资源环境科技发展态势分析平台

This study details a case of transition of volcanic activity between two closely spaced (20-40 m) vents within the southern crater of Yasur Volcano, Vanuatu, over a period of 12 days. The transition from one vent to another newly emerged one was captured by a multi-instrument array, with broadband seismic, thermal-IR camera, and visual recordings presented. The results describe systematic changes in explosive parameters (e.g., style, power, and frequency) at both vents that reflect the transfer of magma and volatile gas flux within a shallow branching conduit system. The decline of activity at the initial vent corresponds with a shift from bomb-rich to ash-rich behavior indicating a progressive decrease in magma and volatile gas flux and increasing shallow conduit magma viscosity. The concurrent increase in activity at the emerging vent accompanies more bomb-rich behavior that indicates increased flux and lower magma viscosity. During the transition period, most explosions were systematically paired between the two vents, occurring within <1 to up to 45 s of each other. Broadband seismic data show that paired explosions produce a common seismic signal that resembles that of a single, nonpaired explosion. The presence of a common low-frequency (0.06-1 Hz) signal indicates that multiple shallow conduits may transmit the same gas and impulsive energy differently from a single gas rise and burst event. Temporal offsets between paired explosions reflect the different conduit pathways and viscosity states of the magma in each conduit, with the lagging vent always displaying greater ash-rich activity indicating higher magma viscosity and gas path tortuosity.