A Study on Automatic Velocity Analysis in Seismic Exploration

• Main Author: 蕭旭宏
• Other Authors: 孫鎮球
• Format: Others
• Language: zh-TW
• Published: 1998
• Online Access: http://ndltd.ncl.edu.tw/handle/70793655694151159761

碩士 === 國立成功大學 === 地球科學研究所 === 87 === 　　This is a research on the automation of normal moveout(NMO) velocity analysis. The methodology is to quantify the velocitypicking criterion such that an electronic computer is able to substitute human force in the velocity picking. The algorithm is proceeded in common depth point(CDP) gather on which testing NMO in implemented with various possible velocities. The NMOed CDP gather is divided into windows along the time axis to encompass the energy of a single reflection. Cross-correlation between the energy in two neighbor traces is computed within each window. Maximum cross-correlation then marks the time shift of the arrival time of the reflection. The relative arrival time of a reflection at each trace can ten be obtained by accumulating the time shift on neighboring traces. With the relative arrival time quantified this way, the velocity picking can then be implemented by finding the velocity that generates the least-slope(NMOed) reflection. 　　Testing of this algorithm is implemented against synthetic seismogram as well as real field seismic data for shallow seismic exploration purpose, with peak frequency of 90 Hz. The result is satisfactory in the case of low stretching and low noise. Otherwise, the result is not quite satisfactory. Therefore, more efforts is needed to reduce the stretching and noise level before this algorithm can be of practical usage.