Изучение предвестников землетрясений выявило недостатки системы безопасности при гидроразрыве пласта

Here’s what you’ll learn when you read this story: - Hydraulic fracking, the primary method for accessing natural gas in the U.S., can also cause earthquakes, which are often signaled by foreshocks preceding the main seismic event. - A new study analyzing injection-induced earthquakes (IIEs) in the Western Canada Sedimentary Basin found that of the 77 recorded earthquakes caused by fracking, 92 percent of them were preceded by foreshocks. - While regulatory agencies use a traffic-light protocol (TLP) with seismic data to switch to a “red light” if an earthquake appears imminent, the study shows that the system is far from perfect. During the early days of the oil boom—an era ushered in with the drilling of the first commercial oil well in Titusville, Pennsylvania—precious “black gold” mostly sat in shallow pools, easily accessible with simple drilling. While some explosion-happy innovators laid the groundwork for what would eventually be hydraulic fracking not long after the Civil War, the technique, which involves pumping high-pressure fluid into the Earth to unlock trapped fossil fuels, didn’t progress rapidly until the 1990s. In the past three decades, fracking transformed the U.S. into an energy exporter while also instigating litigation and resistance. While fracking primarily accesses natural gas, which burns cleaner than coal, it’s still a dirty source of energy. The fluid injection creates mounds of environmental concerns, and, perhaps most troublingly, it can also cause man-made earthquakes. In 2015, a study published in the Bulletin of the Seismological Society of America reported that fracking caused a magnitude 3.0 earthquake in Ohio, and since then, scientists have only further confirmed the seismic side effects of this controversial mining method. However, these earthquakes often have one handy feature that helps mining operations avoid the worst-case scenarios. Foreshocks, minor rumbles that precede a much larger earthquake, allow regulatory agencies to use what’s known as a “traffic-light protocol,” or TLP. Much like a typical traffic light, green means “go,” but seismic data informs whether that metaphorical light ever turns yellow or red, slowing or shutting down operations. Now, in a new study, a team of scientists led by researchers at Zhejiang University of Technology in China closely examined 77 earthquakes in the Western Canada Sedimentary Basin in Alberta. They noted that of these 77 earthquakes—all greater than 3.0 in magnitude and identified as induced by fracking—92 percent were accompanied by foreshocks within five kilometers and five days of the main seismic event. The results of the study were published in the journal Science. While it’s enough to get a passing grade in school, 92 percent doesn’t cut it when earthquakes might wreak havoc on the local population. While magnitude 3.0 earthquakes are rarely felt, fracking can sometimes cause much bigger rumbles. In 2018, a magnitude 5.5 earthquake—the second-largest in the country’s history—hit Pohang, South Korea, injuring more than 70 people and causing millions of dollars in damage. Later, a study published in the journal Science confirmed the earthquake came from fracking nearby at a geothermal plant. In the new study, geophysicist Bei Wang and his colleagues discerned three main ways that fracking causes foreshocks, according to Science News. In the first, injected fluid gradually weakens a fault, which then creeps along over time. In the second, the fault gives way all at once. In the third, a series of small ruptures fires off in succession, like a line of falling dominoes. “The high prevalence of foreshocks supports a central assumption of TLP, but their highly variable productivity shows that warning capability is spatially conditioned,” the authors write. “TLP decisions should be region-conditioned with seismogenic susceptibility, real-time seismic-geodetic observations, and physics-based nucleation models to constrain evolving fault loading and guide operational responses.” Improving predictions of injection-induced earthquakes (IIE) will continue to be important even as the world weans itself off of fossil fuels. That’s because enhanced geothermal energy (EGS) relies on fracking to inject water in areas near super-heated areas to generate renewable energy. Because of the seismic activity in the American West, superhot rocks are relatively close to the surface, but injecting water to create energy there will still risk producing IIE earthquakes, as happened in South Korea. Whether clean or dirty, there’s energy locked underground, and after nearly 170 years, we’re still trying to find the safest way to unleash it. Darren lives in Portland, has a cat, and writes/edits about sci-fi and how our world works. You can find his previous stuff at Gizmodo and Paste if you look hard enough.