【摘要】 为实现对高密度、宽频带流动地震台阵地震检测能力的实时、不同深度评估,本研究采用"基于概率的完整性震级"(PMC)方法,以西昌流动地震台阵为例,对2013-01-13—2014-05-14期间平均的地震检测能力、不同震源深度检测能力,以及某一时刻的实时地震检测能力进行了评估.结果表明,PMC方法可识别地震观测资料处理中人为因素对地震检测能力的影响,不同震源深度下地震的检测能力存在差异,其中H=7.5km时,"网内"的完整性震级MP可达ML0.8,而在H=15.0km和25.0km时,"网内"的MP分别为ML1.0和ML1.4.在示例的2014-01-14时刻,非正常运行的台站造成地震检测能力的变化可被清晰识别出.此外,与MAXC和EMR等其它常用方法的对比表明,这些方法可能过高估计了地震台阵的检测能力.更多还原

【Abstract】 It is particularly important to obtain reliable and real-time assessments of earthquake detection capability of a small-aperture seismic array,which could be used to monitor its running state.Due to many obvious limitations such as the priori assumptions,real-time assessment unavailable and significant deviation to actual detection capability,the traditional methods including those based on G-R distribution are not suitable.Recently,a Probability-based Magnitude of Completeness(PMC)method was proposed to address these problems(Schorlemmer and Woessner,2008).Here we investigate the detection capabilities and recording completeness of the Xichang seismic array operated by the Institute of Geophysics,China Earthquake Administration(IGPCEA)applying the PMC method to demonstrate its feasibility under such condition.The PMC method was used to assess the earthquake detection capability of the Xichang seismic array in the period 2013-01-13—2014-05-14. We achieved probability distributions as functions of magnitude and distance for each station representing each station′s performance during thisperiod.Then,the detection probability for a given magnitude and probabilistic magnitude of completeness are computed by combining the single station detecting capabilities on a grid of points in the target area.The probability of detecting an event of given magnitude is the joint probability that the minimum number of triggering stations 4have detected it.We obtain the maps of probabilistic magnitude of completeness in the period or at one moment with different depth by searching minimal magnitude that exceeds the desired detection probability.In addition,we also compare the PMC method with two traditional methods MAXC and EMR by analyzing the differences between their results.The detection probability can significantly decreased with increasing depth,the magnitude completeness MP are ML0.8,ML1.0 and ML1.4 at depths of 7.5km,15.0km and 25 km respectively in the study area.From the snapshot of probabilistic magnitude of completeness at2014-01-01,a total of 7poorly running stations are identified,which could reduce the detection capability about 0.2magnitude units compared to the whole seismic array,and even could reach0.9magnitude units around some stations.Comparing to the other two traditional methods,The completeness magnitude from PMC method is larger about 0.5/0.6 magnitude units than the other two traditional methods.The PMC method are expected to be an accurate and reliable assessments method to access the event detection capability of a small-aperture seismic array with high density for avoiding the prior assumptions and providing a detailed description of detection probabilities over space,time,and magnitude.The Xichang seismic array shows very high event detectability.By using the PMC method,we can distinguish the effect of human factors in data processing and identify the poorly running stations nearly real-time.Furthermore,we also find the MAXC and EMR method may overestimate the detection capability comparing to the PMC method under the same assessment conditions.更多还原