Study on the fluctuation of seismic wave amplitude due to random heterogeneity of crustal structure

2020 Fiscal Year Final Research Report

• Project/Area Number: 18K03786
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 17040:Solid earth sciences-related
• Research Institution: Yokohama City University
• Principal Investigator: Yoshimoto Kazuo 横浜市立大学, 理学部, 教授 (10281966)
• Co-Investigator(Kenkyū-buntansha): 武村 俊介 東京大学, 地震研究所, 助教 (10750200) ; 中原 恒 東北大学, 理学研究科, 准教授 (20302078)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: 地震波 / 振幅の揺らぎ / ばらつき / 地殻構造 / ランダム不均質性

Outline of Final Research Achievements

We investigated the characteristics of the fluctuations of seismic-wave amplitudes and travel times due to short-wavelength random heterogeneity of crustal structure on the basis of numerical simulation of seismic wave propagation. We confirmed that the fluctuations of P-wave and S-wave amplitudes increase with distance near the hypocenter, and the characteristics are more noticeable at higher frequencies. Within the range of parameters used in this study, the larger the correlation distance and the magnitude of the fluctuations of the short-wavelength random heterogeneity, the larger the amplitude fluctuations are demonstrated. In addition, we found that the travel-time fluctuation also increases with the hypocentral distance. It was confirmed that the travel-time fluctuations (standard deviation) of P-waves are modeled by the predictions of Markov approximation theory.

Free Research Field

固体地球科学

Academic Significance and Societal Importance of the Research Achievements

S波の振幅のばらつきの特性の把握は、地震工学における地震動予測の高度化（予測誤差の評価）の観点からも重要視されている。本研究では、地殻構造が短波長ランダム不均質性を有する場合、地震波伝播の物理特性から、地震動予測に一定レベルの不確定性が発生することを示した。今後、地殻構造の短波長ランダム不均質性を正確に把握することで、物理モデルに基づく予測誤差を反映させた地震動予測が可能になるものと期待される。