微震震源定位可靠性综合评价模型

A comprehensive evaluation model for microseismic source location reliability

微震震源定位受定位方法、微震台网布置、波速模型和到时等因素的影响,单一指标很难对震源定位结果进行全面评价,因此提出了一种包含事件残差指标、敏感度指标和触发序列指标的震源定位可靠性综合评价方法。采用改进的L1范数统计准则计算微震事件残差,并根据事件残差的取值范围确定了可评价震源定位精度的事件残差指标;根据给定波速误差后震源定位结果之间差值的大小,提出了敏感度指标,主要对定位稳定性进行评价;基于观测触发序列和计算触发序列匹配度,并结合微震台网布置和有效传感器数量,提出了触发序列指标,该指标能够同时反映定位精度和稳定性;综合以上3种评价指标,建立了微震震源定位可靠性综合评价模型。通过现场试验验证,表明该模型能够对定位精度和稳定性进行全面有效评价,评价结果可以作为衡量微震监测系统定位可靠性的实用依据。

Microseismic source location is mainly affected by source location methods, microseismic network, velocity model and arrival times, therefore, a single index may not get a comprehensive evaluation of the source location re- sults. This paper presented a comprehensive evaluation model, which contains event residual index, sensitivity index and hit sequence index, to evaluate the microseismic source location reliability. First, the improved L1 norm statistical standard for source location was used to calculate the event residual. According to the ranges of the event residuals, the event residual index and its rating standard were determined, which can estimate the source location accuracy. Second, the stability of a solution was analyzed by the sensitivity index which was defined as the distance between a located source and its associated position by assuming different velocities. Third, based on the matching degree of the observed hit sequence and the calculated hit sequence,together with the microseismic network and the number of microseismic sensors, the hit sequence index was put forward. It can reflect not only the location accuracy but also the solution sta- bility. Finally, the comprehensive evaluation model was built up by considering the above three evaluation indexes. In the end, the comprehensive evaluation model was checked by the field test. The results show that this model can evalu- ate the source location accuracy and stability comprehensively and effectively. The result of assessment can be used as a practical basis for the source location reliability of microseismic monitoring systems.