California earthquake: Tsunami warning canceled after 7.0-magnitude quake
A 7.0-magnitude earthquake struck off California on Thursday morning, briefly triggering a tsunami warning for the coast of Northern California and southern Oregon.
The quake occurred at around 10:44 a.m. and originated about 62 miles west of Ferndale, California, according to the U.S. Geological Survey.
The tsunami warning was issued for coastal areas from Davenport, California, to the border between Douglas and Lane counties in Oregon. The Tsunami Warning Center canceled the warning at about 11:55 a.m.
In Humboldt County, the area on land closest to the epicenter, about 10,000 people lost power, but no injuries or deaths were reported.
Some Californians scrambled to get to higher ground after today’s tsunami warning was issued, but a damaging wave never materialized. That sequence of events suggests that the warning system needs improvement, said Lori Dengler, an expert on tsunamis and the Mendocino fault zone, where this quake occurred.
The U.S. Tsunami Warning Center issued the tsunami alert at 10:49 a.m. PT, then canceled it more than an hour later, at 11:54 a.m. PT.
“We need to work hard at reducing unnecessary alerts,” said Dengler, an emeritus professor in geology at California State Polytechnic University, Humboldt. “We need to know within 5 to 10 minutes if a tsunami was produced, and at present, it was kind of crazy having a tsunami warning in place for so long.”
NOAA uses a network of buoys and seafloor sensors, called DART, to help detect tsunamis. Dengler said the system needs to be expanded to give forecasters a better chance of receiving the data they need to make quicker and more reliable decisions about tsunami forecasts.
“The closest DART systems are hundreds of miles away” from today’s earthquake epicenter, Dengler said. “You really need more ocean bottom instruments to detect what’s happening near the source quickly.”
Today’s earthquake occurred in what has historically been the most seismically active part of California, according to Lucy Jones, a seismologist at the California Institute of Technology.
Jones said the region offshore of Northern California, where today’s temblor struck, has recorded more 7.0-magnitude earthquakes than anywhere else in the state.
The reason for all the seismic activity is because that spot is where three different tectonic plates — the North American plate, the Pacific plate and the Juan de Fuca plate — come together. Today’s quake occurred because of horizontal motion between the Juan de Fuca plate and the Pacific plate, she said.
“But when you have three plates coming together with a lot of motion, it gets very complicated and you end up with a lot of earthquakes,” Jones said.
Still, earthquakes that strike in this region do not tend to cause much damage.
“These earthquakes are offshore, so nobody’s right on top of it,” Jones said. “And the shaking really does die off very quickly.”
