Two weeks ago the news tooted: "Strong earthquake shakes northern Japan." It had a magnitude of 6.3, and occurred at around 3:30 pm. The shaking was noticed in Tokyo, 250 km away from the epicenter. In the following, a little more information about earthquakes.
Seismic monitors measure the waves that move though and around the earth. There are two main forms of waves: body waves and surface waves. Surface waves travel like ripples on water, and body waves move through earth's inner layers.
Surface waves
Body waves
The two above have several variations, but generally the surface waves, which are easily measured by seismic devices, account for all the visible disasters. The recent earthquake, measured from the coastal station quite near the actual site, was as the picture below shows. At the 3:30 graph an eminent change can be seen. (each colored line represents a time frame of 30 minutes)
Though the epicenter was about 1,000 km (650 mi) away from Oita City, the waves were measured here as well. Below is a graph of the measurements from Oita:
The seismic waves traveled to Tokyo in 38 seconds, and by the average speed of 6.5 km/sec they reached Oita in 2,5 minutes.
On one hand experiencing an earthquake would be a cool thing but then again, it might turn out as an immense terror, which is NOT that cool! For the time being, I better not wish for one. That's it about earthquakes!
2 comments (click to write a comment):
so scary, im from ny staying in tokyo and can often feel the earth shaking. am i crazy?
Greetings to you from NY!
Though it's very unlikely, perhaps you are feeling shake made by the trains that move underground in the dense subway network of Tokyo.
That in mind, have no fear! and enjoy your time there!
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