Projects

The near surface geology in Qatar is known for its expansive limestone deposits, and limestone

quarries provide building material for construction sites throughout the country. While, limestone

deposits offer a good foundation for construction sites, they are also associated with localized karst

features which may cause collapse hazards. Consequently, development sites need to be scanned for

karst zones before construction commences. Drilling is a common technique to interrogate the

subsurface, but the costs of providing reliable coverage make it less desirable. Therefore

non-invasive techniques are needed to cover large areas with higher resolution and reduced costs. In this study we propose to employ scattered seismic waves, generated by passive and active seismic means to interrogate the subsurface for karst features. The method is base on the principle that air or water-filled cavities and fractures represent strong contrasts for seismic waves relative to the surrounding limestone. Therefore, these features generate strong scattered seismic waves, when probed by active seismic sources or background seismicity. The scattered seismic waves can be used to locate the cavities and fractures, determine their size and content (i.e., water- or air-filled, etc.).

Large-scale near-subsurface imaging of new development areas In Qatar (NPRP 4 - 138 - 1 - 026)

The Middle-East has seen a recent boom in construction including the planning and development of complete new sub-sections of metropolitan areas. Before planning and construction can commence, however, the development areas need to be investigated to determine their suitability for the planned project. Subsurface parameters such as the type of material (soil/rock), thickness of top soil layer, thickness and elastic moduli of rock layer, for example, comprise important information needed before a decision concerning the suitability of the site for construction can be made. Typically, these parameters are obtained by point measurements through augers, drilling, or excavations. This can become prohibitively expensive if the area is geological heterogeneous, particularly for large construction sites. To solve this problem, we propose to apply a recently developed non-invasive and more cost effective method based on the recording of noise-generated seismic surface waves, which can cover large areas, provide higher resolution and deeper imaging than the currently available methods. This technique will require seismic sensors to be deployed in passive mode over the area of interest and record ground motion generated by cultural and natural sources over a time span of several months up to a year. The analysis of the data will yield information of the subsurface parameters including type of geologic layers and their elastic parameters.