Identification of Ransiki fault segment in South Manokwari Regency, West Papua Province, Indonesia based on analysis of a high-resolution of global gravity field: Implications on the Earthquake Source Parameters

Abstract

The province of West Papua in Indonesia is an area crossed by three major faults, including Sorong, Koor, and Ransiki, leading to the collision of Australia, the Pacific, and Eurasia. In the past, there have been strong and damaging earthquakes on these faults, manly Ransiki fault in the South Manokwari regency. Identification of the Ransiki fault segment was conducted by geological subsurface modeling using the earth gravity field of the Global Gravity Map (GGM) based on satellite measurements implicates for earthquake source parameters. The GGM is seen as a solution for the unavailability of direct measurements in the region. The gravity field analysis begins with data reduction using SRTM2gravity as modern terrain correction to obtain a complete Bouguer anomaly. Furthermore, the gravity gradient approach through vertical and horizontal gradients, analytical signal, and the tilt angle are applied to emphasize a contact or fault structures that are not visible using a 2D fast Fourier transform. Overall, the gravity gradient analysis obtained results that were compatible with the alignment of the Ransiki fault segment which direction of the northwest to south. The gravity inversion produces a geological subsurface model that clearly shows the Ransiki fault segment, associated with a low rock density distribution, thought to the Befoor formation and quaternary sediments, located between high-density rocks correlated to Arfak volcanic rocks as a basement.