METROPOLITAN MANILA SEISMIC HAZARD MAP USING MIDORIKAWA & HORI SITE AMPLIFICATION MODEL

Abstract

Since Metropolitan Manila is known to be susceptible to seismic hazards, it is necessary to consider multiple factors in assessing this hazard. Aside from ground motion, the properties of soil which lead to the amplification of seismic waves should be considered. This study aimed to develop a seismic hazard map for Metro Manila considering the soil properties in the area by using Midorikawa & Hori site amplification model. Probabilistic seismic hazard assessment was conducted using earthquake data within 250 km of Metropolitan Manila for 10% and 2% probabilities of exceedance. The site amplification factors were computed using calculated shear wave velocities from SPT-N values. The calculated ground motions were amplified using the site amplification factors considering short-period and mid-period amplifications. The constructed maps of amplified peak ground acceleration (PGA) values showed how soil properties affect the ground motion. It was found that for a short-period amplification, the average PGAs is 0.538 g, and 0.659 g for 10%, and 2% probabilities of exceedance, respectively. While for mid-period amplification, the average PGAs is 0.589 g, and 0.830 g for 10%, and 2% probabilities of exceedance. Using the amplified seismic hazard maps, a better approximation of seismic hazards can be generated for future use.