Mechanism of Different Coseismic Water-Level Changes in Wells with Similar Epicentral Distances of Intermediate Field
Mechanism of Different Coseismic Water-Level Changes in Wells with Similar Epicentral Distances of Intermediate Field
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DOI：
10.1785/0120100104
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发表时间：
2011-08
影响因子：
3
通讯作者：
Yan Zhang;Fu-qiong Huang
中科院分区：
文献类型：
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作者：
Yan Zhang;Fu-qiong Huang
本文观测了中国大陆汶川S 8.0级地震期间各监测站水位的变化。在中场，我们观测到了震中距相近的井中不同幅度的同震水位变化。为了研究这些同震水位变化的机制，我们用Okada位错模型(Okada，1992；Lin和Stein，2004；Toda et al.，2005)。将孔弹性理论计算的同震水位变化与实际水位变化进行比较，可以判断孔弹性理论是否适用于该井的含水层。研究发现，孔弹性理论适用于震中距≲1.5断层破裂长度的地区。考虑到这一点，我们发现这些井的水位变化何时可以用孔洞弹性理论来解释，而震中距相近的井水位变化的差异主要与Skempton系数B的差异有关。否则，水位变化可能是由地震波的转换引起的，因为它通常比不排水的膨胀和固结引起的水位变化大，变化也更缓慢。
Water-level changes at different monitoring stations are observed during the Wenchuan earthquake ( M S 8.0) in the Chinese mainland. In the intermediate field, we observed coseismic water-level changes of different amplitude in wells with similar epicentral distances. In order to study the mechanism of those coseismic water-level changes, we calculated the static strain change with the Okada dislocation model (Okada, 1992; Lin and Stein, 2004; Toda et al. , 2005). By comparing the calculated coseismic water-level change based on the poroelastic theory with the observed water-level change, we can judge whether the poroelastic theory can be applied to the aquifer of the well. From our research, we find the poroelastic theory can be applied to the area with epicentral distance≲1.5 fault rupture length. Bearing this in mind, we find that when the water-level change of those wells can be explained by the poroelastic theory and that the difference of the water-level change in wells with similar epicentral distances is mostly related to the difference of Skempton’s coefficient B . Otherwise, the water-level change may be induced by the transition of the seismic waves because it is usually larger than the one induced by the undrained dilatation and consolidation, and changes more gradually.