A Joint Seismic and Geodetic Rupture Model for the 2013 Khash Intraplate Earthquake

The April 16th, 2013, Mw 7.8 earthquake east of Khash, Iran, occurred within the subducting Arabian plate, approximately 300 km north of the Makran coast. Although the level of intraplate seismicity in this area is relatively low, earthquakes down to a depth of 170 km roughly define a north-dipping subducting slab. Previous large regional earthquakes include an Mw7.2 event in 2011 with similar normal faulting mechanism and depth, approximately 200 km to the east, and a 1983 Mw6.7 event within 50 km of the 2013 hypocenter. Depth estimates for the Khash earthquake range from around 85 km, as computed by several different agencies from P-wave arrival times, to values of around 50 km as determined by most Centroid Moment Tensor inversion methods using teleseismic data. Focal mechanisms calculated by a wide variety of methods and data types consistently indicate normal faulting with EW to NW-SE striking nodal planes. We will present the results from a joint kinematic rupture inversion using teleseismic body and surface wave data, as well as seismic waveforms from the local Iranian broadband networks, and InSAR data. We incorporate three Radarsat-2 differential interferograms created from two right looking ascending tracks of C-band SAR data with time intervals of just over one year. Coherence is high in this arid area for all pairs. Preliminary results of our inversions indicate a compact source, with the main slip between 45 and 65 km depth. We will also present both conventional optimization and Bayesian inversions of the interferogram displacements and focus on inferences of the depth of significant slip. Teleseismic P-waves recorded by stations to the NW of the hypocenter, which are close to nodal, show a consistent misfit in the first 10 seconds after the first arrival. A similar effect is seen in the P-waves for the 2011 earthquake. The near-source presence of a dipping interface and/or low velocity layer may be able to explain this misfit. We will investigate this effect using waveform modeling.