Seismic activity

4.0 earthquake rattles residents in Los Angeles, California

The Southern California coastline felt a "real good jolt" yesterday at about 1 p.m. A 4.0 magnitude earthquake rumbled just off the coast of the Palos Verdes Peninsula.

Latinos Post,

17 May, 2013

No serious problems were reported in relation to the earthquake, though the shake-up certainly was frightening. The Los Angeles County Sheriff's Department noted that they were currently checking up on "critical facilities" but believed everything to be functioning.

The earthquake could be felt from Huntington Beach all the way to Playa del Ray. The epicenter of the quake was located six miles south of Point Fermin in the Pacific Ocean.

Angela Butts-Chester, 41, has an office in downtown Long Beach and reported that she felt a strong shake while working at her computer. The initial jolt was followed by about five seconds of swaying as the building maintained balance.

"It was like if someone were to bump you in the store and you're taken off guard," she said. "It really got my attention. I sat there for a minute and said, 'Oh, OK, never mind. It's over.'"

Butts-Chester wasn't the only one to deal with the earthquake while at work. Hostess Nikki Scotti was on duty at Nelson's in Ranchos Palos Verdes when she felt the quake. Scotti said she was talking with a customer at the time and attempted to distract them so they wouldn't be frightened.

"They still noticed," she said with a laugh. "For the most part, everyone just stopped where they were."

Others have reported feeling the quake as well, though again, did not seem to think much of it. Earthquakes are generally not very dangerous unless they are closer to a magnitude 6.0 or 7.0 or are located near possible avalanche and mudslide locations.

Moderate 5.1 magnitude earthquake ripples through Toronto, Canada

Huffington Post,

17 May, 2013

TORONTO — A 5.2 magnitude earthquake centered northwest of Ottawa rattled buildings Friday in Ontario and Quebec and was felt across upstate New York from Buffalo to the Vermont border.

Canada's government agency that monitors earthquakes said the quake it registered a 5.2-magnitude temblor with an epicenter located about 11 miles (17 kilometers) northeast of Shawville, Quebec, about an hour's drive outside Canada's capital.

It was felt as far west as Toronto, Canada's largest city, but no damage was immediately reported.

Twitter erupted with reports of buildings shaking in Ottawa for several seconds. Ontario's premier, who lives in Toronto, tweeted that her house was shaking.

Ontario Provincial Police in Arnprior, Ontario, not far from the epicenter, say they have received no reports of damage. Local media outlets in northern New York say people in communities along the St. Lawrence River and as far east as Lake Champlain on New York-Vermont border reported feeling their homes shake.

There are also reports from residents of Buffalo and surrounding suburbs who say they felt their houses sway and the ground shake for less than one minute. Rochester and Syracuse media outlets also report that the quake was felt in those areas.

The original report said a 4.8-magnitude quake was centered near the town of Braeside, Ontario.

Is a massive Cascadia earthquake on the horizon?

Futurity,

16 May, 2013

The lack of local documentation has made studying this historic event challenging. New work provides a finer-grained portrait of this earthquake and the changes in coastal land level it produced, enabling modelers to better prepare for future events. The research was published in the Journal of Geophysical Research: Solid Earth.

The Cascadia Subduction Zone runs along the Pacific Northwest coast of the United States to Vancouver Island in Canada. This major fault line is capable of producing megathrust earthquakes 9.0 or higher, though, due to a dearth of observations or historical records, this trait was only discovered within the last several decades from geology records.

The 1700 Cascadia event was better documented in Japan than in the Americas. Records of the “orphan tsunami”—so named because its “parent” earthquake was too far away to be felt—gave earth scientists hints that this subduction zone was capable of such massive seismic activity. Geological studies provided information about the earthquake, but many critical details remained lost to history

“Previous research had determined the timing and the magnitude, but what we didn’t know was how the rupture happened,” says Benjamin Horton, associate professor and director of the Sea Level Research Laboratory in the department of earth and environmental science at the University of Pennsylvania. “Did it rupture in one big long segment, more than a thousand kilometers, or did it rupture in parcels?”

To provide a clearer picture of how the earthquake occurred, Horton and his colleagues applied a technique they have used in assessing historic sea-level rise. The team traveled to various sites along the Cascadia subduction zone, taking core samples from up and down the coast and working with local researchers who donated pre-existing data sets.

The researchers’ targets were microscopic fossils known as foraminifera. Through radiocarbon dating and an analysis of different species’ positions with the cores over time, the researchers were able to piece together a historical picture of the changes in land and sea level along the coastline. The research revealed how much the coast suddenly subsided during the earthquake, which infers how much the tectonic plates moved during the earthquake.

“What we were able to show for the first time is that the rupture of Cascadia was heterogeneous, making it similar to what happened with the recent major earthquakes in Japan, Chile, and Sumatra,” Horton says.

This level of regional detail for land level changes is critical for modeling and disaster planning.

“It’s only when you have that data that you can start to build accurate models of earthquake ruptures and tsunami inundation,” Horton says. “There were areas of the west coast of the United States that were more susceptible to larger coastal subsidence than others.”

The Cascadia subduction zone is of particular interest to geologists and coastal managers because geological evidence points to recurring seismic activity along the fault line, with intervals between 300 and 500 years. With the last major event occurring in 1700, another earthquake could be on the horizon. A better understanding of how such an event might unfold has the potential to save lives.

“The next Cascadia earthquake has the potential to be the biggest natural disaster that the Unites States will have to come to terms with—far bigger than Sandy or even Katrina,” Horton says. “It would happen with very little warning; some areas of Oregon will have less than 20 minutes to evacuate before a large tsunami will inundate the coastline like in Sumatra in 2004 and Japan in 2011.”

The National Science Foundation, the United States Geological Survey, and the University of Victoria funded the research.