| 从宽角地震数据得出的特提斯喜马拉雅南部的速度结构 |
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| 关键词:wide-angle seismic data main Himalayan thrust(MHT) |
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| Structural Elements of the Southern Tethyan Himalaya Crust from Wide Angle Seismic Data |
| A deep seismic common-mid-point (CMP) profile, shot across the southern margin of the Tethyan Himalaya as the first stage of Project INDEPTH (International Deep Profiling of Tibet and the Himalaya), imaged the top (Main Himalayan Thrust or MHT) and bottom (Moho) of the indian continental crust underthrusting the Himalaya. We used portable seismographs to record the CMP-profile shots at a wide range of offsets, up to 155km. Our shortoffset data corroborate the CMP-profile data while our large offsets data are dominated by a band of reflectivity. We interpret the bright onset of this reflective band as the South Tibetan Detachment (STD) and a phase at the end of the reflective band as the MHT.We used the CMP-profile first-break data to model the uppermost 2km in detail. The depth of young extensional basins of the Yadong rift system along the CMP-profile was constrained to a masximum of 2km, yielding a throw of 4. 6km across the eastern flank of the rift and a gross estimate of c. 1. 5 % east-west, normal faulting, extension in the Tethyan Himalaya. The wideangle data were used to construct a crustal seismic-velocity model down to the MHT. The STD reflector dips 13°N from a depth of about 6km beneath the surface under the south end of the CMP profile to a depth of 22km, them flattens to a dip of only 5° N. Thus our observations suggest that the STD is a deep-rooted basement fault. For the MHT we observe a dip of 7. 5°NNE from 20km depth below sea level at the crest of the High Himalaya to 36km below sea level (40km beneath the surface) at a distance of about 70km south of the indus-Yarlung suture (IYS). We suggest that indian crust may underthrust the surface expression of the IYS. but probably does not do so as an intact plate. |
| Yizhaq Makovsky,S. L. Klemperer,HUANG Li-yan,LU De-yuan.1996.Structural Elements of the Southern Tethyan Himalaya Crust from Wide Angle Seismic Data[J].Acta Geoscientica Sinica,17(2):153-164. |
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