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earthquakesI - Physical Geology 101 21 Earthquakes I(p...

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Physical Geology 101 1 21. Earthquakes I (p. 296-303; 306) How many people have been killed by earthquakes in the last 4,000 years? ____________ How many people have been killed by earthquakes in the past century? ____________ What two recent earthquakes resulted in a combined ~360,000 fatalities? LOCATION YEAR 1. _______________________ _________ ( M 7.6 ; 86,000 fatalities) 2. _______________________ _________ ( M 9.0 ; 283,000 fatalities) Faults and Earthquakes Earthquakes occur along faults because tectonic stresses are constantly trying to push the two sides of a fault past each other. Which types of faults are associated with the following types of tectonic stresses? Tensional stresses: ___________________ Compressional stresses: ___________________ Shear stresses: ___________________ Tectonic stresses are always present in the crust, but any one fault doesn t produce earthquakes every day. This is because tectonic stresses need to overcome the strength of a fault. What is it that gives faults their strength? ___________________________ When the frictional strength of the fault is exceeded, the fault jumps forward (slips or ruptures) suddenly, producing an earthquake. How much slip generally occurs on a fault during a single earthquake? ____________ What is the largest amount of motion ever recorded at the Earth s surface during an earthquake, and where did it occur? Amount of slip: ____________ Location: _________________________ Is an earthquake produced every single time a fault slips? YES or NO? Some faults slip continuously in response to tectonic stresses, although very, very slowly. This process is called ________________. Why do these creeping faults slip continuously instead of producing earthquakes? __________________________________________
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Physical Geology 101 2 Theory of Earthquakes The reason that faults fail abruptly when the friction is overcome is because the rocks build up a lot of energy by getting deformed before an earthquake. The rocks get pulled in opposite directions on either side of the fault, but they are locked together by the friction along the fault. What type of energy builds up in the rocks? __________________________ In the crust, tectonic stresses are always present. So the energy stored in the rocks is violently released as fault slips and causes an earthquake. We feel this release of energy in the form of shaking of the
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