COSEISMIC DISPLACEMENTS IN THE TIBET SIDE INDUCED BY THE 2015 GORKLA NEPAL EARTHQUAKE

We present a far-field coseismic displacement field induced by the 2015 Gorkla Nepal earthquake observed by the geodetic networks in south Tibet. The dataset for the earthquake contain static offsets collected at about 50 campaign-mode sites and ~10 continuous GPS stations, which shows the maximum horizontal displacement of ~60 cm and subsidence of ~10 cm close to the border of China and Nepal. Using GPS data, the slip distribution models respectively for the mainshock on April 25 and the largest aftershock on May 12 are inverted with green’s function calculated by a finite element method that adopts a three-dimensional, spherical and layered lithosphere including topography as well as a realistic plate geometry for the Himalaya and Tibetan Plateau. Our models show that the mainshock has a heterogenic distribution of slip on the Main Himalayan Thrust with a maximum slip of 6 meters. The slip propagates eastwards from the epicenter for 130-140 km and extends downwards about 110 km under the great Himalaya. The slip of the largest aftershock is observed to coincide with a smaller slip patch of the mainshock to the northeast of Kathmandu. The geodetic moments of the mainshock and the largest aftershock are estimated respectively to 8.8×10²⁰ Nm and 6×10¹⁹ Nm, totally corresponding to an event of Mw 7.9.