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Reply to the Comment "Intercluster correlation in Seismicity" by Helmstetter and Sornette

Description: This paper is a reply to the comment by Helmstetter and Sornette titled "Intercluster correlation in Seismicity" which addresses an important point in a paper written by the authors that needs to be clarified.
Date: September 15, 2003
Creator: Mega, Mirko S.; Allegrini, Paolo; Grigolini, Paolo; Latora, Vito; Palatella, Luigi; Rapisarda, Andrea et al.
Partner: UNT College of Arts and Sciences

Seismicity in Central North Africa at low magnitudes: A first look at the TAM event detected data base

Description: Teleseismic observations of seismicity in the central North Africa region show that the region is aseismic. This is true for earthquakes with a body wave magnitude greater than about 4 or so. For earthquakes with body wave magnitudes substantially below about 4, the teleseismic observations of seismicity in the central Sahara are incomplete since smaller earthquakes would probably not be detected and located by the current teleseismic monitoring networks. Only one known open seismic station has been operating in the central Sahara. This is the Tamanrasset (TAM) seismic station in southern Algeria. A simple analysis of data records from this station can be used to determine if the central Sahara is also relatively aseismic at magnitudes substantially below 4. That is the primary purpose of this study.
Date: January 1, 1997
Creator: Harben, P.E.,
Partner: UNT Libraries Government Documents Department

Recent applications of bandpass filtering

Description: Bandpass filtering has been applied recently in two widely different seismic applications: S.R. Taylor and A.A. Velasco in their source-path amplitude-correction (SPAC) algorithm and N.K. Yacoub in his maximum spectral energy algorithm for picking teleseismic P-wave arrival times. Though the displacement spectrum is the intermediate product in both cases, the filters and scaling corrections used to estimate it are entirely different. They tested both and found that the scaling used by Taylor and Velasco worked in all cases tested whereas Yacoub's did not. They also found that bandpass filtering as implemented by Taylor and Velasco does not work satisfactorily; however, the Gaussian filter used by Yacoub does work. The bandpass filter of Taylor and Velasco works satisfactorily when the results are centered in the band; however, a comb filter with the same number of poles and zeros as the bandpass used by Taylor and Velasco works better than the bandpass filter.
Date: March 15, 1999
Creator: Denny, M D
Partner: UNT Libraries Government Documents Department

Seismicity Precursors of the M6.0 2004 Parkfield and M7.0 1989Loma Prieta Earthquakes

Description: The M6.0 2004 Parkfield and M7.0 1989 Loma Prietastrike-slip earthquakes on the San Andreas Fault (SAF) were preceded byseismicity peaks occurring several months prior to the main events.Earthquakes directly within the SAF zone were intentionally excluded fromthe analysis because they manifest stress-release processes rather thanstress accumulation. The observed increase in seismicity is interpretedas a signature of the increasing stress level in the surrounding crust,whereas the peaks and the subsequent decrease in seismicity areattributed to damage-induced softening processes. Furthermore, in bothcases there is a distinctive zone of low seismic activity that surroundsthe epicentral region in the pre-event period. The increase of seismicityin the crust surrounding a potential future event and the development ofa low-seismicity epicentral zone can be regarded as promising precursoryinformation that could help signal the arrival of large earthquakes. TheGutenberg-Richter relationship (GRR) should allow extrapolation ofseismicity changes down to seismic noise level magnitudes. Thishypothesis is verified by comparison of seismic noise at 80 Hz with theParkfield M4 1993-1994 series, where noise peaks 5 months before theseries to about twice the background level.
Date: March 9, 2006
Creator: Korneev, Valeri A.
Partner: UNT Libraries Government Documents Department

Analysis of cause and mechanism for injection-induced seismicityat the Geysers Geothermal Field, California

Description: We analyzed relative contributions to the cause andmechanism of injection-induced seismicity at The Geysers geothermalfield, California, using coupled thermal-hydrological-mechanicalmodeling. Our analysis shows that the most important cause forinjection-induced seismicity is injection-induced cooling and associatedthermal-elastic shrinkage that changes the stress state in such a waythat mechanical failure and seismicity can be induced. Specifically, thecooling shrinkage results in unloading and associated loss of shearstrength in critically shear-stressed fractures, which are thenreactivated. Thus, our analysis shows that cooling-induced shear slipalong fractures is the dominant mechanism of injection-induced seismicityat The Geysers.
Date: June 14, 2007
Creator: Rutqvist, Jonny & Oldenburg, Curtis
Partner: UNT Libraries Government Documents Department

Integrated modeling and field study of potential mechanisms forinduced seismicity at The Geysers Goethermal Field, California

Description: In this paper, we present progress made in a study aimed atincreasing the understanding of the relative contributions of differentmechanisms that may be causing the seismicity occurring at The Geysersgeothermal field, California. The approach we take is to integrate: (1)coupled reservoir geomechanical numerical modeling, (2) data fromrecently upgraded and expanded NCPA/Calpine/LBNL seismic arrays, and (3)tens of years of archival InSAR data from monthly satellite passes. Wehave conducted a coupled reservoir geomechanical analysis to studypotential mechanisms induced by steam production. Our simulation resultscorroborate co-locations of hypocenter field observations of inducedseismicity and their correlation with steam production as reported in theliterature. Seismic and InSAR data are being collected and processed foruse in constraining the coupled reservoir geomechanicalmodel.
Date: June 7, 2006
Creator: Rutqvist, Jonny; Majer, Ernie; Oldenburg, Curt; Peterson, John & Vasco, Don
Partner: UNT Libraries Government Documents Department

Analysis of source spectra, attenuation, and site effects from central and eastern United States earthquakes

Description: This report describes the results from three studies of source spectra, attenuation, and site effects of central and eastern United States earthquakes. In the first study source parameter estimates taken from 27 previous studies were combined to test the assumption that the earthquake stress drop is roughly a constant, independent of earthquake size. 200 estimates of stress drop and seismic moment from eastern North American earthquakes were combined. It was found that the estimated stress drop from the 27 studies increases approximately as the square-root of the seismic moment, from about 3 bars at 10{sup 20} dyne-cm to 690 bars at 10{sup 25} dyne-cm. These results do not support the assumption of a constant stress drop when estimating ground motion parameters from eastern North American earthquakes. In the second study, broadband seismograms recorded by the United States National Seismograph Network and cooperating stations have been analysed to determine Q{sub Lg} as a function of frequency in five regions: the northeastern US, southeastern US, central US, northern Basin and Range, and California and western Nevada. In the third study, using spectral analysis, estimates have been made for the anelastic attenuation of four regional phases, and estimates have been made for the source parameters of 27 earthquakes, including the M{sub b} 5.6, 14 April, 1995, West Texas earthquake.
Date: February 1, 1998
Creator: Lindley, G.
Partner: UNT Libraries Government Documents Department

Compilation of Earthquakes from 1850-2007 within 200 miles of the Idaho National Laboratory

Description: An updated earthquake compilation was created for the years 1850 through 2007 within 200 miles of the Idaho National Laboratory. To generate this compilation, earthquake catalogs were collected from several contributing sources and searched for redundant events using the search criteria established for this effort. For all sets of duplicate events, a preferred event was selected, largely based on epicenter-network proximity. All unique magnitude information for each event was added to the preferred event records and these records were used to create the compilation referred to as “INL1850-2007”.
Date: July 1, 2010
Creator: Carpenter, N. Seth
Partner: UNT Libraries Government Documents Department

The Impact of Injection on Seismicity at The Geyses, CaliforniaGeothermal Field

Description: Water injection into geothermal systems has often become arequired strategy to extended and sustain production of geothermalresources. To reduce a trend of declining pressures and increasingnon-condensable gas concentrations in steam produced from The Geysers,operators have been injecting steam condensate, local rain and streamwaters, and most recently treated wastewater piped to the field fromneighboring communities. If geothermal energy is to provide a significantincrease in energy in the United States (US Department of Energy (DOE)goal is 40,000 megawatts by 2040), injection must play a larger role inthe overall strategy, i.e., enhanced geothermal systems, (EGS). Presentedin this paper are the results of monitoring microseismicity during anincrease in injection at The Geysers field in California using data froma high-density digital microearthquake array. Although seismicity hasincreased due to increased injection it has been found to be somewhatpredicable, thus implying that intelligent injection control may be ableto control large increases in seismicity.
Date: September 25, 2006
Creator: Majer, Ernest L. & Peterson, John E.
Partner: UNT Libraries Government Documents Department

Induced seismicity associated with enhanced geothermal system

Description: Enhanced Geothermal Systems (EGS) offer the potential to significantly add to the world energy inventory. As with any development of new technology, some aspects of the technology has been accepted by the general public, but some have not yet been accepted and await further clarification before such acceptance is possible. One of the issues associated with EGS is the role of microseismicity during the creation of the underground reservoir and the subsequent extraction of the energy. The primary objectives of this white paper are to present an up-to-date review of the state of knowledge about induced seismicity during the creation and operation of enhanced geothermal systems, and to point out the gaps in knowledge that if addressed will allow an improved understanding of the mechanisms generating the events as well as serve as a basis to develop successful protocols for monitoring and addressing community issues associated with such induced seismicity. The information was collected though literature searches as well as convening three workshops to gather information from a wide audience. Although microseismicity has been associated with the development of production and injection operations in a variety of geothermal regions, there have been no or few adverse physical effects on the operations or on surrounding communities. Still, there is public concern over the possible amount and magnitude of the seismicity associated with current and future EGS operations. It is pointed out that microseismicity has been successfully dealt with in a variety of non-geothermal as well as geothermal environments. Several case histories are also presented to illustrate a variety of technical and public acceptance issues. It is concluded that EGS Induced seismicity need not pose any threat to the development of geothermal resources if community issues are properly handled. In fact, induced seismicity provides benefits because it can be used as a ...
Date: September 26, 2006
Creator: Majer, Ernest; Majer, Ernest L.; Baria, Roy; Stark, Mitch; Oates, Stephen; Bommer, Julian et al.
Partner: UNT Libraries Government Documents Department

Caucasus Seismic Information Network: Data and Analysis Final Report

Description: The geology and tectonics of the Caucasus region (Armenia, Azerbaijan, and Georgia) are highly variable. Consequently, generating a structural model and characterizing seismic wave propagation in the region require data from local seismic networks. As of eight years ago, there was only one broadband digital station operating in the region – an IRIS station at Garni, Armenia – and few analog stations. The Caucasus Seismic Information Network (CauSIN) project is part of a nulti-national effort to build a knowledge base of seismicity and tectonics in the region. During this project, three major tasks were completed: 1) collection of seismic data, both in event catalogus and phase arrival time picks; 2) development of a 3-D P-wave velocity model of the region obtained through crustal tomography; 3) advances in geological and tectonic models of the region. The first two tasks are interrelated. A large suite of historical and recent seismic data were collected for the Caucasus. These data were mainly analog prior to 2000, and more recently, in Georgia and Azerbaijan, the data are digital. Based on the most reliable data from regional networks, a crustal model was developed using 3-D tomographic inversion. The results of the inversion are presented, and the supporting seismic data are reported. The third task was carried out on several fronts. Geologically, the goal of obtaining an integrated geological map of the Caucasus on a scale of 1:500,000 was initiated. The map for Georgia has been completed. This map serves as a guide for the final incorporation of the data from Armenia and Azerbaijan. Description of the geological units across borders has been worked out and formation boundaries across borders have been agreed upon. Currently, Armenia and Azerbaijan are working with scientists in Georgia to complete this task. The successful integration of the geologic data also required ...
Date: February 22, 2007
Creator: Martin, Randolph; Krasovec, Mary; Romer, Spring; O'Connor, Timothy; Bombolakis, Emanuel G.; Sun, Youshun et al.
Partner: UNT Libraries Government Documents Department

INL Seismic Monitoring Annual Report: January 1, 2010 – December 31, 2010

Description: During 2010, the INL Seismic Monitoring Program evaluated 11,606 earthquakes from around the world, the western United States, and local region of the eastern Snake River Plain (ESRP). INL located 2,085 earthquakes and man-made blasts within the local region outside and within a 161-km (or 100-mile) radius of INL. Of these events, 53 were small-to-moderate size earthquakes ranging in magnitude from 3.0 to 4.8. 672 earthquakes occurred within the 161-km radius of INL and the majority of these earthquakes were located in active regions of the Basin and Range Province that surrounds the ESRP. There were 10 microearthquakes within the boundary of the ESRP, all of magnitude less than or equal to 2.0. Five of those were located within and near the ESRP at Craters of the Moon National Monument (COM) at mid- and lower-crust depths and are interpreted to be related to fluid movement. Since 1972, INL has recorded 48 small-magnitude, microearthquakes (M = 2.2) within the ESRP (not including COM events) and 22 deep microearthquakes (M = 2.3) in the vicinity of Craters of the Moon National Monument.
Date: September 1, 2011
Creator: Carpenter, N. Seth; Payne, Suzette J.; Hodges, Jed M. & Berg, Robert G.
Partner: UNT Libraries Government Documents Department

Seismicity in the Vicinity of Yucca Mountain, Nevada, for the Period October 1, 2002, to September 30, 2003

Description: Earthquake activity in the Yucca Mountain from October 1, 2002 through September 30, 2003 (FY03) is assessed and compared with previous activity in the region. FY03 is the first reporting year since the 1992 M 5.6 Little Skull Mountain earthquake with no earthquakes greater than M 3.0 within 65 km of Yucca Mountain. In addition, FY03 includes the fewest number of earthquakes greater than M 2.0 in any reporting year since the LSM event. With 3075 earthquakes in the catalog, FY03 represents the second largest number of earthquakes (second to FY02) since FY96 when digital seismic network operations began. The largest event during FY03 was M 2.78 in eastern NTS and there were only 8 earthquakes greater than M 2.0.
Date: December 4, 2007
Creator: Smith, Ken & von Seggern, David
Partner: UNT Libraries Government Documents Department

First Quarter Hanford Seismic Report for Fiscal Year 2008

Description: The Hanford Seismic Assessment Program (HSAP) provides an uninterrupted collection of high-quality raw and processed seismic data from the Hanford Seismic Network for the U.S. Department of Energy and its contractors. The Hanford Seismic Assessment Team locates and identifies sources of seismic activity and monitors changes in the historical pattern of seismic activity at the Hanford Site. The data are compiled, archived, and published for use by the Hanford Site for waste management, natural phenomena hazards assessments, and engineering design and construction. In addition, the seismic monitoring organization works with the Hanford Site Emergency Services Organization to provide assistance in the event of a significant earthquake on the Hanford Site. The Hanford Seismic Network and the Eastern Washington Regional Network consist of 41 individual sensor sites and 15 radio relay sites maintained by the Hanford Seismic Assessment Team. For the Hanford Seismic Network, forty-four local earthquakes were recorded during the first quarter of fiscal year 2008. A total of thirty-one micro earthquakes were recorded within the Rattlesnake Mountain swarm area at depths in the 5-8 km range, most likely within the pre-basalt sediments. The largest event recorded by the network during the first quarter (November 25, 2007 - magnitude 1.5 Mc) was located within this swarm area at a depth of 4.3 km. With regard to the depth distribution, three earthquakes occurred at shallow depths (less than 4 km, most likely in the Columbia River basalts), thirty-six earthquakes at intermediate depths (between 4 and 9 km, most likely in the pre-basalt sediments), and five earthquakes were located at depths greater than 9 km, within the crystalline basement. Geographically, thirty-eight earthquakes occurred in swarm areas and six earth¬quakes were classified as random events.
Date: March 21, 2008
Creator: Rohay, Alan C.; Sweeney, Mark D.; Hartshorn, Donald C.; Clayton, Ray E. & Devary, Joseph L.
Partner: UNT Libraries Government Documents Department

Fault Geomechanics and Carbon Dioxide Leakage Applied to Geological Storage: FY07 Quarterly and Summary Reports

Description: Safe and permanent storage of carbon dioxide in geologic reservoirs is critical to geologic sequestration. The objective of this study is to quantify the conditions under which a general (simulated) fault network and a specific (field case) fault network will fail and leak carbon dioxide out of a reservoir. Faults present a potential fast-path for CO{sub 2} leakage from reservoirs to the surface. They also represent potential induced seismicity hazards. It is important to have improved quantitative understandings of the processes that trigger activity on faults and the risks they present. Fortunately, the conditions under which leakage along faults is induced can be predicted and quantified given the fault geometry, reservoir pressure, an in-situ stress tensor. We proposed to expand the current capabilities of fault threshold characterization and apply that capability to a site where is CO{sub 2} injection is active or planned. Specifically, we proposed to use a combination of discrete/explicit and continuum/implicit codes to provide constrain the conditions of fault failure. After minor enhancements of LLNL's existing codes (e.g., LDEC), we would create a 3D synthetic model of a common configuration (e.g., a faulted dome). During these steps, we will identify a field site where the necessary information is available and where the operators are willing to share the necessary information. We would then execute an analysis specific to the field case. The primary products by quarter are: 1Q--Identification of likely field case; 2Q--Functioning prototype fault model; 3Q--Execution of fault-slip/migration calculation for synthetic case; and 4Q--Begin simulation of fault-slip/migration calculation for field system. It is worth noting that due to the continuing resolution, we did not receive any funds until 3Q, and did not receive >65% of the support until 4Q. That said, we were still able to meet all of our milestones for FY07 on time and ...
Date: November 2, 2007
Creator: Friedmann, S. J. & Morris, J.
Partner: UNT Libraries Government Documents Department

Shear-slip analysis in multiphase fluid-flow reservoir engineeringap plications using TOUGH-FLAC

Description: This paper describes and demonstrates the use of the coupledTOUGH-FLAC simulator for geomechanical shear-slip (failure) analysis inmultiphase fluid-flow reservoir-engineering applications. Two approachesfor analyzing shear-slip are described, one using continuum stress-strainanalysis and another using discrete fault analysis. The use of shear-slipanalysis in TOUGH-FLAC is demonstrated on application examples related toCO2 sequestration and geothermal energy extraction. In the case of CO2sequestration, the shear-slip analysis is used to evaluate maximumsustainable CO2-injection pressure under increasing reservoir pressure,whereas in the case of geothermal energy extraction, the shear-slipanalysis is used to study induced seismicity during steam productionunder decreasing reservoir pressure and temperature.
Date: January 15, 2006
Creator: Rutqvist, Jonny; Birkholzer, Jens; Cappa, Frederic; Oldenburg,Curt & Tsang, Chin-Fu
Partner: UNT Libraries Government Documents Department


Description: Abstract We conduct a detailed test of a recently developed technique, CAPloc, in recovering source parameters from a few stations against results from a large broadband network in Southern California. The method uses a library of 1D Green’s functions which are broken into segments and matched to waveform observations with adjustable timing shifts. These shifts can be established by calibration against a distribution of well-located earthquakes and assembled in tomographic images for predicting various phase-delays. Synthetics generated from 2D cross-sections through these models indicates that 1D synthetic waveforms are sufficient in modeling but simply shifted in time for most hard-rock sites. This simplification allows the source inversion for both mechanism and location to easily obtain by grid search. We test one-station mechanisms for 160 events against the array for both PAS and GSC which have data since 1960. While individual solutions work well (about 90%), joint solutions produce more reliable and defensible results. Inverting for both mechanism and location also works well except for certain complex paths across deep basins and along mountain ridges.
Date: January 27, 2009
Creator: Helmberger, Donald V.; Tromp, Jeroen & Rodgers, Arthur J.
Partner: UNT Libraries Government Documents Department

Mapping Diffuse Seismicity Using Empirical Matched Field Processing Techniques

Description: The objective of this project is to detect and locate more microearthquakes using the empirical matched field processing (MFP) method than can be detected using only conventional earthquake detection techniques. We propose that empirical MFP can complement existing catalogs and techniques. We test our method on continuous seismic data collected at the Salton Sea Geothermal Field during November 2009 and January 2010. In the Southern California Earthquake Data Center (SCEDC) earthquake catalog, 619 events were identified in our study area during this time frame and our MFP technique identified 1094 events. Therefore, we believe that the empirical MFP method combined with conventional methods significantly improves the network detection ability in an efficient matter.
Date: January 21, 2011
Creator: Wang, J; Templeton, D C & Harris, D B
Partner: UNT Libraries Government Documents Department

The March 11, 2002 Masafi, United Arab Emirates Earthquake: Insights into the Seismotectonics of the Northern Oman Mountains

Description: A moderate (M{approx}5) earthquake struck the northeastern United Arab Emirates (UAE) and northern Oman on March 11, 2002. The event was felt over a wide area of the northern Emirates and was accompanied by smaller (felt) events before and after the March 11 main shock. The event was large enough to be detected and located by global networks at teleseismic distances. We estimated focal mechanism and depth from broadband complete regional waveform modeling. We report a normal mechanism with a slight right-lateral strike-slip component consistent with the large-scale tectonics. The normal component suggests relaxation of obducted crust of the Semail Ophilite (specifically, the Khor Fakkan Block) while the right-lateral strike-slip component of the mechanism is consistent with shear across the Oman Line. Felt earthquakes are rare in the region, however no regional seismic network exists in the UAE to determine local seismicity. This event offers a unique opportunity to study the active tectonics of the region as well as inform future studies of seismic hazard in the UAE and northern Oman.
Date: April 26, 2005
Creator: Rodgers, A; Fowler, A; Al-Amri, A & Al-Enezi, A
Partner: UNT Libraries Government Documents Department

Data Archived for Events in the Caucasus for the CauSINCollaboration Project

Description: The Causin project is a joint effort between the countries in the Caucasus region to develop a Probabilistic Seismic Hazard Analysis. To that end, we have compiled a database of all available network data in the region. The information contained in the database is from four countries: Armenia, Georgia, Azerbaijan, and Turkey and from the Incorporated Research Institutions for Seismology (IRIS). Table 1 lists the networks from which data were obtained. Figure 1 shows the locations of stations, and Figure 2 shows ray paths for event locations of the archived data. An ongoing effort in the region is the Caucasus Seismic Information Network (CauSIN) is an international scientific project enabling the countries and scientists of the region to: better understand the seismicity of the greater Caucasus; develop new monitoring networks to support the scientific understanding; provide access to seismic data from local networks in the participating countries; and develop a probabilistic seismic hazards assessment for the region enabling the governments in the region to better mitigate the damaging effects from large earthquakes. In parallel with this effort, training has been conducted on modern techniques for probabilistic hazards assessment. CauSIN is also an ongoing effort to promote cooperation in the geosciences between Georgia, Armenia, Azerbaijan, European Union and the United States. The DOE supports the American team from New England Research, Inc. (NER), Massachusetts Institute of Technology (MIT), Boston College, and Lawrence Livermore National Laboratory (LLNL).
Date: August 17, 2007
Creator: Godoladze, T; Hunt, D; Aliyev, F; Arakelyan, A; Kalafat, D; Javakhishvil, Z et al.
Partner: UNT Libraries Government Documents Department