典型地区地震山地灾害分布对环境本底因素响应机制研究--以绵竹市为例

Research on Responsive Mechanism Between Earthquake-induced Mountain Hazards and Environmental Background in Typical Region of Wenchuan Earthquake:A Case Study of Mianzhu County

通过对汶川地震灾区的调查和遥感解译,详细分析了绵竹市地震山地灾害的特点,在G IS平台上对297个典型灾害点的环境本底因素进行分析,研究灾害分布对地震烈度、距断裂带距离、岩性、高程、河流、坡度和坡向的响应机制。得出以下结论：1）距中央断裂的距离是汶川大地震山地灾害分布规律的主导因素,灾害在距中央断裂0～8 km范围内响应明显,上盘发育程度明显高于下盘,下盘灾害点分布的变化规律受前山断裂破裂的影响;2）山地灾害在硬质岩层中最为发育,灾害发育密度随坡度的增加而增大;3）地形和河流共同制约着坡体卸荷和地震能量的释放,山地灾害对海拔较高、坡度陡峭、切割强烈和河网密度大的区域响应更为明显;4）当区域地势变化方向和坡向与地震断裂破裂方向一致时,有利于地震能量的传播,灾害更容易发生。

297 earthquake-induced mountain hazards of Mianzhu county were obtained with field investigation and interpretation of remote-sensing images,GIS technique was used to finish the statistical data which were about the relationship between distribution of hazards and environmental factors,including distance from seismogenic faults,lithology,altitude,river,slope and aspect of slope.And research on the responsive mechanism between the distribution of hazards and factors.The main results of the study can be summarized as follows.1）The distance from seismogenic faults was the leading factor for the distribution of earthquake-induced mountain hazards.The high density of earthquake-induced mountain hazards was distributed within 8 km from seismogenic faults,and the density in hangingwall of seismogenic faults was obviously higher than that in footwall.The density of hazards in the footwall of seismogenic faults decreased within 10 km and increased from 10 km to 14 km and decreased again from 14 km to 16 km,which was affected by secondary seismogenic faults.2）Hard rocks were well developed with the highest density of earthquake-induced mountain hazards,and the density increased with the slope of mountain.3）The release of seismic energy was restricted by landform and river.The high density of earthquake-induced mountain hazards was in the high altitude,steep slope,intense incision and high drainage density.4）The earthquake-induced mountain hazards occurred in higher probability if the ruptured direction of faults was consistent with the gradient direction of topography and the aspect of slope,which was convenient for seismic energy transmitting.