SUBSURFACE IMAGING USING SEISMIC REFRACTION TOMOGRAPHY WITH WAVEPATH EIKONAL TRAVELTIME INVERSION TO DETERMINE CONSTRUCTION POSITION OF TUNNEL “AAMO”

• Main Author: ARGE PRATAMA OTOLOMO , MUNAWIR
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/29399
• Institution: Institut Teknologi Bandung

Seismic refraction tomography is a geophysical method that can be used in subsurface imaging to determine geological conditions such as the depth of the bedrock and thickness of weathering layer. One of the infrastructures that need this method is the Jakarta-Bandung high speed railway line that passes through mountain area of West Java. Acquisition of seismic refraction data was conducted in Tunnel “AAMO” and traveltime time data of seismic waves propagated from source to receiver is obtained. Observation traveltimes data derived by picking first break. The initial velocity model was determined using the DeltatV inversion and the smooth inversion method. After that, the Wavepath Eikonal Traveltime (WET) inversion process is performed using both models of initial velocity to obtain the image of subsurface conditions. The results showed three different layers which consist of a weathering layer with Vp less than 1000 m/s, an intermediate layer with Vp between 1000-2300 m/s, and a bedrock layer with Vp value more than 2300 m/s. The weathering layer has a thickness of 30-40 meter. Bedrock layer can be found starting from 50 meter depth. The results also showed a normal fault structure at distance of 850 meter to 1000 meter from the starting line. The position of tunnel is at depth of up to 50 meters from surface, which is located in the intermediate layer and close to the bedrock layer.