The Tectonic Origin "Head Fall" Analysis And Numerical Simulation In Gaizi River Water Source

The Gaizi river water source is located in the western margin of Tarim Basin,first-order tectonic units belongs to the southwestern depression zone of Tarim, andthe second tectonic units belongs to the Kashi depression zone, sandwiches betweenthe kunlun mountains hercynian fold system and Tianshan mountain. Kashidepression’s main tectonic style is thrust nappe structure, it includs three huge thrustnappe zone, the uppal thrust nappe belt, which is consist of three large reverse faults,as one of it, the included uppal fault through the study area.Affected by the regional tectonic, the geologic structure and new tectonicmovement develop in the study area, Especially the new tectonic movement, which isgiven priority to lifting movement and accompanied by the squeezing action, andmade the stratum fold even fault strongly, as a result, in the NW-SE trend, formedfour basic parallel anticline uplift, synclinal depression and hidden fault, which isapproximately parallel to the anticline uplift.In the study area, the exposed strata are simple, mainly for the Cenozoic thirdseries （N）, Quaternary （Q）. The third series is mainly the Pliocene （N₂）, theQuaternary include the lower Pleistocene of Quaternary diluvium (Q₁^pl), MiddlePleistocene alluvium (Q₂^al), the upper Pleistocene alluvial layer (Q₃^pl) and theHolocene alluvium (Q₄^al).The special hydrogeology embodies in the "waterfall" phenomenon of study area,through field investigation, combined with collected geological, geophysical,hydrological geology, borehole data, analyze the study area’s tectonic and stratumcharacteristics, we found that the "head fall" phenomenon distribute in both sides offracture structure and the faults strike are vertical or near vertical with undergroundwater’s flow direction, and in faults’ both sides, the strata thickness are mutation, allthe things indicate that the "head fall" is caused by structure. Based on the translation and induction of research area’s geology, hydrogeologicconditions, with the help of groundwater’s flow field, select the GMS valuesimulation method to simulate the "head fall" phenomenon, characterize the fault’seffect, we use the barrier boundary, which is in the Modflow module, to generalizethe fault, take it as the second boundary condition and input the model, after model’sinspection operation and correction, the reflected situation is in good agreement withthe actual situation, which primely verified the "head fall" phenomenon’s tectonicorigin analysis of the study area and the correctness of fault handling in simulationmodel.By this study, analyzed the "head fall" phenomenon’s tectonic origin, initiallyestablished the numerical model, in which correctly generalize and process faultboundary, it has a practical guiding significance for further exploration of waterresources.