Coseismic displacement field and slip distribution of the 2005 Kashmir earthquake from SAR amplitude image correlation and differential interferometry

Yajing Yan (1, 2) , Virginie Pinel (2) , Emmanuel Trouvé (1) , Erwan Pathier (2) , Jonathan Perrin (2) , Pascale Bascou (3) , François Jouanne (2)

1 LISTIC - Laboratoire d'Informatique, Systèmes, Traitement de l'Information et de la Connaissance
2 ISTerre - Institut des Sciences de la Terre
3 Mécanique des failles

The coseismic surface displacement field and slip distribution at depth due to the Kashmir earthquake (Mw = 7.6, 2005) have been analysed by different authors using subpixel correlation of synthetic aperture radar (SAR) images and optical images, teleseismic analysis, GPS measurements, as well as in situ field measurements. In this paper, first, we use 23 sets of measurement from subpixel correlation of SAR images and differential interferometry to retrieve the 3-D coseismic surface displacement field. The obtained horizontal and vertical components along the fault trace are then compared, respectively, to equivalent measurements obtained from subpixel correlation of two optical ASTER images and in situ field measurements. Second, the coseismic fault geometry parameters and slip distribution at depth are estimated. In addition to the one segment slip model as reported in previous work, a two segments slip model that better fits the surface fault break is proposed. The improvement of the two segments slip model in interpreting the measured displacement field is highlighted through comparison of residuals of both slip models. Taking advantage of differential interferometry measurements that provide precise and continuous information in the far field of the fault, firstly, a wedge thrust according to Bendick et al. to the Northwest of the main rupture built on our two segments model is tested. According to the obtained results, the residual of the two segments main rupture plus wedge thrust model is slightly smaller than the residual of the two segments model to the Northwest of the Balakot-Bagh fault. Secondly, we test the sensitivity of our slip model to the presence of slip along a décollement as evidenced by Jouanne et al. through post-seismic analysis. The results indicate that the estimations of the coseismic displacement field and slip distribution in this paper are not significantly biased by such post-seismic displacement and that most coseismic displacement is located on a ∼40° NE-dipping fault, as previously reported.

Mots clés: Image processing; Earthquake ground motions; Dynamics and mechanics of faulting

Domaines: Sciences de l'environnement

Yajing Yan, Virginie Pinel, Emmanuel Trouvé, Erwan Pathier, Jonathan Perrin, et al.. Coseismic displacement field and slip distribution of the 2005 Kashmir earthquake from SAR amplitude image correlation and differential interferometry. Geophysical Journal International, 2013, 193 (1), pp.29-46. ⟨10.1093/gji/ggs102⟩. ⟨hal-00817363⟩