龙门山逆断裂带中段的构造地貌学研究

TECTONIC GEOMORPHOLOGY OF THE CENTRAL SEGMENT OF THE LONGMENSHAN THRUST BELT, WESTERN SICHUAN,SOUTHWESTERN CHINA

龙门山逆断裂带中段由３条主要的逆断裂带组成，根据构造地貌学特征和地震活动性推测，其第四纪活动性自南西向北东方向递减，表现出明显的分段性。其中灌县－江油断裂控制了山地与平原或山地与丘陵区的分界以及第四系的厚度，根据这一特征可知该断裂的活动性自南向北，在大邑、灌县和彭县一带最强，绵竹次之，安县至江油最弱。断裂活动的分段性可能受龙门山北部南北向岷山隆起的控制。由于新构造活动分布在３条断裂上，所以区内以６级以下的中小地震活动为主。

The NE-trending central segment of the Longmenshan thrust belt is composed of 3 majorthrust or reverse faults. Geomorphic evidence and earthquake activity indicate that Quaternaryactivity is stronger on the southwest and weaker on the northeast along the central segment ofthe Longmenshan thrust belt. The segmentation of faulting is probably produced by the activityon the NS-trending Minshan uplift on the north of the Longmenshan thrust belt. Because defor-mation is dispersed on 3 faults, only moderate（M≤6）earthquakes have occurred along the cen-tral segment of the Longmenshan thrust belt.