This morning we were greeted with this headline about an overnight California quake. At first glance, the reporting made it seem like something important or unusual. Let’s take a closer look and put this in context.
This quake (top left of the picture) occurred a bit west of the Mendocino Triple Junction, the spot where the San Andreas fault ends. This tectonically-active area is where the Pacific Plate, the North American Plate, and the Juan de Fuca Plate all angrily merge together. It’s an inflamed spot on the skin of our violent planet, and no surprise that it should generate quakes.
Today’s quake–a Mw 5.1 –is nothing but a mild sneeze of the Earth. The unofficial geologic designation for quakes of this size is “meh.” There have been far bigger ones near the Mendocino Triple Junction. With a depth of just 24 km, this quake was felt at the surface, but wasn’t really anything approaching a big quake.
Of course, the Napa Quake last August also did not qualify as a “big quake,” though it did significant damage to areas in Napa and Vallejo. That really has more to say about the weakness of the soil in those places, and the vulnerability of our infrastructure, than about the size of the quake.
Perhaps the reason for the headline is that journalists are still a big trigger-happy in reporting because of the damage in Napa. At the same time, they tack the geologic context of this being no big deal.
It’s important to have the perspective that far, far larger quakes loom in our future, and if those quakes are more proximal to population centers, the damage will be significant. That’s the kind of headline we should be seeing from the media.