HR: 15:25h
AN: V12G-08    [PDF]
TI: Magma-tectonic interaction at Mauna Loa, Hawaii: Earthquake stress change influence on direction of dike propagation at rift zones
AU: * Walter, T R
EM: twalter@rsmas.miami.edu
AF: MGG-RSMAS, University of Miami 4600 Rickenbacker Cswy, Miami, FL 33149 United States
AU: Amelung, F
EM: amelung@rsmas.miami.edu
AF: MGG-RSMAS, University of Miami 4600 Rickenbacker Cswy, Miami, FL 33149 United States
AB: There is ample evidence for earthquake volcano interaction at Mauna Loa. An M 6.6 earthquake at the eastern flank of the volcano preceded the 1984 eruption. An M 6.3 earthquake at the western flank preceded the 1950 eruption. An M 7.0 earthquake at the southeastern flank of Mauna Loa preceded the 1868 eruption. Earthquake focal mechanisms suggest a cause by gravitational spreading and fault slip near the base of Mauna Loa. The eruptions that followed initiated at the summit caldera, from where the fissures propagated along the northeast rift zone NERZ (1984) or along the southwest rift zone SWRZ (1868, 1950). Using three-dimensional boundary element models we calculate stress changes associated with earthquakes larger than magnitude 6. The earthquakes caused a decrease of Coulomb stress at the magma chamber, probably triggering the eruption. Moreover, the patterns of extensional normal stress for the rift zones coincide with the locations of the eruptive fissures (SWRZ or NERZ) at Mauna Loa. This suggests that the propagation of dikes is controlled by the change in stress related to gravitational spreading earthquakes.
DE: 8400 VOLCANOLOGY
DE: 8414 Eruption mechanisms
DE: 8434 Magma migration
DE: 8499 General or miscellaneous
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting