According to the Pacific Northwest Seismic Network website: When enthusiastic Seahawk fans jump up and down and shake the stadium (and the ground under it) we record those vibrations on nearby seismographs but don’t call them earthquakes. Such shaking was first recognized at the PNSN back in 2011 in response to a spectacular Marshawn Lynch run that was named a “Beast Quake”. In anticipation of more stadium shaking events last year we installed several seismographs in CenturyLink Stadium to record fan enthusiasm for the Divisional playoff game against the Saints and the NFC Championship game against the 49ers. We learned a lot, but there is more to learn. So lets do it again.
Seahawks Monitoring Page (HERE)