Scary! (Quake)

[tsondaboy 0]

Which Univershity? I have graduated from the Geology school in Greece and now I am doing my phd in Seismology.

[soubriquet 0]

Far out. BSc in Environmental Sciences from U East Anglia, and PhD in Sedimentary Geology from Reading.

 

Enjoy the PhD. It's your's and your's alone, but alone can be tough.

[tsondaboy 0]

It is a bit tough but it is definetly fun. Good thing the typhoon just passed us, because I am heading towards the mountains tomorow.

So, what are you doing in Japan, something that has to do with Geology perhaps?

[soubriquet 0]

Fred Vine taught me geophysics. He was the guy who worked out the link between geomagnetic reversals and sea floor spreading, the final link in plate tectonic theory. Top bloke and a brilliant lecturer.

[tsondaboy 0]

Cool mate!He mast be a really sharp guy, how old is he?

[soubriquet 0]

My ex-wife is a vindictive bitch from hell who destroyed my family, my home and my career, then took me to the cleaners via the Child Support Agency and the Family Court. I am here because I met someone kind. I have a new and better life, but I miss my children as much as they miss me. Having failed to control me with every legal means, she punishes by witholding my kids. Sorry.

[soubriquet 0]

Fred retired about 10 years ago, so he's mid seventies. His lectures were models of crystal clarity. Ace intellect.

[tsondaboy 0]

I see, you had quite some rough time back then. Good thing you didn’t give up and find a way to look forward in your life. I wish you good luck with your kids, I guess if you are close to them, they will grow to respect you for how you are. Just don’t give up and don’t try to put them between you and your ex.

[soubriquet 0]

Taught No1 son to ski. Last winter I chucked his skis in the boot after I put mine on the roof. Complaint: I want my skis to ride with yours, dad. No worries tsondaboy, my sons know who their father is.

[big-will 7]

Got shaken up a bit again today (well, yesterday)... anyone else? Saitama this time it seems

[sunrise 0]

Really? I must have missed it.

 

Sorry to hear about that soubriquet. It can be really tough for the dad in divorces. I hope things soften over time so you can see you kids again before too long.

 

Off to check the EQ map....

[sunrise 0]

Ah - so that's why the train stopped for a while tonite.....

[Sven 0]

To come in a little late: yep, that quake was scary alright. It may just be cos it was the first I'd experienced in my apartment, but that thing was shaking a full 2 minutes after the initial shock...

 

An interesting little aside is that after any earthquake one of the boss dudes at work (who I had thought was completely humourless) always yells something (too quick for me to understand) to the heaviest guy in our office... looks like there's humour in the man after all

[Ocean11 0]

Question: Is all this shaking a good sign that the stress is being released without doing hideous damage (obviously Niigata is not included in that latter bit) ... or is it a prelude to something that does hideous damage?

[soubriquet 0]

Very generally, numerous small earthquakes will reduce the strain over a given area, so I would say the former. Not all earthquakes are the same, however. The amount of energy that can be stored, and released is a function of the surface area and geometry of the fault(s), and there can be different faults behaving differently within the same area. So I'll give the infuriating response, probably, with qualifications.

 

A lot of very clever people have put a lot of energy into studying these problems, and they really are intractable. I'll post something on faults later, got work to do now.

[taguchi 0]

I hope you are right.

 

soubriquet - how do you think about "earthquake cloud" and other concept like that?

[soubriquet 0]

I had a quick check through my stuff, and I have plenty on faults. I can do that from memory, but not much relevant to Earthquakes. I can put up some stuff on plate tectonics too, if anyone is interested, but this is generic geology. Tsondaboy is (should be) the real expert, with respect to Japan. The problem for Kanto and through to Kanazawa is that there are three plates in collision, which causes some very complex motion.

 

There's a good site here which gives current and historic information:

http://neic.usgs.gov/neis/current/japan.html

 

Taguchi. I don't believe in "earthquake clouds". If the link between the subsurface and the atmosphere were strong enough to form clouds, then it could be easily measured.

 

There has been a lot of work done on earthquake prediction. I'll paraphrase from a 1972 textbook "..premonitory phenomena fall into three categories: strains and tilts, variation in background seismicity, and changes in rock physical properties...". Not much has changed in 30 years. The problem is that these phenomena may or may not be predictive, and Ishihara isn't going to evacuate Tokyo because someone's catfish start jumping. Also, while I'll buy that strain will cause localised changes in magnetic susceptibility and electric resistivity, this is really only detectable for shallow faults. The big one is going to come from several 10's of km deep.

[tsondaboy 0]

 Quote:

Originally posted by soubriquet:
Tsondaboy is (should be) the real expert, with respect to Japan.

Thanks for your nice comments soubriquet, I appreciate them.
I am not yet an expert in seismology, but I am working hard to improve myself.

As far as for earthquake predictions, I leave this job to astrologers, I consider myself a scientist. I am not posting much staff about earthquakes because my experience says that the average people are not interested in general-seismology. The only thing that everyone wants to know (including my self), is something that I am not able to answer yet. I hope that sometime in the future, me or some other colleague makes a leap forward into that field. But for the time being the only thing I recommend is patience.

[sanjo 2]

I'm interested in what you guys have to say.... do keep on posting about quakes!

[soubriquet 0]

Due to underwhelming public response.

 

These are the three basic (end member) types of fault.

 

Normal

 

Strike slip

 

Thrust

 

For normal faulting, the crust is in tension (E-W in the diagram). The relatively small surface area limits the amount of strain (stored energy, like bending a spring), and because it is being pulled apart, the fault tends to move easily. You would expect numerous small local earthquakes from this style.

 

Strike slip faulting is shear. The best known example of this is the San Andreas fault. Similar to the normal fault, the fault angle is high and surface area is small. These can store more energy than normal faults, but it is limited because the compressive force is parallel with the fault, and they move relatively easily.

 

Thrust faults are low angle, have a high surface area (energy storage potential), and they tend to lock because the forces are trying to close the fault.

 

 

This is a simple cross section across a volcanic arc similar to Japan. Kanto plain is part of the forearc basin, inland Yamagata (for example) is an intra-arc basin, and the backarc basin is the Japan sea side. In the forearc basin, everything is in compression, as we would expect. The intra- and back arc basins are in tension, which is counter intuitive for a convergent plate margin.

 

A more detailed cross section of a forearc basin. I like this one because their is no vertical exaggeration. Kanto plain is basically the forearc basin fill, where the subducting slab changes to a steeper angle of descent. As the energy released by an earthquake decays at the inverse square of distance, this is good for central and west Japan, not so good for Tokyo.

 

This is a simplified picture of the basic geometry. It is complicated by the interaction of the Philippines and Pacific plates, as well as numerous local variations in structural style.

[Mr Christopher 0]

I'm very interested.

[HeatherLocklearRocks 1]

I was in Chiba on the 6th floor of a fairly old building and it was well scary. Like I've heard others say, didn't really know what to do basically stood to the spot.

[1 4]

Anyone else get woken up by that. Can't get to sleep now.

[bong 0]

Yes I did.

 

Being a bit drunk helped.

[powwwers 0]

hey bro. bong, how were ya a `bit` drunk is that like gettin a girl a `bit` preggo? "i rooted this chic the otha night, and i forgot ta wear a dinga. but it`s okay, i only got her a `bit` preggo."

 

just wondering. lol