Characteristics and causes of shallow seismicity in andesite volcanoes
Journal - Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
Recent observations from Soufriere Hills volcano in Montserratreveal a wide variety of seismic signals. We focus here on characteristicsof long-period events, and their role in the pressurizationof the volcanic plumbing system. These events can occur in swarmsand merge into tremor, an observation that sheds further lighton the generation and composition of harmonic tremor. A two-dimensionalfinite-difference method has been employed to model major featuresof low-frequency seismic signatures and compare them with theobservations. A depth-dependent seismic velocity model for afluid-filled conduit is used that accounts for the varying gascontent in the magma. We analyse episodes of tremor that showshifting spectral lines and model those in terms of changesin excess pressure due to unloading and degassing events. Potentialtrigger mechanisms are suggested and discussed.
|Keywords : ||conduit resonance • tremor • long-period earthquake • pressurization|