Comparison of earthquake acceleration amplification values based on the CPTu and geomorphology approach in the area around the Lembang Fault, Indonesia

Abstract

The Lembang Fault is one of the sources of earthquakes in the Bandung Basin area, Indonesia. Located at coordinates -6.795075°, 107.463449° to -6.865538°, 107.737159° and has a segment length of approximately 29 km, this fault has a potential earthquake hazard that needs to be taken into account. Earthquake hazards originating from its source, namely bedrock, must be analyzed up to the surface. For this reason, a study of the amplification value needs to be carried out. To date, an easy method for analyzing amplification is using the Vs30 approach based on CPTu and geomorphology. This paper aims to obtain amplification values based on the CPTu (electric sondir) and geomorphological methods. This study obtained a 43% agreement, which was indicated by the similarity of the amplification value, which was close to 1. The geomorphology method showed a larger value (more than 1.6). This finding indicates that the equation is used as if it were in an area with a PGA value below 0.1g. Meanwhile, the average value of the two methods is considered relevant, close to 1 or the same as at the earthquake's epicenter. In the future, a more comprehensive method is needed to evaluate the geomorphology equation and the CPTu correlation to the Vs.