Caldera chronicles: Crystallizing magma releases water which can trigger earthquakes

Yellowstone Caldera Chronicles is a weekly column written by scientists and collaborators of the Yellowstone Volcano Observatory. This week’s contribution is from David Shelly, seismologist, and Shaul Hurwitz, research hydrologist, both with the U.S. Geological Survey.

It is well established that pressure variations associated with water flowing through the crust (the outermost layer of the Earth) can trigger earthquakes. This is because pressurized fluids inside a fault zone can partially counter the force pressing the two blocks of rock on both sides of a fault together, making it easier for those blocks to slip along the fault. In other words, water in faults can help to promote earthquake activity.

Water is known to be a cause of earthquakes at Yellowstone and may be particularly important in triggering earthquake swarms, where many earthquakes are clustered in space and time and are not preceded by a large earthquake, or mainshock. Although moving magma can also trigger earthquakes, this process creates different patterns of seismicity, and triggering by water is thought to be much more common in Yellowstone.

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