Bay Area is long overdue for a major earthquake | Hacker News Reader

Bay Area is long overdue for a major earthquake

cnn.com

15 pointscodegeek7 comments

What is with headline writers?

> The last major tremor on the Hayward Fault was a magnitude-6.8 event that happened in 1868 -- exactly 150 years ago. So the region is almost overdue for another one.

"Long overdue" is not "almost overdue." But it probably gets more clicks.

There is no such thing as being "overdue" for earthquakes, if they ran on predictable schedules things would be a lot simpler, they don't.

But they aren't Poisson processes either. (A Poisson processes has an equal probability per unit time, regardless of how long it has been since the last one.) With earthquakes, the probability increases over time as strains build up across faults, until they are suddenly released.

Yup, but you do not know whether the strain will be released in a big quake or many smaller quakes. You could be at a state where a lot of strain has built up and a megaquake could seem immanent but then a smaller quake relieves some of the stress and "resets the clock". And then are you still "overdue" or not?

The way things work over very long periods of time is that some faults exhibit some degree of periodicity in terms of large quakes. But simplifying that periodicity into the concept of being "overdue" for a big quake is intellectually irresponsible.

Additionally, the longer the strain builds up, the greater the eventual release will be, although it’s possible in some cases for the energy to be released in a series of smaller events. In the case of this fault however, on geological time scales, it’s more or less like clockwork. There is also the possibility of such an event triggering, perhaps st some temporal remove, the release of other faults such as the San Andreas.

I live in the Bay Area and after growing up on the Gulf Coast and accepting 1-4 hurricane hits or near misses per year and seeing a lot of tornados/floods, a totally random earthquake seems acceptable. Can't do anything about either natural phenomena except be prepared as possible. Knock on wood.

I don't live in an earthquake-prone area, but this is a good reminder to fill up my water jugs and prepare a small stash of supplies.

I have a friend who watches the earthquake reports. He's pointed out how gravitational vectors lining up make big quakes more likely. It's something about the times the moon is closer to the earth [0], new moons [1] (when the moon is between the earth and the sun), etc.

[0] https://en.wikipedia.org/wiki/Lunar_distance_(astronomy) [1] https://en.wikipedia.org/wiki/New_moon

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