A microgravity investigation of the subsurface at the United Arab Emirates University campus

This paper investigates subsurface structures within the United Arab Emirates University (UAEU) campus using microgravity survey. Gravity methods are widely used in geophysical exploration to detect density variations that may indicate subsurface anomalies. The primary objective of this research is to generate the Bouguer anomaly map of the UAEU campus to map subsurface structures and to assess potential geological hazards such as cavities. A total of 76 gravity stations were measured across the UAEU campus using the Scintrex CG-6 gravimeter. The acquired gravity data underwent standard processing to obtain the Bouguer anomaly, including tidal, instrumental drift, latitude, free air, Bouguer, and terrain corrections. The first Bouguer anomaly map of the UAEU campus was produced, revealing gravity values ranging from 112.8 to 115.1 mGal. High gravity anomalies are concentrated in the north-eastern and western regions, while lower gravity anomalies are predominantly observed in the southeastern and southwestern areas. Gravity gradient derivative techniques, such as the horizontal gradient, tilt angle, horizontal derivative of tilt angle and analytic signal were applied to the Bouguer anomaly. A 3-D gravity inversion was performed, modeling density variations from the surface down to a depth of 300 m below the sea level. The study successfully identified significant density contrasts indicative of probable cavities or low-density bodies, lithological variations and possible faults zones dominant structural trends along WNW-ESE, NW-SE, N-S, and E-W directions in the study area. Two distinct geological layers were identified: a shallow layer extending up to approximately 50 m and a comparatively deeper layer ranging from 50 to 100 m in depth. The 3-D inversion model delineated two prominent low-density anomalies at depths of 125-175 m from surface, suggesting the presence of cavities or low-density zones. This research represents the first high-resolution microgravity study of the UAEU campus, establishes a baseline microgravity dataset for the UAEU campus. The results enhance understanding of subsurface and highlight the need for further geotechnical and geophysical investigations to validate and refine cavity detection and hazard assessments.