龙门山典型河流形态变化的潜在地震因素分析

以岷江支流白沙河和涪江支流湔江为例，探讨了2008年汶川地震之后龙门山地区河流形态的变化及其可能的长期构造地貌效应。研究表明，2008年汶川地震地表破裂带穿越河流形成裂点（跌水），地震触发的山体滑坡、泥石流堵塞河道形成堰塞湖，致使河流形态及河流水动力条件随之发生变化。河流同震裂点在震后迅速消失，部分河段出现“裁弯取直”的趋势，这可能与河流中激增的沉积通量有关。随着周期性大地震的复发，河流的沉积-侵蚀过程会不断改变，伴随着震间活动断裂持续的构造变形，龙门山河流形态可能会发生快速变化。 

POSSIBLE SEISMIC CONTROL ON RIVER CHANNEL CHANGE IN THE LONGMENSHAN MOUNTAIN

The 2008 M_w7.9 Wenchuan earthquake induced a large quantity of landslides whose materials entered the river channels. In some channel reach the seismic surface ruptures caused the co-seismic knick points across the channel of the Longmenshan Mountain. The river morphology and hydrodynamic condition may be changed. The field investigations show that co-seismic knick points disappeared rapidly, and meander cut-off would potentially occur in the near future. This suggests that the temporal increase in sediment input will not reduce the long-term fluvial transport capacity. A few years later, the rivers will reach a new state of eroion-transport-deposition. It is concluded that the seismic erosion events (landslide) and local hydrometerological conditions (heavy rainfall and flash flood) exert significant controls on the river channel change in the Longmenshan Mountain.