SOIL DYNAMIC RESPONSE MAPPING AND SUBSURFACE STRUCTURAL MODELING IN BANDA ACEH USING HORIZONTAL TO VERTICAL SPECTRAL RATIO (HVSR) METHOD

• Main Author: Haifa Fadhilah, Firda
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/69650
• Institution: Institut Teknologi Bandung

Banda Aceh is a city with a high level of seismicity and earthquake risk. This is mainly caused by two Sumatran Fault segments i.e. the Aceh and Seulimeum Segment. The earthquakes hazard in Banda Aceh is aggravated by the presence of soft alluvium deposits. The presence of soft alluvium layers above the harder soil layer will cause earthquake wave amplification. This amplification phenomenon can increase the amplitude and energy of earthquake waves so that the earthquake will become more destructive. Therefore, dynamic response mapping and subsurface shear wave (????????) structure modeling are required to determine the soil characteristics of the research area. Such information is needed for the infrastructure planning development of Banda Aceh City. In this current study, the subsurface model was obtained from microtremor data and a sequence of processing and modeling techniques. The analysis is carried out using the Horizontal to Vertical Spectral Ratio (HVSR) method. The resonance frequency and amplification values are identified from the ratio between the spectrum of the horizontal component and the spectrum of the vertical component depicted in the HVSR curves. Based on the obtained results, Banda Aceh has a predominant frequency values range of 0.54-11.72 Hz and an amplification range of 1.22-6.26. Low predominance frequency is mostly located in the southeast and center of the study area which is associated with large sediment thickness. Meanwhile, high amplification values are mostly located on the southeast, middle, and northwest sides of the study area which are associated with high sediment depth and geological feature in the form of swamp sediment. Then the inversion of the HVSR curve was carried out using the Neighborhood Algorithm method to find out information on the subsurface ???????? value which was then associated with the characteristics of the subsurface layer. The values of ???????? range from 50-3027 m/s for a depth range of up to 700 m, with relatively low ???????? values in the middle, southeast, south, and southwest of the study area. A low V value in the center of the study area is associated with an elongated basin with suspected horst and graben structures. An average value of shear wave velocity ???????? up to a depth of 30 indicates that Banda Aceh City is classified as a seismic site class D (SD).