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Abstract:
A moderate earthquake struck the Cianjur Regency, in West Java, Indonesia, On 21 November 2022 at 13:21 local time, the hypocenter is 6.86°S 107.01°E depth of 11.0 km, with moment magnitude Mw 5.6 with an epicenter located about 100 km Southeast Jakarta, this event is possibly related to Cimandiri fault system. The mainshock also followed by a landslide in Cugenang District. This moderate earthquake causing extensive damage, great economic loss and casualties especially in the Rawa Cina, Cugenang, Warung Kondang and surrounding regions. The focal mechanism is dextral strike-slip fault, the faulting orientation of the mainshock was strike = 347°, dip = 83, the strike direction still controversy. In this research we want to find scientific proof of the true strike direction using aftershock analysis. The mainshock was followed by aftershocks productivity may due to complex faulting systems and relatively heterogeneous stress state in that region. We deployed 6 portable seismographs and analyzed aftershock distribution join with data of the permanent seismograph network (InaTEWS Network). The result shows that aftershock tend to distribute in the North-East direction. We also compute Peak Ground Acceleration (PGA) based on the event, Peak Ground Acceleration is 290 gal. It is relatively high acceleration of magnitude 5.6 may because of volcanic sediment amplify the ground shaking.
