EARTHSC 2GG3 Lecture Notes - Lecture 2: Mercalli Intensity Scale, San Andreas Fault, Seismic Wave
24 Dec 2016
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Document Summary
They result from the rupture of rocks along a fault. Energy from an earthquake is released in the form of seismic waves. They are mapped according to the epicentre; the focus is located directly below the epicentre. They are measured by seismographs and compared by magnitude. *know difference between epicenter and focus, epicenter is on surface of earth and the focus is underground(epicenter is directly above focus) Oil drilling in oklahoma is causing many earthquakes these are man-made, non-nat earthquakes. The magnitude of an earthquake is expressed as a number to one decimal place. This type of measurement was first developed by richter in 1935. The richter scale was a measure of the strength of a wave at a distance of 100 km from the epicentre. Since then, more accurate methods have been developed and the richter scale is no longer used. Today, earthquakes are measured using the moment magnitude scale (m).
