Geophysical investigations of the potential sinkholes in Al Hassa, Eastern Saudi Arabia

Hofuf area in Al Hassa District of Saudi Arabia is well known for its subsurface sinkholes, solution cavities, voids, karsts and caves. These cavities and sinkholes have resulted in short and long term engineering structural stability issues. The development of a sinkhole in a residential area of Hofuf alarmed the authorities to plan for a detailed geophysical investigation to assess sinkhole formation potential near existing buildings. Electrical Resistivity Tomography (ERT) and Multichannel Analysis of Surface Waves (MASW) surveys were carried out to investigate the subsurface strata conditions to detect and map existing and potential cavities/sinkholes in the area. A total of 200 profiles were carried out in the study area. ABEM Lund Imaging System consisting of Terrameter LS was used to acquire apparent resistivity data during the survey. Active MASW method was carried out using DMT XSummit seismograph and receivers of 4.5 Hz frequency. The results revealed several anomalous locations which were subsequently validated by drilling boreholes. Zoning of the area was carried out based on the potential of sinkhole formation and a number of recommendations were made to enhance the long term stability of existing structures.