Seismic Behaviors Estimation of the Shallow and Deep Soil Layers Using Microtremor Recording and EGF Technique in Yogyakarta City, Central Java Island

The technique using microtremor measurements are cost-effective tools that rapidly acquire high resolution sedimentary layer information over a large area about site response, sedimentary thickness, and average S-wave velocity structures from the secondary drilling stations. In 2012, the 274 stations of single microtremor recording were conducted to the main path of NS and EW of the research area. Microtremors were recorded with 3-components by using a model of Mitutoyo-GPL-6A3P and processed by the horizontal-to-vertical (H/V) spectral ratio technique which was used by BIDO software. The results show that the seismic behaviors in Yogyakarta City vary significantly: both of Ts and Td spans 0.10-1.00 sec and 0.15-4.00 sec, and the thickness of sedimentary layers ranges from a few meters to over 200 meters. Moreover, to predict the strong ground motion it was used the Empirical Green's Function technique (EGF) formulated by Irikura1,2, based on scaling law of fault parameters for large and small events and the ω2 source spectra. The NS, EW and UD components of synthetic acceleration wave form or Peak Ground Acceleration (PGA) are calculated 392.30, 484.20 and 236.40 cm/s2 by the EGF method respectively and the Fourier Spectrum is represented the three components by the target event and subevents for the studied area. Finally, this paper evaluates the applicability of the different techniques for seismic behaviors estimation from the H/V spectral ratio of microtremor recordings and EGF method based on the Opak River Fault.