Archive | 2021
Delineation of Sedimentary Basin Structure beneath the Banyumas Basin, Central Java, Indonesia, Using Ambient Seismic Noise Tomography
Abstract
\n Subsurface images of an area with a thick volcanic layer generally can not be well-imaged with conventional seismic exploration (seismic reflection) due to seismic wave scattering. Another method is needed to obtain an accurate subsurface image in a thick volcanic layer area. In this study, we applied Ambient Noise Tomography (ANT) to image the shear-wave velocity (Vs) structure in the Banyumas Basin, Central Java, Indonesia, which has relatively thick volcanic layers. We aimed to delineate the sediment deposits and the sedimentary thickness in this area. Although this method has limited application for subsurface imaging with a thick volcanic layer area, the application of cross-correlations from ambient noise has been widely applied in numerous locations to obtain greater understanding of subsurface structures. In this study, more than 1,000 pairs of vertical component cross-correlations were used to estimate the Green s Function of the Rayleigh wave. The Multiple Filter Technique (MFT) was used as a Time-Frequency Analysis and 1,291 dispersion curves were obtained. The Neighbourhood Algorithm (NA) was utilized to inverse the dispersion curves at 121 grid points which were used to obtain a vertical depth profile of 1D Vs. The Vs map results show that the low Vs tend to trend in a northwest-southeast direction associated with two areas: the Majenang low, and the Citanduy low. The presence of low Vs values corresponds with Middle Miocene–Pliocene sedimentary rocks. Meanwhile, the high Vs value in this area might correspond with Oligocene–Early Miocene volcanic products and Eocene sediment. Our study was also able to reveal the thickness of sedimentary rocks in the the Banyumas sedimentary basin, which is believed to have hydrocarbon potential.