21 May 2015

Nepal earthquake causes a displacement of about 1.1 meters, according to a study by the CTTC

The results of this study, useful for seismic analysis, contribute to the study and understanding of this seismic event of exceptional magnitude

Researchers at the CTTC have estimated the ground deformation suffered in a wide area of Nepal, as a consequence of the Gorkha earthquake of 25 April 2015 and its replicas. The estimate was derived from radar observations acquired by the Sentinel-1 satellite of the European Space Agency. According to this estimate, obtained over an area of approximately 180 by 60 km, the terrain has suffered a co-seismic deformation —permanent deformation of the earth’s surface— associated with the earthquake of up to 1.1 m. This value refers to the line connecting the satellite and the observed area, which is tilted about 36º from the vertical.

The deformation can be seen in the map shown in Figure 1, where the displacements are represented in a colour scale from green (no relative motion) to red (area of maximum deformation). This study conducted by the CTTC, and led by Dr. Oriol Monserrat, head of the Remote Sensing Department, is based on a well-known satellite-based radar remote sensing technique called differential interferometric Synthetic Aperture Radar (SAR).

How were the results derived?

SAR interferometry is a remote sensing technique used to monitor surface deformations. This technique, based on the analysis of SAR satellite data, has been used in various applications such as studying the dynamics of glaciers, earthquakes, volcanoes, mining, civil works, landslides and deformations due to exploitation of aquifers.

The results of this study were obtained using SAR data from the satellite Sentinel-1 of the European Space Agency (https://earth.esa.int/documents/247904/349449/S1_SP-1322_1.pdf). Specifically, in this case, two SAR images acquired before (17/04/2015) and after the seismic event (29/04/2015) have been used.

The data processing has been performed using analysis tools developed by the CTTC. These results can be used for seismic analysis in order to estimate the geophysical parameters of the seismic event. Thus, these results represent a contribution to the study and understanding of the earthquake.

 

Figure 1: Co-seismic deformation map of the Nepal earthquake (25 April 2015) superposed over an image from Google Earth. The red star indicates the location of the earthquake epicentre
Figure 1: Co-seismic deformation map of the Nepal earthquake (25 April 2015) superposed over an image from Google Earth. The red star indicates the location of the earthquake epicentre