大地电磁测深在珊溪水库诱发地震研究中的应用
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摘要
珊溪水库位于浙江省东南的温州市境内,曾经多次发生震群型地震,地震的活动持续15年以上,最大震级达M_L4.6。为了查明该地区深部构造特征,分析地震与深部构造之间的关系,在水库库区布设了一条长度为16.2 km的大地电磁测深(MT)测线。探测结果表明,在12 km深度范围内,电阻率剖面在纵向上主要呈现低阻、高阻、低阻特征,对应可划分出三个地层单元。横向上整体变化均匀,第一层和第二层局部存在低阻异常,反应出断层构造特征。通过剖面低阻异常特征分析,确定了库区断裂的深部构造特征及地层的渗漏特征,并探讨了它们与珊溪水库地震之间的关系。研究结果表明,北西走向的双溪-焦溪垟断裂为珊溪水库地震的主要发震构造,地下水沿着该断裂往下渗透使得深部岩石强度变低而发生了地震。
Shanxi reservoir is located in the Wenzhou, southeast of Zhejiang province, where swarm-type earthquakes have occurred for many times. The activity of the earthquake lasted more than 15 years, with a maximum magnitude of ML4.6. In order to find out the characteristics of deep structures in this area and analyze the relationship between earthquakes and deep structures, a 16.2 km long MT sounding line was laid in the reservoir area. The results show that the resistivity profiles are characterized by low resistance, high resistance and low resistance in the vertical direction within the depth range of 12 km, which can be divided into three stratigraphic units.Horizontally, the change of resistivity is well-distributed on the whole,but the first and second layers have low resistance anomalies, which reflect the fault tectonic feature.Through the analysis of the characteristics of low resistivity anomalies in the section, the deep structural characteristics of the faults in the reservoir area and the seepage characteristics of the strata are determined, and the relationship between them and the earthquake of Shanx reservoir is discussed. The results show that Shuangxi-Jiaoxiplacanticline fault with the northwest trendingis the main seismogenic structure of Shanxi reservoir earthquake, and the ground water seepage downward along it makes the strength of deep rock become lower, therefore, the earthquake occurs.
Shanxi reservoir is located in the Wenzhou, southeast of Zhejiang province, where swarm-type earthquakes have occurred for many times. The activity of the earthquake lasted more than 15 years, with a maximum magnitude of ML4.6. In order to find out the characteristics of deep structures in this area and analyze the relationship between earthquakes and deep structures, a 16.2 km long MT sounding line was laid in the reservoir area. The results show that the resistivity profiles are characterized by low resistance, high resistance and low resistance in the vertical direction within the depth range of 12 km, which can be divided into three stratigraphic units.Horizontally, the change of resistivity is well-distributed on the whole,but the first and second layers have low resistance anomalies, which reflect the fault tectonic feature.Through the analysis of the characteristics of low resistivity anomalies in the section, the deep structural characteristics of the faults in the reservoir area and the seepage characteristics of the strata are determined, and the relationship between them and the earthquake of Shanx reservoir is discussed. The results show that Shuangxi-Jiaoxiplacanticline fault with the northwest trendingis the main seismogenic structure of Shanxi reservoir earthquake, and the ground water seepage downward along it makes the strength of deep rock become lower, therefore, the earthquake occurs.
引文
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[2] 钟羽云,周昕,张帆,等. 2006年温州珊溪水库地震序列特征. 华南地震,2006,27(1):21-30.
[3] 钟羽云,张帆,赵冬. 珊溪水库ML4.6震群精确定位与发震构造研究. 地震研究,2011,34(2):158-165.
[4] 钟羽云,周昕,张帆,等. 水库水位变化与地震活动关系研究. 大地测量与地球动力学,2013,33(2):35-40.
[5] 李金龙,邹振轩. 浙江珊溪水库地震:震源参数测定及断层结构和应力状态描述. 地震地磁观测与研究,2008,29(1):27-35.
[6] 朱新运,张帆,于俊谊. 浙江珊溪水库地震精细定位及构造研究. 中国地震,2010,26(4) :380 -390.
[7] 马志江,钟羽云,韩用兵,等. 温州珊溪水库诱发地震构造条件[J]. 地球科学,2016, 41(8): 1 413-1 423.
[8] 周昕,傅建武,杨福平,等. 水库地震,诱发还是触法. 华南地震,2005, 25(2):13-21.
[9] ROY A, APPARAO A. Depth of investigation indirect current methods[J].Geophysics,1971, 36: 43-959.
[10] 邱松,龚育龄,王粤.江西余江马荃地区EH4大地电磁测深资料解释. 工程地球物理学报,2013,10(6):795-799.
[11] 张健,李忠,鲁霞. 大地电磁测深在安徽某工区地热勘查中的应用研究. 工程地球物理学报,2010,7(5):574-578.
[12] 张胜业,潘玉玲. 应用地球物理学原理[M].武汉: 中国地质大学出版社, 2000:273-279.
[13] 王家映.我国大地电磁测深研究新进展[J].地球物理学报,1997,40(增刊):209-112.
[14] 姚姚. 地球物理反演基本理论与应用方法[M].武汉: 中国地质大学出版社,2000.
[15] 蔡军涛,陈小斌. 大地电磁资料精细处理和二维反演解释技术研究(二)——反演数据极化模式选择[J]. 地球物理学报,2010, 53(11):2 703-2 714.
[16] 叶涛,陈小斌,严良俊. 大地电磁资料精细处理和二维反演解释技术研究(三)——构建二维反演初始模型的印模法[J]. 地球物理学报,2013, 56(10):3 596-3 606.
[17] 钟羽云,朱新运,张震锋,等. 飞云江珊溪水库地震[M]. 杭州:浙江大学出版社,2017.