Improvements of the Maximum Intersection Method for 3D Absolute Earthquake Locations
Improvements of the Maximum Intersection Method for 3D Absolute Earthquake Locations
复制标题
3D绝对地震位置最大交会法的改进
DOI：
--
复制
发表时间：
2012
期刊：
影响因子：
--
通讯作者：
S. Gautier
中科院分区：
文献类型：
--
作者：
T. Theunissen;Y. Font;S. Lallemand;S. Gautier
一种Wepresentanimprovementofthemaximumintersection(MAXI)method，其中绝对地震位置由双曲线等时差分体的最大交集数来定义(一个等差体被描述为满足两个台站之间到达时间差的所有网格节点，公差值称为TERR)。这种3D技术很好地适应了强异质环境(仅avoidsthedepthversusorigin-timetrade-off(evenusingP到达环境)，并客观地过滤了可能的错误到达时间。改进措施包括在TERR参数上引入迭代多尺度方法，并进行网格离散化以改进初步解(多重网格算法)。通过根据每个站点的EDT交叉口数量而不是旅行时间残留量进行统计分析，加强了异常值清理过程。处理台湾近海三维地震configurationofthesouthernmostRyukyusubductionzone，计算的两系列合成到达时间，使我们能够(1)确认最大稳健性，即使在到达时间受到严重干扰或方位覆盖范围大大减少的情况下，以及(2)表明，通过限制起始时间和深度之间的权衡以及震中位置和深度之间的权衡，最大到达时间受到错误速度模型的影响小于最小化旅行时间残差的技术。总之，我们应用最大值方法在先验的三维P-速度模型中定位了台湾中央气象局(CWB)和日本气象厅(JMA)联合台网(1991-2008年)记录的地震。震源确定基于最大置信度因子，沿已知构造特征的地震丛集证明了震源确定的准确性。
Wepresentanimprovementofthemaximumintersection(MAXI)method in which absolute earthquake location is defined by the maximum intersection number of hyperbolic equal differential time (EDT) volumes (one EDT volume being described as all grid nodes satisfying the arrival-time differences between two stations, a tolerance value known as TERR). This 3D technique is well adapted to a strongly heterogeneousenvironment,avoidsthedepthversusorigin-timetrade-off(evenusingP arrivals alone), and objectively filters possible erroneous arrival times. Improvements consist of introducing an iterative multiscale approach on the TERR parameter and conducting a hierarchy of grid discretization to refine the preliminary solution (multigrid algorithm). The outlier cleaning process is strengthened by conducting statistical analyses based on the number of EDT volume intersections per station, rather than on travel-time residues. Processing two series of synthetic arrival times computed in the 3D seismological configurationofthesouthernmostRyukyusubductionzone,offshoreTaiwan,allowsus to (1) confirm MAXI robustness, even when arrival times are highly disturbed or azimuthal coverage largely reduced, and (2) show that MAXI, by limiting trade-offs between origin time and depth and between epicentral position and depth, is less af- fected by a wrong velocity model than a technique that minimizes travel-time residues. To conclude, we apply the MAXI method to locate earthquakes recorded by the combined Central Weather Bureau of Taiwan (CWB) and the Japanese Meteorological Agency (JMA) networks (1991-2008) within a georealistic a priori 3D P-velocity model. Hypocenter determinations are selected based on MAXI confidence factors, and earthquake clustering along well-known tectonic features witnesses hypocenter determination accuracy.