Geography 2152F/G Lecture Notes - Lecture 7: Mercalli Intensity Scale, Epicenter, Seismometer
16 Nov 2020
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Earthquakes from rupture of rocks along fault: energy from earthquake released in form of seismic waves. Mapped according to epicenter, with focus directly below: measured by seismographs and compared by magnitude. Richter scale: measure of strength of wave 100km from epicenter. Modified mercalli intensity scale: qualitative scale based on damage. Elasticity of crust at focus: most common near plate boundaries friction along plate exerts force on rocks (deformation, when stress exceeds strength rock, ruptures, propagates in all direction. Comprised of 2 walls on incline defined by miners: Reverse fault: hanging-wall moved up relative to footwall inclined at angle steeper than. Thrust fault: like reverse except angle is 45 degrees or less. Normal fault: hanging-wall moved down relative to footwall. Tectonic creep: slow movement of rock along fracture cause by stress. Body waves: p-waves: move fast with push-pull motion, travel through solids/liquids, s-waves: slower, up/down motion, travel only though solids. Surface waves: slower than body waves, responsible for damage near epicenter.
