Come Sunday in Seattle, the American football stadium will be rocking 鈥� and there鈥檒l be seismic sensors there to prove it.
The stadium is home to the National Football League鈥檚 Seattle Seahawks and renowned for its raucous crowds. In January 2011, the team鈥檚 Marshawn Lynch ran his way into team history with an improbable game-winning touchdown (pictured), the reaction to which registered at a seismic station 90 metres from the stadium.
Now the stadium itself is wired to pick up crowd tremors, and starting last week, researchers at the (PNSN) began streaming live seismic readings out to fans, and using the experience to test their readiness in case a real earthquake strikes the seismically active region.
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鈥淲hat better way to get the ground truth than really getting our instruments inside the stadium?鈥� says , who leads the project at PNSN. 鈥淗ow does a crowd energise the stadium structure and the ground below to shake?鈥�
Seismic kicks
Malone was the principal scientist responsible for seismic monitoring of Mount St. Helens when it erupted in 1980, and kept tabs on other volcanoes in the Cascade Range. He admits that the Seahawks station is a light-hearted project, but says it鈥檚 a useful one nonetheless.
The 67,000-seat stadium is the first to boast its own seismic station, says Malone. Seismic data could provide a rare look for civil engineers interested in how a particular stadium design handles the unique load of an active crowd. The new station is giving his staff valuable practice in installing and monitoring seismic equipment, recording and interpreting data in real-time, and relaying that information on the PNSN website for the public.
鈥淲e haven鈥檛 had even a moderate-sized earthquake in several years, so this has been a great fire drill,鈥� he says. 鈥淭he experiment simulates what we鈥檇 do in a real earthquake almost exactly.鈥�
Hawk-o-meter action
On Sunday the system will undergo its second test, as the Seahawks take on their archrivals, the San Francisco 49ers. Fans will be able to log on to the and watch the seismic activity detected at the stadium鈥檚 three sensors as it spikes and drops in real-time with each big play on the field. They can check back, too, for the PNSN staff鈥檚 .
Malone says that the surge in PNSN website traffic during the game last week 鈥� which swelled from a normal 2000 to 3000 visits up to 12,500 visits 鈥� caused some glitches and delays. But the challenges were informative for the PNSN team in preparing for website traffic during an emergency, as PNSN is responsible for monitoring quakes in the entire Oregon-Washington region.
Douglas Dreger, a seismologist at the University of California, Berkeley 鈥� and a 49ers fan who鈥檚 hoping for a quiet day for Seattle fans 鈥� says it would be interesting to see if seismic waves produced through different kinds of crowd-responses during a season have any shared characteristics. 鈥淚f there鈥檚 a prominent commonality in these signals, it might tell us something about the natural response of the stadium, or the stadium-soil system,鈥� he says. That could help civil engineers in the area, as well as seismologists investigating the rigidity of the earth for better earthquake prediction.
Though interesting for engineers and as a test of emergency services, Malone says, the crowd-generated seismic blips are nowhere close to the strength of a real earthquake. And though Seahawks fans like to boast that they are the loudest in the NFL (they hold the Guinness world record for loudest outdoor stadium, at 137.6 decibels), seismic sensors won鈥檛 be able to confirm that: they register shaking from body movement like stomping and dancing, but not audible cheers.
