Report on Loihi (United States) — December 2012
Bulletin of the Global Volcanism Network, vol. 37, no. 12 (December 2012)
Managing Editor: Richard Wunderman.
Loihi (United States) Seismic swarms during 2001-2006
Please cite this report as:
Global Volcanism Program, 2012. Report on Loihi (United States) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 37:12. Smithsonian Institution.
18.92°N, 155.27°W; summit elev. -975 m
All times are local (unless otherwise noted)
Ken Rubin of the University of Hawaii provided some of the following information concerning Loihi volcano, noting that there hasn't been much activity reported over the last 10 years. The ocean bottom seismometer (OBS) died several months after installation in mid-1996 because the cable connecting it to land was not armored and thus failed early after deployment. However, using available seismic data from the OBS and the Hawaiian Volcano Observatory (HVO) land network, Caplan-Auerbach and others (2001), were able to develop a more precise crustal velocity model so that seismic events at Loihi recorded by the land stations at Kilauea can now be precisely located. Unfortunately, only large events (probably >M 3 or M 4) are detected.
Several papers were published on Loihi by Schipper and others (2010, 2011) looking at a reworked pyroclastic section of unknown age on the summit platform and making inferences on eruptive conditions (especially on the conditions of vesiculation and fragmentation). The samples for their studies were collected during the last known geological dives to the summit by Hawaii Undersea Research Laboratory (HURL) and NOAA in 2007.
Seismic swarms during 2001-2006. The Loihi web site reported that a seismic swarm was detected at Loihi's summit with earthquakes up to M 5.2 on 13 September 2001. Activity continued for a couple of weeks, with 4 events >M 4 at depths of 12-13 km. No >M 4 earthquakes were detected at Loihi during 2002-2004. An M 4.3 earthquake occurred on 23 April 2005 at ~33 km depth beneath Loihi, and earthquakes of M 5.1 and 5.4 occurred on 13 May and 17 July 2005, respectively, both at a depth of 44 km. The U.S. Geological Survey Advanced National Seismic System measured a small swarm of about 100 earthquakes (the largest 3 events were ~M 4, and between 12 and 28 km deep) that occurred beneath Loihi on 7 December 2005. A more recent earthquake (estimated M 4.7) occurred on 18 January 2006, roughly midway between Loihi and Pahala (on the S coast of the island of Hawaii).
References. Caplan-Auerbach, J., and Duennebier, F.K., 2001, Seismicity and Velocity Structure of Loihi Seamount from the 1996 Earthquake Swarm, Bulletin of the Seismological Society of America, v. 91, no. 2, p. 178-190.
Rubin, K.H., Soule, S.A., Chadwick Jr., W.W., Fornari, D.J., Clague, D.A., Embley, R.W., Baker, E.T., Perfit, M.R., Caress, D.W., and Dziak, R.P., 2012, Volcanic eruptions in the deep sea, Oceanography, v. 25, no. 1, p. 142-157.
Schipper, C.I., White, J.D.L., and Houghton, B.F., 2010, Syn- and post-fragmentation textures in submarine pyroclasts from Lo`ihi Seamount, Hawai`i, Journal of Volcanology and Geothermal Research, v. 191, issues 3-4, p. 93-106.
Schipper, C.I., White, J.D.L., and Houghton, B.F., 2011, Textural, geochemical, and volatile evidence for a Strombolian-like eruption sequence at Lo`ihi Seamount, Hawai`i, Journal of Volcanology and Geothermal Research, v. 207, issues 1-2, p. 16-32.
Geologic Background. Loihi seamount, the youngest volcano of the Hawaiian chain, lies about 35 km off the SE coast of the island of Hawaii. Loihi (which is the Hawaiian word for "long") has an elongated morphology dominated by two curving rift zones extending north and south of the summit. The summit region contains a caldera about 3 x 4 km wide and is dotted with numerous lava cones, the highest of which is about 975 m below the sea surface. The summit platform includes two well-defined pit craters, sediment-free glassy lava, and low-temperature hydrothermal venting. An arcuate chain of small cones on the western edge of the summit extends north and south of the pit craters and merges into the crests prominent rift zones. Deep and shallow seismicity indicate a magmatic plumbing system distinct from that of Kilauea. During 1996 a new pit crater was formed at the summit, and lava flows were erupted. Continued volcanism is expected to eventually build a new island; time estimates for the summit to reach the sea surface range from roughly 10,000 to 100,000 years.
Information Contacts: Lo`ihi Volcano website (URL: http://www.soest.hawaii.edu/GG/HCV/loihi.html); Ken Rubin, Department of Geology and Geophysics, School of Ocean and Earth Science and Technology (SOEST), University of Hawaii at Manoa, Honolulu, HI (URL: http://www/soest.hawaii.edu/GG); U.S. Geological Survey Earthquake Information Center (NEIC) (URL: https://earthquake.usgs.gov/neis); Hawaiian Volcano Observatory (HVO), U.S. Geological Survey, PO Box 51, Hawaii National Park, HI 96718, USA (URL: https://volcanoes.usgs.gov/observatories/hvo/).