I Think I Felt The Earth Move

I lived in California, as a resident, for some 15 years (off and on... long story) and spent a good part of 4 years stationed there while in the Navy. Earthquakes are a concern in that state, though fires and mudslides ought to be, and I got a bit of an interest in them. I only felt a few mild ones while I lived there, nothing above a 4.0 (and that one was not close by). Still, the threat was enough to make me wonder about the causes and why California is prone to them.

There is the San Andreas Fault, of course. But there's more to it. California is above the eastern side of the Pacific Ring of Fire.


It also involves something called Plate Tectonics. You see, the earth is not nearly so solid, in geologic terms, as one might think. The surface plates (the lithosphere) "float" upon the asthenosphere like a fine crust of dirt layer on a thick mud. These plates butt up against each other along these fault zones. This exerts enormous pressure which eventually gets released and, thus, we get earthquakes.

Ok, that is a very simple explanation. And maybe only partially correct. But it will do for now. A couple of years ago, I noticed there was an increase in activity along the Ring so I went looking around in the internet for more information. And there I found earthquake.usgs.gov which has a nice little alert feature. They will send you emails triggered by quakes in the areas you interested in when they are of a magnitude you set as a threshold. So of course I signed up.

I noticed another uptick of activity recently and went to the site and found something of interest...

This is a map showing activity of a magnitude of 4.5 or greater for the past 7 days. Notice the Aleutian Islands and the cluster in California.



I am not trying to spread fear here, I just find it curious.



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