| Two-step interface and velocity inversion—— Study o e of the Tangshan seismic region |
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| 作者姓名： | XIAO LING LAI XIAN KANG ZHANG XU YAO ZHENG Research
Center of Exploration Geophysics China Seismological Bureau Zhengzhou China |
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| 作者单位： | XIAO LING LAI XIAN KANG ZHANG XU YAO ZHENG Research
Center of Exploration Geophysics，China Seismological Bureau，Zhengzhou 450003，China |
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| 摘 要： | ｎｔｒｏｄｕｃｔｉｏｎＩｎｒｅｃｅｎｔｔｅｎｙｅａｒｓ，ｒｅｓｅａｒｃｈｅｓｏｎｔｈｅ３Ｄｃｒｕｓｔａｌｓｔｒｕｃｔｕｒｅａｎｄｔｅｃｔｏｎｉｃｓｈａｖｅｂｅｅｎｐａｉｄｍｏｒｅａｎｄｍｏｒｅａｔｅｎｔｉｏｎ，ｓｔｕｄｉｅｓｏｆｒｅｌｅｖａｎｔｍｅ...
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Two step interface and velocity inversion Study of 3 D fine structure of the Tangshan
seismic re gion |
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| XIAO LING LAI XIAN KANG ZHANG XU YAO ZHENG Research
Center of Exploration Geophysics,China Seismological Bureau,Zhengzhou ,China.Two step interface and velocity inversion Study of 3 D fine structure of the Tangshan
seismic re gion[J].Acta Seismologica Sinica(English Edition),1998(6). |
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| Authors: | XIAO LING LAI XIAN KANG ZHANG XU YAO ZHENG Research
Center of Exploration Geophysics China Seismological Bureau Zhengzhou China |
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| Institution: | XIAO LING LAI XIAN KANG ZHANG XU YAO ZHENG Research
Center of Exploration Geophysics,China Seismological Bureau,Zhengzhou 450003,China |
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| Abstract: | This paper studies the computation method of two step inversion of interface and
velocity in a region. The 3 D interface is described by a segmented incomplete polynomial;
while the reconstruction of 3 D velocity is accomplished by the principle of least squares in
functional space. The computation is carried out in two steps. The first step is to inverse the
shape of 3 D interface; while the second step is to do 3 D velocity inversion by distributing the
remaining residual errors of travel time in accordance with their weights. The data of seismic
sounding in the Tangshan Luanxian seismic region are processed, from which the 3 D
structural form in depth of the Tangshan seismic region and the 3 D velocity distribution in the
crust below the Tangshan Luanxian seismic region are obtained. The result shows that the
deep 3 D structure in the Tangshan seismic region trends NE on the whole and the structure
sandwiched between the NE trending Fengtai Yejituo fault and the NE trending Tangshan fault
is an uplifted zone of the Moho. In the 3 D velocity structure of middle lower crust below that
region, there is an obvious belt of low velocity anomaly to exist along the NE trending
Tangshan fault, the position of which tallies with that of the Tangshan seismicity belt. The larger
block of low velocity anomaly near Shaheyi corresponds to a denser earthquake distribution. In
that region, there is an NW trending belt of high velocity anomaly, probably a buried fault
zone. The lower crust below the epicentral region of the Tangshan M S=7.8 earthquake is a
place where the NE trending belt of low velocity anomaly meets the NW trending belt of high
velocity anomaly. The two sets of structures had played an important role in controlling the
preparation and occurrence of the M S=7.8 Tangshan earthquake. |
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| Keywords: | two step interface and velocity inversion 3 D velocity pattern of crust below Tangshan seismic region seismicity zone |
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