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Subsurface Fault and Colluvial Wedge Detection Using Resistivity, Refraction Tomography and Seismic Reflection. Sherif Hanafy King Abdullah University of science and Technology (KAUST). Outline. Motivations Methodology Study Area Data Acquisition (Resistivity and Seismic)
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Subsurface Fault and Colluvial Wedge Detection Using Resistivity, Refraction Tomography and Seismic Reflection SherifHanafy King Abdullah University of science and Technology (KAUST)
Outline • Motivations • Methodology • Study Area • Data Acquisition (Resistivity and Seismic) • Data Processing and Interpretation • Resistivity • Seismic • Summary and Future Work
Outline • Motivations • Methodology • Study Area • Data Acquisition (Resistivity and Seismic) • Data Processing and Interpretation • Resistivity • Seismic • Summary and Future Work
Motivations Demonstrate the capability of geophysics to detect shallow subsurface faults Is Qademah fault exists? Track the Qademah fault (if exist) trenching and dating ancient earthquakes at Qademah fault to assess size and recurrence intervals
Outline • Motivations • Methodology • Study Area • Data Acquisition (Resistivity and Seismic) • Data Processing and Interpretation • Resistivity • Seismic • Summary and Future Work
Methodology Ground surface Depth t’s are known, x’s are know, and s’s are unknown
Outline • Motivations • Study Area • Data Acquisition (Resistivity and Seismic) • Data Processing and Interpretation • Resistivity • Seismic • Summary and Future Work
Study Area Qadema Fault KAUST
Data Acquisition (Resistivity and Seismic)
Data Acquisition (Resistivity and Seismic)
Outline • Motivations • Study Area • Data Acquisition (Resistivity and Seismic) • Data Processing and Interpretation • Resistivity • Seismic • Summary and Future Work
Data Acquisation Seismic Equipment: Geometrics (NZXP + Geode) No of Profiles: 1 No. of shots: 109 Shot Interval: 3 m No. of Receivers: 109 Receiver Interval: 3 m Profile Length: 324 m • Resistivity • Equipment: Syscal R2 • No. of Profiles: 2 • No. of Nodes: 64 • Node Interval: 5 m • Profile Length: 315 m • Array Type: Wenner
Outline • Motivations • Study Area • Data Acquisition (Resistivity and Seismic) • Data Processing and Interpretation • Resistivity • Seismic • Summary and Future Work
Resistivity ResultsSite # 1 No. of Nodes: 64 Node Interval: 5 m Profile Length: 315 m Array Type: Wenner Raw Data
Resistivity ResultsSite # 1 S Sabkha CW Colluvial Wedge F Fan SG Sand-silt-gravel LS Limestone Inverted Data
Resistivity ResultsSite # 2 No. of Nodes: 64 Node Interval: 5 m Profile Length: 315 m Array Type: Wenner Raw Data
Resistivity ResultsSite # 2 S Sabkha CW Colluvial Wedge F Fan SG Sand-silt-gravel LS Limestone Inverted Data
Outline • Motivations • Study Area • Data Acquisition (Resistivity and Seismic) • Data Processing and Interpretation • Resistivity • Seismic • Summary and Future Work
Common Shot Gather CSG # 60 0 No. of shots: 109 Shot Interval: 3 m No. of Receivers: 109 Receiver Interval: 3 m Profile Length: 324 m Time (s) No of TT: 11881 TT passes Reci. Test: 9488 No. of TT rejected: 2393 No. of Iterations: 40 0.25 324 0 X (m)
Outline • Motivations • Study Area • Data Acquisition (Resistivity and Seismic) • Data Processing and Interpretation • Resistivity • Seismic • Summary and Future Work
Summary and Future Work • Resistivity and seismic methods used to detect the Qademah fault • One colluvial wedge is shown on both ERT and refraction tomogram • Reflection stacked section shows the Qademah fault and the associated antithetic fault(s)
Summary and Future Work • The Qademah Fault will be tracked to the south with • Seismic • Resistivity • EM • and possibly GPR • A trench will be made at Qademah fault to date the colluvial wedge • If more than one colluvial wedge is found, then we will be able to find the fault recurrence.