Ground Magnetic Investigation of Subsurface Structures Affecting Wadi Thuwal Area, KSA

Abstract

Ground magnetic survey was carried out in Wadi Thuwal area, north of Jeddah, during winter and spring of 2007-2009. The survey was intended to delineate the subsurface structures and covered an area of about 130 km 2 , located between latitudes 22° 10' 00 N and 22° 16' 53.5 N and longitudes 39° 06' 40 E and 39° 16' 20 E. The survey was conducted along profiles taking EW and NS directions. The field data were reduced and then interpolated to produce a high resolution total intensity ground magnetic map (HRTMI). Shaded relief maps have been effective in showing structural trends and characteristic anomaly patterns. Magnetic susceptibility measurements (k) were attended throughout the entire ground survey. The depth to the sources of the ground-magnetic anomalies was estimated using 2D and 3D Euler deconvolution. Observed surface faults are expected to be initiated from the basement. 2D and 3D analytic signal analysis and derivative maps show several trends crossing the study area. These trends, which are attributed to faults or contacts, are extended to the east of the study area, and further to the Arabian Shield (East), where some of them represent major faults that evidently have an impact on the water distribution potentiality of the Wadi. These trends are basically taking NE-SW faults direction, the rift shoulder master faults with N-S direction, NW-SE, and NNE-SSW normal faults direction. The Euler deconvolution analysis using N=1, reveals distinctive patterns of subsurface dikes. These may be attributed to dike swarms trending NW-SE and NNW-SSE. Keyword: Magnetic, Thuwal, 3D Euler deconvolution, analytic signal.