November 22, 2011 – The May 2012 Solar Eclipse Threatens the West Coast of the United States: Yesterdays post pictured the beginning of the May 20, 2012 Annular Solar Eclipse. Today we discuss the end.
The eclipse line runs directly through the “Mendocino Fracture Zone,” which is an offshoot of the San Andreas Fault. North of the eclipse line is a complex series of fault lines, the most dangerous being the Subduction Zone that runs parallel to the northwest coast of the U.S. from Oregon to just above Vancouver, British Colombia, Canada. This Subduction Zone offsets several spreading ridges, producing zigzag plate margins. The Juan de Fuca Ridge is the major spreading ridge west of the Subduction Zone.
Subduction is the process by which one tectonic plate dives under another and generates some of the largest and most dangerous earthquakes and volcanoes. For example, the Sumatra mega-quake of December 26, 2004 and the Japan quake of March 11, 2011 were both subduction zone events.
The San Andreas Fault zone, which is about 800 miles long, slices through two thirds of the length of California. It is called a Transform Fault boundary, or strike/slip boundary, because the Pacific Plate to the West is slipping past the North American Plate to the east. Generally, a transform plate boundary produces less large earthquakes than a Subduction Zone fault.
The other important item is the May 20, 2012 Solar Eclipse type. It is an Annular eclipse, which means that the Moon’s disk will not completely cover the Sun’s disk. How much is shown by the magnitude of 0.94. If the Moon covered the Sun completely, magnitude would be equal one or greater.
Further, we must consider the “Gamma” reading of the eclipse. The Gamma for this eclipse is 0.48. Without getting to technical, a positive number indicates north while a negative number equals south. The closer Gama is to zero, the stronger the effect on the earth and the higher the probability of a large earthquake.
Last we have duration. The May 2012 eclipse has a duration of 5.77 minutes. The longer the duration, the higher the probability of an earthquake. For Total Eclipses, the duration can never last longer than 7 minutes and 31 seconds. The last Total Solar Eclipse near this length was on June 30, 1973 (7 Min. 3 Sec.). On July 1, 1973 a 6.7 magnitude quake occurred. Three quakes (6.0M, 6.5M and 6.4M occurred on July 3rd and one on July 5th (6.4M). Notice that the biggest quake occurred directly after the Solar Eclipse. However, the relationship between eclipses and earthquakes is a complex one, and other factors set them off (more on this in later posts).
To summarize, strong earthquakes are generated when Solar Eclipses have magnitudes equal to or greater than one, Gama is close to zero and the duration is long.
The worrisome thing about this eclipse is that it occurs in two areas that are prone to large earthquake, i.e., near Japan and at the juncture of a complex fault system on the west coast of the United States.
The worst case scenario is that both the San Andreas and northwest coast subduction zone release simultaneously, creating a meg-quake of unprecedented proportions!
The Master of Disaster