ANALISIS PERBANDINGAN NILAI Vs30 BERDASARKAN DATA MULTICHANNEL ANALYSIS OF SURFACE WAVE DAN MIKROTREMOR DAERAH GUNUNGKIDUL DAN BANTUL, DAERAH ISTIMEWA YOGYAKARTA
Shellya Dewi Agustin, Dr. Eddy Hartantyo, S.Si., M.Si.
2023 | Skripsi | GEOFISIKA
Bantul and Gunungkidul Regencies Yogyakarta are prone to earthquakes due to plate tectonic activity and active faults. The 2006 earthquake in Yogyakarta was due to the movement of the Opak fault, causing damage to buildings and casualties. Mitigation strategies are performed by identifying local site conditions based on the average shear wave velocity to a depth of 30 m (Vs30) in response to the impact of the earthquakes. Thus, Vs30 values are acquired with MASW and microtremor data measurement that have differences in determining the value. This study aims to analyze the comparison of Vs30 values generated from both data using 25 measurement points to see the response of the data in the characterization of local conditions.
Vs30 values from the MASW data were obtained by inverting the dispersion curve at each measurement point. Meanwhile, Vs30 values from microtremor data were obtained by inverting the HVSR curve. The comparison graph was made with an Excel chart in the form of a scatter plot. This comparative analysis obtained a good correlation between the two data with a coefficient of determination (R2) worth 0.7316. Both data have a range of Vs30 values between 152 – 1167.6 m/s, categorized in the type of soft soil (SE) to rock (SB). Comparisons were also made on both data with Vs30 USGS. The comparison results in Gunungkidul show Vs30 value of either MASW and microtremor data have higher range values compared to the Vs30 USGS. While in Bantul, the Vs30 value of both data tends to be lower. Vs30 USGS model has high compatibility with Vs30 MASW and microtremor in plain areas. While in gentle slope hill areas such as Gunungkidul, Vs30 USGS is less able to explain the value Vs30 suitable for conditions in the field.
Kata Kunci : MASW, mikrotremor, inversi HVSR, Vs30