Analysis of possible generating sources of “tornillo”-type seismic events at Puracé Volcano, Colombia
DOI:
https://doi.org/10.32685/0120-1425/boletingeo.44.2018.34Keywords:
Q resonator, complex frequencies, tornillos, Puracé volcano, Sompi method
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Abstract
In the Puracé volcano, a study of the “tornillo” seismic event was conducted for the period between 2000 and 2012. To characterize the generation source and the nature of the fluids that interact in the internal cracks of the Puracé volcano, the Q factor of the resonator and the dominant frequencies were calculated using the Sompi method. It was found that the Q factor of the resonator values varied between 100 and 400 on average and that in some periods (2010), the Q of the resonator reached values up to 1200. The dominant frequencies presented different ranges (1.5-13 Hz), with a predominant average of 6 Hz. It was possible to observe temporal variations in both the Q factor of the resonator and the complex frequency, which could be associated with changes in the content of the fluid, from a more gaseous fluid to a mixture of gas and particulate material (mineralized sulfur), and to changes in the sizes of the cracks from 30 to 50 m, which are estimated to be located at a depth between 300 and 900 m from the bottom of the crater. We propose a conceptual model in which the fluid that generates the tornillo events is associated with the magmatic activity of the Puracé volcano, which releases gas pulses that interact with the hydrothermal system and with superficial layers of mineralized zones with native sulfur, which in turn is mixed with the gas from the magma, both causing the occurrence of tornillo-type seismicity events and the temporal variations they present in the values of the Q factor of the resonator and the dominant frequencies.
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