REVEALING THE SUBSURFACE OF THE SOUTHWESTERN PART OF THE CAMPLONG ACTIVE FAULT, WEST TIMOR, INDONESIA BY APPLYING AUDIO-FREQUENCY MAGNETOTELLURIC DATA INVERSION

Geologically, three active faults exist in West Timor, East Nusa Tenggara (NTT) Province, Indonesia, namely the Babau, Camplong, and Atambua faults. The audio-frequency magnetotelluric (AMT) data is used to model the electrical subsurface of the Camplong Fault’s southwestern part. The AMT profile that comprised 15 AMT observation points over a length of 26 km running in an NW–SE direction was subjected to a phase tensor analysis. The results suggest that the studied area has a regional strike of N25°E and that 2-D inverse modelling on the AMT profile was possible. The inverse modelling result indicates the presence of two conductive boundaries (C1: ρ ≤ 5 Ωm and C2: ρ ≤ 5 Ωm) in the central and the southeastern parts of the AMT profile that separates the R1 (ρ = 10–50 Ωm) and R2 (ρ = 10–50 Ωm) as well as R2 and R3 (ρ = 5-100 Ωm) zones, respectively. The R1, R2, and R3 are located in the northwestern, central and southeastern parts, respectively. We suggest that the C2 is possibly the damaged zone of the fault in this study area. We also conducted forward modelling and examined the seismic activity and geological background, the results of which aligned with the inverse modelling.