Observations of submarine volcanism from 25 years of global hydrophone deployments

Abstract:

For over two decades the NOAA/PMEL Acoustics Program has been using hydroacoustic methods to detect, locate and characterize submarine volcanism. Access to NE Pacific cabled hydrophone arrays in the early 1990s provided impetus for in-house development of a portable hydrophone mooring system that has enabled remote deployment and detection of volcanism throughout the world’s ocean basins. Our hydrophone systems have detected volcano-acoustic signals from diverse geographic locations and tectonic settings. This includes slow to fast spreading mid-ocean ridges, e.g. East Pacific Rise, mid-Atlantic, Juan de Fuca and Indian Ridges, as well as ridge-axis hotspots such as Axial Seamount (Pacific), Reykjanes Rift and Lucky Strike Seamount (Atlantic), Walvis Ridge (s. Atlantic) and Amsterdam plateau (Indian). Intense seismo-acoustic activity and degassing explosions have been recorded at island arcs and back-arcs, including NW-Rota-1 and Anatahan in the Marianas, Fukutoku-Okanoba (Volcano Isles), and West Mata, Hunga Ha’apai in the Tonga arc. Brothers volcano (Kermadec arc) has exhibited ongoing volcanic tremor, while the Bransfield back-arc (Antarctica) underwent a seafloor spreading event. The character of the volcano-acoustic signals recorded varies with the style of submarine volcanism. For example, mid-ocean ridge (MOR) intrusions are detected by high rates of low magnitude seismicity (with a few large teleseismic “mainshocks”) that can last several weeks. These MOR intrusions typically exhibit migration of earthquake locations tracking the injection of magma 10s of kms down-rift. Recent in situ records of MOR-hotspot volcanism show intense seismicity, tremor and explosions caused by degassing of seafloor lava flows. Arc volcanoes have been observed to produce repeated, violent degassing explosions at the summit eruption vent, as well as broad-band (<100 Hz) volcanic tremor (with fundamentals and overtones) caused by magma flow within the volcanic edifice. This research was made possible by collaboration with several Government and University organizations: OSU, UO, LDEO, NCSU, UW, UH, WHOI, WWU, U-Brest-France; PMEL-EOI, USCG, US-NSF (OOI), KORDI, and KOPRI.