Parçalı Kaldera Çökmelerinin Analog ve Nümerik Modellemesi

Abstract

Analogue experiments are carried out to investigate the structural and tectonic evolution of volcanoes in volcanology. Analogue caldera experiments are important to examine the structural and morphological evolution of calderas. This work has been started with the main step of establishing the necessary experimental apparatus to create analogue caldera models. The formation stages of calderas were investigated by repeated sand box experiments due to the lateral expansional movement of the magma chamber. High precision surface modeling and digital elevation model of the analogue models were created by Structure from Motion - Multi-View Stereophotogrammetry (SfM-MVS) method. Particle Tracking (PT) method was used to investigate surface displacements and surface deformations on the model. Thus, the evolution of the structural elements of the piecemeal calderas on the model surface was examined in two different methods. In order to examine the internal structure of analogue caldera models, the models were fixated and scanned by X-ray tomography and X-ray Micro-CT methods, and the internal-structural elements of the fixated caldera models were investigated in three dimensions. Numerical modeling was carried out using finite element method to investigate the deformation of the lateral expansion of the magma chamber in the roof block. Stress and displacement of the roof block were investigated numerically. The results show that, an inequivalent deformation on the roof block have been formed due to the lateral expansion of the magma chamber. It was determined that during the collapse, this roof block collapsed at different depths, as two discrete blocks and separated from each other with a sub-linear structural boundary. This collapse is called as double-piston piecemeal caldera. Structural elements formed by tumescence and the following collapse of the caldera; outward-dipping reverse faults, inward-dipping normal faults, radial faults and boundary faults surrounding the caldera (ring fault) have been observed. The models were interpreted by comparing them with the calderas formed by piecemeal collapse in the nature.