COMPARISON OF BEDROCK AND SURFACE TIME HISTORIES SUBJECTED TO SUBDUCTION EARTHQUAKES IN A SELECTED LOCATION OF YOGYAKARTA

Abstract

In practical building design, a time history is usually based on earthquake records from
somewhere else, without any precise matching processes. Consequently, the time history is rarely used in
building analysis, because of the difficulty in collecting accurate data at the building site. In this study, the
site of the Alana Yogyakarta Hotel was selected as a research object for determining the real-time history,
aimed towards an earthquake hazard analysis by using the Probabilistic Seismic Hazard Analysis (PSHA)
method. Earthquake events affecting Yogyakarta and its surrounding areas were collected from earthquake
catalogs and they were supplied from various sources, either from the government and/or from international
institutions. The data that was used in the hazard analysis was focused on the main shock only, so the
separation processes were essentially required to distinguish between the main shock, the foreshock and the
aftershock. Due to the unavailability of attenuation functions, these were then determined based upon the
earthquake data, by selecting the similarities of the tectonic and geological conditions in Indonesia, thus
producing a seismic hazard curve and a uniform hazard response spectrum. The time history data on the
bedrock was selected based on the dominant magnitude and the dominant distance of the subduction
earthquakes and matched with the uniform hazard response spectrum, so as to produce a matched response
spectrum. The results have shown that the peak times of the acceleration increased, as the results of the
matching earthquake data on the bedrock corresponded to the hazard deaggregation analysis.