Development of spectral hazard maps for a proposed revision of the Indonesian Seismic Building Code

Abstract

The need to revise the current Indonesian Seismic Hazard Map contained in Indonesian Earthquake Resistant Building Code SNI 03-1726-2002 which partially adopts the concept of UBC 1997, was driven among others by the desire to better reflect the potential larger earthquake disasters faced by the nation in the future. The much larger than maximum predicted Aceh Earthquake (M _w 9.0–9.3) of 2004, followed by the destruction observed during the 2005 Nias Earthquake (M _w 8.7) urgently underline to need to consider the new conceptual approach and technological shift shown in the transition of UBC 1997 to IBC 2006. This paper presents research works for developing spectral hazard maps for Indonesia. Some improvements in seismic hazard analysis were implemented using recent seismic records. Seismic sources were modeled by background, fault, and subduction zones by considering a truncated exponential model, pure characteristic model or both models. A logic tree method was performed to account for the epistemic uncertainty and several attenuation functions were selected. Maps of PGA and spectral accelerations for a short period (0.2 s) and for a 1-s period were then developed using a probabilistic approach. The maps will be proposed as a revision for the current seismic hazard map in the Indonesian Seismic Building Code.

Keywords:

• seismic hazard analysis
• attenuation functions
• spectral hazard map
• total probability theorem

Acknowledgments

The authors gratefully acknowledge Mark Petersen and Stephen Harmsen, both from the USGS, who have provided us with the USGS Software for Probabilistic Seismic Hazard Analysis and technical discussions. Thanks also to our colleagues for their contributions: Drajat Hoedajanto (Indonesian Society of Civil and Structural Engineers), Bigman M. Hutapea (Indonesian Society for Geotechnical Engineering), Engkon K. Kertapati (Geology Research and Development Centre Indonesia), Teddy Boen (World Seismic Safety Initiative – WSSI, Indonesia).