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Geology of Mount Shasta

Figure 26

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Figure 26: Block diagram showing the locations of the FOCI of earthquakes that have occurred beneath Mount Shasta between August 1979 and June 2001. The block is 35 kilometers long from east to west, 35 kilometers wide from north to south, and 30 kilometers deep. It is centered on Mount Shasta's summit, which is shown schematically by the red triangle. The sizes of the points are proportional to the magnitudes of the earthquakes, with the largest being magnitude 3 and the smallest magnitude 1. Notice the concentration of foci southeast of the summit at depths between about 5 and 15 kilometers. Data are from the Northern California Earthquake Data Center database.


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