If the disasters wreaked upon multiple locales across California this winter aren't enough, all the rain we've had seeping into the ground could, potentially, cause groundwater pressures that induce earthquakes along the state's faults. This theory is being put forward in a piece from The Conversation, and it's all speculation at this point, but there is data to suggest that human activities, and maybe even extreme weather, can induce earthquakes, and a series of California earthquakes this year could give scientists new reason to connect heavy rain with seismic activity. This of course would prove that "earthquake weather" is indeed a thing, just the opposite of what most people have referred to as "earthquake weather," i.e. hot, sunny, and windless.
The article could be called irresponsible in its creation of a whole new round of earthquake fears for no documented reason, but The Conversation points to data related to oil and gas mining and how the injection of water into boreholes can be a trigger for tremors. We already know that fracking has caused an unprecedented number of earthquakes in Oklahoma, and scientists earlier put forward a theory that extremely heavy rain in Germany in 2002 triggered a swarm of earthquakes there.
They also point to incidents of earthquakes connected with the filling of large water reservoirs behind dams, like one that occurred in India in 1967 near a relatively new, 35-mile-long reservoir.
Working against this theory would be the fact that California suffered a major, 100-year or 200-year flood back in 1862 caused by intense winter rain which similarly followed five years of drought, and no major earthquakes were reported that year or even the three years after that.
Again, though, a lot of this is just theory! And here's a key caveat paragraph from the piece:
Scientists are now presented with some exciting challenges. Earthquakes can produce a “butterfly effect”: Small changes can have a large impact. Thus, not only can a plethora of human activities load Earth’s crust with stress, but just tiny additions can become the last straw that breaks the camel’s back, precipitating great earthquakes that release the accumulated stress loaded onto geological faults by centuries of geological processes. Whether or when that stress would have been released naturally in an earthquake is a challenging question.
Right, so, just one more thing to add to the list of things to panic over, but it would be silly to panic until the earthquakes start.