Journal
GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS
Volume 23, Issue 1, Pages -Publisher
AMER GEOPHYSICAL UNION
DOI: 10.1029/2021GC010153
Keywords
submarine volcano monitoring; seafloor geodesy; eruption forecasting; bottom pressure recorders; ocean bottom seismometers; OOI cabled observatory
Categories
Funding
- National Science Foundation (NSF)
- NSF [OCE-1356839, 1736882, OCE-1634150, 1928282, OCE-1536219]
- National Oceanic and Atmospheric Administration, Pacific Marine Environmental Laboratory, Earth-Ocean Interactions Program
- Directorate For Geosciences
- Division Of Ocean Sciences [1928282] Funding Source: National Science Foundation
- Directorate For Geosciences
- Division Of Ocean Sciences [1736882] Funding Source: National Science Foundation
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Axial Seamount is a basaltic hot spot volcano located below sea level, and has experienced eruptions in 1998, 2011, and 2015. The magma supply rate has been decreasing since the last eruption in 2015, with the next eruption estimated to be 4-9 years away. Long-term monitoring data reveals significant variations in magma supply rate over different time scales.
Axial Seamount is a basaltic hot spot volcano with a summit caldera at a depth of similar to 1,500 m below sea level, superimposed on the Juan de Fuca spreading ridge, giving it a robust and continuous magma supply. Axial erupted in 1998, 2011, and 2015, and is monitored by a cabled network of instruments including bottom pressure recorders and seismometers. Since its last eruption, Axial has re-inflated to 85%-90% of its pre-eruption level. During that time, we have identified eight discrete, short-term deflation events of 1-4 cm over 1-3 weeks that occurred quasi-periodically, about every 4-6 months between August 2016 and May 2019. During each short-term deflation event, the rate of earthquakes dropped abruptly to low levels, and then did not return to higher levels until reinflation had resumed and returned near its previous high. The long-term geodetic monitoring record suggests that the rate of magma supply has varied by an order of magnitude over decadal time scales. There was a surge in magma supply between 2011 and 2015, causing those two eruptions to be closely spaced in time and the supply rate has been waning since then. This waning supply has implications for eruption forecasting and the next eruption at Axial still appears to be 4-9 years away. We also show that the number of earthquakes per unit of uplift has increased exponentially with total uplift since the 2015 eruption, a pattern consistent with a mechanical model of cumulative rock damage leading to bulk failure during magma accumulation between eruptions.
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