| Abstrak/Abstract |
Stress fields in the Earth's crust are important indicators leading to better understanding of geologic processes. One way to acquire stress data is through morphometric analysis of volcanoes. Here we evaluate 141 Quaternary-age monogenetic and polygenetic volcanoes and volcanic fields in Java, Indonesia, using a 30-m SRTM DEM, a 8-m DEMNAS, aerial photos, published geological maps, and Landsat and Google Earth satellite imagery. We analyze parameters that imply the geometry of the shallow magma plumbing system and ascent pathways: crater ellipticity and elongation axis, and the orientation of crater-breaching bisectors. The dominant trend of all of these parameters should indicate the direction of the maximum horizontal compressive stress (?Hmax) while the minimum horizontal stress (?Hmin) should be perpendicular to it. The goal here is to estimate the principal stress axes at the time of dike emplacement, to recognize any spatial variations in stress orientations, and assess factors controlling the emplacement. The resulting orientation of ?Hmax in the western part of Java is NE-SW, and the trend gradually rotates to NW-SE moving eastward. Abrupt changes in stress orientations and anomalies are also observed in the vicinity of prominent geologic structures, highlighting the influence of preexisting structures on dike emplacement and eruption characteristics. Results of the morphometric analysis of volcanoes and volcanic fields conducted in this study help to estimate the past and present stress orientations in Java, and provide valuable understanding regarding the relationship between volcanic emplacement and crustal structures, complementing other types of analysis. |
