基于数值模拟的长白山天池火山泥石流灾害展布范围分析及预测

Analysis to the Lahars Extent in Changbai Mountains by Numerical Simulation

利用模拟软件LAHARZ,基于长白山天池火山1/25万数字地形图,对二道白河、松花江、鸭绿江以及图们江4条泥石流易发河道进行了火山泥石流的数值模拟。模拟中依据历史喷发柱高度和地形平均坡度设定能量锥最佳阈值为0.07;通过实际河流与计算所得河流的对比匹配,设定河流最佳阈值为5 000;根据历史上长白山地区火山泥石流的爆发规模,设定了108 m3,109 m3,1010 m3和1011 m3 4个体积阈值。通过模拟计算发现,不同河道设定不同阈值流动影响范围有所不同,其灾害规模也相应变化,且模拟所得灾害分布范围与长白山地区的历史火山泥石流分布范围相似。依据模拟计算结果,将长白山火山泥石流灾害区划为4级,其对应的覆盖半径分别约为40km,70km,80km和100km,该结果可为长白山地区的建设规划提供参考。另外,该模型与灾害区划的方法也可为其它火山区的火山泥石流灾害区划提供借鉴。

The core model of LAHARZ is a semi-empirical numerical model based on the hydrodynamics model and combination with the analysis on the lahars of nine volcanoes.The lahars in four high easy-happening rivers,Erdaobai River,Songhua River,Yalu River and Tumen River,are simulated by the LAHARZ based on the 1∶250000 digital elevation model.The threshold of the energy cone is set to 0.07 according to historical plume height and the average slope.By comparing and matching the simulated river with the real river,the river threshold value is determined to be 5 000.And the volume thresholds are defined as 108m3,109m3,1010m3,and 1011m3 by their historical lahar volumes.The simulated results show that the flow distance and the damage scale were influenced by the different thresholds,which is similar with the historical lahars＇ extent.The damage grades are divided into four levels as 40 km,70 km,80 km and 100 km.It is important for the planning and construction in the Changbai Mountain area.In addition,this disaster zoning model and method can be used to be the reference of other volcanoes.