In the current Earthquake Early Warning (EEW) systems, the site amplification factor is usually given as a scalar value empirically obtained. This study aims to study the method that estimates the frequency-dependent site amplification factors for EEW: one is site effects for B-Δ method, another is to design the casual recursive infinite impulse response (IIR) filter to model these factors and to simulate the spectra and accelerograms at target locations and also to evaluate the performance of IIR method.
First B-Δ relation is tested using 208 earthquakes recorded at IBH10 and IBRH19 of Kik-Net. The B-Δ relation obtained by curve fitting to the real data shows that the site condition does affect the relation. Second based on the idea of data assimilation, IIR filter method is tested using the same strong motion data: the surface ground motion at both sites are simulated from the corresponding borehole records using the IIR filter designed to fit the average spectral ratio of surface record to borehole’s one; and the surface motion at IBRH10 is simulated from the surface records of IBRH19 using the IIR filter designed to fit the average spectral ratio of surface record of IBRH10 to that of IBRH19.The method using IIR filter shows a good performance in simulating acceleration waveforms and spectra for most of the event that I used and highly improve the accuracy of the seismic intensity estimation.