in late January 2010, this swarm is the second-largest ever recorded in the Yellowstone Caldera. Interestingly, most of these swarms have "rapid-fire" characteristics: they seemingly appear out of nowhere and can churn out tens or hundreds of small to moderate quakes within a very short time frame. Such swarms usually occur within the caldera boundary, as was especially the case in 2018. The Guy-Greenbrier earthquake swarm occurred in central Arkansas beginning in August 2010. Epicentres show a linear distribution, with a clear overall shift in activity towards the southwest with time, and a magnitude of 4.7 was computed for the largest event. Analysis of the swarm has suggested a link with deep waste disposal drilling. It has led to a moratorium on such drilling. On 2 September 2017, an earthquake swarm appeared around Soda Springs, Idaho. Five quakes with magnitudes between 4.6 and 5.3 occurred within 9 days. Keeping the 2009 L'Aquila case in mind, and because Idaho had experienced an M6.9 earthquake in 1983, experts warned residents that a stronger quake could follow (an unlikely but still possible scenario for them). From early 2016 to late 2019, a swarm of earthquakes occurred near Cahuilla in Riverside County, California. More than 22,000 individual seismic events were recorded—ranging in magnitude from 0.7 to 4.4 -- the strongest one occurred in August 2018, south of Lake Riverside, just off Cahuilla Road (SR 371). By using computer algorithms and machine learning, researchers were able to infer the following detailed picture of the Cahuilla fault zone responsible for the earthquake swarm. The fault zone is no more than wide, long, with the earliest seismic swarm events localized down near its base at below the surface and the latest events migrating upwards to below the surface and spreading throughout the fault zone's length. Containing complex subterranean horizontal channels and prominent bents in its depth profile, the fault zone sits on top of a deeper natural underground reservoir of fluid under pressure with a connector at below the surface that was initially sealed off from the fault zone. When that seal broke open in early 2016, fluids were injected up into the fault zone's base and diffused slowly through the complex channels up to below the surface, which triggered the prolonged earthquake swarm that lasted until late 2019. This analysis provides detailed evidence that fault zone valving is a mechanism for seismogenesis in swarms. Atlantic Ocean