Science clarifies risks of “the really big one” for Seattle residents

All the recent hoopla regarding “The Really Big One” (2015 New Yorker article describing the terrifying possibility and risks associated with a magnitude 9 earthquake in the Pacific Northwest) motivated me to do two things: take some reasonable actions to be more prepared; calm my relatives down a bit by elucidating the risks of living with the Cascadia Subduction Zone based on my reading the relevant primary scientific literature.  The key to the latter task is clarifying two key parts of Schultz’s story:

“…the odds of the big Cascadia earthquake happening in the next fifty years are roughly one in three. The odds of the very big one are roughly one in ten.”

and (adding bold emphasis and changing written out numbers to actual numbers)

“Thanks to that [Goldfinger’s] work, we now know that the Pacific Northwest has experienced 41 subduction-zone earthquakes in the past 10,000 years. If you divide 10,000 by 41, you get 243, which is Cascadia’s recurrence interval: the average amount of time that elapses between earthquakes. That timespan is dangerous both because it is too long—long enough for us to unwittingly build an entire civilization on top of our continent’s worst fault line—and because it is not long enough. Counting from the earthquake of 1700, we are now 315 years into a 243 year cycle.

 

It is possible to quibble with that number. Recurrence intervals are averages, and averages are tricky…”

Ok, so let’s quibble by looking at Goldfinger’s work, specifically his analysis of layers of submarine mud that avalanche deeper into the sea during big earthquakes (a.k.a. turbidites).  In “Turbidite Event History—Methods and Implications for Holocene Paleoseismicity of the Cascadia Subduction Zone” (Goldfinger et al., 2012), you can find in the abstract the results that underlie Schultz’s prose:

The combined stratigraphic correlations, hemipelagic analysis, and 14C framework suggest that the Cascadia margin has three rupture modes: (1) 19–20 full-length or nearly full length ruptures; (2) 3 or 4 ruptures comprising the southern 50–70 percent of the margin; and (3) 18–20 smaller southern-margin ruptures during the past 10 k.y., with the possibility of additional southern-margin events that are presently uncorrelated. The shorter rupture extents and thinner turbidites of the southern margin correspond well with spatial extents interpreted from the limited onshore paleoseismic record, supporting margin segmentation of southern Cascadia. The sequence of 41 events defines an average recurrence period for the southern Cascadia margin of ~240 years during the past 10 k.y.

 

19+3+18=40 events, and 20+4+20=44 events

so it seems Schultz tries to be sort-of conservative and chooses to divide by 41:

10,000 years / 41 events = 243.9 years between events

= 244 year average recurrence time

We could get a range of recurrence times instead by using the range of number of events — 40-44:

10,000/40 = 250 years

10,000/44 = 227 years

And if we average those estimates, we’d get (250+227)/2 = 238 years

So, rounded down (for whatever reason) the bold math above yields (approximately) Schultz’s 243 year average recurrence time for a “big Cascadia earthquake” by which she means either a full-rupture earthquake (involving the whole boundary between the North American and Juan de Fuca tectonic plates, from British Columbia down to northern California) or a shorter/smaller ruptures at the southern half or 2/3 of the margin (CA and OR).  But we could break these averages down for big full plate ruptures (let’s assume 20 rather than 19), 50-70% southern ruptures, and smaller partial southern ruptures.  In the grey literature (not peer-reviewed) document “CHARACTERIZING THE CASCADIA SUBDUCTION ZONE FOR SEISMIC HAZARD ASSESSMENTS” Wong et al. (2014) make a similarly motivated division of earthquakes, assuming they would fall into groups of magnitude 9, 8-8.8, and <8.  Adopting a similar terminology (and implicit assumptions), we can go back to the Goldfinger abstract and calculate

10,000 years / 20 full-length events = 500 years between magnitude 9 events

10,000 years / 50-70% length events = 2,500 years between 8-8.8 events

10,000 years / 20 full-length events = 500 years between magnitude <8 events

In the spirit of quibbling, what magnitude earthquakes are we talking about in the New Yorker article?  Schultz implies we are talking about the really big (~9.0) and big ones (>8), but not the <8 events:

If, on that occasion, only the southern part of the Cascadia subduction zone gives way—your first two fingers, say—the magnitude of the resulting quake will be somewhere between 8.0 and 8.6. Thats the big one. If the entire zone gives way at once, an event that seismologists call a full-margin rupture, the magnitude will be somewhere between 8.7 and 9.2. That’s the very big one.

So maybe it would have been most appropriate for her to sum the number of these larger events from the turbidite record, but leave out what Goldfinger termed the “smaller southern-margin ruptures” —

10,000/(20+4) = 10,000/24

= 417 years between earthquakes greater than magnitude 8.0

If so, then we can transform one of her scariest sentences into something substantially less terrifying: “Counting from the earthquake of 1700, we are now 315 years into a 243 417 year cycle.”  So, on average we shouldn’t expect a big or really big earthquake for another 100 years or so.

If you want to get more geographically explicit, consider this nice figure from “Tsunami impact to Washington and northern Oregon from segment ruptures on the southern Cascadia subduction zone” (Priest et al., 2014), modified from Goldfinger et al. (2012) —

Yellow text show recurrence times for different inferred segments of the full-rupture patch of the Cascadia Subduction Zone.

Yellow text show (simple average) recurrence times for different inferred segments of the full-rupture patch of the Cascadia Subduction Zone.

Of course, all this averaging assumes that earthquakes are random (time-independent) rather than cyclical or periodic (time-dependent), but Goldfinger et al. (2012) point out that — conveniently — it doesn’t matter if you use simple averages or complicated earthquake modes, you get about the same computed likelihoods:

Time-independent probabilities for segmented ruptures range from 7–12 percent in 50 years for full or nearly full margin ruptures to ~21 percent in 50 years for a southern-margin rupture. Time-dependent probabilities are similar for northern margin events at ~7–12 percent and 37–42 percent in 50 years for the southern margin. Failure analysis suggests that by the year 2060, Cascadia will have exceeded ~27 percent of Holocene recurrence intervals for the northern margin and 85 percent of recurrence intervals for the southern margin.

These statistics are what underlie Schultz’s memorable 50-year odds: 1 in 3 (~30%) for a big one; 1 in 10 (~10%) for a really big one.  To the extent that either probability is worrisome, it’s got to be the 30% chance of a big one down south in the next 50 years.  Interestingly, in her follow-up article “How to Stay Safe When the Big One Comes” Schultz clarifies that the 30% probablity is indeed for a magnitude 8-8.6 event:

The odds I cite in the [original] story are correct: there is a thirty-per-cent chance of the M8.08.6 Cascadia earthquake and a ten-per-cent chance of the M8.79.2 earthquake in the next fifty years.

But from Seattle’s perspective, what will be our experience of a magnitude 8-8.6 earthquake, particularly one with an epicenter in Oregon?  It’s not clear to me if the shake maps Schultz provides in her follow-up are for a full- or partial- rupture.  The symmetry of the contours suggests they are for a full-margin rupture.  We need clarification, or another model run (for the full Northwest region) of this most likely (30%) type of earthquake!

The most helpful things I’ve found as I continue to “feel” the risk and decide whether and how to proceed are this timeline from this PDF

Seem likely the next one will be big, not really, big, and maybe pretty soon?

Seem likely the next one will be big, not really, big, and maybe pretty soon?

— and this figure depicting the height of a worst case tsunami as it moves up the OR/WA coast (from a magnitude 8.7 earthquake, aka simulation C588 centered in southern Oregon) —

As the tsunami propagates northward, the maximum wave height deceases from ~10 meters near the epicenter to ~2 meters in northern coastal Washington.  There is no tsunami risk in Seattle from a big or even a really big subduction earthquake.

As the tsunami propagates northward, the maximum wave height deceases from ~10 meters near the epicenter to ~2 meters in northern coastal Washington. There is no tsunami risk in Seattle from a big or even a really big subduction earthquake.

Despite all this scientific quibbling, I applaud Schultz on getting us all to be more prepared.  Here in northeast Seattle, I plan to refresh our emergency plans and kits, and look into a seismic retrofit for our 1926 house.

 

Re-thinking life, death, and purpose

After the death of my friend, Rafe Sagarin, I’m re-thinking the nature of life, death, and one’s purposes and values while on this planet.  Below are a few articles that I want to read and then discuss.

  • Matthieu Ricard in the New York Times (2011) regarding “The Future Doesn’t Hurt. Yet”
    • References a book written with his father “The Monk and the Philosopher
      • From an Amazon comment, the Monk sums up with:
      • `…such a dialogue is useful, but can never be a substitute for the silence of personal experience, as Goethe had aptly stated, “silence allows nature to whisper to us”.’
    • Review by Maria Popova
      • “When Revel takes issue with the Buddhist concept of reincarnation, pointing out its mystical and scientifically ungrounded suppositions, Ricard emphasizes its metaphorical and philosophical importance over its literal interpretation. Embedded in that notion, he suggests, is the key to unmooring ourselves from the tyranny of the self in the here and now:”
      • From the book: “It’s important to understand that what’s called reincarnation in Buddhism has nothing to do with the transmigration of some “entity” or other… As long as one thinks in terms of entities rather than function and continuity, it’s impossible to understand the Buddhist concept of rebirth.

        […]

        Since Buddhism denies the existence of any individual self that could be seen as a separate entity capable of transmigrating from one existence to another by passing from one body to another, one might well wonder what it could be that links those successive states of existence together… It’s seen as a continuum, a stream of consciousness that continues to flow without there being any fixed or autonomous entity running through it.

      • “The fact that there’s no such discontinuous entity being transferred from one life to the next doesn’t mean that there can’t be a continuity of functioning. That the self has no true existence doesn’t prevent one particular stream of consciousness from having qualities that distinguish it from another stream. The fact that there’s no boat floating down the river doesn’t prevent the water from being full of mud, polluted by a paper factory, or clean and clear. The state of the river at any given moment is the result of its history. In the same way, an individual stream of consciousness is loaded with all the traces left on it by positive and negative thoughts, as well as by actions and words arising from those thoughts. What we’re trying to do by spiritual practice is to gradually purify the river.”
      • “There’s a natural feeling of self, of “I,” which makes you think “I’m cold, I’m hungry, I’m walking,” and so forth. By itself, that feeling is neutral. It doesn’t specifically lead to either happiness or suffering. But then comes the idea that the self is a kind of constant that lasts all your life, regardless of all the physical and mental changes you go through. You get attached to the idea of being a self, “myself,” a “person,” and of “my” body, “my” name, “my” mind, and so on. Buddhism accepts that there is a continuum of consciousness, but denies any existence of a solid, permanent, and autonomous self anywhere in that continuum. The essence of Buddhist practice is therefore to get rid of that illusion of a self which so falsifies our view of the world.”
    • Founded Karuna-Shechen Foundation doing humanitarian work in Tibet, Nepal, etc.
    • “The unbridled consumerism of our planet’s richest 5 percent is the greatest contributor to the climate change that will bring the greatest suffering to the most destitute 25 percent, who will face the worst consequences.”
    • “Unchecked consumerism operates on the premise that others are only instruments to be used and that the environment is a commodity. This attitude fosters unhappiness, selfishness and contempt upon other living beings and upon our environment. People are rarely motivated to change on behalf of something for their future and that of the next generation. They imagine, “Well, we’ll deal with that when it comes.” They resist the idea of giving up what they enjoy just for the sake of avoiding disastrous long-term effects. The future doesn’t hurt — yet.

    • Interdependence, sentient living beings, suffering
    • “all beings are interrelated and all, without exception, want to avoid suffering and achieve happiness”
  • Harkening back to one of my childhood’s most trusted sources — Scientific American on “What Happens to Consciousness When We Die” (2012).  I’m not intrigued by the rather dull article, but inspired by the title and many of the comments!
    • “…the goal of enlightenment is to transcend to a more universal nonlocal, nonmaterial identity.” — Deepak Chopra?
    • “The hypothesis that the brain creates consciousness, however, has vastly more evidence for it than the hypothesis that consciousness creates the brain.”
    • “Thousands of experiments confirm the hypothesis that neurochemical processes produce subjective experiences.”
    • “2008 paper published in Mind and Matter by University of California, Irvine, cognitive scientist Donald D. Hoffman: Conscious Realism and the Mind-Body Problem. Conscious realism asserts that the objective world, i.e., the world whose existence does not depend on the perceptions of a particular observer, consists entirely of conscious agents.”
    • “In Hoffman’s view, our senses operate to construct reality, not to reconstruct it.”
  • Seven strange questions that help you find your life purpose” by Mark Manson

Exemplary quote from a “whole lake” ecologist

Would that I could come up with such eloquent prose when talking to the press about alarming environmental politics!

Here is what David Schindler said in the Tyee article about the Harper administration closing Canada’s world-famous archive of freshwater ecological research:

The library’s closing did not surprise retired water ecologist David Schindler. “In retrospect, I am not surprised at all to find them trashing scientific libraries,” he said.

“Paranoid ideologues have burned books and records throughout human history to try to squelch dissenting visions that they view as heretical, and to anyone who worships the great God Economy monotheistically, environmental science is heresy.”

Carl Sagan can change his mind

In science it often happens that scientists say, ‘You know that’s a really good argument; my position is mistaken,’ and then they would actually change their minds and you never hear that old view from them again. They really do it. It doesn’t happen as often as it should, because scientists are human and change is sometimes painful. But it happens every day. I cannot recall the last time someting like that happened in politics or religion.  — Carl Sagan, 1987 CSICOP address

Succinct goal to stabilize CO2

NASA’s Gavin Schmidt quote from his comment at 10:17 in a March 7 Congressional hearing live blog:

CO2 stabilisation requires cuts of 60-70% in emissions at some point in the next few decades (and the sooner it occurs the lower the stabilised value will be). That *will* require concerted international action, which is made up of national actions. The only ethical response is to work towards building the conditions for international action.

Marine algal biodiesel in Bermuda

Marine algae paste

Marine algae paste

Just caught this April, 2010, video of Dr. Michael Lomas making biodiesel from marine algae of the Sargasso Sea.  He’s getting yield of “about 1/2 coffee cup or 4-6 oz” of concentrated (1/100th human hair mesh opening) paste from an 80 liter culture.

Still no mention of open-ocean culture.  It’s all about scaling closed incubators up by 1000x volume.