Inversion of Source Parameters and Site Effects from Strong Ground Motion Records using Genetic Algorithms

Abstract

The low-frequency flat levels and corner frequencies of the aftershocks of the Kobe earthquake, together with the site effects of the recording stations, are inverted by using genetic algorithms. All records were corrected by the quality factor, Q, of propagation-path, and for each aftershock, a different omega-squared model was assumed such that the low-frequency flat levels and corner frequencies would minimize the standard deviation of the site effects at all stations. It was observed that site effects for rock sites showed significant amplification at high frequencies. This amplification was found to correlate with spectral ratios of records located at 70-m depth and at the surface for one of the stations. After estimating the seismic moment and the stress drop, it was observed that the relation of the seismic moment, M 0 , versus the corner frequency, fo, followed the scaling law M 0 ␣ fo ‫3מ‬ . Large values of stress drop were found around asperities on the fault zone and at depth.

An inversion of site response and Lg attenuation using Lg waveform

“…Based on this profile and seismic wave spectral ratios, we present a joint inversion method by which parameters of site response and attenuation can be separated from each other. This method is different from Moya's method (Moya et al, 2000) in that, in considering the source effects it is independent on the source model. The method reduces simplification process used in other methods and decreases errors caused by simplification.…”

“…This simplification in turn introduces corresponding error into the determined site response results. Based on Brune model (1970Brune model ( , 1971, Moya et al (2000) addressed joint inversion method of source parameters and site response. This method is good at separating site response and path effects, but more replies on model result.…”

Application of apparent stress in earthquake prediction

“…Then, the low-frequency flat level Ω 0 and the corner frequency f c of source displacement spectrum can be calculated for each earthquake. These two parameters should be inverted by the genetic algorithm, so as to greatly reduce the effect of artificial factors on the reliability of calculated results (Moya et al, 2000). Finally, equation (3) is used to calculate the apparent stress values of moderate-small earthquakes (LIU et al, 2006).…”

Study on inelastic attenuation coefficient, site response and source parameters in Shanxi region

“…Moya's method is used to determine the source-spectrum parameters of each earthquake and the site response of stations (Moya, et al, 2000). First, the Brune source-spectrum parameters are selected for each earthquake (Brune, 1970(Brune, , 1971, and each parameter is used to calculate the site response of the station that has recorded the earthquake.…”

“…In this case, the site response has nothing to do with frequency basically. The method of Moya, et al (2000) calculates source parameter and site response simultaneously by genetic algorithm. However, the method can only be used under the supposition that geometric spreading and inelastic attenuation parameters are given.…”