电阻率层析成像技术在琼东北活动断裂探测中的应用

琼东北1605年琼山地震发震的中心区域东寨港东侧发育多组近东西向和北西向的活动断裂,且均为隐伏断裂。为探明断裂的分布位置及其活动性,现采用电阻率层析成像技术将其中琼山-铺前断裂(F8)以及F7、F6、F5共四条,北西走向断裂作为此次探测目标断裂。结合前人水文钻孔资料和断裂分布,在珠溪河北岸和罗豆农场北侧部署了三条电法探测线,结果表明区域沉积地层在三条反演剖面上均可以划分出三层视电阻率梯度带,与钻孔资料对应较好。同样,视电阻率对已知四条活动断裂均有明显特征的低阻异常反映,除断裂F7的倾向解释存在争议外,其余三条断裂解释均得到钻孔验证。

Application of the resistivity tomography method to detection of active faults Northeast of the Hainan Island

In the northeastern Hainan island, where the 1605 Qiongshan earthquake occurred, there exist many nearly EW-trending and NW-tren-ding active faults, all of which are buried at depth. This work attempted to clarify the locations and geometries of these faults using the resistivity tomo-graphy method, focusing on four NW trending ones, i. e. , the Qiongshan-Puqian fault(F8),F7,F6,and F5. According to previous hydrological bore-hole data, three electrical survey lines were deployed on the north side of the Zhuxi River and LuoDou farm. The results show that regional sedimentary strata can be delineated by apparent resistivity gradient zones on three inversion profiles, respectively,well consistent with the borehole data. Meanwhile, obvious low-resistivity anomalies are present on the four known active faults,and except F7 tending to be controversial in explanation,the other three in-terpreted faults are all confirmed by drilling data.