Abstract
MONITORING of gravity changes at active volcanoes has considerable potential for understanding magma-chamber dynamics and for detecting eruptive precursors. The technique essentially aims to identify changes in sub-surface mass or density corresponding to departures from the free-air gradient (FAG) or Bouguer-corrected (terrain-corrected) FAG (BCFAG), respectively1,2. Such gravity changes, of the order of 10–100 µgal, have been reported previously through eruptive periods3–6. Here we present a ten-year data set measured at Poás volcano, Costa Rica, in which gravity increases in 1987–1989, relative to both the FAG and the BCFAG, preceded the ash-cloud eruptions of April–May 1989. These results constitute the first unambiguous detection of gravity changes as a precursor to eruption, and we interpret them in terms of the intrusion of an ascending, relatively dense magma body.
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Rymer, H., Brown, G. Gravity changes as a precursor to volcanic eruption at Poás volcano, Costa Rica. Nature 342, 902–905 (1989). https://doi.org/10.1038/342902a0
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DOI: https://doi.org/10.1038/342902a0
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