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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)

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Outline Motivations Methodology Study Area Data Acquisition (Resistivity and Seismic) Data Processing and Interpretation Resistivity Seismic Summary and Future Work

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Outline Motivations Methodology Study Area Data Acquisition (Resistivity and Seismic) Data Processing and Interpretation Resistivity Seismic Summary and Future Work

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Motivations 1.Demonstrate the capability of geophysics to detect shallow subsurface faults 2.Is Qademah fault exists? 3.Track the Qademah fault (if exist) 4.trenching and dating ancient earthquakes at Qademah fault to assess size and recurrence intervals

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Outline Motivations Methodology Study Area Data Acquisition (Resistivity and Seismic) Data Processing and Interpretation Resistivity Seismic Summary and Future Work

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Methodology Ground surface Depth ts are known, xs are know, and ss are unknown

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Outline Motivations Study Area Data Acquisition (Resistivity and Seismic) Data Processing and Interpretation Resistivity Seismic Summary and Future Work

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KAUST Qadema Fault Study Area

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Data Acquisition (Resistivity and Seismic)

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Data Acquisition (Resistivity and Seismic)

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Topography

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Outline Motivations Study Area Data Acquisition (Resistivity and Seismic) Data Processing and Interpretation Resistivity Seismic Summary and Future Work

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Data Acquisation Resistivity Equipment: Syscal R2 No. of Profiles: 2 No. of Nodes: 64 Node Interval: 5 m Profile Length: 315 m Array Type: Wenner 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

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Outline Motivations Study Area Data Acquisition (Resistivity and Seismic) Data Processing and Interpretation Resistivity Seismic Summary and Future Work

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Resistivity Results Site # 1 Raw Data No. of Nodes: 64 Node Interval: 5 m Profile Length: 315 m Array Type: Wenner

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Resistivity Results Site # 1 Inverted Data S SabkhaCW Colluvial Wedge F FanSG Sand-silt-gravel LS Limestone

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Resistivity Results Site # 2 Raw Data No. of Nodes: 64 Node Interval: 5 m Profile Length: 315 m Array Type: Wenner

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Resistivity Results Site # 2 Inverted Data S SabkhaCW Colluvial Wedge F FanSG Sand-silt-gravel LS Limestone

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Outline Motivations Study Area Data Acquisition (Resistivity and Seismic) Data Processing and Interpretation Resistivity Seismic Summary and Future Work

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No. of shots: 109 Shot Interval: 3 m No. of Receivers: 109 Receiver Interval: 3 m Profile Length: 324 m CSG # 60 0 0.25 0 324 X (m) Time (s) Common Shot Gather No of TT: 11881 TT passes Reci. Test: 9488 No. of TT rejected: 2393 No. of Iterations: 40

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Refraction Tomogram

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Reflection Stacked Section

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Result Summary

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Outline Motivations Study Area Data Acquisition (Resistivity and Seismic) Data Processing and Interpretation Resistivity Seismic Summary and Future Work

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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)

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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.

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Thank You