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In the U.S., earthquakes pose significant risk to 75 million
Americans in 39 states. —USGS Jan. 2004 |
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by Holly Deyo
standeyo.com
Some of you are noticing a greater uptick in recent earthquake activity and wondering if this is a real deal or just perception. It's not your imagination.
Look at the earthquakes for 2007 (lavender column). Now look at the darkest purple and darkest green columns. These show the average quake counts for any year. Why two averages? In September 2003, the USGS changed what they consider the 'annual average' - some up, some down - but for continuity, I keep and compute both averages. Either one you consult shows an elevated quake count.
Where it really becomes evident are the Richter 6 and above events. Richter 6 is the magic number where elevated quake counts can't be fobbed off onto having more seismic detection equipment in place or that they're using more sensitive seismometers. At this magnitude, their effect is too large to be missed by existing equipment. If you were talking about relatively small events like 4's and below, or even 5's, yes, this argument could hold true.
Last year saw an impressive five Richter 8 - 9.9 events. Normally there is 1. Year 2000 saw four, but even so, all other magnitudes except 7's were lower than 2007's. That 2007's mag. 7 and 6's were still near or above the yearly average speaks volumes plus 4's and 5's were really high. It seems reasonable that all magnitudes below 7's for 2007 should have fallen off significantly with the bigger quakes releasing such a tremendous amount of energy.
Whether 2007 was a fluke remains to be seen; at least it was an 'interesting' year. What happens in 2008 will be very telling, but you might ask yourself, is it time to prepare?
1 Based on observations since 1900.
Mag.
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2003
2004
2005
2006
2007
2008
"Old"
Annual
Ave.
2007
Compared
to
"Old" Ave.
"New"
Annual
Ave.
Compared
to
"New" Ave.
8.0 - 9.9
Great
0
1
2
3
1
0
2
0
4
3
1
2
1
1
5
0
1
500%
1 1
7.0 - 7.9
Major
24
15
13
22
21
20
14
23
16
15
16
14
11
11
15
2
18
83%
17 2
6.0 - 6.9
Strong
163
141
161
185
160
125
113
123
153
124
145
146
154
139
177
36
148
120%
134 2
5.0 - 5.9
Moderate
1,521
1,449
1,542
1,327
1,223
1,118
979
1,106
1,345
1,243
1,252
1,637
1,954
1,529
1956
162
800
245%
1319 2
4.0 - 4.9
Light
5,153
5,034
4,544
8,140
8,794
7,938
7,303
7,042
8,084
8,084
8,454
10,783
13,702
13,048
12,230
1007
6200
193%
13,000
Deaths
3,814
10,036
1,038
7,949
419
2,907
9,430
22,711
231
35,000-
40,000*
43,819
284,010
82,364
6,605
712
51
10,000
7%
10,000
2 Based on observations since 1990.
*HOLLY NOTES: At the end of September 2003, the USGS adjusted earthquake global averages for magnitudes 4, 5, 6 and 7. Most have increased, one magnitude decreased in shaker averages. This indicates an overall increase in earthquake activity. To get a fair comparison, both the "old" and "new" averages are included in the chart above.
The exact number of deaths from the January 26, 2001 India earthquake will never be known. According to the Red Cross, "Death toll reports vary widely, with some ranging from more 20,000 to as many as 100,000."