 profiles, have been acquired with a 6km long streamer and using an air-gun sources ranging from 5800 c.i. to 3540 c.i. Furthermore, a wide-angle seismic profile of 190 km length was recorded in 16 OBS deployed perpendicular to the coast of Manzanillo. Gravity and magnetic, multibeam bathymetry and sub-bottom profiler data were recorded simultaneously with seismic data in the offshore area. Preliminary stacked MCS seismic sections reveal the crustal structure in the different domains of the Mexican margin. The contact between the Rivera and NA Plates is observed as a strong reflection at 6 s two way travel time (TWTT), in a parallel offshore profile (TS01), south of Manzanillo. This contact is also identified in a perpendicular profile, TS02, along a section of more than 100 km in length crossing the Rivera transform zone, and the plate boundary between Cocos and Rivera Plates. Northwards, offshore Pto. Vallarta, the MCS data reveals high amplitude reflections at around 7-8.5 s TWTT, roughly 2.5-3.5 s TWTT below the seafloor, that conspicuously define the subduction plane (TS06b). These strong reflections which we interpret as the Moho discontinuity define the starting bending of subduction of Rivera Plate. Another clear pattern observed within the first second of the MCS data shows evidences of a bottom

  17. 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

    chimney debris and thick deposits of oxidized hydrothermal sediment extends 200 m south. Large extinct chimneys (5-10 m high, 2-4 m in diameter) along the sulfide ridge indicate that Sasquatch was once far more active, though the current spatial extent and size of active chimneys are significantly smaller than the other four Endeavour vent fields. We suggest that seismic activity in 1999-2000 is responsible for renewed hydrothermal activity at Sasquatch, and that the field may have been further impacted by an earthquake swarm in 2005. Upon its discovery in 2000, diffuse flow was widespread at the field and along the adjacent ridge. Subsequent visits in 2002 and 2004 observed far less bacterial mat, suggesting a decrease in the amount of diffuse flow. In February-March 2005, a swarm of >3,700 earthquakes occurred ~35 km NNW of the field (http://www.pmel.noaa.gov/vents/acoustics/seismicity/nepac/endeav0205.html) and may have contributed to the initiation and growth of several new "beehive" vent structures observed in September 2005 and 2006. References Johnson, H.P., M. Hutnak, R.P. Dziak, C.G. Fox, I. Urcuyo, J.P. Cowen, J. Nabelek, and C. Fisher (2000), Earthquake-induced changes in a hydrothermal system on the Juan de Fuca mid-ocean ridge, Nature 407, 174-177. Lilley, M. D., D. A. Butterfield, J. E. Lupton, and E. J. Olson (2003), Magmatic events can produce rapid changes in hydrothermal chemistry, Nature 422, 878-881. Proskurwoski, G., M. D. Lilley and T. A. Brown (2004), Isotopic evidence of magmatism and seawater bicarbonate removal at the Endeavour hydrothermal system, Ear. Planet. Sci. Let. 225, 1-2, 53-61.

  18. July 1973 ground survey of active Central American volcanoes

    NASA Technical Reports Server (NTRS)

    Stoiber, R. E. (Principal Investigator); Rose, W. I., Jr.

    1973-01-01

    The author has identified the following significant results. Ground survey has shown that thermal anomalies of various sizes associated with volcanic activity at several Central American volcanoes should be detectable from Skylab. Anomalously hot areas of especially large size (greater than 500 m in diameter) are now found at Santiaguito and Pacaya volcanoes in Guatemala and San Cristobal in Nicaragua. Smaller anomalous areas are to be found at least seven other volcanoes. This report is completed after ground survey of eleven volcanoes and ground-based radiation thermometry mapping at these same points.

  19. 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.

  20. Short-Period Seismic Noise in Vorkuta (Russia)

    SciTech Connect

    Kishkina, S B; Spivak, A A; Sweeney, J J

    2008-05-15

    Cultural development of new subpolar areas of Russia is associated with a need for detailed seismic research, including both mapping of regional seismicity and seismic monitoring of specific mining enterprises. Of special interest are the northern territories of European Russia, including shelves of the Kara and Barents Seas, Yamal Peninsula, and the Timan-Pechora region. Continuous seismic studies of these territories are important now because there is insufficient seismological knowledge of the area and an absence of systematic data on the seismicity of the region. Another task of current interest is the necessity to consider the seismic environment in the design, construction, and operation of natural gas extracting enterprises such as the construction of the North European Gas Pipeline. Issues of scientific importance for seismic studies in the region are the complex geodynamical setting, the presence of permafrost, and the complex tectonic structure. In particular, the Uralian Orogene (Fig. 1) strongly affects the propagation of seismic waves. The existing subpolar seismic stations [APA (67,57{sup o}N; 33,40{sup o}E), LVZ (67,90{sup o}N; 34,65{sup o}E), and NRIL (69,50{sup o}N; 88,40{sup o}E)] do not cover the extensive area between the Pechora and Ob Rivers (Fig. 1). Thus seismic observations in the Vorkuta area, which lies within the area of concern, represent a special interest. Continuous recording at a seismic station near the city of Vorkuta (67,50{sup o}N; 64,11{sup o}E) [1] has been conducted since 2005 for the purpose of regional seismic monitoring and, more specifically, detection of seismic signals caused by local mining enterprises. Current surveys of local seismic noise [7,8,9,11], are particularly aimed at a technical survey for the suitability of the site for installation of a small-aperture seismic array, which would include 10-12 recording instruments, with the Vorkuta seismic station as the central element. When constructed, this seismic

  1. Catalog of seismic records obtained in support of the ERDA/Nevada Operations Office, October 1963 through June 1976

    USGS Publications Warehouse

    Navarro, R.; Sembera, E.D.; Jungblut, W.L.

    1977-01-01

    The United States Geological Survey (USGS), Branch of Earthquake Hazards (BEH), Las Vegas, Nevada has provided ERDA, Nevada Operations Office, with seismic monitoring support to the underground nuclear weapons test program conducted at the Nevada Test Site (NTS) since September 1961. Activities from September 15, 1961 to September 13, 1963 are summarized in the report, "Seismic Dats Summary Nuclear Detonation Program, 1961 thru 1963", (Mickey and Shugart 1964) which lists seismic records obtained from all announced underground nuclear tests conducted during that period.

  2. Locating Desired Source Rocks by Using Shallow Ground Penetrating Radar and Seismic Survey Methods in western Washington, Pacific Northwest of the U.S

    NASA Astrophysics Data System (ADS)

    Cakir, R.; Meng, X.; Butler, Q.; Jenkins, J.; Keck, J.; Walsh, T. J.

    2015-12-01

    The Washington State Department of Natural Resources (WADNR) manages 2.1 million acres of forested state trust lands in Washington. WADNR sells timber and other agricultural products to help fund local services and the construction of institutions such as public schools and universities. Quality of rocks used as a surface on the roads built to access the timber is the essential and selecting appropriate rock quarry locations is challenging. Traditional borehole drilling methods only provide information from discrete locations. The study was conducted in the Capitol Forest area of western Washington. In our previous study, we suggested that a combination of P-wave seismic and ground penetrating radar (GPR) can be a rapid, comprehensive and cost effective alternative for identifying desired rock sources. In this study, we further improved upon that method and accomplished the following: 1) rock quality at a relatively fine resolution was distinguished and 2) the spatial variability of the rock was identified. Both 450 MHz and 80 MHz GPR antennas were used to obtain high resolution radargrams in the near-surface zone with 5m maximum penetration depth and lower resolution radargrams in the deeper subsurface zone with about 20m maximum penetration depth. We then correlated the GPR radargrams with P-wave velocities using the refraction survey data as well as S-wave velocities, estimated using Multi-Channel Analysis of Surface Waves (MASW) survey data. Additionally, nearby test pits and boreholes (maximum depth = 15 meters) were used to confirm the geophysical measurements. Our study results demonstrate that the combination of GPR, using the two antennas, and seismic surveys provides very useful subsurface information regarding quality and spatial distribution of the rocks beneath the overburden. Subsurface images gathered from these combined geophysical methods do assist quarry operators to rapidly locate the desired rock sources.

  3. U.S. Geological Survey activities, fiscal year 1981

    USGS Publications Warehouse

    ,

    1982-01-01

    This U.S. Geological Survey Activities report for fiscal year 1981 presents a summary of the work performed between October 1, 1980 and September 30, 1981. The main sections of this report are: (1) The Year in Review; a brief overview of the significant events of the Geological Survey during fiscal year 1980; (2) Perspectives; essays focusing on specific events (rather than scientific topics) and programs involving multi-Division participation; (3) Missions, Organization, and Budget; a description of the Geological Survey 's major duties and assignments and of the organizational structure that supports its missions; and (4) Division Chapters; a description of the significant accomplishments (rather than a comprehensive program by program discussion) of each of the eight operating Divisions and Offices. Also included are supplementary information regarding key personnel, cooperators, and selected summary budgetary tables. (USGS)

  4. Compilation of selected faults and lineaments that may be relevant to a study of seismic activity in southern Nevada and part of adjacent California

    SciTech Connect

    Bucknam, R.C.

    1983-02-01

    The enclosed preliminary map shows selected prominent faults and regional topographic lineaments that may be relevant to a study of known or potential seismic activity in the California-southern Nevada region surrounding the Nevada Test Site.

  5. Active and passive electrical and seismic time-lapse monitoring of earthen embankments

    NASA Astrophysics Data System (ADS)

    Rittgers, Justin Bradley

    In this dissertation, I present research involving the application of active and passive geophysical data collection, data assimilation, and inverse modeling for the purpose of earthen embankment infrastructure assessment. Throughout the dissertation, I identify several data characteristics, and several challenges intrinsic to characterization and imaging of earthen embankments and anomalous seepage phenomena, from both a static and time-lapse geophysical monitoring perspective. I begin with the presentation of a field study conducted on a seeping earthen dam, involving static and independent inversions of active tomography data sets, and self-potential modeling of fluid flow within a confined aquifer. Additionally, I present results of active and passive time-lapse geophysical monitoring conducted during two meso-scale laboratory experiments involving the failure and self-healing of embankment filter materials via induced vertical cracking. Identified data signatures and trends, as well as 4D inversion results, are discussed as an underlying motivation for conducting subsequent research. Next, I present a new 4D acoustic emissions source localization algorithm that is applied to passive seismic monitoring data collected during a full-scale embankment failure test. Acoustic emissions localization results are then used to help spatially constrain 4D inversion of collocated self-potential monitoring data. I then turn to time-lapse joint inversion of active tomographic data sets applied to the characterization and monitoring of earthen embankments. Here, I develop a new technique for applying spatiotemporally varying structural joint inversion constraints. The new technique, referred to as Automatic Joint Constraints (AJC), is first demonstrated on a synthetic 2D joint model space, and is then applied to real geophysical monitoring data sets collected during a full-scale earthen embankment piping-failure test. Finally, I discuss some non-technical issues related to

  6. Student Attitudes and Recommendations on Active Learning: A Student-Led Survey Gauging Course Effectiveness.

    ERIC Educational Resources Information Center

    Marbach-Ad, Gili; Seal, October; Sokolove, Phillip

    2001-01-01

    Describes an active learning approach used in an introductory biology class and evaluates the project with student surveys. Presents students' answers to survey questions. (Contains 16 references.) (YDS)

  7. Volcano-seismic activity before and after the Maule 2010 Earthquake (Southern Chile): a comparison between Llaima and Villarrica volcanoes

    NASA Astrophysics Data System (ADS)

    Mora-Stock, C.; Thorwart, M.; Wunderlich, T.; Bredemeyer, S.; Rabbel, W.

    2012-04-01

    Llaima and Villarrica are two of the most actives volcanoes in the Southern Volcanic Zone in the Chilean Andes, with different type of activity and edifice. Llaima is a close vent volcano with constant seismic activity, while Villarrica is an open vent volcano with lava lake at the summit and constant degassing. The relation between volcano eruptions following a great earthquake has been studied in different cases around the world, and it has been the case for the 1960 Valdivia earthquake in southern Chile, where Llaima and Villarrica presented eruptions on the following months to years. This study is focused on characterizing the volcano-seismic activity in the months before and after the M8.8 Maule earthquake on the 27th February 2010. Time series for tremors, long period and volcano tectonic events were obtained from the catalogue of the Volcanic Observatory of the Southern Andes (OVDAS in Spanish) and from the continuous record of the SFB 574 temporary volcanic network. In Villarrica volcano, peaks of activity of tremor and long period events were observed months prior to and after the earthquake, followed by degassing activity, which is consistent with an increase in the activity related to fluids (gas and magma). While in Llaima volcano, a high increase in the volcano tectonic activity was observed directly after the earthquake, consistent with a possible structural adjustment response. The values for pressure change and normal stress were calculated for the Maule earthquake (M8.8) giving results two orders of magnitude lower in comparison to the ones obtained for Valdivia earthquake (M9.5). Finally, these changes in the seismic behavior had lasted over a year, than it is possible to state that the Maule earthquake affected Llaima and Villarrica in some way due to static stress, but given the location and the insufficient critical state of both edifices, it was not possible to generate a great eruption.

  8. Archive of Digital Boomer Seismic Reflection Data Collected During USGS Field Activity 08LCA04 in Lakes Cherry, Helen, Hiawassee, Louisa, and Prevatt, Central Florida, September 2008

    USGS Publications Warehouse

    Harrison, Arnell S.; Dadisman, Shawn V.; Davis, Jeffrey B.; Flocks, James G.; Wiese, Dana S.

    2009-01-01

    From September 2 through 4, 2008, the U.S. Geological Survey and St. Johns River Water Management District (SJRWMD) conducted geophysical surveys in Lakes Cherry, Helen, Hiawassee, Louisa, and Prevatt, central Florida. This report serves as an archive of unprocessed digital boomer seismic reflection data, trackline maps, navigation files, GIS information, FACS logs, and formal FGDC metadata. Filtered and gained digital images of the seismic profiles are also provided. The archived trace data are in standard Society of Exploration Geophysicists (SEG) SEG-Y format (Barry and others, 1975) and may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU). Example SU processing scripts and USGS software for viewing the SEG-Y files (Zihlman, 1992) are also provided.

  9. Active shortening of the Cascadia forearc and implications for seismic hazards of the Puget Lowland

    USGS Publications Warehouse

    Johnson, S.Y.; Blakely, R.J.; Stephenson, W.J.; Dadisman, S.V.; Fisher, M.A.

    2004-01-01

    Margin-parallel shortening of the Cascadia forearc is a consequence of oblique subduction of the Juan de Fuca plate beneath North America. Strike-slip, thrust, and oblique crustal faults beneath the densely populated Puget Lowland accommodate much of this north-south compression, resulting in large crustal earthquakes. To better understand this forearc deformation and improve earthquake hazard, assessment, we here use seismic reflection surveys, coastal exposures of Pleistocene strata, potential-field data, and airborne laser swath mapping to document and interpret a significant structural boundary near the City of Tacoma. This boundary is a complex structural zone characterized by two distinct segments. The northwest trending, eastern segment, extending from Tacoma to Carr Inlet, is formed by the broad (??? 11.5 km), southwest dipping (??? 11??-2??) Rosedale monocline. This monocline raises Crescent Formation basement about 2.5 km, resulting in a moderate gravity gradient. We interpret the Rosedale monocline as a fault-bend fold, forming above a deep thrust fault. Within the Rosedale monocline, inferred Quaternary strata thin northward and form a growth triangle that is 4.1 to 6.6 km wide at its base, suggesting ??? 2-3 mm/yr of slip on the underlying thrust. The western section of the >40-km-long, north dipping Tacoma fault, extending from Hood Canal to Carr Inlet, forms the western segment of the Tacoma basin margin. Structural relief on this portion of the basin margin may be several kilometers, resulting in steep gravity and aeromagnetic anomalies. Quaternary structural relief along the Tacoma fault is as much as 350-400 m, indicating a minimum slip rate of about 0.2 mm/yr. The inferred eastern section of the Tacoma fault (east of Carr Inlet) crosses the southern part of the Seattle uplift, has variable geometry along strike, and diminished structural relief. The Tacoma fault is regarded as a north dipping backthrust to the Seattle fault, so that slip on a

  10. Seismic Activity Related to the 2002-200