Earthquake off Northern California

merger writes "A 7.0 earthquake (7.4 according to NOAA) occured off of the northern California coast occured at 7:50 p.m. PST triggering a tsunami warning (which was then downgraded to a tsunami bulletin). While searching Google News for information I learned about an earthquake preparedness study for the area which was just published today."

Re:Anyone know how many hurt?

[krautcanman]

None. The earthquake was approx 80 miles offshore from Crescent City, about 300 miles NW of San Francisco. The Tsunami warning was retracted within an hour of the quake.

Japan

[JanneM]

Here in Japan they have the very sensible system of reporting not only (and not even mostly) the energy released at the epicenter, but most prominently the expected effects at any area affected by the earthquake.

They have a seven-point scale, with 1 being that you only just feel the quake if you are lying down or otherwise sensitive; to 7 being that nonhardened buildings collapse, and many expected injuries and deaths. Quake reports are usually in the form of maps with this info overlayed.

For most of the public, that is the kind of info you want when an earthquake has occurred, rather than the intensity at the origin. It tells you much clearer if it's time to worry about friends and relatives or not.

LIGO noticed it

[Anonymous Coward]

Although it wasn't nearly large enough to cause any damage, the shaking was signifigant enough to disturb the Hanford LIGO site. Took about 3-4 hours for ground motion to calm down enough that the mirrors could be used again. Most of the people working on the Interferometers decided it was a good time to head out and grab dinner.

And for those that don't know what LIGO is, look at http://www.ligo-wa.caltech.edu/ [caltech.edu] And check out the Einstein@home project while you're there.

earthquake/tsunami insurance?

[JimBobJoe]

I used to joke that insurance companies didn't care about the very imminent geological dangers that face California, because, they reckon, once the big one hits, there won't be anyone left in California to make any claims.

On the other hand, it's been pointed out to me, semi-recently, that most Californians do not have earthquake insurance.

I dunno about you, but that, with the combination of homes which average $509k, is a source of worry for me. Any Californians able to comment on earthquake/tsunami insurance?

IANA Geologist, But....

[ChipMonk]

Something I noticed after the 5.2 quake in southern California, is that there was a tremendous number of temblors immediately following, but they were all focused around the site of the original quake. I had to wonder how much stress was building up along the fault line, to the north and south.

As I type this, I see >800 quakes on the California/Nevada quake map [usgs.gov], and I wonder how much more stress is building up around Silicon Valley. (Yes, I live and work in the Valley.)

I suspect that big slips north and south increase the odds of a slip in between. Are there any geologists out there who can verify this?

Re:earthquake/tsunami insurance?

[Council]

http://en.wikipedia.org/wiki/Earthquake_insurance [wikipedia.org]

Earthquake insurance in California is very expensive and hard to get. For some reason, insurers don't like the thought of a million people suddenly needing to replace the main joists* in their houses. And so they set the premiums extremely high or refuse to offer coverage altogether.

* I have no idea what a "joist" is.

Backup links ...

[Savage-Rabbit]

No, the amusement is in realizing that if the earthquake caused a break underwater, that it's not going to be fixed in ~2 hrs, thus indicating the cluelessness of the question pondered.

Why? That underwater link that guy mentioned might still be broken, if was indeed broken they probably activated an auxiliary/backup link to route their traffic through and are still working on the severed cable. I rely on a connection via a series of undersea links that have been severed a few times over the last few years by anything from fishermen to mechanical diggers and underwater sand-mining operations. Over here it rarely takes the local telecom more than half an hour to start routing traffic through backup connections but then of course we don't get as quite as many earthquakes here as they do in California

You are sooo wrong!

[Anonymous Coward]

I call bullshit on your statement that "most of Santa Cruz was destroyed in the loma prieta 15 years ago".

I lived there, and I have plenty of photos and video that show that damange, but in NO WAY was most of the town destroyed.

Fuckin wanker!

Re:earthquake/tsunami insurance?

[Bootard]

The best part of it is that the Hayward fault that runs under UC Berkeley is the most likely fault to be the source of the next major quake in N.Cal. While I was there(class of '03), seismologists estimated that there was a 30% chance the next big one in N.Cal would come from that fault, although I think that percentange may have been downgraded since. That fault runs right through the middle of the football stadium, so when they built it, they had to put in expansion joints in the stadium so that the stadium would be ok(the west side is moving north and the east side is moving south). If you go to the stadium and check it out, you'll see that the fault has caused the 2 halves of the stadium to shift probably 24 inches from each other. They also have to flatten out the turf every so often, because the fault causes the field to lose its flatness. If you go to the stadium towards the end of the season, you can usually see where the fault runs on the field. It's well worth checking out one day. Go Bears!

Earthquakes can't be usefully predicted

[jesterzog]

one happens every 200 or so years on average. The last one happened around 1700, so another one is fairly likely in the near future.

This is just a small nit-pick with this assertion. Sorry for dragging it out as I have.

I don't know where you're getting your information from, but I also have a good friend who's a geophysicist, and I know a lot of others in the Earth Sciences department next door to my own. (We have a lot of major earthquake-causing fault lines in New Zealand, and it's a popular place for geophysicists from around the world to hang out.) If someone knows more then I'd welcome a correction, but my understanding is that earthquakes are still almost entirely unpredictible with today's knowledge.

We can look at the history of any site and calculate an average earthquake frequency, just as your site averages every 200 years. If you look a short time into the future, it'll probably remain an average of about 200 years.

But in Earth science terms, a "short" time is millions of years. When the frame of reference is so large, attempting to predict events accurately to hundreds of years is hopeless. An historical average of a big quake every 200 years really doesn't tell us anything useful about the immediate future of a site in terms comparable with a human lifetime.

I've heard people argue about how the stress is released after an earthquake and there's a relation. I think this is a very common misconception that seems intuitive, but doesn't really match the facts as we know. All the geophysicists I've spoken to have claimed that this is mostly fiction, though.

The biggest problem with this approach is that there's no clear and accurate way to even estimate, let alone measure, how much stress there was in the first place. Most of what we can guess simply comes from analysing historical records, and accurate records often don't even exist beyond the past few hundred years, if even that. You might have thought that 7th magnitude quake was big and released a lot of stress, until an 8th magnitude quake suddenly releases ten times as much energy [wikipedia.org], with the earlier quake having made a negligible dent in its force.

If you look historically at the quakes in your area, you'll probably see that they're not set at all evenly. Even if you've gone for 300 years without an earthquake, chances are it's about as likely that you'll get a big one tommorrow as it is that you'll get a big one 1000 years from now. Perhaps you'll get 3 or 4 big ones in the next 3 or 4 decades.

This isn't to say that it's not worth preparing for, though. If you live on a fault, chances are that you'll at least get moderate earthquakes, and over a wide enough population, it's quite likely that some part of it will be hit every so often. (The media doesn't normally report about all of the places that didn't have earthquakes.) Good building standards and response strategies, for instance, are the reason that there may only be a few tens or hundreds of casualties in a well-off country, whereas it might be hundreds of thousands or millions of casualties for an equivalent quake in a third world country.

Re:Earthquake? Bah....

[Hatta]

Oh come off it. Humor is a healthy way of dealing with tragedy. If you get offended that's your choice. Moping about isn't going to bring anyone back, and I prefer to smile.

Not so long ago I lost my dad to heart disease, a perpetual natural disaster that kills more people than 10 WTC attacks every month. And you know what, I still laugh when Homer has a heart attack. If I were to die a horrible horrible death, I'd at least hope someone could get a giggle out of it.