There has been a swarm of quakes the last 2 days beneath Yellowstone lake up to M3.8. The depths given are very shallow: 100 m to 700 m. Probably something hydrothermal if really that shallow: there is quite a lot going on beneath that lake and I saw a talk about a year ago...where there have been some large (phreatic?) explosions over the (centuries? millenia?).
Chris

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