隱伏斷層破碎帶的大地電磁二維正演模擬
發(fā)布時間：2018-10-20 18:37
【摘要】：隱伏斷層的探測對地熱資源調(diào)查，深部礦床的分布，地下水的賦存，大型工程的選址等都有意義。大地電磁法（MT）因其自身特點在對地下深部斷層構造及破碎帶的勘探中發(fā)揮著重要的作用。通過建立不同的斷層破碎帶的模型，分析大地電磁法兩種極化模式對模型的響應特征，可以為實際資料的解釋提供一定幫助。 本文基于有限單元法，對所建立的正斷層、逆斷層、低阻覆蓋層模型，進行大地電磁二維正演模擬，得到大地電磁法對不同斷層模型的響應特征：（1）阻抗相位相對于視電阻率受低阻覆蓋層的影響較小，對地下巖層的電性結構整體形態(tài)反映較好。（2）當斷層斷距較大時，可以根據(jù)兩種極化模式在高頻部分是否出現(xiàn)明顯的“逆推”現(xiàn)象來區(qū)分正斷層與逆斷層；當斷層的斷距較小或低阻覆蓋層較厚時，從兩種極化模式的斷面圖中較難區(qū)分正斷層與逆斷層。 通過對破碎帶模型正演模擬，得到大地電磁的響應特征是：（1）當破碎帶的電阻率低于第一層介質(zhì)的電阻率時，視電阻率和阻抗相位斷面圖在破碎帶處曲線較陡，出現(xiàn)凹陷形態(tài)；當破碎帶的電阻率大于第一層介質(zhì)的電阻率時，視電阻率和阻抗相位斷面圖中凹陷形態(tài)消失，在斷層破碎帶處的曲線變緩。（2）模型中，，斷層傾角為30°，45°，60°時，視電阻率斷面圖中在斷層低阻破碎帶處都有明顯凹陷形態(tài)，對破碎帶傾角反映不明確，阻抗相位對破碎帶傾角反映相對較好。（3）對斷層低阻破碎帶寬度的正演模擬可知，隨著破碎帶逐漸變寬，視電阻率曲線與阻抗相位曲線在破碎帶位置逐漸變陡。 最后，通過對某工作區(qū)進行大地電磁測深工作，在分析總結大地電磁對斷層模型響應特征的基礎上，推斷出工作區(qū)測深斷面圖中三處斷層的位置，并且與實際地質(zhì)資料相符，說明本文模型具有一定實用意義。
[Abstract]:The detection of hidden faults is of great significance to the investigation of geothermal resources, the distribution of deep deposits, the occurrence of groundwater, the location of large projects, and so on. Magnetotelluric method (MT) plays an important role in the exploration of deep fault structures and fracture zones because of its own characteristics. The response characteristics of two polarization modes of magnetotelluric method to the model are analyzed by establishing different models of fault fracture zone, which can provide some help for the interpretation of actual data. Based on the finite element method, the magnetotelluric two dimensional forward modeling of normal fault, reverse fault and low resistance overburden layer is carried out in this paper. The response characteristics of magnetotelluric method to different fault models are obtained as follows: (1) the impedance phase is less affected by the low resistivity overburden than the apparent resistivity, and the electrical structure of underground rock is well reflected. (2) when the fault break is large, The normal fault and the reverse fault can be distinguished according to whether there are obvious "backward" phenomena in the high frequency part of the two polarization modes, when the fault spacing is smaller or the low resistivity overburden is thicker, It is difficult to distinguish the normal fault from the reverse fault from the two polarization patterns. Through forward modeling of the fracture zone model, the characteristics of magnetotelluric response are as follows: (1) when the resistivity of the broken zone is lower than that of the first layer medium, the curve of apparent resistivity and impedance phase profile is steep and the shape of depression appears in the broken zone; When the resistivity of the fractured zone is greater than that of the first layer of medium, the shape of the sag in the apparent resistivity and impedance phase profile disappears, and the curve at the fracture zone slows down. (2) in the model, the dip angle of the fault is 30 擄, 45 擄and 60 擄. In the apparent resistivity fracture diagram, there are obvious concave forms at the low resistivity fracture zone of the fault, the dip angle of the fracture zone is not clear, and the impedance phase reflects the dip angle of the fracture zone relatively well. (3) the forward modeling of the width of the low resistivity fracture zone of the fault can be seen. The apparent resistivity curve and impedance phase curve become steeper in the broken zone as the breakage zone becomes wider and wider. Finally, by doing magnetotelluric sounding in a working area, on the basis of analyzing and summarizing the characteristics of magnetotelluric response to the fault model, the location of three faults in the bathymetric section map of the working area is inferred, which is consistent with the actual geological data. It shows that this model has certain practical significance.
【學位授予單位】：太原理工大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：P631.325
本文編號：2284039
[Abstract]:The detection of hidden faults is of great significance to the investigation of geothermal resources, the distribution of deep deposits, the occurrence of groundwater, the location of large projects, and so on. Magnetotelluric method (MT) plays an important role in the exploration of deep fault structures and fracture zones because of its own characteristics. The response characteristics of two polarization modes of magnetotelluric method to the model are analyzed by establishing different models of fault fracture zone, which can provide some help for the interpretation of actual data. Based on the finite element method, the magnetotelluric two dimensional forward modeling of normal fault, reverse fault and low resistance overburden layer is carried out in this paper. The response characteristics of magnetotelluric method to different fault models are obtained as follows: (1) the impedance phase is less affected by the low resistivity overburden than the apparent resistivity, and the electrical structure of underground rock is well reflected. (2) when the fault break is large, The normal fault and the reverse fault can be distinguished according to whether there are obvious "backward" phenomena in the high frequency part of the two polarization modes, when the fault spacing is smaller or the low resistivity overburden is thicker, It is difficult to distinguish the normal fault from the reverse fault from the two polarization patterns. Through forward modeling of the fracture zone model, the characteristics of magnetotelluric response are as follows: (1) when the resistivity of the broken zone is lower than that of the first layer medium, the curve of apparent resistivity and impedance phase profile is steep and the shape of depression appears in the broken zone; When the resistivity of the fractured zone is greater than that of the first layer of medium, the shape of the sag in the apparent resistivity and impedance phase profile disappears, and the curve at the fracture zone slows down. (2) in the model, the dip angle of the fault is 30 擄, 45 擄and 60 擄. In the apparent resistivity fracture diagram, there are obvious concave forms at the low resistivity fracture zone of the fault, the dip angle of the fracture zone is not clear, and the impedance phase reflects the dip angle of the fracture zone relatively well. (3) the forward modeling of the width of the low resistivity fracture zone of the fault can be seen. The apparent resistivity curve and impedance phase curve become steeper in the broken zone as the breakage zone becomes wider and wider. Finally, by doing magnetotelluric sounding in a working area, on the basis of analyzing and summarizing the characteristics of magnetotelluric response to the fault model, the location of three faults in the bathymetric section map of the working area is inferred, which is consistent with the actual geological data. It shows that this model has certain practical significance.
【學位授予單位】：太原理工大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：P631.325
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