Mysteries remain in geological science. It seems to be accepted truth that earthquakes on a particular fault line are far more likely to trigger future quakes elsewhere on that isolated fault system than on a distant, unconnected fault line.
But both the massive Sumatra quake (9.1) of 2004 and the Chile quake (8.8) last week were said to
"ring the Earth like a bell" and there is evidence that the 2004 Sumatra "great" quake increased stresses on the San Andreas fault.
The Chile quake released 500 times more energy than the Haiti quake (7.0) which preceded it. Unfortunately, Haiti was exponentially less prepared to deal with any sizable earthquake.
http://news.nationalgeographic.com/news/2009/10/091002-earthquakes-tsunami-connected-indonesia.htmlWere Last Week's Pacific Earthquakes Connected?
Richard A. Lovett
for National Geographic News
Updated October 5, 2009
In four days last week there've been at least five substantial earthquakes—and a tsunami—in the same general region, the tectonically rambunctious Ring of Fire in the Pacific Ocean.
Coincidence? Maybe yes, but probably not, scientists say.
...earthquake vibrations may affect faults at surprisingly great distances.
In particular, the researchers found that vibrations from the 2004 Indonesian earthquake may have increased the frequency of small earthquakes in California's San Andreas Fault by causing fluids to move into the fault lines. Such an inflow would have lubricated the fault, making it more likely that the two sides would slip and slide.
Still, the study team is cautious about suggesting the same thing happened with last week's two large quakes. http://www.mcclatchydc.com/2010/03/01/89568/after-haiti-and-chile-are-earthquakes.htmlAn earthquake as powerful as the one that devastated Haiti takes place somewhere on earth about once a month, said Tim Dixon, geophysics professor at the Rosenstiel School of Marine and Atmospheric Science in Miami.http://articles.latimes.com/2009/jan/24/local/me-fault-quakes24
Study finds troubling pattern of Southern California quakes
The southern stretch of the San Andreas fault has had a major temblor about every 137 years, according to new research. The latest looks to be overdue.http://www.ussartf.org/earthquakes.htmin many places, the assumption of random occurrence with time may not be true, because when strain is released along one part of the fault system, it may actually increase on another part. Four magnitude 6.8 or larger earthquakes and many magnitude 6 - 6.5 shocks occurred in the San Francisco Bay region during the 75 years between 1836 and 1911. For the next 68 years (until 1979), no earthquakes of magnitude 6 or larger occurred in the region. Beginning with a magnitude 6.0 shock in 1979, the earthquake activity in the region increased dramatically; between 1979 and 1989, there were four magnitude 6 or greater earthquakes, including the magnitude 7.1 Loma Prieta earthquake. This clustering of earthquakes leads scientists to estimate that the probability of a magnitude 6.8 or larger earthquake occurring during the next 30 years in the San Francisco Bay region is about 67 percent (twice as likely as not).Largest Earthquakes in the World Since 1900.Interesting world map showing a gaping quiet stretch along the Pacific ring of fire -- from Alaska to South America.
The Juan de Fuca tectonic plate along the Cascadia subduction zone is one to be concerned about. The Pacific Northwest coast would have maybe 30 minutes before a massive quake generated tsunami came ashore.
The last major earthquake in the Cascadia subduction zone occurred in 1700 and was estimated to measure about 9.0 -- give or take .2 Japanese tsunami records indicate the quake hit during the evening of January 26, 1700.
But on any given day, there is a far greater risk to your health from traffic on the roads to the coast.
http://earthquake.usgs.gov/earthquakes/world/10_largest_world.phpInteresting CalTech re-cap of the fault movements in the Sumatra quake:
http://www.tectonics.caltech.edu/outreach/highlights/sumatra/what.htmlThe giant 2004 Sumatra earthquake ruptured the greatest fault length of any recorded earthquake, spanning a distance of 1500 km (900 miles), or longer than the state of California. Rather than tearing the land apart all at once, the rupture started beneath the epicenter marked in the figure below and progressed northward along the fault at about 2 km/sec (1.2 miles/second). The whole rupture lasted about 10 minutes. Compare this with California's 1994 Northridge earthquake, which ruptured about 20 km (12 miles) and lasted 15 seconds. This giant quake of 2004 was followed just four months later by the magnitude 8.7 quake of March 28, 2005. This one was west of Sumatra, under the islands of Nias and Simeulue. Although the 2005 quake was one tenth as powerful as the 2004 quake, it is still the fourth largest quake of the last 100 years, and many lives were lost. A third major quake followed two and a half years later. The magnitude 8.4 event of September 13, 2007 rocked the Mentawai islands.
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