北京地区莫霍界面形状的初步研究
A PRELIMINARY STUDY OF THE FORM OF THE MOHO-DISCONTINUITY IN THE BEIJING AREA
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摘要: 本文根据北京地震台网的人工爆破资料, 由莫霍界面的首波 Pn 的走时数据, 经过松散层校正和高程校正后, 采用改进的时间项法计算测点（台站和炮点）的时间项 t 和 Vpn, 最后引进弹性薄板模拟莫霍界面的形状, 得出北京地区莫霍界面深度等值线图.从该图可以明显看出全区趋势变化:西北部山区莫霍界面埋藏深, 东南平原莫霍界面埋藏浅, 向北西72方向, 向下倾斜约2, 全区平均深度约37公里.此外, 莫霍界面下的 Vpn较为稳定.Abstract: The contours of equal depths of the Mohorovicic Discontinuity underneath the Beijing area in North China are presented in this paper. They have been obtained on the basis of the Pn-travel time data of explosions recorded by the Beijing seismic network. The procedure of computation consists of three steps:1. Correction of the Pn-travel time for unconsolidated surface layers and also for station and shot elevations;2. Determination of the time-term of every observation point (stations and explosion sites) and Vpn, using the modified time-term method;3. Finally, simulation of the Moho-Discontinuity, by a thin elastic plate and then calculate the depths.It may be seen quite obviously from the depth contours a tendency that toward the northwest in the mountainous part of the area, the Moho-Discontinuity is deeper, but shallower toward the southeast. In the direction of 72 northwest, it dips about 2.The average depth of the Moho-Discontinuity of the entire area is about 37 km. Besides, below it, the value of Vpn become more stable.
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[15] 滕吉文等, 北京、天津、唐山、张家口地区的地壳结构, 地球物理学报, 22, 3, 218——236, 1979.[1] S. A. D. Bameford, Application of simulated data studies to crustal refraction seismology, B S. S. A., 61, 1013, 1971(a).
[2] S. A. D. Bameford, An interpretation of firm——arrival data from the continental margin refraction experiment, Geophy. J. R. A. S., 24, 213, 1971(b).
[3] S. A. D. Bameford, Refraction data in Western Germany—a time term interpretation, Z. Geoplays., 39, 907, 1973(a.).
[4] S. A. D. Bameford, An example of the iterative approach to time term analysis, Geophy, J. G. A. S., 31, 4, 365——372, 1973(b).
[5] S. A. D. Bameford, MOZaic time term analysis, Geophy. J. R. A. S., 44, 433——446, 1976.
[6] S. A. D. Bameford, An updated time term interpretation of Pn——data from quarry blasts and explosion in Western Germany, In: P. Giese et al., "Explosion Seismology in Central Europe", 215, 1976.
[7] M. Bath, An analysis of the time——term method in refraction seismology, Tectoxophysics, 51, 314, 155J169, 1978.
[8] A. M, Gardner, An cereal plane of mapping subsurface structure by refraction shooting, Geophysics, 4. 247——259, 1937.
[9] G. B. Morris, Delay——time function method and its application to lake Superior refraction data, J. G. R., 77, 2, 297, 1972.
[10] A. E. Scheidger, and P. L. Willmore, The use of a least square method for the interpretation of Iata from seismic surveys, Geophysics, 22, 1, 9——22, 1957.
[11] 王龙甫, 《弹性理论》, 328页, 科学出版社, 1979.
[12] 中国科学院地球物理研究所, 《近震分析》, 地震出版社, 1977.
[13] 中国科学院沈阳计算技术研究所, 《电子计算机常用算法》, 科学出版社, 1976.
[14] 中国科学院地球物理研究所, 晋中南地区地壳结构的初步研究, 地球物理学报, 17, 3, 116——199, 1974.
[15] 滕吉文等, 北京、天津、唐山、张家口地区的地壳结构, 地球物理学报, 22, 3, 218——236, 1979.
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