Earthquake Trends

Earthquakes have obviously been in the new a lot recently.

I heard on the radio the other day that 2008 was on pace to be a record year for earthquakes. Always the skeptic, I did a little research. The US Geological Survery tracks "Significant Earthquakes of the World," where a "Significant Earthquake" is defined as:

Earthquakes of magnitude 6.5 or greater or ones that caused fatalities, injuries or substantial damage.

earthquake.usgs.gov...

I went through all the years on their website and trended the number of Significant Earthquakes. Here are the averages by decade:
1970s - 53/year (note, only 1977-1979)
1980s - 60/year
1990s - 79/year
2000s - 82/year (2000-2007)

So far in 2008, there have been 34, which puts us on a pace of 81 for the year, in line with the decade so far.

Worth noting high and low water marks were:
97 in 1997
42 in 1977

Two observations:
1 - It's on an obvious upward trend, although this could be partially based on their definition, which includes the term "substantial damage." The world is getting more populous, and has more infrastructure to damage now than 3 decades ago. If I have time, I plan to go back through their website and ignore any earthquakes less than a 6.5. THAT would be interesting info to have.

2 - Don't trust everything you hear in the media, who love fear-mongering (if it bleeds, it leads). This year's pace is for 81, which is exactly in line with the rest of the decade. Nothing extraordinary at all.

In recent years there have been better earthquake detectors and readers.

Also, I pretty sure there is a thread about this exact topic (Earthquake trends) that was made before.

I did roughly the same check but for all earthquakes. The total for the last three years is greater than the previous 20 years.
Each of the last three years has been progressively higher in number.

Some searching has suggested the cause.

The melting of the ice on this planet is changing the weight distribution on the crust.

I would add to that the recent nuclear tests right on the fault lines. The earth's crust has been cracked like an egg shell, and we are shifting the weight around on the surface.

If the solidified methane deposits around the edges of the ring of fire start to outgas, there could be a runaway tropicalization of the entire planet in several decades time. You might then expect earthquake and volcano activity unimagined. Add to the pressure the pressure differentials of larger and larger tropical storms. All that air pressure does add up.

My point is that there is every reason to believe that these trends can and will continue to worsen. There is no reason to believe that they will not.

I did roughly the same check but for all earthquakes. The total for the last three years is greater than the previous 20 years.
Each of the last three years has been progressively higher in number.

Do you have a source for this? I'd be curious to see some statistics. I'm not saying what you researched or stated is incorrect. I'm simply skeptical since USGS data show the last 20 years have been pretty consistent for the number of "Significant Earthquakes" with no stepward trends. The data for this is at the link I provided, or I can list the year by year numbers I pulled from the site instead of the averages if people are interested.

I just saw on the BBC news that a quake, 6.2, I think, just hit Iceland, today, 29th May.

I just came across this... it may be old news but I hadn't read it before and it is startling:

ScienceDaily (Feb. 12, 2005) — EVANSTON, Ill. --- Northwestern University seismologists have determined that the Dec. 26 Sumatra earthquake that set off a deadly tsunami throughout the Indian Ocean was three times larger than originally thought, making it the second largest earthquake ever instrumentally recorded and explaining why the tsunami was so destructive.

www.sciencedaily.com...

I came across it while reading another article on the Peru's quakes...

Between 1992 and 2007, nine magnitude 7 or larger earthquakes have rocked the subduction zone of southern Peru and northern Chile, including a magnitude 8.1 earthquake in August 2007 near Pisco, Peru.

Pritchard and Fielding combine data from seismometers and interferometric synthetic aperture radar (InSAR) to determine the Pisco earthquake's heterogeneous slip distribution.

The analysis includes some of the first data from the Japanese Advanced Land Observation Satellite (ALOS) and the European Envisat wide-swath beam. The seismic data indicate that the slip maximum occurred 60Æ seconds after the main shock started, and the InSAR data constrain the main slip patch to be about 70 kilometers (43 miles)from the earthquake's origin.

Combined, these factors suggest an extremely low rupture velocity or a long slip rise time. Historic data indicate that no large earthquake has occurred near Pisco since at least 1746.

Though the Pisco earthquake was large, its expected magnitude would have been larger if all stress accumulated since the eighteenth century had been released.

www.sciencedaily.com...

This is a revival of a thread that I wonder about especially considering the
large earthquake events that have happened in early 2010. I searched
the internet for a trend comparison and found the following link:

research.dlindquist.com...

The interesting thing is that large earthquakes (6.0+) look to be increasing
with 2010 having more than 100 events already.

Causes:
Climate change. Isostasy theory. The weight of the ice on the continents is reducing due to glacier melting. This allows an influx of magma that triggers volcanos and possibly groundwater migration into earthquake faults.

Solar cycle. It's interesting to note that during the last solar min, the number
of earthquakes was reduced. Now that we are beginning the solar max,
the number of earthquakes have increased.

Dust cloud. It's a well known fact that recently the solar system is entering
a more dusty part of the galaxy. This might be causing the heating of
the planets as observed.

motls.blogspot.com...

Magnetic field fluctuation. In case you haven't heard, earth's magnetic
field is weakening and the north pole is migrating. Scientists predict
a reversal of magnetic fields.

Now, the interesting part that I haven't been able to correlate are the
volcanic trends considering:

Iceland volcano eruption
Mount Pinatubo eruption
Alaska volcano eruptions
Multiple earthquake swarms in Yellowstone volcano