Live Science has a story about the tectonic plates along the West Coast of the United States. The plate named Juan de Fuca (pronounced "wahn de fyoo-kuh"), which is about the size of Michigan, has a large tear. The plate is located off the coast of Northern California extending north past Oregon, Washington, up to even British Columbia. The size of the tear in this plate probably explains earthquakes off the shore of California and the volcanoes in Oregon. The research on this appeared in a paper in the journal Geophysical Research Letters back in July.
"Where other people had debated whether or not it [the tear] was there, we can pretty confidently say that it's real," study lead researcher William Hawley, a doctoral student in the Earth and Planetary Science Department at the University of California, Berkeley, told Live Science.
The Juan de Fuca plate is long, stretching about 600 miles (1,000 kilometers) along the Pacific Northwest coast, from Vancouver Island, Canada, to Cape Mendocino, California. "No part of it is above the water. It's a total oceanic plate" that's subducting, or diving beneath another plate, in this case the North American plate (a continental plate), Hawley said.
From 2011 to 2015, scientists boated out over different parts of the Juan de Fuca plate, dropped ocean-bottom seismometers underwater and let these sensors collect seismic data from earthquakes all over the world for a year.
When the year was up, the researchers returned, fished up the seismometers and uploaded the data, which allowed them to create a tomography, or layout, of the plate. Then, they deployed the devices to other spots on the plate. "It was an enormous community effort," Hawley said.
The data from these seismometers showed how seismic waves traveled through the plate, which, in turn, revealed information about the plate's composition and varying temperatures. One region under central Oregon showed a gap in high-velocity seismic waves, which Hawley interpreted to be the hole.
But why does this hole exist? Hawley and study co-researcher Richard Allen, director of the Berkeley Seismological Laboratory, hypothesized that there is a weak zone in the Juan de Fuca plate that exists because the plate formed at two overlapping ridge segments. As this weakened zone of the oceanic plate goes under the continental plate, it unzips from the bottom up (from the underside upward), creating a gash.
