After a recent post on earthquake preparedness, a reader indicated an interest in knowing what earthquakes did to wells (both water and gas) and their distribution. The question made me conclude I didn’t know enough about that topic, so I did some research. Here’s what I found.
What’s predicatable about water wells in earthquakes:
Earthquakes often cause a temporary but significant oscillation in water levels during the event. As layers of rock get compressed and flexed (earthquakes are awesome in their power!), the spaces between and among layers where the water is held get squeezed and stretched. These short-term surges and retreats usually cause no trouble. Wells may jet or gush out water if they’ve an open top; or go temporarily dry, but that’s no big thing. Probably.
The “probably” part comes from my experiences with other kinds of pumps and fluid lines. I’ve seen both pumps and lines vapor lock. I expect a sudden drop in water level could leave the pump temporarily above water and cause a vapor lock. Air doesn’t move through fluid lines nearly as well as I used to expect. The problem is it’s too compressible: The pump pushes, but the gas bubble just gets smaller instead of pushing fluid through the line. When it happens in a blood vessels, we call it an air embolism; and those can kill. Priming the pump (refilling the line with gas-free fluid) tends to fix vapor locks.
What’s not predictable about water wells and earthquakes:
Well … about everything else. Will the water level show a change that lasts longer than the event? Will any change eventually go away; and if so how long will it take? What direction is any change likely to be; more water in the well or less? If my well went dry, did all my neighbors’ wells also go dry? How close to the epicenter does the well have to be to see an effect?
Most of these answers are completely unpredictable. As evidence, see the water levels in a bunch of USGS-monitored wells in the image below. Pretty much every well showed some fluctuation during the event. Some went right back to normal. Others showed a permanent drop in water level. Their neighbors may have seen a permanent increase. Some wells went back to baseline eventually, but not all.
A well will often fluctuate during an earthquake; and may be left with permanent water level change.
I did extract two trends from the data I looked at (these wells and some others on which the USGS reported):
1) Some of the affected wells were a looooooooong way away from the event. Those wells shown in that graph are scattered all over the contiguous U.S. states. And where was the epicenter of that quake? ALASKA. Sure, it was a banger of a quake, but that’s quite a far piece from the East Coast of the U.S.
2) Overall changes were not large; less than a foot for every case I could find. One sees reports of new wells opening up and old ones going dry after earthquakes; but the monitored wells showed permanent changes measured only in inches.
My take away about water wells after earthquakes
A quake, even a distant one, might definitely mess up a well. More likely, it won’t. If I depended on a well (we don’t around here; the aquifer is stupid deep making wells cost prohibitive), I’d spend the extra to get it dug a foot or two deeper than it needed to be. That would give me some safety cushion.
The real problem with wells of all types and earthquakes
All sources agreed on the biggest problem earthquakes cause related to wells. It’s not the wells themselves; it’s the distribution lines. Earthquakes trash distribution lines. The October of 1989 quake in San Francisco, for example, burst more than 150 good-sized water mains. Firefighters were reduced to using fire boats to fight land-based fires in the Marina district; and fires further inland did far more damage than otherwise expected.
Being buried underground protects water and gas lines from lots of things…but not earthquakes.*
So a prepper needs to think not only about what to drink after an earthquake might burst the mains, but also how to be protected from fire. It makes that metal roofing more attractive, for instance.
Speaking of fire … gas lines and earthquakes
Natural gas lines are more rigid than water lines. During earthquakes, they tend to detach where the gas line runs into the building. Yeah, leaking natural gas out in or beside the structure. Knowing where your gas inlet is and how to turn it off should be a high priority if you run gas lines into the house. Also, getting the place checked out before you move back in and start causing sparks would be a grand plan.
Some sources:
A US Geological Survey report on water well responses to various earthquakes, last modified Jan 2018: https://water.usgs.gov/ogw/bgas/eq-gw/
A report on the response of the San Francisco water supply to the quake of 10-11-89 from Art Jensen, the Acting General Manager of the Public Utilities Commission of San Francisco: http://www.sfmuseum.org/quake/svww.html
* Thanks for the image to GordonJ86 [CC BY-SA (https://creativecommons.org/licenses/by-sa/4.0)]
Thanks for the research and the post. The New Madrid series of earthquakes, the largest on February 7, 1812, was estimated at as much as 8.8 magnitude, The force of the land upheaval 15 miles south of New Madrid created Reelfoot Lake, drowned the inhabitants of an Indian village; turned the Mississippi river against itself to flow backwards; devastated thousands of acres of virgin forest; and rerouted and created two temporary waterfalls in the Mississippi. Boatmen on flatboats reportedly survived this experience and lived to tell the tale. Clearly preps need to include enough water to survive until adequate sources of water are reestablished. Not mentioned is the sewer lines in cities which, at a minimum, will contaminate broken water distribution lines and serve as another source of sickness. Just another one of many things for which to consider as you prepare for the unexpected.