SEISMIC MICROZONATION STUDIES IN JOGJA-BAWEN TOLL ROAD, MAGELANG REGENCY, INDONESIA

Peak Ground Acceleration (PGA) is a crucial factor in infrastructure planning, particularly in the context of constructing the Jogja-Bawen Toll Road in Magelang Regency. However, there is a lack of comprehensive research on the optimal PGA value for this region. This research addressed this gap by analyzing two significant earthquake scenarios, namely the Bantul and Yogyakarta earthquakes, with magnitudes of 6.3 Mw and 7.44 Mw, respectively. Three methods were employed for this analysis, namely the Indonesian seismic code, Kanno (2006), and Fukushima (1990) attenuations, as well as microtremor measurements. The PGA value generated by the seismic code ranges from 0.348-0.380g. For the 6.3 Mw earthquake scenario, the Kanno attenuation results in a PGA range of 0.115-0.181g, the Fukushima attenuation yielded 0.082-0.114g, and the microtremor measurements indicated 0.036-0.092g. In the case of the 7.44 Mw earthquake scenario, the Kanno attenuation generated a PGA range of 0.202-0.265g, the Fukushima attenuation produced 0.052g-0.062g, and the microtremor measurements indicated 0.036g-0.088g. The result showed that the PGA value derived from the seismic code is relatively higher because it considered various earthquake models and magnitudes. Meanwhile, the PGA value obtained from microtremor measurements was smaller due to the consideration of site class and site-specific amplification factors at the study site.