THE MARCH 28, 2025 EARTHQUAKE IN MYANMAR: A RUPTURE SURFACE MODEL FROM SATELLITE DATA ON EARTH SURFACE DISPLACEMENTS

The paper presents a model of the rupture surface of the Mw 7.7 earthquake that occurred in Myanmar on March 28, 2025. The model is based on the solution of the problem of stresses and strain state of a spherical radially stratified planet due to displacement on a rectangular section located within it (F. Pollitz, USGS) and displacement data obtained during the earthquake and within six following days, derived from Sentinel-1A satellite imagery (March 22, 2025, and April 3, 2025) using the offset tracking method. A regularization condition was applied, favoring slip directions close to pure right-lateral strike-slip. The results show that the main displacements on the fault occurred within the upper 5 km of the Earth's crust and ranged from 5.0 to 6.7 meters, while at greater depths the displacements were significantly smaller. An exception was a small segment of the fault located between 21.28° and 21.56°N, where the displacement at the upper level was estimated at 4.5 meters. Possible causes for the slight displacement deficit are explained in the study by the peculiarities of the aftershock process development. The constructed rupture surface model does not show significant variations in slip magnitude along the fault or the presence of local thrust or normal faulting components. GPS data collected since the early 2000s also indicate uniform elastic strain accumulation along the fault at an average rate of 20 mm/year, suggesting that the fault was locked over its entire length.

The obtained results refine the rapid-response model presented on the US Geological Survey website by accounting for the Earth's sphericity and radial layering, as well as by applying the regularization condition for slip direction alignment with right-lateral strike-slip motion.