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2002—2005年完成了穿越喜马拉雅山的宽频地震探测,采用了沿剖面紧密排列的台站布置并获得了近震中的反射波资料,这对地壳和岩石圈内部速度界面的研究有重要意义。地震数据及研究结果表明,青藏高原的地震主要发生于上地壳范围内,高原莫霍面反射波的纵波 PmP 与横波 SmS 波至清晰可辨且有很强的能量,在跨越雅鲁藏布江时 PmP 和 SmS 均发生了错动,表现为北深南浅。在改则至鲁谷沿线所记录到的发生在拉萨地块的 Fw21事件的地震数据中,拉萨地块内部的莫霍面反射波,尤其是 SmS 波至非常清晰连续,地壳纵波平均速度为 V_p=6.3km/s,表明拉萨地块内部 Moho 面平坦、连续,不存在突起与错位。在此 Moho 面之前出现壳内较强反射界面,埋深45km 可能正是下地壳的顶界面。P208事件中 PmP 和 SmS 均清晰可见,然而在距震中450km 及其以远地段存在两个清晰的震相 P_(LT)及 S_(LT),并且其能量很强,可能是位于160km 深处的岩石圈底界面的反映。根据对近震资料的分析研究,本文建立了该地区的地壳上地幔的结构模型。
The broadband seismic exploration across the Himalayas was completed in 2002-2005. The station arrangement along the section and the reflections of near-earthquakes were obtained. This is of great significance for the study of the velocity interface within the crust and lithosphere. Seismic data and research results show that the earthquakes in the Tibetan Plateau occur mainly in the upper crust. The PmP and SmS waves reflected by the Moho on the plateau are clearly discernible and have strong energy. When crossing the Yarlung Zangbo River, PmP and SmS All occurred in the wrong move, the performance of North Shennan shallow. In the seismic data of the Fw21 event that occurred in the Lhasa block from the Lhasa block to the Lugu block, the Moho waves in the Lhasa block, especially the SmS waves, are very clear and continuous with an average velocity of the longitudinal crust of V_p = 6.3km / s, which indicates that the Moho surface in Lhasa block is flat and continuous, and there is no protrusion and dislocation. Before this Moho surface, there appeared a strong reflection interface in the shell. The depth of 45km may be the top interface of the lower crust. Both PmP and SmS are clearly visible in the P208 event, however, there are two clear phases P LT and LT LT at a distance of 450 km and beyond from the epicenter, and their energy is very strong, probably at a depth of 160 km Reflection of the lithosphere bottom interface. According to the analysis of near-Earthquake data, this paper established the structural model of the upper crust in the region.