EPSC 201 Lecture Notes - Lecture 7: Thrust Fault, Plate Tectonics, Elastic Energy

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!!%
!!faults%are%produced%when%stress%is%applied%to%rock%
o!stress%causes%deformation%of%rock%–%strain%%
o!when%the%strength%of%the%rock%is%exceeded%there%is%failure%–%fault%%
Stress,%Strain%and%fracture:%
!!The%formation%and%movement%of%faults%causes%most%destructive%earthquakes%%
!!When%the%strength%of%the%rock%is%exceeded,%there%is%failure%and%release%of%the%strain%by%
sudden%dislocation%or%fracture%along%the%fault%plane%%
!!Development%of%a%fault%
o!Earth%shaking%is%caused%by%a%rapid%release%of%energy,%most%of%which%is%due%to%
tectonic%forces%
Introduction%to%earthquakes:%%
!!Common%%
o!Occur%everyday%
o!More%than%a%million%detectable%earthquakes%per%year%
!!Most%earthquakes%result%from%tectonic%plate%motion%%
!!Most%earthquake%damage%is%due%to%ground%shaking%%
Causes%of%Earthquakes:%
!!Seismicity%(earthquake%activity)%occurs%due%to:%
o!Sudden%motion%along%a%newly%formed%crustal%fault%
o!Sudden%slip%along%an%existing%fault%
o!A%sudden%change%in%mineral%structure%
o!Movement%of%magma%in%a%volcano%
o!Volcanic%eruption%%
o!Giant%landslides%
o!Meteorite%impacts%
o!Nuclear%detonations%
!!Fault%slip%is%the%most%common%cause%
Fault%in%the%Crust:%
!!Faults%are%crustal%breaks%where%movement%occurs%
o!Displacement%is%a%measure%of%movement%%
o!Fault%trace%is%the%ground%surface%expression%of%a%fault%%
!!On%a%sloping%fault,%crustal%blocks%are%classified%as:%
o!Footwall%(block%below%the%fault)%
o!Hanging%wall%(block%above%the%fault)%
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