Oversized aircon v. Inverter

We compare here the performance of an older high powered air conditioner(OHP), ceiling split type, with a newly installed replacement, an inexpensive ($US 450 installed) Mitsubishi inverter (MI) wall unit at about one third the power (ie BTU/hr) of the old one.

The MI wins, hands down.

Why?

The Xe Pian Lao dam failure of July 2018

Blume center article published October 2018

https://blume.stanford.edu/news/new-space-data-offer-instant-clues-cause-deadly-laos-dam-disaster

Asia Times article by Jim Pollard, broader coverage of issue

https://www.asiatimes.com/2018/11/article/collapsed-lao-dam-was-built-on-a-sinkhole/

The Earthquake that Haunts

Long before Fukushima  there was one earthquake that counted the most for the Diablo Canyon nuclear plant, and that earthquake has been kicked around now for half a century. Today I received a copy of that much discussed but rarely seen report on Diablo Canyon seismicity written by Hugo Benioff and Stewart Smith, which I include in full later in this post. True,  the findings date to the mid 1960s when many things were not known. As Smith put it to me in retrospect:

In the Geological Sciences we were still puzzled over the worldwide distribution of seismicity because the plate tectonic model had yet to be discovered.  Benioff had much earlier  recognized dipping zones of earthquakes, which we now call subduction zones, off the coast of South America and elsewhere, but there was not yet an overarching theory to explain how these were related to features like the San Andreas, which we now recognize as  transform fault necessary to account for the plate motion produced by subduction.  As I recall this was an era in which Clarence Allen at Caltech had pronounced that, based on the widespread nature of aftershocks in Chile, a large earthquake could occur anywhere in California.  I don't recall the reference, but I do remember the slide he would show where he overlaid the aftershocks of the Chile earthquake of 1960 on a map of California.  The entire state was filled with earthquakes.

Victor Hugo Benioff

But the Benioff-Smith report conveys remarkably sound judgment in many respects, notably in its conclusion that the Diablo site is subject to a magnitude 6 3/4 earthquake occurring directly beneath the plant. The effects of exactly this type of event have just been presented by PG&E and its SSHAC committee to the NRC, and they are worth examining, contradicting as they do key elements of  the Benioff-Smith conclusion and design recommendation. We can easily and will examine this proposition later by using various online tools to estimate ground shaking at the Diablo Site and in a manner that should be understandable to any bright high school student. 

The key finding of the Benioff-Smith report comes in the last paragraph of the report:

Can you find the fault "hosting" this "earthquake"

I like the picturesque metaphor of faults "hosting" earthquakes. Faults as metaphors: I went into this in my last book, perhaps too deeply.

However, do faults really cause anything? Or are they results, not causes? I hold that the foregoing video clip, which can be profitably watched several times, opens a door to world of physics in which certain premises and statistics of the SSHAC process, set forth in naked naivete in the defining NRC SSHAC document, simply disappear. By SSHAC premises, I mean the following axiom presented in the defining NRC document:

It is universally true that earthquakes are the result of differential slip on faults. However, in many areas, such as most of the eastern U.S., the identification of the causative faults giving rise to seismicity is problematic. To accommodate this uncertainty in fault location..... SSHAC 1997 NUREG CR-6372

The SSHAC process urges, not surprisingly given its adherence to this non-mathematical doctrine, even greater and better funded attempts to seek "causative" faults in the hidden depths. All of this follows a fifty year old idea that earthquake forecasting can be carried out using a model such as:

Find faults>

characterize earthquake style and magnitude>

determine distance and geological transmission path to site>

import and adjust various seismic recordings from other sites.

The probabilistic version of this procedure,  which was originally proposed for Central Mexico by Emilio Rosenblueth and Luis Esteva, mainly with distant earthquakes and long-period ground motions in mind, was elaborated in the mid 1960s by engineer Alan Cornell. It subsequently accrued other paste-in assumptions relating to inter-earthquake temporal probability theories, site effects, and so on. Geologists loved this idea, it lent a quantitative prestige to their poetical approach to nature. Hard to imagine that we once considered all this highly sophisticated, but we can now in the post Fukushima era, be permitted to ask whether it provides valid guidance. Some geophysicists imply it may not. Consider the implications of the following:

Should we be really be surprised at doubts about using a single number founded on Professor Richter's solitary star gazing habits, signals recorded at great distance as a base,  to characterize ground vibrations in the immediate vicinity of an inferred epicenter of a M6 earthquake? Not any more than having doubts about a Boston Red Socks'  bettor's  relying on either the distant roar of the crowd, or (to approach it from the opposite direction,)  from the bleacher seats populated by home town fans.

And as for that idealized "causative fault", consider the video clip at the top of the page. Does the reader find such a distinct fault  there?

(Add to this later: the question addressed in stock descriptions of probabilistic seismic hazard analyses, as compared favorably with "deterministic" straw man methods embodying complete ignorance of how engineers actually make design decisions. Add here too a Monte Carlo analysis showing how breaking the problem down into "causative" steps increases rather than decreases the uncertainty...add further how the assumptions of characteristic earthquakes based on similar Newtonian correlations was the fatal misconception in Fukushima in 2011...the questions are piling up here like traffic on the San Diego freeway)

Ambraseys' Lorry

Of all the professors over the years Nick Ambraseys was my favorite. Greek by birth, he brought some Meditteranean sunshine into the lecture hall on those grey drizzly days of the mid sixties in South Kensington. He made it clear that he thought things were pretty simple and he invited us to see it that way too. “Particle velocity? You know that already, maybe you just haven’t thought about it. If you can know the strength of the rock, and the shear wave velocity doesn’t vary much, so…” and he would turn to the blackboard and make a little sketch and it was just like he said, easy. He liked solutions to problems too. He was working on a way to use steel straps from packing crates to hold mud brick houses together, like something you would see in years to come in “The Whole Earth Catalog”.

Ambraseys was interested in the effects of earthquakes on dams and originated several of the ideas that became mainstream in seismic studies of dam safety in California in the 1970s, especially after the near catastrophe of the San Fernando dam failure. These included dynamic response

1963: A long bus ride through the Hindu Kush

I began my engineering career in the early 1960s, an era  when big was beautiful. This was also a time of great rivalry between the US and the Russians. As often as not this required demonstrations of who was the bigger man. Edward Teller, who will make a guest appearance later in this story, had designed and tested his hydrogen bomb on a Pacific island a few years before; the stolen Russian version inspired rational terror in us all in the following year. My first experience with a nuclear weapon was as a young army lieutenant in 1961 -- a later post for this blog -- and the Berlin blockade, followed soon after by a near miss of war in the Cuban missile crisis. There was a good deal of talk of Atoms for Peace too. The Bay Area Vallecitos plant, said to have been assembled from the innards of a Russian submarine,  was commissioned in the late 1950s, and by 1963 PG&E, having failed to build a plant at Bodega Bay near San Francisco, had purchased a lonely coastal site at Diablo Canyon, even securing an endorsement from the Sierra Club that this would be a good site for a 2000 Mw plant.

Afghan "terrorist" country today,  
peaceful in 1963 when I took 
my  long bus ride through the 
Hindu Kush

In those days my fondest dreams were about building big dams. I try now to recover that feeling. Was it fear or bravery that drove us to these things? The Russians had talked the Egyptians into letting them build the Aswan dam. One of my jobs, just out of the army, working for a famous engineering firm of the distinguished old fashioned partnership type, in New York City was to engineer a way to save the temples of Abu Simbel from the destructive rising waters behind Aswan. But we had some big dam tricks too, embodied in the great Tarbela Dam in Pakistan, which created an enormous 300 foot deep reservoir on the Indus River, then and now the biggest dam in the world and producer of almost twice as much power as Diablo Canyon.  MIT engineer John Lowe was in charge of that project,

Worried about acceleration?

Ambraseys first law of earthquake
engineering, Imperial College, 1965.
Solid line good, dashed line, bad

In the old days engineers who were old timers (back then, I was a new kid) used to talk about horizontal ground acceleration as the principal source of   disturbance, damage, and failure in structures. Then in the late twentieth century we had some medium sized earthquakes like San Fernando and Northridge down in LA, with these big sharp accelerations, one g or more, twice as much as what experts like George Housner and Nathan Newmark, whom we all respected, had said would be likely in earthquakes; these leaders had led us to believe (we said to ourselves) that we didn't have to worry about more than 0.5 or 0.6g, that's about all the geophysics of the earth could produce and even my prof, Nick Ambraseys, (I've got it her somewhere in my 1965 lecture notes at Imperial College, something about stress drop and velocity and limits.) So everyone, seeing these high accelerations began to waffle around: There must be something wrong about this record. Or: just hold on here, my structure, it doesn't care about high frequency vibration, it worries about longer period motion. 


And then the vision of those old WW2 army barracks being pulled down comes back, that long noisy gradual fall.

Cal Tech engineer Tom Heaton, whose style is much in the solid practical tradition of George Housner or Nick Ambraseys, suggests that designing for peak ground acceleration or for targeted response frequencies, could even be dangerously misleading:

While I understand that many structural fragilities are described in terms of PGA, its use only leads to dangerous mischaracterization of earthquake risk....5% damped response spectral acceleration (sa) is also a common parameterization of shaking intensity. While SA is certainly more useful than PGA, there are serious concerns about using it to predict structural demand. In particular, sa is based on a linear analysis of a structure about its undeformed state. However, there will always be significant ductile yielding prior to catastrophic failure of a structure, and it is more meaningful to use parameters that better characterize a structure that is in its highly deformed state. For example, structures that yield plastically have much lower effective stiffness and much higher effective damping than is typically assumed in current practice.