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Earthquake Insurance and You

In an article published today on the web site, Lucas Eichman discusses earthquake insurance in California.  He quotes Glenn Pomeroy, CEO of the California Earthquake Authority:   "Lets say the 7.2 (Baja earthquake) that happened on Sunday happened under Los Angeles.  We would see massive destruction.  Homes destroyed.  Infrastructure badly damaged."


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Aftershocks are earthquakes that are triggered by a previous, larger earthquake mainshock.  Today we know that aftershocks are a result of the transfer of stress from the region of the mainshock to surrounding, smaller faults.   About 5%-10% of mainshocks have foreshocks, which can be regarded as instances when the aftershock is larger than the mainshock.

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Earthquake Correlations - II

In the year 1657, the Dutch scientist Christian Huygens observed that if two pendulum clocks were mounted adjacent to each other on the same support, the subtle and almost imperceptible vibrations of the swinging pendulums would cause those pendulums to become synchronized, swinging in opposite directions.  He referred to this phenomenon as "odd sympathy".

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Earthquake Correlations

Haiti, January 12, 2010, magnitude 7.0.  Chile, February 27, 2010, magnitude 8.8.  Baja, April 4, 2010, magnitude 7.0.  Sumatra, April 6, 2010, magnitude 7.7.   Are they related?  Although it is rather unlikely, the simple answer is that no one knows for sure, because it is a very difficult proposition to unequivocally prove. 

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Today's Magnitude 7.7 Sumatra Earthquake


Yet another earthquake occurred today in Sumatra, Indonesia.  Preliminary estimates place the magnitude at 7.7, a very large earthquake.  The depth was about 30 km.  Earthquakes of this size can cause damage, injuries and deaths as was seen in Haiti. A tsunami watch was issued.

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Yesterday's Magnitude 7.2 Mexicali Earthquake

About 40 years ago a Japanese seismologist by the name of Kiyoo Mogi proposed the idea that before a large earthquake occurs, there are a series of earthquakes of increasing magnitude that occur as a "run-up" to the main event.  These events surround the eventual fault that breaks in the main earthquake in a kind of "donut" pattern, with the main earthquake then occurring in the "hole" of the "donut".  Since that time, seismologists call this type of precursory pattern a "Mogi Donut". 

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When Charleston was Destroyed

On January 9, 1861, the first shots of the American Civil War were fired in Charleston, South Carolina.  Cadets from the military school "The Citadel" opened fire on the Union ship Star of the West as it was entering Charleston harbor.  Twenty-six years later, the city of Charleston was destroyed by the largest earthquake to strike the eastern United States in recorded history.

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Can toads predict earthquakes?

Using animals as a possible early warning for earthquakes is nothing new: Chinese researchers began a systematic study of unusual animal behavior and in December 1974 predicted a major earthquake that did, in fact, occur in February 1975.  Skeptics, however, are quick to debunk nearly all such observations. For the 1975 prediction, it was pointed out that most of the information came from a series of strong foreshocks.

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The Story of Immamura and Omori

In his 1980 presidential address to the Seismological Society of America, the great seismologist Keiiti Aki told the story of Fusakichi Omori and Akitune Immamura, and of the great Kanto earthquake of September 1, 1923.  That event destroyed the metropolis of Tokyo and killed over 130,000 persons, laying waste the cities of Tokyo and Yokohama. 

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East Coast vs West Coast Earthquakes: The Good and the Bad

In the past several years, damaging earthquakes appear to be on the rise and it seems that every few months a big event happens (Sumatra, Samoa, Haiti, Chile, Italy etc).  It turns out that globally, large earthquake rates have not changed, but unfortunately the past several earthquakes have occurred in populated areas, some of which have poor building practices.  This only brings home the need to better understand our risk in North America.


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