Observations of Changes in Waveform Character Induced by the 1999 Mw7.6 Chi-Chi Earthquake
Observations of Changes in Waveform Character Induced by the 1999 Mw7.6 Chi-Chi Earthquake
复制标题
1999年Mw7.6集集地震波形特征变化观测
DOI：
10.1029/2011gl049841
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
R.-J. Rau
中科院分区：
文献类型：
--
作者：
Chen;K.;T. Furumura;J. Rubinstein;R.-J. Rau
我们观察到台湾东部在1999年6 .6级赤赤地震后的重复地震波形的变化，而它们的重复周期似乎没有受到影响。在Chi - Chi事件发生时，波形相似度和速度变化的延迟相位明显减少。这些变化仅限于Chi - Chi震源周围70 × 100公里区域内的站点和路径，该区域地震强度和同震地表位移最大。这表明近表面的损伤是观测到的波形变化的原因。延迟在S波后期最大，达到大约120毫秒。这相当于路径平均波速降低约1%。也有证据表明，断裂带的破坏导致了下盘位置波形特征的变化，在下盘，震源-接收路径沿着破裂或穿过破裂传播。在我们的研究中，波形相似性的降低在最近的重复事件中持续存在（2007年11月15日），这表明Chi‐Chi地震引起的地下破坏在Chi‐Chi地震发生后的前8年内并没有完全愈合。
We observe changes in the waveforms of repeating earthquakes in eastern Taiwan following the 1999 Mw7.6 Chi‐Chi earthquake, while their recurrence intervals appear to be unaffected. There is a clear reduction in waveform similarity and velocity changes indicated by delayed phases at the time of the Chi‐Chi event. These changes are limited to stations in and paths that cross the 70 × 100 km region surrounding the Chi‐Chi source area, the area where seismic intensity and co‐seismic surface displacements were largest. This suggests that damage at the near‐surface is responsible for the observed waveform changes. Delays are largest in the late S‐wave coda, reaching approximately 120 ms. This corresponds to a path averagedSwave velocity reduction of approximately 1%. There is also evidence that damage in the fault‐zone caused changes in waveform character at sites in the footwall, where source‐receiver paths propagate either along or across the rupture. The reduction in waveform similarity persists through the most recent repeating event in our study (November 15, 2007), indicating that the subsurface damage induced by the Chi‐Chi earthquake did not fully heal within the first 8 years following the Chi‐Chi earthquake.