越南红河断裂带的深部结构、现今动力学与地震活动

展示了越南红河断裂带（RRFZ）的地壳结构，断裂与地震活动表现的主要特征，研究结果表明：（1）红河断裂带的莫霍面的深度在22－24km与30－32km之间变动，倾向北西；与之相反，此处地壳的结晶面则倾向北东且其在红河新生代拗陷的中部的深度只有8－9km。（2）在现代，红河断裂带受来自燕东方向的挤压影响，在此断裂带的北东部分明显有强烈的隆升和地震活动。（3）地震震中主要分布于7－20km的深度，大多数在10－16km的范围内。震中最小深度与最大震级之间的相关函数lgHmin=0.25Ms-0.30。（4）红河断裂带的主要孕震断裂为Lo河，Vinh Ninh,Chay河，红河，Fansipan及BinhLuc等断裂，在红河断裂带地区，最强的地震可达Mmax=5.6-6.0级，而最强烈的地震活动带在Chay河与红河一带地区。（5）红河断裂带地区区域地震危险性最高的可能在LunYen-YenBai和VietTri-Hanoi地区。

DEEP STRUCTURE, RECENT DYNAMICS AND SEISMIC ACTIVITY IN RED RIVER FAULT ZONE IN VIET NAM

The main characteristics of the crustal structure, the faults and the manifestation of seismic activities in the Red River Fault Zone (RRFZ) are presented in this paper. The results of study show that:(1) The depth of the Moho discontinuity of the RRFZ varies from 22-24 km to 30-32 km with northwestward dipping tendency. On the contrary, crystal surface of the earth's crust has northeastward dipping tendency and its depth reached about 8-9 km in the central part of Red River Cenozoic depression.(2) At present, the RRFZ is affected by compression from northeast direction. Strong uplift and high seismic activity in the northeast part of the fault zone are shown here clearly.(3) Earthquake epicenters are mainly distributed in the depths of about 7-20 km,but the most in the range of 10-16 km.The correlation function between minimal depth of hypocenters Hmin and maximum magnitudes(Mmax)of the earthquake is as follows.Lg Hmin=0.25Ms-0.30(4) The main seismogenic faults of RRFZ consist of: Lo River, Vinh Ninh, Chay River, Red River, Fansipan and Binh Luc.The strongest earthquakes which will occur within RRFZ may be Mmax=5.5-6.0 and it seems that Chay River and Red River have the strongest seismic activity.(5) The highest risk of seismic activity in the RRFZ may be in Luc Yen-Yen Bai and Viet Tri-Hanoi areas.