岷江上游地质灾害发育强度与规律分析

ANALYSIS OF INTENSITY AND REGULARITY OF GEOHAZARDS IN UPPER REACHES OF MINJIANG RIVER

岷江上游地区地质环境条件复杂、脆弱,以滑坡、崩塌、泥石流为主的地质灾害数量多、规模大、危害严重,汶川地震又引发了大量崩滑地质灾害。本文根据汶川地震前和汶川地震地质灾害调查、排查等成果,采用GIS分析和编程计算相结合的方法,选取适宜的控制点间距、搜索半径编制了岷江上游汶川地震前、汶川地震地质灾害点密度、面积密度和体积密度图,提出利用点密度、面积密度和体积密度来综合评价地质灾害的发育强度,从弱到强划分为8个等级。分析认为,岷江上游地区地质灾害发育强度高,汶川地震前地质灾害累积发育强度达最高8级极端活动,汶川地震诱发崩滑地质灾害发育强度最高为7级极强活动,且2~6级区面积较大。岷江上游地区历史强震、暴雨等极端事件多发是地质灾害累积发育强度高的主要原因,而汶川地震单次事件引发的地质灾害发育强度总体较高,并主要沿龙门山断裂带、南部河谷区分布。

The geological environment is complex and fragile in the upper reaches of Minjiang River.Geological hazards mainly landslides,collapses and debris flows in these areas are characterized by large quantity,large scale and serious harm.Especially,many geological hazards were triggered by the Wenchuan Earthquake.This study is based on the geological survey reports before and after the Wenchuan Earthquake,and uses GIS technology and programming computing technology.It makes the point density map,surface density map and volume density map of the upper reaches of Minjiang River with suitable control-points space and searching radius.It is proposed that geohazard intensity can be divided into 8 grades from weak to strong using the point density map,surface density map and volume density map.So,its analysis shows that the geohazard intensity is high in the upper reaches of Minjiang River.The accumulative geohazard intensity before the Wenchuan Earthquake is up to the highest 8^th grade(extremely intense activity).The highest geohazard intensity triggered by Wenchuan Earthquake is the 7^th grade,and most are the 2^th to the 6^th.The main reason of the high cumulative geohazard intensity in the upper reaches of Minjiang River is the frequent occurrence of extreme events such as historical strong earthquake and rainstorms.Generally,the geohazard intensity triggered by the Wenchuan Earthquake is high,and mainly along the Longmen Mountain fault zone and the southern valley area.