Location and source mechanism of sound signals at Gakkel ridge, Arctic Ocean: Submarine Strombolian activity in the 1999–2001 volcanic episode

Abstract

[1] Gakkel ridge is the slowest spreading mid-ocean ridge with full spreading rates <10 mm/yr. In 1999, a teleseismic earthquake swarm signaled the onset of an eruptive episode at 85°E. The Arctic Mid-Ocean Ridge expedition in 2001 detected a hydrothermal event plume and explosive seismoacoustic signals. In 2007, the Arctic Gakkel Vents Expedition found direct evidence for recent submarine explosive activity on the seafloor at $4000 m. The newest data motivated a reassessment of the seismoacoustic events of 2001. We undertake 2-D finite difference wavefield modeling to relocate the source of the signals and investigate the possible source mechanism; the explosion sounds likely result from submarine Strombolian eruptions with bursting gas bubbles rising from a magma reservoir along a major fault at the southern rift valley wall.

Effusive and explosive volcanism on the ultraslow‐spreading Gakkel Ridge, 85°E

“…Geophysical surveys of the 85°E segment from a nuclear submarine (SCICEX expedition) following the onset of the swarm (summer of 1999) imaged a large region of high acoustic backscatter covering the entire axial valley (Figure 3), which was interpreted to represent multiple unsedimented, voluminous lava flows [ Edwards et al , 2001]. The AMORE expedition, which returned to the 85°E site in 2001, found evidence for a hydrothermal ‘megaplume’ in the water column over the axial valley [ Edmonds et al , 2003] and seismometers deployed on ice floes over the site recorded explosive reports interpreted to represent ongoing volcanic activity [ Schlindwein et al , 2007; Schlindwein and Riedel , 2010]. All of this evidence led to the hypothesis that the 85°E segment has been undergoing a phase of active volcanism wherein it has produced frequent and voluminous lava flows and vigorous, sustained, hydrothermal discharge [ Müller and Jokat , 2000; Edwards et al , 2001; Tolstoy et al , 2001; Edmonds et al , 2003; Baker et al , 2004].…”

Seismic Arrays on Drifting Ice Floes: Experiences from Four Deployments in the Arctic Ocean

“…The deployment yielded new results about the seismic activity of Gakkel Ridge . At the 85°E volcanic complex, the seismometers showed an astonishing in-situ record of sounds of an ongoing submarine volcanic eruption (Schlindwein et al 2005;Schlindwein and Riedel 2010). Furthermore, this experiment proved that low-magnitude local seismicity can be recorded with sensors deployed on drifting ice floes.…”

Deep explosive volcanism on the Gakkel Ridge and seismological constraints on shallow recharge at TAG active mound

“…The 2001 AMORE expedition returned to the study area to conduct dredging and water column surveys. The most 13 vigorous hydrothermal venting detected along the ridge was found in the same location (85°E) where a 1400 m thick megaplume was observed .Seismoacousitic arrays recorded numerous microearthquakes (average magnitude = -0.33) during the 2001 AMORE study that are proposed to have been magmatic in origin [Schlindwein et al, 2007;Schlindwein and Riedel, 2010]. From this evidence, it was hypothesized that the 85°E segment is a hydrothermally and volcanically active area that experienced eruption in 1999.…”

“…Seismoacousitic arrays recorded numerous microearthquakes (average magnitude = -0.33) during the 2001 AMORE study that are proposed to have been magmatic in origin [Schlindwein et al, 2007;Schlindwein and Riedel, 2010]. From this evidence, it was hypothesized that the 85°E segment is a hydrothermally and volcanically active area that experienced eruption in 1999.…”