Seismicity of the Lazufre Volcanic System, Northern Chile/Argentina

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Cordon del Azufre and Lastarria are two volcanoes on the border of Chile and Argentina that have been shown to have an unusual deformation signature. The main center of deformation is between the two volcanoes, with the top of the modelled deformation source at a depth of 7-15 km. A smaller deformation signal is near the summit of Lastarria, with a deformation source at ~1 km below the surface. The most recent eruptions at these volcanoes occurred ~150 ka at Lastarria, and ~0.3 Ma at Cordon del Azufre. Current geologic activity, which is not centered on just the volcanoes, but also in between the two, consists of fumarolic activity, seismic activity, and degassing with a possible change in gas composition between 2009 and 2012 that may be indicative of a change from a hydrothermal to a magmatic nature. The PLUTONS Project deployed 8 seismic stations around the Lazufre complex from November 2011 to March 2013. Preliminary results from analyzing the seismic activity show an average of 1 autodetected event per day within a 20 km radius of Lazufre with the majority of depths less than 10 km below sea level. The average magnitude is ML~1, and does not exceed ML = 2.8. The b-value for these events is ~1.03 ± 0.08 (a typical tectonic value), with a magnitude of completeness threshold Mc = 0.3. The peak event rate is 17 events per day in the beginning of May 2012. These results suggest moderately high volcanic and/or hydrothermal activity at the Lazufre Volcanic complex, with most events occurring beneath the summit of Lastarria.

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Presented at the Seismological Society of America Annual Meeting on May 15, 2018 in Miami, FL