Thursday, April 14, 2011
Earthquake Long Cycle
Take a look at this chart. What we have is a clear thirty year rise in earthquake activity starting around 1960 and then dropping of for a decade. The last decade it has returned to the secular uptrend and has now made up for any lost ground. Thus we have a clear fifty years of stable activity counts with no apparent trend, followed by fifty years of double the activity and a secular uptrend.
This may well be the result of changing data collection capability, although I find that to be a bit of a stretch. The seismograph sees through the earth and the first handful did the trick quite well. I think we can now accept a higher level of seismic activity that continues to be sustained and equally unexplained. Most certainly it shows little correlation to sunspot activity or other non earth source.
It is better to bite the bullet and accept that this is a natural earth cycle and we need to understand it. The apparent length of the cycle itself is pretty easy to understand as it can be mapped against a model based on the ring of fire in which certain significant events over time translate into further events along the boundary.
Thus a cycle in activity, which may be century’s long or even millennia long, is implied by the very existence of the ring itself which is slowly shrinking around the Pacific Plate. That there should be internal cycles could simply reflect the random selection of triggers that allow a spat of them to take place and may actually be a residual echo of a major event many millennia ago.
I bring that up because the Pleistocene nonconformity is exactly one such event that would still drive such a wave of seismicity even today.
In fact knowledge of such long cycle seismicity may even be the underlying argument for certain ancient predictions that crop up in arguments for 2012 and the like.
Right now the take home is that such a cycle appears to exist and begs consideration and watching. Do not forget that the San Andreas is way overdue.