Geography 2152F/G Lecture Notes - Lecture 7: Mercalli Intensity Scale, San Andreas Fault, Aseismic Creep
20 Jan 2018
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Document Summary
Result from rupture of rocks along a fault. Energy is in the form of seismic waves and mapped below the epicentre. The richter scale measures strength of a wave at a distance of 100km from the epicentre. No longer used as more accurate methods have been developed. Expressed as a number to one decimal place. Determined by: area ruptured along a fault, amount of movement along fault, elasticity of the crust at the focus. Ex: an m7 earthquake reps 10x the amount of an m6. *stronger earthquakes have lower frequency then smaller ones. The modified mercalli intensity scale is a qualitative scale based on damage to structures and the affect on people. Earthquakes are common at or near plate boundaries. (motion is not usually smooth or constant) Friction along the boundary exerts a force (stress) on the rocks, exerting strain or deformation. When the stress exceeds the strength of the rock, there"s sudden movement along a fault.
