Slow initial phase generated by microearthquakes occurring in the western Nagano Prefecture, Japan ‐The source effect‐
Slow initial phase generated by microearthquakes occurring in the western Nagano Prefecture, Japan ‐The source effect‐
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日本长野县西部发生的微地震产生的缓慢初始阶段 ‐震源效应‐
DOI：
10.1029/1999gl900404
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发表时间：
1999
影响因子：
5.2
通讯作者：
M. Ando
中科院分区：
文献类型：
--
作者：
Y. Iio;S. Ohmi;R. Ikeda;E. Yamamoto;Hisao Itô;H. Sato;Y. Kuwahara;T. Ohminato;B. Shibazaki;M. Ando
对长野县西部发生的微震的近震源观测表明，记录到的缓慢初始阶段的持续时间几乎不受震源距离的影响。虽然进一步观察发现，慢初始阶段的持续时间随着焦距的增加而略有增加，但它们与焦距不成正比。因此，慢初相并不主要反映整个路径Q。如果慢初相与整个路径Q的强滞弹衰减相结合，则2.4级地震的P波速度脉冲在震源处的上升时间估计为3ms左右，2.4级地震的震源半径估计为10m左右，这一震源半径对于M2.4来说太小了。这表明缓慢的初始相并不是由表层强烈的滞弹性衰减引起的。很可能缓慢的初始阶段主要反映的不是路径效应，而是震源效应。
Near‐source observations of microearthquakes occurring in the Western Nagano prefecture show that durations of recorded slows initial phases were almost constant independently of focal distance. Although a closer inspection revealed that the durations of the slow initial phases slightly increased with focal distance, they were not proportional to focal distance. Thus, it is concluded that the slow initial phases do not mainly reflect the whole path Q. If the slow initial phases were attributed to the strong anelastic attenuation in the surface layer combined with that of the whole path Q, the rise time of the P‐wave velocity pulse at the source for a M2.4 event would be estimated as about 3 ms and the source radius of the M2.4 event would be estimated as about 10 m. This value of the source radius is too small for M2.4. This suggests that the slow initial phase does not arise from the strong anelastic attenuation in the surface layer. It is likely that the slow initial phase does not mainly reflect a path effect but a source effect.