TY - JOUR

T1 - The trigger mechanism of low-frequency earthquakes on Montserrat.

AU - Neuberg, Juergen W

AU - Tuffen, Hugh

AU - Collier, Lindsey

AU - Green, David

AU - Powell, Tanya

AU - Dingwell, Donald B

PY - 2006

Y1 - 2006

N2 - A careful analysis of low-frequency seismic events on Soufrie`ere Hills volcano, Montserrat, points to a source mechanism that is non-destructive, repetitive, and has a stationary source location. By combining these seismological clues with new field evidence and numerical magma flow modelling, we propose a seismic trigger model which is based on brittle failure of magma in the glass transition. Loss of heat and gas from the magma results in a strong viscosity gradient across a dyke or conduit. This leads to a buildup of shear stress near the conduit wall where magma can rupture in a brittle manner, as field evidence from a rhyolitic dyke demonstrates. This brittle failure provides seismic energy, the majority of which is trapped in the conduit or dyke forming the lowfrequency coda of the observed seismic signal. The trigger source location marks the transition from ductile conduit flow to friction-controlled magma ascent. As the trigger mechanism is governed by the depth-dependent magma parameters, the source location remains fixed at a depth where the conditions allow brittle failure. This is reflected in the fixed seismic source locations.

AB - A careful analysis of low-frequency seismic events on Soufrie`ere Hills volcano, Montserrat, points to a source mechanism that is non-destructive, repetitive, and has a stationary source location. By combining these seismological clues with new field evidence and numerical magma flow modelling, we propose a seismic trigger model which is based on brittle failure of magma in the glass transition. Loss of heat and gas from the magma results in a strong viscosity gradient across a dyke or conduit. This leads to a buildup of shear stress near the conduit wall where magma can rupture in a brittle manner, as field evidence from a rhyolitic dyke demonstrates. This brittle failure provides seismic energy, the majority of which is trapped in the conduit or dyke forming the lowfrequency coda of the observed seismic signal. The trigger source location marks the transition from ductile conduit flow to friction-controlled magma ascent. As the trigger mechanism is governed by the depth-dependent magma parameters, the source location remains fixed at a depth where the conditions allow brittle failure. This is reflected in the fixed seismic source locations.

KW - Monserrat Volcanic Earthquake Trigger Magma Conduit Dome Lava Andesite Andesitic Soufriere Hills Tuffen Rupture Fracture Model Maxwell unrelaxed deformation glass transition shear pressure seismic seismicity volcano-seismicity brittle failure swarm swarms

U2 - 10.1016/j.jvolgeores.2005.08.008

DO - 10.1016/j.jvolgeores.2005.08.008

M3 - Journal article

VL - 153

SP - 37

EP - 50

JO - Journal of Volcanology and Geothermal Research

JF - Journal of Volcanology and Geothermal Research

SN - 0377-0273

ER -