PROPOSED GROUND MOTION FOR FOUR CAPITAL CITIES IN SUMATERA REGION BASED ON SEISMIC HAZARD ANALYSIS RESULT USING 3-D FAULT SOURCE MODEL

• Main Author: PANDHU MAHESWORO (NIM 25005025), RAKHINDRO
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/9008
• Institution: Institut Teknologi Bandung

Vibration of the ground due to seismic waves propagation can be clearly described by amounts of ground motion data in terms of acceleration time histories which is recorded at the station. Therefore, by interpretation of these ground motion data, evaluation of the effect of earthquake within a region can be conducted in objective and quantitative ways. Unfortunately, available recorded data for Indonesia and Sumatera region are mainly about the location of epicenter, magnitude, focal depth, and earthquake mechanism. Based on the condition, the study presents a method of developing proposed ground motion for four capital cities in Sumatera region which are seismically active i.e. Banda Aceh, Padang, Bengkulu, and Bandar Lampung. The study is discussed in the form of research methodology, and started with identification and collection of historical earthquake data within a radius of 500 km that significantly contributed to seismicity condition in site location of interest. By considering the seismotectonic and regional geologic aspects, the collected data are then used as a consideration in the making of earthquake source models. Distinction has been made to earthquake model as subduction model and shallow crustal model. Thus, subduction model itself are separated between megathrust zone, a zone with focal depth equal or less than 60 km, and benioff zone, a zone with focal depth more than 60 km. Several method which used in statistical operation of the data are magnitude scale conversion, analysis of dependency, and analysis of completeness. Seismic parameters illustrate characteristic and earthquake activity in every source of earthquake zone and needed as input in PSHA. This parameter covers recurrence rate and b-value, maximum magnitude, slip rate and attenuation function. Furthermore, analysis of seismic hazard for 500 years of return period is performed based on probabilistic concept using 3-dimensional source model which is derived from these earthquake models and seismic parameters. This analysis gives accurate results of peak ground acceleration and response spectra at bedrock. Response spectra at bed-rock afterwards put into scale for spectral period of 0.2 sec and 1.0 sec to obtain the target spectra. Analysis of spectral matching from characteristic earthquake response spectra to target spectra results the scaled spectra and the scaled acceleration time histories at bed-rock which is proposed as ground motion design in this study. PHSA and spectral matching analysis in this study is performed by using computer program EZ-FRISKTM Version 7.20 from Risk Engineering Inc.