December 2, 2011
by John Vidale
Since last summer, Sound Transit has been tunneling from Husky Stadium towards the future Capitol Hill station. The tunnel boring machines (TBMs) are now 100-200 feet underground near Volunteer Park, and progressing 50-100 feet per day. Behind them, trains run to deliver the tunnel wall sections, which are assembled as the TBM progresses. The CHS Capitol Hill Seattle Blog has lots of details.
The work is apparently causing noticeable vibrations in the Montlake and perhaps wider neighborhood. This site has more details. Following widespread complaints, the PNSN installed a new seismometer, and verified the noise.
Shown below is a seismogram (vertical component of acceleration) recorded on the foundation of a house on 19th Ave East, just below Interlaken Park. The train signal, which likely results from couplets of pops caused by pairs of wheels of cars in the train crossing track junctions, lasts about 100s as the train passes underneath.
This four-minute signal was recorded at 9:15am (17:15 UTC) yesterday, December 1st. The peak amplitude of 6000 counts corresponds to an acceleration of 0.25% g, above the limit of perceptibility. The shaking is possibly greater higher in the house.
A spectrogram shows the frequency content of the shaking, plotted over the duration of the signal.
This spectrogram ranges from 0 to 80 Hz, and shows most of the energy is in the range 20 to 60 Hz, matching the frequency content reported by a study for Sound Transit. This information allows us to take a look at the source mechanism and to test future recordings to see how loud, common, at what times of days is the disturbance.
[added at the next day:
We've lowered the automatic triggering threshhold so that we don't need to recover data from times of manually reported noises, and now many similar events are being detected. Here are the traces. Clearly, if these signals come from the trains, the issue is their loudness, not whether they can be felt.]
- The Great ShakeOut 2014 is Tomorrow!
- Three Cascadia ETS events in past month??
- Is Mount St. Helens seismicity increasing?
- Warm weather triggers snow avalanches at St. Helens
- Seismic recordings of a gas explosion in North Bend, WA
- Seismic signals generated by the March 22nd Oso Landslide
- Legacy web site content returns
- 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
- October (1)
- September (1)
- July (1)
- May (1)
- April (1)
- March (2)
- February (3)
- January (4)
- 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)