Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Earthquake in Japan yesterday may have shifted land 1.3 meters

www3.nhk.or.jp

Post reply on HN
Print view View original

51–60 of 87 posts

Re: Earthquake in Japan yesterday may have shifted land 1.3 meters

#51

Post by blacksmith_tb »

bee_rider wrote: post #40
chrismorgan wrote: post #30

Earlier quoted context omitted.

Australia’s geocentric datum is pretty boring, because Australia’s tectonics are pretty boring. We just don’t get large earthquakes. So the GDA94 → GDA2020 update is actually pretty minor. If my understanding is correct, the 1.8m difference sometimes talked of between ITRF92 and GDA94 by 2020 is actually irrelevant so long as you do proper projection of your coordinates, which you should , but some things don’t—and s…

Hi from New England, middle-of-the-plate buddy. In fact, it had never occurred to me that the mapping of parts of the ground to, like, latitude-longitude could be time dependent, haha. I guess this could make a big difference in surveying.

For most surveying wouldn't the the relative, nearby points be shifting together equally?

Re: Earthquake in Japan yesterday may have shifted land 1.3 meters

#54

Post by throwup238 »

IKantRead wrote: post #31
sandworm101 wrote: post #2

The amount of energy released in such events boggles the mind. Shifting cubic-kilometers of rock, in this case several hundred or even thousands of cubic-kilometers, even a few inches requires more energy than all the worlds nukes many times over. We live atop an immense heat engine, every little vibration of which could power our entire civilization for years.

I've always found it fascinating that geophysicist and earlier advocate for Bayesian methods, Sir Harold Jeffreys, didn't believe in continental drift and plate tectonics because he felt there was no known source of energy on the Earth massive enough to explain this movement. [0] He remained an opponent until death (at which point continental drift was widely accepted) which is both a testament to the literally unbel…

Another great illustration of Planck’s law:

> Max Planck, surveying his own career in his Scientific Autobiography, sadly remarked that “a new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it.“ -The Structure of Scientific Revolutions

Re: Earthquake in Japan yesterday may have shifted land 1.3 meters

#55

Post by roenxi »

thehours wrote: post #38
IKantRead wrote: post #31

Earlier quoted context omitted.

I've always found it fascinating that geophysicist and earlier advocate for Bayesian methods, Sir Harold Jeffreys, didn't believe in continental drift and plate tectonics because he felt there was no known source of energy on the Earth massive enough to explain this movement. [0] He remained an opponent until death (at which point continental drift was widely accepted) which is both a testament to the literally unbel…

Actually the lesson I take away is the importance of not having a 0% (or 100%) prior, since it leaves no room to update with new information.

It is also suspicious because it means someone has assigned a 0% prior to their being insane or in some sort of Plato's-cave scenario - which is hard to justify.

The minimum possible Baysian prior is a base rate of "my senses are just not picking up reality and/or my memory is catastrophically compromised and/or I cannot process logic right now due to some reason" which while low is never going to be 0%. There are too many known ways for human brains to fall over. 0% priors are unjustifiable.

Re: Earthquake in Japan yesterday may have shifted land 1.3 meters

#57

Post by dexwiz »

rwmj wrote: post #18
philip1209 wrote: post #5

How property rights work when land shifts?

In Japan property boundaries are (often) marked with physical markers embedded into the ground: https://www.japantimes.co.jp/community/2015/01/02/how-tos/pr... https://japanpropertycentral.com/real-estate-faq/land-bounda...

Survey spikes are common worldwide. The issue is that they are not always where you think they would be. They are positioned relative to each other, were placed years ago, or moved by unscrupulous land owners. And until relatively recently it was all done by one person using an optical device looking at another person standing there with a colored stick.

Surveyors are often called to resolve any discrepancies during disputes or sales.

Re: Earthquake in Japan yesterday may have shifted land 1.3 meters

#58

Post by sandworm101 »

barbariangrunge wrote: post #44
sandworm101 wrote: post #2

The amount of energy released in such events boggles the mind. Shifting cubic-kilometers of rock, in this case several hundred or even thousands of cubic-kilometers, even a few inches requires more energy than all the worlds nukes many times over. We live atop an immense heat engine, every little vibration of which could power our entire civilization for years.

I think we sort of have the tech to use geological energy, but I imagine the hardest part is not having your equipment destroyed all the time by quakes? You'd probably want to put your collectors deep underground where there's more activity

At a theoretical level, it could be done with ropes. You don't need to wait for earthquakes. Setup two anchors on either side of a fault. String ropes between them. As the two plates slowly more, the stretching ropes can be tied to generators. Totally theoretical but, no new physics is required to extract energy from two slowly moving things.

Re: Earthquake in Japan yesterday may have shifted land 1.3 meters

#59

Post by Retric »

Retric wrote: post #48
arghwhat wrote: post #35

Earlier quoted context omitted.

Not necessarily. Place a grid of receivers in fixed locations and observe their reported position. That grid is then the transform you need between the map when they were placed and the current state of the globe. A question would be how many you need, but these movements are on a large scale and receivers are dirt cheap.

A low resolution grid is cheap, but having enough censors for local accuracy is expensive because fault lines are so complicated: https://strangesounds.org/wp-content/uploads/2014/09/earthqu... What you really want is censers placed based on the underlying geology rather than a grid and then to combine that with a model of the geology.

*sensors

Re: Earthquake in Japan yesterday may have shifted land 1.3 meters

#60

Post by 1letterunixname »

4' in Freedom Units. I'm wondering how well utilities and megastructures on the Noto Peninsula are able to cope with gradual and sudden shifts, even in Japan where earthquakes are assumed. It looks like Noto is being ripped and stretched NW from the mainland.

---

Also, I re-read the Fukushima Daiichi report summaries yesterday. It's an almost universal human condition that plays out again and again: corporate risk management for large projects is done improperly, especially when there are constraints and cognitive dissonance imposed by the business culture, and it leads to a major failure.

Points of the failure chain include:

- Failure to account for known unknown risks such as the land subsidence combined with a large tsunami (based on the coastal geomorphology of the specific site).

- Failure to protect critical EDGs from flooding, e.g., seawater intrusion. If trying to run a diesel motor near the ocean, it must be buttoned-up tighter than a Jeep with a snorkel including waterproofing sensors, wiring, and control systems. In general, sites should be chosen on very high ground with a large safety factor. If that's not possible, they should be placed on elevated, reinforced structures.

- GE BWR-3/-4 (Mark I) core design is such that they can overheat and self-destruct, even if scrammed, because cooling is an absolute requirement at all times.

- A lack of redundant, auxiliary, passive cooling ability, such as a gravity-fed reservoir that can be operated manually.

- Regulators did insufficient due-diligence to prevent these risks.

- "Made in Japan" failure of culture (this was part of the final report).

- Using radionuclides that are inherently dangerous and produce forever waste rather than cheaper alternatives like solar with PES. Japan's solar just overtook nuclear, but still relies heavily on coal and gas. BWRs are inherently nastier than PWRs.

Non-problems at FD:

- Scramming worked properly, but the primary loops were still hot.

Disclaimer: Worked in the nuclear industry where hostnames were Simpsons' character names.

Post reply on HN