Magmatic activity at the slowest spreading rates: insights from a high-resolution earthquake catalog obtained from Gakkel Ridge Deep (Arctic Ocean)

At the eastern end of Gakkel Ridge, Arctic Ocean, spreading rates drop below 5 mm/y near the termination of the active mid-ocean ridge in the Laptev Sea. A small-scale ocean bottom seismometer network deployed for one year at a volcanic center near Gakkel Ridge Deep in sea ice covered waters revealed abundant microseismicity despite the low spreading rate. In order to reveal spreading processes, we analyze a manually picked earthquake catalog refined by low-magnitude events detected by template matching. We attribute seismicity occurring randomly in time and space to tectonic stress release along the ridge. During short time periods of hours to days, seismicity is organized in time and densely clustered in space with signs of migration away from an aseismic area. In analogy to volcanic centers at Knipovich Ridge and in Iceland, we interpret the seismicity as signs of ongoing localized magmatism occurring even at the slowest spreading rates.