【摘要】 地球介质的衰减特性可以从地震波中的频谱信息中获取,并且能够提供地球内部结构非均匀性的重要信息.与大量的速度结构研究相比,对衰减结构的研究却较少,且大多仅对日本群岛局部地区做研究.本文运用ML振幅层析成像技术反演获得了整个日本群岛上地壳的品质因子Q0值(1Hz时的Q值).计算中共利用了日本Hi-net台网971个台站记录到的5559个地震事件,超过60000条Sg波最大振幅-频率数据,并且满足震中距小于2°、震源深度小于10km.计算结果表明,低Q0值区域主要存在于日本群岛的中央火山带,与日本新生代以来的火山分布非常一致;同时,位于从神户到京都东北地区、以及四国岛东部等地的非火山区,断层密集,对应的Q0值也很低;另外,西太平洋俯冲海沟与日本群岛东海岸之间的区域也是低Q0值区,这说明高温、岩石强烈破碎、深厚的沉积物是造成地震波强烈衰减的主要原因.高Q0值主要分布在中央火山带前缘与日本东海岸之间.更多还原

【Abstract】 Seismic attenuation(Q-factor)can be estimated by extracting the amplitude-frequency information contained in seismic waveforms.We applied ML amplitude tomography to estimate attenuation of upper crust in Japan.More than 60000 Sg-wave maximum amplitude data from 5559 events recorded by 971 stations were selected from the dense High-Sensitivity Seismographic Network(Hi-net)under the condition that epicentral distance is less than 2°;event depth is less than 10km.The lateral S-wave Q-factor variations of upper crust at 1Hz in Japan were obtained,and the result indicates that the low Q values exist in the central Japan islands,and have almost the same distribution with volcanoes;the low-Q zones also exist in non-volcanic regions at the Kyoto and Kobe prefectures,and eastern Shikoku with dense faults there;in addition,low Q was found between eastern coast and Japan trench.These suggest that the high attenuation(low Q value)results from high temperature,cracked rocks and thick sediment.The high Q values mainly exist between the front of volcanoes and the Japanese east coast.更多还原