[S-SS07] Environmental Seismology: from deep earth to surface process

[SSS07-P14] Subsurface Investigation of the destructive earthquake November 21, 2022, M_w 5.6 Cianjur (Indonesia)

*Zulfakriza Zulfakriza¹, Andri Dian Nugraha¹, Rexha Verdhora Ry¹, Aditya Lesmana², Nanang T. Puspito¹ (1.Global Geophysics Research Group, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, 2.Geophysical Engineering Graduate Program, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Bandung, 40132, Indonesia)

Keywords:Seismic source, Indonesia, Cianjur Earthquake 2022

A destructive shallow earthquake with a magnitude of 5.6 struck Cianjur, West Java, Indonesia on November 21, 2022. This earthquake resulted in 602 casualties and the collapse of over 67,504 residences. The day after the mainshock, we deployed 19 temporary seismic stations to monitor aftershocks for a period of 30 days. We manually picked arrival times for 4499 P-waves and 3419 S-waves and determined locations for 514 events. Following the velocity model update, phase refinement through waveform cross correlation, and relocation using double-difference methods, we were able to determine 442 well-defined hypocenters of the aftershocks. We identified two clusters of aftershocks: one in the NNW-SSE direction, with a length of about 8 km, and another in the WSW-ENE direction, with a length of around 6 km. The seismogenic zone of these clusters ranges from a depth of 3 to 13 km. Our interpretation suggests that these clusters may indicate a conjugate fault. It is possible that the mainshock (Mw5.6) Cianjur earthquake on November 21, 2022 occurred on the WSW-ENE direction with sinistral movement. Furthermore, we also conducted seismic tomographic inversion, the result shows contrast seismic velocities anomalies around the mainshock.