西藏玛尼7.5级地震与云南的远场前兆异常
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摘要
远场前兆 ,是一种场兆 ,它是地壳构造活动的反映 ,往往也是强震连发的异常表现 ,它显示区域构造应力场的增强作用。 1996年 2月 3日丽江 7 0级大震后 ,云南省的前兆异常突出。前兆异常分布广 ,异常种类也多 ;有新的趋势性异常出现 ,持续多年的继承性异常也很多 ;有些前兆异常幅度类似于孟连、武定、丽江三次强震前的异常图象。 1997年 7～ 9月 ,这些趋势性异常或继承性异常出现转折与恢复 ,一些短期异常也趋于结束。如果说云南地区没有一次强震或周围地区没有一次大震即将发生 ,这些异常是很难得到解释的。1997年 11月 8日西藏玛尼发生 7 5级大震 ,正好在这个发震的时间段上。应该讲 ,这些前兆异常与 7 5级大震有关 ,属于远场前兆异常。这样 ,不仅可解释 1997年云南地区有异常而没有发生强震 ,也进一步说明这些前兆异常为远场大震异常。
The far-field precursor, as a precursor, is reflection of tectonic activity in crust and also often is anomalous expression of earthquake occurrence in succession, which displays distinct effect of regional tectonic stress field. There were prominent precursor anomalies in Yunnan Province after the M7 3 large Lijiang earthquake on February 3, 1996, with broad distribution, diversity, new tendency and continuity for many years. Anomalous amplitudes of some precursors were similar to anomalous images before the three strong earthquakes, the Menglian, Wuding and Lijiang earthquakes. Turning and recovery of tendency or inheritance anomalies took place and some short-term anomalies tended towards end from July to September in 1997. It would have been very difficult for interpreting the anomalies if there had not been a strong earthquake in Yunnan region or a large earthquake in its surrounding regions to be about occur. On November 8, 1997, a large earthquake of M7 5 occurred in Manyi, Tibet, which just dropped in this earthquake occurrence period. It should be said that these precursor anomalies were related to the M7 5 large earthquake and belong to far-field precursor anomalies, thus which not only can interpret why no strong earthquake occurred though there were anomalies in Yunnan in 1997, but also shows the precursor anomalies were the far-field anomalies for large earthquake.
The far-field precursor, as a precursor, is reflection of tectonic activity in crust and also often is anomalous expression of earthquake occurrence in succession, which displays distinct effect of regional tectonic stress field. There were prominent precursor anomalies in Yunnan Province after the M7 3 large Lijiang earthquake on February 3, 1996, with broad distribution, diversity, new tendency and continuity for many years. Anomalous amplitudes of some precursors were similar to anomalous images before the three strong earthquakes, the Menglian, Wuding and Lijiang earthquakes. Turning and recovery of tendency or inheritance anomalies took place and some short-term anomalies tended towards end from July to September in 1997. It would have been very difficult for interpreting the anomalies if there had not been a strong earthquake in Yunnan region or a large earthquake in its surrounding regions to be about occur. On November 8, 1997, a large earthquake of M7 5 occurred in Manyi, Tibet, which just dropped in this earthquake occurrence period. It should be said that these precursor anomalies were related to the M7 5 large earthquake and belong to far-field precursor anomalies, thus which not only can interpret why no strong earthquake occurred though there were anomalies in Yunnan in 1997, but also shows the precursor anomalies were the far-field anomalies for large earthquake.
引文
〔1〕杨继登 .西藏发生大震的危险性分析 .高原地震 ,1999,11(1) :2 1～ 2 6
〔2〕李献智 .对地震前兆的一些思考 .地震 ,1998,2 (18) :16 3～ 170
〔2〕李献智 .对地震前兆的一些思考 .地震 ,1998,2 (18) :16 3～ 170
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