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) 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 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

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

KAUST Qadema Fault Study Area

Data Acquisition (Resistivity and Seismic)

Data Acquisition (Resistivity and Seismic)

Topography

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

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

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

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

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

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

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

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

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

Refraction Tomogram

Reflection Stacked Section

Result Summary

Outline Motivations Study Area Data Acquisition (Resistivity and Seismic) Data Processing and Interpretation Resistivity Seismic 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.

Thank You