华北地区地幔高导层埋藏深度的研究
INVESTIGATIONS OF THE DEEP ELECTRICAL CONDUCTIVITY BENEATH NORTHERN CHINA USING THE SPATIAL GRADIENT METHOD
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摘要: 本文用磁场梯度法研究华北地区地幔高导层的埋藏深度.所用的 Sq 资料取自六个台站:大连、昌黎、北京、红山、泰安和西安.计算 C 值时用二次曲面法.为了解释本文的 Creal-T 曲线和|Cimag|-T 曲线,至少要假设地下是四层结构.最底层的电导率非常高,埋藏深度约为690km.中间可能有一夹层,电导率约为0.325S/m,厚约24.5km,其顶面的埋藏深度约为334km.上述结果只是初步的,其真实性还需更多的研究、证实.本区与我国东南地区的深部结构比较,差异很大,因此也需要研究其间是怎样变化过渡的.Abstract: The spatial gradient method was used in estimating the buried depth of high conductivity layer beneath the region of northern China. Quiet daily magnetic variations recorded at six observatories, Dalian, Changli, Beijing, Hongshan, Taian and Xian, were analysed in this study. The second-order polynomial surface method was used for the calculation of value C. In order to interpret the results, Creal-T curve and |Cimag|-T curve, a four layer structure must be constructed at the least. The conductivity of the bottom layer is extremely high and its buried depth is about 690 km. A sandwiched high conductivity layer probably exists beneath this region, its conductivity 0.325 S/m, its thickness 24.5 km and its top at the depth of 334 km. It must be stressed that the results obtained here is preliminary, its reliability should be investigated and verified in further studies. The electrical structure revealed here is distinctly different from that of south-east China[1], therefore the whole feature of the change of the depth should also be investigated in the future.
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[1] 陈伯舫,中国东南部地慢高导层的埋藏深度,地震学报,8,172——178,1986.
[2] Lilley, F. E. M. and Sloane, M. N., On estimating electrical conductivity using gradient data from mag——netometer arrays, J. Geomag. Geoelectr., 28, 321——325, 1976.
[3] Woods,D.V. and Lilley, F. E. M., Geomagnetic induction in central Australia, J. Geomag. Geoelectr., 31,449——458,1979.
[4] Lilley, F. E. M. and Sloane, M. N., Ideal phase in estimating the spatial gradient of magnetic daily variations recorded by magnetometer arrays, J. Geomag. Ceoelectr., 33, 517——525, 1981.
[5] Lilley, F. E. M., Woods, D. V. and Sloane, M. N., Electrical conductivity from Australian magnetometer arrays using spatial gradient data, Phys. Earth Planet. Inter., 25, 202——209, 1981.
[6] Jones, A. G., Geomagnetic induction studies in Scandinavia, J. Geophys., 48, 181——194, 1980
[7] Beamish, D. and Jolinson, P. M., Difficulties in the application of magnetic field gradient analysis to induclion studies, Phys. Earth Planet. Inter., 28, 1——13, 1992.
[8] Lilley, F. E. M., Running waves and standing waves in geomagneting depth sounding, J. Geomag. Geoelectr, 27, 491——504, 1975.
[9] Berdichevsky, M. N., Fainberg, E. B., Rotanova, N. M., Smirnov, J. B. and Vanjan, L. L., Deep electro——magnetic investigations, Ann. Geophys., 32. 143——155, 1976.[1] 陈伯舫,中国东南部地慢高导层的埋藏深度,地震学报,8,172——178,1986.
[2] Lilley, F. E. M. and Sloane, M. N., On estimating electrical conductivity using gradient data from mag——netometer arrays, J. Geomag. Geoelectr., 28, 321——325, 1976.
[3] Woods,D.V. and Lilley, F. E. M., Geomagnetic induction in central Australia, J. Geomag. Geoelectr., 31,449——458,1979.
[4] Lilley, F. E. M. and Sloane, M. N., Ideal phase in estimating the spatial gradient of magnetic daily variations recorded by magnetometer arrays, J. Geomag. Ceoelectr., 33, 517——525, 1981.
[5] Lilley, F. E. M., Woods, D. V. and Sloane, M. N., Electrical conductivity from Australian magnetometer arrays using spatial gradient data, Phys. Earth Planet. Inter., 25, 202——209, 1981.
[6] Jones, A. G., Geomagnetic induction studies in Scandinavia, J. Geophys., 48, 181——194, 1980
[7] Beamish, D. and Jolinson, P. M., Difficulties in the application of magnetic field gradient analysis to induclion studies, Phys. Earth Planet. Inter., 28, 1——13, 1992.
[8] Lilley, F. E. M., Running waves and standing waves in geomagneting depth sounding, J. Geomag. Geoelectr, 27, 491——504, 1975.
[9] Berdichevsky, M. N., Fainberg, E. B., Rotanova, N. M., Smirnov, J. B. and Vanjan, L. L., Deep electro——magnetic investigations, Ann. Geophys., 32. 143——155, 1976.
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