FAQ about the Tsunami @ USGS

I was able to get all the news and images I could stand from other news sources about the recent tsunami. Today, I just happened upon the USGS (U.S. Geological Survey) website after downloading a few of their public domain pictures (downloaded using bittorrent, here).

One of the pics from the USGS package

They also made a Frequently Asked Questions page available to those people who were curious about the Tsunami and the 9.0 magnitude Earthquake that triggered it. Here are a few of the items I found interesting:

Question: How much energy was released by this earthquake?

Answer: Es 20X10^17 Joules, or 475,000 kilotons (475 megatons) of TNT, or the equivalent of 23,000 Hiroshima bombs.

475 megatons of TNT...!? I think I just wet myself.

Question: What other great (M > 8) earthquakes have occurred in the region?

Answer: Since 1900 and prior to the December 26 earthquake, the largest earthquake along the subduction zone from southern Sumatra to the Andaman Islands occurred in 2000 and had a magnitude of 7.9. A magnitude 8.4 earthquake occurred in 1797, a magnitude 8.5 in 1861 and a magnitude 8.7 in 1833 . All three ruptured sections of the subduction zone to the south of the recent earthquake. Interestingly, the 1797 and 1833 quakes are believed to have ruptured roughly the same area with only 36 years separating the events. Paleoseismic evidence shows that great earthquakes or earthquake couplets occur about every 230 years (http://www.gps.caltech.edu/~sieh/publications/a10.html).

Question: What was the background seismicity in the region before the M9.0 earthquake? new 01/04/05

Answer: This table represents the number of earthquakes in the aftershock zone of the magnitude 9.0 earthquake on 12/26/04 for the ten previous years.

The numbers of earthquakes located in 2004 does NOT reflect the main shock or aftershocks from the 9.0. The region encompasses a rectangular box which extends from 2N to 14N and from 92E to 98E. These statistics were obtained from the USGS PDE earthquake catalog search page.

YEAR	Magnitude 5.5 & larger events.	Magnitude 5.0 & larger events.	Magnitude 4.5 & larger events.
1995	2	7	35
1996	2	9	36
1997	2	11	37
1998	1	8	38
1999	3	11	34
2000	5	12	44
2001	4	9	36
2002	11	25	91
2003	6	20	64
2004	4	14	67

The rest of the FAQ is located online at http://earthquake.usgs.gov/eqinthenews/2004/usslav/neic_slav_faq.html. While you're there you might be interested in their section entitled "Can It Happen Here?".

Posted by Jordan at January 13, 2005 03:09 PM | TrackBack