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In this study, we analyzed the performance of a preliminary three-dimensional (3D) velocity model of the Eastern Caucasus covering most of the Azerbaijan. The model was developed in support to long-period ground motion simulations and seismic hazard assessment from regional earthquakes in Azerbaijan. The model’s performance was investigated by simulating ground motion from the damaging Mw 5.9, 2012 Zaqatala earthquake, which was well recorded throughout the region by broadband seismic instruments. In our simulations, we use a parallelized finite-difference method of fourth-order accuracy. The comparison between the simulated and recorded ground motion velocity in the modeled period range of 3–20 s shows that in general, the 3D velocity model performs well. Areas in which the model needs improvements are located mainly in the central part of the Kura basin and in the Caspian Sea coastal areas. Comparisons of simulated ground motion using our 3D velocity model and corresponding 1D regional velocity model were used to locate areas with strong 3D wave propagation effects. In areas with complex underground structure, the 1D model fails to produce the observed ground motion amplitude and duration, and spatial extend of ground motion amplification caused by wave propagation effects.

© 2016 The Authors. We analyze interferometric synthetic aperture radar (InSAR) data acquired between 2004 and 2014, by the ERS-2, Envisat, ALOS and TerraSAR-X/TanDEM-X satellite missions to measure and characterize time-dependent deformation at the Brady Hot Springs geothermal field in western Nevada due to extraction of fluids. The long axis of the ~4 km by ~1.5 km elliptical subsiding area coincides with the strike of the dominant normal fault system at Brady. Within this bowl of subsidence, the interference pattern shows several smaller features with length scales of the order of ~1 km. This signature occurs consistently in all of the well-correlated interferometric pairs spanning several months. Results from inverse modeling suggest that the deformation is a result of volumetric contraction in shallow units, no deeper than 600 m, likely associated with damaged regions where fault segments mechanically interact. Such damaged zones are expected to extend downward along steeply dipping fault planes, providing a high permeability conduit to the production wells. Using time series analysis, we test the hypothesis that geothermal production drives the observed deformation. We find a good correlation between the observed deformation rate and the rate of production in the shallow wells. We also explore mechanisms that could potentially cause the observed deformation, including thermal contraction of rock, decline in pore pressure and dissolution of minerals over time.

We investigate the excitation and propagation of far‐field seismic waves from the 905 kg trinitrotoluene equivalent underground chemical explosion SPE‐3 recorded during the Source Physics Experiment (SPE) at the Nevada National Security Site. The recorded far‐field ground motion at short and long distances is characterized by substantial shear‐wave energy, and large azimuthal variations in P ‐ and S ‐wave amplitudes. The shear waves observed on the transverse component of sensors at epicentral distances

We have developed a spatial, value of information (VOI) methodology that is designed specifically to include the inaccuracies of multidimensional geophysical inversions. VOI assesses the worth of information in terms of how it can improve the decision maker’s likelihood of a higher valued outcome. VOI can be applied to spatial data using an exploration example for hidden geothermal resources. This methodology is applicable for spatial decisions for other exploration decisions (e.g., oil, mining, etc.). This example evaluates how well the magnetotelluric (MT) technique is able to delineate the lateral position of electrically conductive materials that are indicative of a hidden geothermal resource. The conductive structure (referred to as the clay cap) represented where the geothermal alteration occurred. The prior uncertainty of the position of the clay cap (drilling target) is represented with multiple earth models. These prior models are used to numerically simulate the data collection, noise, inversion, and interpretation of the MT technique. MT’s ability to delineate the correct lateral location can be quantified by comparing the true location in each prior model to the location that is interpreted from each respective inverted model. Additional complexity in the earth models is included by adding more electrical conductors (not associated with the clay cap) and deeper targets. Both degrade the ability of the MT technique (the signal and inversion) to locate the clay cap thereby decreasing the VOI. The results indicate the ability of the prior uncertainty to increase and decrease the final VOI assessment. The results also demonstrate how VOI depends on whether or not a resource still exists below the clay cap because the clay cap is only a potential indicator of economic temperatures.

The Arabian Gulf is adjacent to the Zagros Mountains, one of the most seismically active regions in the world. We observe that broadband seismic records of Zagros earthquakes recorded on the Arabian side of the Gulf display long-duration surface waves. While shorter periods ( 10 km) of the Gulf basin, the long-period energy is enhanced and transmitted efficiently. Consequently, large earthquakes in the Zagros could result in amplified ground motions at long periods (2–10 s) relative to average behavior. Such ground motions are of concern for large engineered structures, such as tall buildings and long bridges with resonant periods in the same period range. Here we present results of investigations of the characteristics of ground motions recorded on the western shore of the Gulf from selected earthquakes in the Zagros Mountains region. Exceptionally, long-duration seismic waves, as compared with standard models, are shown to occur with periods of 2–10 s. This may be due to waveguide effects in the deep sedimentary basin structure of the Arabian Platform. In addition to analyzing recorded ground motion we performed 3D wave propagation simulations using a finite difference method and experimental velocity models of the Gulf, with different shallow sedimentary layers structures. The simulation results confirm our hypothesis that long-period waves with extremely long duration and relatively large amplitudes are caused by the geometry of the basin sedimentary layers and, to some extent, by shallow earthquake depths. Combined effects of basin edge geometry with sharp velocity contrasts and shallow sources (

Geodynamic processes occurring in the upper mantle such as slab break off and lithosphere delamination often result in high rates of lithospheric deformation and rapid tectonic uplift of large areas. The continent-continent collision zone between Arabia and Eurasia has been widely studied in this context, but several different viable geodynamic models exist to explain the uplift and deformation of the Anatolian Plateau and the Caucasus Mountains. We have imaged the uppermost mantle shear wave velocity structure of the East Anatolian-Caucasus region using surface wave tomography to better understand the regional tectonic activity since the onset of the collision between the Arabian and Eurasian Plates. Furthermore, we used our tomographic models to better understand the processes, which are responsible for the formation of the 2 km high plateau and the widespread volcanism in eastern Turkey, as well as reactivation of deformation and deep seismicity in the eastern Greater Caucasus. Our model of regional upper mantle shear wave velocity structure supports subduction of the northern and southern branches of Neo-Tethys lithosphere between Eurasia and Gondwana and suggests a possible underthrusting of the Kura Basin lithosphere beneath the Greater Caucasus.

[1] We present a catalog of interferometric synthetic aperture radar (InSAR) constraints on deformation that occurred during earthquake sequences in southern Iran between 1992 and 2011, and explore the implications on the accommodation of large-scale continental convergence between Saudi Arabia and Eurasia within the Zagros Mountains. The Zagros Mountains, a salt-laden fold-and-thrust belt involving ~10 km of sedimentary rocks overlying Precambrian basement rocks, have formed as a result of ongoing continental collision since 10–20 Ma that is currently occurring at a rate of ~3 cm/yr. We first demonstrate that there is a biased misfit in earthquake locations in global catalogs that likely results from neglect of 3-D velocity structure. Previous work involving two M ~ 6 earthquakes with well-recorded aftershocks has shown that the deformation observed with InSAR may represent triggered slip on faults much shallower than the primary earthquake, which likely occurred within the basement rocks (>10 km depth). We explore the hypothesis that most of the deformation observed with InSAR spanning earthquake sequences is also due to shallow, triggered slip above a deeper earthquake, effectively doubling the moment release for each event. We quantify the effects that this extra moment release would have on the discrepancy between seismically and geodetically constrained moment rates in the region, finding that even with the extra triggered fault slip, significant aseismic deformation during the interseismic period is necessary to fully explain the convergence between Eurasia and Saudi Arabia.

Ambient noise correlation was applied to 18 months of continuous seismic data from 14 stations. The procedure of Bensen et al [2007] was followed with some changes to optimize signal-to-noise of the results. The 18 months of correlations (representing about 1 week of CPU time on a 12 core machine) were stacked and manually inspected to yield about 40 cross-correlations. These cross-correlations represent the Green’s function between the station pairs and will be analyzed in part two of this project to yield velocity structure.

An intermediate-depth earthquake is confirmed at a depth of 158 4 km under the northern foothills of the Greater Caucasus. Separate methods were used to confirm the depth: data from local and regional networks, teleseismic depth phases, and examination of waveforms. Additional examination of global catalogs suggests the presence of a (perhaps remnant) northeast-dipping subduction zone under the Greater Caucasus. The most likely explanation appears to be subduction of oceanic crust with the interface at the northern edge of the Kura Basin. Events at depths of 30 – 50 km in the Kura Basin may be related to underthrusting by the South Caspian basin rather than subduction in the Greater Caucasus.

Cerro Prieto is the oldest and largest Mexican geothermal field in operation and has been producing electricity since 1973. The large amount of geothermal fluids extracted to supply steam to the power plants has resulted in considerable deformation in and around the field. The deformation includes land subsidence and related ground fissuring and faulting. These phenomena have produced severe damages to the local infrastructure such as roads, irrigation canals and other facilities. In this paper, the technique of Differential Synthetic Aperture Radar Interferometry (DInSAR) is applied using C-band ENVISAR ASAR data acquired between 2003 and 2006 to determine the extent and amount of land subsidence in the Mexicali Valley near Cerro Prieto Geothermal Field. The DInSAR results were compared with published data from precise leveling surveys (1994–1997 and 1997–2006) and detailed geological information in order to improve understanding of the temporal and spatial distributions of anthropogenic subsidence in the Mexicali Valley. The leveling and DInSAR data were modeled to characterize the observed deformation in terms of fluid extraction. The results confirm that the tectonic faults control the spatial extent of the observed subsidence. These faults likely act as groundwater flow barriers for aquifers and reservoirs. The shape of the subsiding area coincides with the Cerro Prieto pull-apart basin. In addition, the changes in spatial pattern and rate of the subsidence are correlated with the development of the Cerro Prieto Geothermal Field.

On 24 May 2006, a moderate-size ( M w 5.4) earthquake occurred in the Mexicali Valley, Mexico. The event created 5 km of surface rupture. Associated deformation was recorded by geotechnical instruments, leveling profile, and synthetic aperture radar interferometry. A coseismic steplike groundwater level change was detected at seven wells. The surface rupture consisted of up to 30 cm of primarily normal displacement. 20–25 cm of vertical offset was recorded by a crackmeter and 20 cm on leveling line. We created Envisat C-band interferograms spanning the 24 May 2006 earthquake to image the coseismic displacement. Although the coherence of the interferometric images is low, the images clearly show a spatial displacement field centered on the known surface rupture that is consistent with the expected sense of motion. The interferograms and leveling line also include subsidence related to geothermal production. This anthropogenic subsidence component was estimated using a pre-event interferogram. Source parameters for the earthquake were estimated using forward modeling of both surface deformation data and static volume strain change (inferred from coseismic changes in groundwater level). Modeling was based on finite rectangular fault embedded in an elastic media. The preferred fault model has a strike, rake, and dip of (48°, -89°, 45°) and has a length of 5.2 km, width of 6.7 km, and 34 cm of uniform slip. The geodetic moment, based on the modeled fault parameters, is ![Graphic][1] . The model matched the observed surface deformation, expected groundwater changes, and teleseismic moment reasonably well. [1]: /embed/inline-graphic-1.gif

Deep fluid extraction in the Cerro Prieto geothermal field (CPGF) has caused subsidence and induced slip on tectonic faults in the Mexicali Valley (Baja California, Mexico). The Mexicali Valley is located in the southern part of the Salton Trough, at the boundary between the Pacific and North American plates. The Valley is characterized by being a zone of continuous tectonic deformation, geothermal activity, and seismicity. Within the Cerro Prieto pull-apart basin, seismicity is concentrated mainly in swarms, while strong earthquakes have occurred in the Imperial and Cerro Prieto transform faults, that are the eastern and western bound of the basin. Since 1973, fluid extraction at the CPGF has influenced deformation in the area, accelerating the subsidence and causing rupture (frequently as vertical slip or creep) on the surface traces of tectonic faults. Both subsidence and fault slip are causing damage to infrastructure like roads, railroad tracks, irrigation channels, and agricultural fields. Currently, accelerated extraction in the eastern part of CPGF has shifted eastwards the area of most pronounced subsidence rate; this accelerated subsidence can be observed at the Saltillo fault, a southern branch of the Imperial fault in the Mexicali Valley. Published leveling data, together with field data from geological surveys, geotechnical instruments, and new InSAR images were used to model the observed deformation in the area in terms of fluid extraction. Since the electricity production in the CPGF is an indispensable part of Baja California economy, extraction is sure to continue and may probably increase, so that the problem of damages caused by subsidence will likely increase in the future.

Seismic reflection the primary tool used in petroleum exploration and production, but use in geothermal exploration is less standard, in part due to cost but also due to the challenges in identifying the highly-permeable zones essential for economic hydrothermal systems [e.g. Louie et al., 2011; Majer, 2003]. Newer technology, such as wireless sensors and low-cost high performance computing, has helped reduce the cost and effort needed to conduct 3D surveys. The second difficulty, identifying permeable zones, has been less tractable so far. Here we report on the use of seismic attributes from a 3D seismic survey to identify and map permeable zones in a hydrothermal area.

Source parameters determined from interferometric synthetic aperture radar (Insar) measurements and from seismic data are compared from four moderate-size (less than M 6) earthquakes in southern California. The goal is to verify approximate detection capabilities of Insar, assess differences in the results, and test how the two results can be reconciled. First, we calculated the expected surface deformation from all earthquakes greater than magnitude 4 in areas with available Insar data (347 events). A search for deformation from the events in the interferograms yielded four possible events with magnitudes less than 6. The search for deformation was based on a visual inspection as well as cross-correlation in two dimensions between the measured signal and the expected signal. A grid-search algorithm was then used to estimate focal mechanism and depth from the Insar data. The results were compared with locations and focal mechanisms from published catalogs. An independent relocation using seismic data was also performed. The seismic locations fell within the area of the expected rupture zone for the three events that show clear surface deformation. Therefore, the technique shows the capability to resolve locations with high accuracy and is applicable worldwide. The depths determined by Insar agree with well-constrained seismic locations determined in a 3D velocity model. Depth control for well-imaged shallow events using Insar data is good, and better than the seismic constraints in some cases. A major difficulty for Insar analysis is the poor temporal coverage of Insar data, which may make it impossible to distinguish deformation due to different earthquakes at the same location.

Modern seismology has rapidly passed the level of many educational displays. While seismologists almost exclusively use digital data, the traditional pen and ink drum recorder remains the mainstay of many educational seismology exhibits in museums. Although a drum recorder retains several major advantages, such as familiarity and visual appeal, it also has several clear disadvantages, both technical and educational. Chief among the technical disadvantages are the poor data quality of many museum displays due to high noise levels and the difficulty and cost of replacing paper, pens, and ink on a routine basis. The use of a drum recorder also gives a misleading and antiquated impression of how modern seismologists work. Another feature of museum displays is that the sensor is usually kept well away from the actual display to reduce seismic noise levels. However, having a sensor near the display is useful for adding interaction to the display. Visitors can create their own seismic signals by jumping, a feature which is especially popular with children. In general, interactivity in museum displays has been shown to increase the attractiveness of the display. Interactivity is believed to promote learning, at least for some learning styles, although it is not always clear exactly what is being learned (Feher, 1990; Falk and Dierking, 1992). In this paper we describe an innovative exhibit that provides interactivity, displays high-quality seismic data, and transmits the data in real-time to a local seismic network. A strong-motion sensor is located under the display, allowing people to jump, stamp feet, and otherwise create seismic waves that appear almost immediately on a computer monitor. During periods of little museum activity, which is at least 14 hours per day, the sensor records useful low-noise data that can be merged with regional seismic network data for scientific analysis. In addition …

We looked for evidence of interseismic strain occurring between the 1992 Landers earthquake and the 1999 Hector Mine earthquake near the Lavic Lake and Bullion faults by using interferometric synthetic aperture radar (InSAR). Interferograms covering the Hector Mine epicentral region were studied for possible slip along the Bullion and Lavic Lake faults by both visual inspection and a matched filter technique intended to emphasize slip located at the nucleation point. Some indications of possible deformation associated with the 5 July 1992 M L 5.4 Pisgah event was observed, but high decorrelation prevented a conclusive determination. We have seen no evidence for precursory slip in the epicentral region up to 30 days before the Hector Mine event. We estimated that the slip equivalent to a M w 4.5 event would have been observable in the months before the Hector Mine event, and this places an upper bound on the long-term precursory slip, had it occurred. We have noted that InSAR is well suited for detecting precursory slip in general due to the high spatial resolution and the lack of ground instrumentation required but that the detection level depends on the depth and orientation of the slip. [ Back ]

Regional waveform propagation is characterized in the Arabian Peninsula using data from a temporary network of broadband seismometers. Between November 1995 and March 1997, 332 regional (delta

We analyze 243 three-component broadband digital seismograms of aftershocks from the M s = 7.3 Suusamyr, Kyrgyzstan, earthquake to determine seismic attenuation in the northern Tien Shan. P g , S g , and S m S body waves and S coda waves were used to estimate the frequency-dependent ( f = 1.2-30 Hz) attenuation and scattering parameters of the crust and upper mantle as a function of depth. Using the equation Q(f) = Q 0 f n for multiple layers, we find that Q 0 increases with depth from 76 (upper crust) to 1072 (upper mantle), and the value of n decreases from 0.99 to 0.29 over the same range. The Q coda results also demonstrated an azimuthal dependence: Q 0 = 736 in the north-south direction and Q 0 = 494 in the east-west direction. There is a strong 2 ϕ dependence on azimuth for high frequencies (> 1.2 Hz). The depth and azimuthal dependence of the quality factor show that the Q is complicated and three dimensional. Estimates of the inhomogeneity scale a show two types of multiple scatterers (Wu and Aki, 1985): a velocity perturbation with a = 0.5-3.0 km and an impedance perturbation with a = 0.052-0.413 km. It appears that a increases with depth. The coefficient of scattering decreases from g 0 > f = 0.0055 km −1 at h = 0-6 km to 0.0020 km −1 at h = 6-11 km and 0.0048 km −1 at h = 11-15 for forward scattering and g π > f = 0.0006 km −1 at depth of low crust and upper mantle for backscattering. Estimates of seismic albedo B 0 show that the primary source of attenuation is intrinisc anelasticity, and the variation of Q 0 and n indicates that the level of heterogeneity varies with depth, possibly due to pressure. The lateral variation of Q 0 can be connected with azimuthal anisotropy in the upper mantle related to current deformation under the Tien Shan.

We determined crustal and lithospheric mantle velocity structure beneath the Arabian Shield through the modeling of receiver function stacks obtained from teleseismic P waves recorded by the 9 station temporary broadband array in western Saudi Arabia. The receiver function deconvolution technique was used to isolate the receiver-side PS mode conversions. A grid search method, which should yield an unbiased global minimum, was used to solve for a shear wave velocity model that is optimal and has the minimum number of layers needed to fit the receiver function waveform. Results from this analysis show that the crustal thickness in the shield area varies from 35 to 40 km in the west, adjacent to the Red Sea, to 45 km in central Arabia. Stability tests of each solution indicate that the models are relatively well constrained. We have also observed evidence for a large positive velocity contrast at sub-Moho depths at four stations at depths of 80 to 100 km. This discontinuity may represent a change in rheology in the lower part of the lithosphere or remnant structure from the formation of the Arabian Shield.

We investigated the Suusamyr, Kyrgyzstan, earthquake of 19 August 1992, using aftershock data, teleseismic body-wave modeling, and field observations. Aftershocks were recorded by the IRIS Kyrgyzstan broadband network, a temporary six-station aftershock network, and a regional network operated by the Kyrgyz Institute of Seismology. The aftershocks, which range in depth from the surface to 18 km, defined a 50 ± 10-km-long rupture zone that dips 50° ± 13° to the south and strikes roughly east-west. The base of the eastern end of the aftershock zone shallowed to the east along strike and may represent a lateral ramp. The surface ruptures also had an east-west strike and dipped south, but the total length (less than 4 km) was much shorter than the aftershock zone. A teleseismic body-wave inversion, using a point source and a directivity correction, yields a focal mechanism with a strike of 221°, dip of 46°, and a slip of 43°. We obtained a moment of 4.1 × 1019 N-m with a centroid depth between 5 and 21 km. The rupture propagated along an azimuth of 330° ± 60°, which matches the relative location of the mainshock with respect to the aftershock zone. The results of the aftershock study and teleseismic inversion yield a clear picture of the fault geometry of a large-thrust earthquake.

The MS = 7.3 Suusamyr earthquake of 19 August 1992 was a large, thrust-type earthquake in the northern Tien Shan of Kyrgyzstan, an intracontinental mountain belt in central Asia. Focal mechanisms of both the mainshock and 13 moderate-sized aftershocks are consistent with a seismotectonic setting that is dominated by NNW-SSE horizontal compression, which manifests itself in reverse faulting along roughly east-west trending, steeply dipping fault planes. The earthquake produced surface faulting at two widely separated locations, along two different fault segments, the total length of which was less than 4 km. Detailed measurements at one of the locations indicate a net slip of at least 4.2 ± 0.4 m. A wide variety of secondary surface effects was observed in the macroseismic zone that extended over an area of 2500 km2. The lack of extensive surface rupture from such a large event can be explained by a combination of (1) redistribution of the net slip at depth among the secondary splays that branches out from the main fault near the surface and (2) variable surface slip over the fault length. The active deformation associated with this event documents a structural style that involves steeply dipping, reverse faults extending from mid-crustal depths to the surface at nearly uniform dip, accommodating crustal shortening in the interior of the Tien Shan.

We used teleseismic travel time residuals to determine lateral velocity variations of the crust and upper mantle in the Pamir-Hindu Kush region in Tadjikistan and Afghanistan. Data from 29 analog seismic stations in Tadjikistan and northern Afghanistan were used to determine travel time residuals for 210 teleseismic events ranging in distance from 28° to 87° and covering a broad range of azimuths. We inverted for velocity perturbations over a rectangular grid with a block size of 99 × 99 km. The model extended to a depth of 350 km with a 50-km-thick first layer and two 150-km-thick deeper layers. The results show a strong and well-resolved zone of high velocities in the upper mantle at depths greater than 200 km, coincident with the location of the Hindu Kush seismic zone. No clear velocity perturbations are associated with the Pamir seismic zone. Above 200 km little correlation is observed with the seismic zone, but indications of thicker crust under the Pamir and thinner crust under the Tadjik Depression are seen. The high velocities are most likely caused by the presence of oceanic lithosphere at depth.

The northern Tien Shan of Central Asia is an area of active mid-continent deformation. Although far from a plate boundary, this region has experienced 5 earthquakes larger than magnitude 7 in the past century and includes one event that may as be as large as Mw 8.0. Previous studies based on GPS measurements indicate on the order of 23 mm/yr of shortening across the entire Tien Shan and up to 15 mm/year in the northern Tien Shan (Figure 1). The seismic moment release rate appears comparable with the geodetic measured slip, at least to first order, suggesting that geodetic rates can be considered a proxy for accumulation rates of stress for seismic hazard estimation. Interferometric synthetic aperture radar may provide a means to make detailed spatial measurements and hence in identifying block boundaries and assisting in seismic hazard. Therefore, we hoped to define block boundaries by direct measurement and by identifying and resolving earthquake slip. Due to political instability in Kyrgzystan, the existing seismic network has not performed as well as required to precisely determine earthquake hypocenters in remote areas and hence InSAR is highly useful. In this paper we present the result of three earthquake studies and show thatmore » InSAR is useful for refining locations of teleseismically located earthquakes. ALOS PALSAR data is used to investigate crustal motion in the Tien Shan mountains of Central Asia. As part of the work, considerable software development was undertaken to process PALSAR data. This software has been made freely available. Two damaging earthquakes have been imaged in the Tien Shan and the locations provided by ALOS InSAR have helped to refine seismological velocity models. A third earthquake south of Kyrgyzstan was also imaged. The use of InSAR data and especially L band is therefore very useful in providing groundtruth for earthquake locations.« less

A seismic attenuation map of regional phase Pg is constructed for the northern Middle East using two-station frequency-dependent Q measurements and seismic attenuation tomography. Pg is widely used in source discrimination, but its attenuation behavior is not well understood. We investigate the functional form of the geometrical spreading of Pg for both uniform and more complex seismic velocity structures. We find that there is significant trade-off between attenuation and geometrical spreading of Pg , and we quantify this trade-off to interpret the observed Pg attenuation in the Middle East. The northern Middle East attenuation tomographic images show significant lateral Q Pg variations, which may be caused by lateral variations of crustal rheology if intrinsic attenuation dominates the seismic attenuation mechanism of this region. We observe very large variations in the Q Pg model, such as low Q Pg within the Anatolian plate and high Q Pg within much of the stable Arabian plate. The low Q Pg anomalies generally coincide with active fault systems or Quaternary volcanisms. In order to perform a systematic comparison with Lg propagation, we have also updated the Q Lg map of Zor et al. (2007). These two new maps provide estimates for crustal Q α ( Pg ) and Q β ( Lg ) for the northern Middle East.

[1] We examine the potential triggering relationship between large earthquakes and methane mud volcano eruptions. Our data set consists of a 191-year catalog (1810–2001) of eruptions from 77 volcanoes in Azerbaijan, central Asia, supplemented with reports from mud volcano eruptions in Japan, Romania, Pakistan, and the Andaman Islands. We compare the occurrence of historical regional earthquakes (M > 5) with the occurrence of Azerbaijan mud volcano eruptions and find that the number of same-day earthquake/eruption pairs is significantly higher than expected if the eruptions and earthquakes are independent Poisson processes. The temporal correlation between earthquakes and eruptions is most pronounced for nearby earthquakes (within ∼100 km) that produce seismic intensities of Mercalli 6 or greater at the location of the mud volcano. This assumed magnitude/distance relationship for triggering observed in the Azerbaijan data is consistent with documented earthquake-induced mud volcano eruptions elsewhere. We also find a weak correlation that heightened numbers of mud volcano eruptions occur within 1 year after large earthquakes. The distribution of yearly eruptions roughly approximates a Poisson process, although the repose times somewhat favor a nonhomogenous failure rate, which implies that the volcanoes require some time after eruption to recharge. The volcanic triggering likely results from some aspect of the seismic wave's passage, but the precise mechanism remains unclear.

[1] Interferometric synthetic aperture radar (InSAR) measurements show a consistent, 40-km2 wedge-shaped area of deformation partially bounded by a branch of the Coyote Creek fault (a southern extension of the San Jacinto fault) in Imperial County, California, west of the Salton Sea. The deformation is centered at 33.1 N latitude, 116.0 W longitude. 18 ERS-1 and ERS-2 (descending) interferograms falling within 1992 to 2000 are analyzed. An average line-of-sight range change over the area of 6 ± 3 mm per year away from the satellite is observed with peak values up to 12 ± 3 mm per year. The southwestern edge of the deformation is partially bounded by a fault segment that ruptured in the 1968 Mw 6.5 Borrego Mountain earthquake and which also showed triggered slip after the 1987 Superstition Hills earthquakes. The southeastern edge of the deformation also coincides with a mapped fault. The deformation is centered on a farming area that has pumped approximately 5.8 × 10−6 m3 per year of groundwater from 5 wells on the property and which shows declining water levels of 1.4 m per year. The area of highest change appears to be centered on location of the wells and away from the faults. The aquifer is at a depth of roughly 100 to 200 m and consists of sands with interbedded clays. It appears that the most likely explanation is subsidence due to groundwater withdrawal in a fault-bounded aquifer rather than tectonic slip.

The research training activities started by identifying and picking seismic events from various broadband arrays and networks. The next step was to associate these events with existing catalog locations to build databases of local, regional and teleseismic events which are being used in this research project as well as other seismic verification projects at our institute and also other universities. The data processing aspects included learning to use the CSS 3.0 database format to allow the management of datasets with thousands of events. The seismic processing included identification of local, regional, and teleseismic phases which are essential for seismic discrimination research. This involved learning the TCLITK language and the application of this knowledge to provide a graphical user interface to build CSS databases. This program is being developed to support field deployments of seismic stations which will ensure the proper documentation of instrument responses, site locations, and calibration parameters. In addition, this software has been used to support deployments of the Wyoming portable broadband seismic and infrasonic experiments, and with all aspects of data assembly, data processing, data distribution to the research community.