Bermuda Triangle Earthquake Triggered...

Bermuda Triangle Earthquake Triggered 1817 Tsunami

There are 1 comment on the Live Science story from Sep 9, 2013, titled Bermuda Triangle Earthquake Triggered 1817 Tsunami. In it, Live Science reports that:

A "tidal wave" violently tossed ships docked along the Delaware River south of Philadelphia at about 11 a.m. ET on Jan. 8, 1817, according to newspapers of the time.

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“Geologist [I'm Climate Change]”

Since: Mar 07

formerly Nuneaton

#1 Sep 11, 2013

The crust relaxed over the bulk of the USA as a result of a megathrust Rebound/long duration Mercalli X (r/lx) event @ Cascadia in January 27 1700. The runout vector for the bulk of the crustal relaxation was WNW. with the max relaxation in a line from central Oregon through Colorado.

Draw a great circle from the crustal relaxation & it goes through the New Madrid region (big earthquakes from rifting in 1812). and through Charleston (big quake in the latter 19th century).
Continue the great circle onward and it reaches the Bermuda triangle. This quake appears to make up the set & indicates that the plate decompression wave from the 1700AD event crossed the entire continental N. America rather quickly.

Probably indicates that the N. American continent behaved like a rubber block rather than a gradually spreading decompression wave.

The variety of timing of major rift quakes in N. America across this great circle is therefore likely due to variances in the strength of graben faults rather than a wave of extension in the crust.

Of note also is that the 1700AD r/lx was a 2 stage event with 2 turbidites from shaking in Washington & E.Vancouver. The initial event struck N. California and swept up to the Washington-Vancouver junction box with a runout vector NW. relaxing the crust of the basin & range in E.California and the desert states. The 2nd event appears to have a WNW runout vector and broke the megathrust @ washington @ the junction box & decompressing E.Vancouver, Washington & extending back down to the California/Gorda junction box with the biggest runout @ central Oregon via a slow crawl. This 2nd event appears to be responsible for the rift quakes over the great circle area through the USA into the Bermuda triangle area.

The seismic quiet in Cascadia @ present is likely due to the NW-SE convergence between Juan de Fuca & the N.American plate @~4cm/yr still locked and unrelaxed @ the present time having been bypassed by the "hard edged" runouts of january 1700, which relaxed the stress built up by hotspot & rift induced spreading of the Basin & range backarc basin & gulf of California rift.

Of note is the absence of inclusion of Gulf of California rift spreading in the GPS models of ground motion convergence across Cascadia, There have however been more megathrust r/lx events in S. Cascadia than in the North, so this is a deliberate GPS omission rather than an absence.

Have a nice day: Ag

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