复杂地区综合地球物理勘探方法技术应用

Application of Comprehensive Geophysical Exploration Methods and Technologies in Complex Areas

扬子准地台位于中国中西部,是一个复杂的大地构造区域。该区地表地质条件差,相对高差较大,最大可达800m~1000m,有很多喀斯特溶洞形成在中、古生代碳酸盐岩地层中。地底构造复杂,地质构造倾斜角较大,正断层陡峭。地形落差大,地面地质构造不平滑,形成了强烈的透射面波,这对地震勘探产生了严重的透射影响,而复杂的地底结构也增加了深层地震灾害的显像难度。此外,快速火成岩构造和浅部碎屑岩广泛存在,使得反射面动能无法向深层传播,进一步增加了地震勘探的难题。碎屑岩的存在也屏蔽了下伏地质构造的散射动能,导致目的层反射波较弱。地面的多样性也给作用力和电法等地球物理方法增加了一定的技术难点。复杂的地貌波动和地面非均质体的发育也会导致重力异常的失真;在地貌落差的推动下,地表浅部电荷分布不均匀,使得MT或EMAP视电阻曲线图出现严重失真。因此,在这一地区进行地球物理勘探具有一定的困难。

Tectonically located in the central and western parts of the Yangtze paraplatform,with the upper part leaning towards the east,it is a complex geophysical exploration area.The surface geological conditions in this area are poor,and the relative elevation difference is large,up to 800m~1000m,with more outcrops.Karst Plateau caves are developed in the middle and Paleozoic Carbonate rock strata;The underground structure is complex,with a relatively large inclination angle of geological structures and steep normal faults.The significant terrain drop and uneven geological structure on the ground constitute highly dynamic transmission surface waves,which also have serious transmission effects in seismic exploration.The presence of complex underground structures in seismic exploration also adds difficulty factors to the imaging of deep seismic disasters.In addition,the rapid geological structure of Igneous rock and the widespread development of Clastic rock in the shallow part make the kinetic energy of the reflector shield away and cannot spread to the deep layer,which further enhances the difficulties in seismic exploration.The development of Clastic rock also shields the scattering kinetic energy of the underlying geological structure,resulting in the weak reflection wave group of the target layer.The diversity of ground requirements has added certain technical difficulties to the forces and electrical methods(MT,EMAP,etc.).The strong geomorphic fluctuation and the development of surface heterogeneity will also lead to the loss of frame of Gravity anomaly;Under the promotion of geomorphic drop,the heterogeneity of surface charges in shallow areas is significant,resulting in severe loss of frame in MT or EMAP apparent resistance curves.Therefore,conducting geophysical exploration in this area has certain difficulties.