Monday, March 14, 2011

Japan Earthquake and Tsunami

Yet another natural disaster which is captivating the world.  The earthquake in Japan which measured a magnitude 9.0 (revised) was the strongest in history for Japan.

 The Japanese emergency warning system gave a 30 second warning.

Since the 9.0 on Friday, Japan has experienced more than 300 separate "aftershocks".  See the location of the quakes from Friday morning until early Sunday evening.

To put that into perspective, most of these aftershocks have been stronger than the quake that rattled NE Ohio and surrounding areas back on January 31, 1986.

Northern Ohio has areas that are susceptible to earthquakes

From the Ohio Seismic Network:  "Back then, destruction in the epicentral area was mostly minor. Merchandise fell from store shelves in Mentor, Painesville, and Chardon and buildings in these communities experienced varying degrees of cracked plaster and cracked or broken windows. Chimneys are particularly susceptible to damage or destruction from ground motion associated with moderate to strong earthquakes. There was, however, only one confirmed report of a chimney being toppled."

Earthquakes are measured with the Richter Scale. The Richter is "logarithmic" meaning that the increase goes up fast as the scale goes up.  So a magnitude 6.0 is 10 times as powerful at a 5.0.  A 7.0 is 100 times as powerful than a 5.0 and so on.  To put this into perspective, the quake that hit Japan was more than 10,000 TIMES MORE POWERFUL than the quake over Northeast Ohio back in '86!

So why all of these quakes?  Is anything different going on recently?  To better get an understanding on earthquakes, lets look at the area we call "The Pacific Ring of Fire".

The Ring of Fire is a battlezone between several "plates" that make up our continents. Keep in mind that the area of the earth where the continents plates reside is the top 25 miles or so.  These plates "float" on the hotter, more liquified inner portion of the earth.

Each one of these plate "rubs", subducts (or dives under) the neighboring plate.  When the friction between each plate gets to great, it causes an earthquake. Below is a cross-section of the Juan De Fuca Plate and the North American Plate which is responsible for the west coast earthquake activity.

 Where these plate converge, volcanoes also form as the plate push up the crust.
 Over millions of years, volcanoes formed along the Ring of Fire.

The earthquake activity from late Friday until late Sunday evening along the ring of fire.  This accounts for more than 90% of the global quakes.

If earthquakes occur under the ocean floor along one of the faultlines as the plates push up on the ocean, it can cause a ripple effect as it displaces the water above.

Since the tsunami (or seismic sea wave) occurs so far under water, the wavelength of the tsunami is very long.  In most instance, it can measure more than 200 miles from crest to trough.  This is why if your in a boat in the middle of the ocea, you won't much of a change. As the wave get closer to land, the wavelength gets shorter, the water gets higher.

These seismic sea waves can travel across the entire Pacific Ocean at speeds of more than 200 miles per hour. 

The National Oceanic and Atmospheric Administration released a projected wave heights map for the Pacific Ocean. The area that is effected is enormous!            

The impact of the tsunami was fast. The travel times are below.

More updates as the nuclear reactor may meltdown.....

1 comment:

Cheryll R said...

Do you suppose that the quake and tsunami were geologically related to the eruption at Kilauea earlier in the week? I read somewhere that everyone in the Pacific was sort of on 'alert' for something to happen. Of course... you can't really bring life to a screeching halt and close all the power plants, train tracks, and roads in anticipation... it's amazing how little we can do in preparation for a great cosmic swish of the planet's cow-tail, trying to shoo us pesky flies off her rump.