Hydrogeological Characteristics Of Active Fault Caused By Wenchuan Earthquake And Its Impact On The Groundwater System Division With A Case Study Of Xiaoyudong Area

A active fault was developed by Wenchuan earthquake in Xiaoyudong area at 12th May, 2008.Hydrogeological characteristics of the active fault and groundwater system affected by the active fault were analyzed by radon measurement test, the flow velocity of the electrical method means test and leakage test. And some conclusions were showed as follows:The active fault, whose permeability coefficient and hydraulic conductivity are different from the original groundwater aquifer media, is banded distribution. Permeability coefficients among the hanging wall and the footwall of the fault and the fault itself are changed by the fault. The fault permeability and conductivity of water capacity may be greater or smaller than the hanging wall and footwall. Fault in Xiaoyudong is not acting as a barrier to flow, but act as a pathway between hanging wall and footwall, between inner of the fault and the hanging wall and footwall, and between shallow groundwater and deep groundwater. However, the recharge ,flow, discharge of the groundwater in and near the fault, and finally the local groundwater flow characteristics are affected by the fault. Xiaoyudong active fault plays the role of catchment channel and pathway to flow.Affected by the fault after Wenchuan earthquake, groundwater system in Xiaoyudong can be divided into regional groundwater flow system and local groundwater flow systems. Regional groundwater flow system is recharged by atmospheric precipitation, vertical infiltration of irrigation, and the mountain bedrock fracture water, then the groundwater flow moves to the river horizontally. One of the local flow system is recharged by rainfall and irrigation, infiltrating vertically to the aquifer, then flow to the discharge area, the fault zone, and finally transports to deep circulation. Another local flow system is mainly recharged by the fault zone, rainfall and irrigation water, and discharges to the stream. Overall, the shallow groundwater flow system in Xiaoyudong area is affected by topography, it transports mainly from higher terrain to lower terrain, and then discharges into the river, a new recharge and drainage channel was developed in original groundwater system.