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Developing Story: Seismic swarm in progress between Cascadia and San Andreas Faults

Four Magnitude-3.4 and larger quakes have struck in two hours, all south of Cape Mendocino, and west of the town of Petrolia, California. Based on the earthquake locations and their focal mechanisms (both by the USGS), the swarm appears to be occurring on a right-lateral reverse fault that connects the northernmost San Andreas-Mendocino Fracture Zone with the shallow portion of the Cascadia Megathrust (as shown by the black half- arrows in the map).

This area has highest quake rate in all of California (http://temblor.net/earthquake-insights/m6-5-earthquake-stresses-offshore-san-andreas-fault-aka-mendocino-fault-zone-1917/). That’s because the two fastest-slipping faults in the western U.S. join, or nearly join, here. It’s also because the bend in both the San Andreas and Cascadia Faults mean that the crust here is being crushed, distorted, and fractured. This distortion cannot be accommodated solely along the great faults, and so there is a plethora of small faults like this one that distribute the stress.

What this event means for the Cascadia and San Andreas Faults is unknown, but it is certainly a swarm to watch.

Source: http://temblor.net/earthquake-insights/developing-story-seismic-swarm-in-progress-in-cascadia-8323/

3.8 magnitude earthquake hits area northwest of Hampton, NB

Earthquakes Canada has confirmed a 3.8 magnitude earthquake hit an area 17 kilometres northwest of Hampton in southern New Brunswick this morning.

Nick Ackerley, an Earthquakes Canada seismologist, said the earthquake happened at 9:49 a.m. AT, approximately 17 kilometres west-northwest of Hampton and 35 kilometres north of Saint John.

Its preliminary magnitude was reported as 3.7, but Earthquakes Canada upgraded it later Thursday.

It was an “intraplate earthquake,” a type that happened inside the tectonic plate, as opposed to an interplate earthquake, which occurs in areas at the edge of a tectonic plate.

“The causes include things like long-dormant faults from previous mountain-building episodes, and glacial rebound,” Ackerley said.

“This part of Canada was under glaciers until about 10,000 years ago, and when the weight of the ice was lifted off, the Earth is slowly springing back, and that causes stress in the crust of the Earth.”

The government of New Brunswick tweeted officials are aware and are monitoring the earthquake.

Earthquakes Canada has confirmed a 3.8 magnitude earthquake hit an area 17 kilometres northwest of Hampton in southern New Brunswick this morning.

Nick Ackerley, an Earthquakes Canada seismologist, said the earthquake happened at 9:49 a.m. AT, approximately 17 kilometres west-northwest of Hampton and 35 kilometres north of Saint John.

Its preliminary magnitude was reported as 3.7, but Earthquakes Canada upgraded it later Thursday.

It was an “intraplate earthquake,” a type that happened inside the tectonic plate, as opposed to an interplate earthquake, which occurs in areas at the edge of a tectonic plate.

“The causes include things like long-dormant faults from previous mountain-building episodes, and glacial rebound,” Ackerley said.

“This part of Canada was under glaciers until about 10,000 years ago, and when the weight of the ice was lifted off, the Earth is slowly springing back, and that causes stress in the crust of the Earth.”

The government of New Brunswick tweeted officials are aware and are monitoring the earthquake.

Hughes said there’s no visible damage to her home.

Lee Jacobs said she and her husband heard a low rumbling that lasted for several seconds before the house starting “shaking violently.”

“I said, ‘What is that?’ And as soon as I said those words, the house started shaking. You could hear the sound before the shaking started.”

She called the earthquake an “unnerving” experience

3.8-magnitude quake considered minor

A 3.8 magnitude quake “could be widely felt,” according to Ackerley, depending on the depth at which it occurred.

That being said, a 3.8 magnitude is still considered to be a minor earthquake and unlikely to cause damage.

Earthquakes, while rarely severe, aren’t unheard of in New Brunswick.

In the spring of 2018, Earthquakes Canada recorded a “swarm” of 22 minor quakes on the western edge of the province near McAdam, a village also also rattled by a 3.3 magnitude earthquake in 2016.

In November 2016, a magnitude 3.1 earthquake was recorded 23 kilometres west-northwest of Miramichi.

But the last major earthquake, a magnitude 5, hit the Miramichi area in the 1980s, the largest earthquake to have affected the Maritimes since 1929.

Source: https://www.cbc.ca/news/canada/new-brunswick/earthquake-hits-northwest-of-hampton-1.4972818

A low-intensity hum near Vancouver Island may help predict the next killer earthquake

There has not been a major earthquake in the Cascadia subduction zone since 1700. But every year or so, there is a month-long ‘slow slip’ of tectonic plates.

It is well known that, off the coast of Vancouver Island, the massive undersea Juan de Fuca tectonic plate is slowly sliding under the larger North American plate, putting the west coast of Canada at grave risk of a megathrust earthquake and resulting tsunami.

What is lesser known about this process is the massive amount of energy that is unaccounted for, and might be building silently toward catastrophe. Newly published research based on artificial intelligence claims to have found it in a constant, low, background tremor, and, with it, a new way of predicting when the next big one might hit.

There has not been a major earthquake in what is known as the Cascadia subduction zone since about 9 p.m. on Jan. 26, 1700, long before Europeans first landed on Vancouver Island. The event is moderately well known to historians, however, for two reasons.

One is the oral histories and archeological remains of the various First Nations whose villages were swamped by a tsunami. Storytellers began to speak of dwarfs in the mountains who danced around a drum, causing the earth to shake and waters to rise. Others described a sea battle between a thunderbird and a whale that caused “a shaking, jumping up and trembling of the earth beneath, and a rolling up of the great waters,” according to research by Alan McMillan, who studies the archeology and ethnography of Vancouver Island First Nations at Simon Fraser University.

The other reason is that the tsunami also went the other way, westward to Japan, making landfall the next day, killing hundreds and sinking boats.

Ever since, Cascadia has been relatively quiet. But every year or so, there is a roughly month-long “slow slip,” when the North American plate lurches southwesterly over the Juan de Fuca plate.

This slip can account for as much as half of the total relative motion of the tectonic plates, as measured by displacement on the surface. It is usually accompanied by bursts of tremors, but the physics of “slow slip” is not well understood. It only occurs in some regions of the fault line between the plates, for example, while others appear to be “locked,” and only move in megathrust events.

This slip has been observed in advance of major earthquakes, which suggests it might be part of the process that causes them, according to a new paper by Bertrand Rouet-Leduc and Claudia Hulbert of the Los Alamos National Laboratory in New Mexico.

There is also a strange discrepancy between the amount of surface movement as measured by global positioning systems and the amount of energy measured by seismographs in tremors.

Somewhere in this process, a vast amount of energy has gone missing.

The key to finding it was to apply the tools of supervised machine learning, a kind of artificial intelligence that can separate a real signal from background noise. In a newly published paper, the researchers claim to have found that the Cascadia subduction zone is “continuously broadcasting a low-amplitude, tremor-like signal,” and that this low amplitude hum from the depths of the Earth “may account for most of this missing energy.”

Recognizing what this hum reveals about fault line physics might lead to something like an early warning system that “may prove useful in determining if and how a slow slip may couple to or evolve into a major earthquake,” the authors write in the journal Nature Geoscience.

They used seismic data from the Canadian National Seismograph Network and global positioning data from stations in the Western Canada Deformation Array, processed by the United States Geological Survey.

They found the Juan de Fuca plate is moving under the North American plate at around four centimetres a year as the North American plate slips over it. The highest slip speed for the North America plate, moving in the other direction, was also around four centimetres a year, which means that the transition zone between the plates — coastal British Columbia, basically — was slipping at around eight centimetres a year.

“The continuous tremor-like signal we identify tracks the slow slip rate, apparently at all times, and so provides real-time access to the physical state of the slowly slipping portion of the megathrust,” the authors write. “As the slow earthquakes transfer stress to the adjacent locked region where megaquakes originate, careful monitoring of this tremor-like signal may provide new information on the locked zone, with the potential to improve earthquake hazard assessment in Cascadia.”

Source: https://nationalpost.com/news/canada/a-strange-low-intensity-hum-near-vancouver-island-may-help-predict-when-the-next-killer-earthquake-will-strike

Ontario town rattled by ‘mining-related’ earthquake

It wasn’t a particularly strong quake, but it didn’t need to be for Kirkland Lake residents to feel the tremor on Wednesday night [December 12th, 2018] — it happened right underneath their feet.

According to Earthquakes Canada, the magnitude 3.2 earthquake was centred almost directly under the city, 2 km west-southwest of town, at a depth of 1.5 km. More than 100 people reported to Natural Resources Canada that they felt the quake, which struck at 11:16 EST Wednesday night. Weather Network viewers reported hearing a “loud blast that shook a lot of homes” at the time the quake was recorded.

Earthquakes Canada lists the tremor as ‘mining-related’, although no confirmation has been released. Local resident Jeff Wilkinson told CTV News he was concerned it might have been a fracture related to mining. “As you may know,” Wilkinson told CTV, “we have had some fatal rockbursts in this area, so we’re all sort of wondering whether it has happened again.” A rock burst is a sudden, sometimes explosive, fracture that can happen in deep mines. The rock surrounding a mine shaft is under tremendous pressure from the rock surrounding it; sometimes this pressure can cause the rock surrounding the shaft to give way.

DOES MINING CAUSE EARTHQUAKES, OR IS IT THE OTHER WAY AROUND? 

There has definitely been a lot of coverage of fracking-related earthquakes in recent years, as geologists point to the oil-extraction process for the rising number of quakes in places like Ohio and Oklahoma. Earthquakes related to mineral mining are a slightly different animal, however.

As happens with rock bursts, since mining leaves empty spaces that change the balance of pressure on the surrounding rocks, it’s not unusually to get minor earthquakes related to the collapse of excavated regions. The excavation process itself can also result in events that register on the seismometer. According to a report from the Canadian Hazards Information Service, “Literally hundreds of [mining-induced activity] blasts are recorded and identified by the project on a yearly basis.”

Sometimes it’s a case of ‘the chicken and the egg’, however.

A lot of the minerals that people mine for are actually largely found along fault lines — gold being among them. As Daniel Jaska, of the Geoscience Australia Earthquake Alert Centre, put it talking to ABC, “we have mining because of earthquakes.”

“[Minerals like gold] are [along faults] because when and earthquake occurs, there is generally a flow of water or liquid that interacts with the rocks,” said Jaska, “and over many millions of years forms minerals.”

While seismic activity in central Canada tends to be fairly low, thanks to a lake of tectonic plate interactions in the area, there are ‘weak zones’ within plates that are subject to shifting when stress builds up in the interior of a plate, thanks to constant pushing at its edges.

Source: https://www.theweathernetwork.com/news/articles/earthquake-felt-in-kirkland-lake-officials-believe-mining-related-gold-mine-mining-seismicity-rockburst/119806

Powerful quakes buckle Alaska roads, briefly trigger tsunami warning

Back-to-back earthquakes measuring 7.0 and 5.8 rocked buildings and shattered roads Friday morning, November 30, 2018 in Anchorage, Alaska, sending people running into the streets and briefly triggering a warning to residents in Kodiak to flee to higher ground for fear of a tsunami.

The warning was lifted a short time later. There were no immediate reports of any deaths or serious injuries.

The U.S. Geological Survey said the first and more powerful quake was centred about 12 kilometres north of Anchorage, Alaska’s largest city, with a population of about 300,000. People ran from their offices or took cover under desks.

Cracks could be seen in a two-story downtown Anchorage building, and photographs posted to social media showed fractured roads and collapsed ceiling tiles at an Anchorage high school. One image showed a car stranded on an island of pavement, surrounded by cavernous cracks where the earthquake split the road.

Cereal boxes and packages of batteries littered the floor of a grocery store, and picture frames and mirrors were knocked from living room walls.

People went back inside after the first earthquake struck, but the 5.8 aftershock about five minutes later sent them running back into the streets.

A tsunami warning was issued for the southern Alaska coastal areas of Cook’s Inlet and part of the Kenai peninsula. Kodiak police on Kodiak Island warned people in the city of 6,100 to “evacuate to higher ground immediately.”

The National Weather Service Seattle tweeted a tsunami warning is in effect for Cook Inlet, but it is not expected to affect Washington or B.C.

Anchorage lawyer Hank Graper was driving when the quake struck. He first thought his vehicle had a flat tire, then thought it was exploding. He realized it was an earthquake after he saw traffic poles swaying.

Graper called it the most violent earthquake he’s experience in his 20 years in Anchorage.

David Harper was getting some coffee at a store when the low rumble began and intensified into something that sounded “like the building was just going to fall apart.” Harper ran to the exit with other patrons.

“The main thought that was going through my head as I was trying to get out the door was, ‘I want this to stop,”‘ he said.

Harper said the quake was “significant enough that the people who were outside were actively hugging each other. You could tell that it was a bad one.”

Thrown from bathtub

In Kenai, north of Anchorage, Brandon Slaton was alone at home and soaking in the bathtub when the earthquake struck. Slaton, who weighs 209 pounds, said it created a powerful back-and-forth sloshing in the bath, and before he knew it, he was thrown out of the tub by the waves.

His 55-kilogram mastiff panicked and tried to run down the stairs, but the house was swaying back and forth so much that she was thrown off her feet and into a wall and tumbled to the base of the stairs.

“It was anarchy. There’s no pictures left on the walls, there’s no power, there’s no fish tank left. Everything that’s not tied down is broke,” Slaton said.

Slaton ran into his son’s room after the shaking stopped and found his fish tank shattered and the fish on the closet floor, gasping for breath.

He grabbed the Betta fish and put it in another bowl. He says the area was eerily quiet. His children’s school was evacuated.

Alaska averages 40,000 earthquakes per year, with more large quakes than the other 49 states combined. Southern Alaska has a high risk of earthquakes due to tectonic plates sliding past each other under the region.

According to the U.S. Geological Survey, the Pacific plate is sliding northwestward and plunges beneath the North American plate in southern Alaska, the Alaska Peninsula and the Aleutian Islands.

On March 27, 1964, Alaska was hit by a magnitude 9.2 earthquake, the strongest recorded in U.S. history, centred about 120 kilometres east of Anchorage. The quake and the tsunami it triggered claimed about 130 lives.

Source: https://www.cbc.ca/news/canada/north/earthquake-anchorage-1.4927624

Earthquake near Fort St. John ‘very likely’ caused by fracking

An earthquake that struck northeastern B.C. on Thursday evening was “very likely” caused by fracking, a preliminary investigation has found.

Earthquakes Canada said the quake had a preliminary magnitude of 4.5, with the epicentre about 16 kilometres southwest of Fort St. John.

It hit around 5 p.m. PT, followed by another tremor of similar magnitude, classified as an aftershock, less than an hour later.

The Geological Survey of Canada and the B.C. Oil and Gas Commission launched an investigation to figure out what caused the tremor.

On Friday, a statement said they had confirmed there was active fracking happening near the epicentre when the quake struck.

“The likelihood this was induced … there’s a very high correlation,” said Honn Kao, seismology research scientist with the Geological Survey of Canada.

Kao stressed the link was a preliminary finding and more investigation is required before the agency confirms the quake was “100 per cent” a result of fracking — but said it’s “very likely” that’s the case.

Hydraulic fracturing — or fracking — is the process of injecting water, sand and other chemicals underground at a very high pressure to fracture shale rock, in order to extract natural gas.

Western Alberta and northeast B.C. have a high rate of fracking-induced earthquakes, according to a study from the University of Alberta.

Tremor ‘lightly felt’

People in Fort St. John, as well as Taylor, Chetwynd and Dawson Creek, reported feeling the earthquake on social media, but there are currently no reports of damage.

Kao said early data suggests the quake had a relatively shallow depth, which is likely why the quake was widely felt.

“This is certainly an event that has been felt quite a bit by the local residents,” Kao said. “Although this is a significant event for the region, I don’t think it’s going to cause significant damage.”

According to the U.S. Geological Survey, the quake had a preliminary magnitude of 4.2.

Source: https://www.cbc.ca/news/canada/british-columbia/earthquake-fort-st-john-fracking-1.4927898

4.2-magnitude earthquake strikes near Fort St. John

An earthquake struck an area in northeastern B.C. close to Fort St. John on Thursday, November 29, 2018 after 5 p.m. PT.

According to the U.S. Geological Survey, the quake had a preliminary magnitude of 4.2 and the epicentre was 22.4 kilometres southeast of Fort St. John.

People in Fort St. John, as well as Taylor, Chetwynd and Dawson Creek reported feeling the earthquake on social media, but there are currently no reports of damage.

Honn Kao, a research scientist with the Geological Survey of Canada, said early data suggests the quake had a relatively shallow depth which is likely why the quake was widely felt.

“This is certainly an event that has been felt quite a bit by the local residents,” Kao said. “Although this is a significant event for the region I don’t think it’s going to cause significant damage.”

Hydraulic fracturing in the area

Although it is unconfirmed what caused this earthquake, Kao said the B.C. Oil and Gas Commission is investigating if the quake is related to hydraulic fracturing operations in the area.

Hydraulic fracturing — or fracking — is when water, sand and other chemicals are injected underground at a very high pressure to fracture shale rock deep underground in order to extract natural gas.

“They will have to link the location and time of this event to the injection operations nearby,” Kao said.

This area of the country — western Alberta and northeast B.C. — has a high rate of fracking-induced earthquakes, according to a study from the University of Alberta.

Source: https://www.cbc.ca/news/canada/british-columbia/4-2-magnitude-earthquake-strikes-near-fort-st-john-1.4926772

Another earthquake in B.C., breaking down this latest rumble

Another earthquake was measured west of Vancouver Island on October 31st, just shy of a magnitude 5.0 on the Richter scale. Is it another earthquake related to the more powerful episodes back in October?

How many earthquakes do you think have occurred in British Columbia over the past month? 10? 20? 50? We’ve entered quite a tectonically active period.

When reviewing the data, over 80 earthquakes have been measured by sensitive seismometers, but only a couple have been felt. That’s the reality of the plate tectonics around British Columbia, with major plate boundaries being offshore.

The earthquake on the evening of October 31st is a distant cousin of the recent uptick in earthquake activity along a specific fault line, not associated with the Cascadia subduction zone. This was likely an aftershock on the series of greater than magnitude 6.0 earthquakes located on the Sovanco fault. This specific transform fault boundary moves by plates sliding in opposite directions. In this case, the motion is related to the movement of the Explorer and Pacific plates.

DO WE WORRY?

No. But, The ‘big one’ may happen 5 minutes from now, 5 years, or it could be well over 100 years away. From a preparedness standpoint, expecting the earthquake sooner, rather than later will ensure we’re ready to act when the inevitable big shake occurs. A mega-thrust earthquake is one that features a disastrous magnitude 9.0 or greater energy release, but another likely scenario is a weaker, more shallow earthquake under Vancouver Island, or even the Lower Mainland.

For more please refer to the following link (which includes excellent video breakdowns of the tectonic plates movement):

Source: https://www.theweathernetwork.com/news/articles/earthquake-british-columbia-aftershock-vancouver-island-powerful-earthquake-october-vancouver/116148