多重模型地震定位程序及其在北京台网的应用

AN EARTHQUAKE LOCATION PROGRAM WITH MULTIPLE VELOCITY MODEL AND ITS APPLICATION IN THE BEIJING SEISMIC NETWORK

  • 摘要: 利用 W. H. K. Lee、G. Nelson、P. Ward 和本文作者新发展的区域台网地震定位程序HYPO81对北京台网1979年1月1日至1980年6月30日记录的地震作了重新定位处理,并与原台网测定结果进行了比较.新定位程序的特点是:(1)各台站可设定自己的分层速度模型且允许存在低速层;(2)对数据作了多种加权;(3)迭代求解条件方程时采用奇异值分解最小二乘法;(4)对定位结果给出多方面质量评价;(5)可使用多种震相到时数据.为了反映北京地区速度结构的横向差异,对西北部山区、东南部平原和中间过渡区分别使用不同的水平分层模型.定位时使用了直达波P、S及绕射波 Pn.根据 HYPO81程序中给定的定位质量标准,大部分地震属于 C 类和 D 类,说明加密台网和提高到时读数精度是十分必要的.

     

    Abstract: With a new earthquake location program HYPO81, developed by W.H. K. Lee, G. Nelson, P. Ward, and the author, the earthquakes recorded by the Beijing Seismic Network from Jan. 1, 1979 through June 30, 1980 are relocated and the results are compared with the earlier reported ones. The features of the new location program can be summarized as: (1) different multi-layered velocity models can be used for different group of stations and low velocity layers are allowed to be included in the models; (2) several kinds of weightings are used; (3) single value decomposition technique is used in the least-squares iterations; (4) the quality of the results is evaluated in several ways; and (5) different kinds of phase data can be used.In order to reflect the lateral variation of the velocity structure in Beijing area, three different multilayered velocity models are used for the northwestern mountain area, the southeastern plain, and the area between them, respectivety. In locating the earthquakes, direct P, refrected P, and direct S arrival data are used. According to the quality criteria in HYP081, over three quarters of the events relocated fall into the catagories of quality C and D, indicating the necessity of increasing stations in the network and improving the accuracy of the phase data.

     

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