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Killer Qualities of Japanese Fault Revealed
Lasrick sends this report from Nature News:
"The devastating 2011 earthquake and tsunami in Japan shocked researchers who did not expect that the seismic fault involved could release so much energy. Now the world's deepest-drilling oceanographic ship has been able to pin down the odd geology that made this disaster so horrific. The fault turns out to be unusually thin and weak, the researchers report in Science this week1–3. The results will help to pin down whether other offshore faults around the world are capable of triggering the same scale of disaster. ... The coring revealed a very thin clay layer, about 5 meters thick, separating the two sliding tectonic plates (abstract). 'That’s just weird,' says Emily Brodsky of the University of California, Santa Cruz (UCSC), who is an author on all three Science papers this week. 'Usually it’s tens of meters or more.' Lab tests confirmed that this wet clay layer is extremely slippery, and gets even more so under stress (abstract). As sliding creates friction and heat, water in the clay gets pressurized and pushes up against the impermeable rock around it. That 'jacks open the fault” says Brodsky, allowing it to slip even more. The temperature sensors found that more than a year after the quake, the fault was still up to 0.31 C warmer than its surroundings (abstract). From this they could extrapolate how much heat was generated from friction during the sliding event. Their calculations confirmed the very low friction of the 5-meter-thick clay layer."
The first couple times I saw the title I thought it said "Killer Qualities of Japanese Fruit Revealed". Granted, that also could have been really interesting.
Damn_registrars has no butt-hole. Damn_registrars has no use for a butt-hole.
Perhaps by drilling millions of holes; and driving millions of rods of steel rebar into the clay, to reinforce the fault line.
Just get some Utah Boy Scout leaders to give that fault a nice shove. It's all about saving lives!
Statistically, five meters really isn't much different from ten meters, or twenty meters, or even thirty meters. It's only when you get to about 80 meters or so that we see a statistically-significant deviation from the standard probability distributions.
And you know this because you have the distribution of thicknesses and computed the standard deviation. Right?
Otherwise, you just pulled 80m out of your ass. That must have hurt.
After all, I am strangely colored.
Not all. Some actually were a bit smarter and there is this one small village that had flood gates high enough because the Major looked at historic flood markers, and then pushed through what was actually needed. This just means that people in general are stupid and blind and only see what they want to see. The few exceptions demonstrate that the facts are actually there, but are getting ignored. However I see no indication that Japanese women are smarter then the "Herbivores". In fact, they seem to fit right in.
Most ACs are not even worth the keystrokes to insult them. Be generically insulted by this and ignored otherwise.
Geologists are typically extremely competent fellows with no political agenda. The field is just too slow and usually non-spectacular for that. I suggest you read the articles instead of calling them incompetent, however indirectly you are doing it.
As to speed, do you know how long the review process in a reputable Journal can take? The delay is just average here.
Most ACs are not even worth the keystrokes to insult them. Be generically insulted by this and ignored otherwise.
Most of the info is in the Nature article, the paper, though probably funded by the taxpayes, is securely behind the AAAS paywall. Maybe Congress, if it had any balls, would make it illegal to publish publically funded research behind a paywall, but I digress.
The message here seems to be that there were really two geologic events on the subduction zone of Japan's northern coast in March 2011. The first was an an ordinary subduction quake at modest depth in the plane of the Benioff Zone, a thrust event, but that was followed by a seconary event at shallower depth which involved as much as 50 meters of thrust that triggered the huge 30 m. tsamani. This latter event was triggered by the primary subduction quake in a regime that released stress in the plate by allowing for a large amount of slippage in a relatively weak medium, not storing tectonic strain by reacting to its release elsewhere.
The analogy with the San Andreas Fault in Central California is that there are incompetant rock allowing for a relatively large ammount of slippage, some of it aseismic, between segments of the fault that are stuck because of very strong rocks that store strain for release in large quakes. So serpentines in central California may more easily pas strain along toward places where hard rocks like grainites are storing the stress to be released all at once, to the north and south of the central segment of the fault/
The difference is that the release of strain at one place in the subduction zone caused even greater slip in an incompetant boundary seaward of the initial tectonic release. In California we ger fault creep, but it is not enough to release all the strain, nor does it happen in one great event. Nor does muddy subduction even always result in seismic activity. The Mariannas Trench is aseismic probably because the subduction zone is greased and not storing strain enough to result in quakes, and there are mud volcanoes in that area as well, serpentine mud has been found there.
The abstract for the paper called the grease in the Japan subduction zone "Plagic Clay". All that means is that the mud comes from clay minerals that settle out of the water column. They could have been terrigenous, sediments from land ultimately, that got carried as far as they can get, or meteoric. The "Grease" in California and in the Mariannas Trench is different. It is from a slippery mineral that forms from the reaction of water with minerals very rich in Fe, Mg and less Si, like Olivine. The Pelagic mud may not be slippy enough to release all the strain like the Marianas serpentine mud, but it may need a nudge to move, and then ti might move a great deal all at once. 50 m. is a lot.