Geoinformatics-based assessment of land deformation and damage zonation for Gorkha earthquake, 2015, using SAR interferometry and ANN approach

Tannu Priya,Arvind Chandra Pandey

doi:10.1007/s42452-021-04574-9

Abstract

The Gorkha earthquake 2015 was one of the largest disastrous events that occurred in the main Himalayan thrust (MHT) region with epicenter at Gorkha region and magnitude of 7.8 which caused severe causality to life as well as property. The spatial statistics on vertical displacement and extent of damage zone is still too scarce to provide strong evidences of its hazard potential. In the present study, quantitative assessment on surface deformation has been carried out to compare land displacement of two different regions of Nepal (the Central Nepal and the Eastern Nepal), which are located at different distances from the epicenter, using InSAR technique on post- and pre-earthquake images from Sentinel 1A SLC product. The Central Nepal experiences an upliftment of 1.1 m and land subsidence of − 0.61 m, whereas for the Eastern Nepal the estimated upliftment and subsidence were 1.0 m and − 0.33 m, respectively. Further a regional earthquake-prone zone map was generated using the historical earthquake epicenter data and geographic information system (GIS) to understand the major vulnerability zones in the area. A total of 564 earthquake events were reported by USGS in Nepal region during 2000–2019, of which 476 (84.39%) were of magnitude greater than 4 on Richter scale and 376 events (66%) occurred at depth greater than 15 km. The damage assessment was done using machine learning (artificial neural network) back-propagation model in which the satellite imagery retrieved from the optical satellite Landsat 8 OLI sensor and digital elevation model was used to map slope, aspect, relief, drainage and lineament to be used as input layers to generate damage proxy map. The result obtained from ANN illustrated that despite being located comparatively at more distance from epicenter, the Eastern Nepal exhibited more damage-prone area (587 sq. km) in comparison with Central Nepal with 457sq. km damage prone in similar zone. Central Nepal evidences more damage-prone areas over compact build-up in contrast to Eastern Nepal, making greater risk potential in urban areas of Central Nepal during earthquake activity.

Highlights

Earthquake is defined as a tectonic or volcanic phenomenon that represents the movement of rock and generates shaking or trembling of the Earth’s surface [4]
In this study for the preparation of regional earthquake prone zone map, earthquake epicenter data obtained from NASA website has been used for the period from 2000 to 2019 and the map was prepared in ARCGIS 10.3 environment
For co-registering the images of Central Nepal, the image acquired on 17th April 2015 was used as master image, whereas 23rd May 2015 has been considered as slave image

Summary

Introduction

Earthquake is defined as a tectonic or volcanic phenomenon that represents the movement of rock and generates shaking or trembling of the Earth’s surface [4]. It is considered as one of the most severe natural hazards which can neither be predicted nor controlled. Earthquakes occur on faults, representing a clear link between seismology and structural geology [8]. The major earthquakes occur mainly in belts coinciding with the margins of tectonic plates. An inter-plate earthquake is caused mainly due to three types of faults, namely Normal Fault, Reverse (Thrust) Fault and Strike slip Fault. An earthquake’s point of initial fissure is called its focus or hypocenter, whereas the point at the ground level beeline above the hypocenter is called the epicenter of the earthquake which generally experiences the more damage

Objectives

Methods

Findings

Discussion

Conclusion