Looking at Three Big Quakes in the 1870s

The purpose of this post is strictly to present some food for thought.

The previous post on Saturday, August 10, 2016 noted those two big earthquakes in 1872. The first was the Lone Pine (Owens Valley) quake on March 26, with an estimated magnitude of 7.4 to 7.9 (link). Then, approximately 9 months later came the largest earthquake recorded in Washington state, on December 14, 1872. Estimates for the Washington quake have been as high as M7.5.

It is interesting to note the spacing between the California quake and the one in Washington. Again, there was about 9 months between. Then there was about an 11 month span, and then came the Brookings, Oregon quake, which hit on November 23, 1873. The Brookings quake is said to be the largest in recorded history for Oregon. In 2002, that quake was re-evaluated and upgraded to an M7.3. This is up from the former estimate of an M6.7 (link).

The Owens Valley quake of 1872 was centered on the east side of the Sierra Nevada, where the landmass appears to be rifting. The Washington earthquake of 1872 appears to have been centered on the east side of the Cascade Mountains, and may have been associated with a deep-seated, ancient rift. In the previous post of August 10, there is noted a connection between the rifting in the Walker Lane in California (to the east of the Sierra Nevada) and the Cascadia region. Then there is that 1873 Brookings quake, which appears to have been centered to the west of the Klamath Mountains.

It should be noted that the Klamath Mountains were formerly oceanic islands which appear to have been situated on top of the oceanic rift system. That was before it was forced deep under the continental landmass in the great collision in earlier times. In that collision, the islands were deeply embedded into the continent, clear up to the Cascade Mountains.

Now for something to think about. Was it just a coincidence that these three very large earthquakes occurred relatively close together in the early 1870s, or is there possibly a much greater connection, geologically, than people commonly realize? Is there any importance to be found in the sequence in which these three large earthquakes occurred, plus their specific locations? And then, since that time, things have been relatively quiet on the western coast of North America. Is there any importance in this relative quietness? Is there any chance that it may be similar to the proverbial calm before the storm? Indeed, what may the future hold?



For further reading:

Current Expectations for a Cascadia Mega-Quake
https://cascadian.neocities.org/cascadiaquake.htm