Asperity map along the subduction zone in northeastern Japan inferred from regional seismic data
Asperity map along the subduction zone in northeastern Japan inferred from regional seismic data
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DOI：
10.1029/2003jb002683
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发表时间：
2004-07
影响因子：
--
通讯作者：
Y. Yamanaka;M. Kikuchi
中科院分区：
文献类型：
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作者：
Y. Yamanaka;M. Kikuchi
[1]为了考察凹凸体的特征行为，我们研究了过去70年来日本东北部东北地区近海板间大地震的震源过程。在该地区，7级地震的重复间隔约为30年。自20世纪初以来，日本气象厅一直在使用强震地震仪进行地震观测。我们收集了这些地震记录，以便进行波形反演。在此基础上，我们对1930年后发生的8次地震的大滑移区(凹凸区)进行了识别，并绘制了凹凸区图。日本东北部单个凹凸体的典型大小为M7级，当几个凹凸体同时发生时，可能会引发M8级地震。我们认为东北近海的粗糙度分布可以分为三种不同的类型。在北部(40°-41.3°N)，凹凸体中的地震耦合几乎为100%，且规模较大。在中部(39°-40°N)，大地震释放的地震矩很小，粗糙度较小。南部(37.8°-39°N)地震耦合中等。这种弱地震耦合可能与海底地形特征及俯冲板块上的沉积物和水有关。我们的结果还表明，凹凸体一般倾向于远离震中(初始破裂)，余震发生在凹凸体周围的区域。
[1] In an attempt to examine the characteristic behavior of asperities, we studied the source processes of large interplate earthquakes offshore of the Tohoku district, northeastern Japan, over the past 70 years. In this area, earthquakes of M7 class have a recurrence interval of about 30 years. Seismic observation using a strong-motion seismometer has been carried out by the Japan Meteorological Agency since the beginning of the 1900s. We collected these seismograms in order to make a waveform inversion. On the basis of the derived heterogeneous fault slip, we identified large slip areas (asperities) for eight earthquakes which occurred after 1930, and we constructed an asperity map. The typical size of individual asperities in northeastern Japan is M7 class, and an M8 class earthquake can be caused when several asperities are synchronized. We propose that the patterns of asperity distribution beneath offshore Tohoku fall into three different categories. In the northern part (40°–41.3°N) the seismic coupling in the asperity is almost 100%, and the size is large. In the central part (39°–40°N), little seismic moment has been released by large earthquakes, and the asperity size is small. In the southern part (37.8°–39°N) the seismic coupling is medium. The weak seismic coupling may be related to submarine topographical features and to the sediment and water along the subducting plate. Our results also suggest a general tendency for the asperities to be located away from the hypocenters (initial break), with aftershocks occurring in the area surrounding the asperity.