Geology Introduction to Thrust Faults Up Down

Thrust faults Terminology Calculating stretch and shortening Throw, heave, and slip Stratigraphy and thrust faults

Thrust Fault

Thrust Fault Terminology Original layer cake template

Thrust Fault Terminology Transport Direction ForelandHinterland Fault achieves trajectory rapidly

Fault Bend Fold Movie

Thrust Fault Terminology

Calculating Shortening for Thrust Faults lolo lflf 50 km 40 km Shortening = lo lo lo lo l f - l o * 100% If Stretch [S] = l f /l o, then shortening = lo lo lo lo lflflflf -1 * 100% ( )

Calculating Shortening for Thrust Faults lolo lflf 50 km 40 km Shortening = lo lo lo lo l f - l o * 100% = * 100% = -20%

A Caution Regarding Shortening Choosing a minimum l o value yields maximum shortening lolo lflf 50 km 40 km Shortening = lo lo lo lo l f - l o * 100% = * 100%= -20%

Shortening Calculation lolo lflf 40 km 30 km Shortening = lo lo lo lo l f - l o * 100% = * 100% = -25% Thus “shortening” is relative to the baseline you pick Thus “shortening” is relative to the baseline you pick

 Throw, Heave, and Slip Throw Heave  Slip (Throw) 2 + (Heave) 2 = (Slip) 2 Sin  = (Throw/Slip) Cos  = (Heave/Slip) 

Increasing Stratigraphic Thickness

Evidence for Thrust Faulting in Boreholes

References Slides Slides Twiss, R. J. and E. M. Moores, Structural Geology, W. H. Freeman & Co., New York, 532 p., 1992.