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
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
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
