Magnetotelluric Investigation In The Huanghua Depression And Its Adjacent Areas

摘要

In order to delineate shallow and deep structures of the Huanghua depression, we conduct a magnetotelluric (MT) investigation in the depression and its adjacent areas. The survey line includes 52 MT sites and crosses over 3 main tectonic units: the Chengning Uplift, the Huanghua Depression, and the Cangxian Uplift. A remote reference station is set up to reduce noise disturbance. In data processing, we perform noise identification and manual selection of time series segments to improve data quality, and apply for a PCA (principal component analysis) based method to automatically identify apparent polarized resistivity curves of TE and TM modes. We use the 2-D continuous medium inversion method to obtain underground electrical distribution of the surveyed area. Using apparent tipper data, and combined with seismic, gravity, and magnetic data of the study area, fault system is delineated from the MT inversion profile. The inversion results (the maximum depth is 15 Km) of the MT data reveal that there may exist a south-tilted overthrust fault on the conjunction part between the Chengning Uplift and the Qikou Sag. It can deduced that the thrust fault was formed when pre-Cenozoic strata of the northern Chengning Uplift underwent Indosinian extrusion. The fault zone may indicate a prospective target area for pre-Cenozoic oil and gas resources.