丽江7.0级地震地下流体异常特征
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摘要
通过对１９９６年２月３日云南丽江Ｍｓ７０地震前震中周围水位、水氡、水汞、泉点宏观等地下流体共７１个台项观测资料的异常及综合特征分析，初步认为震前异常数量较多，异常时间分布具有整体性、同步性、集中性的特点，但异常主要集中在短期阶段，临震异常不突出；空间分布具有集中性和非均匀性，孕震区至远场影响区的异常比例最高，震源区内为相对“盲区”，且突出而肯定的宏观异常极少；异常的时空演变特征复杂，总体没有规律变化；异常主要分布在川滇菱型块体构造的两个尖角部位和构造协同活动区；上升型异常主要分布在洱源以南的红河断裂带及附近的右旋张扭断层区，分布走向与区域应力场和震源机制解的主压力轴方向基本一致，下降型异常主要分布在断块附近的逆掩断层区，分布走向与震源机制解的主张力方向基本一致。最后对主要异常特征可能的物理机制进行了探讨
Through synthetic analysis of the anomalous characters of water level, radon and mercury in groundwater, macrospring points and other underground fluids in the data observed from 71 stations or points around the epicenter prior to the Ms 7 0 Lijiang earthquake in Yunnan on Feb 3, 1996, some preliminary knowledges are obtained as follows: The numerous anomalies before the earthquake in temporal distribution were characterized by entirety, synchronism and concentrativeness, however, most of the anomalies were concentrated in short-term stage, without prominent variations of impending earthquake and spatial distribution was characterized by concentativeness and inhomogeneity, having the highest proportion from the seismogenic to far field areas and relatively “blind area” in the focal region and extremely scant macroanomalies with positivity The anomalise displayed complex character of temporal -spatial evolution, without variation regularity in the whole and were disfributed mostly in the two pointed angle positions and tectonic coordinate active areas in the lozenge -shaped block structure of Sichuan-Yunnan The anomales in increaase type were distributed mostly in Red River fault zone to the south of Eryuan and in right-lateral tenso-torsiona fault zone near Eryuan, with the strike being roughly in accordance with the principal tensile orientation of regioanal stress field and focal mechanism solution and the anomalies in decrease type were distributed mostly in overthrust fault zone near the block, with the strike being roughly in accordance with the principal tensile orientation of the focal mechanism solution Lastly, possible physical mechanism of the main characters of the anomalies is approached in the paper
Through synthetic analysis of the anomalous characters of water level, radon and mercury in groundwater, macrospring points and other underground fluids in the data observed from 71 stations or points around the epicenter prior to the Ms 7 0 Lijiang earthquake in Yunnan on Feb 3, 1996, some preliminary knowledges are obtained as follows: The numerous anomalies before the earthquake in temporal distribution were characterized by entirety, synchronism and concentrativeness, however, most of the anomalies were concentrated in short-term stage, without prominent variations of impending earthquake and spatial distribution was characterized by concentativeness and inhomogeneity, having the highest proportion from the seismogenic to far field areas and relatively “blind area” in the focal region and extremely scant macroanomalies with positivity The anomalise displayed complex character of temporal -spatial evolution, without variation regularity in the whole and were disfributed mostly in the two pointed angle positions and tectonic coordinate active areas in the lozenge -shaped block structure of Sichuan-Yunnan The anomales in increaase type were distributed mostly in Red River fault zone to the south of Eryuan and in right-lateral tenso-torsiona fault zone near Eryuan, with the strike being roughly in accordance with the principal tensile orientation of regioanal stress field and focal mechanism solution and the anomalies in decrease type were distributed mostly in overthrust fault zone near the block, with the strike being roughly in accordance with the principal tensile orientation of the focal mechanism solution Lastly, possible physical mechanism of the main characters of the anomalies is approached in the paper
引文
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