| 講演要旨(和文) | | 鉄道における早期地震警報では，震央距離はP波初動の立ち上がりから推定される．この推定はP波振幅が震央距離の増大に伴って減衰するという一対一の関係に基づく．この減衰の原因は幾何減衰，散乱・内部減衰だと考えられている．しかしながら，同じ震央距離に対してもP波初動の立ち上がりは大きくばらつき，その結果，推定された震央距離は時に100kmオーダーの誤差を含んでいる．本研究では，このばらつきの原因が散乱・内部減衰にあると考え検証する．その知見に基づいて，震央距離推定精度の向上方法を考える． |
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| | 講演要旨(英文) | | Epicentral distance is estimated from growing curves of initial P-wave in the Earthquake Early Warning system in Railways. This estimation is based on the simple one-to-one relationship between P-wave amplitude and epicentral distance that the P-wave amplitude decreases as the epicenter is farther, which is due to geometrical spreading, scattering and intrinsic attenuation. However in practice, the estimated epicentral distances from the P-wave amplitude include a considerable error, which sometimes reaches 102 km order. In this study we reveal that the error is due to regional difference in heterogeneous conditions. The regionally different heterogeneities scatter and absorb P-wave amplitude in the different manners. We propose a robust method to estimate epicentral distance considering the regional heterogeneous condition. |
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