Investigation of sediment thickness in the rammang-rammang maros karst area using microtremor method

Abstract

The aims of this study were to analyze the value of dominant frequency and amplification, estimate the thickness of the sediment, and to evaluate the seismic vulnerability of the Rammang-Rammang Maros Karst Area. This work was carried out at the Rammang-Rammang Maros Karst Area, Salenrang and Bontolempangan Village, Bontoa District, Maros Regency, South Sulawesi. Microtremor data were analyzed using the Horizontal to Vertical Spectra Ratio (HVSR) method to obtain the H/V curve representing the dominant frequency and amplification values. The dominant frequency values were obtained in the range from 1.389 to 6.251 Hz. The amplification values were in the range from 0.455 to 3.944. The sediment thickness was obtained in the range from 18.521 to 88.029 m, and the seismic vulnerability was in the range from 0.040 to 5.761. High values of sediment thickness were obtained in riverbank areas, which indicated that the weathering that occurred was caused by weathering of limestone and sedimentation by rivers. Meanwhile, low sediment thickness values were obtained in karst hill areas, indicating that the weathering occurred due to the limestone dissolution process. Based on the seismic vulnerability and amplification, the Rammang-Rammang Maros Karst Area is in a relatively safe zone.