Interseismic Deformation of the Lombok Island Indonesia and Its Tectonic Implication from InSAR and GNSS Data

Abstract

Lombok Island Indonesia part of the Lesser Sunda Islands has high seismic activity because it is surrounded by active faults: the Flores backarc thrust in the north Lombok and Sumbawa strike-slip fault in the west and east of island and the Java trench in the south In 2018 an earthquake sequence with a magnitude larger than 6 4 occurred on 28 July 5 August and 19 August 2018 respectively However Mw > 6 earthquakes still rarely occur during a century based on the U S Geological Survey earthquake catalog from 1979 To understand the characteristics of the tectonic setting of the Lombok Island and its behavior I integrated the Interferometric Synthetic Aperture Radar (InSAR) data from Sentinel 1A/B ascending and descending direction and GPS data to construct the high-resolution 3D velocity field The published 12 GPS campaign-mode velocities from 2013 to 2016 were utilized First I used all possible SAR images to generate interferograms using InSAR Scientific Computing Environment (ISCE) software Then I constructed the Line of Sight (LOS) displacement time series from October 2014 to July 2018 using Generic InSAR analysis toolbox (GIAnT) software with adopting a small baseline subset (SBAS) method The LOS velocities were estimated using the least-squares method for each coherent pixel The mean velocity from the ascending direction is 12 mm/yr while descending is 0 5 mm/yr The general pattern of LOS velocities doesn’t show the clearly fault-related deformation Therefore LOS velocity decomposition to E and U component is needed to understand the characteristic of surface deformation Before the velocity inversion calculation the long-wavelength noise has to be removed The estimated velocities from inversion show a shortening pattern for the whole island It is because the velocity in the west area is higher than the east part These results also propose that the general deformation of Lombok Island is mainly under compression and right-lateral shearing

Date of Award	2020
Original language	English
Supervisor	Kuo-En Ching (Supervisor)