SOIL DYNAMIC RESPONSE MAPPING AND UNDERGROUND STRUCTURAL MODELING IN KERTAJATI REGION USING HORIZONTAL-TO-VERTICAL SPECTRAL RATIO (HVSR) METHOD

• Main Author: Haifa Fadhilah, Firda
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/69627
• Institution: Institut Teknologi Bandung

The Kertajati area is an area dominated by geological features in the form of soft rocks, namely Lower Quaternary sedimentary rocks (Qos) which have weathered in most of the research area and the appearance of Alluvium Deposits (Qa) on the southeast side. The condition of soft rock that is on top of the harder rock will result in amplification during an earthquake. Because in the southwest of the study area there is the Baribis Fault that subducts from Purwakarta and Majalengka. This fault is also estimated to have caused the largest earthquake ever recorded on the island of Java which occurred in the 17th century. In this study, microtremor data processing with the Horizontal to Vertical Spectral Ratio (HVSR) method is expected to be a disaster mitigation effort in the Kertajati area considering that the area has also been built West Java International Airport (BIJB). HVSR is a seismic method that can be used to identify dynamic characteristics of the soil in the form of dominant frequency and amplification, and can produce an image of the subsurface seismic structure. From the results of data processing that has been carried out, the dominant frequency values vary in the range of 0.6-18 Hz while the amplification values have a range of 1.26-6.3. The dominant low-value frequencies are on the southeast, southwest, and central part of the study area, indicating a relatively larger thickness of the sediment layer. While the high value amplification values are dominant on the north, southwest, and central parts of the study area. Then the inversion of the HVSR curve was carried out using the Neighborhood Algorithm method to find out the information on the subsurface ???????? value which was then associated with the characteristics of the subsurface layer. The values of ???????? ranged from 53-3027 m/s for a depth range of up to 610 m, with relatively lower values on the south, northwest, and central parts of the study area. Soil types were also grouped with an average value of ???????? wave velocity to a depth of 30 m which indicated the soil types in the Kertajati area were medium soil (SD) and solid soil or soft rock (SC).