IMPROVED SOURCE IMAGING OF THE KLEIFARVATN EARTHQUAKE, ICELAND, THROUGH A COMBINED USE OF ASCENDING AND DESCENDING INSAR DATA
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We re-investigated the surface deformation of the Kleifarvatn earthquake on Reykjanes Peninsula, an event that was dynamically triggered by a moderatesize magnitude 6.5 earthquake 80 km away on 17 June 2000. Two ERS-2 interferograms from descending and ascending tracks were formed and used in combination with campaign GPS measurements to invert for the source parameters of rectangular faults for the Kleifarvatn and the adjacent and smaller Nupshliðarhals earthquakes assuming uniform slip. With our more complete data set that includes the ascending ERS-2 data, we demonstrate an efficient suppression of model parameter trade-offs between fault dip and fault slip. We consider the correlated noise of InSAR by propagating the full data covariance to a weighting matrix, which balances the complete data set consistently. Our best model agrees not only with the regional faulting system, it is also supported by locations of recently relocated aftershocks.Keywords:
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We identify the source of the Mw = 6.4 earthquake that rocked north-central Albania on November 26, 2019 02:54 UTC. We use synthetic aperture radar interferograms tied to the time series of coordinates of two permanent Global Navigation Satellite System (GNSS) stations (DUR2 and TIR2). We model the source by inverting the displacement data. Assuming in our model a half-space elastic medium and uniform slip along a rectangular fault surface, we invert the 104 picked measurements on a couple of ascending and descending interferograms to calculate the parameters of the fault. All inversions made with different input parameters converge towards a stable and robust solution with root mean square (r.m.s.) residual of 5.4 mm, thus ~1/5 of a fringe. They reveal that the earthquake occurred deep in the crust on a low-angle fault (23°) dipping towards east with a centroid at 16.5 km depth. The best-fitting length and width of the fault are 22 and 13 km, and the reverse slip, 0.55 m. The seismic moment deduced from our model agrees with those of the published seismic moment tensors. This geometry is compatible with a blind thrust fault that may root on the main basal thrust, i.e., along the thrust front that separates Adria–Apulia from Eurasia. It is notable that there is a 123 ns yr−1 active shortening of the crust between the GNSS stations DUR2-TIR2 (equivalent to a shortening rate of 3.6 mm yr−1), and roughly in the east–west direction. Given this amount of strain the recurrence time of M6+ earthquakes along this fault should be of the order of 150 years.
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We use interferometric synthetic aperture radar (InSAR) and Global Positioning System (GPS) observations to investigate static deformation due to the 1999 M w 7.1 Hector Mine earthquake, that occurred in the eastern California shear zone.Interferometric decorrelation, phase, and azimuth offset measurements indicate regions of surface and near-surface slip, which we use to constrain the geometry of surface rupture.The inferred geometry is spatially complex, with multiple strands.The southern third of the rupture zone consists of three subparallel segments extending about 20 km in length in a N45ЊW direction.The central segment is the simplest, with a single strand crossing the Bullion Mountains and a strike of N10ЊW.The northern third of the rupture zone is characterized by multiple splays, with directions subparallel to strikes in the southern and central.The average strike for the entire rupture is about N30ЊW.The interferograms indicate significant alongstrike variations in strain which are consistent with variations in the ground-based slip measurements.Using a variable resolution data sampling routine to reduce the computational burden, we invert the InSAR and GPS data for the fault geometry and distribution of slip.We compare results from assuming an elastic half-space and a layered elastic space.Results from these two elastic models are similar, although the layered-space model predicts more slip at depth than does the half-space model.The layered model predicts a maximum coseismic slip of more than 5 m at a depth of 3 to 6 km.Contrary to preliminary reports, the northern part of the Hector Mine rupture accommodates the maximum slip.Our model predictions for the surface fault offset and total seismic moment agree with both field mapping results and recent seismic models.The inferred shallow slip deficit is enigmatic and may suggest that distributed inelastic yielding occurred in the uppermost few kilometers of the crust during or soon after the earthquake.
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On 18 January 2017, the 2016–2017 central Italy seismic sequence reached the Campotosto area with four events with magnitude larger than 5 in three hours (major event MW 5.5). To study the slip behavior on the causative fault/faults we followed two different methodologies: (1) we use Interferometric Synthetic Aperture Radar (InSAR) interferograms (Sentinel-1 satellites) and Global Positioning System (GPS) coseismic displacements to constrain the fault geometry and the cumulative slip distribution; (2) we invert near-source strong-motion, high-sampling-rate GPS waveforms, and high-rate GPS-derived static offsets to retrieve the rupture history of the two largest events. The geodetic inversion shows that the earthquake sequence occurred along the southern segment of the SW-dipping Mts. Laga normal fault system with an average slip of about 40 cm and an estimated cumulative geodetic moment of 9.29 × 1017 Nm (equivalent to a MW~6). This latter estimate is larger than the cumulative seismic moment of all the events, with MW > 4 which occurred in the corresponding time interval, suggesting that a fraction (~35%) of the overall deformation imaged by InSAR and GPS may have been released aseismically. Geodetic and seismological data agree with the geological information pointing out the Campotosto fault segment as the causative structure of the main shocks. The position of the hypocenters supports the evidence of an up-dip and northwestward rupture directivity during the major shocks of the sequence for both static and kinematic inferred slip models. The activated two main slip patches are characterized by rise time and peak slip velocity in the ranges 0.7–1.1 s and 2.3–3.2 km/s, respectively, and by ~35–50 cm of slip mainly concentrated in the shallower northern part of causative fault. Our results show that shallow slip (depth < 5 km) is required by the geodetic and seismological observations and that the inferred slip distribution is complementary with respect to the previous April 2009 seismic sequence affecting the southern half of the Campotosto fault. The recent moderate strain-release episodes (multiple M~5–5.5 earthquakes) and the paleoseismological evidence of surface-rupturing events (M~6.5) suggests therefore a heterogeneous behavior of the Campotosto fault.
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Brief Report| October 01, 2013 Coseismic Slip Distribution of the 24 March 2011 Tarlay (Myanmar) Mw 6.8 Earthquake from ALOS PALSAR Interferometry Jianbao Sun; Jianbao Sun State Key Lab. of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, No. 1, Huayanli Jia, Chaoyang District, P.O.Box 9803, 100029 Beijing, Chinasunjianbao@gmail.com Search for other works by this author on: GSW Google Scholar Zheng‐Kang Shen; Zheng‐Kang Shen Department of Earth and Space Sciences, University of California, Los Angeles, 3806 Geology, 595 Charles Young Drive East, Los Angeles, CA 90095‐1567 *Also at Department of Geophysics, Peking University, No. 5 Yiheyuan Road, Haidian District, 100871 Beijing, China. Search for other works by this author on: GSW Google Scholar Roland Bürgmann; Roland Bürgmann Department of Earth & Planetary Science, University of California, Berkeley, 389 McCone Hall, Berkeley, California 94720‐4767 Search for other works by this author on: GSW Google Scholar Xiwei Xu Xiwei Xu Institute of Geology, China Earthquake Administration, No.1, Huayanli Jia, Chaoyang District, P.O.Box 9803, 100029 Beijing, China Search for other works by this author on: GSW Google Scholar Bulletin of the Seismological Society of America (2013) 103 (5): 2928–2936. https://doi.org/10.1785/0120120365 Article history first online: 14 Jul 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Jianbao Sun, Zheng‐Kang Shen, Roland Bürgmann, Xiwei Xu; Coseismic Slip Distribution of the 24 March 2011 Tarlay (Myanmar) Mw 6.8 Earthquake from ALOS PALSAR Interferometry. Bulletin of the Seismological Society of America 2013;; 103 (5): 2928–2936. doi: https://doi.org/10.1785/0120120365 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyBulletin of the Seismological Society of America Search Advanced Search Abstract We investigate coseismic deformation of the 24 March 2011 Mw 6.8 Tarlay, Myanmar, earthquake using ALOS PALSAR data from both descending and ascending passes. Using high‐quality synthetic aperture radar interferograms and amplitude‐offset images, the nearly linear surface rupture is well traced along the western end of the Nam Ma fault and strikes ∼69°. From both descending and ascending pass Interferometric Synthetic Aperture Radar data and a rigorous maximum a posteriori probabilistic inversion method, we infer that the event involved mostly a pure left‐lateral strike‐slip rupture with near‐vertical geometry. Our one‐segment model shows that the maximum slip of ∼4.1 m occurred at ∼4 km depth, much larger than the slip at the surface. Both interferograms also reveal a small segment to the east of the main rupture, in a densely populated farming area. Our inversion of a two‐segment model shows a similar slip distribution on the main fault, in addition to ∼0.1–0.3 m left‐lateral slip with normal component on a 58° north‐dipping segment. The total seismic moment from the two‐segment model is 1.95×1019 N·m, equivalent to an Mw 6.79 earthquake, which is comparable to the U.S. Geological Survey seismic inversion estimate of 2.10×1019 N·m (Mw 6.84). The earthquake occurred within a group of east‐northeast‐striking left‐lateral strike‐slip faults near the Myanmar–Laos border, which are seismically active and reflect a system of actively clockwise rotating blocks.Online Material: Figures of InSAR observations, amplitude‐offset maps, InSAR deformation decomposition, one segment model inversion residuals, single data set inversion results, and tectonic setting. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
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The slip distribution of the 16 October 1999, M w 7.1, Hector Mine earthquake, California, is investigated in space and time by jointly inverting geodetic data and broadband teleseismic data constrained by reported surface offsets. The geodetic data consist of a dense network of Global Positioning System (gps) data and synthetic aperture radar (sar) interferograms from both ascending and descending satellite tracks. Considering the complexity of the earthquake rupture, our fault model has four partially overlapping segments discretized into 3 × 3 km2 patches. The seismic source parameters on each subfault are estimated using a nonlinear inversion scheme based on a simulated annealing method to explore the parameter space. We allow a variable rupture velocity and slip to vary in amplitude, direction, and duration. We first explore the space and time resolution of each data set and their combination with data synthetized from known slip distributions. We estimate the slip distribution from the different data sets inverted separately and finally perform a joint inversion of the combined data sets. The teleseismic data inversion exhibits a rather bad spatial resolution compared with the resolution power of the other data. The geodetic data nearly completely map the coseismic deformation field of the Hector Mine earthquake and strongly constrain the spatial distribution of the final slip and the fault geometry. The spatial resolution is expected to be best for the depth range of 0 to 10 km over the entire fault model. The joint inversion of both geodetic and seismic data provides a robust estimate of slip history that simultaneously fits the independent data sets in space and time. The Hector Mine earthquake is a right-lateral strike-slip event that presents a heterogeneous distribution of slip at shallow depth (<12 km). Most of the seismic moment is released in the vicinity of the hypocenter over two overlapping segments. The total seismic moment is 5.8·1019 N m (our joint inversion) with a peak displacement amplitude of about 6 m. The velocity rupture is comprised between 2 and 2.5 km/sec for a total duration of about 15 sec over an extent of about 50 km.
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Abstract. On 18 September 2004, an Mw= 5.5 earthquake struck the Huntoon Valley, California, USA. To measure the coseismic deformation field, we applied interferometric synthetic aperture radar (SAR) (InSAR) technique on ascending and descending SAR images from the ENVISAT satellite. Multi-temporal InSAR images were stacked to reduce the atmospheric artifact and other noise. Deformation signals are obvious across the northeast-trending, left-lateral strike-slip fault that produced the earthquake. Ascending and descending deformation maps allowed us to retrieve the east–west and vertical displacement components. Our results show that the displacement in the east–west component is between −3 and 3 cm while the vertical component is between −1 and 1 cm on both sides of the fault. Modeling the averaged deformation images from both descending and ascending tracks with an elastic dislocation source resulted in a best-fit 8 km-long by 3 km-wide fault model that strikes northeast at a depth of about 4.7 km. The magnitude calculated by InSAR data is Mw= 5.6, which is similar to that from the local earthquake catalog and slightly larger than estimates from global earthquake catalogs. Moreover, the InSAR-derived depth is similar to that from the local catalog; both are shallower than those reported in the global catalogs. Our results suggest that the earthquake parameters based on global seismic catalogs can be improved by high-resolution InSAR imagery and modeling.
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In this study, Sentinel-1 and Advanced Land Observation Satellite-2 (ALOS-2) interferometric synthetic aperture radar (InSAR) and global positioning system (GPS) data were used to jointly determine the source parameters and fault slip distribution of the Mw 6.6 Hokkaido eastern Iburi, Japan, earthquake that occurred on 5 September 2018. The coseismic deformation map obtained from the ascending and descending Sentinel-1 and ALOS-2 InSAR data and GPS data is consistent with a thrust faulting event. A comparison between the InSAR-observed and GPS-projected line-of-sight (LOS) deformation suggests that descending Sentinel-1 track T046D, descending ALOS-2 track P018D, and ascending ALOS-2 track P112A and GPS data can be used to invert for the source parameters. The results of a nonlinear inversion show that the seismogenic fault is a blind NNW-trending (strike angle ~347.2°), east-dipping (dip angle ~79.6°) thrust fault. On the basis of the optimal fault geometry model, the fault slip distribution jointly inverted from the three datasets reveals that a significant slip area extends 30 km along the strike and 25 km in the downdip direction, and the peak slip magnitude can approach 0.53 m at a depth of 15.5 km. The estimated geodetic moment magnitude released by the distributed slip model is 6.16 × 10 18 N · m , equivalent to an event magnitude of Mw 6.50, which is slightly smaller than the estimates of focal mechanism solutions. According to the Coulomb stress change at the surrounding faults, more attention should be paid to potential earthquake disasters in this region in the near future. In consideration of the possibility of multi-fault rupture and complexity of regional geologic framework, the refined distributed slip and seismogenic mechanism of this deep reverse faulting should be investigated with multi-disciplinary (e.g., geodetic, seismic, and geological) data in further studies.
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