California continues to shake following yesterday’s 6.0-magnitude earthquake in Napa. Associate Professor Andrew Newman travels around the world, trying to better understand earthquakes and volcanoes.
Despite being the largest earthquake in the region in the past 25 years, the Napa earthquake represents the overall expected behavior of the earth's crust near the active plate boundary that separates most of North America from the Pacific plate. Along the San Andreas and adjacent faults, the plates try to slide past one another at a little more than an inch a year. When the surface between the plates sticks, it builds energy that is released in these earthquakes.
An earthquake of this magnitude or larger occurs globally about every three days. However, because this earthquake was shallow (only five miles or so deep) and because it occurred very close to the town of Napa, it caused relatively significant damage to the area. The earthquake had very typical behavior, exhibiting no outwardly visible sign immediately beforehand, and is now accompanied by substantial aftershocks that may continue for weeks to months.
Though aftershocks are typically much smaller, there remains the possibility that this event can trigger similar or even larger earthquakes along the same fault or on nearby faults. While the chance of these larger events remains relatively remote, it’s certainly a good time to be aware of the potential.
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