Ocean11 0 Posted February 3, 2006 Share Posted February 3, 2006 Quote: Originally posted by soubriquet: only mechanism I can see for "amplification" is if the P waves are reflecting back and forth off the margins of the basin, and you are getting constructive and destructive interference. On the last big TV 'special' I watched, they had an animation of something that sounds very similar to what you describe. Definitely a lot of bouncing off the edges. Link to post Share on other sites
tsondaboy 0 Posted February 3, 2006 Share Posted February 3, 2006 Quote: Originally posted by soubriquet: While everyone's paying attention, I have a question for tsondaboy. Clearly in a basin of saturated sediment, the intensity and duration of the event is much greater. I have seen this referred to as "amplification". Is this genuinely the case? The only mechanism I can see for "amplification" is if the P waves are reflecting back and forth off the margins of the basin, and you are getting constructive and destructive interference. Anyone? Not necessarily, it is highly depended on the frequency of the wave and the elastic constants of the formations. For frequency lower than 0.4 sec the amplification of a wave pashing through a rock formation is higher than that of passing through a sedimentary formation. Generally speaking though, rock formations have higher shear rigidity strength than sedimentary formation, which results in the amplification of the wave when passing through a rock layer to a sedimentary layer. Multiple reflection between some layers has nothing to do with the above mentioned process. Link to post Share on other sites
lin 0 Posted February 5, 2006 Share Posted February 5, 2006 Interesting. tsondaboy, do you study these things? Link to post Share on other sites
soubriquet 0 Posted February 5, 2006 Share Posted February 5, 2006 Thanks tsondaboy. Some time googling turned up some stuff. From here: http://earthquake.usgs.gov/regional/pacnw/ships/pdfs/SnelsonBSSA2005.pdf "Amplification of strong ground motions around the edges of basins has been interpreted as resulting from interference patterns along crustal fault zones and thinning basins (Kawase, 1996; Graves et al., 1998). Finally, surface waves generated within these basins are thought to be responsible for much of the increased amplitude and duration of shaking during earthquakes (Frankel et al., 1999, 2002; Pratt et al., 2003a; Barberopoulou et al., 2004)" And from here: http://peer.berkeley.edu/year7/yr7_projects/ta4/2212003.html "..show results of vertical wave propagation in soft and stiff soils. The plotted lines are the time histories of displacements from the depth of 30 meters to the surface. The seismic amplification in soft soil (clay) is apparent!" It sheds some light on last year's Niigata shinkansen derailment. It was in a tunnel at the time of the earthquake, and the emergency stop system failed to detect the earthquake, although the surface ground motion was strong enough to damage the elevated section outside the tunnel. Link to post Share on other sites
brit-gob 9 Posted February 6, 2006 Share Posted February 6, 2006 All very interesting stuff. Just don't want to experience it. Link to post Share on other sites
lin 0 Posted February 9, 2006 Share Posted February 9, 2006 Do I remember correctly you are in Yamagata soubriquet? Link to post Share on other sites
soubriquet 0 Posted February 9, 2006 Share Posted February 9, 2006 Yes lin, Oishida is about 30km north of Yamagata city. Link to post Share on other sites
sanjo 2 Posted February 14, 2006 Share Posted February 14, 2006 Where's rahul? I need to know the next prediction. Link to post Share on other sites
bushpig 0 Posted February 14, 2006 Share Posted February 14, 2006 didn't he say he wouldn't be back for quite a while but would only check in very occasionally? Link to post Share on other sites
IIIII 2 Posted February 15, 2006 Share Posted February 15, 2006 It's a little unsafe and a worrying time for us all though, isn't it? Link to post Share on other sites
zebedee 1 Posted March 20, 2006 Share Posted March 20, 2006 It has been rather quiet on the earthquake front of late hasn't it..... is that a bad thing? Link to post Share on other sites
joshnii 2 Posted March 20, 2006 Author Share Posted March 20, 2006 Not having them is definitely a good thing!!!! (But then again isn't it right that it's not good to have it totally quiet, pressure building?) Link to post Share on other sites
muikabochi 208 Posted March 21, 2006 Share Posted March 21, 2006 Yes we can do without those things.... Link to post Share on other sites
TheOrange 0 Posted March 27, 2006 Share Posted March 27, 2006 Bit of a tremblor there, looks like between Shikoku and Kyushu http://www.jma.go.jp/jp/quake/5/27120300391.html Link to post Share on other sites
snowboard 0 Posted March 27, 2006 Share Posted March 27, 2006 I'm in Kyushu at the moment. .. sure felt that one. Link to post Share on other sites
sanjo 2 Posted April 3, 2006 Share Posted April 3, 2006 Just saw this on tv this morning.... There's some 2 hour drama on tv tonight, 9:30 I think. Story is about a shindo 7 quake hitting Tokyo. It's called Aasu-kuweiku. (I don't think it has anything to do with bottoms). Link to post Share on other sites
scouser 4 Posted April 3, 2006 Share Posted April 3, 2006 I'll try and watch that. I'm sure there'll be tons of great acting on show. Link to post Share on other sites
muikabochi 208 Posted April 3, 2006 Share Posted April 3, 2006 I might even watch that myself, think I've mentally recovered enough to be able to watch it. Link to post Share on other sites
taguchi 0 Posted April 4, 2006 Share Posted April 4, 2006 Did you watch it? I was plan to but only got back from work at 11 last night (it's not normal!) and so did not see it. Link to post Share on other sites
yoroshiku onegai shimasu 2 Posted April 5, 2006 Share Posted April 5, 2006 I watched it. Fairly predictable stuff. Actually I fell asleep and missed the last 20 minutes or so - how did it end? Link to post Share on other sites
sv3nni 0 Posted April 8, 2006 Share Posted April 8, 2006 Did anyone notice this ? http://www.stop-hamaoka.com/english/english.html http://www.stop-hamaoka.com/english/020606Interview.html everybody from Hamaoka to Tokyo can flip a coin to check if we're still there in 2010 ... hope we're lucky Its about the Tokai quake Link to post Share on other sites
scouser 4 Posted April 8, 2006 Share Posted April 8, 2006 First I had heard of "Mercalli Scale", will have to look that up. But I'll save that for a work day I think Link to post Share on other sites
IIIII 2 Posted April 8, 2006 Share Posted April 8, 2006 This article is worth reading http://japanfocus.org/article.asp?id=460 Link to post Share on other sites
fukdane 2 Posted April 10, 2006 Share Posted April 10, 2006 Just had a bit of a big shake here before. Link to post Share on other sites
joshnii 2 Posted April 10, 2006 Author Share Posted April 10, 2006 There seems to be a lot of quakes over that area recently (is there always?) http://www.jma.go.jp/jp/quake/10093100391.html Link to post Share on other sites
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