January 16, 2012
by John Vidale
Our role model for a science blog, Cliff Mass's fascinating Weather Blog, suggests slushmageddon for this week. Snow has been suggested to set off earthquakes, as well as traffic jams, discomfort, and discontent with city emergency managers.
There is a real possible way for snow to trigger earthquakes - the weight of the snowfall changes the stresses in the ground. Basically, if a steep enough pile of material is formed, the pile will spread laterally, just as happens when one is too ambitious with a tall sand castle. Of course, adding snow to our mountains only "steepens the slope" a tiny amount, but the principal is the same.
We think the ground already is loaded with about as much stress as it can bear without rupturing in an earthquake, so a tiny amount more might have an effect. The same argument can be made for rain, wind, ocean currents, atmospheric pressure variations, erosion, and even adding buildings to a patch of ground like downtown.
A heavy snowfall could be 30 cm (about a foot), and snow has about 10-20% water, so that is considerable weight dropped on the land. Heavy to us, at least, although not heavy compared to the massive rock underneath. We don't know exactly how close the ground is to spawning an earthquake before the snowfall, so the best way to tell the effect is to see whether snow has caused earthquakes in the past around the world.
Several reputable studies have seen an effect. In one by Kosuke Heki, also described here, the rate of big earthquakes over the last 1500 years in Japan were three times higher during the six months when the snowload favored fault movement than when it didn't. The snow in the studied area was deep, equal to a meter thickness of water.
The figure shows snow depth through a year at three places, and a map of maximum snow depth.
If we believe this study, snow can affect the rate of earthquakes. However, the effect is small. In the study, 10 to 20 times as much weight is laid down as is likely in our local Slushmageddom, and it persists for the winter, stressing the ground for months. Also, even in the Japanese winter in the mountains, the danger is not high - a winter rate three times the summer rate just means 50% higher risk than average in the winter and 50% lower risk than average in the summer.
So yes, a big snowstorm can raise the expected rate of earthquakes, but only ever so slightly, and far, far too little to warrant action.
- Ice avalanches on Cascade volcanoes
- A New View On What's Shaking on the Cascade Volcanoes
- Seismic Spectrograms - A new way to look at wiggles
- The final football game analysis
- The Football Game Experiment Continues
- Seismic Game Analysis
- PNSN Earth-shaking Seahawks Experiment
- Large Mount Baker debris Avalanche this fall
- Speedy ETS in the works
- Peppy seismic swarm 20 km NW of Mount St Helens
- 2014 (7)
- October (1)
- September (1)
- August (1)
- June (1)
- April (3)
- March (4)
- February (1)
- January (2)
- December (1)
- November (2)
- October (3)
- September (1)
- August (3)
- July (2)
- June (4)
- May (4)
- April (2)
- The wech-o-meter takes over all of Cascadia
- Keystone Cops: Italy prosecutes seismologists for failure to predict deadly quake
- UFOs in eastern Washington? No, rather UTEs (Unidentified Terrestrial Events)
- New Sodo Seattle Liquefaction Array Installed
- Why we should constantly watch the deformation of the seafloor
- Mystery chirp near Newberry Volcano
- Planting seismographs causes earthquakes? or maybe ice-quakes?
- Tunneling rumbles south under Capitol Hill
- 15 years of mostly silent magma inflation near Three Sisters, Oregon
- Mount Hood earthquake swarm of Feb 23, 2012
- Web glitches: duplicate (and even triplicate!) earthquakes
- How earthquake magnitude scales work
- Mine blast masquerades as volcanic tremor
- The Spokane Swarm about 10 years ago
- Another hum around Mount St. Helens
- Slow slip: A new kind of earthquake under our feet
- PNSN and social media
- 3am M3.4 earthquake in St. Helens Seismic Zone
- The wrong kind of volcano noise
- Fast chatter on Rainier an hour ago
- Can slush-mageddon trigger earthquakes?
- Rainier Repeating Earthquakes Update and Comparison with Weather Patterns
- 22-minutes drumbeat icequakes(?)
- Mount Rainier popping away
- Repeating Earthquakes on Mount Rainier - are glaciers the culprit?
- Debunking another SEC football myth by the PAC-12
- One year ago, Seattle Seahawks 12th Man Earthquake
- The odds this year of a megaquake on the Pacific Northwest coast
- Is the plague of great earthquakes this decade a sign of increased danger?
- Nile Valley landslide talks to PNSN seismologists
- Good vs evil in central US earthquake hazard analysis
- Why does a volcano scream?
- Predicting big quakes from patterns of little ones
- 1-hour warning for Japanese M9 earthquake?
- Sound Transit train under Interlaken keeps a rollin'
- Invisible changes under the hood at the PNSN
- Sound Transit Tunneling Noise
- "Visionary" toads
- Earthquake early warning in the PNW
- November (1)
- December (13)