Sensor Emplacement Techniques and Seismic Noise Analysis for USArray Transportable Array Seismic Stations

NASA Astrophysics Data System (ADS)

Frassetto, A.; Busby, R. W.; Hafner, K.; Woodward, R.; Sauter, A.

2013-12-01

In preparation for the upcoming deployment of EarthScope's USArray Transportable Array (TA) in Alaska, the National Science Foundation (NSF) has supported exploratory work on seismic station design, sensor emplacement, and communication concepts appropriate for this challenging high-latitude environment. IRIS has installed several experimental stations to evaluate different sensor emplacement schemes both in Alaska and in the lower-48 of the U.S. The goal of these tests is to maintain or enhance a station's noise performance while minimizing its footprint and the weight of the equipment, materials, and overall expense required for its construction. Motivating this approach are recent developments in posthole broadband seismometer design and the unique conditions for operating in Alaska, where there are few roads, cellular communications are scarce, most areas are only accessible by small plane or helicopter, and permafrost underlies much of the state. We will review the methods used for directly emplacing broadband seismometers in comparison to the current methods used for the lower-48 TA. These new methods primarily focus on using a portable drill to make a bored hole three to five meters, beneath the active layer of the permafrost, or by coring 1-2 meters deep into surface bedrock. Both methods are logistically effective in preliminary trials. Subsequent station performance has been assessed quantitatively using probability density functions summed from power spectral density estimates. These are calculated for the continuous time series of seismic data recorded for each channel of the seismometer. There are five test stations currently operating in Alaska. One was deployed in August 2011 and the remaining four in October 2012. Our results show that the performance of seismometers in Alaska with auger-hole or core-hole installations can sometimes exceed that of the quietest TA stations in the lower-48, particularly horizontal components at long periods. A

Multi-Use seismic stations offer strong deterrent to clandestine nuclear weapons testing

NASA Astrophysics Data System (ADS)

Hennet, C. B.; Van der Vink, G. E.; Richards, P. G.; Adushkin, V. V.; Kopnichev, Y. F.; Geary, R.

As the United States and other nations push for the signing of a Comprehensive Test Ban Treaty, representatives are meeting in Geneva this year to develop an International Seismic Monitoring System to verify compliance with the treaty's restrictions. In addition to the official monitoring system, regional networks developed for earthquake studies and basic research can provide a strong deterrent against clandestine testing. The recent release of information by the U.S. Department of Energy (DoE) on previously unannounced nuclear tests provides an opportunity to assess the ability of multi-use seismic networks to help monitor nuclear testing across the globe.Here we look at the extent to which the formerly unannounced tests were recorded and identified on the basis of publicly available seismographic data recorded by five seismic networks. The data were recorded by networks in southern Nevada and northern California at stations less than 1500 km from the Nevada Test Site (NTS), and two networks in the former Soviet Union at stations farther than 1500 km from the NTS.

Background noise spectra of global seismic stations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wada, M.M.; Claassen, J.P.

1996-08-01

Over an extended period of time station noise spectra were collected from various sources for use in estimating the detection and location performance of global networks of seismic stations. As the database of noise spectra enlarged and duplicate entries became available, an effort was mounted to more carefully select station noise spectra while discarding others. This report discusses the methodology and criteria by which the noise spectra were selected. It also identifies and illustrates the station noise spectra which survived the selection process and which currently contribute to the modeling efforts. The resulting catalog of noise statistics not only benefitsmore » those who model network performance but also those who wish to select stations on the basis of their noise level as may occur in designing networks or in selecting seismological data for analysis on the basis of station noise level. In view of the various ways by which station noise were estimated by the different contributors, it is advisable that future efforts which predict network performance have available station noise data and spectral estimation methods which are compatible with the statistics underlying seismic noise. This appropriately requires (1) averaging noise over seasonal and/or diurnal cycles, (2) averaging noise over time intervals comparable to those employed by actual detectors, and (3) using logarithmic measures of the noise.« less

New comprehensive standard seismic noise models and 3D seismic noise variation for Morocco territory, North Africa, obtained using seismic broadband stations

NASA Astrophysics Data System (ADS)

El Fellah, Younes; El-Aal, Abd El-Aziz Khairy Abd; Harnafi, Mimoun; Villaseñor, Antonio

2017-05-01

In the current work, we constructed new comprehensive standard seismic noise models and 3D temporal-spatial seismic noise level cubes for Morocco in north-west Africa to be used for seismological and engineering purposes. Indeed, the original global standard seismic noise models published by Peterson (1993) and their following updates by Astiz and Creager (1995), Ekström (2001) and Berger et al. (2003) had no contributing seismic stations deployed in North Africa. Consequently, this preliminary study was conducted to shed light on seismic noise levels specific to north-west Africa. For this purpose, 23 broadband seismic stations recently installed in different structural domains throughout Morocco are used to study the nature and characteristics of seismic noise and to create seismic noise models for Morocco. Continuous data recorded during 2009, 2010 and 2011 were processed and analysed to construct these new noise models and 3D noise levels from all stations. We compared the Peterson new high-noise model (NHNM) and low-noise model (NLNM) with the Moroccan high-noise model (MHNM) and low-noise model (MLNM). These new noise models are comparable to the United States Geological Survey (USGS) models in the short period band; however, in the period range 1.2 s to 1000 s for MLNM and 10 s to 1000 s for MHNM display significant variations. This variation is attributed to differences in the nature of seismic noise sources that dominate Morocco in these period bands. The results of this study have a new perception about permanent seismic noise models for this spectacular region and can be considered a significant contribution because it supplements the Peterson models and can also be used to site future permanent seismic stations in Morocco.

The 2017 Maple Creek Seismic Swarm in Yellowstone National Park

NASA Astrophysics Data System (ADS)

Pang, G.; Hale, J. M.; Farrell, J.; Burlacu, R.; Koper, K. D.; Smith, R. B.

2017-12-01

The University of Utah Seismograph Stations (UUSS) performs near-real-time monitoring of seismicity in the region around Yellowstone National Park in partnership with the United States Geological Survey and the National Park Service. UUSS operates and maintains 29 seismic stations with network code WY (short-period, strong-motion, and broadband) and records data from five other seismic networks—IW, MB, PB, TA, and US—to enhance the location capabilities in the Yellowstone region. A seismic catalog is produced using a conventional STA/LTA detector and single-event location techniques (Hypoinverse). On June 12, 2017, a seismic swarm began in Yellowstone National Park about 5 km east of Hebgen Lake. The swarm is adjacent to the source region of the 1959 MW 7.3 Hebgen Lake earthquake, in an area corresponding to positive Coulumb stress change from that event. As of Aug. 1, 2017, the swarm consists of 1481 earthquakes with 1 earthquake above magnitude 4, 8 earthquakes in the magnitude 3 range, 115 earthquakes in the magnitude 2 range, 469 earthquakes in the magnitude 1 range, 856 earthquakes in the magnitude 0 range, 22 earthquakes with negative magnitudes, and 10 earthquakes with no magnitude. Earthquake depths are mostly between 3 and 10 km and earthquake depth increases toward the northwest. Moment tensors for the 2 largest events (3.6 MW and 4.4. MW) show strike-slip faulting with T axes oriented NE-SW, consistent with the regional stress field. We are currently using waveform cross-correlation methods to measure differential travel times that are being used with the GrowClust program to generate high-accuracy relative relocations. Those locations will be used to identify structures in the seismicity and make inferences about the tectonic and magmatic processes causing the swarm.

Sensor Emplacement Techniques and Seismic Noise Analysis for USArray Transportable Array Seismic Stations

NASA Astrophysics Data System (ADS)

Busby, Robert; Frassetto, Andy; Hafner, Katrin; Woodward, Robert; Sauter, Allan

2013-04-01

In preparation for deployment of EarthScope's USArray Transportable Array (TA) in Alaska beginning in 2014, the National Science Foundation (NSF) is supporting exploratory work on seismic station design, sensor emplacement and communication concepts appropriate for the challenging high-latitude environment that is proposed for deployment. IRIS has installed several experimental stations to evaluate different sensor emplacement schemes both in Alaska and the lower-48 U.S. The goal of these tests is to maintain or enhance a station's noise performance while minimizing its footprint and the equipment, materials, and overall expense required for its construction. Motivating this approach are recent developments in posthole broadband seismometer design and the unique conditions for operating in Alaska, where there are few roads, cellular communications are scarce, most areas are only accessible by small plane or helicopter, and permafrost underlies much of the northern tundra. In this study we review our methods used for directly emplacing of broadband seismometers in comparison to the current methods used to deploy TA stations. These primarily focus on using an auger to drill three to five meters, beneath the active layer of the permafrost, or coring directly into surface bedrock to one meter depth using a portable drill. Both methods have proven logistically effective in trials. Subsequent station performance can be quantitatively assessed using probability density functions summed from power spectral density estimates. These are calculated for the continuous time series of seismic data recorded for each channel of the seismometer. There are five test stations currently operating in Alaska. One was deployed in August 2011 and the remaining four in October 2012. Our results show that the performance of seismometers in Alaska with auger-hole or core-hole installations equals or exceeds that of the quietest TA stations in the lower-48, particularly at long periods, and

Revision of IRIS/IDA Seismic Station Metadata

NASA Astrophysics Data System (ADS)

Xu, W.; Davis, P.; Auerbach, D.; Klimczak, E.

2017-12-01

Trustworthy data quality assurance has always been one of the goals of seismic network operators and data management centers. This task is considerably complex and evolving due to the huge quantities as well as the rapidly changing characteristics and complexities of seismic data. Published metadata usually reflect instrument response characteristics and their accuracies, which includes zero frequency sensitivity for both seismometer and data logger as well as other, frequency-dependent elements. In this work, we are mainly focused studying the variation of the seismometer sensitivity with time of IRIS/IDA seismic recording systems with a goal to improve the metadata accuracy for the history of the network. There are several ways to measure the accuracy of seismometer sensitivity for the seismic stations in service. An effective practice recently developed is to collocate a reference seismometer in proximity to verify the in-situ sensors' calibration. For those stations with a secondary broadband seismometer, IRIS' MUSTANG metric computation system introduced a transfer function metric to reflect two sensors' gain ratios in the microseism frequency band. In addition, a simulation approach based on M2 tidal measurements has been proposed and proven to be effective. In this work, we compare and analyze the results from three different methods, and concluded that the collocated-sensor method is most stable and reliable with the minimum uncertainties all the time. However, for epochs without both the collocated sensor and secondary seismometer, we rely on the analysis results from tide method. For the data since 1992 on IDA stations, we computed over 600 revised seismometer sensitivities for all the IRIS/IDA network calibration epochs. Hopefully further revision procedures will help to guarantee that the data is accurately reflected by the metadata of these stations.

Instrumentation Guidelines for the Advanced National Seismic System

USGS Publications Warehouse

Working Group on Instrumentation, Siting

2008-01-01

This document provides guidelines for the seismic-monitoring instrumentation used by long-term earthquake-monitoring stations that will sense ground motion, digitize and store the resulting signals in a local data acquisition unit, and optionally transmit these digital data. These guidelines are derived from specifications and requirements for data needed to address the nation's emergency response, engineering, and scientific needs as identified in U.S. Geological Survey Circular 1188 (1999). Data needs are discussed in terms of national, regional, and urban scales of monitoring in section 3. Functional performance specifications for instrumentation are introduced in section 4.3 and discussed in detail in section 6 in terms of instrument classes and definitions described in section 5. System aspects and testing recommendations are discussed in sections 7 and 8, respectively. Although U.S. Geological Survey Circular 1188 (1999) recommends that the Advanced National Seismic System (ANSS) include portable instrumentation, performance specifications for this element are not specifically addressed in this document. Nevertheless, these guidelines are largely applicable to portable instrumentation. Volcano monitoring instrumentation is also beyond the scope of this document. Guidance for ANSS structural-response monitoring is discussed briefly herein but details are deferred to the ANSS document by the ANSS Structural Response Monitoring Committee (U.S. Geological Survey, 2005). Aspects of station planning, siting, and installation other than instrumentation are beyond the scope of this document.

Location Performance and Detection Threshold of the Spanish National Seismic Network

NASA Astrophysics Data System (ADS)

D'Alessandro, Antonino; Badal, José; D'Anna, Giuseppe; Papanastassiou, Dimitris; Baskoutas, Ioannis; Özel, Nurcan M.

2013-11-01

Spain is a low-to-moderate seismicity area with relatively low seismic hazard. However, several strong shallow earthquakes have shaken the country causing casualties and extensive damage. Regional seismicity is monitored and surveyed by means of the Spanish National Seismic Network, maintenance and control of which are entrusted to the Instituto Geográfico Nacional. This array currently comprises 120 seismic stations distributed throughout Spanish territory (mainland and islands). Basically, we are interested in checking the noise conditions, reliability, and seismic detection capability of the Spanish network by analyzing the background noise level affecting the array stations, errors in hypocentral location, and detection threshold, which provides knowledge about network performance. It also enables testing of the suitability of the velocity model used in the routine process of earthquake location. To perform this study we use a method that relies on P and S wave travel times, which are computed by simulation of seismic rays from virtual seismic sources placed at the nodes of a regular grid covering the study area. Given the characteristics of the seismicity of Spain, we drew maps for M L magnitudes 2.0, 2.5, and 3.0, at a focal depth of 10 km and a confidence level 95 %. The results relate to the number of stations involved in the hypocentral location process, how these stations are distributed spatially, and the uncertainties of focal data (errors in origin time, longitude, latitude, and depth). To assess the extent to which principal seismogenic areas are well monitored by the network, we estimated the average error in the location of a seismic source from the semiaxes of the ellipsoid of confidence by calculating the radius of the equivalent sphere. Finally, the detection threshold was determined as the magnitude of the smallest seismic event detected at least by four stations. The northwest of the peninsula, the Pyrenees, especially the westernmost segment

Single-station monitoring of volcanoes using seismic ambient noise

NASA Astrophysics Data System (ADS)

De Plaen, Raphael S. M.; Lecocq, Thomas; Caudron, Corentin; Ferrazzini, Valérie; Francis, Olivier

2016-08-01

Seismic ambient noise cross correlation is increasingly used to monitor volcanic activity. However, this method is usually limited to volcanoes equipped with large and dense networks of broadband stations. The single-station approach may provide a powerful and reliable alternative to the classical "cross-station" approach when measuring variation of seismic velocities. We implemented it on the Piton de la Fournaise in Reunion Island, a very active volcano with a remarkable multidisciplinary continuous monitoring. Over the past decade, this volcano has been increasingly studied using the traditional cross-correlation technique and therefore represents a unique laboratory to validate our approach. Our results, tested on stations located up to 3.5 km from the eruptive site, performed as well as the classical approach to detect the volcanic eruption in the 1-2 Hz frequency band. This opens new perspectives to successfully forecast volcanic activity at volcanoes equipped with a single three-component seismometer.

How wind turbines affect the performance of seismic monitoring stations and networks

NASA Astrophysics Data System (ADS)

Neuffer, Tobias; Kremers, Simon

2017-12-01

In recent years, several minor seismic events were observed in the apparently aseismic region of the natural gas fields in Northern Germany. A seismic network was installed in the region consisting of borehole stations with sensor depths up to 200 m and surface stations to monitor induced seismicity. After installation of the network in 2012, an increasing number of wind turbines was established in proximity (<5 km) to several stations, thereby influencing the local noise conditions. This study demonstrates the impact of wind turbines on seismic noise level in a frequency range of 1-10 Hz at the monitoring sites with correlation to wind speed, based on the calculation of power spectral density functions and I95 values of waveforms over a time period of 4 yr. It could be shown that higher wind speeds increase the power spectral density amplitudes at distinct frequencies in the considered frequency band, depending on height as well as number and type of influencing wind turbines. The azimuthal direction of incoming Rayleigh waves at a surface station was determined to identify the noise sources. The analysis of the perturbed wave field showed that Rayleigh waves with backazimuths pointing to wind turbines in operation are dominating the wave field in a frequency band of 3-4 Hz. Additional peaks in a frequency range of 1-4 Hz could be attributed to turbine tower eigenfrequencies of various turbine manufactures with the hub height as defining parameter. Moreover, the influence of varying noise levels at a station on the ability to automatically detect seismic events was investigated. The increased noise level in correlation to higher wind speeds at the monitoring sites deteriorates the station's recording quality inhibiting the automatic detection of small seismic events. As a result, functionality and task fulfilment of the seismic monitoring network is more and more limited by the increasing number of nearby wind turbines.

Identifying and Correcting Timing Errors at Seismic Stations in and around Iran

DOE PAGES

Syracuse, Ellen Marie; Phillips, William Scott; Maceira, Monica; ...

2017-09-06

A fundamental component of seismic research is the use of phase arrival times, which are central to event location, Earth model development, and phase identification, as well as derived products. Hence, the accuracy of arrival times is crucial. However, errors in the timing of seismic waveforms and the arrival times based on them may go unidentified by the end user, particularly when seismic data are shared between different organizations. Here, we present a method used to analyze travel-time residuals for stations in and around Iran to identify time periods that are likely to contain station timing problems. For the 14more » stations with the strongest evidence of timing errors lasting one month or longer, timing corrections are proposed to address the problematic time periods. Finally, two additional stations are identified with incorrect locations in the International Registry of Seismograph Stations, and one is found to have erroneously reported arrival times in 2011.« less

GEODIS: A Portable Ocean Bottom Very Broadband Seismic Station

NASA Astrophysics Data System (ADS)

KARCZEWSKI, J.; MONTAGNER, J.; BEGUERY, L.; STUTZMANN, E.; ROULT, G.; LOGNONNE, P.; CACHO, S.; KOENIG, J.; SAVARY, J.

2001-12-01

The last ten years have seen the simultaneous development of a global seismic network coordinated through the FDSN (Federation of Digital Seismograph Networks) and of portable broadband seismic arrays. The same approach can be followed for improving our scientific understanding of the Earth processes below oceanic areas. Both components of ocean bottom geophysical networks, will be coordinated by ION (international Ocean Network). They are complementary since they enable to investigate the Earth structure and processes at different spatial and temporal scales. Geophysical Ocean bottom observatories (hereafter referred as GOBO) and portable seismic stations are sharing common technological problems. However, the issues of power supply and real-time data transmission are more crucial for a GOBO than for a portable temporary station. Since 1999, our group is developing a new "portable" geophysical ocean bottom autonomous station, named GEODIS. This station might be a basic element for a GOBO. It relies on the use of adapted VBB sensors issued from space experiments and technology and on improved electronics compared with previous ocean bottom experiments (SISMOBS/OFM 1992; MOISE 1997). The main characteristics of GEODIS are the following: - 3 axes VBB seismic sensors with a classical flat velocity response 360-0.2s. at 2500V/m/s (intrinsic noise level smaller than LNM). - Automatic (under software control) installation, levelling, centring of the 3 component seismic sensors. - 24 bit digitiser recording at 20sps, 3 seismic component and 1 infrasonic sensor. - Recording by a 16 bit converter at 1sps of the sea temperature in the vicinity of the instrument and housekeeping parameters (temperature, inclinations, power,...). - 1 year autonomy by using Lithium batteries. - Storage of data on Flash card and recording on hard disk every day. - Weight of GEODIS: 186kg in air and 110kg in water. - Overall dimensions: 930 x 930 x 440 mm. GEODIS can be easily installed by a

Engineering for Autonomous Seismic Stations at the IRIS PASSCAL Instrument Center

NASA Astrophysics Data System (ADS)

Anderson, K. R.; Carpenter, P.; Beaudoin, B. C.; Parker, T.; Hebert, J.; Childs, D.; Chung, P.; Reusch, A. M.

2015-12-01

The NSF funded Incorporated Research Institutions for Seismology (IRIS) through New Mexico Tech operates the PASSCAL Instrument Center (PIC) in Socorro New Mexico. The engineering effort at the PIC seeks to optimize seismic station operations for all portable experiments, include those in extremely remote and harsh polar environments. Recent advances have resulted in improved station design, allowing improved operational efficiencies, data quality return and reduction in station logistics associated with installation, maintenance and decommissioning of stations. These include: Battery and power system designs. Incorporating primary Lithium Thionyl Chloride (LTC) technology with rechargeable Lithium Iron Phosphate (LiFePO4) batteries allows systems to operate in areas with long-term solar autonomy (high latitudes). Development includes charge controller systems to switch between primary and secondary technologies efficiently. Enclosures: Engineered solutions to efficiently manage waste heat, maintain operational environment and provide light-weight and durable housing for seismic instrumentation. Communications: In collaboration with Xeos Technologies Inc., we deliver Iridium-based SOH/Command and Control telemetry as well as full bandwidth seismic data communications in high latitude environments at low power requirements. Smaller-lighter-instrumentation: Through the GEOICE MRI, we are working with Nanometrics on next generation "all-in-one" seismic systems that can be deployed in polar environments - easing logistics, minimizing installation time and improving data quality return for these expensive deployments. All autonomous station designs are openly and freely available at the IRIS PASSCAL webpage (www.passcal.nmt.edu/polar/design-drawings). More information on GEOICE and data quality from various seismometer emplacements will be presented in other posters at this AGU meeting.

Seismic Catalogue and Seismic Network in Haiti

NASA Astrophysics Data System (ADS)

Belizaire, D.; Benito, B.; Carreño, E.; Meneses, C.; Huerfano, V.; Polanco, E.; McCormack, D.

2013-05-01

The destructive earthquake occurred on January 10, 2010 in Haiti, highlighted the lack of preparedness of the country to address seismic phenomena. At the moment of the earthquake, there was no seismic network operating in the country, and only a partial control of the past seismicity was possible, due to the absence of a national catalogue. After the 2010 earthquake, some advances began towards the installation of a national network and the elaboration of a seismic catalogue providing the necessary input for seismic Hazard Studies. This paper presents the state of the works carried out covering both aspects. First, a seismic catalogue has been built, compiling data of historical and instrumental events occurred in the Hispaniola Island and surroundings, in the frame of the SISMO-HAITI project, supported by the Technical University of Madrid (UPM) and Developed in cooperation with the Observatoire National de l'Environnement et de la Vulnérabilité of Haiti (ONEV). Data from different agencies all over the world were gathered, being relevant the role of the Dominican Republic and Puerto Rico seismological services which provides local data of their national networks. Almost 30000 events recorded in the area from 1551 till 2011 were compiled in a first catalogue, among them 7700 events with Mw ranges between 4.0 and 8.3. Since different magnitude scale were given by the different agencies (Ms, mb, MD, ML), this first catalogue was affected by important heterogeneity in the size parameter. Then it was homogenized to moment magnitude Mw using the empirical equations developed by Bonzoni et al (2011) for the eastern Caribbean. At present, this is the most exhaustive catalogue of the country, although it is difficult to assess its degree of completeness. Regarding the seismic network, 3 stations were installed just after the 2010 earthquake by the Canadian Government. The data were sent by telemetry thought the Canadian System CARINA. In 2012, the Spanish IGN together

Improved Seismic Acquisition System and Data Processing for the Italian National Seismic Network

NASA Astrophysics Data System (ADS)

Badiali, L.; Marcocci, C.; Mele, F.; Piscini, A.

2001-12-01

A new system for acquiring and processing digital signals has been developed in the last few years at the Istituto Nazionale di Geofisica e Vulcanologia (INGV). The system makes extensive use of the internet communication protocol standards such as TCP and UDP which are used as the transport highway inside the Italian network, and possibly in a near future outside, to share or redirect data among processes. The Italian National Seismic Network has been working for about 18 years equipped with vertical short period seismometers and transmitting through analog lines, to the computer center in Rome. We are now concentrating our efforts on speeding the migration towards a fully digital network based on about 150 stations equipped with either broad band or 5 seconds sensors connected to the data center partly through wired digital communication and partly through satellite digital communication. The overall process is layered through intranet and/or internet. Every layer gathers data in a simple format and provides data in a processed format, ready to be distributed towards the next layer. The lowest level acquires seismic data (raw waveforms) coming from the remote stations. It handshakes, checks and sends data in LAN or WAN according to a distribution list where other machines with their programs are waiting for. At the next level there are the picking procedures, or "pickers", on a per instrument basis, looking for phases. A picker spreads phases, again through the LAN or WAN and according to a distribution list, to one or more waiting locating machines tuned to generate a seismic event. The event locating procedure itself, the higher level in this stack, can exchange information with other similar procedures. Such a layered and distributed structure with nearby targets allows other seismic networks to join the processing and data collection of the same ongoing event, creating a virtual network larger than the original one. At present we plan to cooperate with other

Data from deployment of temporary seismic stations in northern Norway and Finland

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maercklin, N; Mykkeltveit, S; Schweitzer, J

2005-02-11

This short contribution is a description of data now available in NORSAR's data archives from a temporary deployment during 2002-2004 of six seismic stations in northern Norway and Finland. Explosions in underground as well as open-pit mines in the Khibiny massif of the Kola Peninsula of northwestern Russia are conducted on a frequent and relatively regular basis. It was decided to supplement the network of permanent stations in northern Fennoscandia and northwest Russia with temporarily deployed stations, in order to record these explosions, as well as other mining explosions and natural events occurring in this general area. As shown inmore » Fig. 6.4.1, the six temporary stations were deployed along two profile lines, extending westwards from the Khibini massif. The rationale for this deployment was to collect data to examine distance as well as azimuthal dependence of seismic discriminants. As can be seen from Fig. 6.4.1 the southernmost of the two profile lines runs through the permanent seismic array ARCES in northern Norway.« less

Design and Implementation of the National Seismic Monitoring Network in the Kingdom of Bhutan

NASA Astrophysics Data System (ADS)

Ohmi, S.; Inoue, H.; Chophel, J.; Pelgay, P.; Drukpa, D.

2017-12-01

Bhutan-Himalayan district is located along the plate collision zone between Indian and Eurasian plates, which is one of the most seismically active region in the world. Recent earthquakes such as M7.8 Gorkha Nepal earthquake in April 25, 2015 and M6.7 Imphal, India earthquake in January 3, 2016 are examples of felt earthquakes in Bhutan. However, there is no permanent seismic monitoring system ever established in Bhutan, whose territory is in the center of the Bhutan-Himalayan region. We started establishing permanent seismic monitoring network of minimum requirements and intensity meter network over the nation. The former is composed of six (6) observation stations in Bhutan with short period weak motion and strong motion seismometers as well as three (3) broad-band seismometers, and the latter is composed of twenty intensity meters located in every provincial government office. Obtained data are transmitted to the central processing system in the DGM office in Thimphu in real time. In this project, DGM will construct seismic vault with their own budget which is approved as the World Bank project, and Japan team assists the DGM for site survey of observation site, designing the observation vault, and designing the data telemetry system as well as providing instruments for the observation such as seismometers and digitizers. We already started the operation of the six (6) weak motion stations as well as twenty (20) intensity meter stations. Additionally, the RIMES (Regional Integrated Multi-hazard Early Warning System for Africa and Asia) is also providing eight (8) weak motion stations and we are keeping close communication to operate them as one single seismic monitoring network composed of fourteen (14) stations. This network will be definitely utilized for not only for seismic disaster mitigation of the country but also for studying the seismotectonics in the Bhutan-Himalayan region which is not yet precisely revealed due to the lack of observation data in the

Pattern recognition applied to seismic signals of Llaima volcano (Chile): An evaluation of station-dependent classifiers

NASA Astrophysics Data System (ADS)

Curilem, Millaray; Huenupan, Fernando; Beltrán, Daniel; San Martin, Cesar; Fuentealba, Gustavo; Franco, Luis; Cardona, Carlos; Acuña, Gonzalo; Chacón, Max; Khan, M. Salman; Becerra Yoma, Nestor

2016-04-01

Automatic pattern recognition applied to seismic signals from volcanoes may assist seismic monitoring by reducing the workload of analysts, allowing them to focus on more challenging activities, such as producing reports, implementing models, and understanding volcanic behaviour. In a previous work, we proposed a structure for automatic classification of seismic events in Llaima volcano, one of the most active volcanoes in the Southern Andes, located in the Araucanía Region of Chile. A database of events taken from three monitoring stations on the volcano was used to create a classification structure, independent of which station provided the signal. The database included three types of volcanic events: tremor, long period, and volcano-tectonic and a contrast group which contains other types of seismic signals. In the present work, we maintain the same classification scheme, but we consider separately the stations information in order to assess whether the complementary information provided by different stations improves the performance of the classifier in recognising seismic patterns. This paper proposes two strategies for combining the information from the stations: i) combining the features extracted from the signals from each station and ii) combining the classifiers of each station. In the first case, the features extracted from the signals from each station are combined forming the input for a single classification structure. In the second, a decision stage combines the results of the classifiers for each station to give a unique output. The results confirm that the station-dependent strategies that combine the features and the classifiers from several stations improves the classification performance, and that the combination of the features provides the best performance. The results show an average improvement of 9% in the classification accuracy when compared with the station-independent method.

The Caucasus Seismic Network (CNET): Seismic Structure of the Greater and Lesser Caucasus

NASA Astrophysics Data System (ADS)

Sandvol, E. A.; Mackey, K. G.; Nabelek, J.; Yetermishli, G.; Godoladze, T.; Babayan, H.; Malovichko, A.

2017-12-01

The Greater Caucasus are a portion of the Alpine-Himalayan mountain belt that has undergone rapid uplift in the past 5 million years, thus serving as a unique natural laboratory to study the early stages of orogenesis. Relatively lower resolution seismic velocity models of this region show contradictory lateral variability. Furthermore, recent waveform modeling of seismograms has clearly demonstrated the presence of deep earthquakes (with a maximum hypocentral depth of 175 km) below the Greater Caucasus. The region has been largely unexplored in terms of the detailed uppermost mantle and crustal seismic structure due in part to the disparate data sets that have not yet been merged as well as key portions being sparsely instrumented. We have established collaborative agreements across the region. Building on these agreements we recently deployed a major multi-national seismic array across the Greater Caucasus to address fundamental questions about the nature of continental deformation in this poorly understood region. Our seismic array has two components: (1) a grid of stations spanning the entire Caucasus and (2) two seismic transects consisting of stations spaced at distances of less than 10 km that cross the Greater Caucasus. In addition to the temporary stations, we are working to integrate data from the national networks to produce high resolution images of the seismic structure. Using data from over 106 new seismic stations in Azerbaijan, Armenia, Russia, and Georgia, we hope to gain a better understanding of the recent uplift ( 5 Ma) of the Greater Caucasus and the nature of seismogenic deformation in the region.

Detecting Noisy Events Using Waveform Cross-Correlation at Superarrays of Seismic Stations

NASA Astrophysics Data System (ADS)

von Seggern, D. H.; Tibuleac, I. M.

2007-12-01

Cross-correlation using master events, followed by stacking of the correlation series, has been shown to dramatically improve detection thresholds of small-to-medium seismic arrays. With the goal of lowering the detection threshold, determining relative magnitudes or moments, and characterizing sources by empirical Green's functions, we extend the cross-correlation methodology to include "superarrays" of seismic stations. The superarray concept naturally brings further benefits over conventional arrays and single-stations due to the fact that many distances and azimuths can be sampled. This extension is straightforward given the ease with which regional or global data from various stations or arrays can be currently accessed and combined into a single database. We demonstrate the capability of superarrays to detect and analyze events which lie below the detection threshold. This is aided by applying an F-statistic detector to the superarray cross-correlation stack and its components. Our first example illustrates the use of a superarray consisting of the Southern Great Basin Digital Seismic Network, a small-aperture array (NVAR) in Mina, Nevada and the Earthscope Transportable Array to detect events in California-Nevada areas. In our second example, we use a combination of small-to-medium arrays and single stations to study the rupture of the great Sumatra earthquake of 26 December 2004 and to detect its early aftershocks. The location and times of "detected" events are confirmed using a frequency- wavenumber method at the small-to-medium arrays. We propose that ad hoc superarrays can be used in many studies where conventional approaches previously used only single arrays or groups of single stations. The availability of near-real-time data from many networks and of archived data from, for instance, IRIS makes possible the easy assembly of superarrays. Furthermore, the continued improvement of seismic data availability and the continued growth in the number of

Detecting earthquakes over a seismic network using single-station similarity measures

NASA Astrophysics Data System (ADS)

Bergen, Karianne J.; Beroza, Gregory C.

2018-06-01

New blind waveform-similarity-based detection methods, such as Fingerprint and Similarity Thresholding (FAST), have shown promise for detecting weak signals in long-duration, continuous waveform data. While blind detectors are capable of identifying similar or repeating waveforms without templates, they can also be susceptible to false detections due to local correlated noise. In this work, we present a set of three new methods that allow us to extend single-station similarity-based detection over a seismic network; event-pair extraction, pairwise pseudo-association, and event resolution complete a post-processing pipeline that combines single-station similarity measures (e.g. FAST sparse similarity matrix) from each station in a network into a list of candidate events. The core technique, pairwise pseudo-association, leverages the pairwise structure of event detections in its network detection model, which allows it to identify events observed at multiple stations in the network without modeling the expected moveout. Though our approach is general, we apply it to extend FAST over a sparse seismic network. We demonstrate that our network-based extension of FAST is both sensitive and maintains a low false detection rate. As a test case, we apply our approach to 2 weeks of continuous waveform data from five stations during the foreshock sequence prior to the 2014 Mw 8.2 Iquique earthquake. Our method identifies nearly five times as many events as the local seismicity catalogue (including 95 per cent of the catalogue events), and less than 1 per cent of these candidate events are false detections.

Detecting Earthquakes over a Seismic Network using Single-Station Similarity Measures

NASA Astrophysics Data System (ADS)

Bergen, Karianne J.; Beroza, Gregory C.

2018-03-01

New blind waveform-similarity-based detection methods, such as Fingerprint and Similarity Thresholding (FAST), have shown promise for detecting weak signals in long-duration, continuous waveform data. While blind detectors are capable of identifying similar or repeating waveforms without templates, they can also be susceptible to false detections due to local correlated noise. In this work, we present a set of three new methods that allow us to extend single-station similarity-based detection over a seismic network; event-pair extraction, pairwise pseudo-association, and event resolution complete a post-processing pipeline that combines single-station similarity measures (e.g. FAST sparse similarity matrix) from each station in a network into a list of candidate events. The core technique, pairwise pseudo-association, leverages the pairwise structure of event detections in its network detection model, which allows it to identify events observed at multiple stations in the network without modeling the expected move-out. Though our approach is general, we apply it to extend FAST over a sparse seismic network. We demonstrate that our network-based extension of FAST is both sensitive and maintains a low false detection rate. As a test case, we apply our approach to two weeks of continuous waveform data from five stations during the foreshock sequence prior to the 2014 Mw 8.2 Iquique earthquake. Our method identifies nearly five times as many events as the local seismicity catalog (including 95% of the catalog events), and less than 1% of these candidate events are false detections.

Influence of wind turbines on seismic stations in the upper rhine graben, SW Germany

NASA Astrophysics Data System (ADS)

Zieger, Toni; Ritter, Joachim R. R.

2018-01-01

By analysing long- and short-term seismological measurements at wind farms close to the town of Landau, SW Germany, we present new insights into ground motion signals from wind turbines (WTs) at local seismic stations. Because of their need to be located in similar regions with sparsely anthropogenic activities, wind turbines impact seismic stations and their recordings in a way that is not yet fully understood by researchers. To ensure the undisturbed recording tasks of a regional seismic array or a single station by a protected area around those endangered stations, it is very important to investigate the behavior of WTs as a seismic source. For that reason, we calculate averaged one-hour long spectra of the power spectral density (PSD) before and after the installation of a new wind farm within the investigated area. These PSD are ordered according to the rotation speed. We observe a clear increase of the PSD level after the WT installation in a frequency range of 0.5 to 10 Hz up to a distance of 5.5 km away from the WT. By analysing seismic borehole data, we also observe a decrease of the PSD of wind dependent signals with depth. The impact of wind-dependent signals is found to be much more pronounced for the shallower station (150 m depth) than for the deeper one (305 m depth). Using short-term profile measurements, we fit a power-law decay proportional to 1/ r b to the main WT-induced PSD peaks and differentiate between near-field and far-field effects of ground motions. For low frequencies in the range from 1 to 4 Hz, we determine a b value of 0.78 to 0.85 for the far field, which is consistent with surface waves. The b value increases (up to 1.59) with increasing frequencies (up to 5.5 Hz), which is obviously due to attenuating effects like scattering or anelasticity. These results give a better understanding of the seismic wavefield interactions between wind turbines (or wind farms) with nearby seismic stations, including borehole installations, in a

Investigating the Effects Fracture Systems Have on Seismic Wave Velocities at the Lajitas, Texas Seismic Station

DTIC Science & Technology

1989-05-01

Victoria L. Sandidge-Bodoh % S Southern Methodist University Department of Geological Sciences Dallas, TX 75275 1 May 1989 Final Report 3 March 1987 - 2...Projects Agency or the U.S. Government. This technical report has been reviewed and is approved for publicj ion. JAME F. LEWKOW(CZ J/ S F. LEWKOWiC...Effects Fracture Systems Have on Seismic Wave Velocities at the Lajitas, Texas Seismic Station 12. PERSONAL AUTHOR( S ) Victoria L. Sandidge-Bodoh 13a. TYPE

A method to establish seismic noise baselines for automated station assessment

USGS Publications Warehouse

McNamara, D.E.; Hutt, C.R.; Gee, L.S.; Benz, H.M.; Buland, R.P.

2009-01-01

We present a method for quantifying station noise baselines and characterizing the spectral shape of out-of-nominal noise sources. Our intent is to automate this method in order to ensure that only the highest-quality data are used in rapid earthquake products at NEIC. In addition, the station noise baselines provide a valuable tool to support the quality control of GSN and ANSS backbone data and metadata. The procedures addressed here are currently in development at the NEIC, and work is underway to understand how quickly changes from nominal can be observed and used within the NEIC processing framework. The spectral methods and software used to compute station baselines and described herein (PQLX) can be useful to both permanent and portable seismic stations operators. Applications include: general seismic station and data quality control (QC), evaluation of instrument responses, assessment of near real-time communication system performance, characterization of site cultural noise conditions, and evaluation of sensor vault design, as well as assessment of gross network capabilities (McNamara et al. 2005). Future PQLX development plans include incorporating station baselines for automated QC methods and automating station status report generation and notification based on user-defined QC parameters. The PQLX software is available through the USGS (http://earthquake. usgs.gov/research/software/pqlx.php) and IRIS (http://www.iris.edu/software/ pqlx/).

Seismic Station Installation Orientation Errors at ANSS and IRIS/USGS Stations

USGS Publications Warehouse

Ringler, Adam T.; Hutt, Charles R.; Persfield, K.; Gee, Lind S.

2013-01-01

Many seismological studies depend on the published orientations of sensitive axes of seismic instruments relative to north (e.g., Li et al., 2011). For example, studies of the anisotropic structure of the Earth’s mantle through SKS‐splitting measurements (Long et al., 2009), constraints on core–mantle electromagnetic coupling from torsional normal‐mode measurements (Dumberry and Mound, 2008), and models of three‐dimensional (3D) velocity variations from surface waves (Ekström et al., 1997) rely on accurate sensor orientation. Unfortunately, numerous results indicate that this critical parameter is often subject to significant error (Laske, 1995; Laske and Masters, 1996; Yoshizawa et al., 1999; Schulte‐Pelkum et al., 2001; Larson and Ekström, 2002). For the Advanced National Seismic System (ANSS; ANSS Technical Integration Committee, 2002), the Global Seismographic Network (GSN; Butler et al., 2004), and many other networks, sensor orientation is typically determined by a field engineer during installation. Successful emplacement of a seismic instrument requires identifying true north, transferring a reference line, and measuring the orientation of the instrument relative to the reference line. Such an exercise is simple in theory, but there are many complications in practice. There are four commonly used methods for determining true north at the ANSS and GSN stations operated by the USGS Albuquerque Seismological Laboratory (ASL), including gyroscopic, astronomical, Global Positioning System (GPS), and magnetic field techniques. A particular method is selected based on site conditions (above ground, below ground, availability of astronomical observations, and so on) and in the case of gyroscopic methods, export restrictions. Once a north line has been determined, it must be translated to the sensor location. For installations in mines or deep vaults, this step can include tracking angles through the one or more turns in the access tunnel leading to

Seismic Tomography of Siyazan - Shabran Oil and Gas Region Of Azerbaijan by Data of The Seismic Stations

NASA Astrophysics Data System (ADS)

Yetirmishli, Gurban; Guliyev, Ibrahim; Mammadov, Nazim; Kazimova, Sabina; Ismailova, Saida

2016-04-01

The main purpose of the research was to build a reliable 3D model of the structure of seismic velocities in the earth crust on the territory of Siyazan-Shabran region of Azerbaijan, using the data of seismic telemetry stations spanning Siyazan-Shabran region (Siyazan, Altiagaj, Pirgulu, Guba, Khinalig, Gusar), including 7 mobile telemetry seismic stations. Interest to the problem of research seismic tomography caused by applied environmental objectives, such as the assessment of geological risks, engineering evaluation (stability and safety of wells), the task of exploration and mining operations. In the study region are being actively developed oil fields, and therefore, there is a risk of technogenic earthquakes. It was performed the calculation of first arrival travel times of P and S waves and the corresponding ray paths. Calculate 1D velocity model which is the initial model as a set of horizontal layers (velocity may be constant or changed linearly with depth on each layer, gaps are possible only at the boundaries between the layers). Have been constructed and analyzed the horizontal sections of the three-dimensional velocity model at different depths of the investigated region. By the empirical method was proposed density model of the sedimentary rocks at depths of 0-8 km.

A New Design of Seismic Stations Deployed in South Tyrol

NASA Astrophysics Data System (ADS)

Melichar, P.; Horn, N.

2007-05-01

When designing the seismic network in South Tyrol, the seismic service of Austria and the Civil defense in South Tyrol combined more that 10 years experience in running seismic networks and private communication systems. In recent years the high data return rate of > 99% and network uptime of > 99.% is achieved by the combination of high quality station design and equipment, and the use of the Antelope data acquisition and processing software which comes with suite of network monitoring & alerting tools including Nagios, etc. The new Data Center is located in city of Bolzano and is connected to the other Data Centers in Austria, Switzerland, and Italy for data back up purposes. Each Data Center uses also redundant communication system if the primary system fails. When designing the South Tyrol network, new improvements were made in seismometer installations, grounding, lighting protection and data communications in order to improve quality of data recorded as well as network up-time, and data return. The new 12 stations are equipped with 6 Channels Q330+PB14f connected to STS2 + EpiSensor sensor. One of the key achievements was made in the grounding concept for the whole seismic station - and aluminum boxes were introduced which delivered Faraday cage isolation. Lightning protection devices are used for the equipment inside the aluminum housing where seismometer and data logger are housed. For the seismometer cables a special shielding was introduced. The broadband seismometer and strong-motion sensor are placed on a thick glass plate and therefore isolated from the ground. The precise seismometer orientation was done by a special groove on the glass plate and in case of a strong earthquake; the seismometer is tide up to the base plate. Temperature stability was achieved by styrofoam sheets inside the seismometer aluminum protection box.

Seismic noise study for a new seismic station at King Fahd University of Petroleum and Minerals in Saudi Arabia

NASA Astrophysics Data System (ADS)

Kaka, S. I.

2012-04-01

We have carried out a seismic noise study in order to understand the noise level at three selected locations at King Fahd University of Petroleum and Minerals (KFUPM), Dhahran, Saudi Arabia. The main purpose is to select a suitable site with low seismic noise and good signal-to-noise ratio for our new broadband seismic station. There are several factors involved in the selection of a site location for a new station. Most importantly, we need to strike a balance between a logistically convenient site versus a technically suitable site. As a starting point, we selected six potential sites due to accessibility and proximity to the seismic processing center laboratory in the Department of Earth Sciences (ESD) at KFUPM. We then eliminated two sites that are relatively close to possible low-frequency noise sources. We have considered many possible noise sources which include: vehicle traffic / heavy machinery, the direct path of air flowing from air conditioning vent, tall trees / power poles and metal doorways. One more site was eliminated because the site was located in the open where it experiences maximum wind speed which is considered a major source of noise. All three potential sites are situated within the Dammam Dome where both lower middle and upper Rus Formations are exposed. The upper Rus is mainly made up of fine grained chalky limestone and the lower Rus is made up of alternation of marls and thin dolomitic limestone. The area is not known for any major faults and considered very low seismicity and hence the identification of seismoteconic features is not required. Before conducting the noise study, we calibrated and tested the seismic recording system, which was recently acquired by the ESD at KFUPM. The system includes a seismic recorder and a sensor with a GPS device. We deployed the system in order to measure the low-frequency background noise. Knowing the low frequency noise will help in predicting the high-frequency noise. The recording systems were

Optimizing Multi-Station Template Matching to Identify and Characterize Induced Seismicity in Ohio

NASA Astrophysics Data System (ADS)

Brudzinski, M. R.; Skoumal, R.; Currie, B. S.

2014-12-01

As oil and gas well completions utilizing multi-stage hydraulic fracturing have become more commonplace, the potential for seismicity induced by the deep disposal of frac-related flowback waters and the hydraulic fracturing process itself has become increasingly important. While it is rare for these processes to induce felt seismicity, the recent increase in the number of deep injection wells and volumes injected have been suspected to have contributed to a substantial increase of events = M 3 in the continental U.S. over the past decade. Earthquake template matching using multi-station waveform cross-correlation is an adept tool for investigating potentially induced sequences due to its proficiency at identifying similar/repeating seismic events. We have sought to refine this approach by investigating a variety of seismic sequences and determining the optimal parameters (station combinations, template lengths and offsets, filter frequencies, data access method, etc.) for identifying induced seismicity. When applied to a sequence near a wastewater injection well in Youngstown, Ohio, our optimized template matching routine yielded 566 events while other template matching studies found ~100-200 events. We also identified 77 events on 4-12 March 2014 that are temporally and spatially correlated with active hydraulic fracturing in Poland Township, Ohio. We find similar improvement in characterizing sequences in Washington and Harrison Counties, which appear to be related to wastewater injection and hydraulic fracturing, respectively. In the Youngstown and Poland Township cases, focal mechanisms and double difference relocation using the cross-correlation matrix finds left-lateral faults striking roughly east-west near the top of the basement. We have also used template matching to determine isolated earthquakes near several other wastewater injection wells are unlikely to be induced based on a lack of similar/repeating sequences. Optimized template matching utilizes

Korea Integrated Seismic System tool(KISStool) for seismic monitoring and data sharing at the local data center

NASA Astrophysics Data System (ADS)

Park, J.; Chi, H. C.; Lim, I.; Jeong, B.

2011-12-01

The Korea Integrated Seismic System(KISS) is a back-bone seismic network which distributes seismic data to different organizations in near-real time at Korea. The association of earthquake monitoring institutes has shared their seismic data through the KISS from 2003. Local data centers operating remote several stations need to send their free field seismic data to NEMA(National Emergency Management Agency) by the law of countermeasure against earthquake hazard in Korea. It is very important the efficient tool for local data centers which want to rapidly detect local seismic intensity and to transfer seismic event information toward national wide data center including PGA, PGV, dominant frequency of P-wave, raw data, and etc. We developed the KISStool(Korea Integrated Seismic System tool) for easy and convenient operation seismic network in local data center. The KISStool has the function of monitoring real time waveforms by clicking station icon on the Google map and real time variation of PGA, PGV, and other data by opening the bar type monitoring section. If they use the KISStool, any local data center can transfer event information to NEMA(National Emergency Management Agency), KMA(Korea Meteorological Agency) or other institutes through the KISS using UDP or TCP/IP protocols. The KISStool is one of the most efficient methods to monitor and transfer earthquake event at local data center in Korea. KIGAM will support this KISStool not only to the member of the monitoring association but also local governments.

A probabilistic framework for single-station location of seismicity on Earth and Mars

NASA Astrophysics Data System (ADS)

Böse, M.; Clinton, J. F.; Ceylan, S.; Euchner, F.; van Driel, M.; Khan, A.; Giardini, D.; Lognonné, P.; Banerdt, W. B.

2017-01-01

Locating the source of seismic energy from a single three-component seismic station is associated with large uncertainties, originating from challenges in identifying seismic phases, as well as inevitable pick and model uncertainties. The challenge is even higher for planets such as Mars, where interior structure is a priori largely unknown. In this study, we address the single-station location problem by developing a probabilistic framework that combines location estimates from multiple algorithms to estimate the probability density function (PDF) for epicentral distance, back azimuth, and origin time. Each algorithm uses independent and complementary information in the seismic signals. Together, the algorithms allow locating seismicity ranging from local to teleseismic quakes. Distances and origin times of large regional and teleseismic events (M > 5.5) are estimated from observed and theoretical body- and multi-orbit surface-wave travel times. The latter are picked from the maxima in the waveform envelopes in various frequency bands. For smaller events at local and regional distances, only first arrival picks of body waves are used, possibly in combination with fundamental Rayleigh R1 waveform maxima where detectable; depth phases, such as pP or PmP, help constrain source depth and improve distance estimates. Back azimuth is determined from the polarization of the Rayleigh- and/or P-wave phases. When seismic signals are good enough for multiple approaches to be used, estimates from the various methods are combined through the product of their PDFs, resulting in an improved event location and reduced uncertainty range estimate compared to the results obtained from each algorithm independently. To verify our approach, we use both earthquake recordings from existing Earth stations and synthetic Martian seismograms. The Mars synthetics are generated with a full-waveform scheme (AxiSEM) using spherically-symmetric seismic velocity, density and attenuation models of

Surface Wave Tomography of South China Sea from Ambient Seismic Noise and Two-station Measurements

NASA Astrophysics Data System (ADS)

Liang, W.-T.; Gung, Y.-C.

2012-04-01

We have taken the cross-correlation of seismic ambient noise technique as well as the two-station method to analyze the velocity structure in the South China Sea region. The dataset used in this study includes broadband waveforms recorded at the Taiwan BATS (Broadband Array in Taiwan for Seismology), Japan OHP (Ocean Hemisphere Project), Malaysia and Vietnam seismic networks. We remove the instrument response from daily data and filter the waveform with various frequency bands according to the length of each station-pair. Then we apply the commonly used 1-bit normalization to minimize the effect of earthquakes, instrumental irregularities, and non-stationary noise sources near to the stations. With the derived daily cross correlation function (CCF), we are able to examine the timing quality for each station-pair. We then obtain the surface Rayleigh wave dispersion curves from the stacked CCF for each station-pair. To cover the longer period band in the dispersion curves, we adopt the two-station method to compute both the group and phase velocities of surface waves. A new surface wave tomography based on ambient seismic noise study and traditional two-station technique has been achieved in this study. Raypaths that travel through the Central basin present higher velocity, which is in agreement with the idea of thin crust. On the other hand, the slower velocity between Taiwan and Northern Luzon, Philippine is mainly due to a thick accretionary prism above the Manila trench.

Engineering challenges of operating year-round portable seismic stations at high-latitude

NASA Astrophysics Data System (ADS)

Beaudoin, Bruce; Carpenter, Paul; Hebert, Jason; Childs, Dean; Anderson, Kent

2017-04-01

Remote portable seismic stations are, in most cases, constrained by logistics and cost. High latitude operations introduce environmental, technical and logistical challenges that require substantially more engineering work to ensure robust, high quality data return. Since 2006, IRIS PASSCAL has been funded by NSF to develop, deploy, and maintain a pool of polar specific seismic stations. Here, we describe our latest advancements to mitigate the challenges of high-latitude, year-round station operation. The IRIS PASSCAL program has supported high-latitude deployments since the late 1980s. These early deployments were largely controlled source, summer only experiments. In early 2000 PASSCAL users began proposing year-round deployments of broadband stations in some of the harshest environments on the planet. These early year-round deployments were stand-alone (no telemetry) stations largely designed to operate during summer months and then run as long as possible during the winter with hopes the stations would revive come following summer. In 2006 and in collaboration with UNAVCO, we began developing communications, power systems, and enclosures to extend recording to year-round. Since this initial effort, PASSCAL continued refinement to power systems, enclosure design and manufacturability, and real-time data communications. Several sensor and data logger manufacturers have made advances in cold weather performance and delivered newly designed instruments that have furthered our ability to successfully run portable stations at high-latitude with minimal logistics - reducing size and weight of instruments and infrastructure. All PASSCAL polar engineering work is openly shared through our website: www.passcal.nmt.edu/content/polar

National Earthquake Information Center Seismic Event Detections on Multiple Scales

NASA Astrophysics Data System (ADS)

Patton, J.; Yeck, W. L.; Benz, H.; Earle, P. S.; Soto-Cordero, L.; Johnson, C. E.

2017-12-01

The U.S. Geological Survey National Earthquake Information Center (NEIC) monitors seismicity on local, regional, and global scales using automatic picks from more than 2,000 near-real time seismic stations. This presents unique challenges in automated event detection due to the high variability in data quality, network geometries and density, and distance-dependent variability in observed seismic signals. To lower the overall detection threshold while minimizing false detection rates, NEIC has begun to test the incorporation of new detection and picking algorithms, including multiband (Lomax et al., 2012) and kurtosis (Baillard et al., 2014) pickers, and a new bayesian associator (Glass 3.0). The Glass 3.0 associator allows for simultaneous processing of variably scaled detection grids, each with a unique set of nucleation criteria (e.g., nucleation threshold, minimum associated picks, nucleation phases) to meet specific monitoring goals. We test the efficacy of these new tools on event detection in networks of various scales and geometries, compare our results with previous catalogs, and discuss lessons learned. For example, we find that on local and regional scales, rapid nucleation of small events may require event nucleation with both P and higher-amplitude secondary phases (e.g., S or Lg). We provide examples of the implementation of a scale-independent associator for an induced seismicity sequence (local-scale), a large aftershock sequence (regional-scale), and for monitoring global seismicity. Baillard, C., Crawford, W. C., Ballu, V., Hibert, C., & Mangeney, A. (2014). An automatic kurtosis-based P-and S-phase picker designed for local seismic networks. Bulletin of the Seismological Society of America, 104(1), 394-409. Lomax, A., Satriano, C., & Vassallo, M. (2012). Automatic picker developments and optimization: FilterPicker - a robust, broadband picker for real-time seismic monitoring and earthquake early-warning, Seism. Res. Lett. , 83, 531-540, doi: 10

Origins of a national seismic system in the United States

USGS Publications Warehouse

Filson, John R.; Arabasz, Walter J.

2016-01-01

This historical review traces the origins of the current national seismic system in the United States, a cooperative effort that unifies national, regional, and local‐scale seismic monitoring within the structure of the Advanced National Seismic System (ANSS). The review covers (1) the history and technological evolution of U.S. seismic networks leading up to the 1990s, (2) factors that made the 1960s and 1970s a watershed period for national attention to seismology, earthquake hazards, and seismic monitoring, (3) genesis of the vision of a national seismic system during 1980–1983, (4) obstacles and breakthroughs during 1984–1989, (5) consensus building and convergence during 1990–1992, and finally (6) the two‐step realization of a national system during 1993–2000. Particular importance is placed on developments during the period between 1980 and 1993 that culminated in the adoption of a charter for the Council of the National Seismic System (CNSS)—the foundation for the later ANSS. Central to this story is how many individuals worked together toward a common goal of a more rational and sustainable approach to national earthquake monitoring in the United States. The review ends with the emergence of ANSS during 1999 and 2000 and its statutory authorization by Congress in November 2000.

Analysis of the Seismicity Associated to the Subduction of the Rivera Plate using OBS and Onland Stations.

NASA Astrophysics Data System (ADS)

Nuñez-Cornu, F. J.; Barba, D. C., Sr.; Danobeitia, J.; Bandy, W. L.; Zamora-Camacho, A.; Marquez-Ramirez, V. H.; Ambros, M.; Gomez, A.; Sandoval, J. M.; Mortera-Gutierrez, C. A.

2016-12-01

The second stage of TsuJal Project includes the study of passive seismic activity in the region of the plate Rivera and Jalisco block by anchoring OBS and densifying the network of seismic stations on land for at least four months. This stage began in April 2016 with the deployment of 25 Obsidian stations with sensor Le-3D MkIII from the northern part of Nayarit state to the south of Colima state, including the Marias Islands. This temporal seismic network complements the Jalisco Seismic Network (RESAJ) for a total of 50 stations. Offshore, ten OBS type LCHEAPO 2000 with 4 channel (3 seismic short period and 1 pressure) were deployed, in the period from 19 to 30 April 2016 using the BO El Puma from UNAM. The OBS were deployed in an array from the Marias Islands to offcoast of the border of Colima and Michoacan states. On May 4, an earthquake with Ml = 4.2 took place in the contact area of the Rivera Plate, Cocos Plate and the Middle America Trench, subsequently occurred a seismic swarm with over 200 earthquakes until May 16, including an earthquake with Ml = 5.0 on May 7. A second swarm took place between May 28 and Jun 4 including an earthquake with Ml = 4.8 on Jun 1. An analysis of the quality of different location methods is presented: automatic preliminary RESAJ location using Antelope; location with revised RESAJ phases in Antelope; relocation of RESAJ data with hypo and a regional velocity model; relocation of RESAJ data with hypo adding data from the temporal seismic network stations; and finally the relocation adding the data from the OBS network. Moreover, the tectonic implications of these earthquakes are discussed.

Seismicity around the source areas of the 1946 Nankai and the 1944 Tonankai earthquakes detected from data recorded at DONET stations

NASA Astrophysics Data System (ADS)

Suzuki, K.; Kamiya, S.; Takahashi, N.

2016-12-01

The Japan Agency for Marine-Earth Science and Technology (JAMSTEC) installed DONET (Dense Oceanfloor Network System for Earthquakes and Tsunamis) off the Kii Peninsula, southwest of Japan, to monitor earthquakes and tsunamis. Stations of DONET1, which are distributed in Kumano-nada, and DONET2, which are distributed off Muroto, were installed by August 2011 and April 2016, respectively. After the installation of all of the 51 stations, DONET was transferred to National Research Institute for Earth Science and Disaster Resilience (NIED). NIED and JAMSTEC have now corroborated in the operation of DONET since April 2016. To investigate the seismicity around the source areas of the 1946 Nankai and the 1944 Tonankai earthquakes, we detected earthquakes from the records of the broadband seismometers installed to DONET. Because DONET stations are apart from land stations, we can detect smaller earthquakes than by using only land stations. It is important for understanding the stress state and seismogenic mechanism to monitoring the spatial-temporal seismicity change. In this study we purpose to evaluate to the seismicity around the source areas of the Nankai and the Tonankai earthquakes by using our earthquake catalogue. The frequency-magnitude relationships of earthquakes in the areas of DONET1&2 had an almost constant slope of about -1 for earthquakes of ML larger than 1.5 and 2.5, satisfying the Gutenberg-Richter law, and the slope of smaller earthquakes approached 0, reflecting the detection limits. While the most of the earthquakes occurred in the aftershock area of the 2004 off the Kii Peninsula earthquakes, very limited activity was detected in the source region of the Nankai and Tonankai earthquake except for the large earthquake (MJMA = 6.5) on 1st April 2016 and its aftershocks. We will evaluate the detection limit of the earthquake in more detail and investigate the spatial-temporal seismicity change with waiting the data store.

Development and Performance of the Alaska Transportable Array Posthole Broadband Seismic Station

NASA Astrophysics Data System (ADS)

Aderhold, K.; Enders, M.; Miner, J.; Bierma, R. M.; Bloomquist, D.; Theis, J.; Busby, R. W.

2017-12-01

The final stations of the Alaska Transportable Array (ATA) will be constructed in 2017, completing the full footprint of 280 new and existing broadband seismic stations stretching across 19 degrees of latitude from western Alaska to western Canada. Through significant effort in planning, site reconnaissance, permitting and the considerable and concerted effort of field crews, the IRIS Alaska TA team is on schedule to successfully complete the construction of 194 new stations and upgrades at 28 existing stations over four field seasons. The station design and installation method was developed over the course of several years, leveraging the experience of the L48 TA deployments and existing network operators in Alaska as well as incorporating newly engineered components and procedures. A purpose-built lightweight drill was designed and fabricated to facilitate the construction of shallow boreholes to incorporate newly available posthole seismometers. This allowed for the development of a streamlined system of procedures to manufacture uniform seismic stations with minimal crew and minimal time required at each station location. A new station can typically be constructed in a single day with a four-person field crew. The ATA utilizes a hammer-drilled, cased posthole emplacement method adapted to the remote and harsh working environment of Alaska. The same emplacement design is implemented in all ground conditions to preserve uniformity across the array and eliminate the need for specialized mechanical equipment. All components for station construction are ideally suited for transport via helicopter, and can be adapted to utilize more traditional methods of transportation when available. This emplacement design delivers high quality data when embedded in bedrock or permafrost, reaching the low noise levels of benchmark permanent global broadband stations especially at long periods over 70 seconds. The TA will operate the network of real-time stations through at least

The research of a solution on locating optimally a station for seismic disasters rescue in a city

NASA Astrophysics Data System (ADS)

Yao, Qing-Lin

1995-02-01

When the stations for seismic disasters rescue in future or the similars are designed on a network of communication line, the general absolute center of a graph needs to be solved to reduce the requirements in the number of stations and running parameters and to establish an optimal station in a sense distribution of the rescue arrival time by the way of locating optimally the stations. The existing solution on this problem was proposed by Edward (1978) in which, however, there is serious deviation. In this article, the work of Edward (1978) is developed in both formula and figure, more correct solution is proposed and proved. Then the result from the newer solution is contrasted with that from the older one in a instance about locating optimally the station for seismic disasters rescue.

Adding seismic broadband analysis to characterize Andean backarc seismicity in Argentina

NASA Astrophysics Data System (ADS)

Alvarado, P.; Giuliano, A.; Beck, S.; Zandt, G.

2007-05-01

Characterization of the highly seismically active Andean backarc is crucial for assessment of earthquake hazards in western Argentina. Moderate-to-large crustal earthquakes have caused several deaths, damage and drastic economic consequences in Argentinean history. We have studied the Andean backarc crust between 30°S and 36°S using seismic broadband data available from a previous ("the CHARGE") IRIS-PASSCAL experiment. We collected more than 12 terabytes of continuous seismic data from 22 broadband instruments deployed across Chile and Argentina during 1.5 years. Using free software we modeled full regional broadband waveforms and obtained seismic moment tensor inversions of crustal earthquakes testing for the best focal depth for each event. We also mapped differences in the Andean backarc crustal structure and found a clear correlation with different types of crustal seismicity (i.e. focal depths, focal mechanisms, magnitudes and frequencies of occurrence) and previously mapped terrane boundaries. We now plan to use the same methodology to study other regions in Argentina using near-real time broadband data available from the national seismic (INPRES) network and global seismic networks operating in the region. We will re-design the national seismic network to optimize short-period and broadband seismic station coverage for different network purposes. This work is an international effort that involves researchers and students from universities and national government agencies with the goal of providing more information about earthquake hazards in western Argentina.

Estimation of background noise level on seismic station using statistical analysis for improved analysis accuracy

NASA Astrophysics Data System (ADS)

Han, S. M.; Hahm, I.

2015-12-01

We evaluated the background noise level of seismic stations in order to collect the observation data of high quality and produce accurate seismic information. Determining of the background noise level was used PSD (Power Spectral Density) method by McNamara and Buland (2004) in this study. This method that used long-term data is influenced by not only innate electronic noise of sensor and a pulse wave resulting from stabilizing but also missing data and controlled by the specified frequency which is affected by the irregular signals without site characteristics. It is hard and inefficient to implement process that filters out the abnormal signal within the automated system. To solve these problems, we devised a method for extracting the data which normally distributed with 90 to 99% confidence intervals at each period. The availability of the method was verified using 62-seismic stations with broadband and short-period sensors operated by the KMA (Korea Meteorological Administration). Evaluation standards were NHNM (New High Noise Model) and NLNM (New Low Noise Model) published by the USGS (United States Geological Survey). It was designed based on the western United States. However, Korean Peninsula surrounded by the ocean on three sides has a complicated geological structure and a high population density. So, we re-designed an appropriate model in Korean peninsula by statistically combined result. The important feature is that secondary-microseism peak appeared at a higher frequency band. Acknowledgements: This research was carried out as a part of "Research for the Meteorological and Earthquake Observation Technology and Its Application" supported by the 2015 National Institute of Meteorological Research (NIMR) in the Korea Meteorological Administration.

Seismic Monitoring of Rock Falls in Yosemite National Park

NASA Astrophysics Data System (ADS)

Zimmer, V. L.; Stock, G. M.; Sitar, N.

2008-12-01

Between 1857 and 2007, more than 600 landslide events have been documented in Yosemite National Park, with the vast majority of events occurring as rock falls in Yosemite Valley. The conditions leading to and triggering rock fall are understood in approximately 50 percent of cases, but in the other 50 percent, there were no apparent triggers. Occasionally, large rock falls have been preceded by smaller events that, in retrospect, may have been precursors. Close range seismic monitoring presents an opportunity to study the conditions leading up to rock fall, as well as the mechanics of the actual rock fall as recorded seismically. During the winter of 2007-08, we conducted a rock fall seismic monitoring feasibility study in Yosemite Valley. A station consisting of an 8 Hz geophone and an accelerometer was placed on a ledge 1000 feet above the valley floor, in a historically active rock fall area known as the Three Brothers. At least two rock falls in this area were recorded by the instrumentation and witnessed by visitors, representing the first time rock falls have been recorded with seismic instrumentation in Yosemite Valley. Significant energy was recorded in a wide frequency range, from a few Hz to approximately 150 Hz, limited by the geophone response and attenuation of the signal due to distance to the source (400 m). Furthermore, there exists a weak signal approximately 5-10 seconds before the obvious rock fall signature. We hypothesize that the weak signal represents rock fall initiation manifesting as the first blocks sliding down the cliff face, while the stronger impulses represent these blocks impacting ledges and the bottom talus field. This study demonstrated that rock fall monitoring is feasible with seismic instrumentation, and serves as the catalyst for future studies using a network of sensors for more advanced analysis.

Unravelling Responses for the Canadian National Seismic Network

NASA Astrophysics Data System (ADS)

Mulder, T. L.

2009-12-01

There are a number of attendant difficulties any network must deal with that range from defining the transfer function to instrument naming conventions to choices of final local file format representation. These choices ultimately result in the ease of conversion to other data formats and therefore directly impact useability. In particular, the ease of data exhange and use of established software that is dependent on standard data types is impacted. This becomes particularly critical with large (terabyte) dataset processing and when integrating external datasets into analysis procedures. Transfer functions, often referred to as instrument responses, are a key component in describing instrumentation. The transfer function describes the complete response of the seismic system. The seismic system is designed to be a linear system that can be decomposed into discrete components. Analogue or digital convolution can be represented as multiplication in the frequency domain. The two basic elements of a seismic system are the sensor and datalogger. The analogue sensor can be represented mathmatically as poles and zeroes. The datalogger can be further broken down into its discrete analogue and digital components: the preamp, A/D converter, and fir filters. The Canadian seismic network (CNSN) digitizers have an additional complication. To save telemetry band-width, the 32 bit signal from the digitizer has a transmission gain removed. The transmission gain (txgain) represents the number of the least significant bits truncated from the sample (2^txgain) after which the data is compressed and transmitted. While telemetry band-width is not the issue it was, now that many sites have ip connectivity, this user programmable transmission gain is still in use and can vary from station to station. The processes receiving the transmitted data do not restore the pre-transmission scaling, consequently the archived waveform files can vary in bit weight over time from station to station

Ghana's experience in the establishment of a national digital seismic network observatory

NASA Astrophysics Data System (ADS)

Ahulu, Sylvanus; Danuor, Sylvester Kojo

2015-07-01

The Government of Ghana has established a National Digital Seismic Network Observatory in Ghana with the aim of monitoring events such as earthquakes, blasts from mining and quarrying, nuclear tests, etc. The Digital Observatory was commissioned on 19 December 2012, and was dedicated to Geosciences in Ghana. Previously Ghana did not have any operational, digital seismic network acquisition system with the capability of monitoring and analysing data for planning and research purposes. The Ghana Geological Survey has been monitoring seismic events with an analogue system which was not efficient and does not deliver real-time data. Hence, the importance of setting up the National Digital Seismic Network System which would enable the Geological Survey to constantly monitor, manage and coordinate both natural and man-made seismic activities in the country and around the globe, to some extent on real-time basis. The Network System is made up of six remote digital stations that transmit data via satellite to the central observatory. Sensors used are 3× Trillium Compact and 3× Trillium 120PA with Trident digitizers. The department has also acquired strong motion equipment: Titan accelerometers with Taurus digitizers from Nanometrics. Three of each of these instruments have been installed at the Akosombo and Kpong hydrodams, and also at the Weija water supply dam. These instruments are used to monitor dams. The peak ground acceleration (PGA) values established from the analysed data from the accelerometers will be used to retrofit or carry out maintenance work of the dam structures to avoid collapse. Apart from these, the observatory also assesses and analyses seismic waveforms relevant to its needs from the Global Seismographic Network (GSN) system operated by the US Geological Survey. The Ghana Geological Survey, through its Seismic Network Observatory makes data available to its stakeholder institutions for earthquake disaster mitigation; reports on all aspects of

Seasonal variation of seismic ambient noise level at King Sejong Station, Antarctica

NASA Astrophysics Data System (ADS)

Lee, W.; Sheen, D.; Seo, K.; Yun, S.

2009-12-01

The generation of the secondary- or double-frequency (DF) microseisms with dominant frequencies between 0.1 and 0.5 Hz has been explained by nonlinear second-order pressure perturbations on the ocean bottom due to the interference of two ocean waves of equal wavelengths traveling in opposite directions. Korea Polar Research Institute (KOPRI) has been operating a broadband seismic station (KSJ1) at King George Island (KGI), Antarctica, since 2001. Examining the ambient seismic noise level for the period from 2006 to 2008 at KSJ1, we found a significant seasonal variation in the frequency range 0.1-0.5 Hz. Correlation of the DF peaks with significant ocean wave height and peak wave period models indicates that the oceanic infragravity waves in the Drake Passage is a possible source to excite the DF microseisms at KGI. Location of King Sejong Station, Antarctica Seasonal variations of DF peak, significant wave height, and peak wave period

Seismic noise level variation in South Korea

NASA Astrophysics Data System (ADS)

Sheen, D.; Shin, J.

2008-12-01

The variations of seismic background noise in South Korea have been investigated by means of power spectral analysis. The Korea Institute of Geoscience and Mineral Resources (KIGAM) and the Korea Meteorological Administation (KMA) have national wide seismic networks in South Korea, and, in the end of 2007, there are 30 broadband stations which have been operating for more than a year. In this study, we have estimated the power spectral density of seismic noise for 30 broadband stations from 2005 to 2007. Since we estimate PSDs from a large dataset of continuous waveform in this study, a robust PSD estimate of McNamara and Buland (2004) is used. In the frequency range 1-5 Hz, the diurnal variations of noise are observed at most of stations, which are especially larger at coastal stations and at insular than at inland. Some stations shows daily difference of diurnal variations, which represents that cultural activities contribute to the noise level of a station. The variation of number of triggered stations, however, shows that cultural noise has little influence on the detection capability of seismic network in South Korea. Seasonal variations are observed well in the range 0.1-0.5 Hz, while much less found in the frequency range 1-5 Hz. We observed that strong peaks in the range 0.1-0.5 Hz occur at the summer when Pacific typhoons are close to the Korean Peninsula.

TexNet seismic network performance and reported seismicity in West Texas

NASA Astrophysics Data System (ADS)

Savvaidis, A.; Lomax, A.; Aiken, C.; Young, B.; Huang, D.; Hennings, P.

2017-12-01

In 2015, the Texas State Legislature began funding the Texas Seismological Network (TexNet). Since then, 22 new permanent broadband three-component seismic stations have been added to 17 existing stations operated by various networks [US, N4, IM]. These stations together with 4 auxiliary stations, i.e. long term deployments of 20 sec portable stations, were deployed to provide a baseline of Texas seismicity. As soon as the deployment of the new permanent stations took place in West Texas, TexNet was able to detect and characterize smaller magnitude events than was possible before, i.e. M < 2.5. As a consequence, additional portable stations were installed in the area in order to better map the current seismicity level. During the different stages of station deployment, we monitored the seismic network performance and its ability to detect earthquake activity. We found that a key limitation to the network performance is industrial noise in West Texas. For example, during daytime, phase picking and event detection rates are much lower than during nighttime at noisy sites. Regarding seismicity, the high density portable station deployment close to the earthquake activity minimizes hypocentral location uncertainties. In addition, we examined the effects of different crustal velocity models in the area of study on hypocentral location using the local network first arrivals. Considerable differences in location were obtained, which shows the importance of local networks and/or reliable crustal velocity models for West Texas. Given the levels of seismicity in West Texas, a plan to continuously monitor the study area is under development.

Incorporating induced seismicity in the 2014 United States National Seismic Hazard Model: results of the 2014 workshop and sensitivity studies

USGS Publications Warehouse

Petersen, Mark D.; Mueller, Charles S.; Moschetti, Morgan P.; Hoover, Susan M.; Rubinstein, Justin L.; Llenos, Andrea L.; Michael, Andrew J.; Ellsworth, William L.; McGarr, Arthur F.; Holland, Austin A.; Anderson, John G.

2015-01-01

The U.S. Geological Survey National Seismic Hazard Model for the conterminous United States was updated in 2014 to account for new methods, input models, and data necessary for assessing the seismic ground shaking hazard from natural (tectonic) earthquakes. The U.S. Geological Survey National Seismic Hazard Model project uses probabilistic seismic hazard analysis to quantify the rate of exceedance for earthquake ground shaking (ground motion). For the 2014 National Seismic Hazard Model assessment, the seismic hazard from potentially induced earthquakes was intentionally not considered because we had not determined how to properly treat these earthquakes for the seismic hazard analysis. The phrases “potentially induced” and “induced” are used interchangeably in this report, however it is acknowledged that this classification is based on circumstantial evidence and scientific judgment. For the 2014 National Seismic Hazard Model update, the potentially induced earthquakes were removed from the NSHM’s earthquake catalog, and the documentation states that we would consider alternative models for including induced seismicity in a future version of the National Seismic Hazard Model. As part of the process of incorporating induced seismicity into the seismic hazard model, we evaluate the sensitivity of the seismic hazard from induced seismicity to five parts of the hazard model: (1) the earthquake catalog, (2) earthquake rates, (3) earthquake locations, (4) earthquake Mmax (maximum magnitude), and (5) earthquake ground motions. We describe alternative input models for each of the five parts that represent differences in scientific opinions on induced seismicity characteristics. In this report, however, we do not weight these input models to come up with a preferred final model. Instead, we present a sensitivity study showing uniform seismic hazard maps obtained by applying the alternative input models for induced seismicity. The final model will be released after

Characterization of site conditions for selected seismic stations in eastern part of Romania

NASA Astrophysics Data System (ADS)

Grecu, B.; Zaharia, B.; Diaconescu, M.; Bala, A.; Nastase, E.; Constantinescu, E.; Tataru, D.

2018-02-01

Strong motion data are essential for seismic hazard assessment. To correctly understand and use this kind of data is necessary to have a good knowledge of local site conditions. Romania has one of the largest strong motion networks in Europe with 134 real-time stations. In this work, we aim to do a comprehensive site characterization for eight of these stations located in the eastern part of Romania. We make use of a various seismological dataset and we perform ambient noise and earthquake-based investigations to estimate the background noise level, the resonance frequencies and amplification of each site. We also derive the Vs30 parameter from the surface shear-wave velocity profiles obtained through the inversion of the Rayleigh waves recorded in active seismic measurements. Our analyses indicate similar results for seven stations: high noise levels for frequencies larger than 1 Hz, well defined fundamental resonance at low frequencies (0.15-0.29 Hz), moderate amplification levels (up to 4 units) for frequencies between 0.15 and 5-7 Hz and same soil class (type C) according to the estimated Vs30 and Eurocode 8. In contrast, the eighth station for which the soil class is evaluated of type B exhibits a very good noise level for a wide range of frequencies (0.01-20 Hz), a broader fundamental resonance at high frequencies ( 8 Hz) and a flat amplification curve between 0.1 and 3-4 Hz.

Seismic-monitoring changes and the remote deployment of seismic stations (seismic spider) at Mount St. Helens, 2004-2005: Chapter 7 in A volcano rekindled: the renewed eruption of Mount St. Helens, 2004-2006

USGS Publications Warehouse

McChesney, Patrick J.; Couchman, Marvin R.; Moran, Seth C.; Lockhart, Andrew B.; Swinford, Kelly J.; LaHusen, Richard G.; Sherrod, David R.; Scott, William E.; Stauffer, Peter H.

2008-01-01

The instruments in place at the start of volcanic unrest at Mount St. Helens in 2004 were inadequate to record the large earthquakes and monitor the explosions that occurred as the eruption developed. To remedy this, new instruments were deployed and the short-period seismic network was modified. A new method of establishing near-field seismic monitoring was developed, using remote deployment by helicopter. The remotely deployed seismic sensor was a piezoelectric accelerometer mounted on a surface-coupled platform. Remote deployment enabled placement of stations within 250 m of the active vent.

Toward 2D Seismic Wavefield Monitoring: Seismic Gradiometry for Long-Period Seismogram and Short-Period Seismogram Envelope applied to the Hi-net Array

NASA Astrophysics Data System (ADS)

Maeda, T.; Nishida, K.; Takagi, R.; Obara, K.

2015-12-01

The high-sensitive seismograph network Japan (Hi-net) operated by National Research Institute for Earth Science and Disaster Prevention (NIED) has about 800 stations with average separation of 20 km. We can observe long-period seismic wave propagation as a 2D wavefield with station separations shorter than wavelength. In contrast, short-period waves are quite incoherent at stations, however, their envelope shapes resemble at neighbor stations. Therefore, we may be able to extract seismic wave energy propagation by seismogram envelope analysis. We attempted to characterize seismic waveform at long-period and its envelope at short-period as 2D wavefield by applying seismic gradiometry. We applied the seismic gradiometry to a synthetic long-period (20-50s) dataset prepared by numerical simulation in realistic 3D medium at the Hi-net station layout. Wave amplitude and its spatial derivatives are estimated by using data at nearby stations. The slowness vector, the radiation pattern and the geometrical spreading are extracted from estimated velocity, displacement and its spatial derivatives. For short-periods at shorter than 1 s, seismogram envelope shows temporal and spatial broadening through scattering by medium heterogeneity. It is expected that envelope shape may be coherent among nearby stations. Based on this idea, we applied the same method to the time-integration of seismogram envelope to estimate its spatial derivatives. Together with seismogram envelope, we succeeded in estimating the slowness vector from the seismogram envelope as well as long-period waveforms by synthetic test, without using phase information. Our preliminarily results show that the seismic gradiometry suits the Hi-net to extract wave propagation characteristics both at long and short periods. This method is appealing that it can estimate waves at homogeneous grid to monitor seismic wave as a wavefield. It is promising to obtain phase velocity variation from direct waves, and to grasp wave

Seismic Structure of Perth Basin (Australia) and surroundings from Passive Seismic Deployments

NASA Astrophysics Data System (ADS)

Issa, N.; Saygin, E.; Lumley, D. E.; Hoskin, T. E.

2016-12-01

We image the subsurface structure of Perth Basin, Western Australia and surroundings by using ambient seismic noise data from 14 seismic stations recently deployed by University of Western Australia (UWA) and other available permanent stations from Geoscience Australia seismic network and the Australian Seismometers in Schools program. Each of these 14 UWA seismic stations comprises a broadband sensor and a high fidelity 3-component 10 Hz geophone, recording in tandem at 250 Hz and 1000 Hz. The other stations used in this study are equipped with short period and broadband sensors. In addition, one shallow borehole station is operated with eight 3 component geophones at depths of between 2 and 44 m. The network is deployed to characterize natural seismicity in the basin and to try and identify any microseismic activity across Darling Fault Zone (DFZ), bounding the basin to the east. The DFZ stretches to approximately 1000 km north-south in Western Australia, and is one of the longest fault zones on the earth with a limited number of detected earthquakes. We use seismic noise cross- and auto-correlation methods to map seismic velocity perturbations across the basin and the transition from DFZ to the basin. Retrieved Green's functions are stable and show clear dispersed waveforms. Travel times of the surface wave Green's functions from noise cross-correlations are inverted with a two-step probabilistic framework to map the absolute shear wave velocities as a function of depth. The single station auto-correlations from the seismic noise yields P wave reflectivity under each station, marking the major discontinuities. Resulting images show the shear velocity perturbations across the region. We also quantify the variation of ambient seismic noise at different depths in the near surface using the geophones in the shallow borehole array.

Seismic Noise Analysis and Reduction through Utilization of Collocated Seismic and Atmospheric Sensors at the GRO Chile Seismic Network

NASA Astrophysics Data System (ADS)

Farrell, M. E.; Russo, R. M.

2013-12-01

The installation of Earthscope Transportable Array-style geophysical observatories in Chile expands open data seismic recording capabilities in the southern hemisphere by nearly 30%, and has nearly tripled the number of seismic stations providing freely-available data in southern South America. Through the use of collocated seismic and atmospheric sensors at these stations we are able to analyze how local atmospheric conditions generate seismic noise, which can degrade data in seismic frequency bands at stations in the ';roaring forties' (S latitudes). Seismic vaults that are climate-controlled and insulated from the local environment are now employed throughout the world in an attempt to isolate seismometers from as many noise sources as possible. However, this is an expensive solution that is neither practical nor possible for all seismic deployments; and also, the increasing number and scope of temporary seismic deployments has resulted in the collection and archiving of terabytes of seismic data that is affected to some degree by natural seismic noise sources such as wind and atmospheric pressure changes. Changing air pressure can result in a depression and subsequent rebound of Earth's surface - which generates low frequency noise in seismic frequency bands - and even moderate winds can apply enough force to ground-coupled structures or to the surface above the seismometers themselves, resulting in significant noise. The 10 stations of the permanent Geophysical Reporting Observatories (GRO Chile), jointly installed during 2011-12 by IRIS and the Chilean Servicio Sismológico, include instrumentation in addition to the standard three seismic components. These stations, spaced approximately 300 km apart along the length of the country, continuously record a variety of atmospheric data including infrasound, air pressure, wind speed, and wind direction. The collocated seismic and atmospheric sensors at each station allow us to analyze both datasets together, to

Integrate urban‐scale seismic hazard analyses with the U.S. National Seismic Hazard Model

USGS Publications Warehouse

Moschetti, Morgan P.; Luco, Nicolas; Frankel, Arthur; Petersen, Mark D.; Aagaard, Brad T.; Baltay, Annemarie S.; Blanpied, Michael; Boyd, Oliver; Briggs, Richard; Gold, Ryan D.; Graves, Robert; Hartzell, Stephen; Rezaeian, Sanaz; Stephenson, William J.; Wald, David J.; Williams, Robert A.; Withers, Kyle

2018-01-01

For more than 20 yrs, damage patterns and instrumental recordings have highlighted the influence of the local 3D geologic structure on earthquake ground motions (e.g., M">M 6.7 Northridge, California, Gao et al., 1996; M">M 6.9 Kobe, Japan, Kawase, 1996; M">M 6.8 Nisqually, Washington, Frankel, Carver, and Williams, 2002). Although this and other local‐scale features are critical to improving seismic hazard forecasts, historically they have not been explicitly incorporated into the U.S. National Seismic Hazard Model (NSHM, national model and maps), primarily because the necessary basin maps and methodologies were not available at the national scale. Instead,...

Seismic databases of The Caucasus

NASA Astrophysics Data System (ADS)

Gunia, I.; Sokhadze, G.; Mikava, D.; Tvaradze, N.; Godoladze, T.

2012-12-01

The Caucasus is one of the active segments of the Alpine-Himalayan collision belt. The region needs continues seismic monitoring systems for better understanding of tectonic processes going in the region. Seismic Monitoring Center of Georgia (Ilia State University) is operating the digital seismic network of the country and is also collecting and exchanging data with neighboring countries. The main focus of our study was to create seismic database which is well organized, easily reachable and is convenient for scientists to use. The seismological database includes the information about more than 100 000 earthquakes from the whole Caucasus. We have to mention that it includes data from analog and digital seismic networks. The first analog seismic station in Georgia was installed in 1899 in the Caucasus in Tbilisi city. The number of analog seismic stations was increasing during next decades and in 1980s about 100 analog stations were operated all over the region. From 1992 due to political and economical situation the number of stations has been decreased and in 2002 just two analog equipments was operated. New digital seismic network was developed in Georgia since 2003. The number of digital seismic stations was increasing and in current days there are more than 25 digital stations operating in the country. The database includes the detailed information about all equipments installed on seismic stations. Database is available online. That will make convenient interface for seismic data exchange data between Caucasus neighboring countries. It also makes easier both the seismic data processing and transferring them to the database and decreases the operator's mistakes during the routine work. The database was created using the followings: php, MySql, Javascript, Ajax, GMT, Gmap, Hypoinverse.

An assessment of seismic monitoring in the United States; requirement for an Advanced National Seismic System

USGS Publications Warehouse

,

1999-01-01

This report assesses the status, needs, and associated costs of seismic monitoring in the United States. It sets down the requirement for an effective, national seismic monitoring strategy and an advanced system linking national, regional, and urban monitoring networks. Modernized seismic monitoring can provide alerts of imminent strong earthquake shaking; rapid assessment of distribution and severity of earthquake shaking (for use in emergency response); warnings of a possible tsunami from an offshore earthquake; warnings of volcanic eruptions; information for correctly characterizing earthquake hazards and for improving building codes; and data on response of buildings and structures during earthquakes, for safe, cost-effective design, engineering, and construction practices in earthquake-prone regions.

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.

The improved broadband Real-Time Seismic Network in Romania

NASA Astrophysics Data System (ADS)

Neagoe, C.; Ionescu, C.

2009-04-01

Starting with 2002 the National Institute for Earth Physics (NIEP) has developed its real-time digital seismic network. This network consists of 96 seismic stations of which 48 broad band and short period stations and two seismic arrays are transmitted in real-time. The real time seismic stations are equipped with Quanterra Q330 and K2 digitizers, broadband seismometers (STS2, CMG40T, CMG 3ESP, CMG3T) and strong motions sensors Kinemetrics episensors (+/- 2g). SeedLink and AntelopeTM (installed on MARMOT) program packages are used for real-time (RT) data acquisition and exchange. The communication from digital seismic stations to the National Data Center in Bucharest is assured by 5 providers (GPRS, VPN, satellite communication, radio lease line and internet), which will assure the back-up communications lines. The processing centre runs BRTT's AntelopeTM 4.10 data acquisition and processing software on 2 workstations for real-time processing and post processing. The Antelope Real-Time System is also providing automatic event detection, arrival picking, event location and magnitude calculation. It provides graphical display and reporting within near-real-time after a local or regional event occurred. Also at the data center was implemented a system to collect macroseismic information using the internet on which macro seismic intensity maps are generated. In the near future at the data center will be install Seiscomp 3 data acquisition processing software on a workstation. The software will run in parallel with Antelope software as a back-up. The present network will be expanded in the near future. In the first half of 2009 NIEP will install 8 additional broad band stations in Romanian territory, which also will be transmitted to the data center in real time. The Romanian Seismic Network is permanently exchanging real -time waveform data with IRIS, ORFEUS and different European countries through internet. In Romania, magnitude and location of an earthquake are now

High-resolution earthquake relocation in the Fort Worth and Permian Basins using regional seismic stations

NASA Astrophysics Data System (ADS)

Ogwari, P.; DeShon, H. R.; Hornbach, M.

2017-12-01

Post-2008 earthquake rate increases in the Central United States have been associated with large-scale subsurface disposal of waste-fluids from oil and gas operations. The beginning of various earthquake sequences in Fort Worth and Permian basins have occurred in the absence of seismic stations at local distances to record and accurately locate hypocenters. Most typically, the initial earthquakes have been located using regional seismic network stations (>100km epicentral distance) and using global 1D velocity models, which usually results in large location uncertainty, especially in depth, does not resolve magnitude <2.5 events, and does not constrain the geometry of the activated fault(s). Here, we present a method to better resolve earthquake occurrence and location using matched filters and regional relative location when local data becomes available. We use the local distance data for high-resolution earthquake location, identifying earthquake templates and accurate source-station raypath velocities for the Pg and Lg phases at regional stations. A matched-filter analysis is then applied to seismograms recorded at US network stations and at adopted TA stations that record the earthquakes before and during the local network deployment period. Positive detections are declared based on manual review of associated with P and S arrivals on local stations. We apply hierarchical clustering to distinguish earthquakes that are both spatially clustered and spatially separated. Finally, we conduct relative earthquake and earthquake cluster location using regional station differential times. Initial analysis applied to the 2008-2009 DFW airport sequence in north Texas results in time continuous imaging of epicenters extending into 2014. Seventeen earthquakes in the USGS earthquake catalog scattered across a 10km2 area near DFW airport are relocated onto a single fault using these approaches. These techniques will also be applied toward imaging recent earthquakes in the

Reevaluation of the Seismicity and seismic hazards of Northeastern Libya

NASA Astrophysics Data System (ADS)

Ben Suleman, abdunnur; Aousetta, Fawzi

2014-05-01

Libya, located at the northern margin of the African continent, underwent many episodes of orogenic activities. These episodes of orogenic activities affected and shaped the geological setting of the country. This study represents a detailed investigation that aims to focus on the seismicity and its implications on earthquake hazards of Northeastern Libya. At the end of year 2005 the Libyan National Seismological Network starts functioning with 15 stations. The Seismicity of the area under investigation was reevaluated using data recorded by the recently established network. The Al-Maraj earthquake occurred in May 22nd 2005was analyzed. This earthquake was located in a known seismically active area. This area was the sight of the well known 1963 earthquake that kills over 200 people. Earthquakes were plotted and resulting maps were interpreted and discussed. The level of seismic activity is higher in some areas, such as the city of Al-Maraj. The offshore areas north of Al-Maraj seem to have higher seismic activity. It is highly recommended that the recent earthquake activity is considered in the seismic hazard assessments for the northeastern part of Libya.

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

Seismic hazard in the Nation's breadbasket

USGS Publications Warehouse

Boyd, Oliver; Haller, Kathleen; Luco, Nicolas; Moschetti, Morgan P.; Mueller, Charles; Petersen, Mark D.; Rezaeian, Sanaz; Rubinstein, Justin L.

2015-01-01

The USGS National Seismic Hazard Maps were updated in 2014 and included several important changes for the central United States (CUS). Background seismicity sources were improved using a new moment-magnitude-based catalog; a new adaptive, nearest-neighbor smoothing kernel was implemented; and maximum magnitudes for background sources were updated. Areal source zones developed by the Central and Eastern United States Seismic Source Characterization for Nuclear Facilities project were simplified and adopted. The weighting scheme for ground motion models was updated, giving more weight to models with a faster attenuation with distance compared to the previous maps. Overall, hazard changes (2% probability of exceedance in 50 years, across a range of ground-motion frequencies) were smaller than 10% in most of the CUS relative to the 2008 USGS maps despite new ground motion models and their assigned logic tree weights that reduced the probabilistic ground motions by 5–20%.

Ambient seismic noise monitoring of the Super-Sauze landslide from a very dense temporary seismic array

NASA Astrophysics Data System (ADS)

Chtouki, Toufik; Vergne, Jerome; Provost, Floriane; Malet, Jean-Philippe; Burtin, Arnaud; Hibert, Clément

2017-04-01

The Super-Sauze landslide is located on the southern part of the Barcelonnette Basin (French Alps) and has developed in a soft clay-shale environment. It is one of the four sites continuously monitored through a wide variety of geophysical and hydro-geological techniques in the framework of the OMIV French national landslide observatory. From early June to mid-July 2016, a temporary dense seismic array has been installed in the most active part of the landslide and at its surroundings. 50 different sites with an average inter-station distance of 50m have been instrumented with 150 miniaturized and autonomous seismic stations (Zland nodes), allowing a continuous record of the seismic signal at frequencies higher than 0.2Hz over an almost regular grid. Concurrently, a Ground-Based InSAR device allowed for a precise and continuous monitoring of the surface deformation. Overall, this experiment is intended to better characterize the spatio-temporal evolution of the deformation processes related to various type of forcing. We analyze the continuous records of ambient seismic noise recorded by the dense array. Using power spectral densities, we characterize the various types of natural and anthropogenic seismic sources, including the effect of water turbulence and bedload transport in the small nearby torrents. We also compute the correlation of the ambient diffuse seismic noise in various frequency bands for the 2448 station pairs to recover the empirical Green functions between them. The temporal evolution of the coda part of these noise correlation functions allows monitoring and localizing shear wave velocity variations in the sliding mass. Here we present some preliminary results of this analysis and compare the seismic variations to meteorological data and surface deformation.

Romanian Data Center: A modern way for seismic monitoring

NASA Astrophysics Data System (ADS)

Neagoe, Cristian; Marius Manea, Liviu; Ionescu, Constantin

2014-05-01

The main seismic survey of Romania is performed by the National Institute for Earth Physics (NIEP) which operates a real-time digital seismic network. The NIEP real-time network currently consists of 102 stations and two seismic arrays equipped with different high quality digitizers (Kinemetrics K2, Quanterra Q330, Quanterra Q330HR, PS6-26, Basalt), broadband and short period seismometers (CMG3ESP, CMG40T, KS2000, KS54000, KS2000, CMG3T,STS2, SH-1, S13, Mark l4c, Ranger, gs21, Mark l22) and acceleration sensors (Episensor Kinemetrics). The data are transmitted at the National Data Center (NDC) and Eforie Nord (EFOR) Seismic Observatory. EFOR is the back-up for the NDC and also a monitoring center for the Black Sea tsunami events. NIEP is a data acquisition node for the seismic network of Moldova (FDSN code MD) composed of five seismic stations. NIEP has installed in the northern part of Bulgaria eight seismic stations equipped with broadband sensors and Episensors and nine accelerometers (Episensors) installed in nine districts along the Danube River. All the data are acquired at NIEP for Early Warning System and for primary estimation of the earthquake parameters. The real-time acquisition (RT) and data exchange is done by Antelope software and Seedlink (from Seiscomp3). The real-time data communication is ensured by different types of transmission: GPRS, satellite, radio, Internet and a dedicated line provided by a governmental network. For data processing and analysis at the two data centers Antelope 5.2 TM is being used running on 3 workstations: one from a CentOS platform and two on MacOS. Also a Seiscomp3 server stands as back-up for Antelope 5.2 Both acquisition and analysis of seismic data systems produce information about local and global parameters of earthquakes. In addition, Antelope is used for manual processing (event association, calculation of magnitude, creating a database, sending seismic bulletins, calculation of PGA and PGV, etc.), generating

Seismic source characterization for the 2014 update of the U.S. National Seismic Hazard Model

USGS Publications Warehouse

Moschetti, Morgan P.; Powers, Peter; Petersen, Mark D.; Boyd, Oliver; Chen, Rui; Field, Edward H.; Frankel, Arthur; Haller, Kathleen; Harmsen, Stephen; Mueller, Charles S.; Wheeler, Russell; Zeng, Yuehua

2015-01-01

We present the updated seismic source characterization (SSC) for the 2014 update of the National Seismic Hazard Model (NSHM) for the conterminous United States. Construction of the seismic source models employs the methodology that was developed for the 1996 NSHM but includes new and updated data, data types, source models, and source parameters that reflect the current state of knowledge of earthquake occurrence and state of practice for seismic hazard analyses. We review the SSC parameterization and describe the methods used to estimate earthquake rates, magnitudes, locations, and geometries for all seismic source models, with an emphasis on new source model components. We highlight the effects that two new model components—incorporation of slip rates from combined geodetic-geologic inversions and the incorporation of adaptively smoothed seismicity models—have on probabilistic ground motions, because these sources span multiple regions of the conterminous United States and provide important additional epistemic uncertainty for the 2014 NSHM.

Newberry Seismic Deployment Fieldwork Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, J; Templeton, D C

2012-03-21

This report summarizes the seismic deployment of Lawrence Livermore National Laboratory (LLNL) Geotech GS-13 short-period seismometers at the Newberry Enhanced Geothermal System (EGS) Demonstration site located in Central Oregon. This Department of Energy (DOE) demonstration project is managed by AltaRock Energy Inc. AltaRock Energy had previously deployed Geospace GS-11D geophones at the Newberry EGS Demonstration site, however the quality of the seismic data was somewhat low. The purpose of the LLNL deployment was to install more sensitive sensors which would record higher quality seismic data for use in future seismic studies, such as ambient noise correlation, matched field processing earthquakemore » detection studies, and general EGS microearthquake studies. For the LLNL deployment, seven three-component seismic stations were installed around the proposed AltaRock Energy stimulation well. The LLNL seismic sensors were connected to AltaRock Energy Gueralp CMG-DM24 digitizers, which are powered by AltaRock Energy solar panels and batteries. The deployment took four days in two phases. In phase I, the sites were identified, a cavity approximately 3 feet deep was dug and a flat concrete pad oriented to true North was made for each site. In phase II, we installed three single component GS-13 seismometers at each site, quality controlled the data to ensure that each station was recording data properly, and filled in each cavity with native soil.« less

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.

Surface Wave Dispersion Measurements and Tomography From Ambient Seismic Noise in China

DTIC Science & Technology

2007-12-20

Recovering the Green’s function from field - field correlations in an open scattering medium (L), J. Acoust. Soc. Amer. 113 (6), 2973- 2976, 2003. Eagle, D...The basic approach can be traced back much earlier studies of random fields in seismology (Aki, 1957; Toksoz, 1964; Claerbout, 1968), in...Seismic Network (CNDSN), Center of China Digital Seismic Network (CCDSN) stations, and China Seismic Network ( CSN ). We refer here as China National

Romanian Educational Seismic Network Project

NASA Astrophysics Data System (ADS)

Tataru, Dragos; Ionescu, Constantin; Zaharia, Bogdan; Grecu, Bogdan; Tibu, Speranta; Popa, Mihaela; Borleanu, Felix; Toma, Dragos; Brisan, Nicoleta; Georgescu, Emil-Sever; Dobre, Daniela; Dragomir, Claudiu-Sorin

2013-04-01

Romania is one of the most active seismic countries in Europe, with more than 500 earthquakes occurring every year. The seismic hazard of Romania is relatively high and thus understanding the earthquake phenomena and their effects at the earth surface represents an important step toward the education of population in earthquake affected regions of the country and aims to raise the awareness about the earthquake risk and possible mitigation actions. In this direction, the first national educational project in the field of seismology has recently started in Romania: the ROmanian EDUcational SEISmic NETwork (ROEDUSEIS-NET) project. It involves four partners: the National Institute for Earth Physics as coordinator, the National Institute for Research and Development in Construction, Urban Planning and Sustainable Spatial Development " URBAN - INCERC" Bucharest, the Babeş-Bolyai University (Faculty of Environmental Sciences and Engineering) and the software firm "BETA Software". The project has many educational, scientific and social goals. The main educational objectives are: training students and teachers in the analysis and interpretation of seismological data, preparing of several comprehensive educational materials, designing and testing didactic activities using informatics and web-oriented tools. The scientific objective is to introduce into schools the use of advanced instruments and experimental methods that are usually restricted to research laboratories, with the main product being the creation of an earthquake waveform archive. Thus a large amount of such data will be used by students and teachers for educational purposes. For the social objectives, the project represents an effective instrument for informing and creating an awareness of the seismic risk, for experimentation into the efficacy of scientific communication, and for an increase in the direct involvement of schools and the general public. A network of nine seismic stations with SEP seismometers

Emergency seismic and CGPS networks: a first employment for the L'Aquila Mw 6.3 earthquake

NASA Astrophysics Data System (ADS)

Abruzzese, L.; Avallone, A.; Cecere, G.; Cattaneo, M.; Cardinale, V.; Castagnozzi, A.; Cogliano, R.; Criscuoli, F.; D'Agostino, N.; D'Ambrosio, C.; de Luca, G.; D'Anastasio, E.; Falco, L.; Flammia, V.; Migliari, F.; Minichiello, F.; Memmolo, A.; Monachesi, G.; Moschillo, R.; Pignone, M.; Pucillo, S.; Selvaggi, G.; Zarrilli, L.; Delladio, A.; Govoni, A.; Franceschi, D.; de Martin, M.; Moretti, M.

2009-12-01

During the last 2 years, the Istituto Nazionale di Geofisica e Vulcanologia (INGV) developed an important real-time temporary seismic network infrastructure in order to densify the Italian National Seismic Network in epicentral areas thus enhancing the localization of the micro-seismicity after main earthquake events. This real-time temporary seismic network is constituted by various mobile and autonomous seismic stations that in group of three are telemetered to a Very Small Aperture Terminal (VSAT). This system uses a dedicated bandwidth on UHF, Wi-Fi and satellite frequency that allows the data flow in real-time at INGV centre in Rome (and Grottaminarda as backup center). The deployment of the seismic network is managed in a geographical information systems (GIS) by particular scenarios that visualizes, for the epicentral area, information about instrumental seismicity, seismic risk, macroseismic felts and territorial data. Starting from digital terrain model, the surface spatial analysis (Viewshed, Observer Point) allows the geographic arrangement of the stations and relative scenarios. The April, 6th, 2009 Mw 6.3 L'Aquila destructive earthquake represented the first real-case to test the entire emergency seismic network infrastructure. Less than 6 hours after the earthquake occurrence, a first accelerometer station was already sending data at INGV seismic monitoring headquarters. A total number of 9 seismic stations have been installed within 3 days after the earthquake. Furthermore, 5 permanent GPS stations have been installed in the epicentral area within 1 to 9 days after the main shock to detect the post-seismic deformation induced by the earthquake. We will show and describe the details of the Emergency Seismic Network infrastructure, and the first results from the collected data.

Romanian Complex Data Center for Dense Seismic network

NASA Astrophysics Data System (ADS)

Neagoe, Cristian; Ionescu, Constantin; Marius Manea, Liviu

2010-05-01

Since 2002 the National Institute for Earth Physics (NIEP) developed its own real-time digital seismic network: consisting of 96 seismic stations of which 35 are broadband sensors and 24 stations equipped with short period sensors and two arrays earthquakes that transmit data in real time at the National Data Center (NDC) and Eforie Nord (EFOR) Seismic Observatory. EFOR is the back-up for the NDC and also a monitoring center for Black Sea tsunamis. Seismic stations are equipped with Quanterra Q330 and K2 digitizers, broadband seismometers (STS2, CMG40T, CMG 3ESP, CMG3T) and acceleration sensors Episensor Kinemetrics (+ / - 2G). SeedLink who is a part of Seiscomp2.5 and Antelope are software packages used for acquisition in real time (RT) and for data exchange. Communication of digital seismic stations to the National Data Center in Bucharest and Seismic Observatory Eforie Nord is assured by 5 providers (GPRS, VPN, satellite radio and Internet communication). For acquisition and data processing at the two centers of reception and processing is used AntelopeTM 4.11 running on 2 workstations: one for real-time and other for offline processing and also a Seiscomp 3 server that works as back-up for Antelope 4.11 Both acquisition and analysis of seismic data systems produced information about local and global parameters of earthquakes, in addition Antelope is used for manual processing (association events, the calculation of magnitude, creating a database, sending seismic bulletins, calculation of PGA and PGV , etc.), generating ShakeMap products and interacts with global data centers. In order to make all this information easily available across the Web and also lay the grounds for a more modular and flexible development environment the National Data Center developed tools to enable centralizing of data from software such as Antelope which is using a dedicated database system ( Datascope, a database system based on text files ) to a more general-purpose database, My

Earthquake Monitoring: SeisComp3 at the Swiss National Seismic Network

NASA Astrophysics Data System (ADS)

Clinton, J. F.; Diehl, T.; Cauzzi, C.; Kaestli, P.

2011-12-01

The Swiss Seismological Service (SED) has an ongoing responsibility to improve the seismicity monitoring capability for Switzerland. This is a crucial issue for a country with low background seismicity but where a large M6+ earthquake is expected in the next decades. With over 30 stations with spacing of ~25km, the SED operates one of the densest broadband networks in the world, which is complimented by ~ 50 realtime strong motion stations. The strong motion network is expected to grow with an additional ~80 stations over the next few years. Furthermore, the backbone of the network is complemented by broadband data from surrounding countries and temporary sub-networks for local monitoring of microseismicity (e.g. at geothermal sites). The variety of seismic monitoring responsibilities as well as the anticipated densifications of our network demands highly flexible processing software. We are transitioning all software to the SeisComP3 (SC3) framework. SC3 is a fully featured automated real-time earthquake monitoring software developed by GeoForschungZentrum Potsdam in collaboration with commercial partner, gempa GmbH. It is in its core open source, and becoming a community standard software for earthquake detection and waveform processing for regional and global networks across the globe. SC3 was originally developed for regional and global rapid monitoring of potentially tsunamagenic earthquakes. In order to fulfill the requirements of a local network recording moderate seismicity, SED has tuned configurations and added several modules. In this contribution, we present our SC3 implementation strategy, focusing on the detection and identification of seismicity on different scales. We operate several parallel processing "pipelines" to detect and locate local, regional and global seismicity. Additional pipelines with lower detection thresholds can be defined to monitor seismicity within dense subnets of the network. To be consistent with existing processing

Global Seismic Cross-Correlation Results: Characterizing Repeating Seismic Events

NASA Astrophysics Data System (ADS)

Vieceli, R.; Dodge, D. A.; Walter, W. R.

2016-12-01

Increases in seismic instrument quality and coverage have led to increased knowledge of earthquakes, but have also revealed the complex and diverse nature of earthquake ruptures. Nonetheless, some earthquakes are sufficiently similar to each other that they produce correlated waveforms. Such repeating events have been used to investigate interplate coupling of subduction zones [e.g. Igarashi, 2010; Yu, 2013], study spatio-temporal changes in slip rate at plate boundaries [e.g. Igarashi et al., 2003], observe variations in seismic wave propagation velocities in the crust [e.g. Schaff and Beroza, 2004; Sawazaki et al., 2015], and assess inner core rotation [e.g. Yu, 2016]. The characterization of repeating events on a global scale remains a very challenging problem. An initial global seismic cross-correlation study used over 310 million waveforms from nearly 3.8 million events recorded between 1970 and 2013 to determine an initial look at global correlated seismicity [Dodge and Walter, 2015]. In this work, we analyze the spatial and temporal distribution of the most highly correlated event clusters or "multiplets" from the Dodge and Walter [2015] study. We examine how the distributions and characteristics of multiplets are effected by tectonic environment, source-station separation, and frequency band. Preliminary results suggest that the distribution of multiplets does not correspond to the tectonic environment in any obvious way, nor do they always coincide with the occurrence of large earthquakes. Future work will focus on clustering correlated pairs and working to reduce the bias introduced by non-uniform seismic station coverage and data availability. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Sources of high frequency seismic noise: insights from a dense network of ~250 stations in northern Alsace (France)

NASA Astrophysics Data System (ADS)

Vergne, Jerome; Blachet, Antoine; Lehujeur, Maximilien

2015-04-01

Monitoring local or regional seismic activity requires stations having a low level of background seismic noise at frequencies higher than few tenths of Hertz. Network operators are well aware that the seismic quality of a site depends on several aspects, among them its geological setting and the proximity of roads, railways, industries or trees. Often, the impact of each noise source is only qualitatively known which precludes estimating the quality of potential future sites before they are tested or installed. Here, we want to take advantage of a very dense temporary network deployed in Northern Alsace (France) to assess the effect of various kinds of potential sources on the level of seismic noise observed in the frequency range 0.2-50 Hz. In September 2014, more than 250 seismic stations (FairfieldNodal@ Zland nodes with 10Hz vertical geophone) have been installed every 1.5 km over a ~25km diameter disc centred on the deep geothermal sites of Soultz-sous-Forêts and Rittershoffen. This region exhibits variable degrees of human imprints from quite remote areas to sectors with high traffic roads and big villages. It also encompasses both the deep sedimentary basin of the Rhine graben and the piedmont of the Vosges massif with exposed bedrock. For each site we processed the continuous data to estimate probability density functions of the power spectral densities. At frequencies higher than 1 Hz most sites show a clear temporal modulation of seismic noise related to human activity with the well-known variations between day and night and between weekdays and weekends. Moreover we observe a clear evolution of the spatial distribution of seismic noise levels with frequency. Basically, between 0.5 and 4 Hz the geological setting modulates the level of seismic noise. At higher frequencies, the amplitude of seismic noise appears mostly related to the distance to nearby roads. Based on road maps and traffic estimation, a forward approach is performed to model the induced

Preliminary consideration on the seismic actions recorded during the 2016 Central Italy seismic sequence

NASA Astrophysics Data System (ADS)

Carlo Ponzo, Felice; Ditommaso, Rocco; Nigro, Antonella; Nigro, Domenico S.; Iacovino, Chiara

2017-04-01

After the Mw 6.0 mainshock of August 24, 2016 at 03.36 a.m. (local time), with the epicenter located between the towns of Accumoli (province of Rieti), Amatrice (province of Rieti) and Arquata del Tronto (province of Ascoli Piceno), several activities were started in order to perform some preliminary evaluations on the characteristics of the recent seismic sequence in the areas affected by the earthquake. Ambient vibration acquisitions have been performed using two three-directional velocimetric synchronized stations, with a natural frequency equal to 0.5Hz and a digitizer resolution of equal to 24bit. The activities are continuing after the events of the seismic sequence of October 26 and October 30, 2016. In this paper, in order to compare recorded and code provision values in terms of peak (PGA, PGV and PGD), spectral and integral (Housner Intensity) seismic parameters, several preliminary analyses have been performed on accelerometric time-histories acquired by three near fault station of the RAN (Italian Accelerometric Network): Amatrice station (station code AMT), Norcia station (station code NRC) and Castelsantangelo sul Nera station (station code CNE). Several comparisons between the elastic response spectra derived from accelerometric recordings and the elastic demand spectra provided by the Italian seismic code (NTC 2008) have been performed. Preliminary results retrieved from these analyses highlight several apparent difference between experimental data and conventional code provision. Then, the ongoing seismic sequence appears compatible with the historical seismicity in terms of integral parameters, but not in terms of peak and spectral values. It seems appropriate to reconsider the necessity to revise the simplified design approach based on the conventional spectral values. Acknowledgements This study was partially funded by the Italian Department of Civil Protection within the project DPC-RELUIS 2016 - RS4 ''Seismic observatory of structures and

Site selection for the future stations of the french permanent broadband network

NASA Astrophysics Data System (ADS)

Vergne, Jérôme; Charade, Olivier

2013-04-01

RESIF (REseau SIsmologique et géodésique Français) is a new French research infrastructure dedicated to the observation of earth deformation based on seismic and geodetic instruments mainly located in France. One of its major component, called RESIF-CLB (Construction Large Bande), is devoted to the evolution of the permanent seismic broadband network in metropolitan France with the objective to complement the 45 existing stations with ~155 new stations within the next eight years. This network will be used for various scientific objectives including deep structures imaging and national seismicity monitoring. The chosen network topology consists in a backbone of homogeneously distributed stations (long wavelength array) completed by additional stations in seismically active regions. Management of the RESIF-CLB project is carried out by the technical division of INSU (Institut National des Sciences de l'Univers) who will rely on eight regional observatories and the CEA-LDG for the construction and operation of the stations. To optimize the performance of the network, we put a strong emphasis on the standardization of the stations in term of vault types, scientific and technical instrumentation and operation procedures. We also set up a procedure for site selection requiring that every potential site has to be tested for at least 3 weeks with a minimalist installation. Analysis of the continuous ambient noise records is then included in a standardized report submitted to all committed partners for acceptance. During the last two years, about 60 potential new sites have been tested, spanning various places and environments. We present a review of the seismic noise measurements at these sites and discuss the influence of different types of noise sources depending on the frequency band of interest. For example, we show that regional population distribution can be used as a proxy to infer the noise level at frequencies higher than 1 Hz. Based on similar noise analyses

Geothermal Induced Seismicity National Environmental Policy Act Review

DOE Office of Scientific and Technical Information (OSTI.GOV)

Levine, Aaron L; Cook, Jeffrey J; Beckers, Koenraad J

In 2016, the U.S. Bureau of Land Management (BLM) contracted with the National Renewable Energy Laboratory (NREL) to assist the BLM in developing and building upon tools to better understand and evaluate induced seismicity caused by geothermal projects. This review of NEPA documents for four geothermal injection or EGS projects reveals the variety of approaches to analyzing and mitigating induced seismicity. With the exception of the Geysers, where induced seismicity has been observed and monitored for an extended period of time due to large volumes of water being piped in to recharge the hydrothermal reservoir, induced seismicity caused by geothermalmore » projects is a relative new area of study. As this review highlights, determining the level of mitigation required for induced seismic events has varied based on project location, when the review took place, whether the project utilized the International Energy Agency or DOE IS protocols, and the federal agency conducting the review. While the NEPA reviews were relatively consistent for seismic monitoring and historical evaluation of seismic events near the project location, the requirements for public outreach and mitigation for induced seismic events once stimulation has begun varied considerably between the four projects. Not all of the projects were required to notify specific community groups or local government entities before beginning the project, and only one of the reviews specifically stated the project proponent would hold meetings with the public to answer questions or address concerns.« less

Application of the dynamic calibration method to international monitoring system stations in Central Asia using natural seismicity data

NASA Astrophysics Data System (ADS)

Kedrov, O. K.; Kedrov, E. O.; Sergeyeva, N. A.; Zabarinskaya, L. P.; Gordon, V. R.

2008-05-01

The dynamic calibration method (DCM), using natural seismicity data and initially elaborated in [Kedrov, 2001; Kedrov et al., 2001; Kedrov and Kedrov, 2003], is applied to International Monitoring System (IMS) stations in Central Asia. The algorithm of the method is refined and a program is designed for calibrating diagnostic parameters (discriminants) that characterize a seismic source on the source-station traces. The DCM calibration of stations in relation to the region under study is performed by the choice of attenuation coefficients that adapt the diagnostic parameters to the conditions in a reference region. In this method, the stable Eurasia region is used as the latter. The calibration used numerical data samples taken from the archive of the International Data Centre (IDC) for the IMS stations MKAR, BVAR, EIL, ASF, and CMAR. In this paper, we used discriminants in the spectral and time domains that have the form D_i = X_i - a_m m_b - b_Δ log Δ and are independent of the magnitude m b and the epicentral distance Δ; these discriminants were elaborated in [Kedrov et al., 1990; Kedrov and Lyuke, 1999] on the basis of a method used for identification of events at regional distances in Eurasia. Prerequisites of the DCM are the assumptions that the coefficient a m is regionindependent and the coefficient b Δ depends only on the geotectonic characteristics of the medium and does not depend on the source type. Thus, b Δ can be evaluated only from a sample of earthquakes in the region studied; it is used for adapting the discriminants D( X i ) in the region studied to the reference region. The algorithm is constructed in such a way that corrected values of D( X i) are calculated from the found values of the calibration coefficients b Δ, after which natural events in the region under study are selected by filtering. Empirical estimates of the filtering efficiency as a function of a station vary in a range of 95 100%. The DCM was independently tested using

Application of continuous seismic-reflection techniques to delineate paleochannels beneath the Neuse River at US Marine Corps Air Station, Cherry Point, North Carolina

USGS Publications Warehouse

Cardinell, Alex P.

1999-01-01

A continuous seismic-reflection profiling survey was conducted by the U.S. Geological Survey on the Neuse River near the Cherry Point Marine Corps Air Station during July 7-24, 1998. Approximately 52 miles of profiling data were collected during the survey from areas northwest of the Air Station to Flanner Beach and southeast to Cherry Point. Positioning of the seismic lines was done by using an integrated navigational system. Data from the survey were used to define and delineate paleochannel alignments under the Neuse River near the Air Station. These data also were correlated with existing surface and borehole geophysical data, including vertical seismic-profiling velocity data collected in 1995. Sediments believed to be Quaternary in age were identified at varying depths on the seismic sections as undifferentiated reflectors and lack the lateral continuity of underlying reflectors believed to represent older sediments of Tertiary age. The sediments of possible Quaternary age thicken to the southeast. Paleochannels of Quaternary age and varying depths were identified beneath the Neuse River estuary. These paleochannels range in width from 870 feet to about 6,900 feet. Two zones of buried paleochannels were identified in the continuous seismic-reflection profiling data. The eastern paleochannel zone includes two large superimposed channel features identified during this study and in re-interpreted 1995 land seismic-reflection data. The second paleochannel zone, located west of the first paleochannel zone, contains several small paleochannels near the central and south shore of the Neuse River estuary between Slocum Creek and Flanner Beach. This second zone of channel features may be continuous with those mapped by the U.S. Geological Survey in 1995 using land seismic-reflection data on the southern end of the Air Station. Most of the channels were mapped at the Quaternary-Tertiary sediment boundary. These channels appear to have been cut into the older sediments

Documentation for the 2008 Update of the United States National Seismic Hazard Maps

USGS Publications Warehouse

Petersen, Mark D.; Frankel, Arthur D.; Harmsen, Stephen C.; Mueller, Charles S.; Haller, Kathleen M.; Wheeler, Russell L.; Wesson, Robert L.; Zeng, Yuehua; Boyd, Oliver S.; Perkins, David M.; Luco, Nicolas; Field, Edward H.; Wills, Chris J.; Rukstales, Kenneth S.

2008-01-01

The 2008 U.S. Geological Survey (USGS) National Seismic Hazard Maps display earthquake ground motions for various probability levels across the United States and are applied in seismic provisions of building codes, insurance rate structures, risk assessments, and other public policy. This update of the maps incorporates new findings on earthquake ground shaking, faults, seismicity, and geodesy. The resulting maps are derived from seismic hazard curves calculated on a grid of sites across the United States that describe the frequency of exceeding a set of ground motions. The USGS National Seismic Hazard Mapping Project developed these maps by incorporating information on potential earthquakes and associated ground shaking obtained from interaction in science and engineering workshops involving hundreds of participants, review by several science organizations and State surveys, and advice from two expert panels. The National Seismic Hazard Maps represent our assessment of the 'best available science' in earthquake hazards estimation for the United States (maps of Alaska and Hawaii as well as further information on hazard across the United States are available on our Web site at http://earthquake.usgs.gov/research/hazmaps/).

Cultural noise and the night-day asymmetry of the seismic activity recorded at the Bunker-East (BKE) Vesuvian Station

NASA Astrophysics Data System (ADS)

Scafetta, Nicola; Mazzarella, Adriano

2018-01-01

Mazzarella and Scafetta (2016) showed that the seismic activity recorded at the Bunker-East (BKE) Vesuvian station from 1999 to 2014 suggests a higher nocturnal seismic activity. However, this station is located at about 50 m from the main road to the volcano's crater and since 2009 its seismograms also record a significant diurnal cultural noise due mostly to tourist tours to Mt. Vesuvius. Herein, we investigate whether the different seismic frequency between day and night times could be an artifact of the peculiar cultural noise that affects this station mostly from 9:00 am to 5:00 pm from spring to fall. This time-distributed cultural noise should evidently reduce the possibility to detect low magnitude earthquakes during those hours but not high magnitude events. Using hourly distributions referring to different magnitude thresholds from M = 0.2 to M = 2.0, the Gutenberg-Richter magnitude-frequency diagram applied to the day and night-time sub-catalogs and Montecarlo statistical modeling, we demonstrate that the day-night asymmetry persists despite an evident disruption induced by cultural noise during day-hours. In particular, for the period 1999-2017, and for earthquakes with M ≥ 2 we found a Gutenberg-Richter exponent b = 1.66 ± 0.07 for the night-time events and b = 2.06 ± 0.07 for day-time events. Moreover, we repeat the analysis also for an older BKE catalog covering the period from 1992 to 2000 when cultural noise was not present. The analysis confirms a higher seismic nocturnal activity that is also characterized by a smaller Gutenberg-Richter exponent b for M ≥ 2 earthquakes relative to the day-time activity. Thus, the found night-day seismic asymmetric behavior is likely due to a real physical feature affecting Mt. Vesuvius.

Near-Real-Time Sismo-acoustic Submarine Station for offshore monitoring

NASA Astrophysics Data System (ADS)

D'Anna, Giuseppe; D'Alessandro, Antonino; Fertitta, Gioacchino; Fraticelli, Nicola; Calore, Daniele

2016-04-01

From the early 1980's, Italian seismicity is monitored by the National Seismic Network (NSN). The network has been considerably enhanced by INGV since 2005 by 24-bit digital stations equipped with broad-band sensors. The NSN is nowadays constituted by about 300 on-land seismic station able to detect and locate also small magnitude earthquake in the whole Italian peninsula. However, the lack of offshore seismic stations does not allow the accurate estimation of hypocentral and focal parameters of small magnitude earthquakes occurring in offshore areas. As in the Mediterranean area there is an intense offshore seismic activity, an extension of the seismic monitoring to the sea would be beneficial. There are two types of stations that could be used to extend the network towards the sea: the first type is connected to the coast though a cable, the second type is isolated (or stand alone) and works autonomously. Both solutions have serious limitations: the first one, for several technical and economic problems, linked to the indispensable transmission/alimentation cable, cannot be installed far from the coast; the second one, allows access to the recorded data, only after they are recovered from the seabed. It is clear that these technical solutions are not suitable for the real time monitoring of the offshore seismicity or for the realization of a tsunami warning system. For this reason, in early 2010, the OBSLab of Gibilmanna begins the design of a submarine station able to overcome the limitations of the two systems above. The station isbuilt under the project EMSO-MedIT. The two stations built have already been tested in dock and ready for installation. One of this station will be installed, in few time, in the southern Tyrrhenian Sea, near the epicentre of the Palermo 2002 main shock. The sea bottom station will be equipped with 2 very broadband 3C seismometers, a broad band hydrophone, a differential and an absolute pressure gauge. The station includes a submarine

The AlpArray Seismic Network: A Large-Scale European Experiment to Image the Alpine Orogen

NASA Astrophysics Data System (ADS)

Hetényi, György; Molinari, Irene; Clinton, John; Bokelmann, Götz; Bondár, István; Crawford, Wayne C.; Dessa, Jean-Xavier; Doubre, Cécile; Friederich, Wolfgang; Fuchs, Florian; Giardini, Domenico; Gráczer, Zoltán; Handy, Mark R.; Herak, Marijan; Jia, Yan; Kissling, Edi; Kopp, Heidrun; Korn, Michael; Margheriti, Lucia; Meier, Thomas; Mucciarelli, Marco; Paul, Anne; Pesaresi, Damiano; Piromallo, Claudia; Plenefisch, Thomas; Plomerová, Jaroslava; Ritter, Joachim; Rümpker, Georg; Šipka, Vesna; Spallarossa, Daniele; Thomas, Christine; Tilmann, Frederik; Wassermann, Joachim; Weber, Michael; Wéber, Zoltán; Wesztergom, Viktor; Živčić, Mladen

2018-04-01

The AlpArray programme is a multinational, European consortium to advance our understanding of orogenesis and its relationship to mantle dynamics, plate reorganizations, surface processes and seismic hazard in the Alps-Apennines-Carpathians-Dinarides orogenic system. The AlpArray Seismic Network has been deployed with contributions from 36 institutions from 11 countries to map physical properties of the lithosphere and asthenosphere in 3D and thus to obtain new, high-resolution geophysical images of structures from the surface down to the base of the mantle transition zone. With over 600 broadband stations operated for 2 years, this seismic experiment is one of the largest simultaneously operated seismological networks in the academic domain, employing hexagonal coverage with station spacing at less than 52 km. This dense and regularly spaced experiment is made possible by the coordinated coeval deployment of temporary stations from numerous national pools, including ocean-bottom seismometers, which were funded by different national agencies. They combine with permanent networks, which also required the cooperation of many different operators. Together these stations ultimately fill coverage gaps. Following a short overview of previous large-scale seismological experiments in the Alpine region, we here present the goals, construction, deployment, characteristics and data management of the AlpArray Seismic Network, which will provide data that is expected to be unprecedented in quality to image the complex Alpine mountains at depth.

Seismic hazard in the South Carolina coastal plain: 2002 update of the USGS national seismic hazard maps

USGS Publications Warehouse

Cramer, C.H.; Mays, T.W.; ,

2005-01-01

The damaging 1886 moment magnitude ???7 Charleston, South Carolina earthquake is indicative of the moderately likely earthquake activity along this portion of the Atlantic Coast. A recurrence of such an earthquake today would have serious consequences for the nation. The national seismic hazard maps produced by the U.S. Geological Survey (USGS) provide a picture of the levels of seismic hazard across the nation based on the best and most current scientific information. The USGS national maps were updated in 2002 and will become part of the International Codes in 2006. In the past decade, improvements have occurred in the scientific understanding of the nature and character of earthquake activity and expected ground motions in the central and eastern U.S. The paper summarizes the new knowledge of expected earthquake locations, magnitudes, recurrence, and ground-motion decay with distance. New estimates of peak ground acceleration and 0.2 s and 1.0 s spectral acceleration are compared with those displayed in the 1996 national maps. The 2002 maps show increased seismic hazard in much of the coastal plain of South Carolina, but a decrease in long period (1 s and greater) hazard by up to 20% at distances of over 50 km from the Charleston earthquake zone. Although the national maps do not account for the effects of local or regional sediments, deep coastal-plain sediments can significally alter expected ground shaking, particularly at long period motions where it can be 100% higher than the national maps.

The Central and Eastern U.S. Seismic Network: Legacy of USArray

NASA Astrophysics Data System (ADS)

Eakins, J. A.; Astiz, L.; Benz, H.; Busby, R. W.; Hafner, K.; Reyes, J. C.; Sharer, G.; Vernon, F.; Woodward, R.

2014-12-01

As the USArray Transportable Array entered the central and eastern United States, several Federal agencies (National Science Foundation, U.S. Geological Survey, U.S. Nuclear Regulatory Commission, and Department of Energy) recognized the unique opportunity to retain TA stations beyond the original timeline. The mission of the CEUSN is to produce data that enables researchers and Federal agencies alike to better understand the basic geologic questions, background earthquake rates and distribution, seismic hazard potential, and associated societal risks of this region. The selected long-term sub-array from Transportable Array (TA) stations includes nearly 200 sites, complemented by 100 broadband stations from the existing regional seismic networks to form the Central and Eastern United States Network (CEUSN). Multiple criteria for site selection were weighed by an inter-agency TA Station Selection (TASS) Working Group: seismic noise characteristics, data availability in real time, proximity to nuclear power plants, and homogeneous distribution throughout the region. The Array Network Facility (ANF) started collecting data for CEUSN network stations since late 2013, with all stations collected since May 2014. Regional seismic data streams are collected in real-time from the IRIS Data Management Center (DMC). TA stations selected to be part of CEUSN, retain the broadband sensor to which a 100 sps channel is added, the infrasound and environmental channels, and, at some stations, accelerometers are deployed. The upgraded sites become part of the N4 network for which ANF provides metadata and can issue remote commands to the station equipment. Stations still operated by TA, but planned for CEUSN, are included in the virtual network so all stations are currently available now. By the end of 2015, the remaining TA stations will be upgraded. Data quality control procedures developed for TA stations at ANF and at the DMC are currently performed on N4 data. However

New strong motion network in Georgia: basis for specifying seismic hazard

NASA Astrophysics Data System (ADS)

Kvavadze, N.; Tsereteli, N. S.

2017-12-01

Risk created by hazardous natural events is closely related to sustainable development of the society. Global observations have confirmed tendency of growing losses resulting from natural disasters, one of the most dangerous and destructive if which are earthquakes. Georgia is located in seismically active region. So, it is imperative to evaluate probabilistic seismic hazard and seismic risk with proper accuracy. National network of Georgia includes 35 station all of which are seismometers. There are significant gaps in strong motion recordings, which essential for seismic hazard assessment. To gather more accelerometer recordings, we have built a strong motion network distributed on the territory of Georgia. The network includes 6 stations for now, with Basalt 4x datalogger and strong motion sensor Episensor ES-T. For each site, Vs30 and soil resonance frequencies have been measured. Since all but one station (Tabakhmelam near Tbilisi), are located far from power and internet lines special system was created for instrument operation. Solar power is used to supply the system with electricity and GSM/LTE modems for internet access. VPN tunnel was set up using Raspberry pi, for two-way communication with stations. Tabakhmela station is located on grounds of Ionosphere Observatory, TSU and is used as a hub for the network. This location also includes a broadband seismometer and VLF electromagnetic waves observation antenna, for possible earthquake precursor studies. On server, located in Tabakhmela, the continues data is collected from all the stations, for later use. The recordings later will be used in different seismological and engineering problems, namely selecting and creating GMPE model for Caucasus, for probabilistic seismic hazard and seismic risk evaluation. These stations are a start and in the future expansion of strong motion network is planned. Along with this, electromagnetic wave observations will continue and additional antennas will be implemented

Leveraging EarthScope USArray with the Central and Eastern United States Seismic Network

NASA Astrophysics Data System (ADS)

Busby, R.; Sumy, D. F.; Woodward, R.; Frassetto, A.; Brudzinski, M.

2015-12-01

Recent earthquakes, such as the 2011 M5.8 Mineral, Virginia earthquake, raised awareness of the comparative lack of knowledge about seismicity, site response to ground shaking, and the basic geologic underpinnings in this densely populated region. With this in mind, the National Science Foundation, United States Geological Survey, United States Nuclear Regulatory Commission, and Department of Energy supported the creation of the Central and Eastern United States Seismic Network (CEUSN). These agencies, along with the IRIS Consortium who operates the network, recognized the unique opportunity to retain EarthScope Transportable Array (TA) seismic stations in this region beyond the standard deployment duration of two years per site. The CEUSN project supports 159 broadband TA stations, more than 30 with strong motion sensors added, that are scheduled to operate through 2017. Stations were prioritized in regions of elevated seismic hazard that have not been traditionally heavily monitored, such as the Charlevoix and Central Virginia Seismic Zones, and in regions proximal to nuclear power plants and other critical facilities. The stations (network code N4) transmit data in real time, with broadband and strong motion sensors sampling at 100 samples per second. More broadly the CEUSN concept also recognizes the existing backbone coverage of permanently operating seismometers in the CEUS, and forms a network of over 300 broadband stations. This multi-agency collaboration is motivated by the opportunity to use one facility to address multiple missions and needs in a way that is rarely possible, and to produce data that enables both researchers and federal agencies to better understand seismic hazard potential and associated seismic risks. In June 2015, the CEUSN Working Group (www.usarray.org/ceusn_working_group) was formed to review and provide advice to IRIS Management on the performance of the CEUSN as it relates to the target scientific goals and objectives. Map shows

Passive seismic experiment - A summary of current status. [Apollo-initiated lunar surface station data

NASA Technical Reports Server (NTRS)

Latham, G. V.; Dorman, H. J.; Horvath, P.; Ibrahim, A. K.; Koyama, J.; Nakamura, Y.

1978-01-01

The data set obtained from the four-station Apollo seismic network including signals from approximately 11,800 events, is surveyed. Some refinement of the lunar model will result, but its gross features remain the same. Attention is given to the question of a small, molten lunar core, the answer to which remains dependent on analysis of signals from a far side impact. Seventy three sources of repeating, deep moonquakes have been identified, thirty nine of which have been accurately located. Concentrated at depths from 800 to 1000 km, the periodicities of these events have led to the hypothesis that they are generated by tidal stresses. Lunar seismic data has also indicated that the meteoroid population is ten times lower than originally determined from earth based observations. Lunar seismic activity is much lower and mountainous masses show no sign of sinking, in contrast to earth, as a result of the lunar crust being four times thicker. While much work remains to be done, significant correlation between terrestrial and lunar observations can be seen.

Observations and modeling of seismic background noise

USGS Publications Warehouse

Peterson, Jon R.

1993-01-01

The preparation of this report had two purposes. One was to present a catalog of seismic background noise spectra obtained from a worldwide network of seismograph stations. The other purpose was to refine and document models of seismic background noise that have been in use for several years. The second objective was, in fact, the principal reason that this study was initiated and influenced the procedures used in collecting and processing the data.With a single exception, all of the data used in this study were extracted from the digital data archive at the U.S. Geological Survey's Albuquerque Seismological Laboratory (ASL). This archive dates from 1972 when ASL first began deploying digital seismograph systems and collecting and distributing digital data under the sponsorship of the Defense Advanced Research Projects Agency (DARPA). There have been many changes and additions to the global seismograph networks during the past twenty years, but perhaps none as significant as the current deployment of very broadband seismographs by the U.S. Geological Survey (USGS) and the University of California San Diego (UCSD) under the scientific direction of the IRIS consortium. The new data acquisition systems have extended the bandwidth and resolution of seismic recording, and they utilize high-density recording media that permit the continuous recording of broadband data. The data improvements and continuous recording greatly benefit and simplify surveys of seismic background noise.Although there are many other sources of digital data, the ASL archive data were used almost exclusively because of accessibility and because the data systems and their calibration are well documented for the most part. Fortunately, the ASL archive contains high-quality data from other stations in addition to those deployed by the USGS. Included are data from UCSD IRIS/IDA stations, the Regional Seismic Test Network (RSTN) deployed by Sandia National Laboratories (SNL), and the TERRAscope network

Receiver function structure beneath a broad-band seismic station in south Sumatra

NASA Astrophysics Data System (ADS)

MacPherson, K. A.; Hidayat, D.; Goh, S.

2010-12-01

We estimated the one-dimensional velocity structure beneath a broad-band station in south Sumatra by the forward modeling and inversion of receiver functions. Station PMBI belongs to the GEOFON seismic network maintained by GFZ-Potsdam, and at a longitude of 104.77° and latitude of -2.93°, sits atop the south Sumatran basin. This station is of interest to researchers at the Earth Observatory of Singapore, as data from it and other stations in Sumatra and Singapore will be incorporated into a regional velocity model for use in seismic hazard analyses. Three-component records from 193 events at teleseismic distances and Mw ≥ 5.0 were examined for this study and 67 records were deemed to have sufficient signal to noise characteristics to be retained for analysis. Observations are primarily from source zones in the Bougainville trench with back-azimuths to the east-south-east, the Japan and Kurile trenches with back-azimuths to the northeast, and a scattering of observations from other azimuths. Due to the level of noise present in even the higher-quality records, the usual frequency-domain deconvolution method of computing receiver functions was ineffective, and a time-domain iterative deconvolution was employed to obtain usable wave forms. Receiver functions with similar back-azimuths were stacked in order to improve their signal to noise ratios. The resulting wave forms are relatively complex, with significant energy being present in the tangential components, indicating heterogeneity in the underlying structure. A dip analysis was undertaken but no clear pattern was observed. However, it is apparent that polarities of the tangential components were generally reversed for records that sample the Sunda trench. Forward modeling of the receiver functions indicates the presence of a near-surface low-velocity layer (Vp≈1.9 km/s) and a Moho depth of ~31 km. Details of the crustal structure were investigated by employing time-domain inversions of the receiver

Preliminary Results from the North Anatolian Fault Passive Seismic Experiment: Seismicity and Anisotropy

NASA Astrophysics Data System (ADS)

Biryol, C. B.; Ozacar, A.; Beck, S. L.; Zandt, G.

2006-12-01

The North Anatolian Fault (NAF) is one of the world's largest continental strike-slip faults. Despite much geological work at the surface, the deep structure of the NAF is relatively unknown. The North Anatolian Fault Passive Seismic Experiment is mainly focused on the lithospheric structure of this newly coalescing continental transform plate boundary. In the summer of 2005, we deployed 5 broadband seismic stations near the fault to gain more insight on the background seismicity, and in June 2006 we deployed 34 additional broadband stations along multiple transects crossing the main strand of the NAF and its splays. In the region, local seismicity is not limited to a narrow band near the NAF but distributed widely suggesting widespread continental deformation especially in the southern block. We relocated two of the largest events (M>4) that occurred close to our stations. Both events are 40-50km south of the NAF in the upper crust (6-9 km) along a normal fault with a strike-slip component that previously ruptured during the June 6, 2000 Orta-Cankiri earthquake (M=6.0). Preliminary analysis of SKS splitting for 4 stations deployed in 2005 indicates seismic anisotropy with delay times exceeding 1 sec. The fast polarization directions for these stations are primarily in NE-SW orientation, which remains uniform across the NAF. This direction is at a high angle to the surface trace of the fault and crustal velocity field, suggesting decoupling of lithosphere and mantle flow. Our SKS splitting observations are also similar to that observed from GSN station ANTO in central Turkey and stations across the Anatolian Plateau in eastern Turkey indicating relatively uniform mantle anisotropy throughout the region.

ANZA Seismic Network- From Monitoring to Science

NASA Astrophysics Data System (ADS)

Vernon, F.; Eakin, J.; Martynov, V.; Newman, R.; Offield, G.; Hindley, A.; Astiz, L.

2007-05-01

The ANZA Seismic Network (http:eqinfo.ucsd.edu) utilizes broadband and strong motion sensors with 24-bit dataloggers combined with real-time telemetry to monitor local and regional seismicity in southernmost California. The ANZA network provides real-time data to the IRIS DMC, California Integrated Seismic Network (CISN), other regional networks, and the Advanced National Seismic System (ANSS), in addition to providing near real-time information and monitoring to the greater San Diego community. Twelve high dynamic range broadband and strong motion sensors adjacent to the San Jacinto Fault zone contribute data for earthquake source studies and continue the monitoring of the seismic activity of the San Jacinto fault initiated 24 years ago. Five additional stations are located in the San Diego region with one more station on San Clemente Island. The ANZA network uses the advance wireless networking capabilities of the NSF High Performance Wireless Research and Education Network (http:hpwren.ucsd.edu) to provide the communication infrastructure for the real-time telemetry of Anza seismic stations. The ANZA network uses the Antelope data acquisition software. The combination of high quality hardware, communications, and software allow for an annual network uptime in excess of 99.5% with a median annual station real-time data return rate of 99.3%. Approximately 90,000 events, dominantly local sources but including regional and teleseismic events, comprise the ANZA network waveform database. All waveform data and event data are managed using the Datascope relational database. The ANZA network data has been used in a variety of scientific research including detailed structure of the San Jacinto Fault Zone, earthquake source physics, spatial and temporal studies of aftershocks, array studies of teleseismic body waves, and array studies on the source of microseisms. To augment the location, detection, and high frequency observations of the seismic source spectrum from local

Antarctic ice sheet thickness estimation using the horizontal-to-vertical spectral ratio method with single-station seismic ambient noise

NASA Astrophysics Data System (ADS)

Yan, Peng; Li, Zhiwei; Li, Fei; Yang, Yuande; Hao, Weifeng; Bao, Feng

2018-03-01

We report on a successful application of the horizontal-to-vertical spectral ratio (H / V) method, generally used to investigate the subsurface velocity structures of the shallow crust, to estimate the Antarctic ice sheet thickness for the first time. Using three-component, five-day long, seismic ambient noise records gathered from more than 60 temporary seismic stations located on the Antarctic ice sheet, the ice thickness measured at each station has comparable accuracy to the Bedmap2 database. Preliminary analysis revealed that 60 out of 65 seismic stations on the ice sheet obtained clear peak frequencies (f0) related to the ice sheet thickness in the H / V spectrum. Thus, assuming that the isotropic ice layer lies atop a high velocity half-space bedrock, the ice sheet thickness can be calculated by a simple approximation formula. About half of the calculated ice sheet thicknesses were consistent with the Bedmap2 ice thickness values. To further improve the reliability of ice thickness measurements, two-type models were built to fit the observed H / V spectrum through non-linear inversion. The two-type models represent the isotropic structures of single- and two-layer ice sheets, and the latter depicts the non-uniform, layered characteristics of the ice sheet widely distributed in Antarctica. The inversion results suggest that the ice thicknesses derived from the two-layer ice models were in good concurrence with the Bedmap2 ice thickness database, and that ice thickness differences between the two were within 300 m at almost all stations. Our results support previous finding that the Antarctic ice sheet is stratified. Extensive data processing indicates that the time length of seismic ambient noise records can be shortened to two hours for reliable ice sheet thickness estimation using the H / V method. This study extends the application fields of the H / V method and provides an effective and independent way to measure ice sheet thickness in Antarctica.

Seismic Noise Characterization in the Northern Mississippi Embayment

NASA Astrophysics Data System (ADS)

Wiley, S.; Deshon, H. R.; Boyd, O. S.

2009-12-01

We present a study of seismic noise sources present within the northern Mississippi embayment near the New Madrid Seismic Zone (NMSZ). The northern embayment contains up to 1 km of unconsolidated coastal plain sediments overlying bedrock, making it an inherently noisy environment for seismic stations. The area is known to display high levels of cultural noise caused by agricultural activity, passing cars, trains, etc. We characterize continuous broadband seismic noise data recorded for the months of March through June 2009 at six stations operated by the Cooperative New Madrid Seismic Network. We looked at a single horizontal component of data during nighttime hours, defined as 6:15PM to 5:45AM Central Standard Time, which we determined to be the lowest amplitude period of noise for the region. Hourly median amplitudes were compared to daily average wind speeds downloaded from the National Oceanic and Atmospheric Administration. We find a correlation between time periods of increased noise and days with high wind speeds, suggesting that wind is likely a prevalent source of seismic noise in the area. The effects of wind on seismic recordings may result from wind induced tree root movement which causes ground motion to be recorded at the vaults located ~3m below ground. Automated studies utilizing the local network or the EarthScope Transportable Array, scheduled to arrive in the area in 2010-11, should expect to encounter wind induced noise fluctuations and must account for this in their analysis.

Detection capability of the IMS seismic network based on ambient seismic noise measurements

NASA Astrophysics Data System (ADS)

Gaebler, Peter J.; Ceranna, Lars

2016-04-01

All nuclear explosions - on the Earth's surface, underground, underwater or in the atmosphere - are banned by the Comprehensive Nuclear-Test-Ban Treaty (CTBT). As part of this treaty, a verification regime was put into place to detect, locate and characterize nuclear explosion testings at any time, by anyone and everywhere on the Earth. The International Monitoring System (IMS) plays a key role in the verification regime of the CTBT. Out of the different monitoring techniques used in the IMS, the seismic waveform approach is the most effective technology for monitoring nuclear underground testing and to identify and characterize potential nuclear events. This study introduces a method of seismic threshold monitoring to assess an upper magnitude limit of a potential seismic event in a certain given geographical region. The method is based on ambient seismic background noise measurements at the individual IMS seismic stations as well as on global distance correction terms for body wave magnitudes, which are calculated using the seismic reflectivity method. From our investigations we conclude that a global detection threshold of around mb 4.0 can be achieved using only stations from the primary seismic network, a clear latitudinal dependence for the detection threshold can be observed between northern and southern hemisphere. Including the seismic stations being part of the auxiliary seismic IMS network results in a slight improvement of global detection capability. However, including wave arrivals from distances greater than 120 degrees, mainly PKP-wave arrivals, leads to a significant improvement in average global detection capability. In special this leads to an improvement of the detection threshold on the southern hemisphere. We further investigate the dependence of the detection capability on spatial (latitude and longitude) and temporal (time) parameters, as well as on parameters such as source type and percentage of operational IMS stations.

MSNoise: a Python Package for Monitoring Seismic Velocity Changes using Ambient Seismic Noise

NASA Astrophysics Data System (ADS)

Lecocq, T.; Caudron, C.; Brenguier, F.

2013-12-01

Earthquakes occur every day all around the world and are recorded by thousands of seismic stations. In between earthquakes, stations are recording "noise". In the last 10 years, the understanding of this noise and its potential usage have been increasing rapidly. The method, called "seismic interferometry", uses the principle that seismic waves travel between two recorders and are multiple-scattered in the medium. By cross-correlating the two records, one gets an information on the medium below/between the stations. The cross-correlation function (CCF) is a proxy to the Green Function of the medium. Recent developments of the technique have shown those CCF can be used to image the earth at depth (3D seismic tomography) or study the medium changes with time. We present MSNoise, a complete software suite to compute relative seismic velocity changes under a seismic network, using ambient seismic noise. The whole is written in Python, from the monitoring of data archives, to the production of high quality figures. All steps have been optimized to only compute the necessary steps and to use 'job'-based processing. We present a validation of the software on a dataset acquired during the UnderVolc[1] project on the Piton de la Fournaise Volcano, La Réunion Island, France, for which precursory relative changes of seismic velocity are visible for three eruptions betwee 2009 and 2011.

Temporal variations in Global Seismic Stations ambient noise power levels

USGS Publications Warehouse

Ringler, A.T.; Gee, L.S.; Hutt, C.R.; McNamara, D.E.

2010-01-01

Recent concerns about time-dependent response changes in broadband seismometers have motivated the need for methods to monitor sensor health at Global Seismographic Network (GSN) stations. We present two new methods for monitoring temporal changes in data quality and instrument response transfer functions that are independent of Earth seismic velocity and attenuation models by comparing power levels against different baseline values. Our methods can resolve changes in both horizontal and vertical components in a broad range of periods (∼0.05 to 1,000 seconds) in near real time. In this report, we compare our methods with existing techniques and demonstrate how to resolve instrument response changes in long-period data (>100 seconds) as well as in the microseism bands (5 to 20 seconds).

The GEOSCOPE broadband seismic observatory

NASA Astrophysics Data System (ADS)

Douet, Vincent; Vallée, Martin; Zigone, Dimitri; Bonaimé, Sébastien; Stutzmann, Eléonore; Maggi, Alessia; Pardo, Constanza; Bernard, Armelle; Leroy, Nicolas; Pesqueira, Frédéric; Lévêque, Jean-Jacques; Thoré, Jean-Yves; Bes de Berc, Maxime; Sayadi, Jihane

2016-04-01

The GEOSCOPE observatory has provided continuous broadband data to the scientific community for the past 34 years. The 31 operational GEOSCOPE stations are installed in 17 countries, across all continents and on islands throughout the oceans. They are equipped with three component very broadband seismometers (STS1, T240 or STS2) and 24 or 26 bit digitizers (Q330HR). Seismometers are installed with warpless base plates, which decrease long period noise on horizontal components by up to 15dB. All stations send data in real time to the IPGP data center, which transmits them automatically to other data centers (FDSN/IRIS-DMC and RESIF) and tsunami warning centers. In 2016, three stations are expected to be installed or re-installed: in Western China (WUS station), in Saint Pierre and Miquelon Island (off the East coast of Canada) and in Walis and Futuna (SouthWest Pacific Ocean). The waveform data are technically validated by IPGP (25 stations) or EOST (6 stations) in order to check their continuity and integrity. Scientific data validation is also performed by analyzing seismic noise level of the continuous data and by comparing real and synthetic earthquake waveforms (body waves). After these validations, data are archived by the IPGP data center in Paris. They are made available to the international scientific community through different interfaces (see details on http://geoscope.ipgp.fr). Data are duplicated at the FDSN/IRIS-DMC data center and a similar duplication at the French national data center RESIF will be operational in 2016. The GEOSCOPE broadband seismic observatory also provides near-real time information on global moderate-to-large seismicity (above magnitude 5.5-6) through the automated application of the SCARDEC method (Vallée et al., 2011). By using global data from the FDSN - in particular from GEOSCOPE and IRIS/USGS stations -, earthquake source parameters (depth, moment magnitude, focal mechanism, source time function) are determined about 45

Seismic instrumentation plan for the Hawaiian Volcano Observatory

USGS Publications Warehouse

Thelen, Weston A.

2014-01-01

The installation of new seismic stations is only the first part of building a volcanic early warning capability for seismicity in the State of Hawaii. Additional personnel will likely be required to study the volcanic processes at work under each volcano, analyze the current seismic activity at a level sufficient for early warning, build new tools for monitoring, maintain seismic computing resources, and maintain the new seismic stations.

Seismic imaging of the oil and geothermal reservoirs using the induced seismicity

NASA Astrophysics Data System (ADS)

Zhang, H.; Toksoz, M. N.; Fehler, M.

2011-12-01

It is known that microseismicity can be induced in the oil field due to the stress change caused by oil/gas production. Similarly, injection of high-pressure fluids into the reservoir can also induce microseismicity. Due to the proximity of induced seismicity to the reservoir, in some cases, it may be advantageous to use induced seismicity to image the reservoir. The seismic stations for monitoring the induced seismicity are usually sparse. Conventional travel time tomography using travel times from seismic events to stations may not be applicable because of poor ray coverage outside the source region. In comparison, the double-difference tomography method of Zhang and Thurber (2003) that uses the differential travel times is able to image the reservoir by avoiding determining the velocity structure outside the source region. In this study, we present two case studies of applying double-difference tomography to induced seismicity monitored by borehole stations. In the case of an oil field in Oman, five closely spaced monitoring wells are used to monitor microseismicity induced by gas production. In each well, multiple seismic sensors are positioned from depths 750 m - 1250 m and about 2000 events are selected for tomography. Reservoir imaging shows encouraging results in identifying structures and velocity changes within reservoir layers. Clear velocity contrast was seen across the major northeast-southwest faults. Low Vp, low Vs and low Vp/Vs anomalies are mainly associated with the gas production layer. For the case of the Soultz Enhanced Geothermal System at Soultz-sous-Forets, France, we used travel time data from the September and October 1993 hydraulic stimulations, where only four borehole stations are available. The results showed that the S-wave velocity structure correlated well with seismicity and showed low velocity zones at depths between 2900 and 3300 meters, where fluid was believed to have infiltrated the reservoir. We also attempt time

Pre-instrumental seismicity in Central Africa using felt seisms recorded mainly at the meteorological stations of DRC, Rwanda and Burundi during the colonial period

NASA Astrophysics Data System (ADS)

Mulumba, J.-L.; Delvaux, D.

2012-04-01

Seismic hazard assessment and mitigation of catastrophes are primarily based on the identification and characterization of seismically active zones. These tasks still rely heavily on the existing knowledge of the seismic activity over the longest possible time period. The first seismic network in Equatorial Africa (IRSAC network) was operated from the Lwiro scientific base on the western shores of Lake Kivu between 1953 and 1963. Before this installation, the historical record of seismic activity in Central Africa is sparse. Even for the relatively short period concerned, spanning only 50-60 years, the historical record is far from being complete. A first attempt has been made by Herrinckx (1959) who compiled a list 960 felt seisms recorded at the meteorological stations between 1915 and 1954 in Congo, Rwanda and Burundi. They were used to draw a density map of felt seisms per square degree. We completed this data base by exploiting the meteorological archives and any available historical report to enlarge the database which now reaches 1513 entries between 1900 and 1959. These entries have been exanimate in order to identify possible historical seismic events. Those are defined by 3 or more quasi-simultaneous records observed over a relatively short distance (a few degrees of latitude/longitude) within a short time difference (few hours). A preliminary list of 115 possible historical seisms has been obtained, identified by 3 to 15 different stations. The proposed location is taken as the average latitude and longitude of the stations where the felt seisms were recorded. Some of the most important ones are associated to aftershocks that have been felt at some stations after the main shocks. The most recent felt seisms have been also recorded instrumentally, which helps to validate the procedure followed. The main difficulties are the magnitude estimation and the possible spatial incompleteness of the recording of felt seism evidence at the margin of the observation

Bulgarian National Digital Seismological Network

NASA Astrophysics Data System (ADS)

Dimitrova, L.; Solakov, D.; Nikolova, S.; Stoyanov, S.; Simeonova, S.; Zimakov, L. G.; Khaikin, L.

2011-12-01

The Bulgarian National Digital Seismological Network (BNDSN) consists of a National Data Center (NDC), 13 stations equipped with RefTek High Resolution Broadband Seismic Recorders - model DAS 130-01/3, 1 station equipped with Quanterra 680 and broadband sensors and accelerometers. Real-time data transfer from seismic stations to NDC is realized via Virtual Private Network of the Bulgarian Telecommunication Company. The communication interruptions don't cause any data loss at the NDC. The data are backed up in the field station recorder's 4Mb RAM memory and are retransmitted to the NDC immediately after the communication link is re-established. The recorders are equipped with 2 compact flash disks able to save more than 1 month long data. The data from the flash disks can be downloaded remotely using FTP. The data acquisition and processing hardware redundancy at the NDC is achieved by two clustered SUN servers and two Blade Workstations. To secure the acquisition, processing and data storage processes a three layer local network is designed at the NDC. Real-time data acquisition is performed using REFTEK's full duplex error-correction protocol RTPD. Data from the Quanterra recorder and foreign stations are fed into RTPD in real-time via SeisComP/SeedLink protocol. Using SeisComP/SeedLink software the NDC transfers real-time data to INGV-Roma, NEIC-USA, ORFEUS Data Center. Regional real-time data exchange with Romania, Macedonia, Serbia and Greece is established at the NDC also. Data processing is performed by the Seismic Network Data Processor (SNDP) software package running on the both Servers. SNDP includes subsystems: Real-time subsystem (RTS_SNDP) - for signal detection; evaluation of the signal parameters; phase identification and association; source estimation; Seismic analysis subsystem (SAS_SNDP) - for interactive data processing; Early warning subsystem (EWS_SNDP) - based on the first arrived P-phases. The signal detection process is performed by

A deployment of broadband seismic stations in two deep gold mines, South Africa

USGS Publications Warehouse

McGarr, Arthur F.; Boettcher, Margaret S.; Fletcher, Jon Peter B.; Johnston, Malcolm J.; Durrheim, R.; Spottiswoode, S.; Milev, A.

2009-01-01

In-mine seismic networks throughout the TauTona and Mponeng gold mines provide precise locations and seismic source parameters of earthquakes. They also support small-scale experimental projects, including NELSAM (Natural Earthquake Laboratory in South African Mines), which is intended to record, at close hand, seismic rupture of a geologic fault that traverses the project region near the deepest part of TauTona. To resolve some questions regarding the in-mine and NELSAM networks, we deployed four portable broadband seismic stations at deep sites within TauTona and Mponeng for one week during September 2007 and recorded ground acceleration. Moderately large earthquakes within our temporary network were recorded with sufficiently high signal-to-noise that we were able to integrate the acceleration to ground velocity and displacement, from which moment tensors could be determined. We resolved the questions concerning the NELSAM and in-mine networks by using these moment tensors to calculate synthetic seismograms at various network recording sites for comparison with the ground motion recorded at the same locations. We also used the peak velocity of the S wave pulse, corrected for attenuation with distance, to estimate the maximum slip within the rupture zone of an earthquake. We then combined the maximum slip and seismic moment with results from laboratory friction experiments to estimate maximum slip rates within the same high-slip patches of the rupture zone. For the four largest earthquakes recorded within our network, all with magnitudes near 2, these inferred maximum slips range from 4 to 27 mm and the corresponding maximum slip rates range from 1 to 6 m/s. These results, in conjunction with information from previous ground motion studies, indicate that underground support should be capable of withstanding peak ground velocities of at least 5 m/s.

Extraction of Pn seismic signals from air-gun shots recorded by the Cascadia Amphibious seismic experiment

NASA Astrophysics Data System (ADS)

Rathnayaka, S.; Gao, H.

2017-12-01

The goal of this study is to extract Pn (head wave) seismic waveforms recorded by both offshore and onshore (broadband and short period) seismic stations and evaluate the data quality. Two offshore active-source seismic experiments, MGL 1211 and MGL 1212, were conducted from 13th June to 24th July 2012, during the first year deployment of the Cascadia Initiative Amphibious Array. In total, we choose 110 ocean bottom seismometers and 209 inland stations that are located along the entire Cascadia subduction zone. We first remove the instrument response, and then explore the potential frequency ranges and the diurnal effect. We make the common receiver gathering for each seismic station and filter the seismic waveforms at multiple frequency bands, ranging from 3-5 Hz, 5-10 Hz, 10-20 Hz, to 20-40 Hz, respectively. To quantitatively evaluate the data quality, we calculate the signal-to-noise ratio (SNR) of the waveforms for usable stations that record clear Pn arrivals at multiple frequency bands. Our results show that most offshore stations located at deep water (>1.5 km) record clear air-gun shot signals at frequencies higher than 3 Hz and up to 550 km away from the source. For most stations located on the shallow continental shelf, the seismic recordings appear much noisier at all the frequencies compared to stations at deep water. Three general trends are observed for the SNR distribution; First, the SNR ratio increases from lower to higher frequency bands; Second, the ratio decreases with the increasing source-to-receiver distance; And third, the ratio increases from shallow to deep water. We also observe a rough negative relationship of the signal-to-noise ratio with the thickness of the marine sediment. Only 5 inland stations record clear air-gun shot arrivals up to 200 km away from the source. More detailed data quality analysis with more results will also be present.

Seismic Search Engine: A distributed database for mining large scale seismic data

NASA Astrophysics Data System (ADS)

Liu, Y.; Vaidya, S.; Kuzma, H. A.

2009-12-01

The International Monitoring System (IMS) of the CTBTO collects terabytes worth of seismic measurements from many receiver stations situated around the earth with the goal of detecting underground nuclear testing events and distinguishing them from other benign, but more common events such as earthquakes and mine blasts. The International Data Center (IDC) processes and analyzes these measurements, as they are collected by the IMS, to summarize event detections in daily bulletins. Thereafter, the data measurements are archived into a large format database. Our proposed Seismic Search Engine (SSE) will facilitate a framework for data exploration of the seismic database as well as the development of seismic data mining algorithms. Analogous to GenBank, the annotated genetic sequence database maintained by NIH, through SSE, we intend to provide public access to seismic data and a set of processing and analysis tools, along with community-generated annotations and statistical models to help interpret the data. SSE will implement queries as user-defined functions composed from standard tools and models. Each query is compiled and executed over the database internally before reporting results back to the user. Since queries are expressed with standard tools and models, users can easily reproduce published results within this framework for peer-review and making metric comparisons. As an illustration, an example query is “what are the best receiver stations in East Asia for detecting events in the Middle East?” Evaluating this query involves listing all receiver stations in East Asia, characterizing known seismic events in that region, and constructing a profile for each receiver station to determine how effective its measurements are at predicting each event. The results of this query can be used to help prioritize how data is collected, identify defective instruments, and guide future sensor placements.

Seismic anisotropy and slab dynamics from SKS splitting recorded in Colombia

NASA Astrophysics Data System (ADS)

Porritt, Robert W.; Becker, Thorsten W.; Monsalve, Gaspar

2014-12-01

The Nazca, Caribbean, and South America plates meet in northwestern South America where the northern end of the Andean volcanic arc and Wadati-Benioff zone seismicity indicate ongoing subduction. However, the termination of Quaternary volcanism at ~5.5°N and eastward offset in seismicity underneath Colombia suggest the presence of complex slab geometry. To help link geometry to dynamics, we analyze SKS splitting for 38 broadband stations of the Colombian national network. Measurements of fast polarization axes in western Colombia close to the trench show dominantly trench-perpendicular orientations. Orientations measured at stations in the back arc, farther to the east, however, abruptly change to roughly trench parallel anisotropy. This may indicate along-arc mantle flow, possibly related to the suggested "Caldas" slab tear, or a lithospheric signature, but smaller-scale variations in anisotropy remain to be explained. Our observations are atypical globally and challenge our understanding of the complexities of subduction zone seismic anisotropy.

Geothermal Induced Seismicity National Environmental Policy Act Review

DOE Office of Scientific and Technical Information (OSTI.GOV)

Levine, Aaron L; Cook, Jeffrey J; Beckers, Koenraad J

This presentation reviews four National Environmental Policy Act of 1969 (NEPA) documents to understand how Federal agencies, including the U.S. Bureau of Land Management and Department of Energy, review and analyze the potential impacts to the human environment when funding or approving permits for enhanced geothermal system with the potential for induced seismicity.

Real-time detection and characterization of nuclear explosion using broadband analyses of regional seismic stations

NASA Astrophysics Data System (ADS)

Prastowo, T.; Madlazim

2018-01-01

This preliminary study aims to propose a new method of real-time detection and characterization of nuclear explosions by analyzing broadband seismic waveforms acquired from a network of regional seismic stations. Signal identification generated by a nuclear test was differentiated from natural sources of either earthquakes or other natural seismo-tectonic events by verifying crucial parameters, namely source depth, type of first motion, and P-wave domination of the broadband seismic wavesunder consideration. We examined and analyzed a recently hypothetical nuclear test performed by the North Koreangovernment that occurred on September 3, 2017 as a vital point to study. From spectral analyses, we found that the source of corresponding signals associated with detonations of the latest underground nuclear test was at a much shallower depth below the surface relatively compared with that of natural earthquakes, the suspected nuclear explosions produced compressional waves with radially directed outward from the source for their first motions, and the waves were only dominated by P-components. The results are then discussed in the context of potential uses of the proposed methodology for human-induced disaster early warning system and/or the need of rapid response purposes for minimizing the disaster risks.

Alaska Volcano Observatory Seismic Network Data Availability

NASA Astrophysics Data System (ADS)

Dixon, J. P.; Haney, M. M.; McNutt, S. R.; Power, J. A.; Prejean, S. G.; Searcy, C. K.; Stihler, S. D.; West, M. E.

2009-12-01

The Alaska Volcano Observatory (AVO) established in 1988 as a cooperative program of the U.S. Geological Survey, the Geophysical Institute at the University of Alaska Fairbanks, and the Alaska Division of Geological and Geophysical Surveys, monitors active volcanoes in Alaska. Thirty-three volcanoes are currently monitored by a seismograph network consisting of 193 stations, of which 40 are three-component stations. The current state of AVO’s seismic network, and data processing and availability are summarized in the annual AVO seismological bulletin, Catalog of Earthquake Hypocenters at Alaska Volcanoes, published as a USGS Data Series (most recent at http://pubs.usgs.gov/ds/467). Despite a rich seismic data set for 12 VEI 2 or greater eruptions, and over 80,000 located earthquakes in the last 21 years, the volcanic seismicity in the Aleutian Arc remains understudied. Initially, AVO seismic data were only provided via a data supplement as part of the annual bulletin, or upon request. Over the last few years, AVO has made seismic data more available with the objective of increasing volcano seismic research on the Aleutian Arc. The complete AVO earthquake catalog data are now available through the annual AVO bulletin and have been submitted monthly to the on-line Advanced National Seismic System (ANSS) composite catalog since 2008. Segmented waveform data for all catalog earthquakes are available upon request and efforts are underway to make this archive web accessible as well. Continuous data were first archived using a tape backup, but the availability of low cost digital storage media made a waveform backup of continuous data a reality. Currently the continuous AVO waveform data can be found in several forms. Since late 2002, AVO has burned all continuous waveform data to DVDs, as well as storing these data in Antelope databases at the Geophysical Institute. Beginning in 2005, data have been available through a Winston Wave Server housed at the USGS in

The Southern Kansas Seismic Network

NASA Astrophysics Data System (ADS)

Terra, F. M.

2015-12-01

Historically aseismic Harper and Sumner counties in Southern Kansas experienced a dramatic increase in seismicity beginning in early 2014, coincident with the development of new oil production in the Mississippi Lime Play. In order to better understand the potential relationships between seismicity and oil development, the USGS installed a real-time telemetered seismic network in cooperation with the Kansas Geological Survey, the Kansas Corporation Commission, the Kansas Department of Health and Environment, Harper County, and the Oklahoma Geological Survey. The network began operation in March 2014 with an initial deployment of 5 NetQuakes accelerometers and by July 2014 had expanded to include 10 broadband sites. The network currently has 14 stations, all with accelerometers and 12 with broadband seismometers. The network has interstation spacing of 15 - 25 km and typical azimuthal gap of 80 for well-located events. Data are continuously streamed to IRIS at 200 samples per second from most sites. Earthquake locations are augmented with additional stations from the USGS National Network, Oklahoma Geological Survey Seismic Network, Kansas Seismic Monitoring Network and the Enid Oklahoma Network. Since the spring of 2014 over 7500 earthquakes have been identified with data from this network, 1400 of which have been manually timed and cataloged. Focal depths for earthquakes typically range between 2 and 7 km. The catalog is available at earthquake.usgs.gov/earthquakes/search/ under network code 'Ismpkansas'. The network recorded the largest known earthquake in Harper County, Mw 4.3, on October 2, 2014 and in Sumner County, Mw 4.9, on November 12, 2014. Recorded ground motions at the epicenter of the October earthquake were 0.70 g (PGA) and 12 cm/s (PGV). These high ground motion values agree with near-source recordings made by other USGS temporary deployments in the U. S. midcontinent, indicating a significant shaking hazard from such shallow, moderate

Exploring Seismic Noise with the USArray Transportable Array

NASA Astrophysics Data System (ADS)

Woodward, R.; Busby, R. W.; Simpson, D. W.

2009-12-01

The large number of seismic stations that comprise the EarthScope USArray Transportable Array (TA) seismic network provide an unparalleled opportunity for studying how seismic noise evolves with time over a large portion of the North American continent. Power spectra for every station in the TA data are computed automatically, for every hour of every station-day, by the Quality Analysis Control Kit (QUACK) system at the IRIS Data Management Center. The power spectra utilize hour-long data segments, with 50% overlap between segments, providing spectral values in the band between 20 Hz and 172 s. Thus, at any in-band frequency one can construct a continuous two-year time history of seismic noise for every TA station. When the time variation of the power spectra values across the array are rendered as individual movie frames one can examine the evolution of seismic noise across the full spatio-temporal extent of the TA. Overall, the background noise levels (especially at periods below 10 s) are remarkably uniform across the entire array. Numerous expected features are present, including diurnal and annual variations, enhanced noise levels at coastal stations, transients related to large storms, and episodes when the observations of background noise are dominated by earthquake energy. Upgrades to the TA station instrumentation will provide the capability to measure additional physical factors relevant to seismic noise. All TA stations deployed after August 2009 include MEMS barometers that can measure atmospheric pressure from DC to approximately 0.1 Hz. In additional, several stations have been temporarily equipped with infrasound sensors. Previous research has highlighted the direct effect of atmospheric pressure fluctuations on very long period vertical seismometers. The relationship to noise observed on horizontal seismometers is more complex. However, with a large number of uniform installations it may be possible to make further progress. We will present analyses

Strong Motion Network of Medellín and Aburrá Valley: technical advances, seismicity records and micro-earthquake monitoring

NASA Astrophysics Data System (ADS)

Posada, G.; Trujillo, J. C., Sr.; Hoyos, C.; Monsalve, G.

2017-12-01

The tectonics setting of Colombia is determined by the interaction of Nazca, Caribbean and South American plates, together with the Panama-Choco block collision, which makes a seismically active region. Regional seismic monitoring is carried out by the National Seismological Network of Colombia and the Accelerometer National Network of Colombia. Both networks calculate locations, magnitudes, depths and accelerations, and other seismic parameters. The Medellín - Aburra Valley is located in the Northern segment of the Central Cordillera of Colombia, and according to the Colombian technical seismic norm (NSR-10), is a region of intermediate hazard, because of the proximity to seismic sources of the Valley. Seismic monitoring in the Aburra Valley began in 1996 with an accelerometer network which consisted of 38 instruments. Currently, the network consists of 26 stations and is run by the Early Warning System of Medellin and Aburra Valley (SIATA). The technical advances have allowed the real-time communication since a year ago, currently with 10 stations; post-earthquake data is processed through operationally near-real-time, obtaining quick results in terms of location, acceleration, spectrum response and Fourier analysis; this information is displayed at the SIATA web site. The strong motion database is composed by 280 earthquakes; this information is the basis for the estimation of seismic hazards and risk for the region. A basic statistical analysis of the main information was carried out, including the total recorded events per station, natural frequency, maximum accelerations, depths and magnitudes, which allowed us to identify the main seismic sources, and some seismic site parameters. With the idea of a more complete seismic monitoring and in order to identify seismic sources beneath the Valley, we are in the process of installing 10 low-cost shake seismometers for micro-earthquake monitoring. There is no historical record of earthquakes with a magnitude

78 FR 66964 - International Space Station National Laboratory Advisory Committee; Charter Renewal

Federal Register 2010, 2011, 2012, 2013, 2014

2013-11-07

... NATIONAL AERONAUTICS AND SPACE ADMINISTRATION [Notice: (13-129)] International Space Station National Laboratory Advisory Committee; Charter Renewal AGENCY: National Aeronautics and Space Administration (NASA). ACTION: Notice of renewal of the charter of the International Space Station National...

The Global Detection Capability of the IMS Seismic Network in 2013 Inferred from Ambient Seismic Noise Measurements

NASA Astrophysics Data System (ADS)

Gaebler, P. J.; Ceranna, L.

2016-12-01

All nuclear explosions - on the Earth's surface, underground, underwater or in the atmosphere - are banned by the Comprehensive Nuclear-Test-Ban Treaty (CTBT). As part of this treaty, a verification regime was put into place to detect, locate and characterize nuclear explosion testings at any time, by anyone and everywhere on the Earth. The International Monitoring System (IMS) plays a key role in the verification regime of the CTBT. Out of the different monitoring techniques used in the IMS, the seismic waveform approach is the most effective technology for monitoring nuclear underground testing and to identify and characterize potential nuclear events. This study introduces a method of seismic threshold monitoring to assess an upper magnitude limit of a potential seismic event in a certain given geographical region. The method is based on ambient seismic background noise measurements at the individual IMS seismic stations as well as on global distance correction terms for body wave magnitudes, which are calculated using the seismic reflectivity method. From our investigations we conclude that a global detection threshold of around mb 4.0 can be achieved using only stations from the primary seismic network, a clear latitudinal dependence for the detection thresholdcan be observed between northern and southern hemisphere. Including the seismic stations being part of the auxiliary seismic IMS network results in a slight improvement of global detection capability. However, including wave arrivals from distances greater than 120 degrees, mainly PKP-wave arrivals, leads to a significant improvement in average global detection capability. In special this leads to an improvement of the detection threshold on the southern hemisphere. We further investigate the dependence of the detection capability on spatial (latitude and longitude) and temporal (time) parameters, as well as on parameters such as source type and percentage of operational IMS stations.

Large Subduction Earthquake Simulations using Finite Source Modeling and the Offshore-Onshore Ambient Seismic Field

NASA Astrophysics Data System (ADS)

Viens, L.; Miyake, H.; Koketsu, K.

2016-12-01

Large subduction earthquakes have the potential to generate strong long-period ground motions. The ambient seismic field, also called seismic noise, contains information about the elastic response of the Earth between two seismic stations that can be retrieved using seismic interferometry. The DONET1 network, which is composed of 20 offshore stations, has been deployed atop the Nankai subduction zone, Japan, to continuously monitor the seismotectonic activity in this highly seismically active region. The surrounding onshore area is covered by hundreds of seismic stations, which are operated the National Research Institute for Earth Science and Disaster Prevention (NIED) and the Japan Meteorological Agency (JMA), with a spacing of 15-20 km. We retrieve offshore-onshore Green's functions from the ambient seismic field using the deconvolution technique and use them to simulate the long-period ground motions of moderate subduction earthquakes that occurred at shallow depth. We extend the point source method, which is appropriate for moderate events, to finite source modeling to simulate the long-period ground motions of large Mw 7 class earthquake scenarios. The source models are constructed using scaling relations between moderate and large earthquakes to discretize the fault plane of the large hypothetical events into subfaults. Offshore-onshore Green's functions are spatially interpolated over the fault plane to obtain one Green's function for each subfault. The interpolated Green's functions are finally summed up considering different rupture velocities. Results show that this technique can provide additional information about earthquake ground motions that can be used with the existing physics-based simulations to improve seismic hazard assessment.

Site Amplification Characteristics of the Several Seismic Stations at Jeju Island, in Korea, using S-wave Energy, Background Noise, and Coda waves from the East Japan earthquake (Mar. 11th, 2011) Series.

NASA Astrophysics Data System (ADS)

Seong-hwa, Y.; Wee, S.; Kim, J.

2016-12-01

Observed ground motions are composed of 3 main factors such as seismic source, seismic wave attenuation and site amplification. Among them, site amplification is also important factor and should be considered to estimate soil-structure dynamic interaction with more reliability. Though various estimation methods are suggested, this study used the method by Castro et. al.(1997) for estimating site amplification. This method has been extended to background noise, coda waves and S waves recently for estimating site amplification. This study applied the Castro et. al.(1997)'s method to 3 different seismic waves, that is, S-wave Energy, Background Noise, and Coda waves. This study analysed much more than about 200 ground motions (acceleration type) from the East Japan earthquake (March 11th, 2011) Series of seismic stations at Jeju Island (JJU, SGP, HALB, SSP and GOS; Fig. 1), in Korea. The results showed that most of the seismic stations gave similar results among three types of seismic energies. Each station showed its own characteristics of site amplification property in low, high and specific resonance frequency ranges. Comparison of this study to other studies can give us much information about dynamic amplification of domestic sites characteristics and site classification.

On the use of remote infrasound and seismic stations to constrain eruptive sequences

NASA Astrophysics Data System (ADS)

Caudron, C.; Taisne, B.; Garces, M. A.

2014-12-01

The Kelud eruption was one of the strongest volcanic eruption of the decade. The eruption occurred on the 13th of February 2014 and ejected volcanic ash up to 20 km of altitude. The eruption also destroyed most of the instruments deployed in the near field. Therefore, not much information could be unraveled from the local volcano monitoring system. An explosion was clearly captured at many infrasound stations of the IMS network (and in Singapore), making it one of the biggest volcanic events recorded by the network. The high intensity, deep frequency, and infrasonic detection range of >10,000 km is characteristic of an eruptive column that injects ash into aircraft cruising altitudes and is an evident threat to aviation. The explosion signal was particularly rich in very long periods (~ 200s) and could be resolved as two distinct pulses at some sites. Interestingly, many broadband seismic instruments also recorded this event as far as 5000 kilometers. By inspecting the seismic data of the instruments located closer to the edifice (~ 150 km), we could clearly distinguish two different pulses separated by 17 minutes, followed by the arrival of very low frequencies (thanks to the coupling between ground and atmosphere). One pulse vs two pulses might have strong implications for the subsequent ash modelling. Due to the violence of the events, 4 stations out of 5 were destructed and the remaining one was saturated. This illustrates that data streams from broadband seismometers and infrasound sensors located at safe distances are extremely useful for deciphering the dynamic of the eruption and its implication in term of local, regional and global impact.

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

NASA Astrophysics Data System (ADS)

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

2015-12-01

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

Small aperture seismic arrays for studying planetary interiors and seismicity

NASA Astrophysics Data System (ADS)

Schmerr, N. C.; Lekic, V.; Fouch, M. J.; Panning, M. P.; Siegler, M.; Weber, R. C.

2017-12-01

Seismic arrays are a powerful tool for understanding the interior structure and seismicity across objects in the Solar System. Given the operational constraints of ground-based lander investigations, a small aperture seismic array can provide many of the benefits of a larger-scale network, but does not necessitate a global deployment of instrumentation. Here we define a small aperture array as a deployment of multiple seismometers, with a separation between instruments of 1-1000 meters. For example, small aperture seismic arrays have been deployed on the Moon during the Apollo program, the Active Seismic Experiments of Apollo 14 and 16, and the Lunar Seismic Profiling Experiment deployed by the Apollo 17 astronauts. Both were high frequency geophone arrays with spacing of 50 meters that provided information on the layering and velocity structure of the uppermost kilometer of the lunar crust. Ideally such arrays would consist of instruments that are 3-axis short period or broadband seismometers. The instruments must have a sampling rate and frequency range sensitivity capable of distinguishing between waves arriving at each station in the array. Both terrestrial analogs and the data retrieved from the Apollo arrays demonstrate the efficacy of this approach. Future opportunities exist for deployment of seismic arrays on Europa, asteroids, and other objects throughout the Solar System. Here we will present both observational data and 3-D synthetic modeling results that reveal the sensing requirements and the primary advantages of a small aperture seismic array over single station approach. For example, at the smallest apertures of < 1 m, we constrain that sampling rates must exceed 500 Hz and instrument sensitivity must extend to 100 Hz or greater. Such advantages include the improved ability to resolve the location of the sources near the array through detection of backazimuth and differential timing between stations, determination of the small-scale structure

Seismic site-response characterization of high-velocity sites using advanced geophysical techniques: application to the NAGRA-Net

NASA Astrophysics Data System (ADS)

Poggi, V.; Burjanek, J.; Michel, C.; Fäh, D.

2017-08-01

The Swiss Seismological Service (SED) has recently finalised the installation of ten new seismological broadband stations in northern Switzerland. The project was led in cooperation with the National Cooperative for the Disposal of Radioactive Waste (Nagra) and Swissnuclear to monitor micro seismicity at potential locations of nuclear-waste repositories. To further improve the quality and usability of the seismic recordings, an extensive characterization of the sites surrounding the installation area was performed following a standardised investigation protocol. State-of-the-art geophysical techniques have been used, including advanced active and passive seismic methods. The results of all analyses converged to the definition of a set of best-representative 1-D velocity profiles for each site, which are the input for the computation of engineering soil proxies (traveltime averaged velocity and quarter-wavelength parameters) and numerical amplification models. Computed site response is then validated through comparison with empirical site amplification, which is currently available for any station connected to the Swiss seismic networks. With the goal of a high-sensitivity network, most of the NAGRA stations have been installed on stiff-soil sites of rather high seismic velocity. Seismic characterization of such sites has always been considered challenging, due to lack of relevant velocity contrast and the large wavelengths required to investigate the frequency range of engineering interest. We describe how ambient vibration techniques can successfully be applied in these particular conditions, providing practical recommendations for best practice in seismic site characterization of high-velocity sites.

The data quality analyzer: a quality control program for seismic data

USGS Publications Warehouse

Ringler, Adam; Hagerty, M.T.; Holland, James F.; Gonzales, A.; Gee, Lind S.; Edwards, J.D.; Wilson, David; Baker, Adam

2015-01-01

The quantification of data quality is based on the evaluation of various metrics (e.g., timing quality, daily noise levels relative to long-term noise models, and comparisons between broadband data and event synthetics). Users may select which metrics contribute to the assessment and those metrics are aggregated into a “grade” for each station. The DQA is being actively used for station diagnostics and evaluation based on the completed metrics (availability, gap count, timing quality, deviation from a global noise model, deviation from a station noise model, coherence between co-located sensors, and comparison between broadband data and synthetics for earthquakes) on stations in the Global Seismographic Network and Advanced National Seismic System.

50 years of Global Seismic Observations

NASA Astrophysics Data System (ADS)

Anderson, K. R.; Butler, R.; Berger, J.; Davis, P.; Derr, J.; Gee, L.; Hutt, C. R.; Leith, W. S.; Park, J. J.

2007-12-01

Seismological recordings have been made on Earth for hundreds of years in some form or another, however, global monitoring of earthquakes only began in the 1890's when John Milne created 40 seismic observatories to measure the waves from these events. Shortly after the International Geophysical Year (IGY), a concerted effort was made to establish and maintain a more modern standardized seismic network on the global scale. In the early 1960's, the World-Wide Standardized Seismograph Network (WWSSN) was established through funding from the Advanced Research Projects Agency (ARPA) and was installed and maintained by the USGS's Albuquerque Seismological Laboratory (then a part of the US Coast and Geodetic Survey). This network of identical seismic instruments consisted of 120 stations in 60 countries. Although the network was motivated by nuclear test monitoring, the WWSSN facilitated numerous advances in observational seismology. From the IGY to the present, the network has been upgraded (High-Gain Long-Period Seismograph Network, Seismic Research Observatories, Digital WWSSN, Global Telemetered Seismograph Network, etc.) and expanded (International Deployment of Accelerometers, US National Seismic Network, China Digital Seismograph Network, Joint Seismic Project, etc.), bringing the modern day Global Seismographic Network (GSN) to a current state of approximately 150 stations. The GSN consists of state-of-the-art very broadband seismic transducers, continuous power and communications, and ancillary sensors including geodetic, geomagnetic, microbarographic, meteorological and other related instrumentation. Beyond the GSN, the system of global network observatories includes contributions from other international partners (e.g., GEOSCOPE, GEOFON, MEDNET, F-Net, CTBTO), forming an even larger backbone of permanent seismological observatories as a part of the International Federation of Digital Seismograph Networks. 50 years of seismic network operations have provided

Local magnitude determinations for intermountain seismic belt earthquakes from broadband digital data

USGS Publications Warehouse

Pechmann, J.C.; Nava, S.J.; Terra, F.M.; Bernier, J.C.

2007-01-01

The University of Utah Seismograph Stations (UUSS) earthquake catalogs for the Utah and Yellowstone National Park regions contain two types of size measurements: local magnitude (ML) and coda magnitude (MC), which is calibrated against ML. From 1962 through 1993, UUSS calculated ML values for southern and central Intermountain Seismic Belt earthquakes using maximum peak-to-peak (p-p) amplitudes on paper records from one to five Wood-Anderson (W-A) seismographs in Utah. For ML determinations of earthquakes since 1994, UUSS has utilized synthetic W-A seismograms from U.S. National Seismic Network and UUSS broadband digital telemetry stations in the region, which numbered 23 by the end of our study period on 30 June 2002. This change has greatly increased the percentage of earthquakes for which ML can be determined. It is now possible to determine ML for all M ???3 earthquakes in the Utah and Yellowstone regions and earthquakes as small as M <1 in some areas. To maintain continuity in the magnitudes in the UUSS earthquake catalogs, we determined empirical ML station corrections that minimize differences between MLs calculated from paper and synthetic W-A records. Application of these station corrections, in combination with distance corrections from Richter (1958) which have been in use at UUSS since 1962, produces ML values that do not show any significant distance dependence. ML determinations for the Utah and Yellowstone regions for 1981-2002 using our station corrections and Richter's distance corrections have provided a reliable data set for recalibrating the MC scales for these regions. Our revised ML values are consistent with available moment magnitude determinations for Intermountain Seismic Belt earthquakes. To facilitate automatic ML measurements, we analyzed the distribution of the times of maximum p-p amplitudes in synthetic W-A records. A 30-sec time window for maximum amplitudes, beginning 5 sec before the predicted Sg time, encompasses 95% of the

Monitoring Instrument Performance in Regional Broadband Seismic Network Using Ambient Seismic Noise

NASA Astrophysics Data System (ADS)

Ye, F.; Lyu, S.; Lin, J.

2017-12-01

In the past ten years, the number of seismic stations has increased significantly, and regional seismic networks with advanced technology have been gradually developed all over the world. The resulting broadband data help to improve the seismological research. It is important to monitor the performance of broadband instruments in a new network in a long period of time to ensure the accuracy of seismic records. Here, we propose a method that uses ambient noise data in the period range 5-25 s to monitor instrument performance and check data quality in situ. The method is based on an analysis of amplitude and phase index parameters calculated from pairwise cross-correlations of three stations, which provides multiple references for reliable error estimates. Index parameters calculated daily during a two-year observation period are evaluated to identify stations with instrument response errors in near real time. During data processing, initial instrument responses are used in place of available instrument responses to simulate instrument response errors, which are then used to verify our results. We also examine feasibility of the tailing noise using data from stations selected from USArray in different locations and analyze the possible instrumental errors resulting in time-shifts used to verify the method. Additionally, we show an application that effects of instrument response errors that experience pole-zeros variations on monitoring temporal variations in crustal properties appear statistically significant velocity perturbation larger than the standard deviation. The results indicate that monitoring seismic instrument performance helps eliminate data pollution before analysis begins.

The International Space Station: A National Science Laboratory

NASA Technical Reports Server (NTRS)

Giblin, Timothy W.

2011-01-01

After more than a decade of assembly missions and on the heels of the final voyage of Space Shuttle Discovery, the International Space Station (ISS) has reached assembly completion. With visiting spacecraft now docking with the ISS on a regular basis, the Station now serves as a National Laboratory to scientists back on Earth. ISS strengthens relationships among NASA, other Federal entities, higher educational institutions, and the private sector in the pursuit of national priorities for the advancement of science, technology, engineering, and mathematics. In this lecture we will explore the various areas of research onboard ISS to promote this advancement: (1) Human Research, (2) Biology & Biotechnology, (3) Physical & Material Sciences, (4) Technology, and (5) Earth & Space Science. The ISS National Laboratory will also open new paths for the exploration and economic development of space.

Very Fast Estimation of Epicentral Distance and Magnitude from a Single Three Component Seismic Station Using Machine Learning Techniques

NASA Astrophysics Data System (ADS)

Ochoa Gutierrez, L. H.; Niño Vasquez, L. F.; Vargas-Jimenez, C. A.

2012-12-01

To minimize adverse effects originated by high magnitude earthquakes, early warning has become a powerful tool to anticipate a seismic wave arrival to an specific location and lets to bring people and government agencies opportune information to initiate a fast response. To do this, a very fast and accurate characterization of the event must be done but this process is often made using seismograms recorded in at least 4 stations where processing time is usually greater than the wave travel time to the interest area, mainly in coarse networks. A faster process can be done if only one three component seismic station is used that is the closest unsaturated station respect to the epicenter. Here we present a Support Vector Regression algorithm which calculates Magnitude and Epicentral Distance using only 5 seconds of signal since P wave onset. This algorithm was trained with 36 records of historical earthquakes where the input were regression parameters of an exponential function estimated by least squares, corresponding to the waveform envelope and the maximum value of the observed waveform for each component in one single station. A 10 fold Cross Validation was applied for a Normalized Polynomial Kernel obtaining the mean absolute error for different exponents and complexity parameters. Magnitude could be estimated with 0.16 of mean absolute error and the distance with an error of 7.5 km for distances within 60 to 120 km. This kind of algorithm is easy to implement in hardware and can be used directly in the field station to make possible the broadcast of estimations of this values to generate fast decisions at seismological control centers, increasing the possibility to have an effective reactiontribute and Descriptors calculator for SVR model training and test

The data quality analyzer: A quality control program for seismic data

NASA Astrophysics Data System (ADS)

Ringler, A. T.; Hagerty, M. T.; Holland, J.; Gonzales, A.; Gee, L. S.; Edwards, J. D.; Wilson, D.; Baker, A. M.

2015-03-01

for earthquakes) on stations in the Global Seismographic Network and Advanced National Seismic System.

Seismic Yield Estimates of UTTR Surface Explosions

NASA Astrophysics Data System (ADS)

Hayward, C.; Park, J.; Stump, B. W.

2016-12-01

Since 2007 the Utah Test and Training Range (UTTR) has used explosive demolition as a method to destroy excess solid rocket motors ranging in size from 19 tons to less than 2 tons. From 2007 to 2014, 20 high quality seismic stations within 180 km recorded most of the more than 200 demolitions. This provides an interesting dataset to examine seismic source scaling for surface explosions. Based upon observer records, shots were of 4 sizes, corresponding to the size of the rocket motors. Instrument corrections for the stations were quality controlled by examining the P-wave amplitudes of all magnitude 6.5-8 earthquakes from 30 to 90 degrees away. For each station recording, the instrument corrected RMS seismic amplitude in the first 10 seconds after the P-onset was calculated. Waveforms at any given station for all the observed explosions are nearly identical. The observed RMS amplitudes were fit to a model including a term for combined distance and station correction, a term for observed RMS amplitude, and an error term for the actual demolition size. The observed seismic yield relationship is RMS=k*Weight2/3 . Estimated yields for the largest shots vary by about 50% from the stated weights, with a nearly normal distribution.

UMTS rapid response real-time seismic networks: implementation and strategies at INGV

NASA Astrophysics Data System (ADS)

Govoni, A.; Margheriti, L.; Moretti, M.; Lauciani, V.; Sensale, G.; Bucci, A.; Criscuoli, F.

2015-12-01

Universal Mobile Telecommunications System (UMTS) and its evolutions are nowadays the most affordable and widespread data communication infrastructure available almost world wide. Moreover the always growing cellular phone market is pushing the development of new devices with higher performances and lower power consumption. All these characteristics make UMTS really useful for the implementation of an "easy to deploy" temporary real-time seismic station. Despite these remarkable features, there are many drawbacks that must be properly taken in account to effectively transmit the seismic data: Internet security, signal and service availability, power consumption. - Internet security: exposing seismological data services and seismic stations to the Internet is dangerous, attack prone and can lead to downtimes in the services, so we setup a dedicated Virtual Private Network (VPN) service to protect all the connected devices. - Signal and service availability: while for temporary experiment a carefull planning and an accurate site selection can minimize the problem, this is not always the case with rapid response networks. Moreover, as with any other leased line, the availability of the UMTS service during a seismic crisis is basically unpredictable. Nowadays in Italy during a major national emergency a Committee of the Italian Civil Defense ensures unified management and coordination of emergency activities. Inside it the telecom companies are committed to give support to the crisis management improving the standards in their communication networks. - Power consumption: it is at least of the order of that of the seismic station and, being related to data flow and signal quality is largely unpredictable. While the most secure option consists in adding a second independent solar power supply to the seismic station, this is not always a very convenient solution since it doubles the cost and doubles the equipment on site. We found that an acceptable trade-off is to add an

Determination of Rayleigh wave ellipticity using single-station and array-based processing of ambient seismic noise

NASA Astrophysics Data System (ADS)

Workman, Eli Joseph

We present a single-station method for the determination of Rayleigh wave ellipticity, or Rayleigh wave horizontal to vertical amplitude ratio (H/V) using Frequency Dependent Polarization Analysis (FDPA). This procedure uses singular value decomposition of 3-by-3 spectral covariance matrices over 1-hr time windows to determine properties of the ambient seismic noise field such as particle motion and dominant wave-type. In FPDA, if the noise is mostly dominated by a primary singular value and the phase difference is roughly 90° between the major horizontal axis and the vertical axis of the corresponding singular vector, we infer that Rayleigh waves are dominant and measure an H/V ratio for that hour and frequency bin. We perform this analysis for all available data from the Earthscope Transportable Array between 2004 and 2014. We compare the observed Rayleigh wave H/V ratios with those previously measured by multicomponent, multistation noise cross-correlation (NCC), as well as classical noise spectrum H/V ratio analysis (NSHV). At 8 sec the results from all three methods agree, suggesting that the ambient seismic noise field is Rayleigh wave dominated. Between 10 and 30 sec, while the general pattern agrees well, the results from FDPA and NSHV are persistently slightly higher ( 2%) and significantly higher (>20%), respectively, than results from the array-based NCC. This is likely caused by contamination from other wave types (i.e., Love waves, body waves, and tilt noise) in the single station methods, but it could also reflect a small, persistent error in NCC. Additionally, we find that the single station method has difficulty retrieving robust Rayleigh wave H/V ratios within major sedimentary basins, such as the Williston Basin and Mississippi Embayment, where the noise field is likely dominated by reverberating Love waves.

New Observations of Seismic Group Velocities in the Western Solomon Islands from Cross-Correlation of Ambient Seismic Noise

NASA Astrophysics Data System (ADS)

Ku, C. S.; You, S. H.; Kuo, Y. T.; Huang, B. S.; Wu, Y. M.; Chen, Y. G.; Taylor, F. W.

2015-12-01

A MW 8.1 earthquake occurred on 1 April 2007 in the western Solomon Islands. Following this event, a damaging tsunami was induced and hit the Island Gizo where the capital city of Western Province of Solomon Islands located. Several buildings of this city were destroyed and several peoples lost their lives during this earthquake. However, during this earthquake, no near source seismic instrument has been installed in this region. The seismic evaluations for the aftershock sequence, the possible earthquake early warning and tsunami warning were unavailable. For the purpose of knowing more detailed information about seismic activity in this region, we have installed 9 seismic stations (with Trillium 120PA broadband seismometer and Q330S 24bit digitizer) around the rupture zone of the 2007 earthquake since September of 2009. Within a decade, it has been demonstrated both theoretically and experimentally that the Green's function or impulse response between two seismic stations can be retrieved from the cross-correlation of ambient noise. In this study, 6 stations' observations which are more complete during 2011/10 ~ 2012/12 period, were selected for the purpose of the cross-correlation analysis of ambient seismic noise. The group velocities at period 2-20 seconds of 15 station-pairs were extracted by using multiple filter technique (MFT) method. The analyzed results of this study presented significant results of group velocities with higher frequency contents than other studies (20-60 seconds in usually cases) and opened new opportunities to study the shallow crustal structure of the western Solomon Islands.

Exploring Large-Scale Cross-Correlation for Teleseismic and Regional Seismic Event Characterization

NASA Astrophysics Data System (ADS)

Dodge, Doug; Walter, William; Myers, Steve; Ford, Sean; Harris, Dave; Ruppert, Stan; Buttler, Dave; Hauk, Terri

2013-04-01

The decrease in costs of both digital storage space and computation power invites new methods of seismic data processing. At Lawrence Livermore National Laboratory(LLNL) we operate a growing research database of seismic events and waveforms for nuclear explosion monitoring and other applications. Currently the LLNL database contains several million events associated with tens of millions of waveforms at thousands of stations. We are making use of this database to explore the power of seismic waveform correlation to quantify signal similarities, to discover new events not in catalogs, and to more accurately locate events and identify source types. Building on the very efficient correlation methodologies of Harris and Dodge (2011) we computed the waveform correlation for event pairs in the LLNL database in two ways. First we performed entire waveform cross-correlation over seven distinct frequency bands. The correlation coefficient exceeds 0.6 for more than 40 million waveform pairs for several hundred thousand events at more than a thousand stations. These correlations reveal clusters of mining events and aftershock sequences, which can be used to readily identify and locate events. Second we determine relative pick times by correlating signals in time windows for distinct seismic phases. These correlated picks are then used to perform very high accuracy event relocations. We are examining the percentage of events that correlate as a function of magnitude and observing station distance in selected high seismicity regions. Combining these empirical results and those using synthetic data, we are working to quantify relationships between correlation and event pair separation (in epicenter and depth) as well as mechanism differences. Our exploration of these techniques on a large seismic database is in process and we will report on our findings in more detail at the meeting.

Exploring Large-Scale Cross-Correlation for Teleseismic and Regional Seismic Event Characterization

NASA Astrophysics Data System (ADS)

Dodge, D.; Walter, W. R.; Myers, S. C.; Ford, S. R.; Harris, D.; Ruppert, S.; Buttler, D.; Hauk, T. F.

2012-12-01

The decrease in costs of both digital storage space and computation power invites new methods of seismic data processing. At Lawrence Livermore National Laboratory (LLNL) we operate a growing research database of seismic events and waveforms for nuclear explosion monitoring and other applications. Currently the LLNL database contains several million events associated with tens of millions of waveforms at thousands of stations. We are making use of this database to explore the power of seismic waveform correlation to quantify signal similarities, to discover new events not in catalogs, and to more accurately locate events and identify source types. Building on the very efficient correlation methodologies of Harris and Dodge (2011) we computed the waveform correlation for event pairs in the LLNL database in two ways. First we performed entire waveform cross-correlation over seven distinct frequency bands. The correlation coefficient exceeds 0.6 for more than 40 million waveform pairs for several hundred thousand events at more than a thousand stations. These correlations reveal clusters of mining events and aftershock sequences, which can be used to readily identify and locate events. Second we determine relative pick times by correlating signals in time windows for distinct seismic phases. These correlated picks are then used to perform very high accuracy event relocations. We are examining the percentage of events that correlate as a function of magnitude and observing station distance in selected high seismicity regions. Combining these empirical results and those using synthetic data, we are working to quantify relationships between correlation and event pair separation (in epicenter and depth) as well as mechanism differences. Our exploration of these techniques on a large seismic database is in process and we will report on our findings in more detail at the meeting.

Triggered Seismicity in Utah from the November 3, 2002, Denali Fault Earthquake

NASA Astrophysics Data System (ADS)

Pankow, K. L.; Nava, S. J.; Pechmann, J. C.; Arabasz, W. J.

2002-12-01

Coincident with the arrival of the surface waves from the November 3, 2002, Mw 7.9 Denali Fault, Alaska earthquake (DFE), the University of Utah Seismograph Stations (UUSS) regional seismic network detected a marked increase in seismicity along the Intermountain Seismic Belt (ISB) in central and north-central Utah. The number of earthquakes per day in Utah located automatically by the UUSS's Earthworm system in the week following the DFE was approximately double the long-term average during the preceding nine months. From these preliminary data, the increased seismicity appears to be characterized by small magnitude events (M = 3.2) and concentrated in five distinct spatial clusters within the ISB between 38.75°and 42.0° N. The first of these earthquakes was an M 2.2 event located ~20 km east of Salt Lake City, Utah, which occurred during the arrival of the Love waves from the DFE. The increase in Utah earthquake activity at the time of the arrival of the surface waves from the DFE suggests that these surface waves triggered earthquakes in Utah at distances of more than 3,000 km from the source. We estimated the peak dynamic shear stress caused by these surface waves from measurements of their peak vector velocities at 43 recording sites: 37 strong-motion stations of the Advanced National Seismic System and six broadband stations. (The records from six other broadband instruments in the region of interest were clipped.) The estimated peak stresses ranged from 1.2 bars to 3.5 bars with a mean of 2.3 bars, and generally occurred during the arrival of Love waves of ~15 sec period. These peak dynamic shear stress estimates are comparable to those obtained from recordings of the 1992 Mw 7.3 Landers, California, earthquake in regions where the Landers earthquake triggered increased seismicity. We plan to present more complete analyses of UUSS seismic network data, further testing our hypothesis that the DFE remotely triggered seismicity in Utah. This hypothesis is

Short-Period Seismic Noise in Vorkuta (Russia)

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

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,more » 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

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.

Preliminary seismic studies at Ceboruco Volcano

NASA Astrophysics Data System (ADS)

Escudero, C. R.; Nunez-Cornu, F. J.; Ochoa, J.; Robles, F. J.

2012-12-01

Many societies and their economies endure the disastrous consequences of destructive volcanic eruptions. The Ceboruco stratovolcano is located at the west of the Mexican volcanic belt at 21.125o north, 76 km from the pacific coast and 2,280 meters above sea level. It has an eruptive recurrence of 200 years and its last activity was at 1875. This natural hazard could affect more than eight communities and important highways. Scientific knowledge constitutes the only way to avoid or at least to mitigate the negative effects of an eventual eruptive event, accordingly the main objective of this project is monitor and analyze the potential destructive effects of the Ceboruco volcano. Seismic studies began at 2003 with the deployment of one MARSlite station equipped LE3d (1Hz) sensor. Station that works until 2009 and allow us to identify and characterize the seismic activity associated to the volcano;. Since March 2012 we installed four seismic stations, each includes a digital acquisition system TAURUS of Nanometrix and a Lennartz 3D lite seismometer. Batteries are change and data collected monthly. We use the data to establish the average seismic activity rate; we also aim to corroborate previous studies that showed four families of seismic events; and to localize and make preliminary evaluations of the events.

OGS improvements in the year 2011 in running the Northeastern Italy Seismic Network

NASA Astrophysics Data System (ADS)

Bragato, P. L.; Pesaresi, D.; Saraò, A.; Di Bartolomeo, P.; Durı, G.

2012-04-01

The Centro di Ricerche Sismologiche (CRS, Seismological Research Center) of the Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS, Italian National Institute for Oceanography and Experimental Geophysics) in Udine (Italy) after the strong earthquake of magnitude M=6.4 occurred in 1976 in the Italian Friuli-Venezia Giulia region, started to operate the Northeastern Italy Seismic Network: it currently consists of 15 very sensitive broad band and 21 simpler short period seismic stations, all telemetered to and acquired in real time at the OGS-CRS data center in Udine. Real time data exchange agreements in place with other Italian, Slovenian, Austrian and Swiss seismological institutes lead to a total number of about 100 seismic stations acquired in real time, which makes the OGS the reference institute for seismic monitoring of Northeastern Italy. Since 2002 OGS-CRS is using the Antelope software suite on several workstations plus a SUN Cluster as the main tool for collecting, analyzing, archiving and exchanging seismic data, initially in the framework of the EU Interreg IIIA project "Trans-national seismological networks in the South-Eastern Alps". SeisComP is also used as a real time data exchange server tool. In order to improve the seismological monitoring of the Northeastern Italy area, at OGS-CRS we tuned existing programs and created ad hoc ones like: a customized web server named PickServer to manually relocate earthquakes, a script for automatic moment tensor determination, scripts for web publishing of earthquake parametric data, waveforms, state of health parameters and shaking maps, noise characterization by means of automatic spectra analysis, and last but not least scripts for email/SMS/fax alerting. The OGS-CRS Real Time Seismological website (RTS, http://rts.crs.inogs.it/) operative since several years was initially developed in the framework of the Italian DPC-INGV S3 Project: the RTS website shows classic earthquake locations

Advanced National Seismic System—Current status, development opportunities, and priorities for 2017–2027

USGS Publications Warehouse

,

2017-05-25

SummaryEarthquakes pose a threat to the safety of over 143 million people living in the United States. Earthquake impacts can be significantly reduced if communities understand their risk and take proactive steps to mitigate that risk. The Advanced National Seismic System (ANSS) is a cooperative effort to collect and analyze seismic and geodetic data on earthquakes, issue timely and reliable notifications of their occurrence and impacts, and provide data for earthquake research and the hazard and risk assessments that are the foundation for creating an earthquakeresilient nation.

The 16 August 1997 Novaya Zemlya seismic event as viewed from GSN stations KEV and KBS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hartse, H.E.

1997-11-01

Using current and historic seismic records from Global Seismic Network stations KEV and KBS, the authors find that S minus P arrival time comparisons between nuclear explosions and the 16 August 1997 seismic event (m{sub b} {approx} 3.6) from near Novaya Zemlya clearly indicate that (relative to KEV) the 16 August event occurred at least 80 km east of the Russian test site. Including S minus P arrival times from KBS constrains the location to beneath the Kara Sea and in good agreement with previously reported locations, over 100 km southeast of the test site. From an analysis of P{submore » n}/S{sub n} waveform ratios at frequencies above 4 Hz, they find that the 16 August event falls within the population of regional earthquakes and is distinctly separated from Novaya Zemlya and other northern Eurasian nuclear explosion populations. Thus, given its location and waveform characteristics, they conclude the 16 August event was an earthquake. The 16 August event was not detected at teleseismic distances, and thus, this event provides a good example of the regional detection, location, and identification efforts that will be required to monitor the Comprehensive Test Ban Treaty below m{sub b} {approx} 4.« less

SIG-VISA: Signal-based Vertically Integrated Seismic Monitoring

NASA Astrophysics Data System (ADS)

Moore, D.; Mayeda, K. M.; Myers, S. C.; Russell, S.

2013-12-01

Traditional seismic monitoring systems rely on discrete detections produced by station processing software; however, while such detections may constitute a useful summary of station activity, they discard large amounts of information present in the original recorded signal. We present SIG-VISA (Signal-based Vertically Integrated Seismic Analysis), a system for seismic monitoring through Bayesian inference on seismic signals. By directly modeling the recorded signal, our approach incorporates additional information unavailable to detection-based methods, enabling higher sensitivity and more accurate localization using techniques such as waveform matching. SIG-VISA's Bayesian forward model of seismic signal envelopes includes physically-derived models of travel times and source characteristics as well as Gaussian process (kriging) statistical models of signal properties that combine interpolation of historical data with extrapolation of learned physical trends. Applying Bayesian inference, we evaluate the model on earthquakes as well as the 2009 DPRK test event, demonstrating a waveform matching effect as part of the probabilistic inference, along with results on event localization and sensitivity. In particular, we demonstrate increased sensitivity from signal-based modeling, in which the SIGVISA signal model finds statistical evidence for arrivals even at stations for which the IMS station processing failed to register any detection.

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. 

A Dramatic Increase in Seismic Observations in the Central and Eastern US

NASA Astrophysics Data System (ADS)

Woodward, R.; Busby, R.; Simpson, D.; Alvarez, M.; Vernon, F.

2009-05-01

The USArray Transportable Array (TA) is a network of 400 seismograph stations that is systematically moving west-to-east across the contiguous United States. The TA is part of the National Science Foundation's multi- disciplinary EarthScope program. The TA has already occupied over 700 stations in the western US, and is continuing its multi-year migration towards the Atlantic coast before heading for Alaska. The stations use a grid-like deployment with 70 km separation between stations. At any given time there are approximately 400 stations operational, occupying a nominal 800 km by 2000 km "footprint." Each station is operated for two years. TA stations consist of three component broadband seismometers, with a few sites in the westernmost United States also including three component strong motion instruments. The instruments are installed about two meters below the surface, in thermally stable vaults. All stations transmit continuous data in near-real-time, and the data are freely distributed through the IRIS Data Management Center. TA stations can be upgraded to incorporate high frequency or strong motion instrument. Organizations can also "adopt" stations after installation by reimbursing the cost of the hardware, so that the stations become permanent. The TA is presently operating in the swath of the country extending from Texas to Montana. From 2010 to 2013 the TA will occupy ~800 sites in the central and eastern US. The array will be centered on the New Madrid, MO region during the bicentennial of the 1811-1812 earthquakes. During the TA deployment every existing or planned nuclear plant in the eastern US will be within 70 km of at least four new seismic stations. Thus, this station deployment in the eastern half of the US presents an unprecedented opportunity for improving source characterization, modeling the regional velocity and attenuation structure, and mapping seismic zones down to low magnitude thresholds. We will provide an overview of TA

Seismic and Geodetic Monitoring of the Nicoya, Costa Rica, Seismic Gap

NASA Astrophysics Data System (ADS)

Protti, M.; Gonzalez, V.; Schwartz, S.; Dixon, T.; Kato, T.; Kaneda, Y.; Simila, G.; Sampson, D.

2007-05-01

The Nicoya segment of the Middle America Trench has been recognized as a mature seismic gap with potential to generate a large earthquake in the near future (it ruptured with large earthquakes in 1853, 1900 and 1950). Low level of background seismicity and fast crustal deformation of the forearc are indicatives of strong coupling along the plate interface. Given its high seismic potential, the available data and especially the fact that the Nicoya peninsula extends over large part of the rupture area, this gap was selected as one of the two sites for a MARGINS-SEIZE experiment. With the goal of documenting the evolution of loading and stress release along this seismic gap, an international effort involving several institutions from Costa Rica, the United States and Japan is being carried out for over a decade in the region. This effort involves the installation of temporary and permanent seismic and geodetic networks. The seismic network includes short period, broad band and strong motion instruments. The seismic monitoring has provided valuable information on the geometry and characteristics of the plate interface. The geodetic network includes temporary and permanent GPS stations as well as surface and borehole tiltmeters. The geodetic networks have helped quantify the extend and degree of coupling. A continuously recording, three- station GPS network on the Nicoya Peninsula, Costa Rica, recorded what we believe is the first slow slip event observed along the plate interface of the Costa Rica subduction zone. We will present results from these monitoring networks. Collaborative international efforts are focused on expanding these seismic and geodetic networks to provide improved resolution of future creep events, to enhanced understanding of the mechanical behavior of the Nicoya subduction segment of the Middle American Trench and possibly capture the next large earthquake and its potential precursor deformation.

USGS National Seismic Hazard Maps

USGS Publications Warehouse

Frankel, A.D.; Mueller, C.S.; Barnhard, T.P.; Leyendecker, E.V.; Wesson, R.L.; Harmsen, S.C.; Klein, F.W.; Perkins, D.M.; Dickman, N.C.; Hanson, S.L.; Hopper, M.G.

2000-01-01

The U.S. Geological Survey (USGS) recently completed new probabilistic seismic hazard maps for the United States, including Alaska and Hawaii. These hazard maps form the basis of the probabilistic component of the design maps used in the 1997 edition of the NEHRP Recommended Provisions for Seismic Regulations for New Buildings and Other Structures, prepared by the Building Seismic Safety Council arid published by FEMA. The hazard maps depict peak horizontal ground acceleration and spectral response at 0.2, 0.3, and 1.0 sec periods, with 10%, 5%, and 2% probabilities of exceedance in 50 years, corresponding to return times of about 500, 1000, and 2500 years, respectively. In this paper we outline the methodology used to construct the hazard maps. There are three basic components to the maps. First, we use spatially smoothed historic seismicity as one portion of the hazard calculation. In this model, we apply the general observation that moderate and large earthquakes tend to occur near areas of previous small or moderate events, with some notable exceptions. Second, we consider large background source zones based on broad geologic criteria to quantify hazard in areas with little or no historic seismicity, but with the potential for generating large events. Third, we include the hazard from specific fault sources. We use about 450 faults in the western United States (WUS) and derive recurrence times from either geologic slip rates or the dating of pre-historic earthquakes from trenching of faults or other paleoseismic methods. Recurrence estimates for large earthquakes in New Madrid and Charleston, South Carolina, were taken from recent paleoliquefaction studies. We used logic trees to incorporate different seismicity models, fault recurrence models, Cascadia great earthquake scenarios, and ground-motion attenuation relations. We present disaggregation plots showing the contribution to hazard at four cities from potential earthquakes with various magnitudes and

Improving Station Performance by Building Isolation Walls in the Tunnel

NASA Astrophysics Data System (ADS)

Jia, Yan; Horn, Nikolaus; Leohardt, Roman

2014-05-01

Conrad Observatory is situated far away from roads and industrial areas on the Trafelberg in Lower Austria. At the end of the seismic tunnel, the main seismic instrument of the Observatory with a station code CONA is located. This station is one of the most important seismic stations in the Austrian Seismic Network (network code OE). The seismic observatory consists of a 145m long gallery and an underground laboratory building with several working areas. About 25 meters away from the station CONA, six temporary seismic stations were implemented for research purposes. Two of them were installed with the same equipment as CONA, while the remaining four stations were set up with digitizers having lower noise and higher resolution (Q330HR) and sensors with the same type (STS-2). In order to prevent possible disturbances by air pressure and temperature fluctuation, three walls were built inside of the tunnel. The first wall is located ca 63 meters from the tunnel entrance, while a set of double walls with a distance of 1.5 meters is placed about 53 meters from the first isolation wall but between the station CONA and the six temporary stations. To assess impact of the isolation walls on noise reduction and detection performance, investigations are conducted in two steps. The first study is carried out by comparing the noise level and detection performance between the station CONA behind the double walls and the stations in front of the double walls for verifying the noise isolation by the double walls. To evaluate the effect of the single wall, station noise level and detection performance were studied by comparing the results before and after the installation of the wall. Results and discussions will be presented. Additional experiment is conducted by filling insulation material inside of the aluminium boxes of the sensors (above and around the sensors). This should help us to determine an optimal insulation of the sensors with respect to pressure and temperature

Tools for educational access to seismic data

NASA Astrophysics Data System (ADS)

Taber, J. J.; Welti, R.; Bravo, T. K.; Hubenthal, M.; Frechette, K.

2017-12-01

Student engagement can be increased both by providing easy access to real data, and by addressing newsworthy events such as recent large earthquakes. IRIS EPO has a suite of access and visualization tools that can be used for such engagement, including a set of three tools that allow students to explore global seismicity, use seismic data to determine Earth structure, and view and analyze near-real-time ground motion data in the classroom. These tools are linked to online lessons that are designed for use in middle school through introductory undergraduate classes. The IRIS Earthquake Browser allows discovery of key aspects of plate tectonics, earthquake locations (in pseudo 3D) and seismicity rates and patterns. IEB quickly displays up to 20,000 seismic events over up to 30 years, making it one of the most responsive, practical ways to visualize historical seismicity in a browser. Maps are bookmarkable and preserve state, meaning IEB map links can be shared or worked into a lesson plan. The Global Seismogram Plotter automatically creates visually clear seismic record sections from selected large earthquakes that are tablet-friendly and can also to be printed for use in a classroom without computers. The plots are designed to be appropriate for use with no parameters to set, but users can also modify the plots, such as including a recording station near a chosen location. A guided exercise is provided where students use the record section to discover the diameter of Earth's outer core. Students can pick and compare phase arrival times onscreen which is key to performing the exercise. A companion station map shows station locations and further information and is linked to the record section. jAmaSeis displays seismic data in real-time from either a local instrument and/or from remote seismic stations that stream data using standard seismic data protocols, and can be used in the classroom or as a public display. Users can filter data, fit a seismogram to travel time

Improvement of real-time seismic magnitude estimation by combining seismic and geodetic instrumentation

NASA Astrophysics Data System (ADS)

Goldberg, D.; Bock, Y.; Melgar, D.

2017-12-01

Rapid seismic magnitude assessment is a top priority for earthquake and tsunami early warning systems. For the largest earthquakes, seismic instrumentation tends to underestimate the magnitude, leading to an insufficient early warning, particularly in the case of tsunami evacuation orders. GPS instrumentation provides more accurate magnitude estimations using near-field stations, but isn't sensitive enough to detect the first seismic wave arrivals, thereby limiting solution speed. By optimally combining collocated seismic and GPS instruments, we demonstrate improved solution speed of earthquake magnitude for the largest seismic events. We present a real-time implementation of magnitude-scaling relations that adapts to consider the length of the recording, reflecting the observed evolution of ground motion with time.

Siting of USArray Seismic Stations in North Carolina and southern Virginia: Experience of NC-1 Team

NASA Astrophysics Data System (ADS)

Martin, P.; Howard, J.; Horne, T.

2012-12-01

The USArray component of the EarthScope, a transportable array of 400 seismometers installed in a grid about 70 km apart, is in the next two years entering its final stage with station deployment along the Atlantic coast of the United States. Here, we present the experience of the student-faculty team from North Carolina Central University (NCCU) in finding and documenting the suitable sites for the twenty five USArray stations in North Carolina and southern Virginia. The ideal sites are easily accessible yet far from traffic and other sources of noise, with good cell phone coverage, sun exposure and out of flood-prone areas. Although the initial selection of potential locations was done using geospatial mapping and analysis software provided by EarthScope, finding and finalizing the sites involved driving more then 1,000 miles each week for over two months inspecting possible site locations. Aside from driving, the majority of time was spent talking about the EarthScope project and hosting of USArray stations to mostly reluctant landowners. In addition to facing various challenges in finding appropriate sites due to land use issues, such as suburban sprawl of central North Carolina, or topography factors, such as low lying flood prone coastal areas, by far the major challenge was finding the landowners willing to host the seismic station for the necessary three years. In addition to involving students from an HBCU in seismology related project and increasing the visibility of NCCU geophysics program in the University and local community through publicity releases in local media and on university web site, the project had an important outreach component. As North Carolina is located along the seismically quiet, passive Atlantic margin, most residents are not familiar with earthquakes and seismology and the siting experience provided students an opportunity to practice explaining the earthquake research to the general public. The dialog also highlighted science

Seismic excitation by space shuttles

USGS Publications Warehouse

Kanamori, H.; Mori, J.; Sturtevant, B.; Anderson, D.L.; Heaton, T.

1992-01-01

Shock waves generated by the space shuttles Columbia (August 13, 1989), Atlantis (April 11, 1991) and Discovery (September 18, 1991) on their return to Edwards Air Force Base, California, were recorded by TERRAscope (Caltech's broadband seismic network), the Caltech-U.S.G.S Southern California Seismic Network (SCSN), and the University of Southern California (USC) Los Angeles Basin Seismic Network. The spatial pattern of the arrival times exhibits hyperbolic shock fronts from which the path, velocity and altitude of the space shuttle could be determined. The shock wave was acoustically coupled to the ground, converted to a seismic wave, and recorded clearly at the broadband TERRAscope stations. The acoustic coupling occurred very differently depending on the conditions of the Earth's surface surrounding the station. For a seismic station located on hard bedrock, the shock wave (N wave) was clearly recorded with little distortion. Aside from the N wave, very little acoustic coupling of the shock wave energy to the ground occurred at these sites. The observed N wave record was used to estimate the overpressure of the shock wave accurately; a pressure change of 0.5 to 2.2 mbars was obtained. For a seismic station located close to the ocean or soft sedimentary basins, a significant amount of shock wave energy was transferred to the ground through acoustic coupling of the shock wave and the oceanic Rayleigh wave. A distinct topography such as a mountain range was found effective to couple the shock wave energy to the ground. Shock wave energy was also coupled to the ground very effectively through large man made structures such as high rise buildings and offshore oil drilling platforms. For the space shuttle Columbia, in particular, a distinct pulse having a period of about 2 to 3 seconds was observed, 12.5 s before the shock wave, with a broadband seismograph in Pasadena. This pulse was probably excited by the high rise buildings in downtown Los Angeles which were

Using Seismic Interferometry to Investigate Seismic Swarms

NASA Astrophysics Data System (ADS)

Matzel, E.; Morency, C.; Templeton, D. C.

2017-12-01

Seismicity provides a direct means of measuring the physical characteristics of active tectonic features such as fault zones. Hundreds of small earthquakes often occur along a fault during a seismic swarm. This seismicity helps define the tectonically active region. When processed using novel geophysical techniques, we can isolate the energy sensitive to the fault, itself. Here we focus on two methods of seismic interferometry, ambient noise correlation (ANC) and the virtual seismometer method (VSM). ANC is based on the observation that the Earth's background noise includes coherent energy, which can be recovered by observing over long time periods and allowing the incoherent energy to cancel out. The cross correlation of ambient noise between a pair of stations results in a waveform that is identical to the seismogram that would result if an impulsive source located at one of the stations was recorded at the other, the Green function (GF). The calculation of the GF is often stable after a few weeks of continuous data correlation, any perturbations to the GF after that point are directly related to changes in the subsurface and can be used for 4D monitoring.VSM is a style of seismic interferometry that provides fast, precise, high frequency estimates of the Green's function (GF) between earthquakes. VSM illuminates the subsurface precisely where the pressures are changing and has the potential to image the evolution of seismicity over time, including changes in the style of faulting. With hundreds of earthquakes, we can calculate thousands of waveforms. At the same time, VSM collapses the computational domain, often by 2-3 orders of magnitude. This allows us to do high frequency 3D modeling in the fault region. Using data from a swarm of earthquakes near the Salton Sea, we demonstrate the power of these techniques, illustrating our ability to scale from the far field, where sources are well separated, to the near field where their locations fall within each other

Evaluation of the new infrastructure for French Permanent Broadband Stations in Auvergne (France).

NASA Astrophysics Data System (ADS)

Douchain, J. M.; Regis, E.; Battaglia, J.; Vergne, J.

2017-12-01

French seismologic and geodetic network (RESIF) is a national equipment for the observation and understanding of the solid Earth. It is an instrument aimed at acquiring new top-quality data for disciplines like seismology, geodesy and gravimetry to advance the understanding of the dynamics of our planet. The seismology component of RESIF, with its homogeneous coverage of the territory, will allow better localisation and characterisation of seismic activityover a wide range of magnitudes as well as provide high quality data for research The Auvergne Seismic Network (ASN) manages seismic stations in the center of france since the beginning of the 80's and continuously ugrades them. Nowadays, 21 stations (velocimeters and accelerometers) are deployed to monitor the Massif Central seismic activity. In the future, the ASN will run 15 broadband stations that will be part of RESIF network. Six of theses sites already have former generation instrumentation (short period sensors buried in the ground, low dynamic) but others are completely new. In june 2017, 4 permanent seismic stations have been upgraded to the new standard installation type for open environment. The chozen infrastructure is a 5 meter drilling equiped with a posthole broadband sensor. Prior to these final installations, on each site, Trillium 120 PA have been installed for 2 temporary experiments. The first one consisted of a direct burial installations at about 80 centimeters depth and lasted for 1 or 2 months. The second dataset was recorded in shallow seismic vaults, during 6 months.In this study, we compare, for each site, data recorded with the 3 configurations in order to evaluate the profits of the new RESIF installations. For this purpose, we compare the probability density fonctions to evaluate noise levels, as well as sprectrograms and hourly detection number. Our results show that the installation of sensors in drillings greatly improves the quality of data at low and high frequencies.

Large-N Nodal Seismic Deployment at Mount St Helens

NASA Astrophysics Data System (ADS)

Hansen, S. M.; Schmandt, B.; Vidale, J. E.; Creager, K. C.; Levander, A.; Kiser, E.; Barklage, M.; Hollis, D.

2014-12-01

In late July of 2014 over 900 autonomous short period seismometers were deployed within 12 km of the summit crater at Mount St Helens. In concert with the larger iMUSH experiment, these data constitute the largest seismic interrogation of an active volcano ever conducted. The array was deployed along the road and trail system of the national volcanic monument and adjacent regions with an average station spacing of 250 meters and included several station clusters with increased sampling density. The 10 Hz phones recorded the vertical component wavefield continuously at 250 Hz sampling rate over a period of approximately two weeks. During the recording time, the Pacific Northwest Seismic Network detected ~65 earthquakes within the array footprint ranging in magnitude from -0.9 to 1.1, the majority of which were located beneath the crater at less than 10 km depth. In addition to the natural seismicity, 23 explosion sources from the iMUSH active source experiment were recorded, several of which exceeded magnitude 2. Preliminary results for this project will include an expanded event catalog as the array should significantly reduce the detection threshold. The sheer number of instruments allows for stacking of station clusters producing high signal-to-noise beam traces which can be used for event triggering and for creating waveform templates to measure relative travel-times across the array via cross-correlation. The ability of the array to estimate focal mechanisms from event radiation patterns and delineate complex path effects will also be investigated. The density and azimuthal coverage provide by this array offers an excellent opportunity to investigate short-wavelength variations of the seismic wavefield in a complex geologic environment. Previous seismic tomography results suggest the presence of a shallow magma chamber at 1-3 km depth near the region of shallow seismicity as evidenced by a P wave low-velocity anomaly of at least -5.5% [Waite and Moran, 2009

Mammoth Mountain, California broadband seismic experiment

NASA Astrophysics Data System (ADS)

Dawson, P. B.; Pitt, A. M.; Wilkinson, S. K.; Chouet, B. A.; Hill, D. P.; Mangan, M.; Prejean, S. G.; Read, C.; Shelly, D. R.

2013-12-01

Mammoth Mountain is a young cumulo-volcano located on the southwest rim of Long Valley caldera, California. Current volcanic processes beneath Mammoth Mountain are manifested in a wide range of seismic signals, including swarms of shallow volcano-tectonic earthquakes, upper and mid-crustal long-period earthquakes, swarms of brittle-failure earthquakes in the lower crust, and shallow (3-km depth) very-long-period earthquakes. Diffuse emissions of C02 began after a magmatic dike injection beneath the volcano in 1989, and continue to present time. These indications of volcanic unrest drive an extensive monitoring effort of the volcano by the USGS Volcano Hazards Program. As part of this effort, eleven broadband seismometers were deployed on Mammoth Mountain in November 2011. This temporary deployment is expected to run through the fall of 2013. These stations supplement the local short-period and broadband seismic stations of the Northern California Seismic Network (NCSN) and provide a combined network of eighteen broadband stations operating within 4 km of the summit of Mammoth Mountain. Data from the temporary stations are not available in real-time, requiring the merging of the data from the temporary and permanent networks, timing of phases, and relocation of seismic events to be accomplished outside of the standard NCSN processing scheme. The timing of phases is accomplished through an interactive Java-based phase-picking routine, and the relocation of seismicity is achieved using the probabilistic non-linear software package NonLinLoc, distributed under the GNU General Public License by Alomax Scientific. Several swarms of shallow volcano-tectonic earthquakes, spasmodic bursts of high-frequency earthquakes, a few long-period events located within or below the edifice of Mammoth Mountain and numerous mid-crustal long-period events have been recorded by the network. To date, about 900 of the ~2400 events occurring beneath Mammoth Mountain since November 2011 have

Fully probabilistic seismic source inversion - Part 2: Modelling errors and station covariances

NASA Astrophysics Data System (ADS)

Stähler, Simon C.; Sigloch, Karin

2016-11-01

Seismic source inversion, a central task in seismology, is concerned with the estimation of earthquake source parameters and their uncertainties. Estimating uncertainties is particularly challenging because source inversion is a non-linear problem. In a companion paper, Stähler and Sigloch (2014) developed a method of fully Bayesian inference for source parameters, based on measurements of waveform cross-correlation between broadband, teleseismic body-wave observations and their modelled counterparts. This approach yields not only depth and moment tensor estimates but also source time functions. A prerequisite for Bayesian inference is the proper characterisation of the noise afflicting the measurements, a problem we address here. We show that, for realistic broadband body-wave seismograms, the systematic error due to an incomplete physical model affects waveform misfits more strongly than random, ambient background noise. In this situation, the waveform cross-correlation coefficient CC, or rather its decorrelation D = 1 - CC, performs more robustly as a misfit criterion than ℓp norms, more commonly used as sample-by-sample measures of misfit based on distances between individual time samples. From a set of over 900 user-supervised, deterministic earthquake source solutions treated as a quality-controlled reference, we derive the noise distribution on signal decorrelation D = 1 - CC of the broadband seismogram fits between observed and modelled waveforms. The noise on D is found to approximately follow a log-normal distribution, a fortunate fact that readily accommodates the formulation of an empirical likelihood function for D for our multivariate problem. The first and second moments of this multivariate distribution are shown to depend mostly on the signal-to-noise ratio (SNR) of the CC measurements and on the back-azimuthal distances of seismic stations. By identifying and quantifying this likelihood function, we make D and thus waveform cross

Demonstration of Regional Discrimination of Eurasian Seismic Events Using Observations at Soviet IRIS and CDSN Stations

DTIC Science & Technology

1992-03-01

Propagation of Lg Waves Across Eastern Europe and Asia, Lawrence Livermore National Laboratory Report, LLNL Report No. UCRL -52494. Press, F., and M. Ewing...the Nuclear Testing Ground in Eastern Kazakhstan, Lawrence Livermore National Laboratory Report, LLNL Report No. UCRL -52856. Ruzaikin, A., I. Nersesov...Derring Hall University Park, PA 16802 Blacksburg, VA 24061 Dr. Ralph Alewine, III Dr. Stephen Bratt DARPAftMRO Center for Seismic Studies 3701 North Fairax

Improved earthquake monitoring in the central and eastern United States in support of seismic assessments for critical facilities

USGS Publications Warehouse

Leith, William S.; Benz, Harley M.; Herrmann, Robert B.

2011-01-01

Evaluation of seismic monitoring capabilities in the central and eastern United States for critical facilities - including nuclear powerplants - focused on specific improvements to understand better the seismic hazards in the region. The report is not an assessment of seismic safety at nuclear plants. To accomplish the evaluation and to provide suggestions for improvements using funding from the American Recovery and Reinvestment Act of 2009, the U.S. Geological Survey examined addition of new strong-motion seismic stations in areas of seismic activity and addition of new seismic stations near nuclear power-plant locations, along with integration of data from the Transportable Array of some 400 mobile seismic stations. Some 38 and 68 stations, respectively, were suggested for addition in active seismic zones and near-power-plant locations. Expansion of databases for strong-motion and other earthquake source-characterization data also was evaluated. Recognizing pragmatic limitations of station deployment, augmentation of existing deployments provides improvements in source characterization by quantification of near-source attenuation in regions where larger earthquakes are expected. That augmentation also supports systematic data collection from existing networks. The report further utilizes the application of modeling procedures and processing algorithms, with the additional stations and the improved seismic databases, to leverage the capabilities of existing and expanded seismic arrays.

Data quality control and tools in passive seismic experiments exemplified on the Czech broadband seismic pool MOBNET in the AlpArray collaborative project

NASA Astrophysics Data System (ADS)

Vecsey, Luděk; Plomerová, Jaroslava; Jedlička, Petr; Munzarová, Helena; Babuška, Vladislav; AlpArray Working Group

2017-12-01

This paper focuses on major issues related to the data reliability and network performance of 20 broadband (BB) stations of the Czech (CZ) MOBNET (MOBile NETwork) seismic pool within the AlpArray seismic experiments. Currently used high-resolution seismological applications require high-quality data recorded for a sufficiently long time interval at seismological observatories and during the entire time of operation of the temporary stations. In this paper we present new hardware and software tools we have been developing during the last two decades while analysing data from several international passive experiments. The new tools help to assure the high-quality standard of broadband seismic data and eliminate potential errors before supplying data to seismological centres. Special attention is paid to crucial issues like the detection of sensor misorientation, timing problems, interchange of record components and/or their polarity reversal, sensor mass centring, or anomalous channel amplitudes due to, for example, imperfect gain. Thorough data quality control should represent an integral constituent of seismic data recording, preprocessing, and archiving, especially for data from temporary stations in passive seismic experiments. Large international seismic experiments require enormous efforts from scientists from different countries and institutions to gather hundreds of stations to be deployed in the field during a limited time period. In this paper, we demonstrate the beneficial effects of the procedures we have developed for acquiring a reliable large set of high-quality data from each group participating in field experiments. The presented tools can be applied manually or automatically on data from any seismic network.

Multi-Parameter GEOSCOPE Land Stations and Ocean Bottom Observatories

NASA Astrophysics Data System (ADS)

Stutzmann, E.; Roult, G.; Montagner, J.; Karczewski, J.; Geoscope Group,.

2002-12-01

Since the mid-eighties, the number of high quality broadband stations installed over the world has increased in a spectacular way and these stations cover now most of the emerged lands, with a higher concentration in the northern hemisphere between the latitudes 0 and 60N. The GEOSCOPE program has been the first global network of 3-component broadband seismic stations and has contributed to the elaboration of the FDSN. The 25 broadband GEOSCOPE stations fulfill the FDSN criteria, the data are stored in data-centers at the IPGP and IRIS DMC and are accessible through the netdc procedure (email to netdc@ipgp.jussieu.fr) or via the web. GEOSCOPE data have contributed to the major progresses of our knowledge of the earth interior. The earthquake CMT are now determined in a routine manner and the temporal history of the seismic source is accessible for the largest earthquakes. The geographical distribution of GEOSCOPE stations, specially in the southern hemisphere, has also played an important role in improving the resolution of global tomographic models. Recent P-wave models give high resolution images of subducted slabs whereas recent S-wave models have enable to discover the two super-swells. The evolution of the GEOSCOPE program is now focused on the installation of multi-parameter stations including 3-component broadband seismic sensors, pressure gauge, thermometer and GPS receivers. These stations will enable to decrease the seismic noise, and -among others- to better characterize the background free oscillations of the earth. The seismic station earth coverage is limited by the presence of oceans and the next step is the installation of ocean bottom broadband stations. For this purpose, in 1992, a first temporary station sismobs/OFM has been working for 2 weeks, along the mid atlantic ridge. In 1997, an international multi-parameter station, MOISE has been operating during 3 months in the Monterey Bay. The further step is the installation of the station NERO in a

The LUSI Seismic Experiment: Deployment of a Seismic Network around LUSI, East Java, Indonesia

NASA Astrophysics Data System (ADS)

Karyono, Karyono; Mazzini, Adriano; Lupi, Matteo; Syafri, Ildrem; Haryanto, Iyan; Masturyono, Masturyono; Hadi, Soffian; Rohadi, Suprianto; Suardi, Iman; Rudiyanto, Ariska; Pranata, Bayu

2015-04-01

The spectacular Lusi eruption started in northeast Java, Indonesia the 29 of May 2006 following a M6.3 earthquake striking the island. Initially, several gas and mud eruption sites appeared along the reactivated strike-slip Watukosek fault system and within weeks several villages were submerged by boiling mud. The most prominent eruption site was named Lusi. Lusi is located few kilometres to the NE of the Arjuno-Welirang volcanic complex. Lusi sits upon the Watukosek fault system. From this volcanic complex originates the Watukosek fault system that was reactivated by the M6.3 earthquake in 2006 and is still periodically reactivated by the frequent seismicity. To date Lusi is still active and erupting gas, water, mud and clasts. Gas and water data show that the Lusi plumbing system is connected with the neighbouring Arjuno-Welirang volcanic complex. This makes the Lusi eruption a "sedimentary hosted geothermal system". To verify and characterise the occurrence of seismic activity and how this perturbs the connected Watukosek fault, the Arjuno-Welirang volcanic system and the ongoing Lusi eruption, we deployed 30 seismic stations (short-period and broadband) in this region of the East Java basin. The seismic stations are more densely distributed around LUSI and the Watukosek fault zone that stretches between Lusi and the Arjuno Welirang (AW) complex. Fewer stations are positioned around the volcanic arc. Our study sheds light on the seismic activity along the Watukosek fault system and describes the waveforms associated to the geysering activity of Lusi. The initial network aims to locate small event that may not be captured by the Indonesian Agency for Meteorology, Climatology and Geophysics (BMKG) seismic network and it will be crucial to design the second phase of the seismic experiment that will consist of a local earthquake tomography of the Lusi-Arjuno Welirang region and temporal variations of vp/vs ratios. Such variations will then be ideally related to

Seismic monitoring at Deception Island volcano (Antarctica): Recent advances

NASA Astrophysics Data System (ADS)

Carmona, E.; Almendros, J.; Martín, R.; Cortés, G.; Alguacil, G.; Moreno, J.; Martín, B.; Martos, A.; Serrano, I.; Stich, D.; Ibáñez, J. M.

2012-04-01

Deception Island (South Shetland Island, Antarctica) is an active volcano with recent eruptions (e.g. 1967, 1969 and 1970). It is also among the Antarctic sites most visited by tourists. Besides, there are currently two scientific bases operating during the austral summers, usually from late November to early March. For these reasons it is necessary to deploy a volcano monitoring system as complete as possible, designed specifically to endure the extreme conditions of the volcanic environment and the Antarctic climate. The Instituto Andaluz de Geofísica of University of Granada, Spain (IAG-UGR) performs seismic monitoring on Deception Island since 1994 during austral summer surveys. The seismicity basically includes volcano-tectonic earthquakes, long-period events and volcanic tremor, among other signals. The level of seismicity is moderate, except for a seismo-volcanic crisis in 1999. The seismic monitoring system has evolved during these years, following the trends of the technological developments and software improvements. Recent advances have been mainly focused on: (1) the improvement of the seismic network introducing broadband stations and 24-bit data acquisition systems; (2) the development of a short-period seismic array, with a 12-channel, 24-bit data acquisition system; (3) the implementation of wireless data transmission from the network stations and also from the seismic array to a recording center, allowing for real-time monitoring; (4) the efficiency of the power supply systems and the monitoring of the battery levels and power consumption; (5) the optimization of data analysis procedures, including database management, automated event recognition tools for the identification and classification of seismo-volcanic signals, and apparent slowness vector estimates using seismic array data; (6) the deployment of permanent seismic stations and the transmission of data during the winter using a satellite connection. A single permanent station is operating

A permanent seismic station beneath the Ocean Bottom

NASA Astrophysics Data System (ADS)

Harris, David; Cessaro, Robert K.; Duennebier, Fred K.; Byrne, David A.

1987-03-01

The Hawaii Institute of Geophysics began development of the Ocean Subbottom Seisometer (OSS) system in 1978, and OSS systems were installed in four locations between 1979 and 1982. The OSS system is a permanent, deep ocean borehole seismic recording system composed of a borehole sensor package (tool), an electromechanical cable, recorder package, and recovery system. Installed near the bottom of a borehole (drilled by the D/V Glomar Challenger), the tool contains three orthogonal, 4.5-Hz geophones, two orthogonal tilt meters; and a temperature sensor. Signals from these sensors are multiplexed, digitized (with a floating point technique), and telemetered through approximately 10 km of electromechanical cable to a recorder package located near the ocean bottom. Electrical power for the tool is supplied from the recorder package. The digital seismic signals are demultiplexed, converted back to analog form, processed through an automatic gain control (AGC) circuit, and recorded along with a time code on magnetic tape cassettes in the recorder package. Data may be recorded continuously for up to two months in the self-contained recorder package. Data may also be recorded in real time (digital formal) during the installation and subsequent recorder package servicing. The recorder package is connected to a submerged recovery buoy by a length of bouyant polypropylene rope. The anchor on the recovery buoy is released by activating either of the acoustical command releases. The polypropylene rope may also be seized with a grappling hook to effect recovery. The recorder package may be repeatedly serviced as long as the tool remains functional A wide range of data has been recovered from the OSS system. Recovered analog records include signals from natural seismic sources such as earthquakes (teleseismic and local), man-made seismic sources such as refraction seismic shooting (explosives and air cannons), and nuclear tests. Lengthy continuous recording has permitted analysis

The 2014 update to the National Seismic Hazard Model in California

USGS Publications Warehouse

Powers, Peter; Field, Edward H.

2015-01-01

The 2014 update to the U. S. Geological Survey National Seismic Hazard Model in California introduces a new earthquake rate model and new ground motion models (GMMs) that give rise to numerous changes to seismic hazard throughout the state. The updated earthquake rate model is the third version of the Uniform California Earthquake Rupture Forecast (UCERF3), wherein the rates of all ruptures are determined via a self-consistent inverse methodology. This approach accommodates multifault ruptures and reduces the overprediction of moderate earthquake rates exhibited by the previous model (UCERF2). UCERF3 introduces new faults, changes to slip or moment rates on existing faults, and adaptively smoothed gridded seismicity source models, all of which contribute to significant changes in hazard. New GMMs increase ground motion near large strike-slip faults and reduce hazard over dip-slip faults. The addition of very large strike-slip ruptures and decreased reverse fault rupture rates in UCERF3 further enhances these effects.

Systematic Site Characterization at Seismic Stations combined with Empirical Spectral Modeling: critical data for local hazard analysis

NASA Astrophysics Data System (ADS)

Michel, Clotaire; Hobiger, Manuel; Edwards, Benjamin; Poggi, Valerio; Burjanek, Jan; Cauzzi, Carlo; Kästli, Philipp; Fäh, Donat

2016-04-01

The Swiss Seismological Service operates one of the densest national seismic networks in the world, still rapidly expanding (see http://www.seismo.ethz.ch/monitor/index_EN). Since 2009, every newly instrumented site is characterized following an established procedure to derive realistic 1D VS velocity profiles. In addition, empirical Fourier spectral modeling is performed on the whole network for each recorded event with sufficient signal-to-noise ratio. Besides the source characteristics of the earthquakes, statistical real time analyses of the residuals of the spectral modeling provide a seamlessly updated amplification function w.r. to Swiss rock conditions at every station. Our site characterization procedure is mainly based on the analysis of surface waves from passive experiments and includes cross-checks of the derived amplification functions with those obtained through spectral modeling. The systematic use of three component surface-wave analysis, allowing the derivation of both Rayleigh and Love waves dispersion curves, also contributes to the improved quality of the retrieved profiles. The results of site characterisation activities at recently installed strong-motion stations depict the large variety of possible effects of surface geology on ground motion in the Alpine context. Such effects range from de-amplification at hard-rock sites to amplification up to a factor of 15 in lacustrine sediments with respect to the Swiss reference rock velocity model. The derived velocity profiles are shown to reproduce observed amplification functions from empirical spectral modeling. Although many sites are found to exhibit 1D behavior, our procedure allows the detection and qualification of 2D and 3D effects. All data collected during the site characterization procedures in the last 20 years are gathered in a database, implementing a data model proposed for community use at the European scale through NERA and EPOS (www.epos-eu.org). A web stationbook derived from it

The Seismic component of the IBERARRAY: Placing constraints on the Lithosphere and Mantle.

NASA Astrophysics Data System (ADS)

Carbonell, R.; Diaz, J.; Villaseñor, A.; Gallart, J.; Morales, J.; Pazos, A.; Cordoba, D.; Pulgar, J.; Garcia-Lobon, J.; Harnafi, M.

2008-12-01

TOPOIBERIA, is a multidisciplinary large scale research project which aims to study the links between the deep and superficial processes within the Iberian Peninsula.One of its main experimental components is the deployment of the IBERARRAY seismic network. This is a dense array (60x60 km) of new generation dataloggers equipped with broad-band seismometers which will cover Iberia and North Morocco in three successive deployments, each lasting for about 18 months. The first leg, deployed since late 2007, covers the southern part of Iberia (35 stations) and northern Morocco (20 stations). Two data centers have been established one at the CSIC-Institute of Earth Sciences (CSIC-Barcelona) and a second at the Geologic and Mining Insititute (IGME-Madrid) the data follows a standard-conventional flow from recovery to archival. The field teams collect the recorded hard disk on the field and send data and metadata to a processing center, where raw data is collected and stored and a quality control checking is performed. This include a systematic inspection of the experimental parameters (batteries charge, thermal insulation, time adjustments, geophone leveling etc), the visual verification of the seismic waveforms and the analysis, using power density spectra (PSD), of the noise level of each station. All this information is disseminated between the research teams involved in the project using a dedicated website and the continuous seismic data is made accessible through FTP and CWQ servers. Some of the nodes of the theoretical network are covered by permanent stations of the national broad-band network (IGN) or other networks operating in the region (IAG-UGR, ROA). Data from those stations will also be integrated to the Iberarray database. This Iberarray network will provide a large database of both waveform and catalogued events, with an unprecedented resolution. Earthquake data at local, regional and teleseismic scales will be analyzed using different methodologies. The

Regional seismic lines reprocessed using post-stack processing techniques; National Petroleum Reserve, Alaska

USGS Publications Warehouse

Miller, John J.; Agena, W.F.; Lee, M.W.; Zihlman, F.N.; Grow, J.A.; Taylor, D.J.; Killgore, Michele; Oliver, H.L.

2000-01-01

This CD-ROM contains stacked, migrated, 2-Dimensional seismic reflection data and associated support information for 22 regional seismic lines (3,470 line-miles) recorded in the National Petroleum Reserve ? Alaska (NPRA) from 1974 through 1981. Together, these lines constitute about one-quarter of the seismic data collected as part of the Federal Government?s program to evaluate the petroleum potential of the Reserve. The regional lines, which form a grid covering the entire NPRA, were created by combining various individual lines recorded in different years using different recording parameters. These data were reprocessed by the USGS using modern, post-stack processing techniques, to create a data set suitable for interpretation on interactive seismic interpretation computer workstations. Reprocessing was done in support of ongoing petroleum resource studies by the USGS Energy Program. The CD-ROM contains the following files: 1) 22 files containing the digital seismic data in standard, SEG-Y format; 2) 1 file containing navigation data for the 22 lines in standard SEG-P1 format; 3) 22 small scale graphic images of each seismic line in Adobe Acrobat? PDF format; 4) a graphic image of the location map, generated from the navigation file, with hyperlinks to the graphic images of the seismic lines; 5) an ASCII text file with cross-reference information for relating the sequential trace numbers on each regional line to the line number and shotpoint number of the original component lines; and 6) an explanation of the processing used to create the final seismic sections (this document). The SEG-Y format seismic files and SEG-P1 format navigation file contain all the information necessary for loading the data onto a seismic interpretation workstation.

Updated Tomographic Seismic Imaging at Kilauea Volcano, Hawaii

NASA Astrophysics Data System (ADS)

Okubo, P.; Johnson, J.; Felts, E. S.; Flores, N.

2013-12-01

Improved and more detailed geophysical, geological, and geochemical observations and measurements at Kilauea, along with prolonged eruptions at its summit caldera and east rift zone, are encouraging more ambitious interpretation and modeling of volcanic processes over a range of temporal and spatial scales. We are updating three-dimensional models of seismic wave-speed distributions within Kilauea using local earthquake arrival time tomography to support waveform-based modeling of seismic source mechanisms. We start from a tomographic model derived from a combination of permanent seismic stations comprising the Hawaiian Volcano Observatory (HVO) seismographic network and a dense deployment of temporary stations in the Kilauea caldera region in 1996. Using P- and S-wave arrival times measured from the HVO network for local earthquakes from 1997 through 2012, we compute velocity models with the finite difference tomographic seismic imaging technique implemented by Benz and others (1996), and applied to numerous volcanoes including Kilauea. Particular impetus to our current modeling was derived from a focused effort to review seismicity occurring in Kilauea's summit caldera and adjoining regions in 2012. Our results reveal clear P-wave low-velocity features at and slightly below sea level beneath Kilauea's summit caldera, lying between Halemaumau Crater and the north-facing scarps that mark the southern caldera boundary. The results are also suggestive of changes in seismic velocity distributions between 1996 and 2012. One example of such a change is an apparent decrease in the size and southeastward extent, compared to the earlier model, of the low VP feature imaged with the more recent data. However, we recognize the distinct possibility that these changes are reflective of differences in earthquake and seismic station distributions in the respective datasets, and we need to further populate the more recent HVO seismicity catalogs to possibly address this concern

Single-station 6C beamforming

NASA Astrophysics Data System (ADS)

Nakata, N.; Hadziioannou, C.; Igel, H.

2017-12-01

Six-component measurements of seismic ground motion provide a unique opportunity to identify and decompose seismic wavefields into different wave types and incoming azimuths, as well as estimate structural information (e.g., phase velocity). By using the relationship between the transverse component and vertical rotational motion for Love waves, we can find the incident azimuth of the wave and the phase velocity. Therefore, when we scan the entire range of azimuth and slownesses, we can process the seismic waves in a similar way to conventional beamforming processing, without using a station array. To further improve the beam resolution, we use the distribution of amplitude ratio between translational and rotational motions at each time sample. With this beamforming, we decompose multiple incoming waves by azimuth and phase velocity using only one station. We demonstrate this technique using the data observed at Wettzell (vertical rotational motion and 3C translational motions). The beamforming results are encouraging to extract phase velocity at the location of the station, apply to oceanic microseism, and to identify complicated SH wave arrivals. We also discuss single-station beamforming using other components (vertical translational and horizontal rotational components). For future work, we need to understand the resolution limit of this technique, suitable length of time windows, and sensitivity to weak motion.

Crustal Structure Beneath the Gulf of ST. Lawrence, Atlantic Canada, from Ambient Seismic Noise Tomography

NASA Astrophysics Data System (ADS)

Kuponiyi, A.; Kao, H.; Cassidy, J. F.; Spence, G.

2013-12-01

The Gulf of St. Lawrence (GSL), located north of the southwest-northeast trending Appalachian mountain in eastern Canada, is a major sedimentary basin with huge potentials for hydrocarbon accumulation. Important questions about the geometry and evolution of the crustal and basin structure beneath the gulf are yet to be answered. To address these issues, the Geological Survey of Canada (GSC) with support from the Portable Observatories for Lithospheric Analysis and Research Investigating Seismicity (POLARIS) deployed a temporary array of broadband seismic stations in the GSL region between October 2005 and October 2008. Combined with the permanent stations of the Canadian National Seismograph Network (CNSN) in the region, the station density is sufficient for detailed seismic tomography inversion. In this study, we investigate the upper crustal structure beneath the gulf using 3 years of continuous ambient noise waveforms recorded at 25 (POLARIS and CNSN) stations around the GSL. Cross-correlation functions of the vertical component of the ambient noise wavefield for simultaneously recording station pairs (corresponding to inter-station Green's functions) are computed and analyzed using the frequency-time analysis method. Dispersion curves are measured and Rayleigh wave group velocities are subsequently extracted for periods between 2 and 20s, which are periods sensitive to the upper crustal structures. Preliminary results from the dispersion measurements indicate that mean group velocities in the region range from 2.8 to 3.2 km/s across the range of period specified. 2-D group velocity distribution for each period is determined by linearized inversion of the dispersion data. Our tomography results show prominent lateral velocity variation. Low velocity anomalies are observed at shorter periods (up to ~10 s) which correspond to the sedimentary structures at shallow depths (between 5-10 km), whereas the characteristics of upper crustal structures are shown by

Characteristics of seismic waves from Soviet peaceful nuclear explosions in salt

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adushkin, V.V.; Kaazik, P.B.; Kostyuchenko, V.N.

1995-04-01

The report is carried out by the Institute for Dynamics of the Geospheres, Russian Academy of Sciences under contract NB280344 with Lawrence Livermore National Laboratory, University of California. The work includes investigation of seismic waves generation and propagation from Soviet peaceful underground nuclear explosions in salt based on the data from temporary and permanent seismic stations. The explosions were conducted at the sites Azgir and Vega within the territory of the Caspian depression of the Russian platform. The data used were obtained in the following conditions of conduction: epicentral distance range from 0 to 60 degrees, yields from 1 tomore » 65 kt and depths of burial from 160 to 1500 m.« less

Specification goals for a Mars seismic network

NASA Technical Reports Server (NTRS)

Davis, Paul M.

1990-01-01

A seismic network on Mars should have enough stations (e.g., 24) to characterize the seismicity of the planet for comparison with a diversity of structural features; be comprised of low noise stations, preferably underground, 3 to 4 orders of magnitude more sensitive than those used on Viking; record over a sufficient band-width (DC-30 Hz) to detect micro-earthquakes to normal modes; and record for a sufficient duration (10 years) and data rate (10(exp 8) Mb/day/station) to obtain a data set comparable to that from the Apollo mission to the Moon so that locations of major internal boundaries can be inferred, such as those in the Earth, i.e., crust - lithosphere - asthenosphere - upper - lower phase transitions - outer - inner core. The proposed Mars Global Network Mission provides an opportunity to sense the dynamics and probe the interior of the planet. The seismic objectives, the availability of the instrumentation and trade-offs to meet them are discussed.

Seismic Tomography and the Development of a State Velocity Profile

NASA Astrophysics Data System (ADS)

Marsh, S. J.; Nakata, N.

2017-12-01

Earthquakes have been a growing concern in the State of Oklahoma in the last few years and as a result, accurate earthquake location is of utmost importance. This means using a high resolution velocity model with both lateral and vertical variations. Velocity data is determined using ambient noise seismic interferometry and tomography. Passive seismic data was acquired from multiple IRIS networks over the span of eight years (2009-2016) and filtered for earthquake removal to obtain the background ambient noise profile for the state. Seismic Interferometry is applied to simulate ray paths between stations, this is done with each possible station pair for highest resolution. Finally the method of seismic tomography is used to extract the velocity data and develop the state velocity map. The final velocity profile will be a compilation of different network analyses due to changing station availability from year to year. North-Central Oklahoma has a dense seismic network and has been operating for the past few years. The seismic stations are located here because this is the most seismically active region. Other parts of the state have not had consistent coverage from year to year, and as such a reliable and high resolution velocity profile cannot be determined from this network. However, the Transportable Array (TA) passed through Oklahoma in 2014 and provided a much wider and evenly spaced coverage. The goal of this study is to ultimately combine these two arrays over time, and provide a high quality velocity profile for the State of Oklahoma.

Seismic Readings from the Deepest Borehole in the New Madrid Seismic Zone

DOE Office of Scientific and Technical Information (OSTI.GOV)

Woolery, Edward W; Wang, Zhenming; Sturchio, Neil C

2006-03-01

Since the 1980s, the research associated with the UK network has been primarily strong-motion seismology of engineering interest. Currently the University of Kentucky operates a strong-motion network of nine stations in the New Madrid Seismic Zone. A unique feature of the network is the inclusions of vertical strong-motion arrays, each with one or two downhole accelerometers. The deepest borehole array is 260 m below the surfaces at station VASA in Fulton County, Kentucky. A preliminary surface seismic refraction survey was conducted at the site before drilling the hole at VSAS (Woolery and Wang, 2002). The depth to the Paleozoic bedrockmore » at the site was estimated to be approximately 595 m, and the depth to the first very stiff layer (i.e. Porters Creek Clay) was found to be about 260 m. These depths and stratigraphic interpretation correlated well with a proprietary seismic reflection line and the Ken-Ten Oil Exploration No. 1 Sanger hole (Schwalb, 1969), as well as our experience in the area (Street et al., 1995; Woolery et al., 1999).« less

Site classification for National Strong Motion Observation Network System (NSMONS) stations in China using an empirical H/V spectral ratio method

NASA Astrophysics Data System (ADS)

Ji, Kun; Ren, Yefei; Wen, Ruizhi

2017-10-01

Reliable site classification of the stations of the China National Strong Motion Observation Network System (NSMONS) has not yet been assigned because of lacking borehole data. This study used an empirical horizontal-to-vertical (H/V) spectral ratio (hereafter, HVSR) site classification method to overcome this problem. First, according to their borehole data, stations selected from KiK-net in Japan were individually assigned a site class (CL-I, CL-II, or CL-III), which is defined in the Chinese seismic code. Then, the mean HVSR curve for each site class was computed using strong motion recordings captured during the period 1996-2012. These curves were compared with those proposed by Zhao et al. (2006a) for four types of site classes (SC-I, SC-II, SC-III, and SC-IV) defined in the Japanese seismic code (JRA, 1980). It was found that an approximate range of the predominant period Tg could be identified by the predominant peak of the HVSR curve for the CL-I and SC-I sites, CL-II and SC-II sites, and CL-III and SC-III + SC-IV sites. Second, an empirical site classification method was proposed based on comprehensive consideration of peak period, amplitude, and shape of the HVSR curve. The selected stations from KiK-net were classified using the proposed method. The results showed that the success rates of the proposed method in identifying CL-I, CL-II, and CL-III sites were 63%, 64%, and 58% respectively. Finally, the HVSRs of 178 NSMONS stations were computed based on recordings from 2007 to 2015 and the sites classified using the proposed method. The mean HVSR curves were re-calculated for three site classes and compared with those from KiK-net data. It was found that both the peak period and the amplitude were similar for the mean HVSR curves derived from NSMONS classification results and KiK-net borehole data, implying the effectiveness of the proposed method in identifying different site classes. The classification results have good agreement with site classes

Puerto Rico Strong Motion Seismic Network

NASA Astrophysics Data System (ADS)

Huerta-Lopez, C. I.; Martínez-Cruzado, J. A.; Martínez-Pagan, J.; Santana-Torres, E. X.; Torres-O, D. M.

2014-12-01

The Puerto Rico Strong Motion Seismic Network is currently in charge of the operation of: (i) free-field (ff) strong motion stations, (ii) instrumented structures (STR) (Dams, Bridges, Buildings), and (iii) the data acquisition/monitoring and analysis of earthquakes considered strong from the point of view of their intensity and magnitude. All these instruments are deployed in the Puerto Rico Island (PRI), US-, and British-Virgin Islands (BVI), and Dominican Republic (DR). The Puerto Rico Island and the Caribbean region have high potential to be affected by earthquakes that could be catastrophic for the area. The Puerto Rico Strong Motion Seismic Network (actually Puerto Rico Strong Motion Program, PRSMP) has grown since 1970's from 7 ff strong motion stations and one instrumented building with analog accelerographs to 111 ff strong motion stations and 16 instrumented buildings with digital accelerographs: PRI: 88 ff, 16 STR., DR: 13 ff, BVI: 5 ff, 2 STR collecting data via IP (internet), DU (telephone), and stand alone stations The current stage of the PRSMP seismic network, the analysis of moderate earthquakes that were recorded and/or occurred on the island, results of the intensity distribution of selected earthquakes, as well as results of dynamic parameter identification of some of the instrumented structures are here presented.

Analysis of the seismicity in the region of Mirovo salt mine after 8 years monitoring

NASA Astrophysics Data System (ADS)

Dimitrova, Liliya; Solakov, Dimcho; Simeonova, Stela; Aleksandrova, Irena; Georgieva, Gergana

2015-04-01

Mirovo salt deposit is situated in the NE part of Bulgaria and 5 kilometers away from the town of Provadiya. The mine is in operation since 1956. The salt is produced by dilution and extraction of the brine to the surface. A system of chambers-pillars is formed within the salt body as a result of the applied technology. The mine is situated in a seismically quiet part of the state. The region is characterized with complex geological structure and several faults. During the last 3 decades a large number of small and moderate earthquakes (M<4.5) are realized in the close vicinity of the salt deposit. Local seismological network (LSN) is deployed in the region to monitor the local seismicity. It consists of 6 three component digital stations. A real-time data transfer from LSN stations to National Data Center (in Sofia) is implemented using the VPN and MAN networks of the Bulgarian Telecommunication Company. Common processing and interpretation of the data from LSN and the national seismic network is performed. Real-time and interactive data processing are performed by the Seismic Network Data Processor (SNDP) software package. More than 700 earthquakes are registered by the LSN within 30km region around the mine during the 8 years monitoring. First we processed the data and compile a catalogue of the earthquakes occur within the studied region (30km around the salt mine). Spatial pattern of seismicity is analyzed. A large number of the seismic events occurred within the northern and north-western part of the salt body. Several earthquakes occurred in close vicinity of the mine. Concerning that the earthquakes could be tectonic and/or induced an attempt is made to find criteria to distinguish natural from induced seismicity. To characterize and distinguish the main processes active in the area we also made waveform and spectral analysis of a number of earthquakes.

Seismic evidence for multiple-stage exhumation of high/ultrahigh pressure metamorphic rocks in the eastern Dabie orogenic belt

NASA Astrophysics Data System (ADS)

Luo, Yinhe; Zhao, Kaifeng; Tang, Chi-Chia; Xu, Yixian

2018-05-01

The Dabie-Sulu orogenic belt in China contains one of the largest exposures of high and ultrahigh pressure (HP and UHP) metamorphic rocks in the world. The origin of HP/UHP metamorphic rocks and their exhumation to the surface in this belt have attracted great interest in the geologic community because the study of exhumation history of HP/UHP rocks helps to understand the process of continental-continental collision and the tectonic evolution of post-collision. However, the exhumation mechanism of the HP-UHP rocks to the surface is still contentious. In this study, by deploying 28 broadband seismic stations in the eastern Dabie orogenic belt and combining seismic data from 40 stations of the China National Seismic Network (CNSN), we image the high-resolution crustal isotropic shear velocity and radial anisotropy structure using ambient noise tomography. Our high-resolution 3D models provide new information about the exhumation mechanism of HP/UHP rocks and the origin of two dome structures.

Seismic activity in northeastern Brazill-new perspectives

NASA Astrophysics Data System (ADS)

Ferreira, J. M.; Do Nascimento, A. F.; Vilar, C. S.; Bezerra, F. H.; Assumpcao, M.; Berrocal, J.; Fuck, R. A.

2007-05-01

Northeastern Brazil is the most seismic active region in the country. Some earthquakes with magnitude above 5.0 and intensity VII MM associated with swam-like seismic activity lasting for many years are a serious social concern. Since the 1980's macroseismic and instrumental surveys have been carried out in this region and they are an important data archive which allows the composition of a reliable catalogue of seismic activity for this region. Among the many scientific results it was possible to identify the main seismogenic areas, obtain reliable hypocentres and focal mechanisms. As a consequence, it was possible also to analyse the relationship between seismicity and geological features. It was also possible to determined maximum horizontal stress direction for the region. An important induced seismic activity case has also been reported in the area as being a classical example of pore pressure diffusion triggering mechanism. The majority of the results were obtained using analogic data. Recently, a new research project is being conducted and will allow us to provide a regional scale monitoring with 6 broad-band stations and a new portable six station digital seismic network equipped with short- period sensors. Thus, with the continuous seismic activity in the area we trust that the results of this project will increase the present knowledge of seismic activity in northeastern Brazil.

Technical guidelines for the implementation of the Advanced National Seismic System

USGS Publications Warehouse

Committee, ANSS Technical Integration

2002-01-01

The Advanced National Seismic System (ANSS) is a major national initiative led by the US Geological Survey that serves the needs of the earthquake monitoring, engineering, and research communities as well as national, state, and local governments, emergency response organizations, and the general public. Legislation authorizing the ANSS was passed in 2000, and low levels of funding for planning and initial purchases of new seismic instrumentation have been appropriated beginning in FY2000. When fully operational, the ANSS will be an advanced monitoring system (modern digital seismographs and accelerographs, communications networks, data collection and processing centers, and well-trained personnel) distributed across the United States that operates with high performance standards, gathers critical technical data, and effectively provides timely and reliable earthquake products, information, and services to meet the Nation’s needs. The ANSS will automatically broadcast timely and authoritative products describing the occurrence of earthquakes, earthquake source properties, the distribution of ground shaking, and, where feasible, broadcast early warnings and alerts for the onset of strong ground shaking. Most importantly, the ANSS will provide earthquake data, derived products, and information to the public, emergency responders, officials, engineers, educators, researchers, and other ANSS partners rapidly and in forms that are useful for their needs.

Seismic Ecology

NASA Astrophysics Data System (ADS)

Seleznev, V. S.; Soloviev, V. M.; Emanov, A. F.

The paper is devoted to researches of influence of seismic actions for industrial and civil buildings and people. The seismic actions bring influence directly on the people (vibration actions, force shocks at earthquakes) or indirectly through various build- ings and the constructions and can be strong (be felt by people) and weak (be fixed by sensing devices). The great number of work is devoted to influence of violent seismic actions (first of all of earthquakes) on people and various constructions. This work is devoted to study weak, but long seismic actions on various buildings and people. There is a need to take into account seismic oscillations, acting on the territory, at construction of various buildings on urbanized territories. Essential influence, except for violent earthquakes, man-caused seismic actions: the explosions, seismic noise, emitted by plant facilities and moving transport, radiation from high-rise buildings and constructions under action of a wind, etc. can exert. Materials on increase of man- caused seismicity in a number of regions in Russia, which earlier were not seismic, are presented in the paper. Along with maps of seismic microzoning maps to be built indicating a variation of amplitude spectra of seismic noise within day, months, years. The presence of an information about amplitudes and frequencies of oscillations from possible earthquakes and man-caused oscillations in concrete regions allows carry- ing out soundly designing and construction of industrial and civil housing projects. The construction of buildings even in not seismically dangerous regions, which have one from resonance frequencies coincident on magnitude to frequency of oscillations, emitted in this place by man-caused objects, can end in failure of these buildings and heaviest consequences for the people. The practical examples of detail of engineering- seismological investigation of large industrial and civil housing projects of Siberia territory (hydro power

Combining Real-time Seismic and Geodetic Data to Improve Rapid Earthquake Information

NASA Astrophysics Data System (ADS)

Murray, M. H.; Neuhauser, D. S.; Gee, L. S.; Dreger, D. S.; Basset, A.; Romanowicz, B.

2002-12-01

The Berkeley Seismological Laboratory operates seismic and geodetic stations in the San Francisco Bay area and northern California for earthquake and deformation monitoring. The seismic systems, part of the Berkeley Digital Seismic Network (BDSN), include strong motion and broadband sensors, and 24-bit dataloggers. The data from 20 GPS stations, part of the Bay Area Regional Deformation (BARD) network of more than 70 stations in northern California, are acquired in real-time. We have developed methods to acquire GPS data at 12 stations that are collocated with the seismic systems using the seismic dataloggers, which have large on-site data buffer and storage capabilities, merge it with the seismic data stream in MiniSeed format, and continuously stream both data types using reliable frame relay and/or radio modem telemetry. Currently, the seismic data are incorporated into the Rapid Earthquake Data Integration (REDI) project to provide notification of earthquake magnitude, location, moment tensor, and strong motion information for hazard mitigation and emergency response activities. The geodetic measurements can provide complementary constraints on earthquake faulting, including the location and extent of the rupture plane, unambiguous resolution of the nodal plane, and distribution of slip on the fault plane, which can be used, for example, to refine strong motion shake maps. We are developing methods to rapidly process the geodetic data to monitor transient deformation, such as coseismic station displacements, and for combining this information with the seismic observations to improve finite-fault characterization of large earthquakes. The GPS data are currently processed at hourly intervals with 2-cm precision in horizontal position, and we are beginning a pilot project in the Bay Area in collaboration with the California Spatial Reference Center to do epoch-by-epoch processing with greater precision.

Studies of infrasound propagation using the USArray seismic network (Invited)

NASA Astrophysics Data System (ADS)

Hedlin, M. A.; Degroot-Hedlin, C. D.; Walker, K. T.

2010-12-01

Although there are currently ~ 100 infrasound arrays worldwide, more than ever before, the station density is still insufficient to provide validation for detailed propagation modeling. Much structure in the atmosphere is short-lived and occurs at spatial scales much smaller than the average distance between infrasound stations. Relatively large infrasound signals can be observed on seismic channels due to coupling at the Earth's surface. Recent research, using data from the 70-km spaced 400-station USArray and other seismic network deployments, has shown the value of dense seismic network data for filling in the gaps between infrasound arrays. The dense sampling of the infrasound wavefield has allowed us to observe complete travel-time branches of infrasound signals and shed more light on the nature of infrasound propagation. We present early results from our studies of impulsive atmospheric sources, such as series of UTTR rocket motor detonations in Utah. The Utah blasts have been well recorded by USArray seismic stations and infrasound arrays in Nevada and Washington State. Recordings of seismic signals from a series of six events in 2007 are used to pinpoint the shot times to < 1 second. Variations in the acoustic branches and signal arrival times at the arrays are used to probe variations in atmospheric structure. Although we currently use coupled signals we anticipate studying dense acoustic network recordings as the USArray is currently being upgraded with infrasound microphones. These new sensors will allow us to make semi-continental scale network recordings of infrasound signals free of concerns about how the signals observed on seismic channels were modified when being coupled to seismic.

Earthquake information products and tools from the Advanced National Seismic System (ANSS)

USGS Publications Warehouse

Wald, Lisa

2006-01-01

This Fact Sheet provides a brief description of postearthquake tools and products provided by the Advanced National Seismic System (ANSS) through the U.S. Geological Survey Earthquake Hazards Program. The focus is on products specifically aimed at providing situational awareness in the period immediately following significant earthquake events.

Towards marine seismological Network: real time small aperture seismic array

NASA Astrophysics Data System (ADS)

Ilinskiy, Dmitry

2017-04-01

Most powerful and dangerous seismic events are generated in underwater subduction zones. Existing seismological networks are based on land seismological stations. Increased demands for accuracy of location, magnitude, rupture process of coming earthquakes and at the same time reduction of data processing time require information from seabed seismic stations located near the earthquake generation area. Marine stations provide important contribution for clarification of the tectonic settings in most active subduction zones of the world. Early warning system for subduction zone area is based on marine seabed array which located near the area of most hazardous seismic zone in the region. Fast track processing for location of the earthquake hypocenter and energy takes place in buoy surface unit. Information about detected and located earthquake reaches the onshore seismological center earlier than the first break waves from the same earthquake will reach the nearest onshore seismological station. Implementation of small aperture array is based on existed and shown a good proven performance and costs effective solutions such as weather moored buoy and self-pop up autonomous seabed seismic nodes. Permanent seabed system for real-time operation has to be installed in deep sea waters far from the coast. Seabed array consists of several self-popup seismological stations which continuously acquire the data, detect the events of certain energy class and send detected event parameters to the surface buoy via acoustic link. Surface buoy unit determine the earthquake location by receiving the event parameters from seabed units and send such information in semi-real time to the onshore seismological center via narrow band satellite link. Upon the request from the cost the system could send wave form of events of certain energy class, bottom seismic station battery status and other environmental parameters. When the battery life of particular seabed unit is close to became empty

Reflection imaging of the Moon's interior using deep-moonquake seismic interferometry

NASA Astrophysics Data System (ADS)

Nishitsuji, Yohei; Rowe, C. A.; Wapenaar, Kees; Draganov, Deyan

2016-04-01

The internal structure of the Moon has been investigated over many years using a variety of seismic methods, such as travel time analysis, receiver functions, and tomography. Here we propose to apply body-wave seismic interferometry to deep moonquakes in order to retrieve zero-offset reflection responses (and thus images) beneath the Apollo stations on the nearside of the Moon from virtual sources colocated with the stations. This method is called deep-moonquake seismic interferometry (DMSI). Our results show a laterally coherent acoustic boundary around 50 km depth beneath all four Apollo stations. We interpret this boundary as the lunar seismic Moho. This depth agrees with Japan Aerospace Exploration Agency's (JAXA) SELenological and Engineering Explorer (SELENE) result and previous travel time analysis at the Apollo 12/14 sites. The deeper part of the image we obtain from DMSI shows laterally incoherent structures. Such lateral inhomogeneity we interpret as representing a zone characterized by strong scattering and constant apparent seismic velocity at our resolution scale (0.2-2.0 Hz).

South-Central Tibetan Seismicity from HiCLIMB Seismic Array Data

NASA Astrophysics Data System (ADS)

Carpenter, S.; Nabelek, J.; Braunmiller, J.

2010-12-01

The HiCLIMB broadband passive seismic experiment (2002-2005) operated 233 sites along a 800-km long north-south array extending from the Himalayan foreland into the Central Tibetan Plateau and a flanking 350x350 km lateral array in southern Tibet and eastern Nepal. We use data from the experiment’s second phase (June 2004 to August 2005), when stations operated in Tibet, to locate earthquakes in south-central Tibet, a region with no permanent seismic network where little is known about its seismicity. We used the Antelope software for automatic detection and arrival time picking, event-arrival association and event location. Requiring a low detection and event association threshold initially resulted in ~110,000 declared events. The large database size rendered manual inspection unfeasible and we developed automated post-processing modules to weed out spurious detections and erroneous phase and event associations, which stemmed, e.g., from multiple coincident earthquakes within the array or misplaced seismicity from the great 2004 Sumatra earthquake. The resulting database contains ~32,000 events within 5° distance from the closest station. We consider ~7,600 events defined by more than 30 P and S arrivals well located and discuss them here. Seismicity in the subset correlates well with mapped faults and structures seen on satellite imagery attesting to high location quality. This is confirmed by non-systematic, kilometer-scale differences between automatic and manual locations for selected events. Seismicity in south-central Tibet is intense north of the Yarlung-Tsangpo Suture. Almost 90% of events occurred in the Lhasa Terrane mainly along north-south trending rifts. Vigorous activity (>4,800 events) accompanied two M>6 earthquakes in the Payang Basin (84°E), ~100 km west of the linear array. The Tangra-Yum Co (86.5°E) and Pumqu-Xianza (88°E) rifts were very active (~1,000 events) without dominant main shocks indicating swarm like-behavior possibly related

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

Seismic source parameters of the induced seismicity at The Geysers geothermal area, California, by a generalized inversion approach

NASA Astrophysics Data System (ADS)

Picozzi, Matteo; Oth, Adrien; Parolai, Stefano; Bindi, Dino; De Landro, Grazia; Amoroso, Ortensia

2017-04-01

The accurate determination of stress drop, seismic efficiency and how source parameters scale with earthquake size is an important for seismic hazard assessment of induced seismicity. We propose an improved non-parametric, data-driven strategy suitable for monitoring induced seismicity, which combines the generalized inversion technique together with genetic algorithms. In the first step of the analysis the generalized inversion technique allows for an effective correction of waveforms for the attenuation and site contributions. Then, the retrieved source spectra are inverted by a non-linear sensitivity-driven inversion scheme that allows accurate estimation of source parameters. We therefore investigate the earthquake source characteristics of 633 induced earthquakes (ML 2-4.5) recorded at The Geysers geothermal field (California) by a dense seismic network (i.e., 32 stations of the Lawrence Berkeley National Laboratory Geysers/Calpine surface seismic network, more than 17.000 velocity records). We find for most of the events a non-selfsimilar behavior, empirical source spectra that requires ωγ source model with γ > 2 to be well fitted and small radiation efficiency ηSW. All these findings suggest different dynamic rupture processes for smaller and larger earthquakes, and that the proportion of high frequency energy radiation and the amount of energy required to overcome the friction or for the creation of new fractures surface changes with the earthquake size. Furthermore, we observe also two distinct families of events with peculiar source parameters that, in one case suggests the reactivation of deep structures linked to the regional tectonics, while in the other supports the idea of an important role of steeply dipping fault in the fluid pressure diffusion.

How a Country-Wide Seismological Network Can Improve Understanding of Seismicity and Seismic Hazard -- The Example of Bhutan

NASA Astrophysics Data System (ADS)

Hetényi, G.; Diehl, T.; Singer, J.; Kissling, E. H.; Clinton, J. F.; Wiemer, S.

2015-12-01

The Eastern Himalayas are home to a seemingly complex seismo-tectonic evolution. The rate of instrumental seismicity is lower than the average along the orogen, there is no record of large historical events, but both paleoseismology and GPS studies point to potentially large (M>8) earthquakes. Due to the lack of a permanent seismic monitoring system in the area, our current level of understanding is inappropriate to create a reliable quantitative seismic hazard model for the region. Existing maps are based on questionable hypotheses and show major inconsistencies when compared to each other. Here we present results on national and regional scales from a 38-station broadband seismological network we operated for almost 2 years in the Kingdom of Bhutan. A thorough, state-of-the-art analysis of local and regional earthquakes builds a comprehensive catalogue that reveals significantly (2-to-3 orders of magnitude) more events than detected from global networks. The seismotectonic analysis reveals new patterns of seismic activity as well as striking differences over relatively short distances within the Himalayas, only partly explained by surface observations such as geology. We compare a priori and a posteriori (BMC) magnitude of completeness maps and show that our network was able to detect all felt events during its operation. Some of these events could be felt at surprisingly large distances. Based on our experiment and experience, we draft the pillars on which a permanent seismological observatory for Bhutan could be constructed. Such a continuous monitoring system of seismic activity could then lead to a reliable quantitative seismic hazard model for Bhutan and surrounding regions, and serve as a base to improve building codes and general preparedness.

SSHAC Level 1 Probabilistic Seismic Hazard Analysis for the Idaho National Laboratory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Payne, Suzette; Coppersmith, Ryan; Coppersmith, Kevin

A Probabilistic Seismic Hazard Analysis (PSHA) was completed for the Materials and Fuels Complex (MFC), Naval Reactors Facility (NRF), and the Advanced Test Reactor (ATR) at Idaho National Laboratory (INL) (Figure 1-1). The PSHA followed the approaches and procedures appropriate for a Study Level 1 provided in the guidance advanced by the Senior Seismic Hazard Analysis Committee (SSHAC) in U.S. Nuclear Regulatory Commission (NRC) NUREG/CR-6372 and NUREG-2117 (NRC, 1997; 2012a). The SSHAC Level 1 PSHAs for MFC and ATR were conducted as part of the Seismic Risk Assessment (SRA) project (INL Project number 31287) to develop and apply a new-riskmore » informed methodology, respectively. The SSHAC Level 1 PSHA was conducted for NRF to provide guidance on the potential use of a design margin above rock hazard levels. The SRA project is developing a new risk-informed methodology that will provide a systematic approach for evaluating the need for an update of an existing PSHA. The new methodology proposes criteria to be employed at specific analysis, decision, or comparison points in its evaluation process. The first four of seven criteria address changes in inputs and results of the PSHA and are given in U.S. Department of Energy (DOE) Standard, DOE-STD-1020-2012 (DOE, 2012a) and American National Standards Institute/American Nuclear Society (ANSI/ANS) 2.29 (ANS, 2008a). The last three criteria address evaluation of quantitative hazard and risk-focused information of an existing nuclear facility. The seven criteria and decision points are applied to Seismic Design Category (SDC) 3, 4, and 5, which are defined in American Society of Civil Engineers/Structural Engineers Institute (ASCE/SEI) 43-05 (ASCE, 2005). The application of the criteria and decision points could lead to an update or could determine that such update is not necessary.« less

CRUSTAL TECTONICS AND SEISMICITY OF THE MIDDLE EAST

NASA Astrophysics Data System (ADS)

Ghalib, H. A.; Gritto, R.; Sibol, M. S.; Herrmann, R. B.; Aleqabi, G. I.; Caron, P. F.; Wagner, R. A.; Ali, B. S.; Ali, A. A.

2009-12-01

The Arabian plate describes a geological entity and a dynamic system that has been in continuous interaction with the African plate to the west and south and the Eurasian plate to the north and east. The western and southern boundaries are distinguished by see floor spreading along the Gulf of Aden and Red Sea and transform faulting along the Dead Sea, whereas the northern and eastern boundaries are portrayed by compressional suture zones under thrusting the Turkish and Iranian plateaus. Despite this favorable juxtaposition of continental land masses and the plethora of national seismic networks in every country of the Middle East, the majority of published research on the Arabian plate and surrounding tectonic blocks still depends primarily on global seismographic stations and occasional local networks. Since 2005, we deployed a number of seismic stations, and more recently a five elements array, in close proximity to the northeastern boundary of the Arabian plate. The primary objective of the effort is to better understand the regional seismicity and seismotectonics of the Arabian plate and surrounding regions. To date over a terabyte of high quality 100 sps continuous three-component broadband data have been collected and being analyzed to derive models representative of the greater Middle East tectonic setting. This goal is, in part, achieved by estimating local and regional seismic velocity models using receiver function and surface wave dispersion analyses, and by using these models to obtain accurate hypocenter locations and event focal mechanisms. The resulting events distribution reveals a distinct picture of the interaction between the seismicity and tectonics of the region. The highest seismicity rate seems to be confined to the active northern section of the Zagros thrust zone, while it decreases towards the southern end, before the intensity increases again in the Bandar Abbas region. Spatial distribution of the events and stations provide thorough

Amplification Factors for Spectral Acceleration Using Borehole Seismic Array in Taiwan

NASA Astrophysics Data System (ADS)

Lai, T. S.; Yih-Min, W.; Chao, W. A.; Chang, C. H.

2017-12-01

In order to reduce the noise from surface to get the high-quality seismic recordings, there are 54 borehole seismic arrays have been installed in Taiwan deployed by Central Weather Bureau (CWB) until the end of 2016. Each array includes two force balance accelerometers, one at the surface and other inside the borehole, as well as one broadband seismometer inside the borehole. The downhole instruments are placed at a depth between 120 and 400 m. The background noise level are lower at the borehole stations, but the amplitudes recorded by borehole stations are smaller than surface stations for the same earthquake due to the different geology conditions. Therefore, the earthquake magnitude estimated by borehole station is smaller than surface station. So far, CWB only use the surface stations in the magnitude determination due to this situation. In this study, we investigate the site effects between surface and downhole for borehole seismic arrays. Using the spectral ratio derived by the two-station spectral method as the transfer function, simulated the waveform recorded by borehole stations to the surface stations. In the future, through the transfer function, the borehole stations will be included in the estimation of earthquake magnitude and the results of amplification factors can provide the information of near-surface site effects for the ground motion simulation applications.

Seismic noise on Rarotonga: Surface versus downhole

USGS Publications Warehouse

Butler, Rhett; Hutt, C.R.

1992-01-01

Seismic noise data are presented from the new Global Seismographic Network station, RAR, on the Island of Rarotonga in the South Pacific. Data from the first new borehole site in the GSN are compared with a surface vault installation. Initial indications from the data show that borehole siting on a small island significantly reduces long-period (>20 s) horizontal seismic noise levels during the daytime, but little or no improvement is evident at periods shorter than 20 s or on the vertical component.The goal of the Incorporated Research Institutions for Seismology (IRIS) GSN program is broad, uniform coverage of the Earth with a 128-station network. To achieve this goal and provide coverage in oceanic areas, many stations will be sited on islands. A major siting consideration for these new stations is whether to build a surface vault or drill a borehole. Neither option is inexpensive. The costs for drilling a cased hole and a borehole sensor are large, but the benefit of a borehole site is that seismic noise is reduced during certain periods when a surface installation may be subject to wind, weather, and thermal effects. This benefit translates into recording greater numbers of smaller earthquakes and higher signal-to-noise ratio.

Reassessment of the Seismicity and seismic hazards of Libya

NASA Astrophysics Data System (ADS)

Ben Suleman, A.; Elmeladi, A.

2009-04-01

The tectonic evolution of Libya, located at the northern extreme of the African continent, has yielded a complex crustal structure that is composed of a series of basins and uplifts. The present day deformation of Libya is the result of the Eurasia-Africa continental collision. At the end of the year 2005, The Libyan National Seismological Network was established to monitor local, regional and teleseismic activities, as well as to provide high quality data for research projects both locally and on the regional and global scale. This study aims to discuss the seismicity of Libya by using the new data from the Libyan national seismological network and to focus on the seismic hazards. At first glance the seismic activity map shows dominant trends of seismicity with most of the seismic activity concentrated along the northern coastal areas. Four major seismic trends were quite noticeable. A first trend is a NW-SE direction coinciding with the eastern boarder of the Hun Graben. A second trend is also a NW-SE direction in the offshore area and might be a continuation of this trend. The other two trends were located in the western Gulf of Sirt and Cyrenaica platform. The rest of seismicity is diffuse either offshore or in land, with no good correlation with well-mapped faults. Detailed investigations of the Libyan seismicity indicates that the Libya has experienced earthquakes of varying magnitudes and that there is definitely a certain amount of seismic risk involved in engineering projects, particularly in the northern regions. Detailed investigation of the distribution of the Libyan earthquakes in space and time along with all other geological considerations suggested the classification of the country into four seismic zones with the Hun graben zone being the most seismically active zone.

WILBER and PyWEED: Event-based Seismic Data Request Tools

NASA Astrophysics Data System (ADS)

Falco, N.; Clark, A.; Trabant, C. M.

2017-12-01

WILBER and PyWEED are two user-friendly tools for requesting event-oriented seismic data. Both tools provide interactive maps and other controls for browsing and filtering event and station catalogs, and downloading data for selected event/station combinations, where the data window for each event/station pair may be defined relative to the arrival time of seismic waves from the event to that particular station. Both tools allow data to be previewed visually, and can download data in standard miniSEED, SAC, and other formats, complete with relevant metadata for performing instrument correction. WILBER is a web application requiring only a modern web browser. Once the user has selected an event, WILBER identifies all data available for that time period, and allows the user to select stations based on criteria such as the station's distance and orientation relative to the event. When the user has finalized their request, the data is collected and packaged on the IRIS server, and when it is ready the user is sent a link to download. PyWEED is a downloadable, cross-platform (Macintosh / Windows / Linux) application written in Python. PyWEED allows a user to select multiple events and stations, and will download data for each event/station combination selected. PyWEED is built around the ObsPy seismic toolkit, and allows direct interaction and control of the application through a Python interactive console.

Rocky Mountain Research Station 2008-2012 National Fire Plan Investments

Treesearch

Erika Gallegos

2013-01-01

This report highlights selected accomplishments by the USDA Forest Service Rocky Mountain Research Station's Wildland Fire and Fuels Research & Development projects in support of the National Fire Plan from 2008 through 2012. These projects are examples of the broad range of knowledge and tools developed by National Fire Plan funding beginning in 2008.

Passive seismic imaging based on seismic interferometry: method and its application to image the structure around the 2013 Mw6.6 Lushan earthquake

NASA Astrophysics Data System (ADS)

Gu, N.; Zhang, H.

2017-12-01

Seismic imaging of fault zones generally involves seismic velocity tomography using first arrival times or full waveforms from earthquakes occurring around the fault zones. However, in most cases seismic velocity tomography only gives smooth image of the fault zone structure. To get high-resolution structure of the fault zones, seismic migration using active seismic data needs to be used. But it is generally too expensive to conduct active seismic surveys, even for 2D. Here we propose to apply the passive seismic imaging method based on seismic interferometry to image fault zone detailed structures. Seismic interferometry generally refers to the construction of new seismic records for virtual sources and receivers by cross correlating and stacking the seismic records on physical receivers from physical sources. In this study, we utilize seismic waveforms recorded on surface seismic stations for each earthquake to construct zero-offset seismic record at each earthquake location as if there was a virtual receiver at each earthquake location. We have applied this method to image the fault zone structure around the 2013 Mw6.6 Lushan earthquake. After the occurrence of the mainshock, a 29-station temporary array is installed to monitor aftershocks. In this study, we first select aftershocks along several vertical cross sections approximately normal to the fault strike. Then we create several zero-offset seismic reflection sections by seismic interferometry with seismic waveforms from aftershocks around each section. Finally we migrate these zero-offset sections to create seismic structures around the fault zones. From these migration images, we can clearly identify strong reflectors, which correspond to major reverse fault where the mainshock occurs. This application shows that it is possible to image detailed fault zone structures with passive seismic sources.

Earthquake Source Parameter Estimates for the Charlevoix and Western Quebec Seismic Zones in Eastern Canada

NASA Astrophysics Data System (ADS)

Onwuemeka, J.; Liu, Y.; Harrington, R. M.; Peña-Castro, A. F.; Rodriguez Padilla, A. M.; Darbyshire, F. A.

2017-12-01

The Charlevoix Seismic Zone (CSZ), located in eastern Canada, experiences a high rate of intraplate earthquakes, hosting more than six M >6 events since the 17th century. The seismicity rate is similarly high in the Western Quebec seismic zone (WQSZ) where an MN 5.2 event was reported on May 17, 2013. A good understanding of seismicity and its relation to the St-Lawrence paleorift system requires information about event source properties, such as static stress drop and fault orientation (via focal mechanism solutions). In this study, we conduct a systematic estimate of event source parameters using 1) hypoDD to relocate event hypocenters, 2) spectral analysis to derive corner frequency, magnitude, and hence static stress drops, and 3) first arrival polarities to derive focal mechanism solutions of selected events. We use a combined dataset for 817 earthquakes cataloged between June 2012 and May 2017 from the Canadian National Seismograph Network (CNSN), and temporary deployments from the QM-III Earthscope FlexArray and McGill seismic networks. We first relocate 450 events using P and S-wave differential travel-times refined with waveform cross-correlation, and compute focal mechanism solutions for all events with impulsive P-wave arrivals at a minimum of 8 stations using the hybridMT moment tensor inversion algorithm. We then determine corner frequency and seismic moment values by fitting S-wave spectra on transverse components at all stations for all events. We choose the final corner frequency and moment values for each event using the median estimate at all stations. We use the corner frequency and moment estimates to calculate moment magnitudes, static stress-drop values and rupture radii, assuming a circular rupture model. We also investigate scaling relationships between parameters, directivity, and compute apparent source dimensions and source time functions of 15 M 2.4+ events from second-degree moment estimates. To the first-order, source dimension

76 FR 65752 - International Space Station (ISS) National Laboratory Advisory Committee; Charter Renewal

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-24

... NATIONAL AERONAUTICS AND SPACE ADMINISTRATION [Notice (11-104)] International Space Station (ISS) National Laboratory Advisory Committee; Charter Renewal AGENCY: National Aeronautics and Space... International and Interagency Relations, (202) 358-0550, National Aeronautics and Space Administration...

Scientific Rationale and Requirements for a Global Seismic Network on Mars

NASA Technical Reports Server (NTRS)

Solomon, Sean C.; Anderson, Don L.; Banerdt, W. Bruce; Butler, Rhett G.; Davis, Paul M.; Duennebier, Frederick K.; Nakamura, Yosio; Okal, Emile A.; Phillips, Roger J.

1991-01-01

Following a brief overview of the mission concepts for a Mars Global Network Mission as of the time of the workshop, we present the principal scientific objectives to be achieved by a Mars seismic network. We review the lessons for extraterrestrial seismology gained from experience to date on the Moon and on Mars. An important unknown on Mars is the expected rate of seismicity, but theoretical expectations and extrapolation from lunar experience both support the view that seismicity rates, wave propagation characteristics, and signal-to-noise ratios are favorable to the collection of a scientifically rich dataset during the multiyear operation of a global seismic experiment. We discuss how particular types of seismic waves will provide the most useful information to address each of the scientific objectives, and this discussion provides the basis for a strategy for station siting. Finally, we define the necessary technical requirements for the seismic stations.

SEISMIC STUDY OF THE AGUA DE PAU GEOTHERMAL PROSPECT, SAO MIGUEL, AZORES.

USGS Publications Warehouse

Dawson, Phillip B.; Rodrigues da Silva, Antonio; Iyer, H.M.; Evans, John R.

1985-01-01

A 16 station array was operated over the 200 km**2 central portion of Sao Miguel utilizing 8 permanent Instituto Nacional de Meterologia e Geofisica stations and 8 USGS portable stations. Forty four local events with well constrained solutions and 15 regional events were located. In addition, hundreds of unlocatable seismic events were recorded. The most interesting seismic activity occurred in a swarm on September 6 and 7, 1983 when over 200 events were recorded in a 16 hour period. The seismic activity around Agua de Pau was centered on the east and northeast slopes of the volcano. The data suggest a boiling hydrothermal system beneath the Agua de Pau volcano, consistent with a variety of other data.

Estimating seismic site response in Christchurch City (New Zealand) from dense low-cost aftershock arrays

USGS Publications Warehouse

Kaiser, Anna E.; Benites, Rafael A.; Chung, Angela I.; Haines, A. John; Cochran, Elizabeth S.; Fry, Bill

2011-01-01

The Mw 7.1 September 2010 Darfield earthquake, New Zealand, produced widespread damage and liquefaction ~40 km from the epicentre in Christchurch city. It was followed by the even more destructive Mw 6.2 February 2011 Christchurch aftershock directly beneath the city’s southern suburbs. Seismic data recorded during the two large events suggest that site effects contributed to the variations in ground motion observed throughout Christchurch city. We use densely-spaced aftershock recordings of the Darfield earthquake to investigate variations in local seismic site response within the Christchurch urban area. Following the Darfield main shock we deployed a temporary array of ~180 low-cost 14-bit MEMS accelerometers linked to the global Quake-Catcher Network (QCN). These instruments provided dense station coverage (spacing ~2 km) to complement existing New Zealand national network strong motion stations (GeoNet) within Christchurch city. Well-constrained standard spectral ratios were derived for GeoNet stations using a reference station on Miocene basalt rock in the south of the city. For noisier QCN stations, the method was adapted to find a maximum likelihood estimate of spectral ratio amplitude taking into account the variance of noise at the respective stations. Spectral ratios for QCN stations are similar to nearby GeoNet stations when the maximum likelihood method is used. Our study suggests dense low-cost accelerometer aftershock arrays can provide useful information on local-scale ground motion properties for use in microzonation. Preliminary results indicate higher amplifications north of the city centre and strong high-frequency amplification in the small, shallower basin of Heathcote Valley.

Deep seismic exploration into the Arctic Lithosphere: Arctic-2012 Russian wide-angle seismic experiment

NASA Astrophysics Data System (ADS)

Kashubin, S.

2013-12-01

Integrated geological and geophysical studies of the Earth's crust and upper mantle (the Russian project 'Arctic-2012') were carried out in 2012 in the Mendeleev Rise, central Arctic. The set of studies included wide-angle seismic observations along the line crossing the Mendeleev Rise in its southern part. The DSS seismic survey was aimed at the determination of the Mendeleev Rise crust type. A high-power air gun (120 liters or 7320 cu.in) and ocean stations with multi-component recording (X, Y, Z geophone components and a hydrophone) were used for the DSS. The line was studied using a dense system of observation: bottom station spacing was from 10 to 20 km, excitation point spacing (seismic traces interval) was 315 m. Observation data were obtained in 27 location points of bottom stations, the distance between the first and the last stations was 480 km, the length of the excitation line was 740 km. In DSS wave fields, in the first and later arrivals, there are refracted and reflected waves associated with boundaries in the sedimentary cover, with the top of the basement, and with boundaries in the consolidated crust, including its bottom (Moho discontinuity). The waves could be traced for offsets up to 170-240 km. The DSS line coincides with the near-vertical CMP line worked out with the use of a 4500-m-long seismic streamer and with a 50 m shot point interval that allowed essential detalization of the upper part of the section and taking it into account in the construction of a deep crust model. The deep velocity model was constructed using ray-trace modeling of compressional, shear, and converted waves with the use of the SeisWide program. Estimates were obtained for Vp/Vs velocity ratios, which played an important role in determining the type of crust. The results of the interpretation show that the Mendeleev Rise section corresponds to sections of a thin continental crust of shelf seas and a thinned continental crust of submarine ridges and rises.

The International Space Station: A National Laboratory

NASA Technical Reports Server (NTRS)

Giblin, Timothy W.

2012-01-01

After more than a decade of assembly missions and the end of the space shuttle program, the International Space Station (ISS) has reached assembly completion. With other visiting spacecraft now docking with the ISS on a regular basis, the orbiting outpost now serves as a National Laboratory to scientists back on Earth. The ISS has the ability to strengthen relationships between NASA, other Federal entities, higher educational institutions, and the private sector in the pursuit of national priorities for the advancement of science, technology, engineering, and mathematics. The ISS National Laboratory also opens new paths for the exploration and economic development of space. In this presentation we will explore the operation of the ISS and the realm of scientific research onboard that includes: (1) Human Research, (2) Biology & Biotechnology, (3) Physical & Material Sciences, (4) Technology, and (5) Earth & Space Science.

Spatial-temporal variations of seismic noise and their relation to wind, rivers, and basins in central Alaska

NASA Astrophysics Data System (ADS)

Smith, K.; Tape, C.; Bruton, C. P.; West, M. E.

2016-12-01

Continuous seismic recordings-or ambient noise-provide means for time-dependent monitoring of site conditions. Frequency-domain amplitude spectra of seismic recordings can be used to characterize time-dependent variations as a function of period (or frequency). Spatial variations can be characterized by using a set of stations across a large region. We analyze time-dependent ambient noise spectra from stations across central Alaska with three purposes. First, we are interested in monitoring the station performance and quality of a new array (FLATS) of 13 posthole seismometers near the Tanana River in Minto Flats. Second, we want to understand time-dependent threshold levels for earthquake detection: when noise is high, earthquake detections are low. Third, we are interested in identifying the effects of nature and Earth structure on seismic stations at different spatial-temporal scales. Our results show that seismic stations are sensitive to variations in wind speed and river flow. Correlations between wind speed and long-period (>10 seconds) seismic noise variations are probably due to tilt effects that have been previously documented. We identify a seismic signal at 10 Hz that is present only on stations close (<100 m) to the main channel of the Tanana river. The 10-Hz signal is strongly correlated with river gage height during summer and weakly correlated during the winter, when the river surface is covered in 1 m of ice. Spatial correlations among stations reveal large variations at shorter time scales (days); these could be due to weather anomalies. The amplitude of seismic noise at periods 2-10 s is strongly influenced by the thickness of sediment, which ranges from 0 m at bedrock sites to 6000 m at sites in the deepest part of Nenana basin. Our analysis allows us to better monitor the performance of temporary and permanent seismic stations, and to understand the physical causes of time-dependent noise variations in Alaska. Our findings show that seismic

Lithospheric structure below seismic stations in Cuba from the joint inversion of Rayleigh surface waves dispersion and receiver functions

NASA Astrophysics Data System (ADS)

González, O'Leary; Moreno, Bladimir; Romanelli, Fabio; Panza, Giuliano F.

2012-05-01

The joint inversion of Rayleigh wave group velocity dispersion and receiver functions has been used to study the crust and upper mantle structure at eight seismic stations in Cuba. Receiver functions have been computed from teleseismic recordings of earthquakes at epicentral (angular) distances in the range from 30° to 90° and Rayleigh wave group velocity dispersion relations have been taken from earlier surface wave tomographic studies in the Caribbean area. The thickest crust (˜30 km) below Cuban stations is found at Cascorro (CCC) and Maisí (MAS) whereas the thinnest crust (˜18 km) is found at stations Río Carpintero (RCC) and Guantánamo Bay (GTBY), in the southeastern part of Cuba; this result is in agreement with the southward gradual thinning of the crust revealed by previous studies. In the crystalline crust, the S-wave velocity varies between ˜2.8 and ˜3.9 km s-1 and, at the crust-mantle transition zone, the shear wave velocity varies from ˜4.0 and ˜4.3 km s-1. The lithospheric thickness varies from ˜65 km, in the youngest lithosphere, to ˜150 km in the northeastern part of the Cuban island, below Maisí (MAS) and Moa (MOA) stations. Evidence of a subducted slab possibly belonging to the Caribbean plate is present below the stations Las Mercedes (LMG), RCC and GTBY whereas earlier subducted slabs could explain the results obtained below the Soroa (SOR), Manicaragua (MGV) and Cascorro (CCC) station.

Regional travel-time residual studies and station correction from 1-D velocity models for some stations around Peninsular Malaysia and Singapore

NASA Astrophysics Data System (ADS)

Osagie, Abel U.; Nawawi, Mohd.; Khalil, Amin Esmail; Abdullah, Khiruddin

2017-06-01

We have investigated the average P-wave travel-time residuals for some stations around Southern Thailand, Peninsular Malaysia and Singapore at regional distances. Six years (January, 2010-December, 2015) record of events from central and northern Sumatra was obtained from the digital seismic archives of Integrated Research Institute for Seismology (IRIS). The criteria used for the data selection are designed to be above the magnitude of mb 4.5, depth less than 200 km and an epicentral distance shorter than 1000 km. Within this window a total number of 152 earthquakes were obtained. Furthermore, data were filtered based on the clarity of the seismic phases that are manually picked. A total of 1088 P-wave arrivals and 962 S-wave arrivals were hand-picked from 10 seismic stations around the Peninsula. Three stations IPM, KUM, and KOM from Peninsular Malaysia, four stations BTDF, NTU, BESC and KAPK from Singapore and three stations SURA, SRIT and SKLT located in the southern part of Thailand are used. Station NTU was chosen as the Ref. station because it recorded the large number of events. Travel-times were calculated using three 1-D models (Preliminary Ref. Earth Model PREM (Dziewonski and Anderson, 1981, IASP91, and Lienert et al., 1986) and an adopted two-point ray tracing algorithm. For the three models, we corroborate our calculated travel-times with the results from the use of TAUP travel-time calculation software. Relative to station NTU, our results show that the average P wave travel-time residual for PREM model ranges from -0.16 to 0.45 s for BESC and IPM respectively. For IASP91 model, the average residual ranges from -0.25 to 0.24 s for SRIT and SKLT respectively, and ranges from -0.22 to 0.30 s for KAPK and IPM respectively for Lienert et al. (1986) model. Generally, most stations have slightly positive residuals relative to station NTU. These corrections reflect the difference between actual and estimated model velocities along ray paths to stations and

The persistent signature of tropical cyclones in ambient seismic noise

NASA Astrophysics Data System (ADS)

Gualtieri, Lucia; Camargo, Suzana J.; Pascale, Salvatore; Pons, Flavio M. E.; Ekström, Göran

2018-02-01

The spectrum of ambient seismic noise shows strong signals associated with tropical cyclones, yet a detailed understanding of these signals and the relationship between them and the storms is currently lacking. Through the analysis of more than a decade of seismic data recorded at several stations located in and adjacent to the northwest Pacific Ocean, here we show that there is a persistent and frequency-dependent signature of tropical cyclones in ambient seismic noise that depends on characteristics of the storm and on the detailed location of the station relative to the storm. An adaptive statistical model shows that the spectral amplitude of ambient seismic noise, and notably of the short-period secondary microseisms, has a strong relationship with tropical cyclone intensity and can be employed to extract information on the tropical cyclones.

An Experimental Seismic Data and Parameter Exchange System for Interim NEAMTWS

NASA Astrophysics Data System (ADS)

Hanka, W.; Hoffmann, T.; Weber, B.; Heinloo, A.; Hoffmann, M.; Müller-Wrana, T.; Saul, J.

2009-04-01

In 2008 GFZ Potsdam has started to operate its global earthquake monitoring system as an experimental seismic background data centre for the interim NEAMTWS (NE Atlantic and Mediterranean Tsunami Warning System). The SeisComP3 (SC3) software, developed within the GITEWS (German Indian Ocean Tsunami Early Warning System) project was extended to test the export and import of individual processing results within a cluster of SC3 systems. The initiated NEAMTWS SC3 cluster consists presently of the 24/7 seismic services at IMP, IGN, LDG/EMSC and KOERI, whereas INGV and NOA are still pending. The GFZ virtual real-time seismic network (GEOFON Extended Virtual Network - GEVN) was substantially extended by many stations from Western European countries optimizing the station distribution for NEAMTWS purposes. To amend the public seismic network (VEBSN - Virtual European Broadband Seismic Network) some attached centres provided additional private stations for NEAMTWS usage. In parallel to the data collection by Internet the GFZ VSAT hub for the secured data collection of the EuroMED GEOFON and NEAMTWS backbone network stations became operational and the first data links were established. In 2008 the experimental system could already prove its performance since a number of relevant earthquakes have happened in NEAMTWS area. The results are very promising in terms of speed as the automatic alerts (reliable solutions based on a minimum of 25 stations and disseminated by emails and SMS) were issued between 2 1/2 and 4 minutes for Greece and 5 minutes for Iceland. They are also promising in terms of accuracy since epicenter coordinates, depth and magnitude estimates were sufficiently accurate from the very beginning, usually don't differ substantially from the final solutions and provide a good starting point for the operations of the interim NEAMTWS. However, although an automatic seismic system is a good first step, 24/7 manned RTWCs are mandatory for regular manual verification

Modernization of the Caltech/USGS Southern California Seismic Network

NASA Astrophysics Data System (ADS)

Bhadha, R.; Devora, A.; Hauksson, E.; Johnson, D.; Thomas, V.; Watkins, M.; Yip, R.; Yu, E.; Given, D.; Cone, G.; Koesterer, C.

2009-12-01

The USGS/ANSS/ARRA program is providing Government Furnished Equipment (GFE), and two year funding for upgrading the Caltech/USGS Southern California Seismic Network (SCSN). The SCSN is the modern digital ground motion seismic network in southern California that monitors seismicity and provides real-time earthquake information products such as rapid notifications, moment tensors, and ShakeMap. The SCSN has evolved through the years and now consists of several well-integrated components such as Short-Period analog, TERRAscope, digital stations, and real-time strong motion stations, or about 300 stations. In addition, the SCSN records data from about 100 stations provided by partner networks. To strengthen the ability of SCSN to meet the ANSS performance standards, we will install GFE and carry out the following upgrades and improvements of the various components of the SCSN: 1) Upgrade of dataloggers at seven TERRAscope stations; 2) Upgrade of dataloggers at 131 digital stations and upgrade broadband sensors at 25 stations; 3) Upgrade of SCSN metadata capabilities; 4) Upgrade of telemetry capabilities for both seismic and GPS data; and 5) Upgrade balers at stations with existing Q330 dataloggers. These upgrades will enable the SCSN to meet the ANSS Performance Standards more consistently than before. The new equipment will improve station uptimes and reduce maintenance costs. The new equipment will also provide improved waveform data quality and consequently superior data products. The data gaps due to various outages will be minimized, and ‘late’ data will be readily available through retrieval from on-site storage. Compared to the outdated equipment, the new equipment will speed up data delivery by about 10 sec, which is fast enough for earthquake early warning applications. The new equipment also has about a factor of ten lower consumption of power. We will also upgrade the SCSN data acquisition and data center facilities, which will improve the SCSN

Concordia CCD - A Geoscope station in continental Antarctica

NASA Astrophysics Data System (ADS)

Maggi, A.; Lévêque, J.; Thoré, J.; Bes de Berc, M.; Bernard, A.; Danesi, S.; Morelli, A.; Delladio, A.; Sorrentino, D.; Stutzmann, E.; Geoscope Team

2010-12-01

Concordia (Dome C, Antarctica) has had a permanent seismic station since 2005. It is run by EOST and INGV in collaboration with the French and Italian polar institutes (IPEV and PNRA). It is installed in an ice-vault, at 12m depth, distant 1km from the permanent scientific base at Concordia. The temperature in the vault is a constant -55°C. The data quality at the station has improved continuously since its installation. In 2007, the station was declared at ISC as an open station with station code CCD (ConCorDia), with data available upon request. It is only the second permanent station in the Antarctic continent, after South Pole. In 2010, CCD was included in the Geoscope network. Data from CCD starting in 2007 are now freely available from the Geoscope Data Center and IRIS. We present an analysis of the data quality at CCD, and describe the technical difficulties of operating an observatory-quality seismic station in the extreme environmental conditons present in continental Antarctica.

A new dataset of Wood Anderson magnitude from the Trieste (Italy) seismic station

NASA Astrophysics Data System (ADS)

Sandron, Denis; Gentile, G. Francesco; Gentili, Stefania; Rebez, Alessandro; Santulin, Marco; Slejko, Dario

2014-05-01

The standard torsion Wood Anderson (WA) seismograph owes its fame to the fact that historically it has been used for the definition of the magnitude of an earthquake (Richter, 1935). With the progress of the technology, digital broadband (BB) seismographs replaced it. However, for historical consistency and homogeneity with the old seismic catalogues, it is still important continuing to compute the so called Wood Anderson magnitude. In order to evaluate WA magnitude, the synthetic seismograms WA equivalent are simulated convolving the waveforms recorded by a BB instrument with a suitable transfer function. The value of static magnification that should be applied in order to simulate correctly the WA instrument is debated. The original WA instrument in Trieste operated from 1971 to 1992 and the WA magnitude (MAW) estimates were regularly reported in the seismic station bulletins. The calculation of the local magnitude was performed following the Richter's formula (Richter, 1935), using the table of corrections factor unmodified from those calibrated for California and without station correction applied (Finetti, 1972). However, the WA amplitudes were computed as vector sum rather than arithmetic average of the horizontal components, resulting in a systematic overestimation of approximately 0.25, depending on the azimuth. In this work, we have retrieved the E-W and N-S components of the original recordings and re-computed MAW according to the original Richter (1935) formula. In 1992, the WA recording were stopped, due to the long time required for the daily development of the photographic paper, the costs of the photographic paper and the progress of the technology. After a decade of interruption, the WA was recovered and modernized by replacing the recording on photographic paper with an electronic device and it continues presently to record earthquakes. The E-W and N-S components records were memorized, but not published till now. Since 2004, next to the WA (few

Tide-related seismic velocity changes across the English Channel

NASA Astrophysics Data System (ADS)

de Ridder, S.; Valova, V.; Curtis, A.

2016-12-01

Temporal changes in the seismic velocities in the Earth's subsurface are known to occur due to a range of phenomena including seasonal variations, magmatic activity, nonlinear healing after strong ground motion, and glacial loading and unloading. Our goal is to extend observations of small velocity changes towards shorter timescales. Earth tides caused by the gravitational attraction between the Earth and the Moon might affect seismic properties. If tidal velocity variations can be recovered from long range cross-correlations, and can also be coupled to stress-strain induced variations in the elastic properties, that would pave the way for systematic imaging of rheological properties of the upper crust. With this long-term goal, we studied data recorded between January 2010 and December 2015 by four broad-band instruments from the British Geological Survey network. One station is located in Cornwall, two in Devon, and one across the English Channel on the island of Jersey. Continuous seismic recordings of the vertical components of particle velocity were divided into one hour intervals, bandpass filtered between 0.02 and 0.11 Hz, spectrally whitened, and cross-correlated between station pairs. The resulting cross-correlations were stacked into bins corresponding to the average water levels observed at nearby ports resulting in cross-correlation traces as a function of water level, for each station pair. To detect temporal changes, a multi-window time-shift analysis is applied to these inter-station traces. We find a stretch factor that best translates one trace into another: this stretch is indicative of changes in average seismic velocities between the pair of tidal phases. We detected systematic seismic velocity variations as a function of water level. We find that increasing water level coincided with decreasing seismic velocities. Separating the data according to up- and down-going tidal tracts reveals that the observed velocity changes exhibit a time

Digital recovery, modification, and analysis of Tetra Tech seismic horizon mapping, National Petroleum Reserve Alaska (NPRA), northern Alaska

USGS Publications Warehouse

Saltus, R.W.; Kulander, Christopher S.; Potter, Christopher J.

2002-01-01

We have digitized, modified, and analyzed seismic interpretation maps of 12 subsurface stratigraphic horizons spanning portions of the National Petroleum Reserve in Alaska (NPRA). These original maps were prepared by Tetra Tech, Inc., based on about 15,000 miles of seismic data collected from 1974 to 1981. We have also digitized interpreted faults and seismic velocities from Tetra Tech maps. The seismic surfaces were digitized as two-way travel time horizons and converted to depth using Tetra Tech seismic velocities. The depth surfaces were then modified by long-wavelength corrections based on recent USGS seismic re-interpretation along regional seismic lines. We have developed and executed an algorithm to identify and calculate statistics on the area, volume, height, and depth of closed structures based on these seismic horizons. These closure statistics are tabulated and have been used as input to oil and gas assessment calculations for the region. Directories accompanying this report contain basic digitized data, processed data, maps, tabulations of closure statistics, and software relating to this project.

Properties of Repetitive Long-Period Seismicity at Villarrica Volcano, Chile

NASA Astrophysics Data System (ADS)

Richardson, J.; Waite, G. P.; Palma, J.; Johnson, J. B.

2011-12-01

Villarrica Volcano, Chile hosts a persistent lava lake and is characterized by degassing and long-period seismicity. In order to better understand the relationship between outgassing and seismicity, we recorded broadband seismic and acoustic data along with high-rate SO2 emission data. We used both a densely-spaced linear array deployed on the northern flank of Villarrica, during the austral summer of 2011, and a wider aperture array of stations distributed around the volcano that was active in the austral summer of 2010. Both deployments consisted of three-component broadband stations and were augmented with broadband infrasound sensors. Of particular interests are repetitive, ~1 Hz seismic and coincident infrasound signals that occurred approximately every 2 minutes. Because these events are typically very low amplitude, we used a matched filter approach to identify them. We windowed several high-amplitude records of these events from broadband seismic stations near the vent. The record section of each event served as a template to compare with the entire dataset by cross-correlation. This approach identified ~20,000 nearly identical events during the ~7 day deployment of the linear array, which were otherwise difficult to identify in the raw records. Assuming that all of the events that we identified have identical source mechanisms and depths, we stack the large suite of events to produce low-noise records and particle motions at receivers farther than 5 km from the vent. We find that the records from stations near the edifice are dominated by tangential particle motion, suggesting the influence of near-field components. Correlation of these data with broadband acoustic data collected at the summit suggest that these repeatable seismic processes are linked to acoustic emissions, probably due to gas bubbles bursting at the magma free surface, as no eruptive products besides gas were being emitted by the volcano during the instrument deployment. The acoustic

Correction of clock errors in seismic data using noise cross-correlations

NASA Astrophysics Data System (ADS)

Hable, Sarah; Sigloch, Karin; Barruol, Guilhem; Hadziioannou, Céline

2017-04-01

Correct and verifiable timing of seismic records is crucial for most seismological applications. For seismic land stations, frequent synchronization of the internal station clock with a GPS signal should ensure accurate timing, but loss of GPS synchronization is a common occurrence, especially for remote, temporary stations. In such cases, retrieval of clock timing has been a long-standing problem. The same timing problem applies to Ocean Bottom Seismometers (OBS), where no GPS signal can be received during deployment and only two GPS synchronizations can be attempted upon deployment and recovery. If successful, a skew correction is usually applied, where the final timing deviation is interpolated linearly across the entire operation period. If GPS synchronization upon recovery fails, then even this simple and unverified, first-order correction is not possible. In recent years, the usage of cross-correlation functions (CCFs) of ambient seismic noise has been demonstrated as a clock-correction method for certain network geometries. We demonstrate the great potential of this technique for island stations and OBS that were installed in the course of the Réunion Hotspot and Upper Mantle - Réunions Unterer Mantel (RHUM-RUM) project in the western Indian Ocean. Four stations on the island La Réunion were affected by clock errors of up to several minutes due to a missing GPS signal. CCFs are calculated for each day and compared with a reference cross-correlation function (RCF), which is usually the average of all CCFs. The clock error of each day is then determined from the measured shift between the daily CCFs and the RCF. To improve the accuracy of the method, CCFs are computed for several land stations and all three seismic components. Averaging over these station pairs and their 9 component pairs reduces the standard deviation of the clock errors by a factor of 4 (from 80 ms to 20 ms). This procedure permits a continuous monitoring of clock errors where small clock

Seismic data from man-made impacts on the moon.

PubMed

Latham, G; Ewing, M; Dorman, J; Press, F; Toksoz, N; Sutton, G; Meissner, R; Duennebier, F; Nakamura, Y; Kovach, R; Yates, M

1970-11-06

Unusually long reverberations were recorded from two lunar impacts by a seismic station installed on the lunar surface by the Apollo 12 astronauts. Seismic data from these impacts suggest that the lunar mare in the region of the Apollo 12 landing site consists of material with very low seismic velocities near the surface, with velocity increasing with depth to 5 to 6 kilometers per second (for compressional waves) at a depth of 20 kilometers. Absorption of seismic waves in this structure is extremely low relative to typical continental crustal materials on earth. It is unlikely that a major boundary similar to the crustmantle interface on earth exists in the outer 20 kilometers of the moon. A combination of dispersion and scattering of surface waves probably explains the lunar seismic reverberation. Scattering of these waves implies the presence of heterogeneity within the outer zone of the mare on a scale of from several hundred meters (or less) to several kilometers. Seismic signals from 160 events of natural origin have been recorded during the first 7 months of operation of the Apollo 12 seismic station. At least 26 of the natural events are small moonquakes. Many of the natural events are thought to be meteoroid impacts.

Fifth National Seismic Conference on Bridges & Highways : innovations in earthquake engineering for highway structures

DOT National Transportation Integrated Search

2007-02-01

This document is the conference program of the 5th National Seismic Conference on Bridges and Highways. The conference was held in San Francisco on September 18-20, 2006 and attracted over 300 engineers, academician, and students from around the worl...

Station corrections for the Katmai Region Seismic Network

USGS Publications Warehouse

Searcy, Cheryl K.

2003-01-01

Most procedures for routinely locating earthquake hypocenters within a local network are constrained to using laterally homogeneous velocity models to represent the Earth's crustal velocity structure. As a result, earthquake location errors may arise due to actual lateral variations in the Earth's velocity structure. Station corrections can be used to compensate for heterogeneous velocity structure near individual stations (Douglas, 1967; Pujol, 1988). The HYPOELLIPSE program (Lahr, 1999) used by the Alaska Volcano Observatory (AVO) to locate earthquakes in Cook Inlet and the Aleutian Islands is a robust and efficient program that uses one-dimensional velocity models to determine hypocenters of local and regional earthquakes. This program does have the capability of utilizing station corrections within it's earthquake location proceedure. The velocity structures of Cook Inlet and Aleutian volcanoes very likely contain laterally varying heterogeneities. For this reason, the accuracy of earthquake locations in these areas will benefit from the determination and addition of station corrections. In this study, I determine corrections for each station in the Katmai region. The Katmai region is defined to lie between latitudes 57.5 degrees North and 59.00 degrees north and longitudes -154.00 and -156.00 (see Figure 1) and includes Mount Katmai, Novarupta, Mount Martin, Mount Mageik, Snowy Mountain, Mount Trident, and Mount Griggs volcanoes. Station corrections were determined using the computer program VELEST (Kissling, 1994). VELEST inverts arrival time data for one-dimensional velocity models and station corrections using a joint hypocenter determination technique. VELEST can also be used to locate single events.

Recent evolutions of the GEOSCOPE broadband seismic observatory

NASA Astrophysics Data System (ADS)

Vallee, M.; Leroy, N.; Bonaime, S.; Zigone, D.; Stutzmann, E.; Thore, J. Y.; Pardo, C.; Bernard, A.; Pesqueira, F.; Maggi, A.; Vincent, D.

2016-12-01

The GEOSCOPE observatory provides 34 years of continuous broadband data to the scientific community. The 31 operational GEOSCOPE stations are installed in 17 countries, across all continents and on islands throughout the oceans. They are equipped with three component very broadband seismometers (STS1 or STS2) and 24 or 26 bit digitizers (Q330HR). Seismometers are installed with warpless base plates, which decrease long period noise on horizontal components by up to 15dB. All stations send data in real time to the GEOSCOPE data center and are automatically transmitted to other data centers (IRIS-DMC and RESIF) and tsunami warning centers. In 2016, a new station has been installed in Wallis and Futuna (FUTU, South-Western Pacific Ocean), and final work is done to reinstall WUS station in Western China. Data of the stations are technically validated by IPGP (25 stations) or EOST (6 stations) in order to check their continuity and integrity. A scientific data validation is also performed by analyzing seismic noise level of the continuous data and by comparing real and synthetic earthquake waveforms (body waves). After these validations, data are archived by the GEOSCOPE data center in Paris. They are made available to the international scientific community through different interfaces (see details on http://geoscope.ipgp.fr ). An important technical work is now done to homogenize the data formats of the whole GEOSCOPE database, in order to make easier the data duplication at the IRIS-DMC and RESIF data centers. The GEOSCOPE broadband seismic observatory also provides near-real time information on the World large seismicity (above magnitude 5.5-6) through the automated application of the SCARDEC method. By using global data from the FDSN - in particular from GEOSCOPE and IRIS/USGS stations -, earthquake source parameters (depth, moment magnitude, focal mechanism, source time function) are determined about 45 minutes after the occurrence of the event. A specific webpage

Peru Subduction Zone Seismic Experiment (PeruSZE): Preliminary Results From a Seismic Network Between Mollendo and Lake Titicaca, Peru.

NASA Astrophysics Data System (ADS)

Guy, R.; Stubailo, I.; Skinner, S.; Phillips, K.; Foote, E.; Lukac, M.; Aguilar, V.; Tavera, H.; Audin, L.; Husker, A.; Clayton, R.; Davis, P. M.

2008-12-01

This work describes preliminary results from a 50 station broadband seismic network recently installed from the coast to the high Andes in Peru. UCLA's Center for Embedded Network Sensing (CENS) and Caltech's Tectonic Observatory are collaborating with the IRD (French L'Institut de Recherche pour le Developpement) and the Institute of Geophysics, in Lima Peru in a broadband seismic experiment that will study the transition from steep to shallow slab subduction. The currently installed line has stations located above the steep subduction zone at a spacing of about 6 km. In 2009 we plan to install a line of 50 stations north from this line along the crest of the Andes, crossing the transition from steep to shallow subduction. A further line from the end of that line back to the coast, completing a U shaped array, is in the planning phase. The network is wirelessly linked using multi-hop network software designed by computer scientists in CENS in which data is transmitted from station to station, and collected at Internet drops, from where it is transmitted over the Internet to CENS each night. The instrument installation in Peru is almost finished and we have been receiving data daily from 10 stations (out of total 50) since June 2008. The rest are recording on-site while the RF network is being completed. The software system provides dynamic link quality based routing, reliable data delivery, and a disruption tolerant shell interface for managing the system from UCLA without the need to travel to Peru. The near real-time data delivery also allows immediate detection of any problems at the sites. We are building a seismic data and GPS quality control toolset that would greatly minimize the station's downtime by alerting the users of any possible problems.

Probing the internal structure of the asteriod Didymoon with a passive seismic investigation

NASA Astrophysics Data System (ADS)

Murdoch, N.; Hempel, S.; Pou, L.; Cadu, A.; Garcia, R. F.; Mimoun, D.; Margerin, L.; Karatekin, O.

2017-09-01

Understanding the internal structure of an asteroid has important implications for interpreting its evolutionary history, for understanding its continuing geological evolution, and also for asteroid deflection and in-situ space resource utilisation. Given the strong evidence that asteroids are seismically active, an in-situ passive seismic experiment could provide information about the asteroid surface and interior properties. Here, we discuss the natural seismic activity that may be present on Didymoon, the secondary component of asteroid (65803) Didymos. Our analysis of the tidal stresses in Didymoon shows that tidal quakes are likely to occur if the secondary has an eccentric orbit. Failure occurs most easily at the asteroid poles and close to the surface for both homogeneous and layered internal structures. Simulations of seismic wave propagation in Didymoon show that the seismic moment of even small meteoroid impacts can generate clearly observable body and surface waves if the asteroid's internal structure is homogeneous. The presence of a regolith layer over a consolidated core can result in the seismic energy becoming trapped in the regolith due to the strong impedance contrast at the regolith-core boundary. The inclusion of macro-porosity (voids) further complexifies the wavefield due to increased scattering. The most prominent seismic waves are always found to be those traveling along the surface of the asteroid and those focusing in the antipodal point of the seismic source. We find also that the waveforms and ground acceleration spectra allow discrimination between the different internal structure models. Although the science return of a passive seismic experiment would be enhanced by having multiple seismic stations, one single seismic station can already vastly improve our knowledge about the seismic environment and sub-surface structure of an asteroid. We describe several seismic measurement techniques that could be applied in order to study the

Travel-time source-specific station correction improves location accuracy

NASA Astrophysics Data System (ADS)

Giuntini, Alessandra; Materni, Valerio; Chiappini, Stefano; Carluccio, Roberto; Console, Rodolfo; Chiappini, Massimo

2013-04-01

Accurate earthquake locations are crucial for investigating seismogenic processes, as well as for applications like verifying compliance to the Comprehensive Test Ban Treaty (CTBT). Earthquake location accuracy is related to the degree of knowledge about the 3-D structure of seismic wave velocity in the Earth. It is well known that modeling errors of calculated travel times may have the effect of shifting the computed epicenters far from the real locations by a distance even larger than the size of the statistical error ellipses, regardless of the accuracy in picking seismic phase arrivals. The consequences of large mislocations of seismic events in the context of the CTBT verification is particularly critical in order to trigger a possible On Site Inspection (OSI). In fact, the Treaty establishes that an OSI area cannot be larger than 1000 km2, and its larger linear dimension cannot be larger than 50 km. Moreover, depth accuracy is crucial for the application of the depth event screening criterion. In the present study, we develop a method of source-specific travel times corrections based on a set of well located events recorded by dense national seismic networks in seismically active regions. The applications concern seismic sequences recorded in Japan, Iran and Italy. We show that mislocations of the order of 10-20 km affecting the epicenters, as well as larger mislocations in hypocentral depths, calculated from a global seismic network and using the standard IASPEI91 travel times can be effectively removed by applying source-specific station corrections.

Epicenter Location of Regional Seismic Events Using Love Wave and Rayleigh Wave Ambient Seismic Noise Green's Functions

NASA Astrophysics Data System (ADS)

Levshin, A. L.; Barmin, M. P.; Moschetti, M. P.; Mendoza, C.; Ritzwoller, M. H.

2011-12-01

We describe a novel method to locate regional seismic events based on exploiting Empirical Green's Functions (EGF) that are produced from ambient seismic noise. Elastic EGFs between pairs of seismic stations are determined by cross-correlating long time-series of ambient noise recorded at the two stations. The EGFs principally contain Rayleigh waves on the vertical-vertical cross-correlations and Love waves on the transverse-transverse cross-correlations. Earlier work (Barmin et al., "Epicentral location based on Rayleigh wave empirical Green's functions from ambient seismic noise", Geophys. J. Int., 2011) showed that group time delays observed on Rayleigh wave EGFs can be exploited to locate to within about 1 km moderate sized earthquakes using USArray Transportable Array (TA) stations. The principal advantage of the method is that the ambient noise EGFs are affected by lateral variations in structure similarly to the earthquake signals, so the location is largely unbiased by 3-D structure. However, locations based on Rayleigh waves alone may be biased by more than 1 km if the earthquake depth is unknown but lies between 2 km and 7 km. This presentation is motivated by the fact that group time delays for Love waves are much less affected by earthquake depth than Rayleigh waves; thus exploitation of Love wave EGFs may reduce location bias caused by uncertainty in event depth. The advantage of Love waves to locate seismic events, however, is mitigated by the fact that Love wave EGFs have a smaller SNR than Rayleigh waves. Here, we test the use of Love and Rayleigh wave EGFs between 5- and 15-sec period to locate seismic events based on the USArray TA in the western US. We focus on locating aftershocks of the 2008 M 6.0 Wells earthquake, mining blasts in Wyoming and Montana, and small earthquakes near Norman, OK and Dallas, TX, some of which may be triggered by hydrofracking or injection wells.

Seismic and hydroacoustic analysis relevant to MH370

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stead, Richard J.

2014-07-03

The vicinity of the Indian Ocean is searched for open and readily available seismic and/or hydroacoustic stations that might have recorded a possible impact of MH370 with the ocean surface. Only three stations are identified: the IMS hydrophone arrays H01 and H08, and the Geoscope seismic station AIS. Analysis of the data from these stations shows an interesting arrival on H01 that has some interference from an Antarctic ice event, large amplitude repeating signals at H08 that obscure any possible arrivals, and large amplitude chaotic noise at AIS precludes any analysis at higher frequencies of interest. The results are thereforemore » rather inconclusive but may point to a more southerly impact location within the overall Indian Ocean search region. The results would be more useful if they can be combined with any other data that are not readily available.« less

Utah's Regional/Urban ANSS Seismic Network---Strategies and Tools for Quality Performance

NASA Astrophysics Data System (ADS)

Burlacu, R.; Arabasz, W. J.; Pankow, K. L.; Pechmann, J. C.; Drobeck, D. L.; Moeinvaziri, A.; Roberson, P. M.; Rusho, J. A.

2007-05-01

The University of Utah's regional/urban seismic network (224 stations recorded: 39 broadband, 87 strong-motion, 98 short-period) has become a model for locally implementing the Advanced National Seismic System (ANSS) because of successes in integrating weak- and strong-motion recording and in developing an effective real-time earthquake information system. Early achievements included implementing ShakeMap, ShakeCast, point-to- multipoint digital telemetry, and an Earthworm Oracle database, as well as in-situ calibration of all broadband and strong-motion stations and submission of all data and metadata into the IRIS DMC. Regarding quality performance, our experience as a medium-size regional network affirms the fundamental importance of basics such as the following: for data acquisition, deliberate attention to high-quality field installations, signal quality, and computer operations; for operational efficiency, a consistent focus on professional project management and human resources; and for customer service, healthy partnerships---including constant interactions with emergency managers, engineers, public policy-makers, and other stakeholders as part of an effective state earthquake program. (Operational cost efficiencies almost invariably involve trade-offs between personnel costs and the quality of hardware and software.) Software tools that we currently rely on for quality performance include those developed by UUSS (e.g., SAC and shell scripts for estimating local magnitudes) and software developed by other organizations such as: USGS (Earthworm), University of Washington (interactive analysis software), ISTI (SeisNetWatch), and IRIS (PDCC, BUD tools). Although there are many pieces, there is little integration. One of the main challenges we face is the availability of a complete and coherent set of tools for automatic and post-processing to assist in achieving the goals/requirements set forth by ANSS. Taking our own network---and ANSS---to the next level

Seismic databases and earthquake catalogue of the Caucasus

NASA Astrophysics Data System (ADS)

Godoladze, Tea; Javakhishvili, Zurab; Tvaradze, Nino; Tumanova, Nino; Jorjiashvili, Nato; Gok, Rengen

2016-04-01

The Caucasus has a documented historical catalog stretching back to the beginning of the Christian era. Most of the largest historical earthquakes prior to the 19th century are assumed to have occurred on active faults of the Greater Caucasus. Important earthquakes include the Samtskhe earthquake of 1283, Ms~7.0, Io=9; Lechkhumi-Svaneti earthquake of 1350, Ms~7.0, Io=9; and the Alaverdi(earthquake of 1742, Ms~6.8, Io=9. Two significant historical earthquakes that may have occurred within the Javakheti plateau in the Lesser Caucasus are the Tmogvi earthquake of 1088, Ms~6.5, Io=9 and the Akhalkalaki earthquake of 1899, Ms~6.3, Io =8-9. Large earthquakes that occurred in the Caucasus within the period of instrumental observation are: Gori 1920; Tabatskuri 1940; Chkhalta 1963; 1991 Ms=7.0 Racha earthquake, the largest event ever recorded in the region; the 1992 M=6.5 Barisakho earthquake; Ms=6.9 Spitak, Armenia earthquake (100 km south of Tbilisi), which killed over 50,000 people in Armenia. Recently, permanent broadband stations have been deployed across the region as part of various national networks (Georgia (~25 stations), Azerbaijan (~35 stations), Armenia (~14 stations)). The data from the last 10 years of observation provides an opportunity to perform modern, fundamental scientific investigations. A catalog of all instrumentally recorded earthquakes has been compiled by the IES (Institute of Earth Sciences, Ilia State University). The catalog consists of more then 80,000 events. Together with our colleagues from Armenia, Azerbaijan and Turkey the database for the Caucasus seismic events was compiled. We tried to improve locations of the events and calculate Moment magnitudes for the events more than magnitude 4 estimate in order to obtain unified magnitude catalogue of the region. The results will serve as the input for the Seismic hazard assessment for the region.

An Experimental Seismic Data and Parameter Exchange System for Tsunami Warning Systems

NASA Astrophysics Data System (ADS)

Hoffmann, T. L.; Hanka, W.; Saul, J.; Weber, B.; Becker, J.; Heinloo, A.; Hoffmann, M.

2009-12-01

For several years GFZ Potsdam is operating a global earthquake monitoring system. Since the beginning of 2008, this system is also used as an experimental seismic background data center for two different regional Tsunami Warning Systems (TWS), the IOTWS (Indian Ocean) and the interim NEAMTWS (NE Atlantic and Mediterranean). The SeisComP3 (SC3) software, developed within the GITEWS (German Indian Ocean Tsunami Early Warning System) project, capable to acquire, archive and process real-time data feeds, was extended for export and import of individual processing results within the two clusters of connected SC3 systems. Therefore not only real-time waveform data are routed to the attached warning centers through GFZ but also processing results. While the current experimental NEAMTWS cluster consists of SC3 systems in six designated national warning centers in Europe, the IOTWS cluster presently includes seven centers, with another three likely to join in 2009/10. For NEAMTWS purposes, the GFZ virtual real-time seismic network (GEOFON Extended Virtual Network -GEVN) in Europe was substantially extended by adding many stations from Western European countries optimizing the station distribution. In parallel to the data collection over the Internet, a GFZ VSAT hub for secured data collection of the EuroMED GEOFON and NEAMTWS backbone network stations became operational and first data links were established through this backbone. For the Southeast Asia region, a VSAT hub has been established in Jakarta already in 2006, with some other partner networks connecting to this backbone via the Internet. Since its establishment, the experimental system has had the opportunity to prove its performance in a number of relevant earthquakes. Reliable solutions derived from a minimum of 25 stations were very promising in terms of speed. For important events, automatic alerts were released and disseminated by emails and SMS. Manually verified solutions are added as soon as they become

CzechGeo/EPOS - Building a national data portal

NASA Astrophysics Data System (ADS)

Zednik, J.; Hejda, P.

2012-04-01

CzechGeo/EPOS is the consortium of seven geoscience institutions in the Czech Republic (Institute of Geophysics AS CR Prague, Institute of Rock Structure and Mechanics AS CR Prague, Institute of Geonics AS CR Ostrava, Institute of Physics of the Earth, Masaryk University Brno, Faculty of Mathematics and Physics, Charles University Prague, Faculty of Science, Charles University Prague, and Research Institute of Geodesy, Cartography and Topography Zdiby). These institutions operate a distributed system of seismic, GPS, magnetic, gravimetric and geodynamic observatories. The operational and personal costs of CzechGeo/EPOS are mostly covered by the Ministry of education, sports and youth within the support of twelve large research infrastructures in the Czech Republic. Web pages of the project www.czechgeo.cz are being built as a data portal which should integrate all the data and services provided by the involved institutions and research infrastructures. Seismic portal offers selected portions of digital data from permanent, local and temporary seismic stations, locations of seismic events in the country and worldwide, daily seismograms from permanent observatories and local seismic network Webnet, seismic bulletins and catalogs, and macroseismic observations on the territory of the Czech Republic. Magnetic portal involves besides real-time magnetograms also recent state of geomagnetic activity and its forecast for the next day. GPS portal will provide preprocessed data from regional GPS stations. Building the national portal is closely related with the development of the Preparatory phase of the EPOS (European Plate Observing System) project.

Preliminary report on the Black Thunder, Wyoming CTBT R and D experiment quicklook report: LLNL input from regional stations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harben, P.E.; Glenn, L.A.

This report presents a preliminary summary of the data recorded at three regional seismic stations from surface blasting at the Black Thunder Coal Mine in northeast Wyoming. The regional stations are part of a larger effort that includes many more seismic stations in the immediate vicinity of the mine. The overall purpose of this effort is to characterize the source function and propagation characteristics of large typical surface mine blasts. A detailed study of source and propagation features of conventional surface blasts is a prerequisite to attempts at discriminating this type of blasting activity from other sources of seismic events.more » The Black Thunder Seismic experiment is a joint verification effort to determine seismic source and path effects that result from very large, but routine ripple-fired surface mining blasts. Studies of the data collected will be for the purpose of understanding how the near-field and regional seismic waveforms from these surface mining blasts are similar to, and different from, point shot explosions and explosions at greater depth. The Black Hills Station is a Designated Seismic Station that was constructed for temporary occupancy by the Former Soviet Union seismic verification scientists in accordance with the Threshold Test Ban Treaty protocol.« less

Automatic classification of seismic events within a regional seismograph network

NASA Astrophysics Data System (ADS)

Tiira, Timo; Kortström, Jari; Uski, Marja

2015-04-01

A fully automatic method for seismic event classification within a sparse regional seismograph network is presented. The tool is based on a supervised pattern recognition technique, Support Vector Machine (SVM), trained here to distinguish weak local earthquakes from a bulk of human-made or spurious seismic events. The classification rules rely on differences in signal energy distribution between natural and artificial seismic sources. Seismic records are divided into four windows, P, P coda, S, and S coda. For each signal window STA is computed in 20 narrow frequency bands between 1 and 41 Hz. The 80 discrimination parameters are used as a training data for the SVM. The SVM models are calculated for 19 on-line seismic stations in Finland. The event data are compiled mainly from fully automatic event solutions that are manually classified after automatic location process. The station-specific SVM training events include 11-302 positive (earthquake) and 227-1048 negative (non-earthquake) examples. The best voting rules for combining results from different stations are determined during an independent testing period. Finally, the network processing rules are applied to an independent evaluation period comprising 4681 fully automatic event determinations, of which 98 % have been manually identified as explosions or noise and 2 % as earthquakes. The SVM method correctly identifies 94 % of the non-earthquakes and all the earthquakes. The results imply that the SVM tool can identify and filter out blasts and spurious events from fully automatic event solutions with a high level of confidence. The tool helps to reduce work-load in manual seismic analysis by leaving only ~5 % of the automatic event determinations, i.e. the probable earthquakes for more detailed seismological analysis. The approach presented is easy to adjust to requirements of a denser or wider high-frequency network, once enough training examples for building a station-specific data set are available.

Coherency of seismic noise, Green functions and site effects

NASA Astrophysics Data System (ADS)

Prieto, G. A.; Beroza, G. C.

2007-12-01

The newly rediscovered methodology of cross correlating seismic noise (or seismic coda) to retrieve the Green function takes advantage of the coherency of the signals across a set of stations. Only coherent signals are expected to emerge after stacking over a long enough time. Cross-correlation has a significant disadvantage for this purpose, in that the Green function recovered is convolved with the source-time function of the noise source. For seismic waves, this can mean that the microseism peak dominates the signal. We show how the use of the transfer function between sensors provides a better resolved Green function (after inverse Fourier transform), because the deconvolution process removes the effect of the noise source-time function. In addition, we compute the coherence of the seismic noise as a function of frequency and distance, providing information about the effective frequency band over which Green function retrieval is possible. The coherence may also be used in resolution analysis for time reversal as a constraint on the de-coherence length (the distance between sensors over which the signals become uncorrelated). We use the information from the transfer function and the coherence to examine wave propagation effects (attenuation and site effects) for closely spaced stations compared to a reference station.

Seismic monitoring of the bedload transport in La Réunion Island rivers during tropical cyclones

NASA Astrophysics Data System (ADS)

Gonzalez, Alicia; Fontaine, Fabrice. R.; Burtin, Arnaud; Barruol, Guilhem; Recking, Alain; Join, Jean-Lambert; Delcher, Eric

2017-04-01

La Réunion Island, located in the western Indian Ocean, undergoes heavy annual precipitations during the rainy season (Dec to Apr) and particularly during tropical depressions and cyclones. Large rainfalls that affect this volcanic island modify the stream dynamic and control the sediment transport and the very active erosion. However, in situ characterization of sediment transport is difficult during high water stage, requiring indirect observation such as seismic noise. In order to monitor spatial and temporal variations of the river's bed-load during tropical cyclones from the high-frequency seismic noise in La Réunion, we deployed a temporary seismic network of 9 three-component broadband seismometers along two rivers: Rivière des Pluies and Rivière du Mât, both located on the northern side of the island. Seismic data are supplemented by meteorological and hydrological stations installed in these experimental watersheds. They provide valuable data such as precipitations, water discharge and water level. We also characterized the stream morphology and the bed surface grain size distribution to set the current characteristics and we aim to repeat this analyze after each flood event in order to quantify the effect of the flood episode on the sediment transport. We present the results of the signature of the cyclone Bejisa which passed close to the island in January 2014 recorded at three broadband seismic stations, among which two are located near instrumented streams: station SALA installed close to the Rivière du Mât and the permanent GEOSCOPE seismic station RER installed in a 4.7 km long tunnel close to the Rivière de l'Est. The third station MAID is used as a reference station since it is located on a summit (2.190 km altitude) and far from any active river. We observe a significant increase of the precipitation as the cyclone eye was at 300 km to the island and the associated increase of the water discharge clearly generates a sudden increase of the

A fast topographic characterization of seismic station locations in Iran through integrated use of digital elevation models and GIS

NASA Astrophysics Data System (ADS)

Karimzadeh, Sadra; Miyajima, Masakatsu; Kamel, Batoul; Pessina, Vera

2015-10-01

We present topographic slope positions of seismic stations within four independent networks (IGUT, IIEES, GSI, and BHRC) in Iran through integrated use of digital elevation models and GIS. Since topographic amplification factor (TAF) due to ground surface irregularity could be one of the reasons of earthquake wave amplification and unexpected damage of structures located on the top of ridges in many previous studies, the ridge stations in the study area are recognized using topographic position index (TPI) as a spatial-based scale-dependent approach that helps in classification of topographic positions. We also present the correlation between local topographic positions and V {/s 30} along with Voronoi tiles of two networks (IGUT and IIEES). The obtained results can be profitably used in seismology to establish homogeneous subnetworks based on Voronoi tiles with precise feedback and in the formulation of new ground motion prediction equations with respect to topographic position and topographic amplification factor.

Seismic excitation by the space shuttle Columbia

USGS Publications Warehouse

Kanamori, H.; Mori, J.; Anderson, D.L.; Heaton, T.H.

1991-01-01

SEISMIC stations in southern California recorded the atmospheric shock waves generated by the space shuttle Columbia on its return to the Edwards Air Force base on 13 August 1989 (Fig. 1). In addition to the shock wave, the broad-band IRIS-TERRAscope station at Pasadena recorded a distinct pulse with a period of ???2-3 seconds, which arrived 12.5 seconds before the shock wave (Fig. 2). This pulse was also recorded at the University of Southern California, near downtown Los Angeles, where it arrived 3 seconds after the shock wave. The origin of this pulse could not be readily identified. We show here that it was a seismic P wave excited by the motion of high-rise buildings in downtown Los Angeles, which were hit by the shock wave. The proximity of the natural period of the high-rise buildings to that of the Los Angeles basin enabled efficient energy transfer from shock wave to seismic wave.

Permafrost Active Layer Seismic Interferometry Experiment (PALSIE).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abbott, Robert; Knox, Hunter Anne; James, Stephanie

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)more » 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.« less

Determination of Rayleigh wave ellipticity across the Earthscope Transportable Array using single-station and array-based processing of ambient seismic noise

NASA Astrophysics Data System (ADS)

Workman, Eli; Lin, Fan-Chi; Koper, Keith D.

2017-01-01

We present a single station method for the determination of Rayleigh wave ellipticity, or Rayleigh wave horizontal to vertical amplitude ratio (H/V) using Frequency Dependent Polarization Analysis (FDPA). This procedure uses singular value decomposition of 3-by-3 spectral covariance matrices over 1-hr time windows to determine properties of the ambient seismic noise field such as particle motion and dominant wave-type. In FPDA, if the noise is mostly dominated by a primary singular value and the phase difference is roughly 90° between the major horizontal axis and the vertical axis of the corresponding singular vector, we infer that Rayleigh waves are dominant and measure an H/V ratio for that hour and frequency bin. We perform this analysis for all available data from the Earthscope Transportable Array between 2004 and 2014. We compare the observed Rayleigh wave H/V ratios with those previously measured by multicomponent, multistation noise cross-correlation (NCC), as well as classical noise spectrum H/V ratio analysis (NSHV). At 8 s the results from all three methods agree, suggesting that the ambient seismic noise field is Rayleigh wave dominated. Between 10 and 30 s, while the general pattern agrees well, the results from FDPA and NSHV are persistently slightly higher (˜2 per cent) and significantly higher (>20 per cent), respectively, than results from the array-based NCC. This is likely caused by contamination from other wave types (i.e. Love waves, body waves, and tilt noise) in the single station methods, but it could also reflect a small, persistent error in NCC. Additionally, we find that the single station method has difficulty retrieving robust Rayleigh wave H/V ratios within major sedimentary basins, such as the Williston Basin and Mississippi Embayment, where the noise field is likely dominated by reverberating Love waves and tilt noise.

Estimating Local and Near-Regional Velocity and Attenuation Structure from Seismic Noise

DTIC Science & Technology

2008-09-30

seismic array in Costa Rica and Nicaragua from ambient seismic noise using two independent methods, noise cross correlation and beamforming. The noise...Mean-phase velocity-dispersion curves are calculated for the TUCAN seismic array in Costa Rica and Nicaragua from ambient seismic noise using two...stations of the TUCAN seismic array (Figure 4c) using a method similar to Harmon et al. (2007). Variations from Harmon et al. (2007) include removing the

Earthquake Seismic Risk Reduction in Ohio: ODNR's Efforts to Address Issues with Natural and Induced Seismicity

NASA Astrophysics Data System (ADS)

Besana-Ostman, G. M.

2013-05-01

With the increasing concerns regarding both natural and induced seismicity in Ohio, ODNR (Ohio Department of Natural Resources) initial efforts on seismic risk reduction paved way to various changes and improvement to tackle several major issues. For natural earthquakes, regional seismicity indicates a NE-SW structure in the northern portion of the area associated with a number of moderate historical earthquakes but no active trace identified. On the other hand, earthquakes of 1986 and 2011 are most probably incidents of induced seismicity that trigger more public uproar against disposal of regulated waste waters through injections. ODNR, in efforts to adapt with increasing need to regulate all operations related to both the Utica and Marcellus shale play within the state, had recently strengthen itself both through additional human resources and improved infrastructure. Tougher regulations and additional field tests were required that took effect immediately when a M4 earthquake was associated with the operations of an injection well. Public meetings were undertaken focused on educating many local inhabitants related to oil and gas operations, hydraulic fracturing, injection wells, and seismicity. Trainings for new and existing staff were regularly done especially for field inspection, data management and technology advancements. Considering the existing seismic stations that are few and distant related to sites of the injection wells, additional seismic stations were installed to gather baseline data and monitor for earthquakes within the injection area(s). Furthermore, to assess if the sites of the injection wells are safe from active structures, initial geomorphic and structural analyses indicated possible active faults in the northern portion of state oriented NE-SW. With the above-mentioned recent changes, ODNR had made a significant leap not only in the improvement of its principal regulatory role in the state for oil and gas operations but also in its

Large-band seismic characterization of the INFN Gran Sasso National Laboratory

NASA Astrophysics Data System (ADS)

Acernese, F.; Canonico, R.; De Rosa, R.; Giordano, G.; Romano, R.; Barone, F.

2013-04-01

In this paper we present the scientific data recorded by tunable mechanical monolithic horizontal seismometers located in the Gran Sasso National Laboratory of the INFN, within thermally insulating enclosures onto concrete slabs connected to the bedrock. The main goals of this long-term large-band measurements are for the seismic characterization of the site in the frequency band 10-6÷10Hz and the acquisition of all the relevant information for the optimization of the sensors.

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.

Using Antelope and Seiscomp in the framework of the Romanian Seismic Network

NASA Astrophysics Data System (ADS)

Marius Craiu, George; Craiu, Andreea; Marmureanu, Alexandru; Neagoe, Cristian

2014-05-01

The National Institute for Earth Physics (NIEP) operates a real-time seismic network designed to monitor the seismic activity on the Romania territory, dominated by the Vrancea intermediate-depth (60-200 km) earthquakes. The NIEP real-time network currently consists of 102 stations and two seismic arrays equipped with different high quality digitizers (Kinemetrics K2, Quanterra Q330, Quanterra Q330HR, PS6-26, Basalt), broadband and short period seismometers (CMG3ESP, CMG40T, KS2000, KS54000, KS2000, CMG3T, STS2, SH-1, S13, Mark l4c, Ranger, Gs21, Mark 22) and acceleration sensors (Episensor Kinemetrics). The primary goal of the real-time seismic network is to provide earthquake parameters from more broad-band stations with a high dynamic range, for more rapid and accurate computation of the locations and magnitudes of earthquakes. The Seedlink and AntelopeTM program packages are completely automated Antelope seismological system is run at the Data Center in Măgurele. The Antelope data acquisition and processing software is running for real-time processing and post processing. The Antelope real-time system provides automatic event detection, arrival picking, event location, and magnitude calculation. It also provides graphical displays and automatic location within near real time after a local, regional or teleseismic event has occurred SeisComP 3 is another automated system that is run at the NIEP and which provides the following features: data acquisition, data quality control, real-time data exchange and processing, network status monitoring, issuing event alerts, waveform archiving and data distribution, automatic event detection and location, easy access to relevant information about stations, waveforms, and recent earthquakes. The main goal of this paper is to compare both of these data acquisitions systems in order to improve their detection capabilities, location accuracy, magnitude and depth determination and reduce the RMS and other location errors.

Characterizing waveform uncertainty due to ambient noise for the Global Seismic Network

NASA Astrophysics Data System (ADS)

Guandique, J. A.; Burdick, S.; Lekic, V.

2015-12-01

Ambient seismic noise is the vibration present on seismograms not due by any earthquake or discrete source. It can be caused by trees swaying in the wind or trucks rumbling on the freeway, but the main source of noise is the microseism caused by ocean waves. The frequency content and amplitude of seismic noise varies due to weather, season, and the location of a station, among other factors. Because noise affects recordings of earthquake waveforms, better understanding it could improve the detection of small earthquakes, reduce false positives in earthquake early warning, and quantify uncertainty in waveform-based studies In this study, we used two years of 3-component accelerograms from stations in the GSN. We eliminate days with major earthquakes, aggregate analysis by month, and calculate the mean power spectrum for each component and the transfer function between components. For each power spectrum, we determine the dominant frequency and amplitude of the primary (PM) and secondary (SM) microseisms which appear at periods of ~14s and ~7s, as well as any other prominent peaks. The cross-component terms show that noise recorded on different components cannot be treated as independent. Trends in coherence and phase delay suggest directionality in the noise and information about in which modes it propagates. Preliminary results show that the noise on island stations exhibits less monthly variability, and its PM peaks tend to be much weaker than the SM peaks. The continental stations show much less consistent behavior, with higher variability in the PM peaks between stations and higher frequency content during winter months. Stations that are further inland have smaller SM peaks compared to coastal stations, which are more similar to island stations. Using these spectra and cross-component results, we develop a method for generating realistic 3-component seismic noise and covariance matrices, which can be used across various seismic applications.

Comparison of Amplitudes and Frequencies of Explosive vs. Hammer Seismic Sources for a 1-km Seismic Line in West Texas

NASA Astrophysics Data System (ADS)

Kaip, G.; Harder, S. H.; Karplus, M. S.; Vennemann, A.

2016-12-01

In May 2016, the National Seismic Source Facility (NSSF) located at the University of Texas at El Paso (UTEP) Department of Geological Sciences collected seismic data at the Indio Ranch located 30 km southwest of Van Horn, Texas. Both hammer on an aluminum plate and explosive sources were used. The project objective was to image subsurface structures at the ranch, owned by UTEP. Selecting the appropriate seismic source is important to reach project objectives. We compare seismic sources between explosions and hammer on plate, focusing on amplitude and frequency. The seismic line was 1 km long, trending WSW to ENE, with 200 4.5 Hz geophones at 5m spacing and shot locations at 10m spacing. Clay slurry was used in shot holes to increase shot coupling around booster. Trojan Spartan cast boosters (150g) were used in explosive sources in each shot hole (1 hole per station). The end of line shots had 5 shot holes instead of 1 (750g total). The hammer source utilized a 5.5 kg hammer and an aluminum plate. Five hammer blows were stacked at each location to improve signal-to-noise ratio. Explosive sources yield higher amplitude, but lower frequency content. The explosions exhibit a higher signal-to-noise ratio, allowing us to recognize seismic energy deeper and farther from the source. Hammer sources yield higher frequencies, allowing better resolution at shallower depths but have a lower signal-to-noise ratio and lower amplitudes, even with source stacking. We analyze the details of the shot spectra from the different types of sources. A combination of source types can improve data resolution and amplitude, thereby improving imaging potential. However, cost, logistics, and complexities also have a large influence on source selection.

Landslide seismic magnitude

NASA Astrophysics Data System (ADS)

Lin, C. H.; Jan, J. C.; Pu, H. C.; Tu, Y.; Chen, C. C.; Wu, Y. M.

2015-11-01

Landslides have become one of the most deadly natural disasters on earth, not only due to a significant increase in extreme climate change caused by global warming, but also rapid economic development in topographic relief areas. How to detect landslides using a real-time system has become an important question for reducing possible landslide impacts on human society. However, traditional detection of landslides, either through direct surveys in the field or remote sensing images obtained via aircraft or satellites, is highly time consuming. Here we analyze very long period seismic signals (20-50 s) generated by large landslides such as Typhoon Morakot, which passed though Taiwan in August 2009. In addition to successfully locating 109 large landslides, we define landslide seismic magnitude based on an empirical formula: Lm = log ⁡ (A) + 0.55 log ⁡ (Δ) + 2.44, where A is the maximum displacement (μm) recorded at one seismic station and Δ is its distance (km) from the landslide. We conclude that both the location and seismic magnitude of large landslides can be rapidly estimated from broadband seismic networks for both academic and applied purposes, similar to earthquake monitoring. We suggest a real-time algorithm be set up for routine monitoring of landslides in places where they pose a frequent threat.

Bayesian Inference for Signal-Based Seismic Monitoring

NASA Astrophysics Data System (ADS)

Moore, D.

2015-12-01

Traditional seismic monitoring systems rely on discrete detections produced by station processing software, discarding significant information present in the original recorded signal. SIG-VISA (Signal-based Vertically Integrated Seismic Analysis) is a system for global seismic monitoring through Bayesian inference on seismic signals. By modeling signals directly, our forward model is able to incorporate a rich representation of the physics underlying the signal generation process, including source mechanisms, wave propagation, and station response. This allows inference in the model to recover the qualitative behavior of recent geophysical methods including waveform matching and double-differencing, all as part of a unified Bayesian monitoring system that simultaneously detects and locates events from a global network of stations. We demonstrate recent progress in scaling up SIG-VISA to efficiently process the data stream of global signals recorded by the International Monitoring System (IMS), including comparisons against existing processing methods that show increased sensitivity from our signal-based model and in particular the ability to locate events (including aftershock sequences that can tax analyst processing) precisely from waveform correlation effects. We also provide a Bayesian analysis of an alleged low-magnitude event near the DPRK test site in May 2010 [1] [2], investigating whether such an event could plausibly be detected through automated processing in a signal-based monitoring system. [1] Zhang, Miao and Wen, Lianxing. "Seismological Evidence for a Low-Yield Nuclear Test on 12 May 2010 in North Korea". Seismological Research Letters, January/February 2015. [2] Richards, Paul. "A Seismic Event in North Korea on 12 May 2010". CTBTO SnT 2015 oral presentation, video at https://video-archive.ctbto.org/index.php/kmc/preview/partner_id/103/uiconf_id/4421629/entry_id/0_ymmtpps0/delivery/http

Seismic Interferometry at a Large, Dense Array: Capturing the Wavefield at the Source Physics Experiment

NASA Astrophysics Data System (ADS)

Matzel, E.; Mellors, R. J.; Magana-Zook, S. A.

2016-12-01

Seismic interferometry is based on the observation that the Earth's background wavefield includes coherent energy, which can be recovered by observing over long time periods, allowing the incoherent energy to cancel out. The cross correlation of the energy recorded at a pair of stations results in an estimate of the Green's Function (GF) and is equivalent to the record of a simple source located at one of the stations as recorded by the other. This allows high resolution imagery beneath dense seismic networks even in areas of low seismicity. The power of these inter-station techniques increases rapidly as the number of seismometers in a network increases. For large networks the number of correlations computed can run into the millions and this becomes a "big-data" problem where data-management dominates the efficiency of the computations. In this study, we use several methods of seismic interferometry to obtain highly detailed images at the site of the Source Physics Experiment (SPE). The objective of SPE is to obtain a physics-based understanding of how seismic waves are created at and scattered near the source. In 2015, a temporary deployment of 1,000 closely spaced geophones was added to the main network of instruments at the site. We focus on three interferometric techniques: Shot interferometry (SI) uses the SPE shots as rich sources of high frequency, high signal energy. Coda interferometry (CI) isolates the energy from the scattered wavefield of distant earthquakes. Ambient noise correlation (ANC) uses the energy of the ambient background field. In each case, the data recorded at one seismometer are correlated with the data recorded at another to obtain an estimate of the GF between the two. The large network of mixed geophone and broadband instruments at the SPE allows us to calculate over 500,000 GFs, which we use to characterize the site and measure the localized wavefield. This work performed under the auspices of the U.S. Department of Energy by

Using Ambient Seismic Noise to Monitor Post-Seismic Relaxation After the 2010 Mw 7.1 Darfield Earthquake, New Zealand

NASA Astrophysics Data System (ADS)

Savage, M. K.; Heckels, R.; Townend, J.

2015-12-01

Quantifying seismic velocity changes following large earthquakes can provide insights into the crustal response of the earth. The use of ambient seismic noise to monitor these changes is becoming increasingly widespread. Cross-correlations of long-duration ambient noise records can be used to give stable impulse response functions without the need for repeated seismic events. Temporal velocity changes were detected in the four months following the September 2010 Mw 7.1 Darfield event in South Island, New Zealand, using temporary seismic networks originally deployed to record aftershocks in the region. The arrays consisted of stations lying on and surrounding the fault, with a maximum inter-station distance of 156km. The 2010-2011 Canterbury earthquake sequence occurred largely on previously unknown and buried faults. The Darfield earthquake was the first and largest in a sequence of events that hit the region, rupturing the Greendale Fault. A surface rupture of nearly 30km was observed. The sequence also included the Mw 6.3 February 2011 Christchurch event, which caused widespread damage throughout the city and resulted in almost 200 deaths. Nine-component, day-long Green's functions were computed for frequencies between 0.1 - 1.0 Hz for full waveform seismic data from immediately after the 4th September 2010 earthquake until mid-January 2011. Using the moving window cross-spectral method, stacks of daily functions covering the study period (reference functions), were compared to consecutive 10 day stacks of cross-correlations to measure time delays between them. These were then inverted for seismic velocity changes with respect to the reference functions. Over the study period an increase in seismic velocity of 0.25% ± 0.02% was determined proximal to the Greendale fault. These results are similar to studies in other regions, and we attribute the changes to post-seismic relaxation through crack-healing of the Greendale Fault and throughout the region.

Field Installation and Real-Time Data Processing of the New Integrated SeismoGeodetic System with Real-Time Acceleration and Displacement Measurements for Earthquake Characterization Based on High-Rate Seismic and GPS Data

NASA Astrophysics Data System (ADS)

Zimakov, Leonid; Jackson, Michael; Passmore, Paul; Raczka, Jared; Alvarez, Marcos; Barrientos, Sergio

2015-04-01

We will discuss and show the results obtained from an integrated SeismoGeodetic System, model SG160-09, installed in the Chilean National Network. The SG160-09 provides the user high rate GNSS and accelerometer data, full epoch-by-epoch measurement integrity and, using the Trimble Pivot™ SeismoGeodetic App, the ability to create combined GNSS and accelerometer high-rate (200Hz) displacement time series in real-time. The SG160-09 combines seismic recording with GNSS geodetic measurement in a single compact, ruggedized package. The system includes a low-power, 220-channel GNSS receiver powered by the latest Trimble-precise Maxwell™6 technology and supports tracking GPS, GLONASS and Galileo signals. The receiver incorporates on-board GNSS point positioning using Real-Time Precise Point Positioning (PPP) technology with satellite clock and orbit corrections delivered over IP networks. The seismic recording element includes an ANSS Class A, force balance triaxial accelerometer with the latest, low power, 24-bit A/D converter, which produces high-resolution seismic data. The SG160-09 processor acquires and packetizes both seismic and geodetic data and transmits it to the central station using an advanced, error-correction protocol with back fill capability providing data integrity between the field and the processing center. The SG160-09 has been installed in the seismic station close to the area of the Iquique earthquake of April 1, 2014, in northern Chile, a seismically prone area at the current time. The hardware includes the SG160-09 system, external Zephyr Geodetic-2 GNSS antenna, and high-speed Internet communication media. Both acceleration and displacement data was transmitted in real-time to the National Seismological Center in Santiago for real-time data processing using Earthworm / Early Bird software. Command/Control of the field station and real-time GNSS position correction are provided via the Pivot software suite. Data from the SG160-09 system was

Space station interior design: Results of the NASA/AIA space station interior national design competition

NASA Technical Reports Server (NTRS)

Haines, R. F.

1975-01-01

The results of the NASA/AIA space station interior national design competition held during 1971 are presented in order to make available to those who work in the architectural, engineering, and interior design fields the results of this design activity in which the interiors of several space shuttle size modules were designed for optimal habitability. Each design entry also includes a final configuration of all modules into a complete space station. A brief history of the competition is presented with the competition guidelines and constraints. The first place award entry is presented in detail, and specific features from other selected designs are discussed. This is followed by a discussion of how some of these design features might be applied to terrestrial as well as space situations.

Recent evolutions of the GEOSCOPE broadband seismic observatory

NASA Astrophysics Data System (ADS)

Vallée, Martin; Zigone, Dimitri; Bonaimé, Sébastien; Thoré, Jean-Yves; Pesqueira, Frédéric; Pardo, Constanza; Bernard, Armelle; Stutzmann, Eléonore; Maggi, Alessia; Douet, Vincent; Sayadi, Jihane; Lévêque, Jean-Jacques

2017-04-01

The GEOSCOPE observatory provides 35 years of continuous broadband data to the scientific community. The 32 operational GEOSCOPE stations are installed in 17 countries, across all continents and on islands throughout the oceans. They are equipped with three component very broadband seismometers (STS1 or STS2) and 24 or 26 bit digitizers (Q330HR). Seismometers are installed with warpless base plates, which decrease long period noise on horizontal components by up to 15dB. All stations send data in real time to the GEOSCOPE data center and are automatically transmitted to other data centers (IRIS-DMC and RESIF) and tsunami warning centers. In 2016, a new station has been installed in Wallis and Futuna (FUTU, South-Western Pacific Ocean), and WUS station has been reinstalled in Western China. Data of the stations are technically validated by IPGP (25 stations) or EOST (6 stations) in order to check their continuity and integrity. A scientific data validation is also performed by analyzing seismic noise level of the continuous data and by comparing real and synthetic earthquake waveforms (body waves). After these validations, data are archived by the GEOSCOPE data center in Paris. They are made available to the international scientific community through different interfaces (see details on http://geoscope.ipgp.fr). An important technical work is done to homogenize the data formats of the whole GEOSCOPE database, in order to make easier the data duplication at the IRIS-DMC and RESIF data centers. The GEOSCOPE broadband seismic observatory also provides near-real time information on the World large seismicity (above magnitude 5.5-6) through the automated application of the SCARDEC method. By using global data from the FDSN - in particular from GEOSCOPE and IRIS/USGS stations -, earthquake source parameters (depth, moment magnitude, focal mechanism, source time function) are determined about 45 minutes after the occurrence of the event. A specific webpage is then

Newberry EGS Seismic Velocity Model

DOE Data Explorer

Templeton, Dennise

2013-10-01

We use ambient noise correlation (ANC) to create a detailed image of the subsurface seismic velocity at the Newberry EGS site down to 5 km. We collected continuous data for the 22 stations in the Newberry network, together with 12 additional stations from the nearby CC, UO and UW networks. The data were instrument corrected, whitened and converted to single bit traces before cross correlation according to the methodology in Benson (2007). There are 231 unique paths connecting the 22 stations of the Newberry network. The additional networks extended that to 402 unique paths crossing beneath the Newberry site.

Moonquakes and lunar tectonism results from the Apollo passive seismic experiment.

NASA Technical Reports Server (NTRS)

Latham, G.; Ewing, M.; Dorman, J.; Lammlein, D.; Press, F.; Toksoz, N.; Sutton, G.; Duennebier, F.; Nakamura, Y.

1972-01-01

The natural seismicity of the moon appears to be very low relative to that of the earth. However, moonquakes do occur. They are detected by the stations of the Apollo seismic network at an average rate of 1800/yr at Station 14 and at lower rates at Stations 12 and 15. All of the moonquakes are small, and in the few cases for which the foci have been located, they occur at great depth (about 800 km). The frequency of occurrence of moonquakes is strongly correlated with lunar tides. The dynamic processes that generate quakes are clearly much less vigorous within the moon than they are within the earth.

Fifty Years of Seismic Monitoring in Davao,Philippines

NASA Astrophysics Data System (ADS)

McNamara, D. J.

2016-12-01

The Manila Observatory was a 150 years old as of 2015. Fiftry years ago it began a seismic monitoring station in the Island of Mindanao, outside the city of Davao, 7 deg. N and 121 deg. E. approxiamtely. This station was chosen not only for its position on the Ring of Fire but also for the fact the the dip angle of the earth's manetic field is zeo at that location. When the CTBT was established and the Republic of the Philippines (RP) a signatory, the Davao station by agreement with RP, began to send its seismic data to the CTBT database in Vienna. This has continued to the present day with support from CTBTO for updates in equipment and maintainence. We discuss if such a private+government model is the way forward for more comprehensive monitoring in the future.

Seismic switch for strong motion measurement

DOEpatents

Harben, Philip E.; Rodgers, Peter W.; Ewert, Daniel W.

1995-01-01

A seismic switching device that has an input signal from an existing microseismic station seismometer and a signal from a strong motion measuring instrument. The seismic switch monitors the signal level of the strong motion instrument and passes the seismometer signal to the station data telemetry and recording systems. When the strong motion instrument signal level exceeds a user set threshold level, the seismometer signal is switched out and the strong motion signal is passed to the telemetry system. The amount of time the strong motion signal is passed before switching back to the seismometer signal is user controlled between 1 and 15 seconds. If the threshold level is exceeded during a switch time period, the length of time is extended from that instant by one user set time period.

Seismic switch for strong motion measurement

DOEpatents

Harben, P.E.; Rodgers, P.W.; Ewert, D.W.

1995-05-30

A seismic switching device is described that has an input signal from an existing microseismic station seismometer and a signal from a strong motion measuring instrument. The seismic switch monitors the signal level of the strong motion instrument and passes the seismometer signal to the station data telemetry and recording systems. When the strong motion instrument signal level exceeds a user set threshold level, the seismometer signal is switched out and the strong motion signal is passed to the telemetry system. The amount of time the strong motion signal is passed before switching back to the seismometer signal is user controlled between 1 and 15 seconds. If the threshold level is exceeded during a switch time period, the length of time is extended from that instant by one user set time period. 11 figs.

Global Seismic Monitoring: Past, Present, and Future

NASA Astrophysics Data System (ADS)

Zoback, M.; Benz, H.; Oppenheimer, D.

2007-12-01

Global seismological observations began in April 1889 when an earthquake in Tokyo, Japan was accurately recorded in Germany on two different horizontal pendulum instruments. However, modern global observational seismology really began 46 years ago when the 120-station World Wide Standard Seismograph Network was installed by the US to monitor underground nuclear tests and earthquakes using well-calibrated short- and long- period stations. At the same time rapid advances in computing technology enabled researchers to begin sophisticated analysis of the increasing amount of seismic data, which led to better understanding of earthquake source properties and their use in establishing plate tectonics. Today, global seismic networks are operated by German (Geophon), France (Geoscope), the United States (Global Seismograph Network) and the International Monitoring System. Presently, the Federation of Digital Seismograph Networks registers more than 1,000 broadband stations world-wide, a small percentage of the total number of digital seismic stations around the world. Following the devastating Kobe, Japan and Northridge, California earthquakes, Japan and the US have led the world in the integration of existing seismic sensor systems (weak and strong motion) into development of near-real-time, post-earthquake response products like ShakeMap, detailing the spatial distribution of strong shaking. Future challenges include expanding real-time integration of both seismic and geodetic sensor systems to produce early warning of strong shaking, rapid source determination, as well as near-realtime post- earthquake damage assessment. Seismic network data, hydro-acoustic arrays, deep water tide gauges, and satellite imagery of wave propagation should be integrated in real-time to provide input for hydrodynamic modeling yielding the distribution, timing and size of tsunamis runup--which would then be available instantly on the web, e.g. in a Google Earth format. Dense arrays of strong

California Fault Parameters for the National Seismic Hazard Maps and Working Group on California Earthquake Probabilities 2007

USGS Publications Warehouse

Wills, Chris J.; Weldon, Ray J.; Bryant, W.A.

2008-01-01

This report describes development of fault parameters for the 2007 update of the National Seismic Hazard Maps and the Working Group on California Earthquake Probabilities (WGCEP, 2007). These reference parameters are contained within a database intended to be a source of values for use by scientists interested in producing either seismic hazard or deformation models to better understand the current seismic hazards in California. These parameters include descriptions of the geometry and rates of movements of faults throughout the state. These values are intended to provide a starting point for development of more sophisticated deformation models which include known rates of movement on faults as well as geodetic measurements of crustal movement and the rates of movements of the tectonic plates. The values will be used in developing the next generation of the time-independent National Seismic Hazard Maps, and the time-dependant seismic hazard calculations being developed for the WGCEP. Due to the multiple uses of this information, development of these parameters has been coordinated between USGS, CGS and SCEC. SCEC provided the database development and editing tools, in consultation with USGS, Golden. This database has been implemented in Oracle and supports electronic access (e.g., for on-the-fly access). A GUI-based application has also been developed to aid in populating the database. Both the continually updated 'living' version of this database, as well as any locked-down official releases (e.g., used in a published model for calculating earthquake probabilities or seismic shaking hazards) are part of the USGS Quaternary Fault and Fold Database http://earthquake.usgs.gov/regional/qfaults/ . CGS has been primarily responsible for updating and editing of the fault parameters, with extensive input from USGS and SCEC scientists.

Site Assessment of a New State-Wide Seismic Network in Texas (TexNet)

NASA Astrophysics Data System (ADS)

Savvaidis, A.; Young, B.; Mukherjee, T.; Hennings, P.; Rathje, E.; Zalachoris, G.; Young, M.; Walter, J. I.; DeShon, H. R.; Frohlich, C.

2016-12-01

Earthquake activity has recently increased in the southern mid-continent of the U.S., including Texas. To monitor seismicity activity in the state of Texas, a new seismicity monitoring program known as TexNet, was funded by the Texas State Legislature in 2015. TexNet consists of 22 new permanent broadband (120s post-hole) seismic stations that will complement the 17 stations currently operating in the State. These permanent stations will provide the baseline seismicity of the state. In addition, 36 portable stations (incorporating both a 20s post-hole seismometer and a post-hole accelerometer) will be used to densify the network in specific areas, of the State, depending on measured seismicity level, proximity to infrastructure, or other scientific investigations. One goal for TexNet is to provide authenticated data needed to evaluate the location, and frequency of earthquakes. To minimize the uncertainties in earthquake locations and increase detectability of the network, an extensive site assessment survey was conducted. The initial station positions were chosen based on Earthscope, Transportable Array (TA) site positions, while ensuring that the stations were relatively evenly-spaced across the State. We then analyzed the noise and earthquake data from the TA seismometers, and added new locations based on geology, topography, and absence of nearby human activities. A 30-min noise test was conducted at each site to identify the site amplification using HVSR information. A 24-hr survey then followed, where the noise level during day and night was identified, analyzed using power spectral density and compared to the NHNM and NLNM (Peterson, 1993; USGS Open File Report, 322). Based on these survey results nearby alternative sites were evaluated to improve final site position. Full deployment and data streaming is expected by December 2016, and will be discussed during this presentation.

Effects on Chilean Vertical Reference Frame due to the Maule Earthquake co-seismic and post-seismic effects

NASA Astrophysics Data System (ADS)

Montecino, Henry D.; de Freitas, Silvio R. C.; Báez, Juan C.; Ferreira, Vagner G.

2017-12-01

The Maule Earthquake (Mw = 8.8) of February 27, 2010 is among the strongest earthquakes that occurred in recent years throughout the world. The crustal deformation caused by this earthquake has been widely studied using GNSS, InSAR and gravity observations. However, there is currently no estimation of the possible vertical deformations produced by co-seismic and post-seismic effects in segments of the Chilean Vertical Reference Frame (CHVRF). In this paper, we present an estimation of co-seismic and post-seismic deformations on the CHVRF using an indirect approach based on GNSS and Gravity Recovery and Climate Experiment (GRACE) data as well as by applying a trajectory model. GNSS time series were used from 10 continuous GNSS stations in the period from 2007 to 2015, as well as 28 GNSS temporary stations realized before and after the earthquake, and 34 vertical deformation vectors in the region most affected by the earthquake. We considered a set of 147 monthly solutions of spherical harmonic gravity field that were expanded up to degree, as well as order 96 of the GRACE mission provided by Center for Space Research, University of Texas at Austin (UT-CSR) process center. The magnitude of vertical deformation was estimated in part of the Chilean vertical network due to the co-seismic and post-seismic effects. Once we evaluated the hydrological effect, natural and artificial jumps, and the effect of glacial isostatic adjustment in GNSS and GRACE time series, the maximum values associated to co- and post-seismic deformations on orthometric height were found to be ∼-34 cm and 5 cm, respectively. Overall, the deformation caused by the Maule earthquake in orthometric heights is almost entirely explained by the variation in the ellipsoidal heights (over 85% in co-seismic jump); however, coseismic jump in the geoid reached -3.3 mm, and could influence the maintenance of a modern vertical reference network in a medium to long term. We evaluated the consistency for a

Surface wave tomography of Europe from ambient seismic noise

NASA Astrophysics Data System (ADS)

Lu, Yang; Stehly, Laurent; Paul, Anne

2017-04-01

We present a European scale high-resolution 3-D shear wave velocity model derived from ambient seismic noise tomography. In this study, we collect 4 years of continuous seismic recordings from 1293 stations across much of the European region (10˚W-35˚E, 30˚N-75˚N), which yields more than 0.8 million virtual station pairs. This data set compiles records from 67 seismic networks, both permanent and temporary from the EIDA (European Integrated Data Archive). Rayleigh wave group velocity are measured at each station pair using the multiple-filter analysis technique. Group velocity maps are estimated through a linearized tomographic inversion algorithm at period from 5s to 100s. Adaptive parameterization is used to accommodate heterogeneity in data coverage. We then apply a two-step data-driven inversion method to obtain the shear wave velocity model. The two steps refer to a Monte Carlo inversion to build the starting model, followed by a linearized inversion for further improvement. Finally, Moho depth (and its uncertainty) are determined over most of our study region by identifying and analysing sharp velocity discontinuities (and sharpness). The resulting velocity model shows good agreement with main geological features and previous geophyical studies. Moho depth coincides well with that obtained from active seismic experiments. A focus on the Greater Alpine region (covered by the AlpArray seismic network) displays a clear crustal thinning that follows the arcuate shape of the Alps from the southern French Massif Central to southern Germany.

Seismic Constraints on Geometry, Seismic Velocity and Anisotropy of the "African Anomaly"

NASA Astrophysics Data System (ADS)

Wang, Y.; Wen, L.

2006-05-01

lower mantle. A uniform Vs to Vp perturbation ratio of 3:1 can best explain the travel time residuals for the P wave data. The geometry and the inferred S to P velocity perturbation ratio of the anomaly indicate that the "African anomaly" in the lower mantle likely, like the VLVP at its base, is compositionally distinct. We also measured the apparent anisotropic parameters (the fast polarization direction and the split time) for selected 503 SKS and 88 SKKS waveform splits of 118 earthquakes (focal depth > 50 km) recorded by stations in Africa and Europe. We observed a good correlation with stations of apparent anisotropy measurements and consistent measurements from SKS and SKKS phases originated from the same earthquakes when seismic phases sample away from the edges of the VLVP. However, we did not find correlation with stations and consistency for the SKS and SKKS phases sampling near the edges of the VLVP. Because the SKS and SKKS phases have similar propagation paths in the shallow Earth and quite different sampling areas at the CMB, the anisotropy in the lithosphere and asthenosphere should have similar influence on the SKS and SKKS phases. Our observations suggest that part of shear wave splitting for the SKS and SKKS phases sampling at the edges of the VLVP has to originate from the lowermost mantle near the exit points of these phases at the CMB, possibly associated with a complex flow pattern near the edges of the VLVP, while the interior of the VLVP is likely isotropic or weakly anisotropic.

Quantifying the similarity of seismic polarizations

NASA Astrophysics Data System (ADS)

Jones, Joshua P.; Eaton, David W.; Caffagni, Enrico

2016-02-01

Assessing the similarities of seismic attributes can help identify tremor, low signal-to-noise (S/N) signals and converted or reflected phases, in addition to diagnosing site noise and sensor misalignment in arrays. Polarization analysis is a widely accepted method for studying the orientation and directional characteristics of seismic phases via computed attributes, but similarity is ordinarily discussed using qualitative comparisons with reference values or known seismic sources. Here we introduce a technique for quantitative polarization similarity that uses weighted histograms computed in short, overlapping time windows, drawing on methods adapted from the image processing and computer vision literature. Our method accounts for ambiguity in azimuth and incidence angle and variations in S/N ratio. Measuring polarization similarity allows easy identification of site noise and sensor misalignment and can help identify coherent noise and emergent or low S/N phase arrivals. Dissimilar azimuths during phase arrivals indicate misaligned horizontal components, dissimilar incidence angles during phase arrivals indicate misaligned vertical components and dissimilar linear polarization may indicate a secondary noise source. Using records of the Mw = 8.3 Sea of Okhotsk earthquake, from Canadian National Seismic Network broad-band sensors in British Columbia and Yukon Territory, Canada, and a vertical borehole array at Hoadley gas field, central Alberta, Canada, we demonstrate that our method is robust to station spacing. Discrete wavelet analysis extends polarization similarity to the time-frequency domain in a straightforward way. Time-frequency polarization similarities of borehole data suggest that a coherent noise source may have persisted above 8 Hz several months after peak resource extraction from a `flowback' type hydraulic fracture.

SSHAC Level 1 Probabilistic Seismic Hazard Analysis for the Idaho National Laboratory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Payne, Suzette Jackson; Coppersmith, Ryan; Coppersmith, Kevin

A Probabilistic Seismic Hazard Analysis (PSHA) was completed for the Materials and Fuels Complex (MFC), Advanced Test Reactor (ATR), and Naval Reactors Facility (NRF) at the Idaho National Laboratory (INL). The PSHA followed the approaches and procedures for Senior Seismic Hazard Analysis Committee (SSHAC) Level 1 study and included a Participatory Peer Review Panel (PPRP) to provide the confident technical basis and mean-centered estimates of the ground motions. A new risk-informed methodology for evaluating the need for an update of an existing PSHA was developed as part of the Seismic Risk Assessment (SRA) project. To develop and implement the newmore » methodology, the SRA project elected to perform two SSHAC Level 1 PSHAs. The first was for the Fuel Manufacturing Facility (FMF), which is classified as a Seismic Design Category (SDC) 3 nuclear facility. The second was for the ATR Complex, which has facilities classified as SDC-4. The new methodology requires defensible estimates of ground motion levels (mean and full distribution of uncertainty) for its criteria and evaluation process. The INL SSHAC Level 1 PSHA demonstrates the use of the PPRP, evaluation and integration through utilization of a small team with multiple roles and responsibilities (four team members and one specialty contractor), and the feasibility of a short duration schedule (10 months). Additionally, a SSHAC Level 1 PSHA was conducted for NRF to provide guidance on the potential use of a design margin above rock hazard levels for the Spent Fuel Handling Recapitalization Project (SFHP) process facility.« less

Hydra—The National Earthquake Information Center’s 24/7 seismic monitoring, analysis, catalog production, quality analysis, and special studies tool suite

USGS Publications Warehouse

Patton, John M.; Guy, Michelle R.; Benz, Harley M.; Buland, Raymond P.; Erickson, Brian K.; Kragness, David S.

2016-08-18

This report provides an overview of the capabilities and design of Hydra, the global seismic monitoring and analysis system used for earthquake response and catalog production at the U.S. Geological Survey National Earthquake Information Center (NEIC). Hydra supports the NEIC’s worldwide earthquake monitoring mission in areas such as seismic event detection, seismic data insertion and storage, seismic data processing and analysis, and seismic data output.The Hydra system automatically identifies seismic phase arrival times and detects the occurrence of earthquakes in near-real time. The system integrates and inserts parametric and waveform seismic data into discrete events in a database for analysis. Hydra computes seismic event parameters, including locations, multiple magnitudes, moment tensors, and depth estimates. Hydra supports the NEIC’s 24/7 analyst staff with a suite of seismic analysis graphical user interfaces.In addition to the NEIC’s monitoring needs, the system supports the processing of aftershock and temporary deployment data, and supports the NEIC’s quality assurance procedures. The Hydra system continues to be developed to expand its seismic analysis and monitoring capabilities.

Source-Type Identification Analysis Using Regional Seismic Moment Tensors

NASA Astrophysics Data System (ADS)

Chiang, A.; Dreger, D. S.; Ford, S. R.; Walter, W. R.

2012-12-01

Waveform inversion to determine the seismic moment tensor is a standard approach in determining the source mechanism of natural and manmade seismicity, and may be used to identify, or discriminate different types of seismic sources. The successful applications of the regional moment tensor method at the Nevada Test Site (NTS) and the 2006 and 2009 North Korean nuclear tests (Ford et al., 2009a, 2009b, 2010) show that the method is robust and capable for source-type discrimination at regional distances. The well-separated populations of explosions, earthquakes and collapses on a Hudson et al., (1989) source-type diagram enables source-type discrimination; however the question remains whether or not the separation of events is universal in other regions, where we have limited station coverage and knowledge of Earth structure. Ford et al., (2012) have shown that combining regional waveform data and P-wave first motions removes the CLVD-isotropic tradeoff and uniquely discriminating the 2009 North Korean test as an explosion. Therefore, including additional constraints from regional and teleseismic P-wave first motions enables source-type discrimination at regions with limited station coverage. We present moment tensor analysis of earthquakes and explosions (M6) from Lop Nor and Semipalatinsk test sites for station paths crossing Kazakhstan and Western China. We also present analyses of smaller events from industrial sites. In these sparse coverage situations we combine regional long-period waveforms, and high-frequency P-wave polarity from the same stations, as well as from teleseismic arrays to constrain the source type. Discrimination capability with respect to velocity model and station coverage is examined, and additionally we investigate the velocity model dependence of vanishing free-surface traction effects on seismic moment tensor inversion of shallow sources and recovery of explosive scalar moment. Our synthetic data tests indicate that biases in scalar

GNSS station displacement analysis

NASA Astrophysics Data System (ADS)

Haritonova, Diana; Balodis, Janis; Janpaule, Inese; Normand, Madara

2013-04-01

Time series of GNSS station results of both the EUPOS®-Riga and LatPos networks have been developed at the Institute of Geodesy and Geoinformation (University of Latvia). The reference stations from EUREF Permanent Network (EPN) in surroundings of Latvia have been used and Bernese GPS Software, Version 5.0, in both static and kinematic modes was applied. The standard data sets were taken from IGS data base. The results of time series have been analysed and distinctive behaviour of daily and subdaily movements of EUPOS®-Riga and LatPos stations was identified. The reasons of dependence of GNSS station coordinate distribution on possible external factors such as seismic activity of some areas of Latvia and periodic processes were given.

Development of real time monitor system displaying seismic waveform data observed at seafloor seismic network, DONET, for disaster management information

NASA Astrophysics Data System (ADS)

Horikawa, H.; Takaesu, M.; Sueki, K.; Takahashi, N.; Sonoda, A.; Miura, S.; Tsuboi, S.

2014-12-01

Mega-thrust earthquakes are anticipated to occur in the Nankai Trough in southwest Japan. In the source areas, we have deployed seafloor seismic network, DONET (Dense Ocean-floor Network System for Earthquake and Tsunamis), in 2010 in order to monitor seismicity, crustal deformations, and tsunamis. DONET system consists of totally 20 stations, which is composed of six kinds of sensors, including strong-motion seismometers　and quartz pressure gauges. Those stations are densely distributed with an average spatial interval of 15-20 km and cover near the trench axis to coastal areas. Observed data are transferred to a land station through a fiber-optical cable and then to JAMSTEC (Japan Agency for Marine-Earth Science and Technology) data management center through a private network in real time. After 2011 off the Pacific coast of Tohoku Earthquake, each local government close to Nankai Trough try to plan disaster prevention scheme. JAMSTEC will disseminate DONET data combined with research accomplishment so that they will be widely recognized as important earthquake information. In order to open DONET data observed for research to local government, we have developed a web application system, REIS　(Real-time Earthquake Information System). REIS is providing seismic waveform data to some local governments close to Nankai Trough as a pilot study. As soon as operation of DONET is ready, REIS will start full-scale operation. REIS can display seismic waveform data of DONET in real-time, users can select strong motion and pressure data, and configure the options of trace view arrangement, time scale, and amplitude. In addition to real-time monitoring, REIS can display past seismic waveform data and show earthquake epicenters on the map. In this presentation, we briefly introduce DONET system and then show our web　application system. We also discuss our future plans for further developments of REIS.

Using VS30 to Estimate Station ML Adjustments (dML)

NASA Astrophysics Data System (ADS)

Yong, A.; Herrick, J.; Cochran, E. S.; Andrews, J. R.; Yu, E.

2017-12-01

Currently, new seismic stations added to a regional seismic network cannot be used to calculate local or Richter magnitude (ML) until a revised region-wide amplitude decay function is developed. The new station must record a minimum number of local and regional events that meet specific amplitude requirements prior to re-calibration of the amplitude decay function. Therefore, there can be significant delay between when a new station starts contributing real-time waveform packets and when the data can be included in magnitude estimation. The station component adjustments (dML; Uhrhammer et al., 2011) are calculated after first inverting for a new regional amplitude decay function, constrained by the sum of dML for long-running stations. Here, we propose a method to calculate an initial dML using known or proxy values of seismic site conditions. For site conditions, we use the time-averaged shear-wave velocity (VS) of the upper 30 m (VS30). We solve for dML as described in Equation (1) by Uhrhammer et al. (2011): ML = log (A) - log A0 (r) + dML, where A is the maximum Wood and Anderson (1925) trace amplitude (mm), r is the distance (km), and dML is the station adjustment. Measured VS30 and estimated dML data are comprised of records from 887 horizontal components (east-west and north-south orientations) from 93 seismic monitoring stations in the California Integrated Seismic Network. VS30 values range from 202 m/s to 1464 m/s and dML range from -1.10 to 0.39. VS30 and dML exhibit a positive correlation coefficient (R = 0.72), indicating that as VS30 increases, dML increases. This implies that greater site amplification (i.e., lower VS30) results in smaller ML. When we restrict VS30 < 760 m/s to focus on dML at soft soil to soft rock sites, R increases to 0.80. In locations where measured VS30 data are unavailable, we evaluate the use of proxy-based VS30 estimates based on geology, topographic slope and terrain classification, as well as other hybridized methods

J-SHIS - an integrated system for knowing seismic hazard information in Japan

NASA Astrophysics Data System (ADS)

Azuma, H.; Fujiwara, H.; Kawai, S.; Hao, K. X.; Morikawa, N.

2015-12-01

An integrated system of Japan seismic hazard information station (J-SHIS) was established in 2005 for issuing and exchanging information of the National Seismic Hazard Maps for Japan that are based on seismic hazard assessment (SHA). A simplified app, also named J-SHIS, for smartphones is popularly used in Japan based on the integrated system of http://www.j-shis.bosai.go.jp/map/?lang=en. "Smartphone tells hazard" is realized on a cellphone, a tablet and/or a PC. At a given spot, the comprehensive information of SHA map can be easily obtained as below: 1) A SHA probability at given intensity (JMA=5-, 5+, 6-, 6+) within 30 years. 2) A site amplification factor varies within 0.5 ~ 3.0 and expectation is 1 based on surface geology map information. 3) A depth of seismic basement down to ~3,000m based on deeper borehole and geological structure. 4) Scenario earthquake maps: By choosing an active fault, one got the average case for different parameters of the modeling. Then choose a case, you got the shaking map of intensity with color scale. "Seismic Hazard Karte tells more hazard" is another app based on website of http://www.j-shis.bosai.go.jp/labs/karte/. (1) For every mesh of 250m x 250m, professional service SHA information is provided over national-world. (2) With five ranks for eight items, comprehensive SHA information could be delivered. (3) Site amplification factor with an average index is given. (4) Deeper geologic structure modeling is provided with borehole profiling. (5) A SHA probability is assessed within 30 and/or 50 years for the given site. (6) Seismic Hazard curves are given for earthquake sources from inland active fault, subduction zone, undetermined and their summarization. (7) The JMA seismic intensities are assessed in long-term averaged periods of 500-years to ~100,000 years. The app of J-SHIS can be downloaded freely from http://www.j-shis.bosai.go.jp/app-jshis.

Hanford Quarter Seismic Report - 98C Seismicity On and Near the Hanford Site, Pasco Basin, Washington: April 1, 1998 Through June 30, 1998

DOE Office of Scientific and Technical Information (OSTI.GOV)

DC Hartshorn, SP Reidel, AC Rohay

1998-10-23

Hanford Seismic Monitoring provides an uninterrupted collection of high-quality raw and processed seismic data from the Hanford Seismic Network (HSN) for the U.S. Department of Energy and its contractors. The staff also locates aud identifies sources of seismic activity and monitors changes in the hi~orical pattern of seismic activity at the Hanford Site. The data are. compiled archived, and published for use by the Hanford Site for waste management Natural Phenomena Hazards assessments, and engineering design and construction. In addition, the seismic monitoring organization works with the Hanford Site Emergency Services Organization to provide assistance in the event of zinmore » earthquake on the Hanford Site. The HSN and Ihe Eastern Washington Regional Network (EN/RN) consist-of 42 individual sensor sites and 15 radio relay sites maintained by the Hanford Seismic Monitoring staff. The operational rate for the third quarter of FY 1998 for stations in the HSN was 99.99%. The operational rate for the third quarter of FY 1998 for stations of the EWRN was 99.95%. For the third quarter of FY 1998, the acquisition computer triggered 133 times. Of these triggers 11 were local earthquakes: 5 (45Yo) in the Columbia River Basalt Group, 2(1 8%) in the pre-basalt sediments, and 4 (36%) in the crystalline basement. The geologic and tectonic environments where these earthquakes occurred are discussed in this report.« less

Hanford Quarter Seismic Report - 98C Seismicity On and Near the Hanford Site, Pasco Basin, Washington: April 1, 1998 Through June 30, 1998

DOE Office of Scientific and Technical Information (OSTI.GOV)

DC Hartshorn, SP Reidel, AC Rohay.

1998-10-23

Hanford Seismic Monitoring provides an uninterrupted collection of high-quality raw and processed seismic data from the Hanford Seismic Network (HSN) for the U.S. Department of Energy and its contractors. The staff also locates aud identifies sources of seismic activity and monitors changes in the hi orical pattern of seismic activity at the Hanford Site. The data are. compiled archived, and published for use by the Hanford Site for waste management Natural Phenomena Hazards assessments, and engineering design and construction. In addition, the seismic monitoring organization works with the Hanford Site Emergency Services Organization to provide assistance in the event ofmore » zin earthquake on the Hanford Site. The HSN and Ihe Eastern Washington Regional Network (EN/RN) consist-of 42 individual sensor sites and 15 radio relay sites maintained by the Hanford Seismic Monitoring staff. The operational rate for the third quarter of FY 1998 for stations in the HSN was 99.99%. The operational rate for the third quarter of FY 1998 for stations of the EWRN was 99.95%. For the third quarter of FY 1998, the acquisition computer triggered 133 times. Of these triggers 11 were local earthquakes: 5 (45Yo) in the Columbia River Basalt Group, 2(1 8%) in the pre-basalt sediments, and 4 (36%) in the crystalline basement. The geologic and tectonic environments where these earthquakes occurred are discussed in this report.« less

Catalog of seismograph stations operated in support of the ERDA Nevada Operations Office, January 1964 thru June 1976

USGS Publications Warehouse

Navarro, R.; Wuollet, Geraldine M.; Bradley, B.R.

1977-01-01

The seismograph stations listed in this catalog were established over the period January 1964 through June 1976 in support of the Energy Research and Development Administration, Nevada (ERDA/NV) underground weapons testing program at the Nevada Test Site (NTS), central Nevada, and Amchitka, Alaska. For station listings before 1964 see Coast and Geodetic Survey publication, "Seismic Data Summary Nuclear Detonation Program 1961 through 1963", by W. V. Mickey and T. R. Shugart, January 1964. Coordinates of stations instrumented for ERDA's Industrial Application Division (IAD, Plowshare) events are published in separate reports (Appendix A, page 66). In addition to the stations for monitoring the testing program, other stations established for specific seismicity studies, such as the Aleutian Seismicity Network, are also listed.

The Irpinia Seismic Network (ISN): a new Monitoring Infrastructure for Seismic Alert Management in Campania Region, Southern Italy

NASA Astrophysics Data System (ADS)

Iannaccone, G.; Satriano, C.; Weber, E.; Cantore, L.; Corciulo, M.; Romano, L.; Martino, C.; Dicrosta, M.; Zollo, A.

2005-12-01

The Irpinia Seismic Network is an high dynamics, high density seismographic network under development in the Southern Apenninic chain. It is deployed in the area stroken by several destructive earthquakes during last centuries. In its final configuration the network will consist of more than fourty high dynamic seismic stations subdivided in physical subnetworks inter-connected by a robust data transmission system. The system is being designed with two primary targets: -Monitoring and analysis of background seismic activity produced by the active fault system which is the cause for large earthquakes in the past, included the 1980, Irpinia earthquake (Ms=6.9) - Development and experimentation of a prototype system for seismic early and post-event warning to be used for protecting public infrastructures and buildings of strategic relevance of the Regione Campania The seismic network will be completed in two stages: 1 - Deployment of 30 seismic stations along the Campania-Lucania Apenninic chain (to date almost completed) 2 - Setting up radio communication system for data transmission. Installation of 12 additional seismic stations (end of year 2006) To ensure an high dynamic recording range each site is equipped with two type of sensors: 30 force-balance accelerometer (model Guralp CMG5-T) and a velocimeter. In particular, 25 sites with short period three components instrument (model Geotech S13-J) and 5 with broad-band sensor (Nanometrics Trillium, with frequency response in the 0.033-50 Hz band). The used data logger is the Osiris-6 model produced by Agecodagis whose main features are: six channels, O/N 24 bit A/D converter, ARM processor with embedded Linux and open source software, two PCMCIA slots (used for two 5GB microdrive or one disk and wi-fi card), Ethernet, wi-fi and serial communication, low power cosumption (~1 W). Power is ensured by two 120 W solar panels and two 130 Ah gel batteries. Each recording site is equipped with a control/alarm system through

Seismic Attenuation Structure and Intraplate Deformation

NASA Astrophysics Data System (ADS)

Bezada, M.; Kowalke, S.; Smale, J.

2017-12-01

It has been suggested that intraplate deformation and seismicity is localized at weak zones in the lithosphere and at rheological boundaries. Comparisons of intraplate deformation regions with mantle seismic velocity structure suggest a correlation, but are not universally accepted as compelling evidence. We present P-wave attenuation models built from records of teleseismic deep-focus earthquakes in three different regions that show significant correlation between attenuation structure and intraplate seismicity and deformation. In the eastern United States, the New Madrid, Wabash Valley, Eastern Tennessee, Central Virginia, and Carolina seismic zones all occur at or near the edges of high-Q (low attenuation) regions. In Spain, intraplate seismicity is absent from high-Q regions but relatively abundant in surrounding low-Q regions where intraplate orogeny is also observed. In Australia, where our model resolution is relatively poor owing to sparse and uneven station coverage, the Petermann and Alice Springs intraplate orogens occur near the edge of a high-Q feature roughly coinciding with the undeformed Amadeus basin. Our results suggest that lithospheric structure exerts important controls on the localization of intraplate deformation and seismicity and that seismic attenuation is a useful proxy for lithospheric strength.

An Expedient but Fascinating Geophysical Chimera: The Pinyon Flat Seismic Strain Point Array

NASA Astrophysics Data System (ADS)

Langston, C. A.

2016-12-01

The combination of a borehole Gladwin Tensor Strain Meter (GTSM) and a co-located three component broadband seismometer (BB) can theoretically be used to determine the propagation attributes of P-SV waves in vertically inhomogeneous media such as horizontal phase velocity and azimuth of propagation through application of wave gradiometry. A major requirement for this to be successful is to have well-calibrated strain and seismic sensors to be able to rely on using absolute wave amplitude from both systems. A "point" seismic array is constructed using the PBO GTSM station B084 and co-located BB seismic stations from an open array experiment deployed by UCSD as well as PFO station at the Pinyon Flat facility. Site amplitude statics for all three ground motion components are found for the 14-element (13 PY stations + PFO), small aperture seismic array using data from 47 teleseisms recorded from 2014 until present. Precision of amplitude measurement at each site is better than 0.2% for vertical components, 0.5% for EW components, and 1% for NS components. Relative amplitudes among sites of the array are often better than 1% attesting to the high quality of the instrumentation and installation. The wavefield and related horizontal strains are computed for the location of B084 using a second order Taylor's expansion of observed waveforms from moderate ( M4) regional events. The computed seismic array areal, differential, and shear strains show excellent correlation in both phase and amplitude with those recorded by B084 when using the calibration matrix previously determined using teleseismic strains from the entire ANZA seismic network. Use of the GTSM-BB "point" array significantly extends the bandwidth of gradiometry calculations over the small-aperture seismic array by nearly two orders of magnitude from 0.5 Hz to 0.01 Hz. In principle, a seismic strain point array could be constructed from every PBO GTSM with a co-located seismometer to help serve earthquake early

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

Map of Pseudo-F-statistics of seismic noise parameters as an indicator of current seismic danger in Japan

NASA Astrophysics Data System (ADS)

Lyubushin, Alexey

2016-04-01

The problem of estimate of current seismic danger based on monitoring of seismic noise properties from broadband seismic network F-net in Japan (84 stations) is considered. Variations of the following seismic noise parameters are analyzed: multifractal singularity spectrum support width, generalized Hurst exponent, minimum Hölder-Lipschitz exponent and minimum normalized entropy of squared orthogonal wavelet coefficients. These parameters are estimated within adjacent time windows of the length 1 day for seismic noise waveforms from each station. Calculating daily median values of these parameters by all stations provides 4-dimensional time series which describes integral properties of the seismic noise in the region covered by the network. Cluster analysis is applied to the sequence of clouds of 4-dimensional vectors within moving time window of the length 365 days with mutual shift 3 days starting from the beginning of 1997 up to the current time. The purpose of the cluster analysis is to find the best number of clusters (BNC) from probe numbers which are varying from 1 up to the maximum value 40. The BNC is found from the maximum of pseudo-F-statistics (PFS). A 2D map could be created which presents dependence of PFS on the tested probe number of clusters and the right-hand end of moving time window which is rather similar to usual spectral time-frequency diagrams. In the paper [1] it was shown that the BNC before Tohoku mega-earthquake on March 11, 2011, has strongly chaotic regime with jumps from minimum up to maximum values in the time interval 1 year before the event and this time intervals was characterized by high PFS values. The PFS-map is proposed as the method for extracting time intervals with high current seismic danger. The next danger time interval after Tohoku mega-EQ began at the end of 2012 and was finished at the middle of 2013. Starting from middle of 2015 the high PFS values and chaotic regime of BNC variations were returned. This could be

Real-time Seismic Amplitude Measurement (RSAM): a volcano monitoring and prediction tool

USGS Publications Warehouse

Endo, E.T.; Murray, T.

1991-01-01

Seismicity is one of the most commonly monitored phenomena used to determine the state of a volcano and for the prediction of volcanic eruptions. Although several real-time earthquake-detection and data acquisition systems exist, few continuously measure seismic amplitude in circumstances where individual events are difficult to recognize or where volcanic tremor is prevalent. Analog seismic records provide a quick visual overview of activity; however, continuous rapid quantitative analysis to define the intensity of seismic activity for the purpose of predicing volcanic eruptions is not always possible because of clipping that results from the limited dynamic range of analog recorders. At the Cascades Volcano Observatory, an inexpensive 8-bit analog-to-digital system controlled by a laptop computer is used to provide 1-min average-amplitude information from eight telemetered seismic stations. The absolute voltage level for each station is digitized, averaged, and appended in near real-time to a data file on a multiuser computer system. Raw realtime seismic amplitude measurement (RSAM) data or transformed RSAM data are then plotted on a common time base with other available volcano-monitoring information such as tilt. Changes in earthquake activity associated with dome-building episodes, weather, and instrumental difficulties are recognized as distinct patterns in the RSAM data set. RSAM data for domebuilding episodes gradually develop into exponential increases that terminate just before the time of magma extrusion. Mount St. Helens crater earthquakes show up as isolated spikes on amplitude plots for crater seismic stations but seldom for more distant stations. Weather-related noise shows up as low-level, long-term disturbances on all seismic stations, regardless of distance from the volcano. Implemented in mid-1985, the RSAM system has proved valuable in providing up-to-date information on seismic activity for three Mount St. Helens eruptive episodes from 1985 to

Complex Modeling of the Seismic Structure of the Trans-European Suture Zone's Margin from Receiver Function Analysis

NASA Astrophysics Data System (ADS)

Wilde-Piorko, M.; Chrapkiewicz, K.; Lepore, S.; Polkowski, M.; Grad, M.

2016-12-01

The Trans-European Suture Zone (TESZ) is one of the most prominent suture zones in Europe separating the young Paleozoic Platform from the much older Precambrian East European Craton. The data recorded by "13 BB Star" broadband seismic stations (Grad et al., 2015) are analyzed to investigate the crustal and upper mantle structure of the margin of the Trans-European Suture Zone (TESZ) in northern Poland. Receiver function (RF) locally provides the signature of sharp seismic discontinuities and information about the shear wave (S-wave) velocity distribution beneath the seismic station. Recorded seismograms are rotated from ZNE to LQT system with method using the properties of RF (Wilde-Piórko, 2015). Different techniques of receiver function interpretation are applied, including 1-D inversion of RF, 1-D forward modeling of RF, 2.5D forward modeling of RF, 1-D join inversion of RF and dispersion curves of surface wave, to find the best S-wave velocity model of the TESZ margin. A high-resolution 3D P-wave velocity model in the area of Poland (Grad et al. 2016) are used as a starting model. National Science Centre Poland provided financial support for this work by NCN grant DEC-2011/02/A/ST10/00284.

Recent Progress of Seismic Observation Networks in Japan

NASA Astrophysics Data System (ADS)

Okada, Y.

2013-04-01

Before the occurrence of disastrous Kobe earthquake in 1995, the number of high sensitivity seismograph stations operated in Japan was nearly 550 and was concentrated in the Kanto and Tokai districts, central Japan. In the wake of the Kobe earthquake, Japanese government has newly established the Headquarters for Earthquake Research Promotion and started the reconstruction of seismic networks to evenly cover the whole Japan. The basic network is composed of three seismographs, i.e. high sensitivity seismograph (Hi-net), broadband seismograph (F-net), and strong motion seismograph (K-NET). A large majority of Hi-net stations are also equipped with a pair of strong motion sensors at the bottom of borehole and the ground surface (KiK-net). A plenty of high quality data obtained from these networks are circulated at once and is producing several new seismological findings as well as providing the basis for the Earthquake Early Warning system. In March 11, 2011, "Off the Pacific coast of Tohoku Earthquake" was generated with magnitude 9.0, which records the largest in the history of seismic observation in Japan. The greatest disaster on record was brought by huge tsunami with nearly 20 thousand killed or missing people. We are again noticed that seismic observation system is quite poor in the oceanic region compared to the richness of it in the inland region. In 2012, NIED has started the construction of ocean bottom seismic and tsunami observation network along the Japan Trench. It is planned to layout 154 stations with an average spacing of 30km, each of which is equipped with an accelerometer for seismic observation and a water pressure gauge for tsunami observation. We are expecting that more rapid and accurate warning of earthquake and tsunami becomes possible by this observing network.

Enhanced global seismic resolution using proposed undersea cables

NASA Astrophysics Data System (ADS)

Ranasinghe, N. R.; Rowe, C. A.; Larmat, C. S.; Syracuse, E. M.; Begnaud, M. L.

2016-12-01

With the exception of a few isolated, near-shore deployments of Ocean-bottom seismometers (OBS's), most seismic instrumentation on the Earth is located on land, although two thirds of the Earth's surface is covered with oceans. Most large earthquakes are unevenly distributed along the Earth's subduction zones; hence, large areas of the Earth are unevenly sampled in terms of seismic rays. The goal of this work is to produce a comparison of seismic ray coverage of the Earth with today's seismic stations to that which might be possible in the future if densely-instrumented transoceanic cables are deployed.Our work is motivated by the planning of a Joint Task Force under the UN that is proposing to integrate seismic sensors at intervals as small as 75 km along the next generation of oceanic telecommunication cables. These sensors offer the potential to improve global geophysical models as well as reduce event detection thresholds and location uncertainties in poorly characterized regions. Data coverage is first estimated via an infinite-frequency ray-tracing utility (Pcalc) that is used to predict seismic propagation in support of the United States effort towards nuclear explosion monitoring. We have predicted P-wave raypaths from 1668 earthquakes to 4421 seismic stations to produce global raypath density images in the crust and mantle. We present the improvement in ray coverage achieved at crustal and mantle depths by the addition of 1382 sensors along the telecommunication cables and we discuss the areas in which our models and earthquake characterization benefits from these proposed instruments. Because the Earth's complex 3D structure can have frequency-dependent effects on seismic propagation, we also employ a spectral element method (SPECFEM3D) to compute finite-frequency kernels that include the first order of scattering produced by 3D anomalies, and we present progress on this effort to compare with our infinite-frequency predictions.

Seismic footprints of shallow dyke propagation at Etna, Italy.

PubMed

Falsaperla, Susanna; Neri, Marco

2015-07-15

One of the key issues in forecasting volcanic eruptions is to detect signals that can track the propagation of dykes towards the surface. Continuous monitoring of active volcanoes helps significantly in achieving this goal. The seismic data presented here are unique, as they document surface faulting processes close (tens to a few hundred meters) to their source, namely the dyke tip. They originated nearby - and under - a seismic station that was subsequently destroyed by lava flows during eruptive activity at Etna volcano, Italy, in 2013. On February 20, a ~600 m-long and ~120 m wide NW-SE fracture field opened at an altitude between 2750 and 2900 m. The consequent rock dislocation caused the station to tilt and offset the seismic signal temporarily. Data acquisition continued until the arrival of the lava flow that led to the breakdown of the transmission system. Shallow ground fracturing and repeated low-frequency oscillations occurred during two stages in which the seismic signal underwent a maximum offset ~2.57 × 10(4) nm/s. Bridging instrumental recordings, fieldwork and conceptual modelling, these data are interpreted as the seismic footprints of a magmatic dyke intrusion that moved at speed ~0.02 m/s (first stage) and 0.46 m/s (second stage).

Hawaiian Volcano Observatory seismic data, January to December 2005

USGS Publications Warehouse

Nakata, Jennifer S.

2006-01-01

The Hawaiian Volcano Observatory (HVO) summary presents seismic data gathered during the year. The seismic summary is offered without interpretation as a source of preliminary data. It is complete in the sense that most data for events of M-1.5 routinely gathered by the Observatory are included. The HVO summaries have been published in various forms since 1956. Summaries prior to 1974 were issued quarterly, but cost, convenience of preparation and distribution, and the large quantities of data dictated an annual publication beginning with Summary 74 for the year 1974. Summary 86 (the introduction of CUSP at HVO) includes a description of the seismic instrumentation, calibration, and processing used in recent years. Beginning with 2004, summaries will simply be identified by the year, rather than Summary number. The present summary includes background information on the seismic network and processing to allow use of the data and to provide an understanding of how they were gathered. A report by Klein and Koyanagi (1980) tabulates instrumentation, calibration, and recording history of each seismic station in the network. It is designed as a reference for users of seismograms and phase data and includes and augments the information in the station table in this summary.

Hawaiian Volcano Observatory Seismic Data, January to December 2006

USGS Publications Warehouse

Nakata, Jennifer

2007-01-01

Introduction The Hawaiian Volcano Observatory (HVO) summary presents seismic data gathered during the year. The seismic summary is offered without interpretation as a source of preliminary data. It is complete in the sense that most data for events of M>1.5 routinely gathered by the Observatory are included. The HVO summaries have been published in various forms since 1956. Summaries prior to 1974 were issued quarterly, but cost, convenience of preparation and distribution, and the large quantities of data dictated an annual publication beginning with Summary 74 for the year 1974. Summary 86 (the introduction of CUSP at HVO) includes a description of the seismic instrumentation, calibration, and processing used in recent years. Beginning with 2004, summaries are simply identified by the year, rather than Summary number. The present summary includes background information on the seismic network and processing to allow use of the data and to provide an understanding of how they were gathered. A report by Klein and Koyanagi (1980) tabulates instrumentation, calibration, and recording history of each seismic station in the network. It is designed as a reference for users of seismograms and phase data and includes and augments the information in the station table in this summary.

Bananas, Doughnuts and Seismic Traveltimes

NASA Astrophysics Data System (ADS)

Dahlen, F. A.

2002-12-01

Most of what we know about the 3-D seismic heterogeneity of the mantle is based upon ray-theoretical traveltime tomography. In this infinite-frequency approximation, a measured traveltime anomaly depends only upon the wavespeed along an infinitesimally thin geometrical ray between a seismic source and a seismographic station. In this lecture I shall describe a new formulation of the seismic traveltime inverse problem which accounts for the ability of a finite-frequency wave to ``feel'' 3-D structure off of the source-receiver ray. Finite-frequency diffraction effects associated with this off-ray sensitivity act to ``heal'' the corrugations that develop in a wavefront propagating through a heterogeneous medium. Ray-theoretical tomography is based upon the premise that a seismic wave ``remembers'' all of the traveltime advances or delays that it accrues along its path, whereas actual finite-frequency waves ``forget''. I shall describe a number of recent analytical and numerical investigations, which have led to an improved theoretical understanding of this phenomenon.

Site Assessment of a New State-Wide Seismic Network in Texas (TexNet), USA.

NASA Astrophysics Data System (ADS)

Savvaidis, Alexandros; Young, Bissett; Hennings, Peter; Rathje, Ellen; Zalachoris, George; Young, Michael H.; Walter, Jacob I.; DeShon, Heather R.; Frohlich, Cliff

2017-04-01

Earthquake activity has recently increased in the southern mid-continent of the U.S., including Texas. To monitor seismicity activity in the state of Texas, a new seismicity monitoring program known as TexNet, was funded by the Texas State Legislature in 2015. TexNet consists of 22 new permanent broadband (120s post-hole) seismic stations that will complement the 17 stations currently operating in the State. These permanent stations will provide the baseline seismicity of the state. In addition, 36 portable stations (incorporating both a 20s post-hole seismometer and a post-hole accelerometer) will be used to densify the network in specific areas, of the State, depending on measured seismicity level, proximity to infrastructure, or other scientific investigations. One goal for TexNet is to provide authenticated data needed to evaluate the location, and frequency of earthquakes. To minimize the uncertainties in earthquake locations and increase detectability of the network, an extensive site assessment survey was conducted. The initial station positions were chosen based on Earthscope, Transportable Array (TA) site positions, while ensuring that the stations were relatively evenly-spaced across the State. We then analyzed the noise and earthquake data from the TA seismometers, and added new locations based on geology, topography, and absence of nearby human activities. A 30-min noise test was conducted at each site to identify the site amplification using HVSR information. A 24-hr survey then followed, where the noise level during day and night was identified, analyzed using power spectral density and compared to the NHNM and NLNM (Peterson, 1993; USGS Open File Report, 322). Based on these survey results nearby alternative sites were evaluated to improve final site position. Deployment and data streaming started on September 2016, and will be discussed during this presentation.

Support Vector Machine Model for Automatic Detection and Classification of Seismic Events

NASA Astrophysics Data System (ADS)

Barros, Vesna; Barros, Lucas

2016-04-01

The automated processing of multiple seismic signals to detect, localize and classify seismic events is a central tool in both natural hazards monitoring and nuclear treaty verification. However, false detections and missed detections caused by station noise and incorrect classification of arrivals are still an issue and the events are often unclassified or poorly classified. Thus, machine learning techniques can be used in automatic processing for classifying the huge database of seismic recordings and provide more confidence in the final output. Applied in the context of the International Monitoring System (IMS) - a global sensor network developed for the Comprehensive Nuclear-Test-Ban Treaty (CTBT) - we propose a fully automatic method for seismic event detection and classification based on a supervised pattern recognition technique called the Support Vector Machine (SVM). According to Kortström et al., 2015, the advantages of using SVM are handleability of large number of features and effectiveness in high dimensional spaces. Our objective is to detect seismic events from one IMS seismic station located in an area of high seismicity and mining activity and classify them as earthquakes or quarry blasts. It is expected to create a flexible and easily adjustable SVM method that can be applied in different regions and datasets. Taken a step further, accurate results for seismic stations could lead to a modification of the model and its parameters to make it applicable to other waveform technologies used to monitor nuclear explosions such as infrasound and hydroacoustic waveforms. As an authorized user, we have direct access to all IMS data and bulletins through a secure signatory account. A set of significant seismic waveforms containing different types of events (e.g. earthquake, quarry blasts) and noise is being analysed to train the model and learn the typical pattern of the signal from these events. Moreover, comparing the performance of the support

Seismicity in Oklahoma Before Prague

NASA Astrophysics Data System (ADS)

Delorey, A. A.; Johnson, P. A.

2017-12-01

The 2011 M5.7 Prague earthquake was the first large anthropogenically induced earthquake in Oklahoma. Since then, three more M5+ earthquakes followed it near Fairview, Pawnee, and Cushing. Oklahoma induced seismicity has garnered a lot of attention from both the media and the scientific community. But, little is known about seismicity in Oklahoma prior to the Prague earthquake due to a lack of instrumentation. We ask the question, "Was there any indication in the geophysical record prior to the Prague earthquake that bigger earthquakes were becoming more likely?" Fortunately, stations from Earthscope's Transportable Array were in Oklahoma during 2010 and 2011 providing a sparse, but still useful data set. Using our microseismicity detector called Interstation Seismic Coherence, we were able to catalog over 3000 earthquakes with a magnitude of completeness around 2.0 in northeastern Oklahoma over 17 months between June 2010 and the Prague earthquake in November 2011. During this period of time there are less than 200 earthquakes in the ANSS Comprehensive Catalog and 900 in the catalog produced by the Array Network Facility at the UCSD using Transportable Array stations. The M>5 earthquakes occurred in a region where stress conditions and seismicity rates were evolving much faster than they do in many natural systems presenting an opportunity to study the time dependence of upper crustal behavior. A clustering analysis shows that earthquakes occurring in northeastern Oklahoma during 2010-2011 are highly correlated with the magnitude of solid earth tides. Although some aftershocks and clusters were recorded following the Prague earthquake using temporary arrays, regional seismicity is not well recorded again until later in 2013. Of note, after 2013, we no longer observe tidal correlation suggesting the ensemble of fault criticality has evolved. One explanation for this change in earthquake behavior is a change in poroelastic conditions.

Crustal seismic structure beneath the southwest Yunnan region from joint inversion of body-wave and surface wave data

NASA Astrophysics Data System (ADS)

Luo, Y.; Thurber, C. H.; Zeng, X.; Zhang, L.

2016-12-01

Data from 71 broadband stations of a dense transportable array deployed in southwest Yunnan makes it possible to improve the resolution of the seismic model in this region. Continuous waveforms from 12 permanent stations of the China National Seismic Network were also used in this study. We utilized one-year continuous vertical component records to compute ambient noise cross-correlation functions (NCF). More than 3,000 NCFs were obtained and used to measure group velocities between 5 and 25 seconds with the frequency-time analysis method. This frequency band is most sensitive to crustal seismic structure, especially the upper and middle crust. The group velocity at short-period shows a clear azimuthal anisotropy with a north-south fast direction. The fast direction is consistent with previous seismic results revealed from shear wave splitting. More than 2,000 group velocity measurements were employed to invert the surface wave dispersion data for group velocity maps. We applied a finite difference forward modeling algorithm with an iterative inversion. A new body-wave and surface wave joint inversion algorithm (Fang et al., 2016) was utilized to improve the resolution of both P and S models. About 60,000 P wave and S wave arrivals from 1,780 local earthquakes, which occurred from May 2011 to December 2013 with magnitudes larger than 2.0, were manually picked. The new high-resolution seismic structure shows good consistency with local geological features, e.g. Tengchong Volcano. The earthquake locations also were refined with our new velocity model.

The Jalisco Seismic Telemetric Network (RESJAL)

NASA Astrophysics Data System (ADS)

Nunez-Cornu, F. J.; Nunez-Cornu, F. J.; Reyes-Davila, G.; Reyes-Davila, G.; Suarez-Plascencia, C.; Suarez-Plascencia, C.; Gonzalez-Ledezma, M.; Garcia-Puga, J.

2001-12-01

The region of Jalisco is one of the most active seismic regions in Mexico, the main tectonic units in this region are the Jalisco Block and the Rivera Plate. The greatest earthquake (M=8.2) occurred in Mexico in the Twenty-Century (1932) took place in the coast of Jalisco, this was followed by another one (Ms =7.8) fifteen days later. In 1995 an earthquake magnitude 8.0 took place in the coast of Jalisco, but its rupture area was only the southern half of the rupture area proposed for the 1932 earthquakes, these facts suggest the existence of an important seismic Gap in the north coast of Jalisco which includes the area of Bahía de Banderas. However, not only subduction earthquakes occurred in this region there are also large inland earthquakes, such as the December 27, 1568 and February 11, 1872 events. There are also three active volcanoes Sanganguey, Ceboruco and the most active volcano in Mexico, the Colima volcano. In spite of these facts and the risk associated to these processes, there were only one seismological permanent station in Chamela on the coast of Jalisco and an analog telemetric network (RESCO) located on the Colima Volcano and the south part of the Colima Rift Zone (CRZ). By these reasons, the Unidad Estatal de Protección Civil de Jalisco (Jalisco Civil Defense) began a project to install a Digital Telemetric Network in the region in several phases, this project is carrying out jointly with SisVOc UdeG.; due to the size of the area and the topography of the region it is very difficult to get direct telemetric links, by these reasons the network is designed in cells with nodes, where the nodes are the different Campus of the University of Guadalajara located in the region, all Campus are linked by a computer network. First phase started in August 2001, it includes the installation of six stations, each station with a Kinemetrics Everest 24 bit datalogger, GPS time, and a Lennartz LE3Dlite 1Hz sensor, using KNI NMS to control and data acquisition

Present Kinematic Regime and Recent Seismicity of Gulf Suez, Egypt

NASA Astrophysics Data System (ADS)

Mohamed, G.-E. A.; Abd El-Aal, A. K.

2018-01-01

In this study we computed recent seismicity and present kinematic regime in the northern and middle zones of Gulf of Suez as inferred from moment tensor settlings and focal mechanism of local earthquakes that happened in this region. On 18 and 22 of July, 2014 two moderate size earthquakes of local magnitudes 4.2 and 4.1 struck the northern zone of Gulf of Suez near Suez City. These events are instrumentally recorded by Egyptian National Seismic Network (ENSN). The earthquakes have been felt at Suez City and greater Cairo metropolitan zone while no losses were reported. The source mechanism and source parameters of the calculated events were considered by the near-source waveform data listed at very broadband stations of ENSN and supported by the P-wave polarity data of short period stations. The new settling method and software used deem the action of the source time function, which has been ignored in most of the program series of the moment tensor settling analysis with near source seismograms. The obtained results from settling technique indicate that the estimated seismic moments of both earthquakes are 0.6621E + 15 and 0.4447E + 15 Nm conforming to a moment magnitude Mw 3.8 and 3.7 respectively. The fault plan settlings obtained from both settling technique and polarity of first-arrival indicate the dominance of normal faulting. We also evaluated the stress field in north and middle zones of Gulf of Suez using a multiple inverse method. The prime strain axis shows that the deformation is taken up mainly as stretching in the E-W and NE-SW direction.

Relative velocity changes using ambient seismic noise at Okmok and Redoubt volcanoes, Alaska

NASA Astrophysics Data System (ADS)

Bennington, N. L.; Haney, M. M.; De Angelis, S.; Thurber, C. H.

2013-12-01

Okmok and Redoubt are two of the most active volcanoes in the Aleutian Arc. Leading up to its most recent eruption, Okmok, a shield volcano on Umnak Island, showed precursors to volcanic activity only five hours before it erupted explosively in July 2008. Redoubt, a stratovolcano located along the Cook Inlet, displayed several months of precursory activity leading up to its March 2009 eruption. Frequent activity at both volcanoes poses a major hazard due to heavy traffic along the North Pacific air routes. Additionally, Okmok is adjacent to several of the world's most productive fisheries and Redoubt is located only 110 miles SW of Anchorage, the major population center of Alaska. For these reasons, it is imperative that we improve our ability to detect early signs of unrest, which could potentially lead to eruptive activity at these volcanoes. We take advantage of continuous waveforms recorded on seismic networks at Redoubt and Okmok in an attempt to identify seismic precursors to the recent eruptions at both volcanoes. We perform seismic interferometry using ambient noise, following Brenguier et al. (2008), in order to probe the subsurface and determine temporal changes in relative seismic velocity from pre- through post-eruption, for the 2008 Okmok and 2009 Redoubt eruptions. In a preliminary investigation, we analyzed 6 months of noise cross-correlation functions averaged over 10-day intervals leading up to the 2009 eruption at Redoubt. During February 2009, station pairs RSO-DFR and RDN-RSO showed a decrease in seismic velocity of ~0.02%. By the beginning of March, the relative velocity changes returned to background levels. Stations RSO and RDN are located within the summit breach, and station DFR is to the north. Although these results are preliminary, it is interesting to note that the decrease in seismic velocity at both station pairs overlaps with the time period when Grapenthin et al. (2012) hypothesize magma in the mid-to-deep crustal reservoir was

Upgrading the seismic and geodetic network of the Popocatépetl volcano (Mexico).

NASA Astrophysics Data System (ADS)

Calò, Marco; Iglesias Mendoza, Arturo; Legrand, Denis; Valdés González, Carlos Miguel; Perez Campos, Xyoli

2017-04-01

The Popocatépetl is one of the most active volcanoes in Mexico and is located only 70 km from Mexico City, populated by more than 20 millions of people, and only 35 km from the Puebla municipality with almost 1.5 millions of people living. The recent activity of the volcano is generally marked by explosions emitting ash plumes often reaching the densely populated regions. In the framework of the Mexican Fund for Prevention of Natural Disasters (FOPREDEN) we are renovating and upgrading the existing geodetic and seismic networks monitoring the volcano. In this project we are installing 10 broadband seismic stations (120s-050Hz) in shallow boreholes (3-5m depth) and 4 GPS with real time sampling rate of 1 Hz. All instruments are equipped with continuous recording systems for real time monitoring purposes and research. The Popocatépetl exceeds 5400m, and the altitude of the stations ranges from 2200 m to 4300 m making it difficult their installation and maintenance. Because of ash emissions and the hard working condition, the real-time transmission is split into two systems in order to ensure the monitoring of the volcano also during the highest expected activity. Therefore we set up a network of "first order", consisting of four stations located about 20 km from the crater and equipped with satellite transmission. These stations, being far enough from the crater, ensure the real time monitoring of the major events also during intense periods of activity of the volcano. The remaining six stations are installed near to the crater (less than 10 km) and take part of the "second order" network equipped with a telemetered radio system transmitting the data either directly to the National Center of Disaster Prevention (CENAPRED) and National Seismological Service (SSN) or to the first order stations (for the sites that have not direct visible line with the monitoring centers). The four GPS sensors are all installed in the second order sites in order to monitor the largest

Characteristics of seismic noises excited from three typhoons in the western Pacific

NASA Astrophysics Data System (ADS)

Park, S.; Choi, E.; Hong, T. K.

2017-12-01

Typhoons play an important role in the atmospheric circulation. Strong winds from typhoons excite ocean waves that accompany seismic noises. The primary and double frequency microseisms are dominant in frequencies of 0.05-0.1 Hz and 0.1-0.4 Hz. We investigate the characteristics of seismic noises from three typhoons that include Son-tinh in October 2012, Bopha in November 2012, and Soulik in July 2013. The peak wind speeds were 148-184 km/h, and the central atmospheric pressures reached 925-955 hPa. The typhoons passed through the western Pacific to South China Sea. We analyzed the temporal changes in spectral amplitudes of seismic noises during typhoon periods. The amplitude of seismic noises increases with decreasing distance between typhoon and seismic station. We observe large spectral amplitudes in frequencies of 0.1-0.4 Hz, which corresponds to the dominant frequencies of the double frequency microseism. The seismic energy in the frequency band of the primary frequency microseism was relatively weak. The seismic-noise amplitudes displays high correlation with the equivalent pressures on ocean bottom from Wave Watch III model. The observation suggests that the seismic noises may be originated from the ocean waves. The dominant frequency of seismic noises generally increases after passage across the stations due to the dispersion of ocean waves. Also, the dominant frequencies of seismic noises from the typhoons in the South China Sea appear to be higher than those from the typhoons in the Pacific. This feature may allow us to identify the origin of seismic noises and the nature of typhoons.

Modern Adaptive Analytics Approach to Lowering Seismic Network Detection Thresholds

NASA Astrophysics Data System (ADS)

Johnson, C. E.

2017-12-01

Modern seismic networks present a number of challenges, but perhaps most notably are those related to 1) extreme variation in station density, 2) temporal variation in station availability, and 3) the need to achieve detectability for much smaller events of strategic importance. The first of these has been reasonably addressed in the development of modern seismic associators, such as GLASS 3.0 by the USGS/NEIC, though some work still remains to be done in this area. However, the latter two challenges demand special attention. Station availability is impacted by weather, equipment failure or the adding or removing of stations, and while thresholds have been pushed to increasingly smaller magnitudes, new algorithms are needed to achieve even lower thresholds. Station availability can be addressed by a modern, adaptive architecture that maintains specified performance envelopes using adaptive analytics coupled with complexity theory. Finally, detection thresholds can be lowered using a novel approach that tightly couples waveform analytics with the event detection and association processes based on a principled repicking algorithm that uses particle realignment for enhanced phase discrimination.

Broadband seismic effects from train vibrations

NASA Astrophysics Data System (ADS)

Fuchs, Florian; Bokelmann, Götz

2017-04-01

Seismologists rarely study train induced vibrations which are mainly regarded an unwanted source of noise for classical seismological applications such as earthquake monitoring. A few seismological studies try to utilize train vibrations however as active sources, e.g. for subsurface imaging, but they do not focus on the characteristics of the train signal itself. Most available studies on train induced vibrations take an engineering approach and aim at better understanding the generation and short-distance propagation of train induced vibrations, mainly for mitigation and construction purposes. They mostly rely on numerical simulations and/or short-period or accelerometer recordings obtained directly on the train track or up to few hundred meters away and almost no studies exist with seismic recordings further away from the track. In some of these previous studies sharp and equidistant peaks are present in the vibration spectrum of heavy freight trains, but they do not attempt to explain them. Here we show and analyze various train vibration signals obtained from a set of seismic broadband stations installed in the context of the temporary, large-scale regional seismic network AlpArray. The geometrical restrictions of this seismic network combined with budget and safety considerations resulted in a number of broad-band instruments deployed in the vicinity of busy railway lines. On these stations we observe very characteristic seismic signals associated with different types of trains, typically showing pronounced equidistant spectral lines over a wide frequency range. In this study we analyze the nature of such signals and discuss if they are generated by a source effect or by wave propagation effects in near-surface soil layers.

Seismic array observations for monitoring phreatic eruptions in Iwojima Island, Japan

NASA Astrophysics Data System (ADS)

Ueda, H.; Kawaguchi, R.; Chiba, K.; Fujita, E.; Tanada, T.

2015-12-01

Iwojima is an active volcanic island located within a 10 km wide submarine caldera about 1250 km to the south of Tokyo, Japan. The volcanic activity is characterized by intensive earthquake activity associated with an island-wide uplift with high uplift rate (30~40 cm/year) and hydrothermal activity. In the last 10 years, phreatic eruptions took place in and near the island in 2012, 2013, and 2015. In such restless volcano, predictions and detections of occurrence points of phreatic eruptions are important for ensuring safety of residents. In the previous studies, we found that the earthquake activity of Iwojima highly correlates with the island wide large uplift, but the precursory activity of the phreatic eruption in 2012 was deviated from the correlation (Ueda et al. 2013 AGU Fall Meeting). For prediction of occurrence points of phreatic eruptions and investigation of the eruption mechanism, we began observation by seismic arrays at two areas in December 2014. The seismic arrays enable to locate epicenters of volcanic tremors, which are not well located by existing seismic stations. In May and June 2015, Japan Maritime Self-Defense Force stayed in Iwojima and a live camera of Japan Meteorological Agency found very small phreatic eruptions occurred at the northern beach. Existing seismic stations could not detect seismic signals related with the eruptions. The seismic array could detect weak seismic signals related with the eruptions. Although the seismic arrays could not detect precursory signals because of too small eruption, we expect the seismic arrays can detect precursory seismic signals suggesting occurrence points of small or medium-sized phreatic eruptions. The seismic arrays also detected epicenters of harmonic and monotonic tremors took place at an active fumarolic field in the north earthen part of Iwojima. The apparent velocity of seismic waves (~1km/s) strongly suggests that the tremors relate with hydrothermal activity near ground surface.

Seismic and deformation precursory to the small explosions of Marapi Volcano, West Sumatra, Indonesia

NASA Astrophysics Data System (ADS)

Hidayat, D.; Patria, C.; Gunawan, H.; Taisne, B.; Nurfiani, D.; Avila, E. J.

2015-12-01

Marapi Volcano is one of the active volcanoes of Indonesia located near the city of Bukittinggi, West Sumatra, Indonesia. Its activity is characterized by small vulcanian explosions with occasional VEI 2 producing tephra and pyroclastic flows. Due to its activity, it is being monitored by Centre for Volcanology and Geological Hazard Mitigation (CVGHM). Four seismic stations consists of 2 broadband and 2 short period instruments have been established since 2009. In collaboration with CVGHM, Earth Observatory of Singapore added 5 seismic stations around the volcano in 2014, initially with short period instruments but later upgraded to broadbands. We added one tilt station at the summit of Marapi. These seismic and tilt stations are telemetered by 5.8GHz radio to Marapi Observatory Post where data are archived and displayed for Marapi observers for their daily volcanic activity monitoring work. We also archive the data in the EOS and CVGHM main offices. Here we are presenting examples of seismic and deformation data from Marapi prior, during, and after the vulcanian explosion. Our study attempt to understand the state of the volcano based on monitoring data and in order to enable us to better estimate the hazards associated with the future eruptions of this or similar volcano.

Windrum: a program for monitoring seismic signals in real time

NASA Astrophysics Data System (ADS)

Giudicepietro, Flora

2017-04-01

Windrum is a program devote to monitor seismic signals arriving from remote stations in real time. Since 2000, the Osservatorio Vesuviano (INGV) uses the first version of Windrum to monitor the seismic activity of Mt. Vesuvius, Campi Flegrei, Ischia and Stromboli volcano. The program has been also used at the Observatory of Bukittinggi (Indonesia), at the offices of the Italian National Civil Protection, at the COA in Stromboli and at the Civil Protection Center of the municipality of Pozzuoli (Napoli, Italy). In addition, the Osservatorio Vesuviano regularly uses Windrum in educational events such as the Festival of Science in Genova (Italy), FuturoRemoto and other events organized by Città della Scienza in Naples (Italy). The program displays the seismic trace of one station on a monitor, using short packet of data (typically 1 or 2 seconds) received through UTC Internet protocol. The data packets are in Trace_buffer format, a native protocol of Earthworm seismic system that is widely used for the data transmission on Internet. Windrum allows the user to visualize 24 hours of signals, to zoom selected windows of data, in order to estimate the duration Magnitude (Md) of an earthquake, in an intercative way, and to generate graphic images for the web. Moreover, Windrum can exchange Internet messages with other copies of the same program to synchronize actions, such as to zoom the same window of data or mark the beginning of an earthquake on all active monitors simultaneously. Originally, in 2000, Windrum was developed in VB6. I have now developed a new version in VB.net, which goes beyond the obsolescence problems that were appearing. The new version supports the decoding of binary packets received by soket in a more flexible way, allowing the generation of graphic images in different formats. In addition, the new version allows a more flexible layout configuration, suitable for use on large screens with high resolution. Over the past 17 years the use of Windrum

Spatial Distribution of Seismic Anisotropy in the Crust in the Northeast Front Zone of Tibetan Plateau

NASA Astrophysics Data System (ADS)

Gao, Y.; Wang, Q.; SHI, Y.

2017-12-01

There are orogenic belts and strong deformation in northeastern zone of Tibetan Plateau. The media in crust and in the upper mantle are seismic anisotropic there. This study uses seismic records by permanent seismic stations and portable seismic arrays, and adopts analysis techniques on body waves to obtain spatial anisotropic distribution in northeastern front zone of Tibetan Plateau. With seismic records of small local earthquakes, we study shear-wave splitting in the upper crust. The polarization of fast shear wave (PFS) can be obtained, and PFS is considered parallel to the strike of the cracks, as well as the direction of maximum horizontal compressive stress. However, the result shows the strong influence from tectonics, such as faults. It suggests multiple-influence including stress and fault. Spatial distribution of seismic anisotropy in study zone presents the effect in short range. PFS at the station on the strike-slip fault is quite different to PFS at station just hundreds of meters away from the fault. With seismic records of teleseismic waveforms, we obtained seismic anisotropy in the whole crust by receiver functions. The PFS directions from Pms receiver functions show consistency, generally in WNW. The time-delay of slow S phases is significant. With seismic records of SKS, PKS and SKKS phases, we can detect seismic anisotropy in the upper mantle by splitting analysis. The fast directions of these phases also show consistency, generally in WNW, similar to those of receiver functions, but larger time-delays. It suggests significant seismic anisotropy in the crust and crustal deformation is coherent to that in the upper mantle.Seismic anisotropy in the upper crust, in the whole crust and in the upper mantle are discussed both in difference and tectonic implications [Grateful to the support by NSFC Project 41474032].

Filling the monitoring gaps across the US Arctic by permanently adopting USArray stations

NASA Astrophysics Data System (ADS)

Buurman, H.; West, M. E.

2017-12-01

The USArray project represents a truly unique opportunity to fundamentally change geophysical monitoring in the US Arctic. The addition of more than 200 stations capable of recording seismic, infrasound, ground temperature and meteorologic data has brought a diverse group of organizations to the table, fostering new connections and collaborations between scientists whose paths otherwise would not cross. With the array slated for removal beginning in 2019, there is a window of opportunity to advocate for permanently retaining a subset of the USArray stations. The Alaska Earthquake Center has drafted a plan to permanently adopt a subset of the USArray stations and maintain them as part of the seismic network in Alaska. The expanded seismic network would substantially improve on the Alaska Earthquake Center's ongoing mission to advance Alaska's resilience to earthquake hazards. By continuing to provide public climate and infrasound data, the Alaska Earthquake Center would also fill important gaps in the weather, wildfire and climate research monitoring networks across Alaska. The many challenges in adopting USArray stations include choosing which stations to retain, upgrading the power systems to have 24/7 data transmission through the long Alaskan winter months, and lowering the costs of continuous telemetry.

Fallon, Nevada FORGE Seismic Reflection Profiles

DOE Data Explorer

Blankenship, Doug; Faulds, James; Queen, John; Fortuna, Mark

2018-02-01

Newly reprocessed Naval Air Station Fallon (1994) seismic lines: pre-stack depth migrations, with interpretations to support the Fallon FORGE (Phase 2B) 3D Geologic model. Data along seven profiles (>100 km of total profile length) through and adjacent to the Fallon site were re-processed. The most up-to-date, industry-tested seismic processing techniques were utilized to improve the signal strength and coherency in the sedimentary, volcanic, and Mesozoic crystalline basement sections, in conjunction with fault diffractions in order to improve the identification and definition of faults within the study area.

Upper crustal structures beneath Yogyakarta imaged by ambient seismic noise tomography

NASA Astrophysics Data System (ADS)

Zulfakriza, Saygin, E.; Cummins, P.; Widiyantoro, S.; Nugraha, Andri Dian

2013-09-01

Delineating the upper crustal structures beneath Yogyakarta is necessary for understanding its tectonic setting. The presence of Mt. Merapi, fault line and the alluvial deposits contributes to the complex geology of Yogyakarta. Recently, ambient seismic noise tomography can be used to image the subsurface structure. The cross correlations of ambient seismic noise of pair stations were applied to extract the Green's function. The total of 27 stations from 134 seismic stations available in MERapi Amphibious EXperiment (MERAMEX) covering Yogyakarta region were selected to conduct cross correlation. More than 500 Rayleigh waves of Green's functions could be extracted by cross-correlating available the station pairs of short-period and broad-band seismometers. The group velocities were obtained by filtering the extracted Green's function between 0.5 and 20 s. 2-D inversion was applied to the retrieved travel times. Features in the derived tomographic images correlate with the surface geology of Yogyakarta. The Merapi active volcanoes and alluvial deposit in Yogyakarta are clearly described by lower group velocities. The high velocity anomaly contrasts which are visible in the images obtained from the period range between 1 and 5 s, correspond to subsurface imprints of fault that could be the Opak Fault.

A Study on distinguishing seismic waves caused by natural earthquakes and underground nuclear explosion within North Korean Context

NASA Astrophysics Data System (ADS)

Premlet, B.; Sabu, S.; Kamarudheen, R.; Subair, S.

2017-12-01

Since the first nuclear test on 15 July 1945 , there have been over 2,051 other weapon tests around the world . The waveforms of a natural earthquake which generates strong S waves and an underground explosion which is dominated by P waves were distinguished from the analysis of data corresponding to a 2005 M5.0 Earthquake and a 2016 North Korean nuclear test , both at similar distances from seismometer . Further differences between the seismograms were evaluated and successfully distinguished between the origins of the elastic waves through the data using Moment Tensor Solution using stations BJT , HIA and INCN . North Korea has developed a nuclear fuel cycle capability and has both plutonium and enriched uranium programs at Pyongyang . Seismic recordings of vertical ground motion at Global Seismographic Network station IC.MDJ of the 4 seismic events at Punggye-ri , North Korea , which occurred on the 9th of October 2006 , 25th of May 2009, 12th of February 2013 and on the 6th of January and 9th of September , 2016 were examined and the P waves of these seismic waves , which show very similar wave form , were inspected and compared to the seismic data of the latest underground nuclear test on the 3rd of September 2017 at 03:30 UTC at the same site which is many times more powerful than the previous tests . The country , which is the only nation to have tested nuclear weapons in this millennium , has successfully prevented the release of radioactive isotopes and hampered data collection but further studies were done using acoustic data which was analysed from sonograms of the 4 North Korean tests at station MDJ. The latest explosion data from 3rd September was also compared to 42 presumed underground explosions which occurred in China , India , the U.S.S.R , Iran , Turkey and recorded at Arkansas Seismic Network.

The Budget Guide to Seismic Network Management

NASA Astrophysics Data System (ADS)

Hagerty, M. T.; Ebel, J. E.

2007-05-01

Regardless of their size, there are certain tasks that all seismic networks must perform, including data collection and processing, earthquake location, information dissemination, and quality control. Small seismic networks are unlikely to possess the resources -- manpower and money -- required to do much in-house development. Fortunately, there are a lot of free or inexpensive software solutions available that are able to perform many of the required tasks. Often the available solutions are all-in-one turnkey packages designed and developed for much larger seismic networks, and the cost of adapting them to a smaller network must be weighed against the ease with which other, non-seismic software can be adapted to the same task. We describe here the software and hardware choices we have made for the New England Seismic Network (NESN), a sparse regional seismic network responsible for monitoring and reporting all seismicity within the New England region in the northeastern U.S. We have chosen to use a cost-effective approach to monitoring using free, off-the-shelf solutions where available (e.g., Earthworm, HYP2000) and modifying freeware solutions when it is easier than trying to adapt a large, complicated package. We have selected for use software that is: free, likely to receive continued support from the seismic or, preferably, larger internet community, and modular. Modularity is key to our design because it ensures that if one component of our processing system becomes obsolete, we can insert a suitable replacement with few modifications to the other modules. Our automated event detection, identification and location system is based on a wavelet transform analysis of station data that arrive continuously via TCP/IP transmission over the internet. Our system for interactive analyst review of seismic events and remote system monitoring utilizes a combination of Earthworm modules, Perl cgi-bin scripts, Java, and native Unix commands and can now be carried out via

RTX Correction Accuracy and Real-Time Data Processing of the New Integrated SeismoGeodetic System with Real-Time Acceleration and Displacement Measurements for Earthquake Characterization Based on High-Rate Seismic and GPS Data

NASA Astrophysics Data System (ADS)

Zimakov, L. G.; Raczka, J.; Barrientos, S. E.

2016-12-01

We will discuss and show the results obtained from an integrated SeismoGeodetic System, model SG160-09, installed in the Chile (Chilean National Network), Italy (University of Naples Network), and California. The SG160-09 provides the user high rate GNSS and accelerometer data, full epoch-by-epoch measurement integrity and the ability to create combined GNSS and accelerometer high-rate (200Hz) displacement time series in real-time. The SG160-09 combines seismic recording with GNSS geodetic measurement in a single compact, ruggedized case. The system includes a low-power, 220-channel GNSS receiver powered by the latest Trimble-precise Maxwell™6 technology and supports tracking GPS, GLONASS and Galileo signals. The receiver incorporates on-board GNSS point positioning using Real-Time Precise Point Positioning (PPP) technology with satellite clock and orbit corrections delivered over IP networks. The seismic recording includes an ANSS Class A, force balance accelerometer with the latest, low power, 24-bit A/D converter, producing high-resolution seismic data. The SG160-09 processor acquires and packetizes both seismic and geodetic data and transmits it to the central station using an advanced, error-correction protocol providing data integrity between the field and the processing center. The SG160-09 has been installed in three seismic stations in different geographic locations with different Trimble global reference stations coverage The hardware includes the SG160-09 system, external Zephyr Geodetic-2 GNSS antenna, both radio and high-speed Internet communication media. Both acceleration and displacement data was transmitted in real-time to the centralized Data Acquisition Centers for real-time data processing. Command/Control of the field station and real-time GNSS position correction are provided via the Pivot platform. Data from the SG160-09 system was used for seismic event characterization along with data from traditional seismic and geodetic stations

Detection and Identification of Small Seismic Events Following the 3 September 2017 UNT Around North Korean Nuclear Test Site

NASA Astrophysics Data System (ADS)

Kim, W. Y.; Richards, P. G.

2017-12-01

At least four small seismic events were detected around the North Korean nuclear test site following the 3 September 2017 underground nuclear test. The magnitude of these shocks range from 2.6 to 3.5. Based on their proximity to the September 3 UNT, these shocks may be considered as aftershocks of the UNT. We assess the best method to classify these small events based on spectral amplitude ratios of regional P and S wave from the shocks. None of these shocks are classified as explosion-like based on P/S spectral amplitude ratios. We examine additional possible small seismic events around the North Korean test site by using seismic data from stations in southern Korea and northeastern China including IMS seismic arrays, GSN stations, and regional network stations in the region.

Excitation of seismic waves by a tornado

NASA Astrophysics Data System (ADS)

Valovcin, A.; Tanimoto, T.; Twardzik, C.

2016-12-01

Tornadoes are among the most common natural disasters to occur in the United States. Various methods are currently used in tornado forecasting, including surface weather stations, weather balloons and satellite and Doppler radar. These methods work for detecting possible locations of tornadoes and funnel clouds, but knowing when a tornado has touched down still strongly relies on reports from spotters. Studying tornadoes seismically offers an opportunity to know when a tornado has touched down without requiring an eyewitness report. With the installation of Earthscope's Transportable Array (TA), there have been an increased number of tornadoes that have come within close range of seismometers. We have identified seismic signals corresponding to three tornadoes that occurred in 2011 in the central US. These signals were recorded by the TA station closest to each of the tornado tracks. For each tornado, the amplitudes of the seismic signals increase when the storm is in contact with the ground, and continue until the tornado lifts off some time later. This occurs at both high and low frequencies. In this study we will model the seismic signal generated by a tornado at low frequencies (below 0.1 Hz). We will begin by modeling the signal from the Joplin tornado, an EF5 rated tornado which occurred in Missouri on May 22, 2011. By approximating the tornado as a vertical force, we model the generated signal as the tornado moves along its track and changes in strength. By modeling the seismic waveform generated by a tornado, we can better understand the seismic-excitation process. It could also provide a way to quantitatively compare tornadoes. Additional tornadoes to model include the Calumet-El Reno-Piedmont-Guthrie (CEPG) and Chickasa-Blanchard-Newcastle (CBN) tornadoes, both of which occurred on May 24, 2011 in Oklahoma.

Seismic footprints of shallow dyke propagation at Etna, Italy

PubMed Central

Falsaperla, Susanna; Neri, Marco

2015-01-01

One of the key issues in forecasting volcanic eruptions is to detect signals that can track the propagation of dykes towards the surface. Continuous monitoring of active volcanoes helps significantly in achieving this goal. The seismic data presented here are unique, as they document surface faulting processes close (tens to a few hundred meters) to their source, namely the dyke tip. They originated nearby - and under - a seismic station that was subsequently destroyed by lava flows during eruptive activity at Etna volcano, Italy, in 2013. On February 20, a ~600 m-long and ~120 m wide NW-SE fracture field opened at an altitude between 2750 and 2900 m. The consequent rock dislocation caused the station to tilt and offset the seismic signal temporarily. Data acquisition continued until the arrival of the lava flow that led to the breakdown of the transmission system. Shallow ground fracturing and repeated low-frequency oscillations occurred during two stages in which the seismic signal underwent a maximum offset ~2.57 × 104 nm/s. Bridging instrumental recordings, fieldwork and conceptual modelling, these data are interpreted as the seismic footprints of a magmatic dyke intrusion that moved at speed ~0.02 m/s (first stage) and 0.46 m/s (second stage). PMID:26173557

Seismicity of the St. Lawrence paleorift faults overprinted by a meteorite impact crater: Implications for crustal strength based on new earthquake relocations in the Charlevoix Seismic Zone, Eastern Canada

NASA Astrophysics Data System (ADS)

Yu, H.; Harrington, R. M.; Liu, Y.; Lamontagne, M.; Pang, M.

2015-12-01

The Charlevoix Seismic Zone (CSZ), located along the St. Lawrence River (SLR) ~100 km downstream from Quebec City, is the most active seismic zone in eastern Canada with five historic earthquakes of M 6-7 and ~ 200 events/year reported by the Canadian National Seismograph Network. Cataloged earthquake epicenters outline two broad linear zones along the SLR with little shallow seismicity in between. Earthquakes form diffuse clusters between major dipping faults rather than concentrating on fault planes. Detailed fault geometry in the CSZ is uncertain and the effect on local seismicity of a meteorite impact structure that overprints the paleorift faults remains ambiguous. Here we relocate 1639 earthquakes occurring in the CSZ between 01/1988 - 10/2010 using the double-difference relocation method HypoDD and waveforms primarily from 7 local permanent stations. We use the layered SLR north shore velocity model from Lamontagne (1999), and travel time differences based on both catalog and cross-correlated P and S-phase picks. Of the 1639 relocated earthquakes, 1236 (75.4%) satisfied selection criteria of horizontal and vertical errors less than 2 km and 1 km respectively. Cross-sections of relocated seismicity show hypocenters along distinct active fault segments. Earthquakes located beneath the north shore of the SLR are likely correlated with the NW Gouffre fault, forming a ~10 km wide seismic zone parallel to the river, with dip angle changing to near vertical at the northern edge of the impact zone. In contrast, seismicity beneath the SLR forms a diffuse cloud within the impact structure, likely representing a highly fractured volume. It further implies that faults could be locally weak and subject to high pore-fluid pressures. Seismicity outside the impact structure defines linear structures aligning with the Charlevoix fault. Relocated events of M > 4 all locate outside the impact structure, indicating they nucleated on the NE-SW-oriented paleorift faults.

Crustal Structure of Indonesia from Seismic Ambient Noise Tomography

NASA Astrophysics Data System (ADS)

Saygin, E.; Cummins, P. R.; Suhardjono, S.; Nishida, K.

2012-12-01

We image a region spanning from south Vietnam to north Australia using over 300 seismic stations by using ambient seismic noise cross-correlations. The backbone of the network is formed by using the broadband seismograph network of Indonesia with over 160 stations serving as mid-tie point in the region. The retrieved Green's functions from the cross-correlation of continuously recorded seismic ambient noise at the stations are used to perform surface wave dispersion analysis. We apply a multiple filter approach to measure the phase and group velocity dispersion of Rayleigh wave component of Green's functions. The traveltime information derived from the dispersion is then used in a nonlinear tomographic approach to map the velocity perturbation of the region. The forward problem for the tomographic imaging can accurately track the evolution of a wavefront in highly heterogeneous media. Therefore the highly complex velocity distribution of the region is accurately reflected into the forward calculations used in the inversion. In general, accretionary prisms in the region are marked with quite low group and phase velocities with perturbations up to 50%. Active volcanoes in Sumatra and Java islands are also marked with low velocities. Rajang delta in north-west Kalimantan and thick sediments in South China Sea are imaged with low velocities.

Seismic Wave Velocity in the Subducted Oceanic Crust from Autocorrelation of Tectonic Tremor Signals

NASA Astrophysics Data System (ADS)

Ducellier, A.; Creager, K.

2017-12-01

Hydration and dehydration of minerals in subduction zones play a key role in the geodynamic processes that generate seismicity and that allow tectonic plates to subduct. Detecting the presence of water in the subducted plate is thus crucial to better understand the seismogenesis and the consequent seismic hazard. A landward dipping, low velocity layer has been detected in most subduction zones. In Cascadia, this low velocity zone is characterized by a low S-wave velocity and a very high Poisson's ratio, which has been interpreted as high pore-fluid pressure in the upper half part of the subducted oceanic crust. Most previous studies were based on seismic reflection imaging, receiver function analysis, or body wave tomography, with seismic sources located far from the low velocity zone. In contrast, the sources of the tectonic tremors generated during Episodic Tremor and Slip (ETS) events are located on the plate boundary. As the sources of the tremors are much closer to the low velocity zone, seismic waves recorded during ETS events should illuminate the area with greater precision. Most methods to detect and locate tectonic tremors and low-frequency earthquakes are based on the cross correlation of seismic signals; either signals at the same station for different events, or the same event at different stations. We use the autocorrelation of the seismic signal recorded by eight arrays of stations, located in the Olympic Peninsula, Washington. Each tremor, assumed to be on the plate boundary, generates a direct wave and reflected and converted waves from both the strong shear-wave velocity contrast in the mid-oceanic crust, and from the Moho of the subducted oceanic crust. The time lag between the arrivals of these different waves at a seismic station corresponds to a peak of amplitude on the autocorrelation signals. Using the time lags observed for different locations of the tremor source, we intend to invert for the seismic wave velocity of the subducted oceanic

Lunar seismicity and tectonics

NASA Technical Reports Server (NTRS)

Lammlein, D. R.

1977-01-01

Results are presented for an analysis of all moonquake data obtained by the Apollo seismic stations during the period from November 1969 to May 1974 and a preliminary analysis of critical data obtained in the interval from May 1974 to May 1975. More accurate locations are found for previously located moonquakes, and additional sources are located. Consideration is given to the sources of natural seismic signals, lunar seismic activity, moonquake periodicities, tidal periodicities in moonquake activity, hypocentral locations and occurrence characteristics of deep and shallow moonquakes, lunar tidal control over moonquakes, lunar tectonism, the locations of moonquake belts, and the dynamics of the lunar interior. It is concluded that: (1) moonquakes are distributed in several major belts of global extent that coincide with regions of the youngest and most intense volcanic and tectonic activity; (2) lunar tides control both the small quakes occurring at great depth and the larger quakes occurring near the surface; (3) the moon has a much thicker lithosphere than earth; (4) a single tectonic mechanism may account for all lunar seismic activity; and (5) lunar tidal stresses are an efficient triggering mechanism for moonquakes.

Ambient seismic noise study in Taiwan for two different scale arrays

NASA Astrophysics Data System (ADS)

Huang, Y.; Yao, H.; Liang, W.; Huang, B.; Wen, K.; Huang, W.; van der Hilst, R. D.

2008-12-01

It has been demonstrated that Time Domain Empirical Green's Function (TDEGF) from ambient seismic noise cross-correlation can be used to investigate crustal velocity structure from many studies around the world. For surface wave tomographic studies from ambient noise, the maximum exploring depth depends on the aperture of receiver array and the lateral resolution relies on the density of station-pair paths. To decipher subsurface structures in various scales, researchers can utilize some existing continuous-recording seismic stations and/or deploy a newly dense receiver array in the study region. In this study, we perform tomographic applications of ambient seismic noise analysis in Taiwan region for two arrays with very different scales. Taiwan is located at a complex convergent plate boundary zone where the Philippine Sea plate interacts with the Eurasian plate. As a result, the lateral velocity variations show dramatic patterns among different geologic provinces. In the past decade, many continuous-recording broadband stations have already been set up to monitor earthquake activities in the Taiwan region. The BATS (Broadband Array in Taiwan for Seismology) network is being operated by the Institute of Earth Sciences, Academia Sinica (IESAS) since 1994. Currently, there are 20 permanent stations covering approximately 350 km by 400 km area around Taiwan, including some remote islets. In this study we selected 7 years data (2000-2006) from BATS to get the TDEGFs which were then used to measure inter-station phase velocities in the period band 5-30s. Finally we then constructed 2D phase velocity maps. At shorter periods (5-10s), phase velocity distribution can compare well with surface geology. At longer periods (14-22s), there is a saxophone shape low velocity zone beneath the Taiwan Island. Taipei Basin is a high-level artificial noise metropolis with a nearly triangular shape basin located close to northern tip of Taiwan with area just around 20 km by 20 km

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

The underground seismic array of Gran Sasso (UNDERSEIS), central Italy

NASA Astrophysics Data System (ADS)

Scarpa, R.; Muscente, R.; Tronca, F.; Fischione, C.; Rotella, P.; Abril, M.; Alguacil, G.; Martini, M.; de Cesare, W.

2003-04-01

Since early May, 2002, a small aperture seismic array has been installed in the underground Physics Laboratories of Gran Sasso, located near seismic active faults of central Apennines, Italy. This array is presently composed by 21 three-component short period seismic stations (Mark L4C-3D), with average distance 90 m and semi-circular aperture of 400 m x 600 m. It is intersecting a main seismogenic fault where the presence of slow earthquakes has been recently detected through two wide band geodetic laser interferometers. The underground Laboratories are shielded by a limestone rock layer having 1400 m thickness. Each seismometer is linked, through a 24 bits A/D board, to a set of 6 industrial PC via a serial RS-485 standard. The six PC transmit data to a server through an ethernet network. Time syncronization is provided by a Master Oscillator controlled by an atomic clock. Earthworm package is used for data selection and transmission. High quality data have been recorded since May 2002, including local and regional earthquakes. In particular the 31 October, 2002, Molise (Mw=5.8 earthquake) and its aftershocks have been recorded at this array. Array techniques such as polarisation and frequency-slowness analyses with the MUSIC noise algorithm indicate the high performance of this array, as compared to the national seismic network, for identifying the basic source parameters for earthquakes located at distance of few hundreds of km.

Evaluation of potential surface rupture and review of current seismic hazards program at the Los Alamos National Laboratory. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1991-12-09

This report summarizes the authors review and evaluation of the existing seismic hazards program at Los Alamos National Laboratory (LANL). The report recommends that the original program be augmented with a probabilistic analysis of seismic hazards involving assignment of weighted probabilities of occurrence to all potential sources. This approach yields a more realistic evaluation of the likelihood of large earthquake occurrence particularly in regions where seismic sources may have recurrent intervals of several thousand years or more. The report reviews the locations and geomorphic expressions of identified fault lines along with the known displacements of these faults and last knowmore » occurrence of seismic activity. Faults are mapped and categorized into by their potential for actual movement. Based on geologic site characterization, recommendations are made for increased seismic monitoring; age-dating studies of faults and geomorphic features; increased use of remote sensing and aerial photography for surface mapping of faults; the development of a landslide susceptibility map; and to develop seismic design standards for all existing and proposed facilities at LANL.« less

The AlpArray-CASE project: temporary broadband seismic network deployment and characterization

NASA Astrophysics Data System (ADS)

Dasović, Iva; Molinari, Irene; Stipčević, Josip; Šipka, Vesna; Salimbeni, Simone; Jarić, Dejan; Prevolnik, Snježan; Kissling, Eduard; Clinton, John; Giardini, Domenico

2017-04-01

While the northern part of the Adriatic microplate will be accurately imaged within the AlpArray project, its central and southern parts deserve detailed studies to obtain a complete picture of its structure and evolution. The Adriatic microplate forms the upper plate in the Western and Central Alps whereas it forms the lower plate in the Apennines and the Dinarides. However, the tectonics of Adriatic microplate is not well constrained and remains controversial, especially with regard to its contact with the Dinarides. The primary goal of the Central Adriatic Seismic Experiment (CASE) is to provide high quality seismological data and to shed light on seismicity and 3D lithospheric structure of the central Adriatic microplate and its boundaries. The CASE project is an international AlpArray Complementary Experiment carried out by four institutions: Department of Earth Sciences and Swiss Seismological Service of ETH Zürich (CH), Department of Geophysics and Croatian Seismological Service of Faculty of Science at University of Zagreb (HR), Republic Hydrometeorological Service of Republic of Srpska (BIH) and Istituto Nazionale di Geofisica e Vulcanologia (I). It establishes a temporary seismic network, expected to be operational at least for one year, composed by existing permanent and temporary seismic stations operated by the institutions involved and newly deployed temporary seismic stations, installed in November and December 2016, provided by ETH Zürich and INGV: five in Croatia, four in Bosnia and Herzegovina and two in Italy. In this work, we present stations sites and settings and discuss their characteristics in terms of site-effects and noise level of each station. In particular, we analyse the power spectral density estimates in order to investigate major sources of noise and background noise.

Monitoring El Hierro submarine volcanic eruption events with a submarine seismic array

NASA Astrophysics Data System (ADS)

Jurado, Maria Jose; Molino, Erik; Lopez, Carmen

2013-04-01

A submarine volcanic eruption took place near the southernmost emerged land of the El Hierro Island (Canary Islands, Spain), from October 2011 to February 2012. The Instituto Geografico Nacional (IGN) seismic stations network evidenced seismic unrest since July 2012 and was a reference also to follow the evolution of the seismic activity associated with the volcanic eruption. From the beginning of the eruption a geophone string was installed less than 2 km away from the new volcano, next to La Restinga village shore, to record seismic activity related to the volcanic activity, continuously and with special interest on high frequency events. The seismic array was endowed with 8, high frequency, 3 component, 250 Hz, geophone cable string with a separation of 6 m between them. The analysis of the dataset using spectral techniques allows the characterization of the different phases of the eruption and the study of its dynamics. The correlation of the data analysis results with the observed sea surface activity (ash and lava emission and degassing) and also with the seismic activity recorded by the IGN field seismic monitoring system, allows the identification of different stages suggesting the existence of different signal sources during the volcanic eruption and also the posteruptive record of the degassing activity. The study shows that the high frequency capability of the geophone array allow the study of important features that cannot be registered by the standard seismic stations. The accumulative spectral amplitude show features related to eruptive changes.

Hydraulically Induced Seismicity in South-Eastern Brazil Linked to Water Wells

NASA Astrophysics Data System (ADS)

Convers, J.; Assumpcao, M.; Barbosa, J. R.

2017-12-01

While hydraulic stimulus on seismic activity is most commonly associated with hydraulic fracturing processes, we find in SE Brazil a rare case of seismicity influenced by hydraulic stimulation linked to seasonal rain and water wells in a farming area. These are thought to be the main factors influencing the seasonal seismicity activity in Jurupema, a farming town located in the interior of the state of Sao Paulo, southern Brazil. With temporary seismic station deployments during 2016 and 2017, we analyze the seismicity in this area, its temporal and spatial distribution, and its association with the drilling of ground water wells in this particular area. In a region where water wells are often drilled to provide irrigation for farming, these are often perforated down to about 100 m depth, penetrating below the uppermost sandstone rock layer ( 50 m) into a fractured basaltic rock layer, reaching the confined aquifer within it. While the wells are constantly pumped during the dry season, during the course of the rainy season (when these are not being used), a possible infiltration into the confined basaltic aquifer, from both the rainwater and the upper sandstone aquifer, adds changes to the pore pressure of the fractured rock, and modifies the tectonic pre-stress conditions, to facilitate stress release mechanisms in pre-existing faults and cracks. With our temporary seismic station deployments, we not only examine the seismicity in this region during both 2016 and 2017, but we additionally compare its characteristics to the nearby Bebedouro case in an apparent induced seismic case of analogous source, and seismic activity with magnitudes up to 2.9 occurring between 2005 and 2010.

Seismic monitoring at Cascade Volcanic Centers, 2004?status and recommendations

USGS Publications Warehouse

Moran, Seth C.

2004-01-01

The purpose of this report is to assess the current (May, 2004) status of seismic monitoring networks at the 13 major Cascade volcanic centers. Included in this assessment are descriptions of each network, analyses of the ability of each network to detect and to locate seismic activity, identification of specific weaknesses in each network, and a prioritized list of those networks that are most in need of additional seismic stations. At the outset it should be recognized that no Cascade volcanic center currently has an adequate seismic network relative to modern-day networks at Usu Volcano (Japan) or Etna and Stromboli volcanoes (Italy). For a system the size of Three Sisters, for example, a modern-day, cutting-edge seismic network would ideally consist of a minimum of 10 to 12 short-period three-component seismometers (for determining particle motions, reliable S-wave picks, moment tensor inversions, fault-plane solutions, and other important seismic parameters) and 7 to 10 broadband sensors (which, amongst other considerations, enable detection and location of very long period (VLP) and other low-frequency events, moment tensor inversions, and, because of their wide dynamic range, on-scale recording of large-amplitude events). Such a dense, multi component seismic network would give the ability to, for example, detect in near-real-time earthquake migrations over a distance of ~0.5km or less, locate tremor sources, determine the nature of a seismic source (that is, pure shear, implosive, explosive), provide on-scale recordings of very small and very large-amplitude seismic signals, and detect localized changes in seismic stress tensor orientations caused by movement of magma bodies. However, given that programmatic resources are currently limited, installation of such networks at this time is unrealistic. Instead, this report focuses on identifying what additional stations are needed to guarantee that anomalous seismicity associated with volcanic unrest will be

Identifying the Transition Zone Between East and West Dharwar Craton by Seismic Imaging

NASA Astrophysics Data System (ADS)

Ashish; Parvez, Imtiyaz A.

2018-01-01

The data from 12 temporary broadband seismic stations operated across east-west corridor in Dharwar region of Indian Peninsula along with ten other seismic stations operated by CSIR National Geophysical Research Institute (NGRI) in the region have been analysed that provide high-resolution image of southern Dharwar crust. Crust along the corridor is imaged by receiver function H-k stacking, common conversion point stacking using data from 22 sites in combination with joint inversion modeling of receiver functions and Rayleigh wave group velocity dispersion curves. The velocity image reveals thinner crust (36-38 km) except one site (coinciding with Cuddapah basin on the surface) in East Dharwar Craton (EDC), while crust beneath the West Dharwar Craton (WDC) is thicker (46-50 km). This study also observed a transition zone between EDC and WDC starting west of Closepet granite to the east of Chitradurga Schist Belt (CSB), which shows diffused Moho with a thickness of 40-44 km. Chitradurga Schist Belt is identified as the contact between Mesoarchean (WDC) and Neoarchean (EDC) crustal blocks. The lowermost part of the crust (V_s > 4.0) is thin (2-6 km) beneath EDC, intermediate (6-8 km) beneath transition zone and thicker (14-30 km) beneath WDC across the profile.

Hawaiian Volcano Observatory Seismic Data, January to December 2007

USGS Publications Warehouse

Nakata, Jennifer S.; Okubo, Paul G.

2008-01-01

The U.S. Geological Survey (USGS), Hawaiian Volcano Observatory (HVO) summary presents seismic data gathered during the year. The seismic summary is offered without interpretation as a source of preliminary data and is complete in that most data for events of M=1.5 are included. All latitude and longitude references in this report are stated in Old Hawaiian Datum. The HVO summaries have been published in various forms since 1956. Summaries prior to 1974 were issued quarterly, but cost, convenience of preparation and distribution, and the large quantities of data necessitated an annual publication, beginning with Summary 74 for the year 1974. Beginning in 2004, summaries are simply identified by the year, rather than by summary number. Summaries originally issued as administrative reports were republished in 2007 as Open-File Reports. All the summaries since 1956 are listed at http://geopubs.wr.usgs.gov/ (last accessed September 30, 2008). In January 1986, HVO adopted CUSP (California Institute of Technology USGS Seismic Processing). Summary 86 includes a description of the seismic instrumentation, calibration, and processing used in recent years. The present summary includes background information about the seismic network to provide the end user an understanding of the processing parameters and how the data were gathered. A report by Klein and Koyanagi (1980) tabulates instrumentation, calibration, and recording history of each seismic station in the network. It is designed as a reference for users of seismograms and phase data and includes and augments the information in the station table in this summary.

Construction and development of IGP DMC of China National Seismological Network

NASA Astrophysics Data System (ADS)

Zheng, X.; Zheng, J.; Lin, P.; Yao, Z.; Liang, J.

2011-12-01

In 2003, CEA (China Earthquake Administration) commenced the construction of China Digital Seismological Observation Network. By the end of 2007, a new-generation digital seismological observation system had been established, which consists of 1 National Seismic Network, 32 regional seismic networks, 2 small-aperture seismic arrays, 6 volcano monitoring networks and 19 mobile seismic networks, as well as CENC (China Earthquake Network Center) DMC (Data Management Centre) and IGP (Institute of Geophysics) DMC. Since then, the seismological observation system of China has completely entered a digital time. For operational, data backup and data security considerations, the DMC at the Institute of Geophysics (IGP), CEA was established at the end of 2007. IGP DMC now receives and archives waveform data from more than 1000 permanent seismic stations around China in real-time. After the great Wenchuan and Yushu earthquakes, the real-time waveform data from 56 and 8 portable seismic stations deployed in the aftershock area are added to IGP DMC. The technical system of IGP DMC is designed to conduct data management, processing and service through the network of CEA. We developed and integrated a hardware system with high-performance servers, large-capacity disc arrays, tape library and other facilities, as well as software packages for real-time waveform data receiving, storage, quality control, processing and service. Considering the demands from researchers for large quantities of seismic event waveform data, IGP DMC adopts an innovative "user order" method to extract event waveform data. Users can specify seismic stations, epicenter distance and record length. In a short period of 3 years, IGP DMC has supplied about 350 Terabytes waveform data to over 200 researches of more than 40 academic institutions. According to incomplete statistics, over 40 papers have been published in professional journals, in which 30 papers were indexed by SCI. Now, IGP DMC has become an

An Adaptable Seismic Data Format for Modern Scientific Workflows

NASA Astrophysics Data System (ADS)

Smith, J. A.; Bozdag, E.; Krischer, L.; Lefebvre, M.; Lei, W.; Podhorszki, N.; Tromp, J.

2013-12-01

Data storage, exchange, and access play a critical role in modern seismology. Current seismic data formats, such as SEED, SAC, and SEG-Y, were designed with specific applications in mind and are frequently a major bottleneck in implementing efficient workflows. We propose a new modern parallel format that can be adapted for a variety of seismic workflows. The Adaptable Seismic Data Format (ASDF) features high-performance parallel read and write support and the ability to store an arbitrary number of traces of varying sizes. Provenance information is stored inside the file so that users know the origin of the data as well as the precise operations that have been applied to the waveforms. The design of the new format is based on several real-world use cases, including earthquake seismology and seismic interferometry. The metadata is based on the proven XML schemas StationXML and QuakeML. Existing time-series analysis tool-kits are easily interfaced with this new format so that seismologists can use robust, previously developed software packages, such as ObsPy and the SAC library. ADIOS, netCDF4, and HDF5 can be used as the underlying container format. At Princeton University, we have chosen to use ADIOS as the container format because it has shown superior scalability for certain applications, such as dealing with big data on HPC systems. In the context of high-performance computing, we have implemented ASDF into the global adjoint tomography workflow on Oak Ridge National Laboratory's supercomputer Titan.

Data Analysis of Seismic Sequence in Central Italy in 2016 using CTBTO- International Monitoring System

NASA Astrophysics Data System (ADS)

Mumladze, Tea; Wang, Haijun; Graham, Gerhard

2017-04-01

The seismic network that forms the International Monitoring System (IMS) of the Comprehensive Nuclear-test-ban Treaty Organization (CTBTO) will ultimately consist of 170 seismic stations (50 primary and 120 auxiliary) in 76 countries around the world. The Network is still under the development, but currently more than 80% of the network is in operation. The objective of seismic monitoring is to detect and locate underground nuclear explosions. However, the data from the IMS also can be widely used for scientific and civil purposes. In this study we present the results of data analysis of the seismic sequence in 2016 in Central Italy. Several hundred earthquakes were recorded for this sequence by the seismic stations of the IMS. All events were accurately located the analysts of the International Data Centre (IDC) of the CTBTO. In this study we will present the epicentral and magnitude distribution, station recordings and teleseismic phases as obtained from the Reviewed Event Bulletin (REB). We will also present a comparison of the database of the IDC with the databases of the European-Mediterranean Seismological Centre (EMSC) and U.S. Geological Survey (USGS). Present work shows that IMS data can be used for earthquake sequence analyses and can play an important role in seismological research.

Seismic unrest at Katla Volcano- southern Iceland

NASA Astrophysics Data System (ADS)

jeddi, zeinab; Tryggvason, Ari; Gudmundsson, Olafur; Bödvarsson, Reynir; SIL Seismology Group

2014-05-01

Katla volcano is located on the propagating Eastern Volcanic Zone (EVZ) in South Iceland. It is located beneath Mýrdalsjökull ice-cap which covers an area of almost 600 km2, comprising the summit caldera and the eruption vents. 20 eruptions between 930 and 1918 with intervals of 13-95 years are documented at Katla which is one of the most active subglacial volcanoes in Iceland. Eruptions at Katla are mainly explosive due to the subglacial mode of extrusion and produce high eruption columns and catastrophic melt water floods (jökulhlaups). The present long Volcanic repose (almost 96 years) at Katla, the general unrest since 1955, and the 2010 eruption of the neighbouring Eyjafjallajökull volcano has prompted concerns among geoscientists about an imminent eruption. Thus, the volcano has been densely monitored by seismologists and volcanologists. The seismology group of Uppsala University as a partner in the Volcano Anatomy (VA) project in collaboration with the University of Iceland and the Icelandic Meteorological Office (IMO) installed 9 temporary seismic stations on and around the Mýrdalsjökull glacier in 2011. Another 10 permanent seismic stations are operated by IMO around Katla. The project's data collection is now finished and temporary stations were pulled down in August 2013. According to seismicity maps of the whole recording period, thousands of microearthquakes have occurred within the caldera region. At least three different source areas are active in Katla: the caldera region, the western Godaland region and a small cluster at the southern rim of Mýrdalsjökull near the glacial stream of Hafursarjökull. Seismicity in the southern flank has basically started after June 2011. The caldera events are mainly volcano-tectonic, while western and southern events are mostly long period (lp) and can be related to glacial or magmatic movement. One motivation of the VA Katla project is to better understand the physical mechanism of these lp events. Changes

Non Conventional Seismic Events Along the Himalayan Arc Detected in the Hi-Climb Dataset

NASA Astrophysics Data System (ADS)

Vergne, J.; Nàbĕlek, J. L.; Rivera, L.; Bollinger, L.; Burtin, A.

2008-12-01

From September 2002 to August 2005, more than 200 broadband seismic stations were operated across the Himalayan arc and the southern Tibetan plateau in the framework of the Hi-Climb project. Here, we take advantage of the high density of stations along the main profile to look for coherent seismic wave arrivals that can not be attributed to ordinary tectonic events. An automatic detection algorithm is applied to the continuous data streams filtered between 1 and 10 Hz, followed by a visual inspection of all detections. We discovered about one hundred coherent signals that cannot be attributed to local, regional or teleseismic earthquakes and which are characterized by emergent arrivals and long durations ranging from one minute to several hours. Most of these non conventional seismic events have a low signal to noise ratio and are thus only observed above 1 Hz in the frequency band where the seismic noise is the lowest. However, a small subset of them are strong enough to be observed in a larger frequency band and show an enhancement of long periods compared to standard earthquakes. Based on the analysis of the relative amplitude measured at each station or, when possible, on the correlation of the low frequency part of the signals, most of these events appear to be located along the High Himalayan range. But, because of their emergent character and the main orientation of the seismic profile, their longitude and depth remain poorly constrained. The origin of these non conventional seismic events is still unsealed but their seismic signature shares several characteristics with non volcanic tremors, glacial earthquakes and/or debris avalanches. All these phenomena may occur along the Himalayan range but were not seismically detected before. Here we discuss the pros and cons for each of these postulated candidates based on the analysis of the recorded waveforms and slip models.

Report of the Committee on the Space Station of the National Research Council

NASA Technical Reports Server (NTRS)

1987-01-01

The Space Station Program will be the most ambitious space project the nation has ever undertaken; will require tens of billions of dollars; and will entwine for many years the space program with those of international partners. It must have enduring stable support across administrations, and the support must be generous. The current Space Shuttle is barely adequate for the limited purpose of deploying the Space Station, and it is inadequate to meet broader national needs in space. The Committee recommends in the strongest terms that the Shuttle be upgraded with new improved solid rocket motors, that it be supplemented with expendable launch vehicles, and that a heavy lift launch vehicle be developed for use in the latter half of the 1990s. The Committee strongly recommends that NASA prepare a new Space Station Program cost estimate in conjunction with the Program Requirements Review scheduled for early next year by NASA. The exercise should address the full range of uncertainties in the current Program, some of which are discussed in the report.

Operating a global seismic network - perspectives from the USGS GSN

NASA Astrophysics Data System (ADS)

Gee, L. S.; Derr, J. S.; Hutt, C. R.; Bolton, H.; Ford, D.; Gyure, G. S.; Storm, T.; Leith, W.

2007-05-01

The Global Seismographic Network (GSN) is a permanent digital network of state-of-the-art seismological and geophysical sensors connected by a global telecommunications network, serving as a multi-use scientific facility used for seismic monitoring for response applications, basic and applied research in solid earthquake geophysics, and earth science education. A joint program of the U.S. Geological Survey (USGS), the National Science Foundation, and Incorporated Research Institutions in Seismology (IRIS), the GSN provides near- uniform, worldwide monitoring of the Earth through 144 modern, globally distributed seismic stations. The USGS currently operates 90 GSN or GSN-affiliate stations. As a US government program, the USGS GSN is evaluated on several performance measures including data availability, data latency, and cost effectiveness. The USGS-component of the GSN, like the GSN as a whole, is in transition from a period of rapid growth to steady- state operations. The program faces challenges of aging equipment and increased operating costs at the same time that national and international earthquake and tsunami monitoring agencies place an increased reliance on GSN data. Data acquisition of the USGS GSN is based on the Quanterra Q680 datalogger, a workhorse system that is approaching twenty years in the field, often in harsh environments. An IRIS instrumentation committee recently selected the Quanterra Q330 HR as the "next generation" GSN data acquisition system, and the USGS will begin deploying the new equipment in the middle of 2007. These new systems will address many of the issues associated with the ageing Q680 while providing a platform for interoperability across the GSN.. In order to address the challenge of increasing operational costs, the USGS employs several tools. First, the USGS benefits from the contributions of local host institutions. The station operators are the first line of defense when a station experiences problems, changing boards

Recent Evolutions of the GEOSCOPE Broadband Seismic Observatory

NASA Astrophysics Data System (ADS)

Stutzmann, E.; Vallee, M.; Zigone, D.; Bonaime, S.; Thore, J. Y.; Pesqueira, F.; Pardo, C.; Bernard, A.; Maggi, A.; Vincent, D.; Sayadi, J.

2017-12-01

The GEOSCOPE observatory provides 36 years of continuous broadband data to the scientific community. The 32 operational GEOSCOPE stations are installed in 17 countries, across all continents and on islands throughout the oceans. They are equipped with three component very broadband seismometers (STS1 or STS2) and 24 or 26 bit digitizers (Q330HR). Seismometers are installed with warpless base plates, which decrease long period noise on horizontal components by up to 15dB. All stations send data in real time to the IPGP data center and are automatically transmitted to other data centers (IRIS-DMC and RESIF) and tsunami warning centers. Recent improvements include a new station in Wallis and Futuna (FUTU, South-Western Pacific Ocean) and the re-installation of WUS station in Western China. Data of the stations are technically validated by IPGP (25 stations) or EOST (6 stations) in order to check their continuity and integrity. A scientific data validation is also performed by analyzing seismic noise level of the continuous data and by comparing real and synthetic earthquake waveforms (body waves). After these validations, data are archived by the IPGP data center in Paris. They are made available to the international scientific community through different interfaces (see details on http://geoscope.ipgp.fr). All GEOSCOPE data are in miniseed format but using various conventions. An important technical work is done to homogenize the data miniseed formats of the whole GEOSCOPE database, in order to make easier the data duplication at the IRIS-DMC and RESIF data centers. The GEOSCOPE observatory also provides near-real time information on the World large seismicity (above magnitude 5.5-6) through the automated use of the SCARDEC method. Earthquake parameters (depth, moment magnitude, focal mechanism, source time function) are determined about 45 minutes after the occurrence of the event. A specific webpage is then generated, which also includes information for a non

The Apollo passive seismic experiment

NASA Technical Reports Server (NTRS)

Latham, G. V.; Dorman, H. J.; Horvath, P.; Ibrahim, A. K.; Koyama, J.; Nakamura, Y.

1979-01-01

The completed data set obtained from the 4-station Apollo seismic network includes signals from approximately 11,800 events of various types. Four data sets for use by other investigators, through the NSSDC, are in preparation. Some refinement of the lunar model based on seismic data can be expected, but its gross features remain as presented two years ago. The existence of a small, molten core remains dependent upon the analysis of signals from a single, far-side impact. Analysis of secondary arrivals from other sources may eventually resolve this issue, as well as continued refinement of the magnetic field measurements. Evidence of considerable lateral heterogeneity within the moon continues to build. The mystery of the much meteoroid flux estimate derived from lunar seismic measurements, as compared with earth-based estimates, remains; although, significant correlations between terrestrial and lunar observations are beginning to emerge.

The AlpArray Seismic Network: current status and next steps

NASA Astrophysics Data System (ADS)

Hetényi, György; Molinari, Irene; Clinton, John; Kissling, Edi

2016-04-01

The AlpArray initiative (http://www.alparray.ethz.ch) is a large-scale European collaboration to study the entire Alpine orogen at high resolution and in 3D with a large variety of geoscientific methods. The core element of the initiative is an extensive and dense broadband seismological network, the AlpArray Seismic Network (AASN), which complements the permanent seismological stations to ensure homogeneous coverage of the greater Alpine area. The some 260 temporary stations of the AlpArray Seismic Network are operated as a joint effort by a number of institutions from Austria, Bosnia-Herzegovina, Croatia, Czech Republic, France, Germany, Hungary, Italy, Slovakia and Switzerland. The first stations were installed in Spring 2015 and the full AASN is planned to be operational by early Summer 2016. In this poster we present the actual status of the deployment, the effort undertaken by the contributing groups, station performance, typical noise levels, best practices in installation as well as in data management, often encountered challenges, and planned next steps including the deployment of ocean bottom seismometers in the Ligurian Sea.

RMT focal plane sensitivity to seismic network geometry and faulting style

USGS Publications Warehouse

Johnson, Kendra L.; Hayes, Gavin; Herrmann, Robert B.; Benz, Harley M.; McNamara, Daniel E.; Bergman, Eric A.

2016-01-01

Modern tectonic studies often use regional moment tensors (RMTs) to interpret the seismotectonic framework of an earthquake or earthquake sequence; however, despite extensive use, little existing work addresses RMT parameter uncertainty. Here, we quantify how network geometry and faulting style affect RMT sensitivity. We examine how data-model fits change with fault plane geometry (strike and dip) for varying station configurations. We calculate the relative data fit for incrementally varying geometries about a best-fitting solution, applying our workflow to real and synthetic seismograms for both real and hypothetical station distributions and earthquakes. Initially, we conduct purely observational tests, computing RMTs from synthetic seismograms for hypothetical earthquakes and a series of well-behaved network geometries. We then incorporate real data and station distributions from the International Maule Aftershock Deployment (IMAD), which recorded aftershocks of the 2010 MW 8.8 Maule earthquake, and a set of regional stations capturing the ongoing earthquake sequence in Oklahoma and southern Kansas. We consider RMTs computed under three scenarios: (1) real seismic records selected for high data quality; (2) synthetic seismic records with noise computed for the observed source-station pairings and (3) synthetic seismic records with noise computed for all possible station-source pairings. To assess RMT sensitivity for each test, we observe the ‘fit falloff’, which portrays how relative fit changes when strike or dip varies incrementally; we then derive the ranges of acceptable strikes and dips by identifying the span of solutions with relative fits larger than 90 per cent of the best fit. For the azimuthally incomplete IMAD network, Scenario 3 best constrains fault geometry, with average ranges of 45° and 31° for strike and dip, respectively. In Oklahoma, Scenario 3 best constrains fault dip with an average range of 46°; however, strike is best constrained

Explosion Source Location Study Using Collocated Acoustic and Seismic Networks in Israel

NASA Astrophysics Data System (ADS)

Pinsky, V.; Gitterman, Y.; Arrowsmith, S.; Ben-Horin, Y.

2013-12-01

We explore a joined analysis of seismic and infrasonic signals for improvement in automatic monitoring of small local/regional events, such as construction and quarry blasts, military chemical explosions, sonic booms, etc. using collocated seismic and infrasonic networks recently build in Israel (ISIN) in the frame of the project sponsored by the Bi-national USA-Israel Science Foundation (BSF). The general target is to create an automatic system, which will provide detection, location and identification of explosions in real-time or close-to-real time manner. At the moment the network comprises 15 stations hosting a microphone and seismometer (or accelerometer), operated by the Geophysical Institute of Israel (GII), plus two infrasonic arrays, operated by the National Data Center, Soreq: IOB in the South (Negev desert) and IMA in the North of Israel (Upper Galilee),collocated with the IMS seismic array MMAI. The study utilizes a ground-truth data-base of numerous Rotem phosphate quarry blasts, a number of controlled explosions for demolition of outdated ammunitions and experimental surface explosions for a structure protection research, at the Sayarim Military Range. A special event, comprising four military explosions in a neighboring country, that provided both strong seismic (up to 400 km) and infrasound waves (up to 300 km), is also analyzed. For all of these events the ground-truth coordinates and/or the results of seismic location by the Israel Seismic Network (ISN) have been provided. For automatic event detection and phase picking we tested the new recursive picker, based on Statistically optimal detector. The results were compared to the manual picks. Several location techniques have been tested using the ground-truth event recordings and the preliminary results obtained have been compared to the ground-truth locations: 1) a number of events have been located as intersection of azimuths estimated using the wide-band F-K analysis technique applied to the

Long period seismic noise modulated by atmospheric tides

NASA Astrophysics Data System (ADS)

Custódio, Susana; Helffrich, George

2016-04-01

The amplitudes of long-period (LP) seismic noise often exhibit a daily modulation, which is particularly visible on data recorded by temporary stations and horizontal components. These daily variations of the LP noise have been associated with temperature fluctuations. Temperature has been suggested to affect the noise recorded by seismometers by means of thermal convection around the sensor or by causing thermally induced tilts. Recently, we observed a semi-diurnal (12.0 hr) modulation of LP seismic noise amplitudes in seismometers in Portugal, SW Europe. This modulation was associated with the variation of atmospheric pressure, the only environmental signal to display a dominant 12-hr periodicity (at some locations). In this presentation we will present an analysis of this semi-diurnal modulation of long-period seismic noise. We show that the modulation: 1) is not instrument dependent, being recorded in a variety of sensors; 2) is observed in stations in mainland Portugal, Madeira island (N Atlantic), Florida (USA) and Mozambique, where it is strongest; 3) is seen only at a minority of sites without a clear geographical association, thus appearing to be strongly site-dependent; 5) is stronger during the Summer than during the Winter; and 6) is more clearly seen on vertical components. We will use data from the Transportable Array (EarthScope, USA) to investigate the admittance between LP seismic noise variations and co-located atmospheric pressure measurements.

Detection and interpretation of seismoacoustic events at German infrasound stations

NASA Astrophysics Data System (ADS)

Pilger, Christoph; Koch, Karl; Ceranna, Lars

2016-04-01

Three infrasound arrays with collocated or nearby installed seismometers are operated by the Federal Institute for Geosciences and Natural Resources (BGR) as the German National Data Center (NDC) for the verification of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). Infrasound generated by seismoacoustic events is routinely detected at these infrasound arrays, but air-to-ground coupled acoustic waves occasionally show up in seismometer recordings as well. Different natural and artificial sources like meteoroids as well as industrial and mining activity generate infrasonic signatures that are simultaneously detected at microbarometers and seismometers. Furthermore, many near-surface sources like earthquakes and explosions generate both seismic and infrasonic waves that can be detected successively with both technologies. The combined interpretation of seismic and acoustic signatures provides additional information about the origin time and location of remote infrasound events or about the characterization of seismic events distinguishing man-made and natural origins. Furthermore, seismoacoustic studies help to improve the modelling of infrasound propagation and ducting in the atmosphere and allow quantifying the portion of energy coupled into ground and into air by seismoacoustic sources. An overview of different seismoacoustic sources and their detection by German infrasound stations as well as some conclusions on the benefit of a combined seismoacoustic analysis are presented within this study.

Improving Seismic Data Accessibility and Performance Using HDF Containers

NASA Astrophysics Data System (ADS)

Evans, B. J. K.; Wang, J.; Yang, R.

2017-12-01

The performance of computational geophysical data processing and forward modelling relies on both computational and data. Significant efforts on developing new data formats and libraries have been made the community, such as IRIS/PASSCAL and ASDF in data, and programs and utilities such as ObsPy and SPECFEM. The National Computational Infrastructure hosts a national significant geophysical data collection that is co-located with a high performance computing facility and provides an opportunity to investigate how to improve the data formats from both a data management and a performance point of view. This paper investigates how to enhance the data usability in several perspectives: 1) propose a convention for the seismic (both active and passive) community to improve the data accessibility and interoperability; 2) recommend the convention used in the HDF container when data is made available in PH5 or ASDF formats; 3) provide tools to convert between various seismic data formats; 4) provide performance benchmark cases using ObsPy library and SPECFEM3D to demonstrate how different data organization in terms of chunking size and compression impact on the performance by comparing new data formats, such as PH5 and ASDF to traditional formats such as SEGY, SEED, SAC, etc. In this work we apply our knowledge and experience on data standards and conventions, such as CF and ACDD from the climate community to the seismology community. The generic global attributes widely used in climate community are combined with the existing convention in the seismology community, such as CMT and QuakeML, StationXML, SEGY header convention. We also extend such convention by including the provenance and benchmarking records so that the r user can learn the footprint of the data together with its baseline performance. In practise we convert the example wide angle reflection seismic data from SEGY to PH5 or ASDF by using ObsPy and pyasdf libraries. It quantitatively demonstrates how the

The evolution of seismic monitoring systems at the Hawaiian Volcano Observatory: Chapter 2 in Characteristics of Hawaiian volcanoes

USGS Publications Warehouse

Okubo, Paul G.; Nakata, Jennifer S.; Koyanagi, Robert Y.; Poland, Michael P.; Takahashi, T. Jane; Landowski, Claire M.

2014-01-01

In the century since the Hawaiian Volcano Observatory (HVO) put its first seismographs into operation at the edge of Kīlauea Volcano’s summit caldera, seismic monitoring at HVO (now administered by the U.S. Geological Survey [USGS]) has evolved considerably. The HVO seismic network extends across the entire Island of Hawai‘i and is complemented by stations installed and operated by monitoring partners in both the USGS and the National Oceanic and Atmospheric Administration. The seismic data stream that is available to HVO for its monitoring of volcanic and seismic activity in Hawai‘i, therefore, is built from hundreds of data channels from a diverse collection of instruments that can accurately record the ground motions of earthquakes ranging in magnitude from <1 to ≥8. In this chapter we describe the growth of HVO’s seismic monitoring systems throughout its first hundred years of operation. Although other references provide specific details of the changes in instrumentation and data handling over time, we recount here, in more general terms, the evolution of HVO’s seismic network. We focus not only on equipment but also on interpretative products and results that were enabled by the new instrumentation and by improvements in HVO’s seismic monitoring, analytical, and interpretative capabilities implemented during the past century. As HVO enters its next hundred years of seismological studies, it is well situated to further improve upon insights into seismic and volcanic processes by using contemporary seismological tools.

On-line Data Transmission, as Part of the Seismic Evaluation Process in the Buildings Field

NASA Astrophysics Data System (ADS)

Sorin Dragomir, Claudiu; Dobre, Daniela; Craifaleanu, Iolanda; Georgescu, Emil-Sever

2017-12-01

The thorough analytical modelling of seismic actions, of the structural system and of the foundation soil is essential for a proper dynamic analysis of a building. However, the validation of the used models should be made, whenever possible, with reference to results obtained from experimental investigations, building instrumentation and monitoring of vibrations generated by various seismic or non-seismic sources. In Romania, the permanent seismic instrumentation/monitoring of buildings is part of a special follow-up activity, performed in accordance with the P130/1999 code for the time monitoring of building behaviour and with the seismic design code, P100-2013. By using the state-of-the-art modern equipment (GeoSIG and Kinemetrics digital accelerographs) in the seismic network of the National Institute for Research and Development URBAN-INCERC, the instrumented buildings can be monitored remotely, with recorded data being sent to authorities or to research institutes in the field by a real-time data transmission system. The obtained records are processed, computing the Fourier amplitude spectra and the response spectra, and the modal parameters of buildings are determined. The paper presents some of the most important results of the institute in the field of building monitoring, focusing on the situation of some significant instrumented buildings located in different parts of the country. In addition, maps with data received from seismic stations after the occurrence of two recent Vrancea (Romania) earthquakes, showing the spatial distribution of ground accelerations, are presented, together with a comparative analysis, performed with reference to previous studies in the literature.

Designing a new post-hole seismological station on Antarctica inlandsis (Concordia station)

NASA Astrophysics Data System (ADS)

Bès de Berc, M.; Maggi, A.; Leveque, J. J.; Thore, J. Y.

2015-12-01

Concordia (75°S 123°E) is a scientific base operated by French and Italian polar institutes IPEV (Institut Paul-Emile Victor) and PNRA (Programma Nazionale di Ricerche in Antartide, and is located on the inlandsis of the East Antarctica plateau. It hosts a seismological station CCD which has provided observatory quality data since the year 2000, has been integrated into the Geoscope network since 2008 and whose data are now available in real-time from IRIS. The current seismic vault is located 800m from Concordia base, as far away as is deemed logistically possible by IPEV, at a depth of 12m. The vault is thermally very stable, but given the close distance to the base, suffers from increased diurnal noise (up to 40 dB) at frequencies above 1Hz, especially in the summer season. Anthropic noise is trapped in the firn (snow) layer, which forms an 100-110m thick waveguide, and is picked up very easily in the seismic vault. The vault is made from steel containers buried vertically in the snow. The hydrostatic pressure of the snow is deforming them: we see container cracking events on the seismograms, and also visual evidence of container deformation inside the vault. In the near future, this deformation will create a security problem.We have decided to progressively abandon our current vault, and construct a new post-hole seismological installation nearby. We plan to drill to 130m depth, which would place us below the firn layer waveguide and also below the ice pinch-out depth. To be able to run the station for several years and change or service the instrumentation if required, we need to keep the hole open, to avoid any hydrostatic movement, and to maintain good coupling between the sensor and the surrounding hard ice. To achieve these goals, we shall install a casing in the fin layer and then drill a few meters more without casing in hard ice. After installing the instrument, we shall then fill the whole hole with a drilling fluid whose density is similar to that

Mantle wedge structure beneath the Yamato Basin, southern part of the Japan Sea, revealed by long-term seafloor seismic observations

NASA Astrophysics Data System (ADS)

Shinohara, M.; Nakahigashi, K.; Yamashita, Y.; Yamada, T.; Mochizuki, K.; Shiobara, H.

2016-12-01

The Japanese Islands are located at subduction zones where Philippine Sea (PHS) plate subducts from the southeast beneath the Eurasian plate and the Pacific plate descends from the east beneath the PHS and Eurasian plates and have a high density of seismic stations. Many seismic tomography studies using land seismic station data were conducted to reveal the seismic structure. These studies discussed the relationship between heterogeneous structures and the release of fluids from the subducting slab, magma generation and movement in the subduction zone. However, regional tomography using the land station data did not have a sufficient resolution to image a deep structure beneath the Japan Sea.To obtain the deep structure, observations of natural earthquakes within the Japan Sea are essential. Therefore, we started the repeating long-term seismic observations using ocean bottom seismometers(OBSs) in the Yamato Basin from 2013 to 2016. We apply travel-time tomography method to the regional earthquake and teleseismic arrival-data recorded by OBSs and land stations. In this presentation, we will report the P and S wave tomographic images down to a depth of 300 km beneath the southern part of the Japan Sea. This study was supported by "Integrated Research Project on Seismic and Tsunami Hazards around the Sea of Japan" conducted by the Ministry of Education, Culture, Sports, Science, and Technology (MEXT) of Japan.

Seismic Structure of the Antarctic Upper Mantle and Transition Zone Unearthed by Full Waveform Adjoint Tomography

NASA Astrophysics Data System (ADS)

Lloyd, A. J.; Wiens, D.; Zhu, H.; Tromp, J.; Nyblade, A.; Anandakrishnan, S.; Aster, R. C.; Huerta, A. D.; Winberry, J. P.; Wilson, T. J.; Dalziel, I. W. D.; Hansen, S. E.; Shore, P.

2017-12-01

The upper mantle and transition zone beneath Antarctica and the surrounding ocean are among the poorest seismically imaged regions of the Earth's interior. Over the last 1.5 decades researchers have deployed several large temporary broadband seismic arrays focusing on major tectonic features in the Antarctic. The broader international community has also facilitated further instrumentation of the continent, often operating stations in additional regions. As of 2016, waveforms are available from almost 300 unique station locations. Using these stations along with 26 southern mid-latitude seismic stations we have imaged the seismic structure of the upper mantle and transition zone using full waveform adjoint techniques. The full waveform adjoint inversion assimilates phase observations from 3-component seismograms containing P, S, Rayleigh, and Love waves, including reflections and overtones, from 270 earthquakes (5.5 ≤ Mw ≤ 7.0) that occurred between 2001-2003 and 2007-2016. We present the major results of the full waveform adjoint inversion following 20 iterations, resulting in a continental-scale seismic model (ANT_20) with regional-scale resolution. Within East Antarctica, ANT_20 reveals internal seismic heterogeneity and differences in lithospheric thickness. For example, fast seismic velocities extending to 200-300 km depth are imaged beneath both Wilkes Land and the Gamburtsev Subglacial Mountains, whereas fast velocities only extend to 100-200 km depth beneath the Lambert Graben and Enderby Land. Furthermore, fast velocities are not found beneath portions of Dronning Maud Land, suggesting old cratonic lithosphere may be absent. Beneath West Antarctica slow upper mantle seismic velocities are imaged extending from the Balleny Island southward along the Transantarctic Mountains front, and broaden beneath the southern and northern portion of the mountain range. In addition, slow upper mantle velocities are imaged beneath the West Antarctic coast extending

The compilation of the instrumental seismic catalogue of Italy: 1975-1984

NASA Astrophysics Data System (ADS)

Giardini, D.; Velonà, M. A.; Boschi, E.

1992-12-01

We compile a homogeneous and complete catalogue of the seismicity of the Italian region for 1975-1984, the period marking the transition from standard analogue seismometry to the new digital era. The work is developed in three phases: (1) the creation of a uniform digital databank of all seismic station readings, unifying the database available at the Istituto Nazionale di Geofisica with the catalogue of the International Seismological Centre; (2) the preparation of numerical procedures for automatic association of arrival data and for hypocentre location, using arrivals from local, regional and teleseismic stations in a spherical geometry; (3) the introduction of lateral heterogeneity by calibrating regional travel-time curves and station corrections. The first two phases have been completed, providing a new instrumental catalogue obtained using a spherical Earth model; the third phase is presented here in a preliminary stage.

Spatial wavefield gradient-based seismic wavefield separation

NASA Astrophysics Data System (ADS)

Van Renterghem, C.; Schmelzbach, C.; Sollberger, D.; Robertsson, J. OA

2018-03-01

Measurements of the horizontal and vertical components of particle motion combined with estimates of the spatial gradients of the seismic wavefield enable seismic data to be acquired and processed using single dedicated multicomponent stations (e.g. rotational sensors) and/or small receiver groups instead of large receiver arrays. Here, we present seismic wavefield decomposition techniques that use spatial wavefield gradient data to separate land and ocean bottom data into their upgoing/downgoing and P/S constituents. Our method is based on the elastodynamic representation theorem with the derived filters requiring local measurements of the wavefield and its spatial gradients only. We demonstrate with synthetic data and a land seismic field data example that combining translational measurements with spatial wavefield gradient estimates allows separating seismic data recorded either at the Earth's free-surface or at the sea bottom into upgoing/downgoing and P/S wavefield constituents for typical incidence angle ranges of body waves. A key finding is that the filter application only requires knowledge of the elastic properties exactly at the recording locations and is valid for a wide elastic property range.

100 years of seismic research on the Moho

NASA Astrophysics Data System (ADS)

Prodehl, Claus; Kennett, Brian; Artemieva, Irina M.; Thybo, Hans

2013-12-01

The detection of a seismic boundary, the “Moho”, between the outermost shell of the Earth, the Earth's crust, and the Earth's mantle by A. Mohorovičić was the consequence of increased insight into the propagation of seismic waves caused by earthquakes. This short history of seismic research on the Moho is primarily based on the comprehensive overview of the worldwide history of seismological studies of the Earth's crust using controlled sources from 1850 to 2005, by Prodehl and Mooney (2012). Though the art of applying explosions, so-called “artificial events”, as energy sources for studies of the uppermost crustal layers began in the early 1900s, its effective use for studying the entire crust only began at the end of World War II. From 1945 onwards, controlled-source seismology has been the major approach to study details of the crust and underlying crust-mantle boundary, the Moho. The subsequent description of history of controlled-source crustal seismology and its seminal results is subdivided into separate chapters for each decade, highlighting the major advances achieved during that decade in terms of data acquisition, processing technology, and interpretation methods. Since the late 1980s, passive seismology using distant earthquakes has played an increasingly important role in studies of crustal structure. The receiver function technique exploiting conversions between P and SV waves at discontinuities in seismic wavespeed below a seismic station has been extensively applied to the increasing numbers of permanent and portable broad-band seismic stations across the globe. Receiver function studies supplement controlled source work with improved geographic coverage and now make a significant contribution to knowledge of the nature of the crust and the depth to Moho.