基于高分辨率地形数据的断层陡坎形态演化与强震活动关系研究

Correlation between Active Fault Scarp Evolution and Strong Earthquake Activity Based on High Resolution Geomorphic Data

摘要:

断层陡坎的形态可以保存有关断层带上地震活动等重要信息,陡坎上的坡折就是多次地震发生后陡坎演化留下的微地貌信息。以往研究选取的断层陡坎多为位于标准阶地面上的断层陡坎,而断层沿线地貌现象复杂,因此需要探索一种具有普适性的断层陡坎形态研究方法。本研究将常见的断层陡坎剖面按照形态划分为三种类型,以LiDAR技术获取的0.2m分辨率DEM数据为基础,选择了8个属于不同断层陡坎剖面类型的实验区,每个实验区采集不少于20条剖面,通过窗口检验确定研究区最佳数据获取移动窗口为7个像元并计算每条剖面的坡度值,通过坡度约束限定陡坎范围,进而识别坡折并获取坡折信息。对坡折信息进行概率密度统计,根据概率密度统计图中的峰值个数确定强震事件的次数。结果显示,陡坎形态研究结果与古地震探槽结果表现出较好的一致性,表明本文提出的陡坎形态研究方法可以适用于不同类型断层陡坎来确定强震事件次数。

Abstract:

The morphology of fault scarps may preserve significant information about earthquakes. However,the selected fault scarps in previous studies were mostly located in standard to nearly standard terraces. In reality,however,the geomorphology along the fault is complex,so that we should find the more appropriate means to analyze the morphological characteristics of fault scarps. In this study,the fault scarps are divided into three types according to their morphology. Based on 0.2m-resolution DEM generated by LiDAR technology,different fault scarp types of 8 experimental areas were studied,in which over 20 topographic profiles are collected in each experimental area. The optimal sliding window size is determined with 7 pixels determined by window inspection and the slope of every profile is calculated. The scarp range is determined through slope constraint. Then we recognized the breaks in slope to determine the position of slope breaks. After calculating the probability density of slope breaks in each experimental area,we determine the number of strong earthquakes from its peak quantity. The results of our fault scarp morphology study are in good agreement with the paleo-earthquake study previously reported in the study area,which indicates that the micro-geomorphology quantitative analysis of fault scarp in this study is applicable to determine the number of strong paleo-earthquakes from different types of fault scarps.