The 2011 Mw 7.1 Van (Eastern Turkey) earthquake

Abstract

[1] We use interferometric synthetic aperture radar (InSAR), body wave seismology, satellite imagery, and field observations to constrain the fault parameters of the M w 7.1 2011 Van (Eastern Turkey) reverse-slip earthquake, in the Turkish-Iranian plateau. Distributed slip models from elastic dislocation modeling of the InSAR surface displacements from ENVISAT and COSMO-SkyMed interferograms indicate up to 9 m of reverse and oblique slip on a pair of en echelon NW 40°-54°dipping fault planes which have surface extensions projecting to just 10 km north of the city of Van. The slip remained buried and is relatively deep, with a centroid depth of 14 km, and the rupture reaching only within 8-9 km of the surface, consistent with the lack of significant ground rupture. The up-dip extension of this modeled WSW striking fault plane coincides with field observations of weak ground deformation seen on the western of the two fault segments and has a dip consistent with that seen at the surface in fault gouge exposed in Quaternary sediments. No significant coseismic slip is found in the upper 8 km of the crust above the main slip patches, except for a small region on the eastern segment potentially resulting from the M w 5.9 aftershock on the same day. We perform extensive resolution tests on the data to confirm the robustness of the observed slip deficit in the shallow crust. We resolve a steep gradient in displacement at the point where the planes of the two fault segments ends are inferred to abut at depth, possibly exerting some structural control on rupture extent.

Patterns and mechanisms of coseismic and postseismic slips of the 2011 M W 7.1 Van (Turkey) earthquake revealed by multi-platform synthetic aperture radar interferometry

“…Several papers have investigated the coseismic deformation, focal mechanisms and aftershocks of this event (Altiner et al, 2013;Elliott et al, 2013;Fielding et al, 2013;Irmak et al, 2012;Moro et al, 2014;Utkucu, 2013;Zahradník and Sokos, 2014). The mechanisms of the mainshock determined from geodetic observations and seismic waveforms are generally consistent.…”

“…In Profiles A-A', B-B', E-E' and F-F', uplift signals of up to 0.06 m can be observed near the fault trace above 38.65 °N in the CSK2 interferogram, which are believed to be due to aftershocks (Elliott et al, 2013).…”

“…The largest uncertainties in the dip-slip, < 0.8 m, are at 20 km depth ( Figure S3 interferogram using the data resolution-based resampling method as used for CSK data. Equal weights were applied in modelling for both ASAR and CSK1 LOS range changes, as in previous studies (Elliott et al, 2013). …”

“…Two geodetic models have also been published for this large event (Elliott et al, 2013;Fielding et al, 2013), both suggesting the maximum slip occurred at a depth of 12-14 km, but with different slip magnitudes and patterns. A complicated slip model with two-equal-size slip patches with a maximum of ~9 m at a depth of 12-14 km for both patches was determined by Elliott et al (2013), which may relate with the employed geometric model and inversion method.…”

“…However, both the magnitudes and patterns of slip vary between models. For example, two-equal-sized areas of slip each with maximum slip of ~9 m were calculated from InSAR observations by Elliott et al (2013), whilst another study that combined InSAR with a SAR pixel offset map and GPS data suggested only one slip patch with a maximum slip of ~ 4 m (Fielding et al, 2013). This discrepancy has not yet to be resolved.…”