What is the likelihood of a large magnitude earthquake in the next 50 years?
The likelihood for any large magnitude (~7.5 or higher) in Cascadia is currently thought to be ~37% +-10%. This is based on 41 likely paleoearthquakes over 10,000 years. Another way to think of these data is that we have presently exceeded ~75% of the recurrence intervals from these earthquakes, which average ~240 years apart, and it’s been 315 years since the last one. 50 years from now, we will have exceeded approximately all but 6 of them, or ~85%. There is a blog about these statistics here:
What are the magnitudes of the southern subduction zone earthquakes?
Magnitudes are the very hardest quantity to estimate for paleoeathquakes because we have no instrumentation for them. Estimates are based on the length, crude guesses about the widths, and information on plate locking and paleotsunami heights and runups; those are the tools we have. Based on these things, very rough estimates range from Mw = 7.5-8.7, based on this publication:
Where is the safest place to be during an earthquake?
Well truly, outside away from anything, and away from the coast.
How will a large magnitude earthquake impact power plants, bridges, and gas plants?
Currently the best source for information about disruption and repair estimates for infrastructure sectors is the Oregon Resiliency Report at this link:
How will wells in rural areas be affected by a large magnitude earthquake?
In general, much less than the urban areas. Most structures are wood frame, and if bolted down, pose low collapse/damage hazards. These areas may be more isolated for a longer time however, so storing some food and water could be more important the more remote the area is. Restoration of services, power, communications, and road repairs may also take longer as well.
How will coastal areas evacuate the injured after an earthquake?
If it is truly the “big one”, an M9 earthquake, the highways will likely be down along with many bridges. We will likely be relying on aircraft, mostly helicopters. There may well be support from the Navy, with helicopter carriers or larger aircraft carriers offshore, similar to what was done in Banda Aceh in 2004. If this happens during typical Oregon bad weather, this could be a major bottleneck.
What is the likelihood that the dams will break? If they do, how much time will we have to respond?
The likelihood of this is considered very low. Most dams perform resonably well in the modest ground motions expected well inland. Some are undergoing or have recently undergone beefing up by the Army Corps of Engineers. This is squarely on their radar and has been for a number of years. Evacuation time if required will depend greatly on proximity and whether or not there are precursory signs of damage, which there very likely will be.
How long will it take to restore communications after an earthquake?
This is one of the more difficult things to estimate. The telecom companies were less willing to share estimates of this because this is proprietaty to their business. Nevertheless, the best source for information about disruption and repair estimates for infrastructure sectors is the Oregon Resiliency Report at this link:
How bad will damage be to mobile homes?
Well, mobile homes actually sitting on their tires have built in “base isolation” and my guess is that they will do well. Others that are sitting on blocks may well slide off and suffer damage. However, the frames are steel and so the damage be modest. On the other hand, they have the same problems as a house sliding off its foundation in terms of rupturing the gas line and would be a fire hazard in that case. Knowledge of how to shut off the gas and having an open end wrench to do so nearby, or better yet, an automatic gas shutoff valve would be good. For the same reason, breaking power connections would also create a hazard if there is not enough slack to allow for some motion.
How is it decided which building gets retrofitted (e.g., Straub Hall vs. Prince Lucien Campbell Hall on the University of Oregon campus)?
Beginning in 2007 the legislature began making funds available to address seismic remediation and deferred maintenance issues on higher education campuses.
At the University of Oregon funds have been awarded to remediate Fenton, Straub, and Chapman Halls. Prior to then Pederson Hall was remediated using a combination of state and privately donated funds and in 2011 Anstett Hall was remediated using only private funds.
Similar efforts will continue in the future to remediate additional buildings as funding becomes available. [JB via Krista Dillon]
Where can I get updated hazard and inundation maps?
Here is an assortment of links to hazard and inundation maps: