摘要

Earthquake location is critical to the research on seismicity and disaster alleviation. The location problem can be solved by an intersection method which determines a hypocenter using its focal loci. The traditional intersection method is excellent in robustness and efficiency but deficient in location accuracy especially for hypocenter depth because it is based on homogeneous or laterally homogeneous media that are far from the real Earth. In order to eliminate the disadvantage of low accuracy, we have modified it in the suitability for 3-D complex velocity models. In the modified method, focal loci are not assumed to be spherical or hyperboloidal but exactly calculated with a minimum traveltime tree algorithm for tracing rays. The focal loci are constrained with observed arrival time differences so that the problem-of origin time is evaded. The hypocenter is located at the point that the focal loci most densely intersect, namely, the point with the minimal total residual of arrival time differences (RDT). The location uncertainty is qualitatively estimated by means of the distribution of nodes where RDT is smaller. The modified intersection method is verified with an earthquake in a complex model. The location tests in different cases including accurate model, perturbed model, noisy arrival times and partial observation show that the modified location method is practical for locating earthquakes in 3-D complex velocity models; integrated utilization of arrival time differences between and of P- and S- waves can remarkably improve the constraint on the hypocenter; using more focal loci can decrease the influence of random errors on earthquake location.

  • 出版日期2012-10
  • 单位中国地震局

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