印度板块的北缘在哪里?

Where is the northern margin of the Indian plate?

通过对INDEPTHII在雅鲁藏布江南的2条南北向深地震反射剖面资料的进一步处理,观察到主喜马拉雅逆冲断裂带(MHT)形成的反射向北逐渐倾没于藏南地壳之下。这一反射一直可延伸至康马穹隆北、浪卡子南,在向北延伸的过程中,断裂带向北倾角逐渐加大,可以看到MHT反射最北端的反射同相轴向北倾斜的角度到达27°30'～29°,最深处的双程走时达到22.5s左右。根据深地震反射资料并结合大地电磁(MT)资料,提出印度板块在雅鲁藏布江南30～40km(大约28°50'N)处沿MHT俯冲到了藏南的地壳之下,即在地壳范围内印度板块的最北部边缘位于雅鲁藏布江南30～40km处。

The mid-crustal reflection formed by the Main Himalayan Thrust （MHT）is interpreted to be underthrust gradually northward beneath the crust of southern Tibet by intensive processing of the data of two N-S-trending deep seismic reflection profiles on the southern side of the Yarlung Zangbo River obtained by Project INDEPTH II in 1993. This reflection may extend northward beneath north of the Kangmar dome and south of Langkazi. During its northward extension, the dip angle of the thrust increases progressively. The north-dip angle of the reflection line-up at the northernmost end of the MHT reflection reaches 27°30＇-29° and the two-way travel time at the deepest part is up to -22.5 s. According to the deep seismic reflection data, combined with magnetotelluric （iT） data, this paper proposes that the Indian plate has been subducted along the MHT beneath the crust of southern Tibet at a site 30-40 km south of the Yarlung Zangbo River （-28°50＇N）, i.e. the northernmost portion of the Indian plate within the crustal scope lies 30-40 km south of the Yarlung Zangbo River.