Locating events with a sparse network of regional arrays
Locating events with a sparse network of regional arrays
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发表时间：
1988-04
影响因子：
3
通讯作者：
S. Bratt;T. Bache
中科院分区：
文献类型：
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作者：
S. Bratt;T. Bache
本文描述了一种利用包含阵列和单元件地震仪的网络自动定位区域地震事件的方法。该方法将后向估计、到达时间数据和相关不确定性合并到最小二乘逆定位算法中。该公式本质上是Jordan和Sverdrup的公式，扩展到包括方位角数据。该技术允许使用关于数据不确定性的先验和后验信息来计算用于位置估计的置信度椭球。这对于根据较少的数据获得解的真实置信度椭球是很重要的。它还允许随着特定领域内事件的经验积累，对置信度椭球计算进行改进。像挪威的NORESS这样的小天线阵可以准确估计区域震相的后方位角。这些方位数据对少数台站探测到的事件的位置提供了很强的约束。约束的强度取决于几何体，在某些情况下，方位角数据与到达时间数据一样重要。对于包含两个阵列的网络，给出了说明这一点的综合例子。提供了挪威南部NORESS阵列和芬兰赫尔辛基附近FINESA阵列的实际数据，以演示定位技术的使用。所研究的大多数事件都是地雷爆炸，有非常准确的、独立的位置。将单阵和双阵的位置及其置信度椭圆与这些独立的位置进行比较，初步验证了我们对(依赖于信号的)先验到达时间和方位角方差的估计，并证明了我们对区域阵列稀疏网络的定位过程的有效性。
Abstract An automated procedure for locating regional seismic events with a network including arrays and single element seismometers is described. The method incorporates backazimuth estimates, arrival-time data, and associated uncertainties into a least-squares-inverse location algorithm. The formulation is essentially that of Jordan and Sverdrup extended to incorporate azimuth data. This technique allows the use of both a priori and a posteriori information about data uncertainties to compute confidence ellipsoids for location estimates. This is important for obtaining realistic confidence ellipsoids for solutions based on few data. It also permits a refinement of the confidence ellipsoid calculations as experience accumulates for events in a particular area. Small arrays like NORESS in Norway provide accurate estimates for the backazimuth of regional phases. These azimuth data provide a strong constraint on the location of events detected by a small number of stations. The strength of the constraint depends on the geometry, and in some situations azimuth data are as important as arrival-time data. Synthetic examples illustrating this are given for a network including two arrays. Actual data from the NORESS array in southern Norway and the FINESA array near Helsinki, Finland, are presented to demonstrate the use of the location technique. Most of the events studied are mine blasts for which there are highly accurate, independent locations. Comparing one-array and two-array locations and their confidence ellipses with these independent locations provides a preliminary validation of our estimates of the (signal-dependent) a priori arrival-time and azimuth variances, and demonstrates the effectiveness of our location procedure for a sparse network of regional arrays.