基于扩散方程的陡坎形貌测年方法进展  

MORPHOLOGIC DATING OF SCARP MORPHOLOGY BASED ON DIFFUSION EQUATION:A REVIEW

作　　者：许建红 陈杰[1] 魏占玉[1] 李涛[1] XU Jian-hong;CHEN Jie;WEI Zhan-yu;LI Tao(Xinjiang Pamir Intracontinental Subduction National Observation and Research Station,State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earthquake Administration,Beijing 100029,China;The Second Monitoring and Application Center,China Earthquake Administration,Xi′an 710054,China)

机构地区：[1]中国地震局地质研究所,地震动力学国家重点实验室,新疆帕米尔陆内俯冲国家野外科学观测研究站,北京100029 [2]中国地震局第二监测中心,西安710054

出　　处：《地震地质》2023年第4期811-832,共22页Seismology and Geology

基　　金：国家重点研发计划项目(SQ2022YFC3000066);国家自然科学基金(41802229,41772221);第2次青藏高原综合科学考察研究项目(2019QZKK0901)共同资助。

摘　　要：陡坎是一种自然界常见的台阶状地貌,但其形成年龄通常很难直接测定。发育在松散堆积物中的陡坎经过初期短暂的重力垮塌之后,将经历漫长的低能退化过程。如果陡坎剖面形态的演化可基于扩散方程来模拟,且扩散系数可独立标定,即可利用陡坎地形剖面估算其年龄,这种方法被称为形貌测年。文中简要回顾了陡坎形貌测年的研究历史,介绍并讨论了陡坎退化的概念模型与扩散模型,特别是非线性扩散模型的建立及求解、参数在扩散模型中所起的作用、最佳陡坎形貌年龄的确定流程等,分析了陡坎上、下地貌面坡度对陡坎退化的影响,编制了非线性扩散模型的年龄图版,给出了图版的应用实例,验证了形貌测年方法的有效性。线性扩散模型和非线性扩散模型均可用于单次事件陡坎的退化分析,但对于年轻的单次事件陡坎推荐使用非线性扩散模型。断层重复活动形成的陡坎的退化分析则需要谨慎对待,恒定滑动速率陡坎的非线性扩散模型适用于模拟年龄<10ka、活动速率高的断层陡坎的演化;多次事件陡坎模型(包括线性扩散和非线性扩散)需要仔细评估每次事件在陡坎剖面上的断错位置及其位移量。尽管陡坎形貌测年方法存在很多假设条件,但目前快速获取一定范围内的高分辨率地形数据已成为现实,从这些数据中可以沿着同一陡坎提取大量剖面进行分析,继而得到具有统计意义的结果,这为陡坎退化分析和形貌测年方法提供了广阔的应用前景。A scarp is a common step-like landform in nature,which consists of a gently sloping plane connected to the upper and lower geomorphic surfaces of differing elevations.Common scarps include fault scarps,terrace scarps,lake shoreline scarps,shoreline scarps,volcanic ash cinder cones,etc.Scarps are often used as strain markers because of their linear characteristics and are favored in the study of active tectonics.However,it is difficult to directly constrain their ages.Instead,they are usually constrained by the ages of the upper and lower geomorphic surfaces.The scarp developed in loose deposits is controlled by a long process of low-energy degradation after a short collapse.This process can be modeled by the diffusion equation because the process can be considered as a slope process under the transport-limited condition.Under this condition,the slope can provide enough loose material for transport,that is,the material transport capacity is less than the material supply capacity.If process assumptions are sufficiently valid and rate constraints can be calibrated independently,the true age of scarps can be obtained.This method is called morphologic dating.This method has been included in many textbooks published overseas,but there have very little research on this method in China.Both linear and nonlinear models have been developed to describe scarp degradation.Linear diffusion models assume that the diffusion coefficient is a constant,whereas nonlinear transport models generally define the diffusion coefficient as a nonlinear function related to the topographic gradient.Compared to the linear transport models,nonlinear transport models can better explain the phenomenon of rapidly increasing deposition flux as the gradient approaches a critical value.In this paper,we review the study history of scarp degradation analysis and the concept model of scarp degradation.We focus on the establishment of the nonlinear model,the role of the different parameters in profile evolution,determining the best-fit age using a full-s

关 键 词：陡坎 陡坎退化 扩散模型 形貌测年 断层陡坎 

分 类 号：P315.2[天文地球—地震学] P542[天文地球—固体地球物理学]