Karst cavity detection in carbonate rocks by integration of high resolution geophysical methods.

Combined surveys using Ground Penetrating Radar (GPR) and Electrical Resistivity Tomography (ERT) are deployed to provide a cost effective characterization of the subsurface karst environments. A total of 12 GPR traverses and 4 ERT lines with lengths from 140 to 710 m are conducted at Sulaimani governorate, NE Iraq (45o 04' E and 35o 35' N). The area represents a broad syncline of limestone rocks, which is covered by a thin layer of recent sediments. Great anomaly depicting crest (high) like pattern was noticed on GPR records. A plausible interpretation for this anomaly was a cavity filled either by groundwater or by residual products of karstification. The presence of this cavity was confirmed also by electrical resistivity tomography. An excellent correlation exists between GPR signatures and ERT layers. The extension and the depth to the top of the cavity were determined from both GPR data and 2D inversion interpretation. A huge cave was discovered. It is located at depth of 25.0 meters. It has an elongated shape that extends from southeast to northwest direction. The geophysical survey results show this cave with approximate dimensions of 150.0 m long, 35.0 m wide and 24.0 m high.