SPATIAL AUTOCORRELATION METHOD FOR SUBSURFACE IMAGING IN BANDUNG BASIN

• Main Author: Sabiq Tafwidlul Maula, Muhammad
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/53357
• Institution: Institut Teknologi Bandung

The subsurface structure of the Bandung Basin can be determined by using Spatial Autocorrelation (SPAC) or spatial autocorrelation methods. The purpose of this study was to determine the characteristics of the soil or rock layers below the surface of the Bandung Basin. With the mechanical wave propagation that occurs, there is one type of wave that can be used to determine the structure of the subsurface layer of the earth, the Rayleigh wave. The spatial autocorrelation method is a microtremor survey method that can provide information on subsurface structures with Rayleigh wave characteristics obtained from microtremor data recording. In this study, data recorded in the Bandung Basin from January to February 2021 using geophone 1Hz. Each measurement is done by forming 3 arrays with 3 different radius, there are of 100, 1000, and 5000 meters radius for each array. The results of the research were processed using Matlab and Geopsy software. The inversion resulted in a shallow three-layer stratified model of shear wave velocity for each array. The shear velocity values of the first array are 150, 250 and 460 m/s for the first three layers from the surface down to 100 m deep. The shear velocity values of the second array are 250, 600 and 1500 m/s for the first three layers from the surface down to 2000 m deep. The shear velocity values of the third array are 300, 650 and 1800 m/s for the first three layers from the surface down to 3000 m deep. Based on the NEHRP classification, the shear wave value is equal to 366 until 762 m/s indicating that the soil profile beneath the measurement site is categorized as very dense soil or soft rock, rock in between 763 and 1524 m/s, and hard rock equal to 1524 m/s or higher than that. The model from the SPAC research consistent with the results of research conducted by other researchers by utilizing different geophysical methods.