Estimation of the Low-Frequency Q-Value (Below 1Hz)

Abstract eng:
Studies that estimate low-frequency Q-value are very scarce. In most of them estimations are made by eye or by trial and error, without any systematic inversion approach. In this study, we propose nonlinear waveform inversion methodology and estimate low-frequency Q-value from the observation data. Results will help us to improve accuracy of the numerical simulations of the long-period waves. The inversion methodology used in this study consists of three steps. Step 1: Compile 1-D velocity models for every observational site in the target area, source region of the 2000 West Tottori earthquake. Step 2: In order to test velocity models, we compared synthetic and observed waveforms. Step 3: Use grid search method to estimate Q-value and linear inversion to estimate corrections to the source and site effects. Results of inversion show that estimated value in low-frequency range, Q = 80-180, agrees well with the results of spectral inversion in high frequency range, in case of a realistic ray-theory geometrical spreading is considered.

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