1 4 Posted September 2, 2005 Share Posted September 2, 2005 Just on the news now about a town in Nagano (Maruko-machi?) that has a new system that apparently lets people know that there's been an earthquake before the shaking starts - they were saying 10 seconds. The alarm goes off in the town over speakers so people can prepare for the shaking. I didn't get much more than that... anyone else? Link to post Share on other sites
Ocean11 0 Posted September 2, 2005 Share Posted September 2, 2005 Apparently it also goes off a lot when there's going to be no earthquake, so it gets ignored, even when there is actually going to be an earthquake. Link to post Share on other sites
sanjo 2 Posted September 2, 2005 Share Posted September 2, 2005 You know more abou that Ocean11 - how is that supposed to work? Link to post Share on other sites
Ocean11 0 Posted September 2, 2005 Share Posted September 2, 2005 I have no idea. I only know the little bit that was on TV last night and that my missus told me. If it was actually reliable, 10 seconds would be long enough to make a big difference though. NHK had a big special on last night about the 3 earthquake zones on the Pacific seaboard that are due to go off sometime soon. Scary stuff. Link to post Share on other sites
sanjo 2 Posted September 2, 2005 Share Posted September 2, 2005 Another special on tv? I didn't know about that one - they seem to have one of those every month these days. Any new info they cared to part with? I presume it being NHK it was a little better than the usual tarento shoutfests that you have on the other channels........ Link to post Share on other sites
scouser 4 Posted September 2, 2005 Share Posted September 2, 2005 Damn, I missed that one. Funny how a small town (never heard of it?) in Nagano is doing that... Link to post Share on other sites
tsondaboy 0 Posted September 2, 2005 Share Posted September 2, 2005 Quote: Originally posted by sanjo: You know more abou that Ocean11 - how is that supposed to work? Although I didn’t watch the specific broadcast so I cant tell for sure how the system they have installed works, I can tell you how similar systems work. Seismic waves in the upper crust “usually” travel with a speed of 3 km/sec. Consider now the case that an earthquake occurs something like 90 Km away from a city. This means that the seismic waves need approximately 30 sec to travel from the source to the city. Now, if you install around the city seismographs at a radius of 30 km from the centre of the city, it will take something like 10 sec for the seismic waves to reach the city after they have been detected by one of the seismographs. Once they have been detected, a radio signal (travels with the speed of light) leaves the seismograph and triggers the alarm in the city. Obvious problems with this system. a) if the seismic source is under the city, the waves will reach first the city and then the seismometers on the perimeter. A big truck passing near one of the seismometers can easily trigger the alarm. There are many other parameters that control the propagation of seismic waves that will cause this system to fail. It’s not easy to explain all of them so I just give you the main principals. Link to post Share on other sites
Ocean11 0 Posted September 2, 2005 Share Posted September 2, 2005 So, how does the movement of Saturn fit into that scenario then tsondaboy...? Link to post Share on other sites
soubriquet 0 Posted September 2, 2005 Share Posted September 2, 2005 It's moving into Uranus Link to post Share on other sites
tsondaboy 0 Posted September 2, 2005 Share Posted September 2, 2005 Obvious problems with this system. a) if the seismic source is under the city, the waves will reach first the city and then the seismometers on the perimeter. A big truck passing near one of the seismometers can easily trigger the alarm. c) Saturn farts and trigers the sirens Link to post Share on other sites
muikabochi 208 Posted September 3, 2005 Share Posted September 3, 2005 Not sure I'd want one of that going off scaring the shit out of me whenever a big truck comes round. Link to post Share on other sites
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