Focal mechanism analysis of volcano-tectonic seismic events in Galeras Volcano, Colombia, with manual and computational methods.
DOI:
https://doi.org/10.32685/0120-1425/bol.geol.50.2.2023.700Keywords:
Galeras volcano, volcano-tectonic earthquakes, focal mechanisms, tectonic-magmatic system, cumulative misfit method, stress field.
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Copyright (c) 2023 Servicio Geológico Colombiano
This work is licensed under a Creative Commons Attribution 4.0 International License.
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Abstract
Focal mechanism solutions of 120 volcano-tectonic earthquakes (VT) were calculated at the Galeras Volcanic Complex (CVG) during 2005 - 2018, using as input data the hypocenter location, azimuth, take-off angles and polarities of the catalog of events compiled by the monitoring network at the Colombian Geological Service, Volcanological and Seismological Observatory of Pasto (SGC-OVSP). Manual and computational solutions were determined. The manual solutions were plotted with the Stereonet program, and computational solutions with the HASH software. Strike (φ) and dip (δ) data obtained by each method were compared to calculate the misfits between both approaches for (φ) and (δ); moreover, comparisons were made between the manual solutions and theoretical data from previous studies, of the strike (φ) and dip (δ) of the Buesaco fault. The misfits revealed spatial and temporal variations in the stress state of the tectonic-magmatic system of the Galeras volcano (VG), integrating with geological and structural information. In particular, it is concluded that there are differences in the state of stresses with respect to time and depth under the VG between 3 km and 6 km, variations are also detected in the area surrounding the volcano defined for the distance according to latitude coordinates between 1º-12.94' and 1º-14.70' and longitude between 77º-20.73' and 77º-18.16', and differences in the state of stress measured along the Buesaco fault, mainly along the NE segment.
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