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Author Topic: How frequent are Earthquakes off the British Columbian coast fault?  (Read 5112 times)

Offline LeeE

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I just noticed (using Google Earth) a recent 4.5 quake off Kunghit Island, British Columbia, and while it's not a terribly strong quake it looks rather isolated.  Any comments?


 

Offline Bass

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This earthquake is in an active seismic zone near a triple junction- the spot where a spreading center, a subduction zone and the Queen Charlotte fault (a major strike slip fault similar to the San Andreas) meet.  The 4.5 quake occurred along the Queen Charlotte fault.  One of the largest measured Canadian earthquakes (8.1M in 1949) was centered along this fault not far from this epicenter.



Diagram is from the USGS earthquake page
« Last Edit: 17/12/2009 00:32:22 by Bass »
 

Offline JimBob

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The fault running closer to the coast of the US averages a major destructive earthquake of magnitude 7 or greater every 500 to 1000 years. The last major quake, estimated to be 8.1, was in 1700 according to Japanese records.
 

Offline LeeE

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Thanks guys.  Interesting to note that the 1949 M8.1 wasn't far away.  I actually missed the fact that there had also been an M4.7 down off Oregon the day before.

JimBob: I assume your reference to an M8.1 in 1700 was actually the M9 1700 Cascadia quake that 'started' in Northern California?

I assume you two guys already know about the USGS Earthquake monitoring plugins for GoogleEarth, but for anyone else who's interested, there a couple available from the USGS website: one shows EQs by magnitude and date and the other by magnitude and depth, and both plate boundaries.  The only problem I sometimes have with them is that the magnitude sizing of the markers sometimes goes a bit screwy and displays all of the markers at the same size :(

Edited: oops!- Plate boundaries, not fault lines.
« Last Edit: 17/12/2009 10:23:28 by LeeE »
 

Offline JimBob

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NOPE !!

I did mean "Japanese records" - there was a very large and damaging tsunami in their written history that, if memory serves me right, damaged most if not all of Edo, Japan. Edo is now known as Tokyo.


BUT why quibble - we are speaking of the same earthquake.
 

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