ENVR 200 Lecture Notes - Lecture 2: Richter Magnitude Scale, Geologic Hazards, Epicenter
12 Dec 2014
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What is the difference between the epicenter and focus of an earthquake? (p. 34, 35; figure 2. 3) The epicenter is the point on the surface of the earth directly above where the ruptured rocks broke to produce the earthquake. The focus is the point of initial breaking below. Earth"s surface, which is directly below the epicenter. How is it related to the amount of shaking and the amount of energy released by an earthquake? (p. 36; figure 2. 4; table 2. 3) The moment magnitude measures the size of an earthquake. Numerically it is similar to the more commonly reported richter scale, but this scale takes into consideration more geological data such as rock type, directivity and the area of rupture along the fault plane. An increase in one whole number to the next higher one represents a 10-fold increase in the amount of shaking and a 32-fold increase in the amount of energy released.
