December 31, 2011
by John Vidale
Seismology occasionally fascinates the public, an occupational hazard that struck the PNSN last January.
The source time function was a professional football player: Marshawn Lynch, whose spectacular 15-second touchdown run assured the local Seahawk team an unlikely and coveted victory on January 8, 2011, and a victory in the playoffs. Through the response of the roar and stomping of the tens of thousands of feet, the ground shook enough that the vibrations were recorded by the Pacific Northwest Seismic Network (PNSN) strong-motion station KDK, a block or so away. One-station signals are always hard to verify, but the timing matched. Recordings revealed a peak acceleration of about 1/20,000th of a g, and peak motion of about 1/100th of a mm.
I spotted the wiggles on our seismogram, PNSN manager Paul Bodin verified the signal, and PNSN information officer Bill Steele forwarded the mostly unintelligible plots to a few local reporters. The next day, reports appeared everywhere, and the Seattle Times created a great visual (see figure). By the end of the week, Google reported 3,600 news outlets had the story, many reporters showed a spectrogram, hits on my name in Google had bumped up by 5,000, several long-lost friends resurfaced, and the story ran its course.
Then, with the possibility of the Seahawks playing another game in Seattle two weeks later, I felt compelled to verify that the “12th man earthquake,” or “beast quake,” was real and unique. I plotted the signal levels for all the home games of the 2010 season, shown below. The Saints game is the second row, with the Beast Quake in the red circle.
Indeed, no other signal of comparable amplitude, duration, and frequency content had happened during that game or the other eight home games this season—although I found a number of similar signals that were shorter and half as big. Also, more noise that was plausibly the play-off pre-game show, the raucous fans and their cars carousing out of the area afterwards, and some unidentified background noises. The fans seemed less raucous after the few losses.
The Seahawks lost their away second-round playoff game, so, perhaps fortunately, fans did not have a chance to recreate or surpass their ground-shaking record, perhaps challenging the stadium. No one in the media asked how much the ground shook; only the engineers guarding the nearby and vulnerable Seattle seawall and viaduct inquired about this critical magnitude. One and all were content with the news item, except perhaps Saints fans and a Deadspin commentator.
(Blog entry is partly from a short article in the Seismological Research Letters.)
- Great ShakeOut, Great success!
- 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
- October (2)
- 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)