微破裂向量扫描原理的研发进展

Development of vector scanning for microseismic

微破裂向量扫描原理是为了适应微震监测的目标特性、恶劣的地表监测环境、和对应用的一般监测要求,而逐步发展起来的.它不得不放弃记录要求较高的传统定位处理方法与可能使很多台站噪声极大的等距等角阵列,使用离散稀疏台网,处理分析完整的空间记录向量.在数学上,它计算各台记录对准各扫描点的向量间的相关性程度;在物理上,则反映了破裂释放能量的分布.选择安静处布设地震台网并在数据处理中去除和压制干扰信号以获得较小振幅的随机记录,是应用向量扫描技术的必要条件.这种条件应当数值化地由地震仪器、地震台网分布、监测环境、与去噪过程判定.一般情况下,为保证监测质量,它放弃振幅较小的纵波,而使用到达地表时携带能量较多的横波,并对扫描计算使用的台站记录附加以不同的权重;为提高性价比和使微震监测成为常规手段,在满足应用必要条件的基础上,它使用一个估计的最小扫描台站数,以及携行布设的最大台站数.利用相关性的概念,它可对速度模型引起的误差进行适度校正.微破裂向量扫描是专门针对微小破裂、三分量浅地表埋设观测、稀疏布设台阵、实时监测并4D处理解释、且考虑了微震多有剪切破裂特性的地震学监测方法;它扩展了传统定位方法的监测范围,能够在地表快速施工并"看到"微破裂,性价比高,可发展成为一种日常生产监测手段.

The vector scanning for microseismic has been gradually developed in last more than ten years based on the characteristics of microseismic,observation environment on surface, and ordinary requirements for any common method. It distributes a spars and scattered seismic network on surface and processes the recorded 3D vectors,instead of using arrays with equidistant seismometers and traditional relocation of hypocenters by picking wave arrivals. In mathematics,it detects the correlation level among the vectors by stacking them relative to any specified point underground,and in physics,it images the distribution of released seismic energy from the points. A necessary condition of applying the vector scanning is that all of records have to be random with small amplitudes and without significantly interfering signals. The vector scanning employs shear waves with greater amplitudes and more energy than preliminary wave for much better ratio of signal over noise,and puts different weights for stations to refine the scanning output. For better cost-effective and making it to be a routine method,a minimum station number is estimated. In addition,it properly correct the error of travel time from velocity model. The vector scanning is robust and cost-effective to detect microseismic with shear slips by using a scattered seismic array on surface and real-time processing3-component data. It may also be applied in other seismic detection ways for relatively farther regions away from the targets.