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
𝑁𝑗
𝑡=
𝑁𝑗
𝑥𝑗 𝑠𝑗
𝑗=1
𝑡𝑖 =
𝑥𝑖𝑗 𝑠𝑗
𝑗=1
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)
Topography
Outline
• Motivations
• Study Area
• Data Acquisition (Resistivity and Seismic)
• Data Processing and Interpretation
• Resistivity
• Seismic
• Summary and Future Work
Data Acquisation
Seismic
Resistivity
Equipment:
No. of Profiles:
No. of Nodes:
Node Interval:
Profile Length:
Array Type:
Syscal R2
2
64
5m
315 m
Wenner
Equipment:
Geometrics
(NZXP + Geode)
No of Profiles:
1
No. of shots:
109
Shot Interval:
3m
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:
Node Interval:
Profile Length:
Array Type:
64
5m
315 m
Wenner
Resistivity Results
Site # 1
S Sabkha
F Fan
LS Limestone
Inverted Data
CW Colluvial Wedge
SG Sand-silt-gravel
Resistivity Results
Site # 2
Raw Data
No. of Nodes:
Node Interval:
Profile Length:
Array Type:
64
5m
315 m
Wenner
Resistivity Results
Site # 2
S Sabkha
F Fan
LS Limestone
Inverted Data
CW Colluvial Wedge
SG Sand-silt-gravel
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
Time (s)
No. of shots:
109
Shot Interval:
3m
No. of Receivers: 109
Receiver Interval: 3 m
Profile Length:
324 m
0.25
No of TT:
11881
TT passes Reci. Test: 9488
No. of TT rejected: 2393
No. of Iterations:
40
0
324
X (m)
Refraction Tomogram
Reflection Stacked Section
Reflection Stacked Section
Result Summary
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.
Thank You