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首页> 外文期刊>Geophysical Research Letters >Crustal structure across Longmenshan fault belt from passive sourceseismic profiling
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Crustal structure across Longmenshan fault belt from passive sourceseismic profiling

机译:基于被动震源剖面的龙门山断裂带地壳结构

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We analyse receiver functions from 29 broad-bandseismographs along a 380-km profile across theLongmenshan(LMS)fault belt to determine crustalstructure beneath the east Tibetan margin and Sichuanbasin. The Moho deepens from about 50 km underSongpan-Ganzi in east Tibet to about 60 km beneath theLMS and then shallowstoabout35kmunderthewesternSichuan basin.The average crustal Vp/Vs ratios vary inthe range 1.75-1.88 under Songpan–Ganzi in east Tibet,1.8-2.0 under the LMS,and decrease systematicallyacross the.NW part of the Sichuan basin to less than 1.70.A negative phase arrival above the Moho under Songpan-Ganzi and Sichuan basin is interpreted as a PS conversionfrom the top of a low-velocity layer in the lower crust.Thevery high crustal Vp/Vs ratio and negative polarity PSconversion at the top of lower crust in east Tibet are inferredto be seismic signatures of a low-viscosity channel in theeastern margin of the Tibetan plateau.The lateral variationof Moho topography,crustal Vp/Vs ratio and negativepolarity PS conversion at the top of the lower crust alongthe profile seem consistent with a model of lower crust flowor tectonic escape.
机译:我们沿着龙门山断裂带的380公里剖面分析了29台宽带地震仪的接收器功能,以确定藏东边缘和四川盆地下方的地壳结构。莫霍面深度从藏东松潘-甘孜下约50公里延伸到LMS下约60公里,然后在四川盆地西部西下约35公里处变浅。地壳的Vp / Vs之比在藏东松潘-甘孜下为1.75-1.88,在藏东以下为1.8-2.0 LMS,并在整个四川盆地西北部系统地减少到1.70以下。松潘-甘孜和四川盆地下方莫霍面上方的负相到达被解释为是下地壳低速层顶部的PS转换。推断藏东东部下地壳顶部的地壳Vp / Vs比率很高,负PS转换是青藏高原东缘低粘度通道的地震信号.Moho地形的横向变化,地壳Vp / Vs地壳下部剖面顶部的比率和负极性PS转换似乎与下部地壳流或构造逃逸的模型一致。

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