SEISMIC HAZARD ASSESSMENT:In the Case Study of Minesite Area-Central Kalimantan

Convention Bandung 2004 (CB2004) The 33^rd Annual Convention & Exhibition 2004

Indonesian Association of Geologist Horizon Hotel, 29-30 Nov, 1 Dec 2004, Bandung

SEISMIC HAZARD ASSESSMENT:In the Case Study of Minesite Area-Central Kalimantan

Engkon K.Kertapati

Geological Research and Development Centre

Abstract

The low-seismicity Central Kalimantan has never experienced any earthquake damage. Thus, earthquake-resistant design has not been specifically required in the building codes. However, it has been realized that urban and mine areas located rather distantly from earthquake sources may also be affected by tremors. The key is basically determined by how well seismic hazards derived from seismic potency can be estimated. In this paper, the potential ground motion in terms of the peak ground accelerations ( PGAs) due to long – distance East Kalimantan and West Sulawesi earthquakes ( far field earthquake ) is investigate, following a probabilistic seismic hazard assessment approach. Earthquakes that have occurred in radius of 500 km ( far field ) in the last 50 year are used. Based on the PGAs of more than 50 % East Kalimantan and West Sulawesi earthquakes recorded in Central Kalimantan, the attenuation relationship of Fukushima and Tanaka ( 1992 ) is found to correlate well with the high-rate attenuation characteristic of the region. The predicted design basis PGA for Tailings Dam , i.e. PGA with 10 % probability of being exceeded in a 50-year exposure time, on rock out-crops site is 0.041 g ( g = gravity value ), or 0.103 g on soft soil. And 0.105 g with 10 % probability of being exceeded in a 1000 year exposure time on rock out-crops or 0.261 g for soft soil. However, the increasing number of felt tremors in recent years demonstrates such as: Muarateweh Earthquake, which occurred on July 05, 1996, that although no significant damage was report, the earthquake was strongly felt.

Keywords: ground acceleration, ground-motion, attenuation function, earthquake- resistant design