The USGS listing of quakes -- foreshock, main shock, aftershocks -- is astonishing. I'm at a loss for a sufficient superlative.

7.2 foreshock on Wednesday, followed by three 6.0 + quakes and dozens of 4+ and 5+ on during Wednesday-Thursday.

Friday's 8.9 main shock, a subsequent 7.1 and (so far) twenty-five over 6.0


http://earthquake.usgs.gov/earthquakes/recenteqsww/Maps/10/140_40_eqs.php


Every one of these 6+ quakes must be taking a toll on surviving infrastructure.

"Oregon and Washington coasts will have only 30 minutes or so before a tsunami hits, when the subduction zone quake scenario in that region plays out as anticipated someday."

I was reading an estimation that, depending on placement, depth and probably other conditions, it could be 10 minutes or less before a tsunami hit the OR/WA coast after a quake.

Having spent many hours on Oregon beaches myself, I wonder if a person would actually feel a quake in the sand? I have warned my sister (new to the PNW) that if she did feel a quake, or saw a coastal draw-down, not to wait for anything, just to RUN. That's not the time to collect your belongings!

Sue

As a rule of thumb, only very strong earthquakes (like 8.0+) can produce these very large, destructive tsunamis, and an 8.0+ quake lasts a long time, so I highly doubt that you could ever miss feeling the Cascadia subduction zone letting loose in a big way.

On one of these video clips, they were interviewing someone from the Australian tsunami warning agency. He broke down the various things that need to happen between the time of a quake and when Joe Average on the ground actually receives a warning to evacuate and he says it's very difficult to do so under 30 minutes.

Although there can be automatic algorithms hooked up to sensors that will send out a warning, it does take a human time to analyze the specifics of a quake, it's location, intensity, depth, the ocean topography, whether there was ocean floor displacement, etc. to make a more definitive prediction. Which is not a good thing for the PNW. But yeah, any time you feel a really strong earthquake in the PNW--the kind where you're muttering, "Holy ****...holy ****..." and everything is getting knocked down, head to higher ground as soon as it's safe if you're near the coast and near sea level. In the Sendai quake, the tsunami pushed 6 miles inland!

However, the other possibility is that the quake happens far enough away that the intensity is a lot lower. I think that a major quake in the Aleutians, near Alaska, could also generate a large tsunami that sweeps down to the PNW without major shaking being felt in the lower 48 and get there pretty quickly.

Ten minutes = toast

For most peops, if caught on a beach with a Japan-scale tsunami surge in route.

Next time at Cannon Beach I should clock how long it would take to run from the water-line to the road. There's usually considerable sand in between. And that wouldn't be high enough for comfort. Doubtful I'd get high enough on land on foot in 10 minutes to survive what hit Japan.

Next time I visit a west coast beach I'll be carrying a rucksack everywhere and with a new mindset.

I wonder what it would cost to build in the northwest the same earthquake early warning system that Japan has.

In my neighborhood we are lucky that there are some good hills right beside some of the beaches. If you feel a strong earthquake and you get moving straight away - you should make higher ground in time. But this is by no means true for all the beaches in So. California.

In addition to the tsunami problem, there is also a "big wave" problem for some beaches. Some of our Californua coastline has deep submarine canyons that come very close to the shore. The bottoms of those canyons are covered in deep mud. That mud can cascade downwards into the canyon during a quake - triggering a strong water response at the surface. That could generate some very big local waves - enough to swamp the beach. Those waves could arrive almost immediately after the quake. But this problem only occurs at selected beaches ... it's not a general situation.

Chernobyl: Your objections above are right. i was wrong to use that analogy. Chernobyl had a different kind of reactor. A Russian physicist pointed that out on TV today. Still - I am concerned by the latest photo's from the Japanese power plant. Take a look at the photo shown on the other thread talking about this subject. There's a pretty big fire burning there - it seems to be too big to match the explanation given by the Government.

Arney: Unfortunately, our worst fears are confirmed. I saw an eye witness report from Sendai this morning, from a Japanese guy who drives a big rig. His truck was washed over by the tidal wave, but the rig was heavy and it didn't get dislodged. He said that other families driving in cars on the same road were washed away by the big wave. Very sad.

other Pete

Dagny, it sounds like that would make you smarter, i mean, more prepared, than some of the locals.

earthquake, tsunami, aftershocks, nuclear meltdowns, and now this...

http://mobile.thestar.com/mobile/NEWS/article/953212

Japan’s weather agency says a volcano in southern Japan has resumed eruptions of ash and rocks as the country struggles with the aftermath of a catastrophic earthquake and tsunami in the north.

Just seen this on msnbc.com....the pic speaks for itself.

In Portland, there are more fault lines running through the hills. Dangit!

Edit: I just moved this from the nuke thread.

Statistically, there should be more aftershocks that are very strong. Normally, they would be considered major earthquakes in themselves, but they would be somewhat pale in comparison to the original quake. One expert on TV was saying that extrapolating from the averages, you could expect one magnitude 8 and ten 7's in the coming weeks. WHAT??? I really hope the averages don't apply in this case.

I wonder how much infrastructure has been weakened by the original quake and is now more vulnerable to these major aftershocks? It's possible that a major aftershock or two could cause more damage to Tokyo than the original quake. I shudder to think what it would do to the nuke plants that are already struggling due to damage.

It also means that people who thought they dodged the bullet with the 8.9 and weren't prepared, should really make preps right now. I'm telling the people I know in Tokyo to be prepared for more, just in case.