Ground Deformation Identification related to 2018 Lombok Earthquake Series based on Sentinel-1 Data

Abstract

Abstract Lombok Island was hit by a series of earthquakes in July and August 2018 with magnitude 6 class. This series of earthquakes resulted in fatalities and material losses that even reached Sumbawa Island to the east of Lombok Island. The earthquake was triggered by Flores back arc thrust resulting in ground deformation. Ground deformation can be identified by satellite-based remote sensing method. The Sentinel-1A and Sentinel-1B satellites are two satellites carrying C-band SAR sensors with a temporal resolution of 12 days each for the same orbit, and the difference in time between the two is 6 days. Therefore, ground deformation related to seismo-tectonic or volcanic activities can be identified by interfering two SAR images (interferometric synthetic aperture radar or InSAR) at least in 6 days. By utilizing Sentinel Application Platform (SNAP) a free open source software (FOSS) and combining with other InSAR software, an interferogram that represents line of sight displacement (LOS) between ground and satellite can be generated. Line of sight displacement can then be interpreted as ground deformation signals. It is shown that the series of Lombok earthquake cause an uplift up to 70cm and subsidence up to 25cm. This deformation affects areas around epicentre. A field survey was conducted to obtain information directly and it was seen that the ground deformation that was identified with the InSAR technique were consistent with the findings in the field. This shows the advantages of remote sensing in terms of ability to cover a wide area in a short time.