TECTONIC ACTIVITY HISTORY BASED METHOD FOR ENGINEERING SAFETY DISTANCE TO ACTIVE FAULT

In essence,how much the engineering safety distance to active fault belongs the fracture-resistance problem. Aim is to reduce damage to the building due to occurrence of the active fault rupture in the future. Not all active faults can produce surface rupture. The seismo-active fault is the object of engineering avoidance.Researchers suggest many engineering distances to active fault using different methods. Whether these distances are suitable for a particular active fault still needs to conduct specialized research about this active fault. This paper respectively uses Helan Mountain piedmont fault and Yinchuan buried fault for an example. It studies the tectonic history of the active faults using the basic research method for active faults. It uses the past to predict the future of the active fault. The results of this study provide the basis for the active fault avoidance. To the exposed activefault,the first work is to identify whether it is a seismo-active fault using geological mapping,trenching. Then it is to determine the location of the engineering active fault avoidance according to recurrence characteristics of paleoearthquake events and fault scarp landscape in situ. The width of the fault zone in trench and the width of fault scarps can be used as a reference engineering safe distance from the active fault. For buried active faults,the location of the fault should first be positioned through various means. The results of trenching and drilling are to identify capable active faults and to analyze the tectonic activity history of the fault. The situ recurrence characteristics of the paleoearthquake events and the fault throw changes of different sedimentary strata at different depths in drilling profiles can be used to predict the future location of surface rupture. Location of the fault plane extended at the surface can be the occurrence location of the next earthquake surface rupture. It is the reference point to engineering safe distance. Through analysis,the distance of 15 m that was given by previous researchers from statistics can be applied to Helan Mountain piedmont fault and Yinchuan buried fault. The engineering safety distance to Yinchuan buried active fault is 40 m if the maximum positioning error is taken into account.