In June 2018 a stadium full of partisan soccer fans jumping with excitement as their team scored a surprise World Cup victory over Germany in Mexico City registered as an earthquake. In 2011 the Seattle Seahawks were playing the New Orleans Saints (the defending Super Bowl champions) and scored a 67-yard touchdown; the crowd went wild enough to register an M1.0 or 2.0 temblor. Remarkably, this was not the first time Seattle fans—who’ve also set a Guinness World Record for the decibel level of their roar—had registered on a seismometer. And back in 1988 a seismometer at Louisiana State University registered shaking from a football game between the home team and Auburn University.
This sounds like an April Fool’s Day story—but it isn’t. These incidents truly occurred and were covered in the media—but they made for great headlines and were misrepresented a tad. The Mexican fans really did go wild with excitement and sensitive seismometers in the nearby Institute of Geological and Atmospheric Investigations genuinely registered the resulting tremors, but it was not an actual earthquake. And in Seattle, the same deal. Every touchdown produced a characteristic signal on the seismometer—but the instrument was registering the vibration from thousands of people leaping up and down in unison—not the sudden movement of tectonic plates. The multitude of fans were able to hit the natural resonance of the stadium structure and to shake their neighborhood a little.
A study reported in LiveScience in 2011 (we can’t make this stuff up, even for April Fool’s Day) figured out that if everybody on Earth gathered together in one place and jumped about a foot in the air in unison, the planet would move only about a hundredth of the radius of a single hydrogen atom—and then immediately recoil back again. People jumping can’t move the ground beneath them enough to trigger an actual earthquake. But several other things that people do, may. Here are a few examples:
- Fracking and injecting wastewater. Induced earthquakes attributable to fracking and the injection of wastewater from oil extraction into disposal wells have been so much in the news in recent years that the issue rarely seems to hit the headlines anymore. An increase in pore pressure may alter the state of friction and thus reduce the sheer strength of pre-existing fractures, bringing them close to failure.
- Building skyscrapers. Taipei 101, a 770,000-ton high-rise in Taipei, Taiwan—the world’s tallest structure when it opened in 2004—has been blamed by local geologists for reopening an ancient fault and triggering quakes both small and large.
- Building dams: The weight of water accumulating behind a dam stresses the land beneath and can cause the ground to shift. Construction of the Hoover Dam in Arizona in the 1930s led to seismic activity that hit M5.0 on the Richter scale. An M6.5 earthquake closely followed the completion of the Koyna Dam in India in 1967, and in 2008 the Zipingpu Dam may have triggered a nearby earthquake in Sichuan, China.
- Nuclear explosions. According to the USGS, underground nuclear tests can cause earthquakes and aftershock sequences less energetic than the nuclear blast.
- Extraction. In 2000 Russian seismologists blamed natural gas extraction in Uzbekistan for three severe earthquakes, one of which measured M7.3 and was the most powerful recorded in Central Asia. Groundwater extraction near Lorca in Spain may have been responsible for a shallow earthquake there in 2011 according to research published in Nature Geoscience.
- Constructing enhanced geothermal-energy projects. Pumping pressurized water deep into the ground and sucking up the heated liquid to generate electricity was blamed for earthquakes in Basel, Switzerland, in 2006. A 2011 study published in Science notes growing seismic activity around the Salton Sea near the San Andreas Fault in California as geothermal field operations have increased.
Induced seismicity, as seismic activity caused by human activity is termed, is generally of a low magnitude but can occur far from the boundaries of tectonic plates where most natural earthquakes take place. It is not something you have to worry about, however, at your next football game.