Active Geological Structures Research Articles

Pleistocene terrace formation, Quaternary rock uplift rates and geodynamics of the Hellenic Subduction Zone revealed from dating of paleoshorelines on Crete, Greece

Quaternary paleoshorelines are common landforms on the island of Crete, a forearc high above the Hellenic Subduction Zone. These geomorphic markers are useful on Crete and elsewhere in determining coastal uplift rates, the identification of active geologic structures, and to constrain geodynamic models and seismic hazards. Controversy exists in the literature regarding the formation mechanisms and age of late Pleistocene paleoshorelines on Crete that has led to competing models of the uplift history, tectonic evolution, and seismic hazards of the Hellenic forearc. We present new mapping and results from luminescence and radiocarbon geochronology of paleoshoreline deposits that constrain the spatial and temporal pattern of rock uplift around the Cretan coastline. Existing and new radiocarbon data are variable and show no obvious age-elevation trends within individual terrace sequences. By contrast, nearly all luminescence ages, some from shorelines dated with radiocarbon, show positive age-elevation trends and range from 60–220 ka suggesting that all dated paleoshorelines are beyond the limits of radiocarbon. We propose that the inconsistencies between the different geochronological methods are the result of secondary contamination of young carbonate, possibly from meteoric waters, that bias radiocarbon in Cretan Pleistocene marine fossils. Most luminescence ages closely correlate with the timing of mid-to-late Pleistocene relative sea level highstands, consistent with stratigraphic observations. Calculated coastal uplift rates using a Monte-Carlo error analysis range from ∼0–1.2 mm/yr; the lowest uplift rates are found along the northern and eastern coasts of the island, while the most rapid are focused along the southern and western coasts where active normal faults are observed offsetting paleoshoreline sequences. Based on this new data, we favor a tectonic model where slip along upper crustal normal faults acts to locally augment a steady regional signal of uplift along the south and west coast, interpreted to result from the deep underplating of rock at the base of the subduction wedge beneath Crete. Arcward of the contact between the upper plate Moho and the top of the subducting slab, crustal thinning will occur in the orogenic wedge resulting in subsidence along the north coast of Crete.

Development of local magnitude scale for the Northern Punjab, Pakistan

We developed a local magnitude scale for the Northern Punjab (Potwar Plateau and Salt Range), using seismic data of CES (Centre for Earthquake Studies). The region is tectonically stable, but surrounded by active geological structures (i.e., Main Boundary Thrust, Sulaiman Range, and Jhelum Fault). The imparted stresses adjust both seismically (moderate to small magnitude earthquakes) and aseismically in decollement. Previously, Southern California magnitude scale was being used to determine local magnitude for compilation of seismic catalog. Difference in geology and tectonics between Southern California and Northern Punjab may lead to systematic errors in hazard assessment based on this catalog. To address this problem, we selected 231 seismic events for a period of 07 years with ML 2.0 and above, that correspond to 2800 records on 21 seismic stations. We chose data of seismic events with hypocentral distance less than 600 km and recorded on five stations at least. We then inverted the synthetic Wood-Anderson amplitudes of selected data for station and distance corrections. Accordingly, the new magnitude scale for Northern Punjab is given by the following: ML = logA + 0.869log(r) + 0.00115(r) − 1.53, where A is the amplitude in nanometers on synthetic Wood-Anderson seismograph and r is the hypocentral distance in kilometers. We observed lower attenuation of seismic waves in our study area as compared to Southern California. Lower standard deviation (i.e., reduction in variance to 45.4% ) in magnitude residuals shows that there is less deviation for newly developed scale as compared to that of Southern California scale. Values of station correction factors for different stations of local network vary between − 0.5 to + 0.5, which suggest variation in station site effects.

The application of the face-perpendicular preconditioning technique for de-stressing seismically active geological structures

ABSTRACTA trial on de-stressing a dyke that was located 60 m ahead of mining faces was conducted through drilling face-perpendicular preconditioning holes that intersected and passed the dyke by two metres. A sticky explosive (Ug101s) with a density of 1.1 g/cc, charging amass of 30.4 kg, powder factor of 1.3 kg/tonne, with gassing gap and 5 m long tamping material were used. After detonating the holes, a small seismic magnitude was noted. As mining progressed towards the dyke and passing through the dyke, good ground conditions were observed. Numerical modelling was conducted to simulate rate of energy release (RER), major principal stress ahead of the mining faces and simulation of the ride. The results of the study showed a gradual decrease of sigma 1,RER and high possibility of large seismic events to occur when mining through the dyke and also increase in the ride at the vicinity of the dyke.

Los mayores sismos en Argelia en la época moderna: las fallas de El Asnam y Zemmouri-Boumerdès

Algeria has experienced many destructive earthquakes during the last few centuries (e.g., Ayadi and Bezzeghoud, 2015). The city of El Asnam (formerly Orleanville, today Chlef) was severely damaged in 1954 and 1980 by magnitude 6.7 and 7.3 earthquakes, respectively. On October 10, 1989, a magnitude 5.9 earthquake struck the Mont Chenoua-Tipasa coastal area approximately 150 km west of Zemmouri, which is where the May 21, 2003 earthquake occurred (Mw6.8). Many other large historical and instrumental earthquakes have severely damaged the coastal cities of Algeria over the last few centuries (i.e., around Algiers, Oran, Mascara, Djidjelli, Constantine and Bejaia). These earthquakes suggest active deformation of the margin in conjunction with the clear offshore extent of active coastal faults. According to several studies, the main active geological structures around El Asnam, Algiers, Zemmouri and Boumerdes have experienced several disastrous earthquakes. Many other earthquakes have occurred in and around the Chlef and Mitidja Basins, underlining the seismic activity in the area. In this chapter, we highlight the main characteristics of the two largest earthquakes that have occurred in Algeria in the modern period: the El Asnam earthquakes of September 9 (Mw6.7) and October 10 1980 (Mw7.3), and the Zemmouri-Boumerdes earthquake of May 21, 2003, (Mw6.8).

Continental crust anisotropy measurements from tectonic tremor in Cascadia

AbstractWe present new observations of crustal anisotropy in the southern Cascadia fore arc from tectonic tremor. The abundance of tremor activity in Oregon and northern California during slow‐slip events offers an enormous amount of information with which to measure and analyze anisotropy in the upper brittle continental crust. To accomplish this, we performed analyses of wave polarization and shear wave splitting of tectonic tremor signals by using three component broadband seismic stations. The splitting times range between 0.11 and 0.32 s and are consistent with typical values observed in the continental crust. Fast polarization azimuths are, in general, margin parallel and trend N‐S, which parallels the azimuths of the maximum compressive stresses observed in this region. This pattern is likely to be controlled by the stress field. Comparatively, the anisotropic structure of fast directions observed in the northern section of the Cascadia margin is oblique with respect to the southern section of Cascadia, which, in general, trends E‐W and is mainly controlled by active faulting and geological structures. Source distribution analysis using a bivariate normal distribution that expresses the distribution of tremors in a preferred direction shows that in northern California and Oregon, the population of tremors tends to distribute parallel to fast polarization azimuths and maximum compressive stresses, suggesting that both tremor propagation and anisotropy are influenced by the stress field. Results show that the anisotropy reflects an active tectonic process that involves the northward movement of the Oregon Block, which is rotating as a rigid body. In northern Cascadia, previous results of anisotropy show that the crust is undergoing a shortening process due to velocity differences between the Oregon Block and the North America plate, which is moving more slowly with respect to the Oregon Block, making it clash against Vancouver Island.

Neogene oblique convergence and strain partitioning along the North Tabriz Fault, NW Iran

The North Tabriz Fault is one of the main active geological structures in NW Iran. It is reactivated under a pure-shear dominated transpressional tectonic regime induced by high angle (∼50°) oblique convergence between the Arabia and Eurasia plates. The first stage structures in the study area are folds and thrust faults that are mostly observed in Miocene sedimentary rocks and are cut by right-lateral strike-slip faults that are part of the North Tabriz Fault. Structural analysis of the North Tabriz Fault revealed flower structure geometry with thrust faults and related folds on both sides of the fault and strain partitioning. From GPS data, 7.3mm/year of right lateral plate motion has been calculated for NW Iran with 57–72% strike-slip partitioning, resulting in a maximum right-lateral slip rate for the North Tabriz Fault of 4.2–5.3mm/year. Since the total strike-slip displacement along the NTF has been estimated at 17±3km, with the slip-rate of 4.2–5.3mm/year, the maximum age of inception of the NTF strike-slip movement was at 3.2–4Ma (Upper Pliocene).

Earthquake relocations, crustal rheology, and active deformation in the central–eastern Alps (N Italy)

A revised seismic catalogue (1994–2007) for the central–eastern Alps (N Italy) is presented. 396 earthquake relocations, for local magnitudes in the 1.2–5.3 range, are performed using a 3D crustal velocity structure and probabilistic locations. The location procedure is validated by computing a set of 41 quarry shot solutions and all the results, both about shots and seismic events, are compared with those obtained using the routine location procedure. Results are shown for five contiguous seismotectonic domains, as supported by geological and geophysical evidence (e.g., fault systems, crustal tomography, focal mechanisms types). Earthquake hypocentres are mostly located in the upper crust (0–15km of depth), in good agreement with thermo-rheological models about the brittle–ductile transitions (8–9km of depth) and total crustal strengths (1.0–2.0TN m−1). Epicentres are clustered and/or aligned along present-day active geological structures. The proposed seismotectonic model shows dominant compression along the Giudicarie and Belluno–Bassano–Montello thrusts, with strain partitioning along the dominant right-lateral strike-slip faults of the Schio–Vicenza domain. The present-day deformation of the Southern Alps and the internal Alpine chain is compatible with Adria indentation and the related crustal stress distribution.

Habitat Inventory Parameters and Drainage Analysis of River Siang in Arunachal Pradesh

River Siang is the one of the major rivers of Arunachal Pradesh and also an important influent tributary leading to the mighty River Brahmaputra. River Siang is Hill-Stream 1st order river; has colluvial valley segment and pool-riffle type of reach. This reach type is most commonly associated with small to mid-size streams and is a quite prevalent type of reach in the rheophilic zones. Pools and riffles alternating with cascades are generally found to dominate the micro-habitat type with frequent occurrence of trench pools. The substrate type has been found to be dominated by bedrocks, boulders, gravels and cobbles. An analysis of the drainage network of a part of River Siang was undertaken to reveal the role of drainage water activity of the area. A number of fluvial geomorphic dissimilarities have been identified in the area. A prominent annular pattern is observed in the central part of the area. The total length of River Siang in Arunachal Pradesh is 293.9 km. This study revealed that the development of topography and drainage system of the study area have been influenced by active sub-surface geological structures.

Atmochemical mercury dispersion aureoles over active geologic structures of the northern Sea of Japan

In the autumn of 2010, contrasting dispersion aureoles of atomic mercury were revealed in the northern Sea of Japan, in the vicinity of the Vityaz’ and Alpatov Rises. Based on the elimination method, the assumption is made that the aureoles resulted from the supply of mercury from hydrothermal or water-gas bottom sources through the sea water column, either in gas bubbles or as a result of diffusion and turbulent mixing. It is inferred that gas-mercury measurements can be used in geological research in sea water areas.

Combined Regional Gravity Model of the Andean Convergent Subduction Zone and Its Application to Crustal Density Modelling in Active Plate Margins

The Central Andean subduction system is one of the most active geological structures on Earth. Although there have been a few previous studies, the structure and dynamics of the system are still not well understood. In the present study, we determine a combined regional gravity model of the Andean convergent subduction region for constraining lithospheric models. After a thorough validation and cleaning of the terrestrial gravity and height databases, the method of Least Squares Collocation was applied to consistently combine terrestrial and satellite gravity data, putting much emphasis on the stochastic modelling of the individual data components. As a result, we computed the first high-resolution regional gravity model of the study region that includes GOCE satellite gravity information. The inclusion of GOCE is an essential distinction from the independent global gravity model EGM2008. Validation against EGM2008 reveals that our regional solution is very consistent in regions where terrestrial gravity data are available, but shows systematic differences in areas with terrestrial data gaps. Artefacts in the EGM2008 of up to 150 mGal could be identified. The new combined regional model benefits from the very homogeneous error characteristics and accuracy of GOCE gravity data in the long-to-medium wavelengths down to 80–100 km. Reliable density modelling became possible also in the region of Central Andes, which lacks terrestrial gravity data. Finally, density models were adapted to fit the new regional gravity field solution. The results clearly demonstrate the capabilities of GOCE to better constrain lithospheric models.

Assessment of the geodynamical settings around the main active faults at Aswan area, Egypt

The proper evaluation of the level of crustal deformations in the Aswan region, especially around the main active faults, is crucial due to the existence of one major artificial structure: the Aswan High Dam. This construction created one of the major artificial lakes in the world: Lake Nasser. The Aswan area is considered as an active seismic area in Egypt due to the frequent recurrence of felted earthquakes. Two earthquakes occurred in the region (Kalabsha fault) after the construction of the Aswan High Dam: November 14, 1981 (ML = 5.6) and December 26, 2011 (ML = 4.1). The main goal of this study is to evaluate the active geological structures that can potentially affect the Aswan High Dam and that are being monitored in detail. For implementing such objective, several techniques (namely magnetic, seismic and GPS) have been utilized. A detailed land magnetic survey was carried out for the total component of the geomagnetic field using two proton magnetometers. The obtained magnetic results reveal that there are three major parallel faults affecting the area. The most dominant magnetic trend strikes those faults in the WNW-ESE direction. The seismicity and the fault plane solution associated with the December 26, 2011 earthquake have been also analyzed. The source mechanism of this event delineates two nodal planes. The trending ENE-WSW to E-W is consistent with the direction of the Kalabsha fault and its extension towards east. The trending NNW-SSE to N-S is consistent with the N-S fault trending. The movement along the ENE-WSW plane is right lateral, while left lateral along the NNW-SSE plane. Based on the estimated relative motions using GPS, dextral strike-slip motions at the Kalabsha and Seiyal fault systems are identified by the velocity gradient changes between the southern and northern stations. However, at the area between Kalabsha and Seiyal faults, other relative movements are also observed, which is consistent with other set of faults (N-S).

About this title ‐ The Aeolian Islands Volcanoes

The Aeolian Islands form one of the most active geological structures in the Mediterranean area, comprising a number of active (Stromboli and Vulcano) and dormant (Panarea and Lipari) volcanoes. They have attracted the attention of scientists in modern and historical times and are the cradle of the scientific discipline of volcanology. This Memoir provides information on geological features of the Aeolian Islands volcanoes at a regional scale and for each island. The stratigraphy, structural evolution, eruptive and magmatic history of the Islands is presented, along with the geodynamic setting of the Aeolian volcanism and implications for magma origin and evolution processes. Particular focus is given to the active and dormant volcanoes and the related natural hazards. It includes new 1:10 000-scale geological maps of the Aeolian Islands and bathymetric maps of sectors of the Aeolian archipelago, together with an extended dataset of rock compositions.

Plio–Quaternary tectonic regime changes in the transition zone between Alborz and Kopeh Dagh mountain ranges (NE Iran)

This paper is concerned with the changes in the Plio–Quaternary stress states in NE Iran and provides evidence for regional active deformation across a wide transition zone between the Alborz and Kopeh Dagh mountains. The Arabia–Eurasia convergence is involved in the strike–slip faulting along NE-trending left-lateral faults in the eastern Alborz as well as NW-trending right-lateral faults in the western Kopeh Dagh. The inversion result of fault kinematic data (slip-vector measurement of fault plane and focal mechanisms) strongly indicates an active transpressional tectonic regime in the study area. We provide evidence for drastic temporal changes in the stress state during the Plio–Quaternary based on the inversions of fault kinematic data. A regional transpressional tectonic regime with a mean N036 ± 20°E trending horizontal σ 1 is representative for the modern stress state. The older state reveals compressional to transpressional tectonic regimes comprising a N135 ± 20°E trending horizontal σ 1. The modern transpressional tectonic regime characterized by a regional NE-trending σ 1 is consistent with the inversion of earthquake focal mechanisms that yield a N47°E trending σ 1 for the present day stress state. The kinematic results are significantly homogeneous and mechanically compatible with the active geological structures, in the way that reverse and strike–slip faulting are coherent with a single σ 1 direction.

Bathymetry and active geological structures in the Upper Gulf of California

Bathymetric surveys made between 1994 and 1998 in the Upper Gulf of California revealed that the bottom relief is dominated by narrow, up to 50 km long, tidal ridges and intervening troughs. These sedimentary linear features are oriented NW-SE, and run across the shallow shelf to the edge of Wagner Basin. Shallow tidal ridges near the Colorado River mouth are proposed to be active, while segments in deeper water are considered as either moribund or in burial stage. Superposition of seismic swarm epicenters and a seismic reflection section on bathymetric features indicate that two major ridge-troughs structures may be related to tectonic activity in the region. Off the Sonora coast the alignment and gradient of the isobaths matches the extension of the Cerro Prieto Fault into the Gulf. A similar gradient can be seen over the west margin of the Wagner Basin, where in 1970 a seismic swarm took place (Thatcher and Brune, 1971) overlapping with a prominent ridge-trough structure in the middle of the Upper Gulf. It is believed that these major elongated features can be linked to active geological structures reflecting the geometry of the deep basement in the Wagner Basin.

The 2006-2007 Earthquake Sequence at Bar Harbor, Maine

ABSTRACT One purpose of monitoring earthquake activity in northeastern North America is to discover which geologic structures are seismically active in this region. If seismically active structures can be found, they can be studied to decipher their seismic history and their potential for strong earthquakes. No seismically active geologic structures have yet been confirmed in the northeastern United States (Ebel and Kafka 1991). The only earthquake with observed surface faulting in northeastern North America took place in the Ungava Peninsula of northern Quebec in 1989 (Adams et al. 1991). Other than some minor offsets of glacial striations (Oliver et al. 1970), no geologic evidence of Holocene surface faulting in the northeastern United States has been reported in the literature. Furthermore, the seismicity that has been detected by modern regional seismic networks in the northeastern United States does not align convincingly along known or suspected geologic structures. Nevertheless, the persistence of small-earthquake activity over time and the historic occurrences of past damaging earthquakes ( e.g. , Ebel 1996; Ebel 2000; Ebel et al. 2000; Ebel 2006) indicate that there must be some seismically active structures in the region that are capable of hosting earthquakes above magnitude 6.0. Because such earthquakes are capable of causing significant damage, there is great incentive to learn which structures are seismically active in this heavily populated region. Between fall 2006 and spring 2007, a sequence of earthquakes took place near the town of Bar Harbor on Mount Desert Island on the coast of Maine ([figure 1][1]). The largest earthquake in the sequence was Lg-magnitude (MLg) 4.2. It caused several rock falls in Acadia National Park near Bar Harbor, forcing the closure of several hiking trails and one road (figures [2][2] and [3][3]; ). Acadia National Park has many steep (almost vertical) rock faces of jointed granite, and some rockslides occur annually due to weathering effects. In this earthquake sequence, only the largest of the events generated sufficiently strong ground motions to generate rock falls of the unstable slopes. A water well at McFarland Hill near Bar Harbor that was being monitored by the U.S. Geological Survey showed an unusual drop in water level of about 2 m immediately following this event (the water level data can be accessed through the Web site ). The MLg 4.2 earthquake was felt over the southern two-thirds of Maine with a few felt reports from New Hampshire (see the community Internet intensity map at [http://pasadena.wr.usgs.gov/shake/ne/STORE/Xtib1\_06/ciim\_display.html][4]) and was the largest event centered in Maine since 1988. A total of 38 earthquakes were detected by seismic stations at regional distances from the Bar Harbor area from the start of the sequence on 22 September 2006 until the end of 2006. Two more events were detected in the spring of 2007. The purpose of this paper is to report on an analysis of the relative locations of the Bar Harbor earthquakes detected by the regional seismic network and to use the results of that analysis to assess what geologic structure might have been seismically active in this earthquake sequence. [1]: #F1 [2]: #F2 [3]: #F3 [4]: http://pasadena.wr.usgs.gov/shake/ne/STORE/Xtib1_06/ciim_display.html

Determination of geoid over South China Sea and Philippine Sea from multi-satellite altimetry data

A new computational procedure for derivation of marine geoid on a 2.5′ × 2.5′ grid in a non-tidal system over the South China Sea and the Philippine Sea from multi-satellite altimeter sea surface heights is discussed. Single-and dual-satellite crossovers were performed, and components of deflections of the vertical were determined at the crossover positions using Sandwell’s computational theory, and gridded onto a 2.5′ × 2.5′ resolution grid by employing the Shepard’s interpolation procedure. 2.5′ × 2.5′ grid of EGM96-derived components of deflections of the vertical and geoid heights were then used as reference global geopotential model quantities in a remove-restore procedure to implement the Molodensky-like formula via 1D-FFT technique to predict the geoid heights over the South China Sea and the Philippine Sea from the gridded altimeter-derived components of deflections of the vertical. Statistical comparisons between the altimeter-and the EGM96-derived geoid heights showed that there was a root-mean-square agreement of ±0.35 m between them in a region of less tectonically active geological structures. However, over areas of tectonically active structures such as the Philippine trench, differences of about −19.9 m were obtained.

平成16年 (2004年) 新潟県中越地震震源域の地表部における地形と地質構造

The Mid Niigata prefecture Earthquake occurred on October 23, 2004. Suzuki et al. (2004) and Maruyama et al. (2005a, 2005b) found small surface ruptures at Obirou and Aoshima areas. Suzuki et al. (2004) also argued that the earthquake was caused by movements of the Obirou Fault and the northern part of the Muikamachi-Bonchi-Seien fault. The aim of this report is to examine active geological structures and landforms in epicentral region of the earthquake. We carried out aerialphoto interpretation, geological survey, and geomorphometry by airborne laser scanning. As a result of our survey, the Suwatoge Flexure was found to be an active structure in the region, together with Obirou Fault and the Muikamachi-Bonchi-Seien fault. The Suwatoge Flexure is recognized as the fold on Uonuma formation (Plio-Pleistocene) and uplifts terraces in west/northwest direction; this is generally correspond with the earthquake source direction. The amount of vertical displacement in each terrace is as follows; more than 70m on Higher terrace (H2 surface), about 40m on Middle terrace (M1 surface) and about 10m on Lower terrace (L1 surface). The mean rate of vertical displacement is estimated 0.3m/103 year based on M1 Terrace surface covered by In-Kt Tephra [≥130, 000 year: Machida and Arai (2003)]. The Suwatoge Flexure is located at the eastern margin of the distributed area of aftershock epicenters, and its south end corresponds with that of the distribution of aftershock epicenters. The largest vertical movement of 71.5cm uplifts (GSI, 2004) as the co-seismic crustal deformation is located on the west side of the Suwatoge Flexure. Therefore, the formation of the Suwatoge Flexure were probably caused by activities of earthquake source faults.

Three-dimensional rheological structure of the lithosphere in the Ordos block and its adjacent area

The 3-D rheological structure of the lithosphere in the Ordos block and its adjacent area (32°–43°N, 102°–116°E) is obtained using iterative and averaging methods, based on the seismic velocity structure, thermal structure and composition of the lithosphere. The thermal structure is obtained from the newly published surface heat flow data sets. The brittle fracture mechanism is taken into account when the rheological structure is calculated. The strain rate obtained from GPS observation in the area under study is used to calculate the strength and the viscosity of the lithosphere. The results show that there are low-viscosity layers at the bottom of the upper crust, the lower crust and the bottom of the lithosphere both under the Ordos block and its adjacent regions, and the viscosity varies horizontally. The viscosity in grabens surrounding the Ordos block is one to two orders of magnitude lower than that in the Ordos block. The results also show that the rheological structure coincides with the major geological structure, below the major fault systems the viscosity is relatively low. The earthquakes with Ms≥ 4.0 occurred along the large active faults. Most of the hypocentres of the earthquakes are in the upper and middle crust with high viscosity. The maximum depth of the earthquake is above the viscosity contour line of 1022 Pa s. Numerical studies show that the active geological structures must be taken into account when the 3-D rheological structure is used for geodynamics study.

Identification of potentially active structures along the Sava river using topographic, and leveling line data

Anomalies in vertical displacement rates related to recent geodynamics were determined between Rateče and Ljubljana by comparing leveling line data with topography of the Sava river longitudinal profile. Beside the general trend showing increase of vertical displacement in the S-N direction, segmentation of the area is noted. The later suggests that active geological structures exist in the northern part of the Ljubljana basin and in the Upper Sava valley respectively.

Locations of selected small earthquakes in the Zagros mountains

The Zagros mountains of southern Iran are marked by a zone of high seismicity and accommodate a significant portion of the convergence between Arabia and Eurasia. Due to the lack of dense local seismic or geodetic networks, the inferred kinematics of the collision in Iran is mainly based on catalogs of teleseismically determined earthquake locations. We surveyed all Mw > 4.5 earthquakes in the Harvard Centroid Moment Tensor (HCMT) and International Seismological Centre (ISC) catalogs that occurred in the Zagros mountains during the period 1992–2002 and that were spanned by Interferometric Synthetic Aperture Radar (InSAR) images from the ERS 1 and 2 satellites. We invert the observed deformation for the best fitting point source, single fault plane, and distributed fault slip for four earthquakes and one unexplained deformation event. We find that we can precisely locate earthquakes that are too small to be well‐located by either the HCMT or ISC catalogs, allowing us to tie specific earthquakes to active geologic structures.