Regional stress influence on the opening direction of crater amphitheaters in Southeast Asian volcanoes

Holocene volcanoes in the Philippines and Indonesia were studied to determine the possible relationship between the regional maximum horizontal stress (σHmax) and the opening direction of volcanic amphitheatre craters. The study was conducted using publicly available Shuttle Radar Topographic Mission (SRTM) images and the World Stress Map (WSM). The results corroborate findings in similar research on Japanese and Indonesian volcanoes indicating that opening of craters occur at an acute angle relative to the σHmax direction. Further investigation of volcanoes in Southwest and Southeast Luzon, Philippines, regions where fault structures and their kinematics are better constrained, reveal a promising tectonic stress-related rationale for crater opening direction. Several volcanoes in these regions of the Philippines appear to have amphitheatre craters open in the direction related to the fault underlying the volcano. These observations are consistent with those derived from analogue models of volcanic cones deformed by basal strike-slip faulting. These findings can be useful in advancing our understanding of volcanic flank failure and for hazards preparedness against such catastrophic events.