2023 Fiscal Year Final Research Report
Does not seismic attenuation in the Earth really depend on ampligude??
| Project/Area Number |
20K20939
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| Research Category |
Grant-in-Aid for Challenging Research (Exploratory)
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| Allocation Type | Multi-year Fund |
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| Review Section |
Medium-sized Section 17:Earth and planetary science and related fields
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
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| Project Period (FY) |
2020-07-30 – 2024-03-31
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| Keywords | 地震波減衰 |
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| Outline of Final Research Achievements |
This study investigates whether attenuation is actually independent of seismic-wave amplitudes by systematic analysis of a large number of spectral amplitudes of co-located earthquake pairs with different observed amplitudes. We analyzed M3-5 intraslab earthquakes that occurred after the 2003 Miyagi-oki earthquake (M7.1) in NE Japan. The obtained results suggest that amplitude-dependent attenuation is required to explain the observations, which contradicts a long-standing recognition that amplitude-dependent attenuation is negligible for the propagation of seismic waves. Our model calculation suggests that Q^(-1) is proportional to the seismic amplitude, A, with the power of 0.1-0.2. Our result highlights the need to revisit and potentially rethink current models of the physical mechanisms influencing intrinsic attenuation.
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| Free Research Field |
地震学
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| Academic Significance and Societal Importance of the Research Achievements |
地震波の減衰は波の振幅に影響を与えるため，強震動の数値シミュレーションなどにも重要なパラメータである．しかしながら，これまでの研究では減衰は振幅に因らず一様であると仮定されてきた．もし減衰に振幅依存がある場合，強震動を正しく評価するためには，振幅依存を考慮する必要がある．特に強震動は振幅が大きいため，減衰の非線形性の影響をより強く受けるからである．本研究の結果は，大地震の地震動予測の高精度化に資すると考えられる．
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