To get 10 seconds warning you'd have to be more that 90 kM from the epicenter. The S-Wave propagates at about 9 kM/Sec.
I absolutely agree... a derailment at 50 would be a lot less destructive than a derailment at 100... but I do know that only maybe 10 seconds could not be enough to come to a complete stop, but if yu could hook a detection system up to an emergency brake, it would make a very large difference, IMO
True, but on a bullet train, seconds can mean a substantial difference in the speed you're going when the quake hits. You can't get to a complete stop, but I think cutting that speed back even by a small amount counts for something.
The success of the Japanese lines in earthquakes due to one main factor: The nature of the Japanese concrete slab support under the rails allowed the derailed train in the one earthquake caused derailment to simply slide to a stop along the concrete. Some cars were tilted, but there was no overturning. Everybody literally walked off.
The value of earthquake detection systems is highly overrated. The warning time is measures in seconds, if that. Earthquake are not predicitble to any meaningful level of certainty with current technology.
This is exactly my point. 10 seconds does not give you any meaningful reduction in speed. for the two earthquake derailments that we have had (oen in Japan and one in Taiwan) the speeds were well above 200 km/h in both.
For some information on derailment in Japan, go to www.jreast.co.jp/e/press/20080202/index.html
The magnitude of the earthquake was 6.8 and the train was 9.8 km from the epicenter.
The derailment stages given in the article. When reading it, understand that car No. 10 was the front car of the train and car No. 1 was the last car. When looking at the pictures, the car that is seen leaned in toward the center is the last car of the train. (Japanese railways run left-handed.) The front car and most of the rest of the train remained well centered on the track, even though off the rails.
(1) 11 axles derailed due to seismic motion.
At 17:56:06, the fourth axle of car No. 10 derailed first. Subsequently, 4 derailments occurred during large lateral movements in a 4 - 5 second interval. 11 out of 40 axles derailed.
(2) Additionally, 11 axles derailed when the track was broken by derailed wheels.
After the fourth derailment, the second, third, and fourth axles of the No. 4 car fell to the track. Continued running while pushing apart the left and right rails. The eight axles of the No. 1 and No. 2 cars then also derailed. A total of 11 axles out of 40 axles derailed.
(3) Breakage of the IJ part.
The last railcar (No. 1 car) angled into the central return channel because a glued insulated joint (IJ) broke.
(4) The train was guided by the rails even after derailment and the attitude of the train was maintained until it came to a stop.
Since the train traveled along the rails with the rails pinched between the wheels and the bogie parts, the attitude of the train was properly maintained until it came to a stop.
I know I have seen the exact speed of the train somewhere, but it was not in the article and I do not have time to hunt it up right now.
Another little factoid from another discussion on this earthquake:
In the perid of 1994 to 2003, there were 960 earthquakes of magntude 6.0 or larger. 220 of these were in Japan.
Based on this, who do you think we should talk to when discussing dealing with seismic issues?