摘要
震源定位是微地震监测技术要解决的主要问题.目前,井下微地震监测多采用走时拟合法计算震源位置.常规方法受到环境噪声、初至拾取误差、速度模型误差等因素的影响,定位结果存在一定误差.为了提高定位精度,本文提出了一种改进的基于网格搜索的微地震震源定位方法.本文方法根据P波的偏振特征参数计算概率密度函数求取震源方位角,并采用改进的目标函数和搜索算法计算震源的径向距离和深度.模型数据和实际资料的处理结果表明,本文方法具有较强的抗噪性,计算得到的震源方位角更加接近真实值;与常规目标函数相比,本文方法采用的目标函数具有更好的收敛性,其定位结果受初至拾取误差和速度模型误差的影响更小;本文提出的搜索算法能够消除由于错误拾取造成的观测到时中的异常值对定位结果的影响.
Microseismic source location is the core problem for microseismic monitoring. As for the downhole monitoring cases, microseismic sources are normally located by minimizing the misfit between the observed and predicted travel times. Conventional method tends to be affected by many factors, such as ambient noises, arrival picking errors and velocity model errors, therefore produces results with larger discrepancies. We propose an improved method for microseismic source location. This method is based on grid search algorithm and some improvements are incorporated to enhance its location accuracy. The improvements include the use of a probability distribution function, which is calculated using the polarization attributes of P-wave, to estimate the source azimuth and the adoption of a new objective function and an improved search algorithm to find the optimal radial distance and depth of the source. The results from testing the proposed method on synthetic and real datasets have shown that this method has a strong noise resistibility and can produce more accurate estimate of the source azimuth. The new objective function shows better convergence than the traditional ones and its location results are less affected by the errors in the arrival times and velocity models. The improved search algorithm can mitigate the impact of erroneous picks on the location results.
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2017年第1期293-304,共12页
Chinese Journal of Geophysics
基金
中央财政拨款地质调查项目(DD20160217-3)资助
关键词
微地震
震源定位
偏振特征
目标函数
网格搜索
Microseismic
Source location
Polarization attribute
Objective function
Grid search
