Great
Earthquakes In Diverse Places
2011 On Target For Highest Number Of Ever Recorded
Earthquakes
By Mark Dunphy - Mon Jun 20, 12:10 am
Irish TImes
2011 is on target to record the largest number of earthquakes in a
single year for at least 12 years.
Research by Irish Weather Online, using data from the US
Geological Survey (USGS), has found that earthquake activity
(5.0-9.9 magnitude) from 01 January to 19 June 2011 is already
exceeding the total annual seismic activity for the years 2001,
2002 and 2003. 2011’s total number of recorded earthquakes is
also expected to exceed the most seismically active year of the
past 12 years, 2007.
A total of 1,445 earthquakes, ranging in magnitude from 5.0 to
9.9, have been recorded in the year up to 19 June. The total
number of earthquakes recorded globally for the entire of 2007 was
2,270.
The massive earthquakes in Japan (2011), Chile (2010), Sichuan
(2008), Sumatra (2005 and 2008) and Indonesia (2004) have served
to remind us of the devastating impact of earthquakes on life and
property. While the number of earthquakes ranging between 8.0
magnitude and 9.9 magnitude have shown no significant increases in
recent years, the number of earthquakes ranging 5.0 magntiude to
7.9 magnitude is rising. In particular there has been a sharp rise
during the past 12 years of moderate earthquakes in the range
5-6.9.
While considered moderate to strong on the Richter Scale and far
less severe than 7+ magnitude quakes, earthquakes in this range
can still cause widespread damage and loss of life. Some well
known examples include Haiti in 2010 (7 mag), San Francisco Bay,
California, USA, in 1989 (6.9 mag), Caracas, Venezuela, in 1965
(6.5 mag), Christchurch, New Zealand, in 2011 (6.3 mag), L’Aquila,
Italy in 2009 (5.8 mag), and Newcastle , Australia, in 1989 (5.6
mag).
In the last 24 hours alone earthquakes ranging 5 magnitude or more
have hit Tonga, Fiji, Panama, the South Sandwich Islands, Japan,
Papua New Guinea, Peru and Indonesia.
Seismologists argue that an increase in detected earthquakes does
not necessarily represent an increase in actual earthquakes. The
USGS, for example, says improved global communication and
enhancements in detection technology have both contributed to
higher earthquake numbers being recorded over time.
According to the USGS: “Although it may seem that we are having
more earthquakes, earthquakes of magnitude 7.0 or greater have
remained fairly constant throughout this century and, according to
our records, have actually seemed to decrease in recent years.”
Commenting on swarm earth activity in a specific geographical
area, the USGS said :” A temporal increase in earthquake activity
does not mean that a large earthquake is about to happen.
Similarly, quiescence, or the lack of seismicity, does not mean a
large earthquake is going to happen. A temporary increase or
decrease in the seismicity rate is usually just part of the
natural variation in the seismicity. There is no way for us to
know whether or not this time it will lead to a larger earthquake.
Swarms of small events, especially in geothermal areas, are
common, and moderate-large magnitude earthquakes will typically
have an aftershock sequence that follows. All that is normal and
expected earthquake activity.”