OS43A-2015
Deformation associated with the 2015 Eruption of Axial Seamount

Thursday, 17 December 2015
Poster Hall (Moscone South)
Scott L Nooner1, William Chadwick2, David W Caress3, David A Clague3, Jennifer Brophy Paduan3, Dana Yoerger4 and Glenn S Sasagawa5, (1)University of North Carolina at Wilmington, Wilmington, NC, United States, (2)Oregon State University/NOAA/PMEL, Newport, OR, United States, (3)Monterey Bay Aquarium Research Institute, Watsonville, CA, United States, (4)Woods Hole Oceanographic Inst., Woods Hole, MA, United States, (5)University of California San Diego, La Jolla, CA, United States
Abstract:
On April 24th 2015, an eruption began at Axial Seamount, a seafloor volcano located about 480 km west of the Oregon coast at the intersection of the Cobb hotspot and the Juan de Fuca Ridge. This eruption was first detected in real time by the newly operational Ocean Observatories Initiative cabled instrumentation at Axial (Delaney, AGU-2015, Wilcock, AGU-2015, Caplan-Auerbach, AGU-2015). Two prior eruptions have been observed since routine observations began in the 1990’s, one in January 1998 and the other in April 2011.

Precise water pressure measurements made on the volcano have documented an inflation/deflation cycle within Axial’s summit caldera for the past 15 years. These data are now being supplemented by repeat bathymetric mapping by AUV. The long-term pattern appears to be “inflation predictable”, in which eruptions are triggered at or near the same level of inflation. This pattern allowed us to successfully forecast in September 2014 that the next eruption was expected to occur at Axial sometime in 2015 (a 1-year time window). It is noteworthy that the rate of inflation between the 2011 and 2015 eruptions was about 4 times higher than between the 1998 and 2011 eruptions (60 cm/yr vs. 15 cm/yr).

Subsidence at the caldera center began at 06:00 on 24 April (all times GMT) and amounted to 2.2 m by 02:00 on 25 April (20 hours in), 2.4 m by 00:00 on 28 April, and 2.45 m by 05 May when subsidence ended and re-inflation began (which has continued ever since). This amount of subsidence is similar to that observed during the 2011 eruption, but in 2015 the initial rate of subsidence was higher (11 cm/hr during the first 20 hours vs. 7 cm/hr in 2011) and the duration appears to have been longer (11 days vs. 6 days). Also, the 1998 and 2011 eruptions occurred along the southeastern edge of the caldera and along Axial’s south rift zone, whereas the 2015 eruption occurred along the north rift zone (Kelley, AGU-2015). Here we present preliminary results of our August 2015 post-eruption geodetic survey and response cruise. In 2013 we increased our network of geodetic stations at Axial, which will provide us with more resolution in modeling the movement of magma associated with the eruption and subsequent recharge. We will also present preliminary maps of the new lava flows.

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