This threw me into a rabbit hole for a bit. Apparently there is good evidence that a lot of historical earthquakes in california were due in part at least to the oil industry, which early on would not replace pumped out oil with water.

Now a days they claim they replace the oil with water and all is well. However, as anyone who has owned an ancient used car and has switched from conventional to synthetic motor oil would tell you, there's no way that would work. The assumption is that these voids the oil are in are these hermetically sealed vaults such that one can simply pump in more volume of liquid and balance out pressures. That seems like a big assumption to me. Water is obviously not nearly so viscous as crude oil. It will seep in situations where crude will not. It's probably leaking out like a sieve if its really choss all the way down in California. The oil as it is isn't even very well contained given how common tar seeps are.

Agriculture probably also plays a role. Central valley has sunken what is it 20-25 feet now from historic ground levels? Same issue as a void generated by an atomic test or oil extraction, one would imagine. Mining probably also plays a decent role. Really anything involving removal or non like for like replacement of structural substrate from the ground is probably liable to be associated with seismic activity.

Kind of depressing a realization if this is the case, like we've screwed ourselves with not just the air but the ground we stand on too. You can't really get that stability back without all this new potential energy leaving the system in the form of stuff falling down and new quakes and plates breaking loose and budging a bit more.

> Mining probably also plays a decent role.

In the Johannesburg area in South Africa, gold mining has produced up to half of all gold ever extracted in the world, with mines reaching depths of 4000m.

This has resulted in frequent seismic events, in the 2.0 to 3.0 range on the Richter scale, occurring on a daily or weekly basis, more occasionally reaching 5.0. This started around 1906 and still continues today. See:

https://www.sciencedirect.com/science/article/pii/S167477551...

What kind of earthquakes in California ?

[dead]