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首页> 外文期刊>Bulletin of the Seismological Society of America >Variations of P-Wave Travel-Time Residuals before and after the 1999 Chi-Chi, Taiwan, Earthquake
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Variations of P-Wave Travel-Time Residuals before and after the 1999 Chi-Chi, Taiwan, Earthquake

机译：1999年台湾集集地震前后P波旅行时残差的变化

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摘要

P-wave velocity variations may provide precursory information before large earthquakes. We present results from a simple study on variations of P-wave travel-time residuals before and after the 1999 Chi-Chi, Taiwan, earthquake. The short-period seismic network deployed in Taiwan by the Central Weather Bureau (CWB) is routinely used for earthquake location. The accuracy of earthquake location is often judged by the travel-time residual of seismic waves. Because the velocity model used by the CWB was one-dimensional, the travel-time residuals will show lateral inhomogeneity of the velocity structures and unmodeled vertical structures. Also, the travel-time residuals may change with time if the velocity structure changes temporally. We used the data of the Central Weather Bureau Seismic Network (CWBSN) from 1991 to 2002 to obtain the difference between observed and calculated P-wave travel times, which is defined as the P-wave travel-time residual. The purpose of this study is to find the mean value of the P-wave travel-time residuals at each station and its possible temporal changes at stations near the Chelungpu fault. Our results show that the mean P-wave travel-time residuals at stations 40 km east of the Chelungpu fault changed very little before and after the Chi-Chi earthquake. But the mean P-wave travel-time residuals at the stations immediately west of the Chelungpu fault clearly changed before and after the Chi-Chi earthquake. The anomalous zone is bounded by stations NSY, TWQ1, TCU, WNT, WGK, CHN5, YUS, WDT, and WHF. These temporal changes of P-wave travel-time residuals can be attributed to changes in the velocity structure, which in turn might be caused by crustal deformation east of the Chelungpu fault beginning about 6 years before the Chi-Chi earthquake. In other words, before the Chi-Chi earthquake, there was a long-term 6-year precursor of P-wave velocity decrease possibly due to dilatancy or development of cracks. The variations of P-wave travel-time residuals with time at the anomalous stations are also confirmed by statistical tests that show clear significance. This method can be used to monitor and identify variations of P-wave travel-time residuals which may be precursors to a large earthquake.
机译：在大地震之前，纵波速度变化可能会提供先兆信息 。我们通过简单的研究 给出了1999年台湾集集地震前后P波传播时间残差变化的结果。中央气象局（sWB）在台湾部署的短期地震 网络通常用于地震定位。地震 定位的准确性通常由地震 波的传播时间残差来判断。因为CWB使用的速度模型是一维的，所以 的行进时间残差将显示 速度结构和未建模的垂直结构的横向不均匀性。另外，如果速度 结构随时间变化， 旅行时间残差可能随时间变化。我们使用1991年至2002年中央 气象局地震台网（CWBSN）的数据来 获得观测波与计算出的P波 之间的差异。传播时间，其定义为P波传播时间残差。 本研究的目的是找到P波传播时间残差的平均值。 Chelungpu断层附近各台站的温度及其可能的时间变化 。我们的结果表明， 切伦普断层以东40 km台站 的平均P波传播时间残差在 前后前后变化很小。集集地震。但是，在志吉浦地震前后，切伦浦断层以西的站点的平均P波传播时间残差 明显改变了。异常的 区域由站点NSY，TWQ1，TCU，WNT，WGK，CHN5， YUS，WDT和WHF界定。 P波传播时间 残余的这些时间变化可以归因于速度结构的变化，而 可能是由于 < / sup>切龙普断裂始于Chi-Chi 地震之前的大约6年。换句话说，在Chi-Chi地震之前，由于扩张或裂缝的发展，有一个长期的6年纵波速度下降的前兆，可能是 。异常站的P波 行进时间残差随时间的变化也通过具有明显意义的统计检验得到确认。 该方法可用于监视和识别 P波传播时间残差的变化，这些残差可能是大 地震的先兆。

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