the drought in the west has caused the land to actually rise, according to this.
however, they say it* doesn’t* raise the risk of earthquakes. why wouldn’t it? 
because a change as big as that described sure seems like it might set off a fault or two.
I accept that this comes from the acknowledged experts in the field, but it has me kind of scratching my head. So ground water is missing and that makes the terrain rise? Water tends to be much lighter than even the most porous rock, so… huh? It seems like the geological cross-section would have gotten denser, provoking a sinkage.
My understanding is that draining the aquifers causes the land to sink… and that some areas of the Valley have sunk so much there’s no chance of replenishing the aquifers, like trying to refill a crushed beer can.
Anyway, I wonder if this rise is unrelated to water and does indeed have to do with tectonic movement, which is going to affect earthquakes one way or the other.
Earthquake initiate deeper than the affected areas.
It is to do with weight. Approximately 250 billion tons of weight has been removed with the water going away
Changes in ground or surface water are known to trigger strong earthquakes, but that’s only if there’s an existing seismic hazard. That’s what happened with the earthquake in China a few years ago: the filling of a reservoir caused a near-surface fault to move. It probably would have moved eventually, but its believed the subsidence caused by the weight of the water triggered it.
However, that’s only an issue if there’s a near surface dip-slip fault (i.e. one with vertical displacement) that’s loaded up just right. The point I think the geophysicist was probably making before it was translated to popular magazine article speak is that the major seismic hazards in California are mostly strike-slip (i.e. horizontal displacement) so subsidence or uplift shouldn’t make a difference. That’s probably a bit of an overly general statement because there are plenty of dip-slip hazards in California, but they do tend to be deeper than the strike-slip ones.
In most cases, the groundwater gets replaced with air which results in overall less density in the rock column, allowing for uplift due to isostacy and tectonics. Subsidence from aquifer depletion only happens in certain types of aquifers and results from removal of water at a rate way faster than what’s happening simply from climate. It’s very localized, as evidenced by the fact that some (but only some) of the stations in the Central Valley are still showing subsidence despite the regional trend.
You’re talking about two different processes. As MG1692 says, the rising land described in the article is due to the weight of the water. If you take that much weight off of most materials, they’ll bounce back up a little. Soils are somewhat elastic, and removing vertical stress lets them rebound a bit.
The settlement you refer to happens when we pumping water from a confined (pressurized) aquifer. In that case, pumping water reduces the pressure of the water that remains. In fluids, pressure pushes simultaneously in every direction, so the pressure of the water is pushing the grains of sediment apart. Releasing that pressure reduces those forces, letting the grains settle back in a tiny bit closer together. As you release more and more pressure, the soil consolidates and the land surface settles.
I know, but that’s a relatively trivial amount in geologic terms, especially when spread over 1/4 or more of a continent.
It sounds overstated, misunderstood or misinterpreted.
I assumed it was the weight, as a sponge is heavier wet than if it dries out.
and the drought-caused water loss is mostly (or even all) surface water and the soil, never deep, then? and it’s happening gradually, might that have something to do with it?
anyway, I thought the stars were looking a tiny bit closer…
AB - the northern parts of the northern hemisphere are still rebounding from the removal of the ice sheets 10000 years ago, which - let me check my sources - yes, were composed of water.