Coseismic slip distribution of the 2015 Mw7.8 Gorkha, Nepal, earthquake from joint inversion of GPS and InSAR data for slip within a 3‐D heterogeneous Domain. Issue 5 (10th May 2016)

• Record Type: Journal Article
• Authors: Tung, Sui; Masterlark, Timothy
• Is Part Of: Journal of geophysical research. Volume 121:Issue 5(2016:May)
• Page Start: 3479
• Page End: 3503
• Publication Date: 2016-05-10
• Subjects: earthquake -- slip -- inversion -- GPS -- InSAR -- FEM; Geomagnetism -- Periodicals; Geochemistry -- Periodicals; Geophysics -- Periodicals; Earth sciences -- Periodicals; 551.1
• DOI: 10.1002/2015JB012497
• Languages: English
• ISSNs: 2169-9313

Abstract

Abstract: We derive a coseismic slip model of the 2015 Mw 7.8 Gorkha earthquake on the basis of GPS and line‐of‐sight displacements from ALOS‐2 descending interferograms, using Green's functions calculated with a 3‐D finite element model (FEM). The FEM simulates a nonuniform distribution of elastic material properties and a precise geometric configuration of the irregular topographical surface. The rupturing fault is modeled as a low‐angle and north dipping surface within the Main Frontal Thrust along the convergent margin of the Himalayas. The optimal model that inherits heterogeneous material properties provides a significantly better solution than that in a homogenous domain at the 95% confidence interval. The best fit solution for the domain having a nonuniform distribution of material properties reveals a rhombus‐shaped slip zone of three composite asperities. Slip is primarily concentrated at a depth of 15 km with both dip‐slip (maximum 6.54 m) and strike‐slip (maximum 2.0 m) components, giving rise to a geodetic‐based moment of 1.09 × 10 21 Nm in general agreement with the seismological estimate. The optimal relative weights among GPS and interferometric synthetic aperture radar (InSAR) are deduced from a new method, MC‐HVCE which combines a Monte Carlo search and a Helmert Method of Variance Components Estimation. This method determines the relative weights in a systemic approach which preserves the intrinsic solution smoothness. The joint solution is significantly better than those inverted from each individual data set. This methodology allows us to integrate multiple data sets of geodetic observations with seismic tomography, in an effort to achieve a better understanding of seismic ruptures within crustal heterogeneity. Key Points: A new method is developed to optimize the relative data weights between GPS and InSAR data Solutions in heterogeneous crustal domain provide better data fit than those in homogeneous domain The rupture demonstrates major dip slips and minor dextral slips at a depth of 15 km