Line‐of‐sight displacement from ALOS‐2 interferometry: M_w 7.8 Gorkha Earthquake and M_w 7.3 aftershock

Abstract

Interferometric synthetic aperture radar (InSAR) is a key tool for the analysis of displacement and stress changes caused by large crustal earthquakes, particularly in remote areas. A challenge for traditional InSAR has been its limited spatial and temporal coverage especially for very large events, whose dimensions exceed the typical swath width of 70–100 km. This problem is addressed by the ALOS‐2 satellite, whose PALSAR‐2 instrument operates in ScanSAR mode, enabling a repeat time of 2 weeks and a swath width of 350 km. Here we present InSAR line‐of‐sight displacement data from ALOS‐2/PALSAR‐2 observations covering the Mw 7.8 Gorkha, Nepal earthquake and its Mw 7.3 aftershock that were acquired within 1 week of each event. The data are made freely available and we encourage their use in models of the fault slip and associated stress changes. The Mw 7.3 aftershock not only extended the rupture area of the main shock toward the east but also left a 20 km gap where the fault has little or no coseismic slip. We estimate this unslipped fault patch has the potential to generate a Mw 6.9 event.

Constraints on Source Parameters of the 25 April 2015, M_w = 7.8 Gorkha, Nepal Earthquake from Synthetic Aperture Radar Interferometry

“…The moment magnitude estimated from our model closely matches with that estimated from teleseismic data. The modelled slip value on the fault is comparable with the average of the distributed slip values (0-6 m) derived using inversion of InSAR and GPS data by Lindsey et al 27 , and Wang and Fialko 30 , though their model has shallower dip (7-10). However, we notice that the steeper dip angle ~15 obtained in the present study is analogous to that of Sreejith et al 31 .…”

“…We find that the length (L = 170 km), width (W = 60 km) and strike (286) of the fault plane are well constrained by the orientation and shape of the observed deformation pattern. ALOS-2 interferogram 27 has also been considered to determine L and W, as the Sentinel-1 interferogram did not cover the easternmost extent of the deformation pattern (Figures 1 and 3).…”

The 2015 Gorkha earthquake investigated from radar satellites: slip and stress modeling along the MHT

“…The ALOS-2 data were processed by Lindsey et al (2015). We processed the Radarsat-2 data using the GAMMA software (Wegmuller and Werner, 1997).…”

Monitoring the geodynamic behaviour of earthquake using Landsat 8-OLI time series data: case of Gorkha and Imphal

“…The Gorkha earthquake of Nepal was a result of thrusting along the Main Himalayan Thrust (MHT) (USGS, 2015) and the analysis of the SAR interferograms led to the interpretations that the event was a blind thrust and seismogenic fault (Angster et al, 2015;Kobayashi et al, 2015;Lindsey et al, 2015).…”