Animation of Japan foreshocks-main shock-aftershocks

This animation from YouTube showns the main shock at 1:16, with both preceding foreshocks and succeeding aftershocks. Because the energy release increases by a factor of 27.5 with each step in magnitude, most of the energy is released by the main shock.

Beware if you are in the library: music is included.



 You can get a sense of all that activity by looking at the lists at the USGS/NEIC website.

Japan quake was magnitude 8.9, is now 9.0

"The USGS has updated the magnitude of the March 11, 2011, Tohoku earthquake in northern Honshu, Japan, to 9.0 from the previous estimate of 8.9. Independently, Japanese seismologists have also updated their estimate of the earthquake’s magnitude to 9.0. This magnitude places the earthquake as the fourth largest in the world since 1900 and the largest in Japan since modern instrumental recordings began 130 years ago.

"The USGS often updates an earthquake’s magnitude following the event. Updates occur as more data become available and more time-intensive analysis is performed. There are many methods of calculating the energy release and magnitude of an earthquake. Some methods give approximate values within minutes of the earthquake, and others require more complete data sets and extensive analysis. Due to inherent uncertainties in the modeling of energy and magnitude, the results from different agencies often vary slightly. These magnitude discrepancies arise from the use of different data and techniques. For more information on why magnitudes change, see the Earthquake Hazards Program FAQ website."

Largest earthquakes in history

By magnitude (Japan quake comes in as #4)

Event	Date/time	Lat	Long	Mag	Fatalities	Region
1.	1960-05-22 19:11	-38.29	-73.05	9.5	1,655	Chile
2.	1964-03-28 03:36	61.02	-147.65	9.2	125	Prince William Sound, Alaska
3.	2004-12-26 00:58	3.295	95.982	9.1	227,898	off the west coast of northern Sumatra
4.	2011-03-11 05:46:23	38.322	142.369	9.0		Near the East Coast of Honshu, Japan
5.	1952-11-04 16:58	52.76	160.06	9.0		Kamchatka, Russia
6.	2010-02-27 06:34:14	-35.846	-72.719	8.8		Offshore Maule, Chile
7.	1906-01-31 15:36	1.0	-81.5	8.8	1,000	Colombia-Ecuador
8.	1965-02-04 05:01	51.21	-178.50	8.7		Rat Islands, Alaska
9.	2005-03-28 16:09	2.074	97.013	8.6	1,313	Northern Sumatra, Indonesia

By casualties (Japan will not make this somewhat subjective list):

Rank	Death toll	Event	Location	Year
1.	&0000000000830000000000830,000	1556 Shaanxi earthquake	China	01556-01-21556
2.	&0000000000242419000000242,419–779,000	1976 Tangshan earthquake	China	01976-07-281976
3.	&0000000000316000000000316,000+	2010 Haiti earthquake	Haiti	02010-01-122010
4.	&0000000000250000000000250,000	526 Antioch earthquake	Antioch, Byzantine Empire (now Turkey)	00526-526
5.	&0000000000235502000000235,502	1920 Haiyuan earthquake	China	01920-12-11920
6.	&0000000000230210000000230,210	2004 Indonesian earthquake	Indonesia	02004-12-262004
7.	&0000000000230000000000230,000	1138 Aleppo earthquake	Syria	01138-1138
8.	&0000000000200000000000200,000	856 Damghan earthquake	Iran	00856-12-2          856
9.	&0000000000150000000000150,000	893 Ardabil earthquake	Iran	00893-03-2893
10.	&0000000000142000000000142,000	1923 Great Kanto earthquake	Japan	01923-09-1923
11.	&0000000000137000000000137,000	1730 Hokkaido earthquake	Japan	0171730
12.	&0000000000123000000000123,000	1908 Messina earthquake	Italy	01908-12-21908
13.	&0000000000110000000000110,000	1948 Ashgabat earthquake	Turkmen SSR, Soviet Union (now Turkmenistan)	01948-10-01948
14.	&0000000000100000000000100,000	1290 Chihli earthquake	China	01290-09-21290
15.	&0000000000100000000000100,000	1755 Lisbon earthquake	Portugal	01755-11-011755
16.	&0000000000100000000000100,000	1667 Shamakhi earthquake	Azerbaijan	01667-11 1667

Or see the USGS list.

Japan quake, some of the early news

Here were some of the early news stories that impressed my geophysics students Peter Rippberger, Hannah Rosenberg, and Matt Slowinksi:

http://www.bbc.co.uk/news/world-middle-east-12307698
Up to date coverage of the diasster in Japan from BBC news report.

http://www.npr.org/?refresh=true
One of the worst effects of earthquakes are the tsunamis caused by the quake, check out the link to learn more.

http://www.affordablecebu.com/load/news/japan_earthquake_and_tsunami_pictures_march_11_2011/37-1-0-663
Look at the link to see pictures from the devastating event.

http://www.youtube.com/watch?v=DePXcKeaHZ4&amp
Look at this live footage of how quickly the flood spreads.

http://www.youtube.com/watch?v=j3fUqdGXLbM&playnext=1&list=PL0870831CE43351E1
Here is a video from one of the residents of Japan while the Earthquake was occuring.

Japan earthquake - seismograms

My geophysics students Eamon Hall, Conor Neal, and Stacey Sosenko tracked down this seismogram from the Australian seismograph network:

Seismograms from the western Australia network of seismograms shows the initial pulse a little more than 10 minutes after the main quake, as shown in the figure below.

 

The Franklin & Marshall seismograph is located about 93 degrees away from the focus and felt the quake about 13 minutes after it struck, as expected.  The seismogram also shows up two  aftershocks later in the day.

Or, check out some more seismograms using the Rapid Earthquake Viewer.

Japan 8.9 quake - the source

On Friday, the morning after the devastating earthquake in Japan, I had my geophysics students compile some information about the quake.

Elvis Andino, Stephanie Douglas, and Andrew Tsang looked at the source parameter. They found:

The epicenter occurred at 38.322°N, 142.369°E on the Japan Trench subduction zone, where the Pacific plate is subducting beneath the Eurasian plate.  The epicenter was 373 km NE of Tokyo. The earthquake focus was about 24 km below the sea floor.

As shown below in the fault plane solution, the earthquake exhibited thrust faulting, consistent with its location along a subduction zone. The NE-SW strike of the fault plane is parallel with the orientation of the plate boundary shown above.

It had a magnitude of 8.9, putting it 5th on the USGS's list of largest earthquakes since 1900, right before the 2010 Chile earthquake,

Large foreshocks preceded the main shock over the previous two days, including a M7.2 quake about 40 km from the epicenter of the big earthquake.

Because Japan is partially surrounded by fault zones, it has had many earthquakes in its history. These have mostly been shallow quakes. The last major earthquake on the same fault was in 2005, a M7.0

Arkansas 4.7 quake, 2/28/11

A magnitude 4.7 earthquake happened in Arkansas on Feb. 28.  It's interesting that the Arkansas Geological Survey has some decent web pages on earthquakes in the New Madrid Seismic Zone, but I couldn't find anything yet on this particular event.

According to the USGS:

This figure [below] shows the distribution of earthquakes in north-central Arkansas that have occurred since June 2010. Earthquakes on the figure are color-coded, with red circles denoting earthquakes that occurred from June 4th, 2010 to February 14, 2011, and orange circles denoting earthquakes that occurred from February 15, 2011 to March 1, 2011. The space-time pattern shows a systematic shift in seismicity to the southwest starting on February 15, 2011. White triangles show the location of real-time seismic stations in the vicinity of the earthquake swarm that are used by the University of Memphis and USGS in their complimentary monitoring activities.

More in following posts.