Chemical changes in spring waters at Tacaná volcano, Chiapas, Mexico: A possible precursor of the May 1986 seismic crisis and phreatic explosion |
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| Authors: | S de la Cruz-Reyna MA Armienta V Zamora F Jurez |
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| Institution: | S. de la Cruz-Reyna, M.A. Armienta, V. Zamora,F. Juárez |
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| Abstract: | Local seismic activity consisting of sharp earthquakes accompanied by thunderous noise was reported starting in late December 1985 around Tacaná volcano (15.13°N, 92.10°W). Portable seismic stations were established in the area by late January 1986 and sampling of the only known thermal spring on the volcano flanks started at the same time. A marked increase in SO42− concentration in the spring water preceded by two months the occurrence of a seismic swarm crisis and a small phreatic explosion. A model involving a crystalline basement fractured by tectonic stresses is proposed to explain the chemical and seismic anomalies, and the consequences on risk of volcanic activity are briefly discussed in terms of the observed behaviour. |
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