Abstract. The site amplification factor was usually considered as scalar values, such as amplification of peak ground acceleration or peak ground velocity, increments of seismic intensity in the conventional earthquake early warning system. This paper focus on evaluation of infinite impulse recursive filter method that could produce frequency-dependent site amplification and compare the performance of the scalar value method with the infinite impulse recursive filter method. Firstly, the strong motion data of IBRH10 and IBRH19 of Kiban Kyoshin network (Kik-net）from 2004 to 2012 were processed and selected carefully. The relative spectral ratio of IBRH10 surface acceleration to IBRH10 borehole acceleration, the relative spectral ratio of IBRH19 surface acceleration to IBRH19 borehole acceleration, the relative spectral ratio the IBRH10 surface and borehole acceleration to the IBRH19 surface and borehole acceleration were calculated using the traditional spectral ratio method. Secondly, the relative spectral ratio were modelled using the infinite impulse recursive filter method. The simulated IBRH19 surface acceleration and Fourier spectrum were obtained by filtering the IBRH19 borehole data. The seismic intensity residual were calculated for both the observation and simulation data, it shows that 98.6 % of these seismic intensity residuals are less than 0.5, 100 % of these seismic intensity residuals are less than 1. Similarly, the simulated IBRH10 Surface acceleration and Fourier spectrum were obtained by filtering the IBRH19 surface acceleration time series. The seismic intensity residual were calculated for both the observation data and the simulation data. The statistical data shows that 69.7 % of these seismic intensity residuals are less than 0.5, 98.1 % of these seismic intensity residuals are less than 1. Through these comparisons, we can find that these simulations show better performance than the ARV method and station correction method. It also shows good performance than the average level and the highest level of all the 11 years Japan Meteorological Agency (JMA) earthquake early warning system. Thirdly, compare different simulation cases, it can be easily found that this method could produce different amplification factor for different earthquakes. It could produce the frequency-depend site amplification factor. It highly improve the situation that the scalar value site amplification methods which could not produce different amplification factor for different earthquakes. This method pays attention to the amplitude and ignore the phase characteristic, this problem may be improved by the seismic interferometry method. This paper makes deep evaluation of the infinite impulse recursive filter method. Although there are some problems needed to consider carefully and solve, it shows good potential to be used in the future earthquake early warning systems for more accuracy modelling the site amplification factor.
Study on Site Amplification Factor Correction for Earthquake Early Warning System
