Club PA 2.0 has arrived! If you'd like to access some extra PA content and help support the forums, check it out at patreon.com/ClubPA
The image size limit has been raised to 1mb! Anything larger than that should be linked to. This is a HARD limit, please do not abuse it.
Our new Indie Games subforum is now open for business in G&T. Go and check it out, you might land a code for a free game. If you're developing an indie game and want to post about it, follow these directions. If you don't, he'll break your legs! Hahaha! Seriously though.
Our rules have been updated and given their own forum. Go and look at them! They are nice, and there may be new ones that you didn't know about! Hooray for rules! Hooray for The System! Hooray for Conforming!

The [Cascadia Subduction Zone] Can't Wait to Kill You

The EnderThe Ender Registered User regular
CSZ.jpg


...So, there's an issue that I don't think is discussed as much as it should be given the scale & seriousness of the situation:

The Cascadia Subduction Zone, which was thought to be dormant / aseismic up until the late 80s because of a dearth of documented earthquakes in the region since European settlement, is now known to actually be a mega-thrust earthquake risk; a region that is only mostly silent because the plates lock together and build-up pressure over hundreds of years rather than decades before rupturing, sometimes across the entire fault line.

Events at this zone would likely mirror the event in terms of energy release seen off of Japan's coast in 2011 - and that quake killed over 15,000 people in Japan, even despite the rather staunch building codes & precautions taken by the state. British Columbia, Oregon & Washington, by comparison, have essentially zero interesting earthquake preparation programs and little to no earthquake related building codes. The fact that the fault is usually so quiet (although you do certainly still feel tremors here on Vancouver Island once or twice a year) disguises the menace, making it far too easy to ignore and difficult to have a serious discussion about (much less try to create policy to address the problem).


Are We Sure This Is a Problem? Scientists Were Saying Different Things [X] Years Ago...

There were competing theories about why this subduction zone seemed so atypically quiet for a geologically active region; either the pressure was being released by some mechanism, or the fault was locked and building-up pressure for abnormally long periods of time. As science does, there were debates over the competing theories and (much warranted) skepticism over the most alarming possible scenario. Researchers from the USGS & the Japanese equivalent (I apologize but I cannot for the life of me find the translated name of the organization) surveyed the coast & dug into First Nations histories for evidence; they found entire red wood forests that had been violently plunged into salt water, stories & myths that corroborated the hypothesis of previous cataclysmic seismic activity and arrow grass blanketed by tsunami sediment. Tree ring dating from the red wood 'ghost forests' suggested that they had died around the year 1700~. Records of an 'orphan tsunami' striking Japan - a wave that did not, from their perspective, appear to be accompanied by an earthquake - were found, which further corroborated the data and also provided a precise date:

January 26, 1700, at about 9 o'clock in the morning.


All of the above was established around 1987. Since then, evidence has been uncovered of about 41 events in the last ten thousand years, 19 of them likely to have been full length ruptures of the fault line.

The Geological Survey of Canada's most recent study suggests that the fault line's most severe events have a recurrence interval, on average, of about once every 480 years. For events less severe than a full rupture (but nevertheless quite powerful), the recurrence interval averages out to about once every 240 years. We're about 316 years away from that last major rupture in January of 1700 - so we're coming close to being due for a real bad day.


So What Can We Even Do About This?

On a state level, we ought to be lobbying for some amount of budget allocation to both study & prepare for the earthquake that is going to be coming (unfortunately, earthquake forecasting is basically impossible; but more information on the phenomena never hurts). We need preparation plans that give respect to the danger being presented.

We also need a very large investment in upgrading homes, businesses, large free standing structures (towers & skyscapers, for example), which are not currently built to do anything other than crumble in the event of a quake.


On a personal level: make sure your home is anchored to it's foundation. If it isn't, see if there is any kind of program available in your area for retrofitting your home to get it anchored. Consider getting rid of shelving units that are large and free standing, or so if it is reasonable to secure them to the wall. Likewise, see if it is reasonable to get your large appliances secures to the wall or floor. Consider getting latches for cupboard doors and/or retention straps, to prevent everything from becoming shrapnel in the event of a quake.


Put together a reasonable, accessible & portable survival package. Some basic food that doesn't need cooking, a day or two worth of drinking water, a first aid kit, etc. Many people do just fine in the initial wake of the impact but find themselves trapped in their home or apartment with nothing to eat or drink until they're found - having a kit handy may prevent you from being among those folks.


If We Roll Snake Eyes On the Earthquake Dice Tomorrow, What Do I Do?

If you are outside, stay outside. If you are inside, stay inside. The most dangerous place to be is near an exterior wall of a house or building (...well, except maybe for being inside a skyscraper. Then you're pretty boned, sorry; just pray that it doesn't pancake).

If you are inside, you want to find what search & rescue teams have dubbed 'survivable void space' - get underneath a sturdy object (no, your Ikea night stand does not count) to use as a shelter against the ceiling coming down (and/or other heavy objects falling) and hold on. DO NOT STAND IN A GODDAMN DOORWAY! Doorways only work if the house has been built to withstand earthquake shocks, and if you live on the west coast, yours hasn't been.

If you are outside, stay away from big heavy things that could fall on you and try to reach high ground.

If you live right on the coast, there's going to be a tsunami coming your way; after the shaking stops, do your damndest to get to high ground.

Don't try to be a hero in the heat of the moment; if you feel compelled, search & rescue will no doubt be looking for volunteers once the immediate danger has passed.

With Love and Courage

Posts

  • tinwhiskerstinwhiskers Registered User regular
    The Ender wrote: »

    The Geological Survey of Canada's most recent study suggests that the fault line's most severe events have a recurrence interval, on average, of about once every 480 years. For events less severe than a full rupture (but nevertheless quite powerful), the recurrence interval averages out to about once every 240 years. We're about 316 years away from that last major rupture in January of 1700 - so we're coming close to being due for a real bad day.

    So I see people say stuff like this all the time and I know there are underlying forces at work, but it always reminds me of the gambler's fallacy.

    knitdan
  • GoumindongGoumindong Registered User regular
    edited July 2016
    The Ender wrote: »

    The Geological Survey of Canada's most recent study suggests that the fault line's most severe events have a recurrence interval, on average, of about once every 480 years. For events less severe than a full rupture (but nevertheless quite powerful), the recurrence interval averages out to about once every 240 years. We're about 316 years away from that last major rupture in January of 1700 - so we're coming close to being due for a real bad day.

    So I see people say stuff like this all the time and I know there are underlying forces at work, but it always reminds me of the gambler's fallacy.

    There is a bit of a fallacy but not much. The probability of an earthquake along a fault should increase as time goes on, since its a pressure building mechanism which causes the quakes. Unless something happens to reduce the pressure and so reduce the risk.

    The real issue is that we aren't actually "super due".
    The Ender wrote: »
    We also need a very large investment in upgrading homes, businesses, large free standing structures (towers & skyscapers, for example), which are not currently built to do anything other than crumble in the event of a quake.

    Well no this isn't true. Its partly true that a lot of structures aren't built to withstand large earthquakes but well, this is true everywhere. The Pac NW's earthquake preparedness is similar to Japans with regards to the structural soundness of buildings. Lots of unreinforced masonry and unsecured wooden structures in Japan too.

    The second issue is that approximately zero skyscrapers are actually close to the fault line. The closest significant city is probably OSU and its about 75-100 miles from the zone. Portland is at least 100 miles away, Seattle and Vancouver 150. To compare, the center of LA is about 25 miles from the San Andres Fault. Seattle and Portland and Vancouver are almost as far away as Las Vegas is from the San Andres Fault. For Seattle at least a M7 along the Seattle fault would almost certainly be more damaging.

    That isn't to say that these cities wouldn't feel it, but it is to say that there are more dangerous fault lines for them. (plus the overall risk from Volcanoes is probably higher)

    The real issue is that there aren't any early warning systems. On the other hand early warning systems might not do much. If the big one hits people will know to get to higher ground. But an early warning system won't give you enough time to make it to higher ground if you're on the coast, before the shock hits. Which means you're almost certainly not making it to higher ground.

    The good news is that very few people actually live in these regions, and there are almost zero low elevation or funneled tsunami risk areas. There is a significant mountain range between every major city in the Pacific Northwest and the Cascadia subduction fault. This is why death toll estimations from full fault ruptures still come in at less than the Japanese 2011 Tsunami. Which is terrible yes, but not end of the world terrible. Japan still exists. Tokyo did not fall over.

    Edit: on phone so not going back through but if I say "Vancouver" I probably mean "Victoria". Since one is on the other.

    Goumindong on
    wbBv3fj.png
  • cckerberoscckerberos Registered User regular
    The Ender wrote: »
    the Japanese equivalent (I apologize but I cannot for the life of me find the translated name of the organization)
    The Geological Survey of Japan (or maybe their Research Institute of Earthquake and Volcano Geology)?

  • WiseManTobesWiseManTobes Registered User regular
    It better not hit until after I see the Hip on the 26 th.

    Steam! Battlenet:Wisemantobes#1508
  • The EnderThe Ender Registered User regular
    Goumindong wrote: »
    The Ender wrote: »

    The Geological Survey of Canada's most recent study suggests that the fault line's most severe events have a recurrence interval, on average, of about once every 480 years. For events less severe than a full rupture (but nevertheless quite powerful), the recurrence interval averages out to about once every 240 years. We're about 316 years away from that last major rupture in January of 1700 - so we're coming close to being due for a real bad day.

    So I see people say stuff like this all the time and I know there are underlying forces at work, but it always reminds me of the gambler's fallacy.

    There is a bit of a fallacy but not much. The probability of an earthquake along a fault should increase as time goes on, since its a pressure building mechanism which causes the quakes. Unless something happens to reduce the pressure and so reduce the risk.

    The real issue is that we aren't actually "super due".
    The Ender wrote: »
    We also need a very large investment in upgrading homes, businesses, large free standing structures (towers & skyscapers, for example), which are not currently built to do anything other than crumble in the event of a quake.

    Well no this isn't true. Its partly true that a lot of structures aren't built to withstand large earthquakes but well, this is true everywhere. The Pac NW's earthquake preparedness is similar to Japans with regards to the structural soundness of buildings. Lots of unreinforced masonry and unsecured wooden structures in Japan too.

    The second issue is that approximately zero skyscrapers are actually close to the fault line. The closest significant city is probably OSU and its about 75-100 miles from the zone. Portland is at least 100 miles away, Seattle and Vancouver 150. To compare, the center of LA is about 25 miles from the San Andres Fault. Seattle and Portland and Vancouver are almost as far away as Las Vegas is from the San Andres Fault. For Seattle at least a M7 along the Seattle fault would almost certainly be more damaging.

    That isn't to say that these cities wouldn't feel it, but it is to say that there are more dangerous fault lines for them. (plus the overall risk from Volcanoes is probably higher)

    The real issue is that there aren't any early warning systems. On the other hand early warning systems might not do much. If the big one hits people will know to get to higher ground. But an early warning system won't give you enough time to make it to higher ground if you're on the coast, before the shock hits. Which means you're almost certainly not making it to higher ground.

    The good news is that very few people actually live in these regions, and there are almost zero low elevation or funneled tsunami risk areas. There is a significant mountain range between every major city in the Pacific Northwest and the Cascadia subduction fault. This is why death toll estimations from full fault ruptures still come in at less than the Japanese 2011 Tsunami. Which is terrible yes, but not end of the world terrible. Japan still exists. Tokyo did not fall over.

    Edit: on phone so not going back through but if I say "Vancouver" I probably mean "Victoria". Since one is on the other.

    Well, the standards are the same except for the extra reinforced steel supports installed onto the superstructures of Japanese skyscrapers, the rubber padding & hydraulic shock absorbers that allow them to sway in the wake of S-Waves, the base isolation techniques used on hospitals & administrative buildings with large surface areas to keep them from being pulled apart...

    Hm. I guess one could say that actually they aren't very similar at all.


    San Andreas is a rather poor comparison; the worst day on San Andreas is an 8~ or so magnitude earthquake (also, because the region is so active, monitoring & public vigilance are prominent fixtures. It is much easier to have a serious conversation about earthquake safety in, say, Los Angeles than it is to have the same conversation in Victoria or Vancouver), which would release about 6~ percent of the energy of a 9~ magnitude full rupture from Cascadia (the Richter Scale is logarithmic in nature).


    velocity.jpg


    Here is the expected peak velocity for ground movement during a Very Bad Day. Victoria has plenty of tall buildings. No, there is not a mountain range between it and the sea or the fault line (although in fairness, it's tucked around a corner fro the expected surge, and there is no evidence around the region of past inundation). Nor is there a mountain range between Vancouver and the sea or the fault line. FEMA's estimates are mostly isolated to impact within the U.S.


    Early warning systems may or may not be of help (P-Wave monitoring systems could save an awful lot of lives if integrated into things like elevator controls & hospital equipment, as they are in Japan, although such retrofitting might be prohibitively expensive), but there is a lot of minimal cost things one can do around their own home in terms of just being more conscious of what sort of furniture & fixtures may not be appropriate to have around, where not to position heavy objects, not storing bottles of liquid in overhead cabinetry, etc, that can mitigate injuries / loss of life.

    With Love and Courage
  • CaedwyrCaedwyr Registered User regular
    The Ender wrote:
    Events at this zone would likely mirror the event in terms of energy release seen off of Japan's coast in 2011 - and that quake killed over 15,000 people in Japan, even despite the rather staunch building codes & precautions taken by the state. British Columbia, Oregon & Washington, by comparison, have essentially zero interesting earthquake preparation programs and little to no earthquake related building codes. The fact that the fault is usually so quiet (although you do certainly still feel tremors here on Vancouver Island once or twice a year) disguises the menace, making it far too easy to ignore and difficult to have a serious discussion about (much less try to create policy to address the problem).

    I am curious where you get this impression from? I work in the geotechnical engineering field in British Columbia and the National Building Code of Canada which is the basis of all more local building codes has devoted a substantial portion to seismic hazards and recommendations for design earthquakes to be used in structural designs for buildings and other civil infrastructure.

    The link here:

    http://www.nrc-cnrc.gc.ca/eng/solutions/advisory/codes_centre/code_adoption.html

    Shows the adoption of the NBCC across the country.

    You can use the seismic hazard calculator for the 2015 NBCC here:

    http://www.earthquakescanada.nrcan.gc.ca/hazard-alea/interpolat/index_2015-en.php

    To calculate the expected spectral acceleration (SA) for different time values and peak ground acceleration (PGA) for coordinates across Canada.

    The graphic maps showing accelerations for the 2015 and 1985/1995 NBCC seismic hazard maps across Canada can be found here.

    http://www.earthquakescanada.nrcan.gc.ca/hazard-alea/zoning-zonage/NBCC2015maps-en.php
    http://www.earthquakescanada.nrcan.gc.ca/hazard-alea/zoning-zonage/NBCC1985maps-en.php

    The design earthquake is based upon the 2%/50 years chance of occurrence, which is the same earthquake as the 1:2475 years event. Note that the probabilistic model does not mean that once every 2475 years we have a major event, but that those are the statistics for determining the probability of the event happening at any time.

    The national building code of Canada is updated every 5 years. The 2015 update takes effect this year (it always comes into effect one year after the named year).


    Now, if you want to say that the existing building codes prior to the 2015 code do not properly take into account the Cascadia subduction zone seismic hazard, then I would agree with you. This article from the Canadian Journal of Civil Engineering (one of the main geotechnical/civil engineering journals in Canada) goes into the changes in the 2015 code: https://tspace.library.utoronto.ca/bitstream/1807/69931/1/cjce-2014-0385.pdf
    And how they are related to the seismic hazard.

    One of the major changes between the 2010 NBCC and the 2015 NBCC is a transition from the use of historically measured values to determine the hazard to probabilistically modeled acceleration values. This is a substantially more firm foundation to base the code upon compared to the use of historical data because those only put values in where it has been measured and does not account for the maximum values that could be generated in a major subduction zone earthquake.

    If you want to be concerned, note that the majority of the dike systems in the Lower Mainland and Fraser valley are based on a big flood about 100 years ago and not any sort of watershed/flood analysis. If the dikes were reclassified as earth-filled dams, then they would all be found to have insufficient design capacity. Don't buy on the floodplain in most places in BC/Alberta for exactly this reason. The floods in Calgary a couple of years ago are a good example. I don't think that flood was even the 1:100 year event.

    So, in conclusion, there has been substantial attention paid to seismic hazard in the building codes for at least 30 years. The problem for an actual earthquake comes where buildings are older than that, and where the design earthquake in previous years was insufficient to model a major seismic subduction event along the Cascadia Subduction Zone.

    I'd also note that there is a number of earthquake preparedness steps that have been taken in the Greater Vancouver area to set up support networks, response hubs, and information for how people can prepare. It isn't as good as the systems they have in Japan, but in the last decade they have improved substantially and there are annual earthquake disaster drills across the region. I can't speak to the state of preparedness in Victoria and Nanaimo (and I have no idea what the presence of multiple old coal mines throughout Nanaimo does to their local seismic hazard/knock-on effects of an event).

    Otherwise, this is a cool post and thank you for the OP. There's a lot more we can be doing for earthquake preparedness and improving older structures. This is the source of the political football being played with education funding for the City of Vancouver which has a lot of old schools that need to be rebuilt or have expensive seismic upgrades. The province is demanding that schools have enrollment at 90% of their capacity in order to be considered for provincial seismic upgrade/replacement funding.

    rockrngerForara5ehrenDark Raven XDiplominator
  • HacksawHacksaw J. Duggan Wrestler at LawRegistered User regular
    I fully expect The Big One to absolutely demolish Seattle and Portland and all when it hits, earthquake resistant retrofits or no. So long as I die in my sleep I don't imagine I'll mind too much.

    So It GoesTicaldfjam
  • GoumindongGoumindong Registered User regular
    n
    The Ender wrote: »

    The Geological Survey of Canada's most recent study suggests that the fault line's most severe events have a recurrence interval, on average, of about once every 480 years. For events less severe than a full rupture (but nevertheless quite powerful), the recurrence interval averages out to about once every 240 years. We're about 316 years away from that last major rupture in January of 1700 - so we're coming close to being due for a real bad day.

    So I see people say stuff like this all the time and I know there are underlying forces at work, but it always reminds me of the gambler's fallacy.

    To explain further it's not really a gamblers fallacy because the probabilities do change when there isn't an earthquake.
    The Ender wrote: »
    Goumindong wrote: »
    The Ender wrote: »

    The Geological Survey of Canada's most recent study suggests that the fault line's most severe events have a recurrence interval, on average, of about once every 480 years. For events less severe than a full rupture (but nevertheless quite powerful), the recurrence interval averages out to about once every 240 years. We're about 316 years away from that last major rupture in January of 1700 - so we're coming close to being due for a real bad day.

    So I see people say stuff like this all the time and I know there are underlying forces at work, but it always reminds me of the gambler's fallacy.

    There is a bit of a fallacy but not much. The probability of an earthquake along a fault should increase as time goes on, since its a pressure building mechanism which causes the quakes. Unless something happens to reduce the pressure and so reduce the risk.

    The real issue is that we aren't actually "super due".
    The Ender wrote: »
    We also need a very large investment in upgrading homes, businesses, large free standing structures (towers & skyscapers, for example), which are not currently built to do anything other than crumble in the event of a quake.

    Well no this isn't true. Its partly true that a lot of structures aren't built to withstand large earthquakes but well, this is true everywhere. The Pac NW's earthquake preparedness is similar to Japans with regards to the structural soundness of buildings. Lots of unreinforced masonry and unsecured wooden structures in Japan too.

    The second issue is that approximately zero skyscrapers are actually close to the fault line. The closest significant city is probably OSU and its about 75-100 miles from the zone. Portland is at least 100 miles away, Seattle and Vancouver 150. To compare, the center of LA is about 25 miles from the San Andres Fault. Seattle and Portland and Vancouver are almost as far away as Las Vegas is from the San Andres Fault. For Seattle at least a M7 along the Seattle fault would almost certainly be more damaging.

    That isn't to say that these cities wouldn't feel it, but it is to say that there are more dangerous fault lines for them. (plus the overall risk from Volcanoes is probably higher)

    The real issue is that there aren't any early warning systems. On the other hand early warning systems might not do much. If the big one hits people will know to get to higher ground. But an early warning system won't give you enough time to make it to higher ground if you're on the coast, before the shock hits. Which means you're almost certainly not making it to higher ground.

    The good news is that very few people actually live in these regions, and there are almost zero low elevation or funneled tsunami risk areas. There is a significant mountain range between every major city in the Pacific Northwest and the Cascadia subduction fault. This is why death toll estimations from full fault ruptures still come in at less than the Japanese 2011 Tsunami. Which is terrible yes, but not end of the world terrible. Japan still exists. Tokyo did not fall over.

    Edit: on phone so not going back through but if I say "Vancouver" I probably mean "Victoria". Since one is on the other.

    Well, the standards are the same except for the extra reinforced steel supports installed onto the superstructures of Japanese skyscrapers, the rubber padding & hydraulic shock absorbers that allow them to sway in the wake of S-Waves, the base isolation techniques used on hospitals & administrative buildings with large surface areas to keep them from being pulled apart...

    Hm. I guess one could say that actually they aren't very similar at all.


    San Andreas is a rather poor comparison; the worst day on San Andreas is an 8~ or so magnitude earthquake (also, because the region is so active, monitoring & public vigilance are prominent fixtures. It is much easier to have a serious conversation about earthquake safety in, say, Los Angeles than it is to have the same conversation in Victoria or Vancouver), which would release about 6~ percent of the energy of a 9~ magnitude full rupture from Cascadia (the Richter Scale is logarithmic in nature).


    velocity.jpg


    Here is the expected peak velocity for ground movement during a Very Bad Day. Victoria has plenty of tall buildings. No, there is not a mountain range between it and the sea or the fault line (although in fairness, it's tucked around a corner fro the expected surge, and there is no evidence around the region of past inundation). Nor is there a mountain range between Vancouver and the sea or the fault line. FEMA's estimates are mostly isolated to impact within the U.S.


    Early warning systems may or may not be of help (P-Wave monitoring systems could save an awful lot of lives if integrated into things like elevator controls & hospital equipment, as they are in Japan, although such retrofitting might be prohibitively expensive), but there is a lot of minimal cost things one can do around their own home in terms of just being more conscious of what sort of furniture & fixtures may not be appropriate to have around, where not to position heavy objects, not storing bottles of liquid in overhead cabinetry, etc, that can mitigate injuries / loss of life.
    Nisqually in 2001 his .3 peak Gs. It was 53km under olympia. Olympia is still standing. Damage was minimal. The total energy from a M9 is much higher but it's also spread over a much larger area.

    Your map has .1 to .2 for Victoria for a worst case scenario rupture. Victoria will not fall down.

    Victoria does have a mountain range between it and the fault. The entire island of Vancouver is a mountain! You are on the back side of it. A tsunami will have to come through the straight and then go back around to hit the city.

    wbBv3fj.png
  • Phoenix-DPhoenix-D Registered User regular
    The other problem for Seattle specifically is parts of the city aren't on bedrock. They are on fill dirt made when a hill was demolished- dirt that isn't stable during an earthquake.

  • IncenjucarIncenjucar Audio Game Developer Seattle, WARegistered User regular
    edited July 2016
    A lot of this comes down to an insane price tag in areas which include cities already dealing with housing crises.

    I've had family barely get out of some of the California earthquakes and fires over the years as is... but we're at least a century away from the kind of political will required to pull off even the beginnings of meaningfully protecting ourselves from the slowly exploding rock we live on by cleaning up shoddy buildings and infrastructure

    Incenjucar on
  • GoumindongGoumindong Registered User regular
    Phoenix-D wrote: »
    The other problem for Seattle specifically is parts of the city aren't on bedrock. They are on fill dirt made when a hill was demolished- dirt that isn't stable during an earthquake.

    Largely industrial areas though. There is afaik no housing on liquifable ground.

    wbBv3fj.png
  • CaedwyrCaedwyr Registered User regular
    Goumindong wrote: »
    n
    The Ender wrote: »

    The Geological Survey of Canada's most recent study suggests that the fault line's most severe events have a recurrence interval, on average, of about once every 480 years. For events less severe than a full rupture (but nevertheless quite powerful), the recurrence interval averages out to about once every 240 years. We're about 316 years away from that last major rupture in January of 1700 - so we're coming close to being due for a real bad day.

    So I see people say stuff like this all the time and I know there are underlying forces at work, but it always reminds me of the gambler's fallacy.

    To explain further it's not really a gamblers fallacy because the probabilities do change when there isn't an earthquake.
    The Ender wrote: »
    Goumindong wrote: »
    The Ender wrote: »

    The Geological Survey of Canada's most recent study suggests that the fault line's most severe events have a recurrence interval, on average, of about once every 480 years. For events less severe than a full rupture (but nevertheless quite powerful), the recurrence interval averages out to about once every 240 years. We're about 316 years away from that last major rupture in January of 1700 - so we're coming close to being due for a real bad day.

    So I see people say stuff like this all the time and I know there are underlying forces at work, but it always reminds me of the gambler's fallacy.

    There is a bit of a fallacy but not much. The probability of an earthquake along a fault should increase as time goes on, since its a pressure building mechanism which causes the quakes. Unless something happens to reduce the pressure and so reduce the risk.

    The real issue is that we aren't actually "super due".
    The Ender wrote: »
    We also need a very large investment in upgrading homes, businesses, large free standing structures (towers & skyscapers, for example), which are not currently built to do anything other than crumble in the event of a quake.

    Well no this isn't true. Its partly true that a lot of structures aren't built to withstand large earthquakes but well, this is true everywhere. The Pac NW's earthquake preparedness is similar to Japans with regards to the structural soundness of buildings. Lots of unreinforced masonry and unsecured wooden structures in Japan too.

    The second issue is that approximately zero skyscrapers are actually close to the fault line. The closest significant city is probably OSU and its about 75-100 miles from the zone. Portland is at least 100 miles away, Seattle and Vancouver 150. To compare, the center of LA is about 25 miles from the San Andres Fault. Seattle and Portland and Vancouver are almost as far away as Las Vegas is from the San Andres Fault. For Seattle at least a M7 along the Seattle fault would almost certainly be more damaging.

    That isn't to say that these cities wouldn't feel it, but it is to say that there are more dangerous fault lines for them. (plus the overall risk from Volcanoes is probably higher)

    The real issue is that there aren't any early warning systems. On the other hand early warning systems might not do much. If the big one hits people will know to get to higher ground. But an early warning system won't give you enough time to make it to higher ground if you're on the coast, before the shock hits. Which means you're almost certainly not making it to higher ground.

    The good news is that very few people actually live in these regions, and there are almost zero low elevation or funneled tsunami risk areas. There is a significant mountain range between every major city in the Pacific Northwest and the Cascadia subduction fault. This is why death toll estimations from full fault ruptures still come in at less than the Japanese 2011 Tsunami. Which is terrible yes, but not end of the world terrible. Japan still exists. Tokyo did not fall over.

    Edit: on phone so not going back through but if I say "Vancouver" I probably mean "Victoria". Since one is on the other.

    Well, the standards are the same except for the extra reinforced steel supports installed onto the superstructures of Japanese skyscrapers, the rubber padding & hydraulic shock absorbers that allow them to sway in the wake of S-Waves, the base isolation techniques used on hospitals & administrative buildings with large surface areas to keep them from being pulled apart...

    Hm. I guess one could say that actually they aren't very similar at all.


    San Andreas is a rather poor comparison; the worst day on San Andreas is an 8~ or so magnitude earthquake (also, because the region is so active, monitoring & public vigilance are prominent fixtures. It is much easier to have a serious conversation about earthquake safety in, say, Los Angeles than it is to have the same conversation in Victoria or Vancouver), which would release about 6~ percent of the energy of a 9~ magnitude full rupture from Cascadia (the Richter Scale is logarithmic in nature).


    velocity.jpg


    Here is the expected peak velocity for ground movement during a Very Bad Day. Victoria has plenty of tall buildings. No, there is not a mountain range between it and the sea or the fault line (although in fairness, it's tucked around a corner fro the expected surge, and there is no evidence around the region of past inundation). Nor is there a mountain range between Vancouver and the sea or the fault line. FEMA's estimates are mostly isolated to impact within the U.S.


    Early warning systems may or may not be of help (P-Wave monitoring systems could save an awful lot of lives if integrated into things like elevator controls & hospital equipment, as they are in Japan, although such retrofitting might be prohibitively expensive), but there is a lot of minimal cost things one can do around their own home in terms of just being more conscious of what sort of furniture & fixtures may not be appropriate to have around, where not to position heavy objects, not storing bottles of liquid in overhead cabinetry, etc, that can mitigate injuries / loss of life.
    Nisqually in 2001 his .3 peak Gs. It was 53km under olympia. Olympia is still standing. Damage was minimal. The total energy from a M9 is much higher but it's also spread over a much larger area.

    Your map has .1 to .2 for Victoria for a worst case scenario rupture. Victoria will not fall down.

    Victoria does have a mountain range between it and the fault. The entire island of Vancouver is a mountain! You are on the back side of it. A tsunami will have to come through the straight and then go back around to hit the city.

    Actually, if you use the 2015 seismic hazard calculator I linked in my post, you get about 0.507 PGA for the 1:2475 designe earthquake for Victoria. That is very high.

  • GoumindongGoumindong Registered User regular
    edited July 2016
    The 2%/50 year earthquake is larger than a full fault on the Cascadia Subduction. Full Faults on the Cascadia line appear to happen every 500 years or so, which is 10/50 and not 2/50. You're looking at the line for earthquakes with a 2500 year period rather than the one for 500.

    Edit: A 2/50 earthquake is one that is so rare we barely have any data at all to suggest it could even happen. We are simply extrapolating from what we have an idea of to what we don't.

    Goumindong on
    wbBv3fj.png
  • So It GoesSo It Goes We keep moving...Registered User, Moderator mod
    Here's an article from the Portland Mercury

    http://www.portlandmercury.com/portland/the-first-four-minutes/Content?oid=5766214


    From what I've read and heard, one of the biggest hazards is all the chemicals we have stored right next to the river...yeah

    http://www.oregonlive.com/environment/index.ssf/2013/09/oregons_energy_hub_on_the_will.html

Sign In or Register to comment.