In Seattle a tsunami from the coastal earthquake should be pretty subdued because of the damping effect of the Sound. However along the coast it will be a different story.

The next time you are at the beach you should ask the question, "If the big subduction zone earthquake hit now, what would I do?" Outline a strategy beforehand.

After the shaking stops there will be about fifteen to twenty minutes to get to higher ground before the tsunami hits. Along most of the Washington coast there is high ground within reach. However, twenty minutes is not much time, so do not spend time grabbing valuables. Head for the hills!

The Japanese quake had a 12+ meter tsunami in places. We could expect as much on the coast. The average telephone pole is about 20 feet tall. Try to get at least two telephone poles height above high tide. In some places even that might not be high enough.

Lowlands will be inundated. Houses and other buildings will be destroyed.

For those planning a vacation at a NW beach, required reading should be: http://www.ess.washington.edu/tsunami/index.html.

It may not be so easy in places like Ocean Shores, Westport and Long Beach. Even though the tsunami evacuation routes are clearly marked, only the first ones in line will make it out in a worst case scenario. And that assumes the bridges are still intact.

For accounts of what happened during the tsunami in Chile in 1960: http://pubs.usgs.gov/circ/c1187/
This gives accounts of what did and did not work to survive.

So, enjoy your next beach holiday!

"Is Fukushima worse than Chernobyl?" is a bit like asking "Are the Mariners a bigger disaster than the Seahawks?" Both are disasters, but in different ways.

First, let's acknowledge the similarities.

Both the Chernobyl disaster and the Fukushima disaster have resulted in radioactive elements leaking out of containment, into the environment. We know very little--at this time--how much radioactive material has leaked out of the Fukushima complex; for Chernobyl we have some information.The Iodine-131 that leaked out of the Chernobyl disaster has been blamed for about 4000 incidents of Thyroid cancer--primarily in children who ate radioactive iodine-contaminated milk, from cows that ate the Iodine-131 that leaked from Chernobyl.

Now, the differences:

Unlike after Chernobyl--and despite this event occuring in the context of a much larger disaster--for Fukushima, those most at risk of injury from Iodine-131 are being provided non-radioactive iodine in pill form, to protect against this possible injury.

The Chernobyl plant had a design that resulted in rapid failure (in the matter of seconds) when the coolant water was lost. In contrast, the Fukushima reactors failed slowly, over the course of hours and days--allowing time for emergency responders to anticipate and prepare for the concequences of the failures. At Chernobyl, only one reactor (in a complex of several) failed. At Fukushima, several reactors have failed, and there is the added (and potentially more serious problem) of damage to nuclear waste storage pools.

Due to a terrible flaw in the Chernobyl reactor design, a massive explosion distributed the leaking radioactive elements over a gigantic geographic area--including most of Western Europe, aside from the Iberian peninsula. In contrast, the Fukushima explosions have been comparatively tiny, steam explosion and hydrogen gas fires.

While damaged, the Fukushima reactors have both primary and secondary containment buildings to help block or slow the leaks into the environment. Chernobyl had no such containment buildings, with one hastily constructed by workers subjected to high radiation levels.

The Fukushima disaster a terrible accident, with short- and long-term concequences for those who live around the plants. Until more information comes out, and we know if the struggles ongoing at the plant succeed in containing the radiation, we won't know how to compare the ultimate effects of this disaster to those in the past.

Just to expound a little more, the Richter magnitude is a measure of the intensity of the ground motion (i.e. the shaking) of an earthquake, whereas the Moment magnitude is a measure of the total energy released in a quake.

When they devised the Moment magnitude scale to replace the Richter scale, they intentionally made it so the scale was similar in the mid-ranges where most noteworthy earthquakes occur. I think essentially all earthquake information is given in Moment these days, but since the numbers stayed similar, some members of the media perhaps haven't picked up on this.

Fill sandy soil does has not packed efficiently when deposited unlike that which has been laid down over geologic time and via transport by water so the vibrations of the earth movement cause it to move and flow like liquid. You can see a similar effect when playing with cornstarch and water slurry. Left to sit you can push down hard and it will support your hand, shake it and it will move and pour like a liquid.

A similar effect is what happens to the flowing soil/sand/rock debris in a lahar where the material acts like a viscous liquid in movement and then turns to a solid when the flowing motion stops.

Not too personal at all! The Wasatch front is a real seismic hazard but it differs significantly from Seattle's. In Utah the predominant seismic hazard is from the range-bounding "normal" fault that runs all along the front and right through Salt Lake City. ("normal" here being geological jargon denoting a fault that is a dipping plane, with the block on top slipping down relative to the block on the bottom--like gravity was driving it.) Big normal faults create the beautiful mountains and valleys all across the Basin and Range, with the Sierra Nevada on the west and the Wasatch on the east moving ever so slowly apart.

The Wasatch fault breaks in chunks that give rise to earthquakes in the M7+ range. Here's an image I stole from the USGS, showing the most recent breaks along the front according to geologists.

The overall level of hazard is a bit less than that of Seattle. The USGS National Seismic Hazard Maps provide gobs of detail. Here's a quick overview in which reds are bad and greens good (as usual!) that gives you an intuitive feel for the distribution of hazard in the western US.

Now this specific map represents a level of a specific frequency of ground shaking that can be expected with a probability of 2% in 50 years. This convoluted way of looking at things ends up being useful for planners, although it seems confusing to us mortals.  But think of it like a weather map showing the likelihood of strong rain, for example. You're more likely to get shook in Seattle over any 50 year period, then you are in Salt Lake. But both are pretty high.

The difference in Seattle is diversity [Gee, who would have thought Seattle to be more diverse than Salt Lake City?]. The potential earthquake sources that contribute to Seattle's high hazard level include M9 megaquakes on the subduction interface out to the west of the city, deep earthquakes (like the 2001 Nisqually earthquake ) in the downgoing sea-floor slab, and crustal faults (like the Seattle Fault that runs right through the city). While the chance of an earthquake from any of the three sources is fairly low (Well, the Nisqually-type source seems to have a rather high recurrence rate, given very similar events in 1949 and 1965 ), they all conspire to form a fairly hefty hazard here.

l'm having a discussion elsewhere about moral imperative and civil duty. l think it applies to this conversation.

You're right that some people are waaayyy too neurotic about this; it's my opinion that if the thought of natural disasters truly affect one's quality of life, he should consider relocating somewhere that isn't prone to them.

However, that doesn't mean we shouldn't take the necessary structural precautions and emergency contingency plans that will protect our numbers. Shit, were those in better place elsewhere, the aftermath of Katrina might have been far less horrifying.

l take some issue with a 'there will always be casualties' argument. Casualties are a fact in the face of natural disaster, but as Emily Steed pointed out in my 'fire' thread, that doesn't mean that packing up a few necessities/valuables in case of emergency is overthinking it. l don't think that's what you're saying (at least, l hope not), l'm just addressing that point in case it is. At any rate, "a few are going to die anyway" isn't a solid argument; it both diminishes the value of protecting as many as possible, and implies that there's no point in doing anything when both death and survival are simply just inevitable. lf your apartment collapses, you may die, but if you don't, that whistle or little foghorn that you grabbed when the earth started shaking will probably save your life. You might be alive solely because of the emergency drills you practiced. ls preserving that worth the preparation? Hell, yes.

This isn't Chicken Little, a completely irrational fear that the sky will fall. Geologically and statistically speaking, we'll have earthquakes whether we like it or not, and have little ones every day throughout Washington. lt's common sense to be ready, and the percentage of people who run around hollering about the sky falling is much smaller than those who make sensible preparations, and then do their best to survive when the big one hits.

That said, the viaduct and certain other structures in Seattle are things that we can control in terms of keeping casualties to a minimum, and they need to addressed. This is not a case in which procrastination should be overlooked.

OK, you're asking a seismologist about a volcano and if any of my vulcanologist buddies read this I'll never hear the end of it...

Let's clarify some obscure but important points. There are different kinds of volcanic eruptions, even at an individual volcanic center. At Yellowstone the most common kind of eruption is hydrothermal --superheated steam or water blasts out craters as large as half a mile across! But that isn't going to strongly affect the US. Magmatic (i.e. lava--molten rock -- the real stuff!) eruptions vary in the chemistry and physical properties of the magma they emit from soupy, runny, basalt like a Hawaiian volcano (picture lava flows running along the ground) to sticky chunky dry goobery gunk called rhyolite that can be as explosive as all get out. The commonest (i.e. most likely) eruptions are smaller ones, and caldera-forming super volcano explosions being the rarest. In fact. at Yellowstone the real bad boy explosions that frame the main point of your question occurred 2.1 million years ago and 1.3 million years ago and 0.64 million years ago. Based on average recurrence of these events, we are deep into a cycle and may only have to wait another 90,000 years for another. [I'm no statistician, but in order to actually answer your last question I just calculated a rough back-of-the envelope estimate of ~0.02% chance of a supervolcano eruption in 100 years, and I made some assuptions that make this rather a high-end estimate].

The most likely eruption, either hydrothermal or magmatic, would NOT be a super volcano, but a regular-sized family-friendly volcanic episode. It would be big news. It would close the Yellowstone National Park. It would likely put a thin layer of volcanic ash all over the northern tier of states. It would disrupt the heck out of air traffic. But it would not kill us all, or wipe out our civilization. (too bad, some might say!)

A supervolcano could be bad news, could disrupt agriculture downwind and could even affect global weather patterns (which actually could help forestall global warming?!). I still don't think it would come close to killing us all or wiping out the country.

Since there were no seismographs (and, even better, no seismologists!) around much more than a century ago, our evidence about how often Cascadia subduction zone earthquakes occur comes from what a lawyer might call "circumstantial evidence". Mostly, from tsunami deposits--characteristic sediments left behind when high tsunamis ran inland and left a layer of sand behind. Also from coastal tree stands in which the all the trees died at once, due to being submerged in saltwater as a result of deformation associated with a big event (and which we can date precisely using tree-rings).

Chris Goldfinger, at Oregon State has shown that Cascadia earthquakes also cause submarine "turbidity currents" that are essentially mudflows that cascade down offshore canyons, and that can be sampled using sea floor coring devices, and the events dated. The size, or magnitude, of these ancient events may be related to how widespread the shaking was (and thus how widespread their resulting turbidite deposits are found). He's established a chronology of Cascadia subduction events that seems to indicate that the subduction zone is "segmented". He interprets the data as evidence that the southern portion tends to go off in relatively smaller earthquakes (M8-M8.5?) relatively frequently. But about half as often the entire margin breaks (like it did 310 years ago), from Cape Mendocino to Vancouver Island, in a walloping M9 earthquake. From a seismologist's perspective, I think these findings are all logical and make a sensible story. But since I'm not a geologist I retain a skeptical attitude about just how well one can identify the turbidites arising from individual earthquakes in different submarine channels.

Ok, now for the probabilities. Yes the accepted 50-year probability of occurrence for a Cascadia Megaquake (sounds like something Hollywood would invent, no?) is generally regarded as 10%-15%. You could do worse than saying that if in any 500 year period I'm likely to have one M9 earthquake, then in 10% of that time interval (i.e. 50 years) I've got 10% chance of an M9. I know I know you think that a 50 year period starting at 450 years after the last earthquake will have a higher chance than one starting 100 years afterward. We call that "time dependent" probability, and it sounds grand. The problem is that you need to know a LOT about the variability of your "500 year events", or time-dependent probabilites don't do any better at forecasting likelihoods of earthquakes then the simple calculation we just did.

Goldfinger's results indeed suggest that the likelihood of a strong southern Cascadia Subduction Zone earthquake is something like twice as high as for the northern part of the zone, which only breaks in great M9 beasts.

Now for my answer to the triggering question: Not that I know of. While it is clear that stress changes and seismic waves from one earthquake can indeed cause other earthquakes to happen, simply not enough is currently known about how this works to enable us to guess how likely it is to happen with any particular earthquake. But my guess is that it is probably fairly rare since I'm not aware of any historical examples of subduction earthquakes being followed by a large crustal earthquake in the overriding plate (and I was looking for this after the 2004 Sumatra earthquake and last month's Chile earthquake).

First things first. Seattle need not worry about the San Andreas fault...it is way down in California and runs from Cape Mendocino south to near the Mexican border. Far away from us!

Now, closer to home. A number of active fault zones are known or suspected. There is a (rather crude, but reasonable) map at: http://www.pnsn.org/INFO_GENERAL/puget_faults.html and to see it you can click here .

Major actors include the Seattle Fault Zone that runs east-west just south of downtown, the Tacoma fault which runs through -- you guessed it, Iowa (no, just kidding--Tacoma), and the South Whidbey Island fault to the north of the Seattle Fault zone.

And of course, do not neglect the subduction fault that lies buried 40 miles or so beneath us--but which is only seismically active to the west. (There's a nice image of the subduction zone here ). Along this fault the sea floor on the Juan de Fuca plate offshore is being driven beneath North America. Stress that arises from that process (known as "subduction") ends up driving all the earthquakes we experience. To learn a bit more about what those earthquake sources are, you can read up on them at:

ht tp://www.pnsn.org/INFO_GENERAL/eqhazards.html

I'm glad you don't suffer from those dreams now. When I was a kid I dreamed of wolves attacking my house and ... well, I digress.

This is really a great question. And the proof is that some scientists say earthquakes can affect volcanic eruptions and some say no way . If we can't agree, then I guess I really have no right to give you a "yes" or "no" answer. Ok, enough of a disclaimer; now I can tell you what I think...

There is some statistical evidence that there were more eruptions after large Chilean earthquakes in 1906 and 1960. But the mechanism by which this "triggering" might happen isn't clear. There's also lots of anecdotal evidence of particular eruptions following certain earthquakes. But such stories suggesting correlation are not entirely convincing, nor do they demand causality . However,  it sure seems plausible that shaking from seismic waves can jostles magma and make it move around--and rise toward the surface if it is so inclined. But it takes magma time to work it's way to the surface. So the difficulty in observing earthquake-triggered eruptions, then (according to me) is that there are likely to be variable delays between the triggering earthquake and the ensuing eruption. Drawing the connection between any given earthquake and some ensuing eruption is uncertain.

I also think that as our capabilities to monitor both ground motion from earthquakes and the deformational processes that precede eruptions, we will be able to x-ray this whole process and answer this question concretely.

Good question! I have to admit I'm not an insurance expert. I also have to admit that I don't carry earthquake insurance. For most of us who live in small wood-frame houses, earthquakes will generally not collapse or structurally compromise our homes. Usual damage will be cracked plaster and/or brick facing, and breakage of contents (your china collection may be decimated, and your liquor cabinet a crying shame...). Most insurance riders, as I understand it, have really high deductible amounts, so you don't see much benefit (if any) after a moderate shaking...which is the most likely.
Serious problems, however, happen when structures are not properly tied to the foundation and the entire structure slips off. Or possibly when chimneys collapse. Or when a gas appliance (water heater, generally) tips over and an open flame catches the structure on fire. I think you are better off dealing with these problems directly, both financially and in peace of mind, rather than relying on insurance.
Similarly, your home's contents can be protected by taking some simple precautions.
Learn more about all of these issues at the website for CREW (the Cascadia Region Earthquake Workgroup:
http://www.crew.org/home/homeowners.html