DEVELOPMENT OF PROBABILISTIC, DETERMINISTIC AND MAXIMUM CONSIDERED EARTHQUAKE MAPS FOR DESIGN OF EARTHQUAKE RESISTANCE INFRASTRUCTURES IN INDONESIA

摘要

Indonesia has been well known as one of the most seismically active countries in the world. It is surrounded by three major active tectonic plates of the earth: Eurasian, Indo-Australian, and Philippine plates. The most effective way to reduce disasters caused by earthquakes is to estimate the seismic hazard and to implement this information on a seismic code for use in infrastructure design and construction so that the infrastructures possess adequate earthquake resistant capacity. Several great earthquake occurrences in Indonesia in the last six years inquire revision of seismic hazard parameters. The need to revise current Indonesian Seismic Hazard Map expressed as PGA contained in our latest Indonesian Earthquake Resistant Building Code SNI 03-1726-2002 was driven among others by the desire to better reflect potential larger earthquake disasters faced by the nation predictably in the future. Two major expected revisions are the earthquake hazard map, to reflect the latest advancement in Seismic Hazard Analysis technology accounting for potential larger disasters predicted in the near future, and changing the provision from UBC-97 concept to the latest IBC-2009 and ASCE 7-2010 provisions. The Department of Public Works then established Team for Revision of Seismic Hazard Maps of Indonesia 2010. This team has worked to develope probabilistic, deterministic, Maximum Considered Earthquake (MCE), and Risk-targeted Maximu Considered Earthquake (MCER) maps of Indonesia. The maps were developed based on probabilistic and deterministic approaches by using three-dimensional seismic source models and by considering latest geological and seismological data and fragility curves of buildings. The works were performed using this following procedure: 1) conducting literature review on geology, geophysics and seismology to identify activity of seismic sources in and around Indonesian region, 2) collecting and processing recorded earthquake data for entire Indonesian region, 3) modeling seismic source zones based on the advance models appropriate with USGS software, 4) determining seismic parameters which include a-b values, maximum magnitudes, and slip-rates, 5) calculating spectral acceleration based on probabilistic and deterministic theorems, 6) mapping MCE and MCER. Seismic parameters used in this study were derived from published journals, proceedings, previous researches conducted by team members, and latest information obtained during this study. This study has then compiled and integrated previous and current studies. Earthquake source parameters were determined based on earthquake catalog, geological, and seismological information of active faults. The earthquake catalog covered earthquake period between 1900 to 2009, relocated catalog by the year 2005, and area between 90°E to 145°E longitudes and 15°S to 15°N latitudes. Seismic sources were devided into subduction, fault, and background zones by considering recurrence relationship that includes truncated exponential model, pure characteristic model, and both models. Geometry of fault and subduction were represented by three-dimensional (3D) models based on the result of tomography and slip-rates of faults were determined by considering the results of GPS measurement. Background source zones were modeled using gridded seismicity based on spatially smoothed earthquake rates. The earthquake catalog was used for developing gridded seismicity starting from 1900 to 2009 and the updated Engdahl catalog up to 2009 was used for control geometry of subduction.