Coseismic Slip Distribution of the 24 March 2011 Tarlay (Myanmar) Mw 6.8 Earthquake from ALOS PALSAR Interferometry

Abstract

Abstract We investigate coseismic deformation of the 24 March 2011 M w 6.8 Tarlay, Myanmar, earthquake using ALOS PALSAR data from both descending and ascending passes. Using high‐quality synthetic aperture radar interferograms and amplitude‐offset images, the nearly linear surface rupture is well traced along the western end of the Nam Ma fault and strikes ∼69°. From both descending and ascending pass Interferometric Synthetic Aperture Radar data and a rigorous maximum a posteriori probabilistic inversion method, we infer that the event involved mostly a pure left‐lateral strike‐slip rupture with near‐vertical geometry. Our one‐segment model shows that the maximum slip of ∼4.1 m occurred at ∼4 km depth, much larger than the slip at the surface. Both interferograms also reveal a small segment to the east of the main rupture, in a densely populated farming area. Our inversion of a two‐segment model shows a similar slip distribution on the main fault, in addition to ∼0.1–0.3 m left‐lateral slip with normal component on a 58° north‐dipping segment. The total seismic moment from the two‐segment model is 1.95×10 19 N·m, equivalent to an M w 6.79 earthquake, which is comparable to the U.S. Geological Survey seismic inversion estimate of 2.10×10 19 N·m ( M w 6.84). The earthquake occurred within a group of east‐northeast‐striking left‐lateral strike‐slip faults near the Myanmar–Laos border, which are seismically active and reflect a system of actively clockwise rotating blocks. Online Material: Figures of InSAR observations, amplitude‐offset maps, InSAR deformation decomposition, one segment model inversion residuals, single data set inversion results, and tectonic setting.