The 2023 eruption of Nyamulagira volcano (DR Congo) began on May 19 with lava overflowing from the summit crater. We analyze seismic data from two nearby stations (RGB2 and RSY2) to investigate the precursory signals leading up to the eruption. Our results show a clear and gradual increase in RSAM (Real-time Seismic Amplitude Measurement) starting around 10 days before, followed by a seismic swarm from May 18 to early May 19. Correlation analyses reveal a weak relationship between RSAM and the number of daily volcanic events, suggesting distinct physical processes: RSAM is sensitive to continuous tremors linked to magma ascent, whereas event counts reflect brittle fracturing. Despite moderate correlation between RSAM values at both stations, local effects may influence amplitude differently. We conclude that RSAM trends, especially progressive increases followed by swarms, may serve as reliable early indicators of eruptive activity, even in the absence of detectable surface deformation.
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