Mayon volcano, Philippines: some insights into stress balance

Mayon volcano is part of the Bicol Volcanic Chain, a peninsula in the south-east of Luzon Island. Mayonʹs eruptive history during this century is fairly periodic with eruptions nearly every 10 years. During the last two eruptions, indications for tidal triggering of activities were found. From statistical analyses, hints for such a correlation exist for a number of volcanoes. The statistical analysis of the seismicity points to a tidal triggering at Mayon volcano. er to verify these indications, the pressure balance between internal and external forces was computed. The computations show that an interrelation between volcanic activities and tides, especially ocean loading, is probable. For this purpose, a global ocean model is improved by a regional model and a model of the local areas in order to consider the tidal distribution and the complicated geometry of the coasts. The method of Farrell, W.E. [1972. Deformation of the earth by surface loads. Rev. Geophys. Space Physics 10, 761–797] is used to calculate the ocean tidal loading. essure increase in the vent due to vesiculation was tentatively modelled assumed a temperature decrease of 2°C per year. The resulting stress is compared to the stress produced by the tidal forces (body tides and ocean tidal loading). It turns out that during a period of several days the small tidal forces may affect the stress balance considerably if the volcano is already in a critical state. FE-modelling we estimate—by neglecting all external forces—how fast pressure can build up in the vent and to which extent the different physical parameters influence the pressure increase. The maximum pressure resulting from the crystallization of the melt is compared with the maximum pressure yielding when in addition tidal forces are acting.