​​​ Abstract: This study evaluates whether abrupt geomagnetic changes systematically precede increases in local seismicity at the Chiles–Cerro Negro volcanic complex. Two unrest episodes, in October 2020 and July 2022, were analyzed using synchronized magnetometer records and seismic catalogs within ±7-day windows. Processing applied a 24-hour robust detrend, standardization, and a smoothed absolute-difference gradient change-points were detected with CUSUM and PELT, and daily cross-correlations assessed lead–lag structure. Sub-daily energy was tracked with a 6–48-hour band proxy. In 2020, magnetic change-points preceded the main MLv 3.4 earthquake by approximately 58–60 hours in 2022, they preceded the MLv 5.6 event by about 110 hours. Both episodes showed positive-lag correlation peaks, consistent with magnetometric variability leading seismic counts by days rather than minutes. Findings support low-cost, LoRa-enabled magnetometry as a complementary surveillance tool and motivate expansion the magnetometrics systems into volcanoes.

Keywords: Geomagnetic monitoring, Seismic precursors, LoRa communications, Cross-correlation, Change-point detection, Chiles-Cerro Negro.

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