Source parameters of the Bhuj earthquake, India of January 26, 2001 from height and gravity changes

Chandrasekhar, D. V.

doi:10.1029/2004gl020768

Cited by 20 publications

(16 citation statements)

References 11 publications

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“…However they assumed a constant oblique rake of 77° over the entire fault plane and did not explore whether this secondary patch could have had a different rake. While attempting to constrain shallow slip with leveling data, Chandrasekhar et al [2004] found that strike‐slip motion dominated on a shallow fault for a model composed of 2 planar dislocations.…”

Section: Discussionmentioning

confidence: 99%

“…Due to the event's remote location, no strong motion and minimal geodetic data are available within the epicentral region. The only useful geodetic data in the region are from a triangulation network last surveyed in the 19th century [ Chandrasekhar et al , 2004] and scattered GPS observations [ Jade et al , 2002]. To supplement the geodetic data, Gahalaut and Bürgmann [2004] examined satellite images to infer surface deformation from the change in the distribution of surface water.…”

Section: Introductionmentioning

confidence: 99%

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InSAR constraints on the source parameters of the 2001 Bhuj earthquake

Schmidt

Bürgmann

2006

Geophysical Research Letters

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We present InSAR results of the coseismic displacement field for the January 2001 Bhuj earthquake. Using InSAR data along multiple tracks, we determine the optimal source parameters of the earthquake. The deformation pattern is first modeled assuming uniform slip on an elastic dislocation. A grid search is used to constrain the source location and finiteness assuming a strike, rake, and dip consistent with seismic studies. An inversion for the distributed slip places oblique reverse slip at depth with strike‐slip motion resolved at shallower depths. The estimated size of the event is Mw 7.6. Results also suggest that the postseismic response is minimal.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

InSAR constraints on the source parameters of the 2001 Bhuj earthquake

Schmidt

Bürgmann

2006

Geophysical Research Letters

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“…Scientists working on the Bhuj event therefore struggled to constrain the parameters of the fault rupture models of the earthquake. Existing geodetic observations include sparsely distributed leveling and gravity data [ Chandrasekhar et al ., ; Wallace et al ., ], flooding pattern variations observed in optical satellite images [ Gahalaut and Bürgmann , ], isolated ERS interferogram patches [ Schmidt and Bürgmann , ], and image offsets from optical images [ Copley et al ., ]. These geodetic observations, however, failed to provide information about the near‐field deformation of the earthquake.…”

Section: Introductionmentioning

confidence: 99%

Coseismic displacements from SAR image offsets between different satellite sensors: Application to the 2001 Bhuj (India) earthquake

Wang

Wei

Jónsson

2015

Geophysical Research Letters

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Synthetic aperture radar (SAR) image offset tracking is increasingly being used for measuring ground displacements, e.g., due to earthquakes and landslide movement. However, this technique has been applied only to images acquired by the same or identical satellites. Here we propose a novel approach for determining offsets between images acquired by different satellite sensors, extending the usability of existing SAR image archives. The offsets are measured between two multiimage reflectivity maps obtained from different SAR data sets, which provide significantly better results than with single preevent and postevent images. Application to the 2001 Mw7.6 Bhuj earthquake reveals, for the first time, its near‐field deformation using multiple preearthquake ERS and postearthquake Envisat images. The rupture model estimated from these cross‐sensor offsets and teleseismic waveforms shows a compact fault slip pattern with fairly short rise times (<3 s) and a large stress drop (20 MPa), explaining the intense shaking observed in the earthquake.

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“…Even if space geodetic techniques (GPS, SAR) are more and more used for seismic, volcanic, and tectonic studies, changes in levelling data between surveys are still very useful for the investigation of seismic and volcanic sources and post‐seismic and tectonic processes (e.g. Iio et al 2002; Chandrasekhar et al 2004; Amoruso et al 2005; Battaglia et al 2006).…”

Section: Introductionmentioning

confidence: 99%

Inversion of levelling data: how important is error treatment?

Amoruso

Crescentini

2007

Geophysical Journal International

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S U M M A R YEven if proper treatment of error statistics is potentially essential for the reliability of experimental data inversion, a critical evaluation of its effects on levelling data inversion is still lacking. In this paper, we consider the complete covariance matrix for levelling measurements, obtained by combining the covariance matrix due to measurement errors and the covariance matrix due to non-measurement errors, under the simple hypothesis of uncorrelated nonmeasurement errors on bench mark vertical displacements. The complete covariance matrix is reduced to diagonal form by means of a rotation matrix; the same rotation transforms the data to independent form. The eigenvalues of the complete covariance matrix give the uncertainties of the transformed independent data. This procedure can be used also with non-normal distributions of errors, in which case misfit functions other than χ 2 (e.g. the mean absolute deviation) are minimized. Here we focus on two test cases (the 1989 Loma Prieta earthquake and the 1908 Messina earthquake) inverting both real data and synthetics. The inversion of synthetic data sets does not evidence any systematic dependence of retrieved parameter values on the covariance matrix. Most retrieved fault parameter values are close to what used in the forward model, whatever covariance matrix is used. As a consequence, large discrepancies among results obtained using covariance matrices including different combinations of measurement and non-measurement errors when inverting measured and synthetic data sets would possibly indicate the need for further investigations. While measurement errors can be a priori evaluated, it is difficult to estimate non-measurement errors. Our synthetic tests using a uniform-slip rectangular fault in a homogeneous elastic half-space show that, if measurement errors have been correctly evaluated, average non-measurement errors can be estimated by choosing their weight inside the covariance matrix so that the ratio between the total square residual for the χ 2 best-fitting model and the number of degrees of freedom is about one. This result holds even if non-measurement errors are different from bench mark to bench mark and/or not normally distributed. In case of more complex models (e.g. one distributed-slip fault) it is difficult to estimate the actual number of degrees of freedom. Our synthetic tests show that this difficulty can be surmounted by using the Akaike Information Criterion, which actually decreases when turning from a uniform-slip inverse model to a distributed-slip inverse model only if the correct amount of non-measurement errors is included in the covariance matrix.

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Source parameters of the Bhuj earthquake, India of January 26, 2001 from height and gravity changes

Cited by 20 publications

References 11 publications

InSAR constraints on the source parameters of the 2001 Bhuj earthquake

InSAR constraints on the source parameters of the 2001 Bhuj earthquake

Coseismic displacements from SAR image offsets between different satellite sensors: Application to the 2001 Bhuj (India) earthquake

Inversion of levelling data: how important is error treatment?

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