2011 : Assessment to the soil-structure resonance using microtremor analysis on pare-east Java, Indonesia

Prof.Dr.Ir. Triwulan DEA


Abstract

The determination of seismic hazard, oriented to seismic risk management in urban areas, particularly on Pare–East java, force us to know the resonance range between the dynamic behavior of ground and the one of building structures. Since no major damaging earthquake has occurred in site in recent times, the presence of soil–structure interaction effects from observed damage pattern are not available. In order to assess the soilstructure resonance for this site study, the microtremor measurements was applied. Microtremor measurements were performed 6 free-field and inside 6 buildings of various heights. We focused on important public buildings (ie schools and mosque). The Horizontal-to-Vertical Spectral ratio (HVSR) analysis was applied in order to access the fundamental frequencies of the sediments, beside the longitudinal (EW) and transverse (NS) fundamental frequencies of each building determined from amplitude spectra and the Floor Spectral Ratio (FSR). When one of these frequencies is close to a nearby freefield fundamental frequency, a potential soil-structure resonance is present. Among 6 buildings with established frequencies we found two buildings with low, one with medium to high and three building with high danger of soil-structure resonance. This study shows that the microtremor method could be used to make preliminary assessment of soil-structure resonance.