| Transient Electromagnetic Method is a kind of time domain electromagnetic exploration method. It uses the encouragement of step wave or other impulse current field source to produce the transition process field in earth. In the moment of shutting the power it produce the volute alternating electromagnetic field. From the abnormity of measuring the attenuation character of the second induction electromagnetic field, which produced by underground medium with time change, the conductive capacity and the position of the underground non-homogeneous substance can be analyzed. So it can resolve the geology problems. This method has the character of reconnoitering deeply, high ability of penetrating high resistance layer, little random disturbance, observing both far and near, observe in different time windows, receiving the geology information in different depth. So this method is widely used in source exploration and engineering measure. It became an important geophysics exploration method.But with the appearance of high-density information collection equipment and improvement of the request of the explanation precision, traditional explanation cannot reach the request of practical production. On the eliminating noise treatment to the original collection signal, traditional method seemed at loose ends. In the signal treatment domain, there occurs a new method, more advanced "digital microscope" --wavelet analysis. Wavelet analysis aims at the treatment of non-stationary signal. It is suitable to detect instant abnormal phenomenon carried in normal signal and exhibit its component. It is especially suitable for treating the dynamic and instant signal. In the TEM measuring depth method, we get the dynamic and instant signal. This gives us information that it is necessary to import wavelet analysis into the TEM measuring depth method to treat the signals. It can reach the purpose of improving precise.This thesis study the theory of TEM measuring depth method , wavelet analysis and differential conductance imaging principle of TEM measuring depth data , then the thesis brings forward the TEM fast imaging technology based on the wavelet analysis.On the plat of MATLAB wavelet function toolbox, import the wavelet analysis into the TEM. We give the eliminating noise treatment to the original data, and give the treatment of enhancement and smoothing to the imaged figures. Based on this and according to explain the principle of equivalent conductance plane method, point out the advantage that uses apparent portrait conductance parameter to explain the measuring depth data. At the same time, in order to improve the distinguish ability to electricity layer. On the basis of assuring physical meaning ofthe conductance and the parameter, use thrice spline insert number function to deal with the fieldwork data, realize the differential imaging. On the WINDOWS operation plat, develop the software to draw the differential conductance fig. The software has abundant function, friendly interphase, and simple operation. The fig can be exhibit the distribution form of the electricity interphase directly, vividly and clearly.The imaging treatment process can be divided to the following stages:1. Collect the original data, use the linear dimension wavelet bag (Symlets wavelet) in the wavelet function toolbox of MATLAB to give the original data eliminating noise treatment;2. Seek the B (t)fieldwork curve and the time derivative curve dBz(t)/dt from the voltage decrease data generalized from field current that eliminating noise treated by wavelet;3. Because limited by the sampling channel of transient electromagnetic measuring depth fieldwork curve (generally 20~40 channels), the smoothing degree of fieldwork curve is not very good, it make against the differential imaging treatment. In order to hold the continuous change characters of the curve and seek the voltage exactly, we use the thrice spline insert number function to reconstruct the fieldwork data;4. From the spline insert number can conclude the m corr...
|
PDF Full Text Request