Geology And Geophysics

Strike Slip Faults Experiment



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A strike slip fault is a vertical rupture which causes a horizontal, or parrallel shift of the ground either side of the rift.  The most famous strike slip fault line occurs in California on the San Andreas fault line.  This fault line is along the boundary of two plates of the Earths crust; The Northern Pacific tectonic plate to the South and West, and the North American tectonic plate to the North and East.  These two plates are moving away from each other with the Northern Pacific sliding laterally to the North of the North American plate. 

When the pressure on the Earths crust, due to the movements of the plates becomes too much, a catastrophic movement occurs where the plates will 'jump' to a point of least pressure.  This is what causes an earthquake and the terrible damage we have seen in the past.

A flash animation of a strike slip fault provided by the 'USGS earthquake hazards program' can be found here .

If an earthquake causes a right to left strike slip shift then it is termed a 'Sinistral' slip.  A left to right shift of the block is termed a 'Dextral'.  The movement is determined from the point of view of an imaginary observer at the fault line itself. 

Bends along a strike slip fault can cause massive devastation.  If the motion of the slip is towards a bend in the fault line (a restraining bend) then the earth is pushed upwards to create thrusts and folds as the two plates push against each other.  This can create hills and mountains with rough jagged peaks.  Alternatively, if the movement of the plates is away from the bend in the fault line (a releasing bend) then huge holes, or basins can be formed.

A simple experiment to show some effects of strike slips can damage the earth is to use two wooden blocks and a sheet of wet kitchen paper.  To carry out the experiment place the two blocks of wood side by side so their edges are touching.  These are your tectonic plates.  Place the paper kitchen towel on top of the blocks and wet thoroughly.  Now slide the wood blacks laterally against each other slowly.  The kitchen towel, being stuck to the blocks will show the same effects of the top layer of the earths crust as you move the blocks.

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ARTICLE SOURCES AND CITATIONS
  • InfoBoxCallToAction ActionArrowhttp://www.see.leeds.ac.uk/structure/faults
  • InfoBoxCallToAction ActionArrowhttp://earthquake.usgs.gov/learn/animations/animation.php?flash_title=Strike-slip+Fault+Flash+Animation&flash_file=strikeslip&flash_width=240&flash_height=310