山西地堑系地裂缝发育特征及其成因分析

从系统论和耦合论的角度,充分利用前人研究数据,分析研究了山西地堑系地裂缝的分布、规模、时间、强度和活动特征以及发育规律及动力来源和形成原因。研究发现:山西地堑系地裂缝以小型地裂缝为主,集中出现于1981-2005年,主要分布于盆地边缘山前冲洪积平原盆山过渡带和盆地内次级地貌单位过渡带以及第四系厚度突变区、地下水降落漏斗的边缘区;山西地堑系整体以张性地裂缝为主,活动强度中等,运动方式以垂直运动为主,同时伴随水平拉张运动和右旋扭动,总体上垂直运动大于横向水平拉张大于水平扭转;青藏高原隆起导致鄂尔多斯盆地整体右旋挤压运动是山西地堑系地裂缝的根本动力来源,深部断裂构造和深部沉积基底宏观上控制了地裂缝的发育地区和发育规模,盆地周缘活动断裂控制了地裂缝的空间分布,新构造活动和地震加剧了地裂缝的活动;盆地边缘地层的富水性、大孔隙性,盆地内部第四纪松散层的可压缩性,为地裂缝的产生提供了物质基础,盆地内部不同块体的泊松比、密度、重力差异也是地裂缝产生的一个重要动力原因,第四纪冲洪积土和风积黄土的管涌和潜蚀易发性一定程度了加剧了地裂缝拓展。

Geofracture Development Features and Genetic Analysis in Shanxi Graben System

From system theory and coupling theory points of view,taking full advantage of previous studied data have analytically studied the Shanxi graben system geofractures distribution,scale,age,intensity and movement features,as well as development pattern,dynamic sources and genesis.The study has shown that the geofractures in Shanxi graben system are mainly small geofractures,concentratedly appeared during 1981~2005.Geofractures are mainly distributed in basin margin pediment alluvial-pluvial plain basin-mountain transition zone and basin internal secondary morphological units’transition zone,as well as in Quaternary thickness mutation zone,groundwater depression cone margin.In Shanxi graben system,geofractures are mainly tensional as a whole,activity intensity medium,movement mode mainly vertical,meanwhile followed by horizontal extensional movement and dextral torsion;on overall,vertical movement>transverse horizontal extension>horizontal torsion.The Qinghai-Tibetan Plateau uplift led to the Ordos Basin entirety dextral compressional movement has been the essential dynamic source of geofractures in Shanxi graben system.Deep faulted structure and deep sedimentary basement have macroscopically controlled geofracture development distributed area and scope;basin peripheral active fault has controlled geofracture spatial distribution;neotectonism and earthquake increased geofracture movement and basin margin strata water yield property and large porosity,as well as basin internal Quaternary loess bed compressibility and provided material basis for geofracture producing.Basin internal different blocks’Poisons ratio,density,gravity differences are also major dynamic causes;susceptibility of piping and suffosion in Quaternary alluvial-pluvial soil and aeolian loess can intensify geofracture prolongation to a certain extent.