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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(?)、(?)及绕射波 P_n.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.
The earthquakes recorded by Beijing Network from January 1, 1979 to June 30, 1980 were repositioned using HYPO81, a newly developed regional network locating program by WHKLee, G. Nelson and P. Ward. And compared with the results of the original station.The new locating program is characterized by: (1) each station can set its own layering speed model and allow the existence of low-speed layer; (2) a variety of weighted data; (3) Singular value decomposition least square method is used to iteratively solve the conditional equations; (4) Multi-quality evaluation of positioning results is given; (5) A variety of seismic facies to time data can be used. In order to reflect the horizontal structure of velocity structure in Beijing , Different horizontal stratification models are used for the mountainous area in the northwest, the plain in the southeast and the intermediate transition zone, respectively. The direct wave (?), (?) And the diffracted wave P_n are used for positioning. According to the given positioning in the HYPO81 program Quality standards, most of the earthquakes belong to Class C and Class D, indicating that it is necessary to encrypt the network and improve the accuracy of arrival readings.