| 講演要旨(和文) | | 2004年新潟県中越地震Mj6.8では震源直上の旧K-NET小千谷などで最大加速度1Gを超える大振幅の強震記録が得られた。震源域は地盤構造が複雑であり，小千谷市では地盤増幅の影響で本震時の地震動特性が局所的に異なっていたことが指摘されている（Yamanaka et al., 2005）。本検討では，連続微動観測記録から評価した相互相関関数（地元ほか,2018）を用いて，笠松・山中(2018)の方法に基づいた波形インバージョンにより当地域の二次元S波速度構造推定を推定した。当地域の地盤構造は非常に複雑であり，地震観測点付近は地盤増幅の影響で局所的に地震動振幅が大きくなる場所に位置することが分かった。 |
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| | 講演要旨(英文) | | Strong ground motions with amplitudes exceeding maximum accelerations of 1G were recorded in Ojiya City in the Mid Niigata Prefecture Earthquake in 2004 (Mj6.8). Yamanaka et al. (2005) have indicated that characteristics of the motions were locally different due to site amplification factors. We applied our waveform inversion technique for retrieving a 2D S-wave velocity profile to the area using cross-correlation functions evaluated by the seismic interferometry analyses. We found that the distribution of the top of a layer with an S-wave velocity of 0.6 km/s is significantly complicated and the observatories for the strong motions were located where a layer having an S-wave velocity of 0.35 km/s is locally distributed. |
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