HR: 0830h
AN: V51J-0407    [PDF]
TI: Borehole Strainmeters on Montserrat: the CALIPSO Project and the July 2003 Eruption.
AU: * Linde, A
EM: linde@dtm.ciw.edu
AF: Carnegie Institution of Washington, Department of Terrestrial Magnetism, 5241 Broad Branch Road, N.W., Washington, DC 20015 United States
AU: Sacks, S I
EM: sacks@dtm.ciw.edu
AF: Carnegie Institution of Washington, Department of Terrestrial Magnetism, 5241 Broad Branch Road, N.W., Washington, DC 20015 United States
AU: Voight, B
EM: bxv1@psu.edu
AF: Pennsylvania State University, Department of Geosciences, Deike Building, University Park, PA 16802 United States
AU: Malin, P
EM: malin@duke.edu
AF: Duke University, Box 90235, 109 Old Chemistry, Durham, NC 27708 United States
AU: Shalev, E
EM: shalev@duke.edu
AF: Duke University, Box 90235, 109 Old Chemistry, Durham, NC 27708 United States
AU: Mattioli, G S
AF: University of Arkansas, Department of Geosciences, 113 Ozark Hall, Fayettville, AR 72701 United States
AU: Young, S R
EM: sry2@psu.edu
AF: Pennsylvania State University, Department of Geosciences, Deike Building, University Park, PA 16802 United States
AB: During November 2002 to February 2003, 4 borehole sites were established on Montserrat in order to provide data to investigate the on-going eruption of Soufriere Hills as part of the multi-institutional CALIPSO project that also included participation by the Monserrat Volcano Observatory. In the boreholes we installed a Sacks-Evertson strainmeter, a short period 3 component seismometer and a tiltmeter. Each site also included a GPS receiver. At one site, we installed for the first time a modified S-E strainmeter that is designed for long term operation under conditions of high temperature and high pressure. Straingrams of earthquakes indicate that all instruments were operating well. The dome building andesitic volcano has been active since before 1995 although the level of activity has been highly variable. Much of the island, including the capital Plymouth, has been devastated by pyroclastic and mud flows. A period of relative quiescence was interrupted last year as the dome built to greater heights than at any time during the activity since 1996. This dome growth continued until July 13, 2003 when the largest dome collapse took place. Three borehole strainmeters were operational during that activity and have provided excellent data associated with the collapse. Preliminary inspection of the data show that a dominant feature is a very long period (~300 sec) tremor-like signal that began about 5 hours before the eruption. The amplitude of the signal generally increased with time, becoming a maximum about the time of the collapse and continued until well after the main collapse. This long period signal is also corresponds well with the short period amplitude signals recorded by the seismometers. The long period signals are presumably related to processes that provided the final contribution to the collapse. Additionally the strain records include much longer period disturbances that may provide constraints on the magma supply process.
DE: 8194 Instruments and techniques
DE: 8414 Eruption mechanisms
DE: 8419 Eruption monitoring (7280)
DE: 8429 Lava rheology and morphology
DE: 8434 Magma migration
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting