The Science Behind the Alaska Earthquake with Casey Webb
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The Science Behind the Alaska Earthquake with Casey Webb


On November 30, 2018, a 7.0 magnitude earthquake shook Anchorage, Alaska and the surrounding areas. Hitting approximately eight miles north of the city, the earthquake damaged roads and buildings and produced a brief tsunami warning.


Casey Webb, lecturer of geology at Southern Utah University, explains that the southern coast of Alaska and the Aleutian Islands are located along a plate boundary where Earth’s crust and upper mantle are split into distinct sections or plates.  


“Here the Pacific Plate converges and subducts beneath the North American Plate at a rate of 6-7 cm per year. This subduction occurs along a very large fault called a megathrust fault. Displacement along this fault doesn’t occur in a smooth, seamless motion, but rather through a series of jolts or earthquakes.”


While earthquakes are common in the region, the last major two experienced were in 1983. Over the past century, the region has seen 14 other earthquakes above 6.0 magnitude, including one of the largest on record, the Great Alaska Earthquake (9.2) in 1964.


“Megathrust faults can also produce Earth’s largest earthquakes including the 1964 Alaska Earthquake and the 1960 Chilean Earthquake, which recorded a 9.5 magnitude and released over 1,000 times the energy of the recent 7.0 Anchorage Alaska Earthquake. These large earthquakes (over 9.0) are rare, occurring globally about once every 25 years.”


Beyond ground shaking, tsunamis are another hazard that occur along these megathrust faults.  


“Tsunamis are large ocean waves that are produced from the sudden displacement of the ocean floor during an earthquake. As the wave approaches the shore, the wave slows down and compresses causing the height of the wave to increase significantly. The size of the tsunami is determined by a variety of factors including the location and size of the earthquake as well as the geometry of the shoreline.”


Currently in his second year of teaching at SUU, Webb fully utilizes the geology of southern Utah to give his students a hands-on learning experience.



Media Contact

Rachelle Hughes

rachellehughes@suu.edu


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