Wednesday, March 16, 2011

Earthquakes & Tsunamis - Is the Pacific Ocean to Blame?

For years scientists have pondered the possible connection between spikes in the El Nino-Southern Oscillation [ENSO] and Pacific sea bed seismicity.  We're just about at the end of what has been a massive La Nina event.  Has this had some bearing on the devastating earthquakes that hit New Zealand and Japan?

Britain's prestigious Royal Society believes the link is statistically made out.

We observe a significant (95% confidence level) positive influence of SOI [Southern Oscillation Index] on seismicity: positive SOI values trigger more earthquakes over the following 2 to 6 months than negative SOI values.  
There is a significant negative influence of absolute sea levels on seismicity (at 6 months lag). We propose that increased seismicity is associated with ENSO-driven sea-surface gradients (rising from east to west) in the equatorial Pacific, leading to a reduction in ocean-bottom pressure over the EPR [East Pacific Rise] by a few kilopascal. This relationship is opposite to reservoir-triggered seismicity and suggests that EPR fault activity may be triggered by plate flexure associated with the reduced pressure.

The Royal Society has a collection of fascinating research papers exploring links between climate change and other events including gas hydrates, volcanology, geospheric and geomorphological responses and more.  You can find links and abstracts here.

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