顾及坡体赋存环境的概率地震滑坡危险性制图

Probabilistic seismic landslide hazard mapping with consideration of slope occurrence environment

位移模型是评估地震滑坡危险性的一种重要方法。作为位移模型主要输入的岩体参数,一般仅考虑岩体的岩性差异,而对岩体所在坡体赋存环境不同而产生的岩体强度空间差异性缺乏必要考虑,影响地震滑坡危险性评估的可靠性。本文基于汶川同震滑坡分析与影响因子定权研究,提出了一种基于位移模型且顾及坡体赋存环境的概率地震滑坡危险性评估方法,研发了基于ArcGIS的概率地震滑坡危险性制图模块,并以康定为例进行了应用试验。根据第五代中国地震动参数区划图提供的地震动峰值加速度,进行了常遇、罕遇地震场景下康定地震滑坡危险性制图。结果显示,相比于未顾及坡体赋存环境影响,本文方法能够识别出更多潜在地震滑坡危险区;在常遇地震场景下,康定部分区域为地震滑坡高危险区域,其分布主要受构造环境与降雨影响;而在罕遇地震场景下,康定受地震影响的范围显著增加,且呈现明显的集聚现象,尤其是康定城区附近及G318国道康定-泸定路段两侧存在大量地震滑坡高危险区。此外,对因岩体强度差异导致的地震滑坡危险性制图的不确定性进行了量化分析,结果显示,岩体强度参数是导致评估结果存在不确定性的重要因素;实践中,应针对具体应用场景选择合适的岩体强度开展概率地震滑坡危险性评估与制图。本文方法扩展了GIS的地灾风险制图应用,具有普适性,可持续改进;试验成果可为康定未来土地利用规划、地震地质灾害防治及川藏铁路安全提供参考依据。

Displacement model is a significant method for probabilistic seismic landslide hazard assessment.However,as the main inputs of the displacement model,the physical-mechanical parameters of rock mass only consider the lithological differences,while the spatial heterogeneous of the rock mass strength resulted from the slope occurrence environment was ignored before,which affects the reliability of the seismic landslide hazard assessment.Based on analysis to co-seismic landslides resulted from Wenchuan earthquake and study on the weighting of impact factors,this paper presents a new method for probabilistic seismic landslide hazard assessment with consideration of slope occurrence environment and develops a group of ArcGIS-based modules for probabilistic seismic landslide hazard mapping.Taking Kangding as an experimental example,the reliability of the proposed method is verified by using the landslides from remote sensing visual interpretation and field survey.Finally,according to the peak ground acceleration under different earthquake scenarios provided by the fifth-generation seismic ground motion parameters zonation map of China,the permanent seismic displacements of Kangding under different earthquake scenarios are computed,and the seismic landslide hazards are mapped.The results show that under the frequently encountered earthquake scenario,some areas in Kangding are high seismic landslide hazard areas mainly affected by the tectonic environment and rainfalls;while under the rarely encountered earthquake scenario,the area seriously affected by earthquakes in Kangding increases significantly and shows an obvious spatially clustering distribution,especially in the vicinity of Kangding and where along Kangding-Luding segment of national highway G318.Besides,the uncertainty of seismic landslide hazard mapping caused by rock mass strength difference is quantified and analyzed,which shows that rock mass strength is critical for the uncertainty of assessment results.For application,suitable rock mass strengths should be selected for different scenarios to conduct probabilistic seismic landslide hazard assessment and mapping.The presented method expands the GIS application in geohazard mapping,which is of general adaptability and could be improved further.The experimental results are valuable for future land planning and utilization in Kangding,and for prevention of earthquake-induced landslide and safeguard of Sichuan-Tibet railway.