Joint inversion of teleseismic, geodetic, and near-field waveform datasets for rupture process of the 2015 Gorkha, Nepal, earthquake

Abstract

The 2015 Gorkha earthquake and its aftershocks caused severe damage mostly in Nepal, while countries around the Himalayan region were warned for decades about large Himalayan earthquakes and the seismic vulnerability of these countries. However, the magnitude of the Gorkha earthquake was smaller than those of historical earthquakes in Nepal, and the most severe damage occurred in the north and northeast of Kathmandu. We explore reasons for these unexpected features by performing a joint source inversion of teleseismic, geodetic, and near-field waveform datasets to investigate the rupture process. Results indicate that the source fault was limited to the northern part of central Nepal and did not reach the Main Frontal Thrust. The zone of large slip was located in the north of Kathmandu, and the fault rupture propagated eastward with an almost constant velocity. Changes in the Coulomb failure function (ΔCFF) due to the Gorkha earthquake were computed, indicating that southern and western regions neighboring the source fault are potential source regions for future earthquakes related to the Gorkha earthquake. These two regions may correspond to the historical earthquakes of 1866 and 1344. Possible future earthquakes in the regions are predicted, and the warning for Himalayan seismic hazards remains high even after the Gorkha earthquake.

Coseismic Traveling Ionospheric Disturbances during the Mw 7.8 Gorkha, Nepal, Earthquake on 25 April 2015 From Ground and Spaceborne Observations

“…The Gorkha earthquake, which was the largest event in the region since 1934 (Bihar‐Nepal) ruptured about 150 km toward east direction of the main shock in Main Himalaya Thrust (MHT), a detachment boundary between India and Eurasian plates which extends to the surface at Himalayan Frontal Thrust (HFT) (Figure ). Joint inversion of teleseismic, geodetic, and waveform data sets suggests that the rupture front velocity of 3.3 km/s controlled the timing of the rupture propagation toward southeast direction (Kobayashi et al, ; Koketsu et al, ). The maximum coseismic slip due to thrust faulting occurred at the hypocenter was about 5.7 m at a depth of ~12 km (Sreejith et al, ).…”

From ground motion simulations to landslide occurrence prediction

“…Some of those sources are the point source model derived by both the Global Centroid Moment Tensor (GCMT) project (Ekström et al, 2012) and United States Geological Survey (USGS) (USGS, 2015). There are also four well known finite fault models derived for the same event using multiple combinations of the teleseismic and geodetic data (Hayes et al, 2015;Yagi and Okuwaki, 2015;Kobayashi et al, 2016;Wei et al, 2018). The model from Wei et al ( 2018) heavily relied on InSAR data from Sentinel-1 and ALOS PALSAR missions, together with the teleseismic data.…”

Strong ground motion data of the 2015 Gorkha Nepal earthquake sequence in the Kathmandu Valley

“…1 ). The hypocentral depth was shallow 13 , and the focal area was estimated to be 180 km long and 110 km wide on the low dip-angle fault plane 14 . The rupture propagated to the east, and a large slip area formed near the northern part of the valley 14 – 16 .…”

“…The hypocentral depth was shallow 13 , and the focal area was estimated to be 180 km long and 110 km wide on the low dip-angle fault plane 14 . The rupture propagated to the east, and a large slip area formed near the northern part of the valley 14 – 16 . This event caused approximately 1,700 deaths, and 13% of the buildings, including World Heritage sites, were damaged inside the valley 17 .…”