If you don't buy earthquake insurance, can you count on state or federal disaster relief programs to pay for reconstruction?
[Edit] Or to rephrase the question, do disaster relief programs create a moral hazard that should be countered by making earthquake insurance in high-risk areas mandatory (with possible subsidies by the state)?
The wikipedia page of the 1906 earthquake[1] is quite instructive:
> Capt. Leonard D. Wildman of the U.S. Army Signal Corps reported that he "was stopped by a fireman who told me that people in that neighborhood were firing their houses…they were told that they would not get their insurance on buildings damaged by the earthquake unless they were damaged by fire".
The issue wasn't that simple. The Army marched in and pretty much went rogue -- they came in and started blowing up buildings to create firebreaks and caused more fires in the process.
The city was also particularly vulnerable to destruction from fire. Lots of unstable landfill, the water used for fire fighting was in underground cisterns that were damaged, and key firefighting personnel were killed.
There's a recent book "San Francisco is Burning" that is a really good account.
It's hard to imagine private insurance companies being able to actually pay out their obligations in the event of a massive earthquake in any metropolitan American city. Federal (and to a smaller degree, state) governments will almost certainly put up most of the money for recovery and rebuilding.
I wonder how much damage it would take to bankrupt even the reinsurers. Would a hurricane Katrina sized disaster hitting every city from SF to Vancouver do it?
The human response to disaster planning is offloaded to a committee who's responsible for disaster mitigation.
Call it a government.
Residents living on the banks of that large river in North Africa built a fucking awesome risk mitigation strategy for said government. Eternal life under a stacked pyramid of stones.
What is required to make a building survive a big quake has been known for some time - the real question is has it been done on the building you are in when the next big quake hits.
A friend who lives in Tokyo relatively frequently experiences fairly large quakes - everything shakes, the buildings wobble, you pick the stuff up off the floor and get on with what you were doing.
Sure for a really big quake it would be more significant but the engineering there is really impressive.
And more specifically (concerning regional resilience): how much of the existing housing stock is built to standards which will survive a likely quake?
San Francisco's last slate-cleaning came in 1906, though parts of the city were constructed far more recently. The 1989 earthquake (nearly 100 km distant and comparatively mild (6.9, as opposed to an 8 or 9 mag such as the 1906 quake) still caused significant structural damage throughout San Francisco, though major damage was limited to a few neighborhoods and specific buildings -- more major damage was concentrated largely to the south, closer to the epicenter.
Most of Tokyo was destroyed during WWII, and has been rebuilt since. Japan also experiences frequent powerful earthquakes (several M8+ quakes are noted by the USGS: http://earthquake.usgs.gov/earthquakes/world/historical_coun...), effectively requiring more robust building standards. Though my understanding is that there's a great deal of collaboration between Japanese and Californian engineers on this work.
Right. Loma Prieta was pretty serious, particularly closer to the epicenter (and as I recall, damage sort of hopped and skipped among geologically unstable landforms for quite some distance). But it was less than 1/10th as powerful as the 1906 quake.
And yes, M9s are monsters -- the Boxing Day and March 11 earthquakes in Indonesia and Japan were both M9s, I believe there was one in Chile ... ok, that was 1960 -- the 1964 Prince William Sound, Alaska, quake was also 9+. Listing at Wikipedia: https://en.wikipedia.org/wiki/List_of_earthquakes
On the US West Coast, it's the Oregon / Washington coast which would be most likely to see a quake of that magnitude, along the Cascadia fault, a megathrust fault which could produce similarly large tsunamis as well as massive shaking. For most of California, not so much.
"Whistling past the graveyard". There's good stuff in John McPhee's Assembling California [1] about the '89 Loma Prieta earthquake, and about earthquakes in general.
6-7 is not THAT bad. Most modern buildings should be able to handle this relatively fine. In Japan usually nothing recent falls apart until after 7. Anyway, in terms of casualties, it all depends where the epicenter exactly is, and at what time of the day or night the earthquake strikes.
This has some truth but not the whole picture. I recently listened to a fascinating Podcast from Freakenomics Radio called, "Are Japanese homes disposable?" where they discussed a huge cultural difference regarding how the Japanese view their homes. When they purchase a home, they usually tear it down and build a new one from scratch. Once a home is built, the Japanese invest almost zero money/effort into maintenance. The average half-life of a home there is 38 years compared to over 100 in the US (not just SF). Growth in their construction industry is rapid despite almost stagnant economic growth. Anyway, it was just super interesting and definitely worth a listen to, especially because "earthquake fear" is an overstated factor in their housing production.
> Once a home is built, the Japanese invest almost zero money/effort into maintenance.
Not really true. There are hundreds of companies in every city specializing in what Japanese call "Reform", which means making older houses/building more modern (either through maintenance, renovation, replacement of installations and so on).
Maybe. I'm know very little about Japanese culture but based on what I heard recently from that podcast, the statics they mentioned regarding home maintenance contradict your statement. Or maybe there are hundreds of companies but the reforms only touch a small fraction of total structures and those structures are non-residential...
2 summers ago there were a couple of great shows at some Tokyo Museums about Tokyo's Urban Metabolism[0]. Not only are homes quickly replaced as you have stated, but the neighborhood structure, created by the commercial buildings on the main roadways and the small homes on the interior, forms a firebreak.
With earthquakes, fire is the greatest threat after the shaking stops.
I actually believe the construction in Japan are much more reliable than construction in San Francisco.
The earthquake risk is everywhere in Japan, so that's a major point that all construction rules take into account. Those rules are revised regularly, getting stricter as technology permits it. A good chunk of the property owners fees go into renovation to make the building earthquake-safe, and an building decreases in value as it gets older because people know it won't be as strong in case of an earthquake.
On the other hand earthquake is not a problem in most places in US, even California doesn't compare to Japan in terms of earthquake risks - outside the Bay Area. So the whole country isn't thinking in terms of earthquake protection, and that makes a difference.
So San Francisco will certainly do much better than Turkey or Haiti, but I don't think it will resist as well as Tokyo.
Not completely true. There's a risk map established by the government in Japan and several areas are considered "safe". For example, Kyoto has not had major earthquakes for centuries.
> A good chunk of the property owners fees go into renovation to make the building earthquake-safe
That's not true either. Usually buildings have a "shelf life" in Japan and whenever they reach the end they end up being destroyed and replaced by newer ones (built with the latest standards). Besides, older constructions can be actually pretty solid, it's rather all the newer stuff with large window panes and less walls that tend to be more fragile.
Kobe is right next to Kyoto and recently had a major earthquake (1995?).
A lot of the older Japanese construction, especially out of Tokyo, is poorly insulated and kind of flimsy. I was very surprised since I always thought of Japan as being rich. I'm sure the wood would do well in the earthquake, but that's the other problem: wood eventually rots and needs to be replaced (those Shinto temples are rebuilt every 30 or 40 years I think).
> Kobe is right next to Kyoto and recently had a major earthquake (1995?).
Hey man, I live in Kobe :) Kyoto was left largely intact after the earthquake in 1995. Of course they felt it, but nothing was devastated there. Kyoto is further up in the middle of the land, further from the seismic rifts, and relatively safe in terms of location.
> (those Shinto temples are rebuilt every 30 or 40 years I think
I think you are refering to Ise Jingu which is destroyed and entirely rebuilt every 20 years. But that's a very different thing. Most large temples no not get rebuilt very often, and their trunks can last centuries.
I think you are referring maps of the risks related to an earthquake (ex: tsunamis, landslides, rivers overflowing, wide range fires) and not the risk of getting an earthquake.
In Tokyo, the area of Odaiba would be a super high risk area due to the artificial soil and the proximity to the ocean for instance.
> So San Francisco will certainly do much better than Turkey or Haiti, but I don't think it will resist as well as Tokyo.
I've lived in both SF and Tokyo, and agree with this statement. Put simply, seismic danger is a Much Bigger Deal(tm) in the latter. It's on everyone's mind, and it's reflected in just about any and every building you enter.
I don't have hard data to support my case, but at least in terms of noticeable seismic activity there really is no comparison. I probably experienced more tremors during any given month in Tokyo than I did during a full year in SF.
19 January 2038 is the world's end date according to the Unix demigods prophecies, so it doesn't make much sense to predict what's going to happen afterwards anyway.
One of the biggest reasons I have avoided moving to SF is because of earthquake liquefaction dangers. I however just recently moved out to Provo Utah from LA temporarily - I didn't know this was a hotbed as well. How would you compare the threat levels here to SF? Comparable? Or severely less than SF?
The risk is lower, but still high. The last estimate was a 16.5% chance of a magnitude 7.0 earthquake in 100 years[1]. I expect the probability will be revised to be higher in the seismic hazard assessments due to be released this year.
7.0 doesn't sound big, but keep in mind, the epicenter would be quite close to the surface and likely to be right in the middle of a highly populated area on the Wasatch Front (Salt Lake City, Cottonwood Heights, etc). Also, many buildings in the vulnerable areas pre-date construction codes that take seismic risk into account. For example, it wasn't until the late 70's that they started reinforcing masonry construction.
The Wasatch fault zone does pose a significant seismic hazard but earthquakes on the WFZ are not nearly as regular as on the San Andreas. On this page [1] (second picture, left side) is a figure showing the instances of known earthquakes along the fault through time; you can see that they're quite irregular, both in space and time. An updated compilation of this data [2, gated] has better accounting of the uncertainties and a fuller record, especially on the older end. In any case, it's clear that some of the fault zone seems to be 'overdue' but other segments, including the Weber and Provo segments, have had moderate earthquakes within the past ~500 years, which is a bit shorter than the median recurrence interval. The SLC segment on the other hand may have enough accumulated stress to cause a pretty significant earthquake.
Note that it's really not clear to what extent faults rupture periodically; there are researchers who argue that the likelihood of an event is basically independent of the time since the last event (basically a Poisson distribution), those who argue for fairly regular events, and everything in between. It probably varies a lot from fault to fault and is more regular on big plate boundary faults like the San Andreas than on smaller (or slower-moving) intraplate faults like the Wasatch Fault.
The real danger, both here and for the San Andreas system, is that an earthquake will break through the segment boundaries and cause a much, much larger earthquake. It's not been demonstrated that this is has happened on the Wasatch fault (there is one instance about 6000 years ago where this is possible within the data uncertainty) but this has happened in California in the 1906 S.F. and 1857 Fort Tejon earthquakes. Although this might not cause more displacement of the fault in any one location, it creates such a bigger swath of destruction that there are more opportunities for associated disasters (fires, floods from dams breaking, etc.) and make response much more difficult. It's also a bit outside my expertise but I think that for a long rupture, there is enough constructive interference of surface waves from the earthquake that ground shaking is much greater than is predicted from displacement at any point on the fault.
What's interesting is that everyone's very aware of the seismic hazard along the San Andreas, but many people aren't aware of the much larger (but much less frequent) hazard in the Seattle/Portland area.
The San Andreas is a strike-slip system. It's not capable of generating very large (magnitude 8 or greater) earthquakes.
The Cascadia subduction zone has had magnitude 9 earthquakes in the past. The last one was on Jan. 26th, 1700. (Thank Japan for having excellent historical records of earthquakes and tsunamis. We know a large earthquake occurred around 300 years ago in the area, and thanks to Japan's record of the tsunami it caused, we can make a solid link to the exact date.)
We don't know the statistical hazard as well due to the small sample size, but when the next large Cascadia earthquake occurs the damage will be absolutely catastrophic.
It's not just the direct earthquake damage, but also the tsunami hazard. You need vertical offset to cause a tsunami. A strike-slip system like the San Andreas is very unlikely to cause a tsunami. The permanent offset is dominantly horizontal, so the only way to generate a tsunami is through secondary effects such as landslides. (Also, most of the length of the San Andreas is onshore.)
Subduction zones are thrust systems. One plate moves up, and the other moves down. Earthquakes there are likely to produce permanent vertical deformation at the surface.
Furthermore, certain types of subduction zones are more prone to generating large tsunamis. A deep earthquake is unlikely to cause much deformation at the seafloor, and therefore doesn't generate as large of a tsunami. However, the shallower the rupture penetrates, the larger the deformation at the seafloor is, and therefore the larger the tsunami is. Certain types of subduction zones are more prone to having large earthquakes that rupture all the way up to the seafloor. (The amount of sediment on top of the incoming oceanic plate is thought to play a large role in this, among other things. The recent Tonankai earthquake in northern Japan turned a lot of what we thought we knew about this on its head, though.)
The Cascadia subduction zone is one of the end-member types that's likely to have both large earthquakes and large tsunamis. We know it has in the past, and it's likely to in the future. It's unusual in that most of the deformation along the fault occurs through periodic creep ("slow-slip events") that doesn't cause an earthquake. (Actually, as we're finding out, it's not that unusual around the world, but it was first observed and is best documented in Cascadia.) However, while this creep does relieve a significant portion of the accumulated elastic strain, it doesn't relieve all of it. The plate boundary fault is still accumulating elastic strain that will eventually be released in a large earthquake.
At any rate, just something to think about. The seismic hazard in the Bay Area can be reduced through proper engineering solutions. (Though SOMA is going to be in very rough shape for the reasons this article mentions. Lesson for next time: Don't bulldoze all the rubble into a pile and then build on top of it!)
For Cascadia, though, you can't engineer your way around a magnitude 9 earthquake and tsunami. You do the best you can, and try to avoid putting critical infrastructure near the coast.
Following the major landslide that just occurred up here, was poking around and came across this fascinating article on what is likely to happen to Seattle in a large earthquake.
Here's a video of an "underwater forest" discovered by some divers in Lake Washington, seemingly caused by a previous landslide: http://vimeo.com/35477614
Similar would happen if Ranier blows it's heavily glaciered top. People don't realize just how much Seattle is a death trap of earthquakes, volcanoes, and rain. Californians take note <s>.
I sometimes imagine Spokane being inundated with refugees from the Big One, whether earthquake or Rainier blowing (or both). I've got a couple of spare rooms ya'll can use for a while. What'll be really interesting will be when the refugees realize that a house that would cost them $1.5M in Seattle will run about $300K in Spokane with no quake/volcano risk and no shortage of Starbucks shops around.
The Portland Mercury (a free alt-weekly) published a cover on this last year, mostly about how ill-prepared the city is in general for earthquakes. Glad to see this sort of friendly-neighbor approach happening though, as it's going to be more effective right now than waiting for the politics to catch up, and oh so very Portland.
How much of a threat is it there? Portland's sounded like an attractive place to try to move to, having the best bicycle transport "infrastructure" in the country. Seems like the side-effects like mudslides are worse than the direct effect of the earthquakes themselves in that region.
I moved back from Japan just a few months before the 2011 disaster.
In Vancouver BC it's well known that "the big one" is coming at some point, and I recall many earthquake drills as a child and a class field trip to UBC's earthquake research centre.
Even though the fact of the potential for a high magnitude earthquake is well known absolutely no one (including myself) is prepared for it at all. I've certainly been meaning to fashion myself a "bug out bag" in case of a disaster but haven't gotten around to it...
Vancouver also has a liquefaction concern. The false creek flats area is filled in estuary/marsh and though it's largely industrial there are plans to move Emily Carr School of Art to that area. I live pretty close to it so I have no idea how affected I am. Even worse is the entire nearby suburb of Richmond (pop 175k) is built on an island of silt in the Fraser River and is probably pretty much entirely a liquefaction zone.
I was aware of the earthquake danger, but the tsunami is news to me. Given that we are not directly on the ocean, I imagined that the significant buffer provided by the Puget sound would absorb the majority of a tsunami; is that not the case?
You're right, Seattle would be sheltered from the brunt of a tsunami caused by a subduction zone earthquake. (More so than I realized until I looked up the predicted inundation maps. I'd forgotten how large Puget Sound is!)
A large tsunami would be quite damaging lot of smaller coastal cities along the western coast, though. It's a major concern, at any rate.
Do you live in cascadia? Out of curiosity, what would be your advice in terms of personal preparation for a potential high-magnitude earthquake (assuming that my goal is simply for me and my wife to survive)?
The buildings in Seattle are also not prepared for a quake of the magnitude expected to hit it soon. California building codes are much stricter.
Downtown Seattle is also built on a mudflat that caused countless problems in early Seattle history. Areas built on mudflats will be hit especially hard in an earthquake.
Personal anecdote: I grew up in Seattle, and I was terrified of earthquakes for my whole childhood. Every time my apartment building would sway at night it would jolt me out of my sleep in a cold sweat. I did a few semesters at a design school on the waterfront that was built on top of a landfill which is predicted to liquify during a large earthquake and swallow the first 1-2 floors of the structures there. One day, while walking to class, I stopped to talk to a construction crew fixing cracks in the viaduct and they told me the entire waterfront sinks approximately 1 inch every year and requires constant repair to the infrastructure there. I've since moved to the atlantic coast and plan to avoid the pacific rim for the rest of my life. :)
The problem is that earthquake insurance is so expensive and so high-deductible that a risk analysis only concludes it's worth getting if you live in an especially risky neighborhood, or have an especially at-risk house.
So only the riskiest buildings get it.
So the average customer of the insurer skews ever closer towards the extremely at-risk end of the spectrum.
So the insurance companies have to raise the rates and deductibles.
And then you go back to step one, and the vicious cycle gets even more extreme.
> So the average customer of the insurer skews ever closer towards the extremely at-risk end of the spectrum.
> So the insurance companies have to raise the rates and deductibles.
This chain of "logic" only makes any sense if you assume that the insurance companies have to offer all their customers the same rates and deductibles. If the building owners can figure out that they're facing an elevated risk, why can't the insurance companies?
That doesn't address anything I said. My parent comment already presupposed that they're able to change their rates. Are they really required to insure anyone who wants it, all on exactly the same terms? If so, maybe the problem isn't that earthquake insurance is just a natural death spiral?
Actual former SF resident here. I'll tell you exactly why I would live in SF, it's because it's one of the most beautiful cities in the world, and I also choose not to live my life in fear.
Yes, there's a threat of earthquakes. Yes, I'm sure there is going to be an earthquake at some point, possibly even large. I experienced a tiny earthquake in SF a few years ago and it scared the shit out of me, because my entire apartment was shaking.
But there are threats everywhere. Would I buy a house (if I can afford one, that is) in a liquefaction area? No. But there are plenty of areas of SF that don't have imminent liquefaction risk. And the chance of actually dying is quite low. There are plenty of things to worry about, but earthquake would be on the bottom quartile for me. And compared to the benefits of living in SF, it isn't even a big concern.
Californians especially are woefully unprepared for disaster. I started a local company (http://expresssurvival.com) selling survival kits and emergency gear to try to help the community get prepared and realize the importance of having those supplies when that next earthquake hits.
Most of us understand that its not a matter of if, but when we will need those emergency supplies, but as someone pointed out earlier, we are "whistling past the graveyard."
"On the anniversary of the 1906 San Francisco Earthquake, Mayor Ed Lee signed into law the Mandatory Soft Story Retrofit Ordinance. This legislation requires the evaluation and retrofit for “multi-unit soft-story buildings,” defined as: Wood-frame structures, containing five or more residential units, having two or more stories over a "soft" or "weak" story, and permitted for construction prior to January 1, 1978."
I can't believe only 10% of SF homeowners have earthquake insurance.
Unfortunately, I'm sure there will be a taxpayer funded bailout of all these people once their homes are damaged/destroyed in the next big one. So, why bother?
So lets disrupt a bit:
1. Identify companies with liquidity, significant exposure to earthquake damage (down to the liquification zone offices)
2. short their stock
3. Wait for the 99.7% chance of earthquake by 2038 (more math to follow)
4. profit!
Warren Buffet might be interested, since he's taken up betting against idiots. YC application, here I come!
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[ 4.5 ms ] story [ 77.2 ms ] thread[Edit] Or to rephrase the question, do disaster relief programs create a moral hazard that should be countered by making earthquake insurance in high-risk areas mandatory (with possible subsidies by the state)?
> Capt. Leonard D. Wildman of the U.S. Army Signal Corps reported that he "was stopped by a fireman who told me that people in that neighborhood were firing their houses…they were told that they would not get their insurance on buildings damaged by the earthquake unless they were damaged by fire".
[1] http://en.wikipedia.org/wiki/1906_San_Francisco_earthquake#S...
The city was also particularly vulnerable to destruction from fire. Lots of unstable landfill, the water used for fire fighting was in underground cisterns that were damaged, and key firefighting personnel were killed.
There's a recent book "San Francisco is Burning" that is a really good account.
Call it a government.
Residents living on the banks of that large river in North Africa built a fucking awesome risk mitigation strategy for said government. Eternal life under a stacked pyramid of stones.
Sure for a really big quake it would be more significant but the engineering there is really impressive.
He's lived there quite a while and has experienced several which have woken him up.
San Francisco's last slate-cleaning came in 1906, though parts of the city were constructed far more recently. The 1989 earthquake (nearly 100 km distant and comparatively mild (6.9, as opposed to an 8 or 9 mag such as the 1906 quake) still caused significant structural damage throughout San Francisco, though major damage was limited to a few neighborhoods and specific buildings -- more major damage was concentrated largely to the south, closer to the epicenter.
Most of Tokyo was destroyed during WWII, and has been rebuilt since. Japan also experiences frequent powerful earthquakes (several M8+ quakes are noted by the USGS: http://earthquake.usgs.gov/earthquakes/world/historical_coun...), effectively requiring more robust building standards. Though my understanding is that there's a great deal of collaboration between Japanese and Californian engineers on this work.
And yes, M9s are monsters -- the Boxing Day and March 11 earthquakes in Indonesia and Japan were both M9s, I believe there was one in Chile ... ok, that was 1960 -- the 1964 Prince William Sound, Alaska, quake was also 9+. Listing at Wikipedia: https://en.wikipedia.org/wiki/List_of_earthquakes
On the US West Coast, it's the Oregon / Washington coast which would be most likely to see a quake of that magnitude, along the Cascadia fault, a megathrust fault which could produce similarly large tsunamis as well as massive shaking. For most of California, not so much.
[1] http://www.nytimes.com/books/98/07/05/specials/mcphee-califo...
Not really true. There are hundreds of companies in every city specializing in what Japanese call "Reform", which means making older houses/building more modern (either through maintenance, renovation, replacement of installations and so on).
Is that more or less than one would expect for one of the wealthiest & most technologically sophisticated countries in the world?
With earthquakes, fire is the greatest threat after the shaking stops.
0: http://en.wikipedia.org/wiki/Metabolism_(architecture)
Actually, the low average age of houses in Japan is not at all due to the war (it's much smaller than 60 years), but due to cultural/economical issues: http://www.reddit.com/r/japan/comments/vv3bf/why_do_japanese...
The earthquake risk is everywhere in Japan, so that's a major point that all construction rules take into account. Those rules are revised regularly, getting stricter as technology permits it. A good chunk of the property owners fees go into renovation to make the building earthquake-safe, and an building decreases in value as it gets older because people know it won't be as strong in case of an earthquake.
On the other hand earthquake is not a problem in most places in US, even California doesn't compare to Japan in terms of earthquake risks - outside the Bay Area. So the whole country isn't thinking in terms of earthquake protection, and that makes a difference.
So San Francisco will certainly do much better than Turkey or Haiti, but I don't think it will resist as well as Tokyo.
Not completely true. There's a risk map established by the government in Japan and several areas are considered "safe". For example, Kyoto has not had major earthquakes for centuries.
> A good chunk of the property owners fees go into renovation to make the building earthquake-safe
That's not true either. Usually buildings have a "shelf life" in Japan and whenever they reach the end they end up being destroyed and replaced by newer ones (built with the latest standards). Besides, older constructions can be actually pretty solid, it's rather all the newer stuff with large window panes and less walls that tend to be more fragile.
A lot of the older Japanese construction, especially out of Tokyo, is poorly insulated and kind of flimsy. I was very surprised since I always thought of Japan as being rich. I'm sure the wood would do well in the earthquake, but that's the other problem: wood eventually rots and needs to be replaced (those Shinto temples are rebuilt every 30 or 40 years I think).
Hey man, I live in Kobe :) Kyoto was left largely intact after the earthquake in 1995. Of course they felt it, but nothing was devastated there. Kyoto is further up in the middle of the land, further from the seismic rifts, and relatively safe in terms of location.
> (those Shinto temples are rebuilt every 30 or 40 years I think
I think you are refering to Ise Jingu which is destroyed and entirely rebuilt every 20 years. But that's a very different thing. Most large temples no not get rebuilt very often, and their trunks can last centuries.
I think you are referring maps of the risks related to an earthquake (ex: tsunamis, landslides, rivers overflowing, wide range fires) and not the risk of getting an earthquake.
In Tokyo, the area of Odaiba would be a super high risk area due to the artificial soil and the proximity to the ocean for instance.
I've lived in both SF and Tokyo, and agree with this statement. Put simply, seismic danger is a Much Bigger Deal(tm) in the latter. It's on everyone's mind, and it's reflected in just about any and every building you enter.
I don't have hard data to support my case, but at least in terms of noticeable seismic activity there really is no comparison. I probably experienced more tremors during any given month in Tokyo than I did during a full year in SF.
7.0 doesn't sound big, but keep in mind, the epicenter would be quite close to the surface and likely to be right in the middle of a highly populated area on the Wasatch Front (Salt Lake City, Cottonwood Heights, etc). Also, many buildings in the vulnerable areas pre-date construction codes that take seismic risk into account. For example, it wasn't until the late 70's that they started reinforcing masonry construction.
[1] http://www.livescience.com/28782-utah-bigger-earthquakes-was...
Note that it's really not clear to what extent faults rupture periodically; there are researchers who argue that the likelihood of an event is basically independent of the time since the last event (basically a Poisson distribution), those who argue for fairly regular events, and everything in between. It probably varies a lot from fault to fault and is more regular on big plate boundary faults like the San Andreas than on smaller (or slower-moving) intraplate faults like the Wasatch Fault.
The real danger, both here and for the San Andreas system, is that an earthquake will break through the segment boundaries and cause a much, much larger earthquake. It's not been demonstrated that this is has happened on the Wasatch fault (there is one instance about 6000 years ago where this is possible within the data uncertainty) but this has happened in California in the 1906 S.F. and 1857 Fort Tejon earthquakes. Although this might not cause more displacement of the fault in any one location, it creates such a bigger swath of destruction that there are more opportunities for associated disasters (fires, floods from dams breaking, etc.) and make response much more difficult. It's also a bit outside my expertise but I think that for a long rupture, there is enough constructive interference of surface waves from the earthquake that ground shaking is much greater than is predicted from displacement at any point on the fault.
[1]: http://michaelhaskinseportfolio.weebly.com/earthquake-hazard...
[2]: http://www.bssaonline.org/content/98/6/2918.short
The San Andreas is a strike-slip system. It's not capable of generating very large (magnitude 8 or greater) earthquakes.
The Cascadia subduction zone has had magnitude 9 earthquakes in the past. The last one was on Jan. 26th, 1700. (Thank Japan for having excellent historical records of earthquakes and tsunamis. We know a large earthquake occurred around 300 years ago in the area, and thanks to Japan's record of the tsunami it caused, we can make a solid link to the exact date.)
We don't know the statistical hazard as well due to the small sample size, but when the next large Cascadia earthquake occurs the damage will be absolutely catastrophic.
It's not just the direct earthquake damage, but also the tsunami hazard. You need vertical offset to cause a tsunami. A strike-slip system like the San Andreas is very unlikely to cause a tsunami. The permanent offset is dominantly horizontal, so the only way to generate a tsunami is through secondary effects such as landslides. (Also, most of the length of the San Andreas is onshore.)
Subduction zones are thrust systems. One plate moves up, and the other moves down. Earthquakes there are likely to produce permanent vertical deformation at the surface.
Furthermore, certain types of subduction zones are more prone to generating large tsunamis. A deep earthquake is unlikely to cause much deformation at the seafloor, and therefore doesn't generate as large of a tsunami. However, the shallower the rupture penetrates, the larger the deformation at the seafloor is, and therefore the larger the tsunami is. Certain types of subduction zones are more prone to having large earthquakes that rupture all the way up to the seafloor. (The amount of sediment on top of the incoming oceanic plate is thought to play a large role in this, among other things. The recent Tonankai earthquake in northern Japan turned a lot of what we thought we knew about this on its head, though.)
The Cascadia subduction zone is one of the end-member types that's likely to have both large earthquakes and large tsunamis. We know it has in the past, and it's likely to in the future. It's unusual in that most of the deformation along the fault occurs through periodic creep ("slow-slip events") that doesn't cause an earthquake. (Actually, as we're finding out, it's not that unusual around the world, but it was first observed and is best documented in Cascadia.) However, while this creep does relieve a significant portion of the accumulated elastic strain, it doesn't relieve all of it. The plate boundary fault is still accumulating elastic strain that will eventually be released in a large earthquake.
At any rate, just something to think about. The seismic hazard in the Bay Area can be reduced through proper engineering solutions. (Though SOMA is going to be in very rough shape for the reasons this article mentions. Lesson for next time: Don't bulldoze all the rubble into a pile and then build on top of it!)
For Cascadia, though, you can't engineer your way around a magnitude 9 earthquake and tsunami. You do the best you can, and try to avoid putting critical infrastructure near the coast.
http://faculty.washington.edu/allstadt/Kates_website/Seattle...
TL;DR - major landslides
Here's a video of an "underwater forest" discovered by some divers in Lake Washington, seemingly caused by a previous landslide: http://vimeo.com/35477614
Not sure what to say about all those houses in the west hills besides good luck...
They're all stocked up on organic, locally sourced emergency supplies, then?
Sorry, I couldn't resist. Worth the karma damage.
http://www.portlandmercury.com/portland/the-first-four-minut...
I moved back from Japan just a few months before the 2011 disaster.
Even though the fact of the potential for a high magnitude earthquake is well known absolutely no one (including myself) is prepared for it at all. I've certainly been meaning to fashion myself a "bug out bag" in case of a disaster but haven't gotten around to it...
Vancouver also has a liquefaction concern. The false creek flats area is filled in estuary/marsh and though it's largely industrial there are plans to move Emily Carr School of Art to that area. I live pretty close to it so I have no idea how affected I am. Even worse is the entire nearby suburb of Richmond (pop 175k) is built on an island of silt in the Fraser River and is probably pretty much entirely a liquefaction zone.
A large tsunami would be quite damaging lot of smaller coastal cities along the western coast, though. It's a major concern, at any rate.
Downtown Seattle is also built on a mudflat that caused countless problems in early Seattle history. Areas built on mudflats will be hit especially hard in an earthquake.
Unless you're trying to buy terrains for construction.
So only the riskiest buildings get it.
So the average customer of the insurer skews ever closer towards the extremely at-risk end of the spectrum.
So the insurance companies have to raise the rates and deductibles.
And then you go back to step one, and the vicious cycle gets even more extreme.
> So the average customer of the insurer skews ever closer towards the extremely at-risk end of the spectrum.
> So the insurance companies have to raise the rates and deductibles.
This chain of "logic" only makes any sense if you assume that the insurance companies have to offer all their customers the same rates and deductibles. If the building owners can figure out that they're facing an elevated risk, why can't the insurance companies?
It's not that simple, but it is that heavily-regulated:
http://law.onecle.com/california/insurance/10089.html
Yes, there's a threat of earthquakes. Yes, I'm sure there is going to be an earthquake at some point, possibly even large. I experienced a tiny earthquake in SF a few years ago and it scared the shit out of me, because my entire apartment was shaking.
But there are threats everywhere. Would I buy a house (if I can afford one, that is) in a liquefaction area? No. But there are plenty of areas of SF that don't have imminent liquefaction risk. And the chance of actually dying is quite low. There are plenty of things to worry about, but earthquake would be on the bottom quartile for me. And compared to the benefits of living in SF, it isn't even a big concern.
Most of us understand that its not a matter of if, but when we will need those emergency supplies, but as someone pointed out earlier, we are "whistling past the graveyard."
http://www.sfgsa.org/index.aspx?page=6048
"On the anniversary of the 1906 San Francisco Earthquake, Mayor Ed Lee signed into law the Mandatory Soft Story Retrofit Ordinance. This legislation requires the evaluation and retrofit for “multi-unit soft-story buildings,” defined as: Wood-frame structures, containing five or more residential units, having two or more stories over a "soft" or "weak" story, and permitted for construction prior to January 1, 1978."
Unfortunately, I'm sure there will be a taxpayer funded bailout of all these people once their homes are damaged/destroyed in the next big one. So, why bother?