Three-Dimensional Surface Displacement Field Associated with the 25 April 2015 Gorkha, Nepal, Earthquake: Solution from Integrated InSAR and GPS Measurements with an Extended SISTEM Approach

Haipeng Luo,Ting Chen

doi:10.3390/rs8070559

Abstract

Three-dimensional surface displacement field associated with the 25 April 2015 Gorkha, Nepal earthquake is derived from an integration of Interferometric Synthetic Aperture Radar (InSAR) and Global Positioning System (GPS) measurements, with an extended SISTEM (Simultaneous and Integrated Strain Tensor Estimation From Geodetic and Satellite Deformation Measurements) approach (ESISTEM) proposed in this study. In ESISTEM approach, both surrounding InSAR and GPS measurements can be used as constraints in deriving surface displacements; while only surrounding GPS measurements are used in SISTEM approach. Besides the constraints from surrounding GPS measurements, the ESISTEM approach makes surrounding InSAR measurements available for constraining the derived deformations based on surface elastic theory for the first time. From the north to the south, derived surface displacement field shows prevailing southward horizontal deformations, and gradually varied vertical deformations ranging from −0.95 to 1.40 m within 120 km to the north of Kathmandu. This reveals that ruptures of Main Himalayan thrust (MHT) system were confined in subsurface and did not propagate to the Main Frontal Thrust (MFT) fault, in accordance with field investigation as well as geodetic and seismic studies. Relation between vertical deformations and earthquake-induced landslides is briefly discussed.

Highlights

On 25 April 2015, a devastating MW 7.9 Gorkha, Nepal, earthquake occurred in central Nepal along the trace of Main Himalayan Thrust (MHT) system and damaged the city of Kathmandu
Surface deformations caused by this earthquake were measured with geodetic techniques such as Interferometric Synthetic Aperture Radar (InSAR) and Global Positioning System (GPS) encompassing the deformation area
The modeled vertical displacement field is validated by comparing to vertical GPS measurements that are not included in the derivation (Figure 4)

Summary

Introduction

On 25 April 2015, a devastating MW 7.9 Gorkha, Nepal, earthquake (hereafter called the Gorkha earthquake) occurred in central Nepal along the trace of Main Himalayan Thrust (MHT) system and damaged the city of Kathmandu. This earthquake induced geohazards such as avalanches and landslides and caused more than 9000 fatalities [1,2,3,4]. Surface deformations caused by this earthquake were measured with geodetic techniques such as Interferometric Synthetic Aperture Radar (InSAR) and Global Positioning System (GPS) encompassing the deformation area. Vertical GPS measurements show a maximum uplift of 1.26 m at the station. As revealed by InSAR analysis [6], unlike continental earthquakes of this massive size, Remote Sens. 2016, 8, 559; doi:10.3390/rs8070559 www.mdpi.com/journal/remotesensing

Methods

Results

Discussion

Conclusion