Tectonic stress field and fractal distribution of volcanoes in the Michoacan-Guanajuato region of the Mexican Volcanic Belt

Abstract

From the orientation of normal faults and the alignment of volcanoes, the tectonic stress field of the Michoacan Guanajuato volcanic field was estimated. The maximum compressional principal stress σ₁ is vertical throughout the region and σ₂ trends E-W in the northern area and NE-SW in the southern area. The origin of the stress field is attributed to the trench ward slipping of the arc sliver on the brittle/ductile boundary surface induced by the rollback of the Middle America trench axis. This is related to the subduction rate of the Cocos plate which is slower than the critical rate of 7.2 cm/y.~~The spatial distribution of volcanic centers, and the volume of volcanic bodies, are fractal; the fractal dimensions are J,63 arid 1.44 respectively. The fractality and the large values of the fractal dimension are explained by an analogy to viscous fingering or invasion percolation in porous media which is an effect of the crustal stress profile of the tensional stress field.