A multitemporal and multisensor study of land displacement due to 5.6M earthquake in Cianjur, West Java, Indonesia

Abstract

Indonesia is located in the so-called "Ring of Fire," a region of high seismic activity surrounding the Pacific Ocean. The country is particularly vulnerable to earthquakes due to its location on the Sunda megathrust, a major boundary between the Eurasian and Indo-Australian tectonic plates. On November 21, 2022, a magnitude 5.6 earthquake struck the Indonesian island of Java, with its epicentre located in Cianjur, West Java. The earthquake caused significant damage to the region's buildings and infrastructure, and several reports of injuries and fatalities were reported. In this study, we used multisensor and multitemporal data to investigate land deformation in the study area. We used three pairs of Sentinel-1 datasets, acquired before and after the earthquake and used the InSAR algorithm to produce land displacement maps. Furthermore, we acquired aerial photogrammetry to produce very high-resolution images of the affected areas. We also classified the Planet imagery using a random forest classifier to extract the landslide events in the study area. Our results show that the earthquake caused significant land deformation in the area, with surface displacements up to 9.8 cm and 11 cm for land uplift and land subsidence, respectively. We found that the deformation was primarily concentrated in the southeastern and northwestern parts of the study area. The earthquake led to secondary disasters such as landslides and collapsed residential buildings. It’s due to the combination of geological factors and the building structures. Where the buildings structures that were not built to be earthquake-resistant stood on the old volcano products have experienced weathering. Our findings highlight the usefulness of radar dan optical remotely-sensed data in studying the effects of earthquakes and can be used to inform future disaster response and recovery efforts.