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


• Major fault : ~10km, 6.5 to 7 mag,

• Local Fault: <10km, 6 to 6.5 mag

Refer to your B. Sc. notes


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



Linear valley Sap Pond

Offset of drainage


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.


San Andres Fault


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


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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