Active Fault

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Active Fault

• An active fault is a fault which has had

displacement or seismic activity during the geologically recent period (Holocene Epoch) (during the last 11,000 or so years before present). Ex San Andres fault

• Master fault : between major tectonic plates,

~100km, 8 mag earthquake, displacement

~10m

• Major fault : ~10km, 6.5 to 7 mag,

• Local Fault: <10km, 6 to 6.5 mag

Refer to your B. Sc. notes

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Features of Active faults

How Do Geologists Find Quaternary-Active Faults?

Stream Ponding

He, Rn emissions

Sharp bend along river course

Displacement of Quaternary formations

LIDAR

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Linear valley Sap Pond

Offset of drainage

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The newest tool to find active faults is Laser Imaging Detection And Ranging

(LIDAR), which uses laser light projected from an airplane to make a detailed image of the ground surface, even through trees in a forest.

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San Andres Fault

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Passive/dead/inactive Fault

• Movement has not occurred in man’s history

• Mature topography

• No seismic potential at present geodynamic condition, may reactivate with changing

tectonic conditions

• Ex Vakra thrust, Upper Siwalik Boulder Conglo not affected by this fault

• Vakra dam situated on Vakra thrust

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Fault identification and characterization

• Collect all relevant data from remote sensing, and any other sources

• Prepare fracture/lineament map

• Integrate with other information

• Characterization

Known fault (established)

Capable (active) fault = seismic potential Probable (inferred) fault

Dead (dormant) fault = zero seismic potential

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Figure

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References

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