Did you feel that rumble Friday night when Jorge Polanco hit the game-winning single in the 15th inning to advance the Seattle Mariners to the American League Championship Series?
Probably not, if you weren't among the more than 47,000 fans attending the sold-out T-Mobile Park game who jumped, screamed and clapped in celebration of the Mariners’ historic win over the Detroit Tigers.
But for those lucky attendees, the ground shaking felt briefly like a “little earthquake” — similar to a big truck rumbling by — according to seismologist Mouse Reusch of the Pacific Northwest Seismic Network, which installed a temporary seismometer on the ground floor of the stadium.
The seismometer measures ground vibrations caused by fans in the stands, “from people jumping up and down mostly,” Reusch said. The network plans to keep the device installed for as long as the Mariners are in the playoffs, she said.
Throughout the game Friday, the network published in real time readings of the seismic activity on its website, along with annotations highlighting key moments from Friday’s game that can be spotted in the waveforms.
A “little caterpillar” of waves formed just after 5 p.m. marking when the players came out for the national anthem, Reusch said.
When the Mariners’ George Kirby struck out the Tigers’ Spencer Torkelson to end the top of the first inning, “that was our first real test that we are able to see changes in the crowd move, and how much they’re moving with excitement,” Reusch said.
The wave flattened out when Kerry Carpenter hit a two-run homer to give the Tigers a 2-1 lead in the top of the sixth inning.
“People were not happy, so people are kind of just standing there,” Reusch said.
The game’s first major shake was when Mariner Leo Rivas hit a single to tie the game in the seventh inning. The seismologist labeled it the “Rivas Rumble.”
Then there was a long lull in major seismic activity, as the innings dragged on and the crowd's energy waned. “We were in for the long haul,” Reusch said.
Just before 10 p.m., the seismologists saw a small spike: The crowd woke back up and the stadium rocked with jubilation during the game's second Salmon Run of the night, as Humpy the Salmon triumphantly burst through the finish line to his first-ever win.
And finally, the seismometer recorded a huge jump, dubbed the Polanco P-wave, when Polanco hit the game-winning single in the 15th inning.
The vibrations from the elated crowd lasted longer than the “Rivas Rumble,” but technically the peak was only slightly higher, Reusch said.
“Who knows, maybe people weren’t jumping as much because they were tired,” Reusch said. “But they were certainly very excited.”
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