Evaluation of site effects using horizontal-to-vertical spectral ratio in Kuala Pilah, Negeri Sembilan

Abstract

The destruction experienced by an area due to tremors is commonly related to the size of magnitude and the distance of the source to the site where it is well known that larger magnitude earthquakes cause greater damage. Similarly, the closest area to the source will experience much devastating damage compared to the area further away. In addition to that, the local site effect also plays a significant role in the impact of earthquake hazards for specific sites despite the site being hundreds of kilometers away from the epicenter. This had been proven by the Michoacán earthquake in 1985 where the situation is similar to Peninsular Malaysia located approximately 400 km away from one of the most active plate tectonics in the world, the Sumatra Subduction Zone. This paper aims to evaluate the local site effects to improve the result of seismic hazard assessment by applying the Horizontal-to-Vertical Spectral Ratio (HVSR) method. The recorded microtremors data are processed to get two parameters that are closely related to the local site condition which is the resonant frequency and the amplification factor. The overall values extracted from the H/V curves are intermediate for both parameters. Overall, Kuala Pilah is divided into two zones; the western region associated with a thin, well-compacted soil layer and the eastern region associated with loose and unconsolidated deposits.