Thread: Earthquakes

Ever been in one? I'm getting rather anxious about what lurks below me, as there have been numerous earthquakes 'round these parts of late.



This is what the last one did in 1700, causing the "Orphan Tsunumi" that was recorded in Japan: "orphan" because it was not preceded by an earthquake.

We're due for another that could cause a lot of damage to the Pacific Northwest of the USA and Vancouver Island.



This "ghost forest" near the mouth of the Copalis River, Washington, was killed by saltwater tides after an earthquake in 1700 caused the land to subside.




A layer of clean sand is sharply bounded by peat and mud
in a pit dug at a marsh just east of Tofino on the west coast
of Vancouver Island. The sand occurs as a sheet that thins
and fines landward and contains marine microfossils. It was
deposited by a landward surge of seawater at the time of the
last great earthquake at the Cascadia subduction zone in
A.D. 1700.






View of Lituya Bay, Alaska from the head of the Bay
looking outwards showing the effects of giant waves





Here's Mount Baker, a familiar US landmark, that I can see everyday from the Canadian side. It's a part of a string of volcanoes that emanate from the subduction zone from central B.C. to California:




Meanwhile:

January 9, 2008 at 9:31 pm

According to the United States Geological Survey (USGS) a large preliminary magnitude 6.4 earthquake has struck off the coast of Oregon in the United States.

The quake struck at 01:37 (UTC) and its epicenter was located 242 kilometers (151 miles) west, northwest of Barview. It registered at a depth of 10 k.m. (6.2 miles).

So far there are no reports of damage, injuries or deaths and no tsunami warning has been issued, but small waves could be locally generated by any possible landslides.

"The magnitude is such that a tsunami is not expected. However, in coastal areas of intense shaking, locally generated tsunamis can be triggered by underwater landslides," said the National Oceanic and Atmospheric Administration's Pacific Tsunami Warning Center in a statement on its website. No further messages will be generated it adds.

Firefighters in Bandon report that they didn't even feel the trembler and police say that no one has yet called to report any quake related incidents. Bandon is also located within 150 miles of the quake's epicenter.

MND: News and Commentary Since 2001 » Large earthquake off the coast of Oregon, US

Closer to home, last week:

Trio of quakes off B.C. coast remarkable, but not alarming says scientist

5 days ago

SIDNEY, B.C. - In earthquake-prone British Columbia, which experiences about 1,500 quakes a year, a preoccupation with The Big One is never far from the surface.

It breaks through almost every time a quake does more than rattle the kitchen glassware. So it wasn't surprising when the airwaves buzzed with Big One talk after three sizable temblors rocked the ocean floor off the West Coast.

A magnitude 6.5 quake was recorded just after 3 a.m. local time last Saturday under the Pacific Ocean south of the Queen Charlotte Islands.

A second, similar-sized quake occurred about 45 minutes later in roughly the same location.
Wednesday morning, a third quake, measured at magnitude 6.1, was traced to the same spot.
Enough to send ripples through quake-sensitive British Columbians who wondered whether this cluster of large shakers might not be a precursor for The Big One.

The answer from a Canadian scientist is no.

Well, probably not.

"These earthquakes don't mean we're any closer to the big earthquake we expect, or that the big earthquake is any further away," says Dr. John Cassidy, part of a team of leading-edge researchers at the Pacific Geoscience Centre near Victoria.

But they do serve as a reminder that coastal B.C. is a very active region where earthquakes occur every day, he says. And once every couple of centuries it gets slammed by a "really big one" - the last an undersea quake in the year 1700.

"It was a magnitude 9 and ruptured the fault from northern Vancouver Island to northern California," says Cassidy.

The biggest quake ever recorded on land in Canada, a magnitude 7.3, struck central Vancouver Island in 1946 at a place called Forbidden Plateau near Campbell River.

The quake, felt as far away as Portland, Ore., and Prince Rupert on B.C.'s North Coast, crumbled chimneys even in Vancouver and sent frightened residents running into the streets, according to Natural Resources Canada account.

Two people died - one drowning when a small boat was capsized by the quake-generated tsunami and another in Seattle from a heart attack.

So the prospect of a very big and very destructive quake is very real, too.

The root of the threat on the West Coast is an area scientists refer to as the Cascadia Subduction Zone, stretching from a fault off the Queen Charlottes off the northern coast to California's infamous San Andreas fault.

To keep the image simple, Cassidy describes two continental plates under the Pacific Ocean moving eastward, being pushed beneath North America's continental plate at a spot in the ocean several hundred kilometres west of Vancouver Island.

Where the plates meet, pressure and friction builds. When they crack or slip, energy is released in the form of earthquakes.

Generally, the larger the magnitude number, the more damage is likely.

But the magnitude scale is logarithmic, not linear, and Cassidy acknowledges this often has people confused, particularly in this case where all three recent quakes were over the magnitude 6 mark.

Going from magnitude 6 to 7, the level of ground shaking goes up by 10 times while the energy release goes up by 32 times. The ground shaking at magnitude 8 is 100 times stronger, and the energy release is 1,000 times stronger, he says.

The trio of plus-6 quakes occurred at the northern tip of the zone, where lower magnitude quakes, while frequent, are more the norm.

Unfortunately, despite sweeping advances in the field, seismologists are still unable to predict where the next devastating quake will occur.

But they are getting a much better handle on the process.

"What we're doing is improving our understanding of where earthquakes occur, how often and, ultimately, how will the ground shake during future earthquakes," says Cassidy.

He sees that as the key, giving engineers and designers the data they need to build bridges, pipelines and buildings to withstand that level of shaking.

"Then it doesn't matter if the earthquake happens tomorrow, or in a year or in 10 years, because your infrastructure will survive," he adds.

"So, it's really the building codes that provide our defence against earthquakes."

Cassidy is realistic enough to admit that predicting earthquakes may never be possible.

But he says scientists are making great advances in their understanding though studies relying on ultra-accurate global-positioning satellite mapping to identify areas where energy is being stored.

"So this is all-new research and is being folded into the national building code of Canada and providing us with, really, a much better defence against earthquakes," he said.

The Canadian Press: Trio of quakes off B.C. coast remarkable, but not alarming says scientist

Seems like a matter of time. Does insurance cover earthquakes/tsunamis or are they considered "acts of God"?

Originally Posted by Happyman

Originally Posted by Deus Ex

I'm in the insurance game & everything is an 'act of God' unless we say otherwise - or the ombudsman steps in

Nice one! Very true -was in the game myself for 17 years

It appears earthquake insurance exists, in some form here:

Earthquake fires could be removed from B.C. home insurance

Last Updated: Monday, January 14, 2008 | 12:12 PM ET

Some lobbyists in the insurance industry want fires caused by earthquakes removed from regular fire insurance as B.C.'s Ministry of Finance revamps the Insurance Act.

Currently, if a house catches fire because of an earthquake it would be covered under normal fire insurance. But, under the new proposal, policy-holders would need to purchase earthquake fire insurance separately.

The Minister of Finance, Carole Taylor, who is overseeing the renovation of the act, told CBC News on Friday no decision on the possible change has been made.

She is concerned the changes may be too complicated for consumers to understand.

"We are looking into all of the suggestions that come to us both from the consumer groups, but also from the insurance bureau," Taylor said.

Chuck Byrne, with the Insurance Brokers Association of B.C., told CBC News the proposal is supported by some in the industry, but not others.

Byrne couldn't say if the proposed change would mean consumers would have to pay more or not.

"If the standard policy was to have that pulled from it, you would think that the standard policy would go down in price," Byrne said. "And then the endorsement, if you chose to add it back on, would be for the fire and the shaking for an earthquake."

The new legislation should be finished this spring.

Right now, about 40 per cent of people in Vancouver don't have earthquake insurance, and if a quake hit the city the economic consequences could be immense, Byrne said.

The tectonic plate movements in the area immediately west of Vancouver in the Juan de Fuca Strait are considered among the most dangerous in the world. Scientists say the Juan de Fuca Plate is gradually sliding underneath its neighbour, the North American Plate.

Eventually, scientists say, this will cause a "subduction earthquake," an incredibly powerful event that could measure up to a magnitude of 9 on the Richter scale.

Based on geological evidence in the region, it's believed that such quakes strike every 300 to 500 years. The last major quake in that zone was Jan. 26, 1700.

Earthquake fires could be removed from B.C. home insurance

Also found this:

Earthquake insurance is a form of property insurance that pays the policyholder in the event of an earthquake that causes damage to the property. Most ordinary homeowners insurance policies do not cover earthquake damage. Most earthquake insurance policies feature a high deductible, which makes this type of insurance useful if the entire home is destroyed, but not useful if the home is merely damaged. Rates depend on location and the probability of an earthquake. Rates may be cheaper for homes made of wood, which withstand earthquakes better than homes made of brick.

As with flood insurance or insurance on damage from a hurricane or other large-scale disasters, insurance companies must be careful when assigning this type of insurance, because an earthquake strong enough to destroy one home will probably destroy dozens of homes in the same area. If one company has written insurance policies on a large number of homes in a particular city, then a devastating earthquake will quickly drain all the company's resources. Insurance companies devote much study and effort toward risk management to avoid such cases.

[edit] California

Earthquake insurance has become a political issue in California, whose residents purchase more earthquake insurance than residents of any other state in the U.S. After the 1994 Northridge earthquake, nearly all insurance companies completely stopped writing homeowners' insurance policies altogether in the state, because under California law (the "mandatory offer law"), companies offering homeowners' insurance must also offer earthquake insurance. Eventually the legislature created a "mini policy" that could be sold by any insurer to comply with the mandatory offer law: only structural damage need be covered, with a 15% deductible. Claims on personal property losses and "loss of use" are limited.

The legislature also created a quasi-public (privately funded, publicly managed) agency called the CEA California Earthquake Authority. Membership in the CEA by insurers is voluntary and member companies satisfy the mandatory offer law by selling the CEA mini policy. Premiums are paid to the insurer, and then pooled in the CEA to cover claims from homeowners with a CEA policy from member insurers. The state of California specifically states that it does not back up CEA earthquake insurance, in the event that claims from a major earthquake were to drain all CEA funds, nor will it cover claims from non-CEA insurers if they were to become insolvent due to earthquake losses. [1]

[edit] Japan

The government of Japan created the "Japanese Earthquake Reinsurance" scheme in 1966, and the scheme has been revised several times since. Homeowners may buy earthquake insurance from an insurance company, usually as an optional rider to a fire insurance policy. Insurers enrolled in the JER scheme who have to pay earthquake claims to homeowners share the risk among themselves and also the government, through the JER. The government pays a much larger proportion of the claims if a single earthquake causes aggregate damage of over about 1 trillion yen (about US $8.75 billion). The maximum payout in a single year to all JER insurance claim filers is 4.5 trillion yen (about US $39.4 billion); if claims exceed this amount, then the claims are pro-rated among all claimants.

Earthquake insurance - Wikipedia, the free encyclopedia

Wow, didn't know England got 20 earthquakes a year...

Earthquake shakes Britain but damages little

Last Updated: 2:29am GMT 28/02/2008

It was, ultimately, a very British earthquake: no collapsed buildings or bridges, no death or mayhem. The strongest tremor to hit the country in almost 25 years shook homes from Dumfries to Dover and Newcastle to Torquay at 12.56am yesterday, causing an initial panic and triggering thousands of calls to the emergency services.


Watch: Residents assess the damage caused to their homes

It did cause one serious injury - when a chimney stack partially collapsed, sending masonry crashing through a roof on to David Bates, 19, a student in Barnsley, leaving him with a suspected broken pelvis.

However, when the dust settled, there was little to show for such a momentous event except a few smashed slates and some bad jokes about the earth moving.

Mr Bates even managed to make light of the unwelcome attention. As he nursed his injuries in hospital, he said what really aggrieved him was missing his local football team's FA Cup clash against Chelsea next week, for which he had a ticket.

Despite yesterday's earthquake measuring 5.2 on the Richter Scale - the biggest since Britain's largest ever onshore tremor, at Nefyn in north Wales, back in July 1984, which measured 5.4 - it was a relative minnow in the international pantheon.

Does insurance cover earthquake damage?
Earthquakes in Britain

Dave Rothery, a volcanologist and earth scientist at the Open University, said the tremor was a million times weaker than the quake that triggered the 2004 Boxing Day tsunami.

But for those who were woken by their homes shaking, it was frightening. Some residents spoke of a roaring sound similar to a train or low-flying aeroplane while others thought a lorry had crashed into their house.

The emergency services said the injury toll could have been much higher had the earthquake hit during the day.

Its epicentre was near Market Rasen in Lincolnshire but tremors were felt for hundreds of miles.
Speaking from his bed at Barnsley General Hospital, Mr Bates said: "Everything started shaking and I don't know why, but I knew it was an earthquake.

"It lasted for several seconds and then it all seemed to stop and I was laying there thinking, 'What do I do now?'

"Then all of a sudden there was a noise like smashing plates as something came crashing through the ceiling. A big piece of concrete fell on me with a big crunch. It was really, really painful."

Michael Steed, a bird keeper in Market Rasen, was woken by the building shaking. "Curiously, all the birds started singing, even though it was 1am," he said. "But they stopped after about a quarter of an hour when they realised it was still night."


Earthquake hotspots- click to enlarge

One fire officer attending a chimney collapse in Gainsborough, Lincs - one of the worst-affected areas - said: "We're lucky it happened when most people were in bed. If it had happened in the afternoon we could have been looking at a lot more casualties as people would have been walking past."

The majority of damage was to chimneys, roof tiles and caused by falling masonry. Insurers estimated the cost at £30 million.

Shona Forsyth, 39, whose chimney collapsed into Portland Terrace, Gainsborough, said: "It was scary. I had just finished feeding my 15-month-old daughter and there was this really loud rumbling. The house was shaking.

"I looked out the window and thought at first a lorry had crashed into the house. We didn't realise what had happened until we saw the news. Everyone was out in the street in their dressing gowns."

In Derby, Helen Sowden, 41, was shaken from her bed. "We were woken by this roar and huge rumbling and the room started shaking.

"My husband and I shot out of bed wondering what was happening. We realised pretty quickly it must have been an earthquake but for a few seconds it was really frightening."

Grace Davis and her son, Marcus Kelly, were thankful to be woken because it alerted them to a fire in their flat in Edgbaston, Birmingham.

Mrs Davis said: "It was only when Marcus got up to see what was going on that he saw smoke billowing from underneath the kitchen door. We are very lucky."

Britain is hit by 200 quakes each year but only about 20 are felt by the public.

Earthquake shakes Britain but damages little - Telegraph

Meanwhile in these here parts:

Virtual Mega-quake Shows Earthquake Could Inflict Major Damage On Pacific Northwest US

ScienceDaily (Feb. 28, 2008) — On January 26, 1700, at about 9 p.m. local time, the Juan de Fuca plate beneath the ocean in the Pacific Northwest suddenly moved, slipping some 60 feet eastward beneath the North American plate in a monster quake of approximately magnitude 9, setting in motion large tsunamis that struck the coast of North America and traveled to the shores of Japan.


Scientists used a supercomputer-driven "virtual earthquake" to explore likely ground shaking in a magnitude 9.0 megathrust earthquake in the Pacific Northwest. Peak ground velocities are displayed in yellow and red. The legend represents speed in meters per second (m/s) with red equaling 2.3 m/s. Although the largest ground motions occur offshore near the fault and decrease eastward, sedimentary basins lying beneath some cities amplify the shaking in Seattle, Tacoma, Olympia, and Vancouver, increasing the risk of damage.

Since then, the earth beneath the region – which includes the cities of Vancouver, Seattle and Portland -- has been relatively quiet. But scientists believe that earthquakes with magnitudes greater than 8, so-called “megathrust events,” occur along this fault on average every 400 to 500 years.

To help prepare for the next megathrust earthquake, a team of researchers led by seismologist Kim Olsen of San Diego State University (SDSU) used a supercomputer-powered “virtual earthquake” program to calculate for the first time realistic three-dimensional simulations that describe the possible impacts of megathrust quakes on the Pacific Northwest region. Also participating in the study were researchers from the San Diego Supercomputer Center at UC San Diego and the U.S. Geological Survey.

What the scientists learned from this simulation is not reassuring, as reported in the Journal of Seismology, particularly for residents of downtown Seattle.

With a rupture scenario beginning in the north and propagating toward the south along the 600-mile long Cascadia Subduction Zone, the ground moved about 1 ½ feet per second in Seattle; nearly 6 inches per second in Tacoma, Olympia and Vancouver; and 3 inches in Portland, Oregon. Additional simulations, especially of earthquakes that begin in the southern part of the rupture zone, suggest that the ground motion under some conditions can be up to twice as large.

“We also found that these high ground velocities were accompanied by significant low-frequency shaking, like what you feel in a roller coaster, that lasted as long as five minutes – and that’s a long time,” said Olsen.

The long-duration shaking, combined with high ground velocities, raises the possibility that such an earthquake could inflict major damage on metropolitan areas -- especially on high-rise buildings in downtown Seattle. Compounding the risks, like Los Angeles to the south, Seattle, Tacoma, and Olympia sit on top of sediment-filled geological basins that are prone to greatly amplifying the waves generated by major earthquakes.

“One thing these studies will hopefully do is to raise awareness of the possibility of megathrust earthquakes happening at any given time in the Pacific Northwest,” said Olsen.

Another component is a model of the earthquake source from the slipping of the Juan de Fuca plate underneath the North American plate. Making use of the extensive measurements of the massive 2004 Sumatra-Andeman earthquake in Indonesia, the scientists developed a model of the earthquake source for similar megathrust earthquakes in the Pacific Northwest.

“We found that the magnitude 9 scenarios generate peak ground velocities five to 10 times larger than those from the smaller magnitude 8.5 quakes.”

Virtual Mega-quake Shows Earthquake Could Inflict Major Damage On Pacific Northwest US

Can be a disturbing experience. When first assigned to Edwards AFB I though I heard the Atlas rocket test stands running - way to early in the morning for regular testing - and they were 35 miles away on the other side of the base.

When my foggy head had cleared somewhat I realized I was on the floor. Yep, the Silmar Quake had actually thrown me out of bed, weird for sure and that quake was centered 50 miles (as the crow flies) away.

E. G.