Last edited Sat Jul 6, 2019, 11:36 AM - Edit history (2)
in terms of the foreschock/aftershock dynamics.
In August 1989, there was an M6 quake in Santa Cruz. Having lived all my life in California, earthquakes were for me routine. At least there were until that moment. I'd experienced 6-magnitude quakes before, but this one was different. Something about it – I think that it was the unusually long duration of the quake– just gave me the creeps.
That August quake was later defined officially as a foreshock to the Real One, the Loma Prieta quake of October 1989, which was (like the second Ridgecrest quake) ~M 6.9/7.0.
Experiencing both the August and October 1989 quakes gave me a new gut-level feeling for the logarithmic scale.
On the 4th, a SoCal friend of mine told me that the first M6 Ridgecrest quake was unusually long - at least where she lived (more than 100 miles from Ridgecrest).
Her account reminded me of that August 1989 quake, and got me to wondering whether that Ridgecrest quake was a foreshock, too. Which of course it turned out to be.
Also, neither the Ridgecrest quake nor the Loma Prieta was on the San Andreas fault.
There are differences, of course (for instance, the Loma Prieta quake was unusually deep). Nevertheless, I found the similarities in foreshock/main event dynamics kind of intriguing.
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