I found this was interesting in SciAm

Link to Science, where this was published

>>For earthquake warnings, each second counts toward characterizing a fault’s rupture. Ruptures from large earthquakes, particularly those offshore, may have varying speed profiles that can only be resolved by dense arrays. In 2022, Atterholt et al. deployed a distributed acoustic sensing array along a 15-kilometer-long coastal telecommunications fiber with channels every 5 meters (see the Perspective by Brodsky and Ruiz). The array provided a second-by-second recording of the 2024 moment magnitude 7 earthquake offshore of Mendocino, California. Beam-forming analysis of P-wave arrivals showed that 8 seconds after the earthquake, the rupture slowed when it encountered the Mendocino Triple Junction and then jumped to supershear velocity before moving onshore. <<