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Q Does an earthquake ever form a new tectonic plate?

— James Webb, Mineral Point, Wis.

A Chuck DeMets, professor of geophysics at the University of Wisconsin-Madison:

Most earthquakes occur when a geological fault, a fracture within the Earth’s crust, slips and releases energy. Individual faults, some of which form the tectonic plate boundaries, build up strain over decades and centuries to eventually break in large earthquakes.

One earthquake by itself isn’t enough to create a new tectonic plate, even if it’s really large.

New tectonic plates can form when the forces acting on the edges of an existing plate change. For example, a large existing plate with an awkward shape could tear into new pieces or begin folding on itself.

That process usually takes hundreds of thousands to millions of years. It could take thousands of large earthquakes within a plate to break it into two plates.

Not all earthquakes are natural. Human activity can definitely cause earthquakes, and this has been known since the 1950s and 1960s. What causes faults to stay locked is friction along a fault line. Anytime you change friction across a fault, there’s the potential for an earthquake, or the fault to slip.

Pumping fluids into the ground can make faults more slippery. When you reduce the friction by pumping some water into the ground, like in hydrofracking, it frequently triggers faults that would otherwise be stuck to slip.

Blue Sky Science is a collaboration of the Wisconsin State Journal and the Morgridge Institute for Research.


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