Geophysical investigation of the 2022 Cianjur earthquake: Uncovering a new active fault

Abstract

An earthquake disaster struck the Cianjur area on November 21 2022, with a main earthquake measuring 5.6 Mw. Until April 2023, BMKG recorded that aftershock occurred 448 times with a magnitude range of 1 – 4.2 Mw. This event occurred due to underground movement caused by a fault. The fault that has been identified in the Cianjur area is the Cimandiri fault, however, the epicentre of the earthquake and the location of the Cimandiri fault line are approximately 20 km away. BMKG indicated that there was a new fault that was the cause of the earthquake. This research aims to determine subsurface conditions with indications of active faults in the areas affected by the 2022 Cianjur earthquake. Data acquisition was carried out at Cibulakan and Firdaus Mosque using the GPR method. The GPR method used is GSSI – SIR 3000 with a 270 MHz frequency antenna. Data processing was carried out using GPRPy software. Based on the processing that has been carried out, there are indications that the fault stretches perpendicularly in a north–south direction at a depth of approximately 2 m below the ground surface. Apart from that, the rock that makes up the area is volcanic rock.