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Master's Thesis: Numerical Modelling of Explosion Signals at Santiaguito Volcano, Guatemala

Master's Thesis: Numerical Modelling of Explosion Signals at Santiaguito Volcano, Guatemala
sws:

29.10.2019

Referent:

Alicia Rohnacher (GPI)

This presentation will be given in english!

 

The activity of Santiaguito volcano dome complex with its active crater El Caliente is currently described by small, gas-rich explosions, effusive lava flow and dome growth. Rapid changes of the explosive behaviour have been reported in the past (e.g. 2015/2016) and emphasize the importance of a good understanding of the volcano, due to its proximity to major population centres. Here, we focus on the explosions accompanied by ash and gas rise at the crater centre to develop a better physical understanding of the source characteristics. Data of a permanent network established in 2018 with two Trillium Compact (120s) and two LE-3Dlite (1Hz) seismometers are used. In January 2019 a seismo-acoustic antenna with nine LE-3Dlite and five infrasound sensors were deployed for eight days. Additional three LE-3Dlite seismometers were installed to densify a NW-SE profile covering distances of 0.5-7.5km to the crater. Observations at stations within a distance of 4.5km to the crater show a seismic signal preceding the main explosion pulse. Using array analysis a slowness of 0.1-0.2 s/km is determined for precursor and main pulse onset.
Various source parameters and velocity models are tested with spectral element modelling (SPECFEM2D) and the comparison of simulated and measured data reveal important information about the source mechanism and subsurface model. It was seen that the main signal shows similarities with synthetics of a shallow vertical single force. The particle motion of the precursor indicate a deeper (200-600m) source related to an explosion or the formation of tensile cracks.