Subduction earthquake effect on lateral ground movement for offshore structure in Malaysia water

Abstract

Peninsular Malaysia is located in a low seismic region. Although Malaysia is not located in an active fault seismic area, it is in the vicinity of the Sumatran and Philippines active seismic zones. Tall buildings frequently felt the tremor generated from Sumatran subduction and fault zones especially in states that are near the coastal area of Peninsular Malaysia such as Johor, Penang and Terengganu. In general, offshore engineering is known to be one of the most high-risk and ultimately extreme engineering field where extra attention and precaution are needed when analyzing, designing, monitoring or maintaining a structure in order to ensure the integrity of the many structures and components that are involved in this field. Fixed offshore structures in Malaysian waters are not designed to resist earthquake ground motion. However, Malaysia actually experienced the tremors due to the earthquakes which happened in neighboring countries. Furthermore, any offshore structure design should consider several factors such as wind, wave and seismic loads which affect the stability and the integrity of the offshore structure. This research was carried out to achieve the main objective which is to develop new attenuation equation. The development of new attenuation equation is to determine the ground motion parameter which is Peak Ground Acceleration (PGA). The new attenuation equation is In Y = 3.25 – 2.27M + 2.28M1.13– 2.22ln(R + 360.46 exp (0.05M)) – 0.005H. An earthquake source parameter such as magnitude of earthquake, source to site distance and focal depth of site characteristics function must be considered to determine the value of PGA by using the new attenuation equation. The range of the PGA values for this study is from 0.00006g to 0.0003g. The value of PGA can be used to analyse all the types of structure in mainland and offshore. Non-Linear Earthquake Response Analysis (NERA) program was used to determine the time history on the specific location of the offshore structure and Finite Element Method (FEM) analysis was used to determine deflection of piles effected by the ground movement. The findings in this research suggest that seismic loading effects should be considered in the design of offshore structure due to displacement of pile arising from ground movement.