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

Bakhtiar Qader Aziz1, Peshawa Mohammad Ali2

Faculty of Science and Education, University of Sulaimani, 2 Faculty of Humanitarian Science, University of Sulaimani

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.

Keywords: Carbonate Cave; GPR; Resistivity Tomography

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