Magnetotelluric resistivity imaging of the Baribis fault zone’s Majalengka segment in West Java, Indonesia

Abstract

This work discusses the application of the magnetotelluric (MT) method to observing and delineating a local fault in the Majalengka Regency, West Java, Indonesia. This fault is part of the well-known Baribis fault segment. Phase tensor and induction vector analysis were applied to all MT data to reveal the dimensionality, geoelectric strike, and geological conditions of the study area, with 12 MT sites composing the studied profile. The estimated skew angle (β) value is − 3º < β < 3º enabling the subsurface structure modeling using the 2-D inversion. The calculated geoelectric strike of the study area of N15^oE was used to rotate the impedance tensor of all MT observation points before modeling. The induction vector analysis revealed that the vectors did not lie in a particular direction. It can be possibly related to the volcanic products which dominate the surroundings of the study area. The 2-D subsurface electrical resistivity model suggested the presence of a very conductive zone (C1 ≤ 10 Ωm), which may be related to the existence of the targeted fault. The subsurface model also showed the resistivity contrasts between C1 (≤ 10 Ωm) and R1 (ρ ≥ 500 Ωm) as well as C1 (≤ 10 Ωm) and R2 (ρ = 50–100 Ωm). These notable contrasts are represented by the models’ block boundaries, and it is suggested that these may become a future earthquake epicenter.