Inferring magma-feeding fracture geometry through morphological analysis: A volcanotectonic study of Hat Creek Graben, California

Volcano–tectonic processes in extensional settings influence dike emplacement and vent morphology. In this study, we analyze volcanic vents and tectonic structures in the Hat Creek Graben (HCGR), northern California, using drone-based digital terrain models (DTMs) and digital elevation models (DEMs). These datasets enable high-resolution mapping of vent geometry, lava flows, and fault scarps. Two distinct magma types—low-potassium olivine tholeiitic basalt (LKOT) and calc-alkaline basaltic andesite (CAB)—occur in close spatial and temporal proximity within the graben. We compare vent morphology and orientations to evaluate the influence of magma viscosity and tectonic stress. Results show that low-viscosity LKOT dikes tend to erupt within the graben, forming low-relief cones and en-echelon vent patterns, whereas higher-viscosity CAB dikes often deflect toward fault scarps, forming steeper cones. We interpret that viscosity, in combination with local stress fields and topography, controls dike propagation and vent localization. These findings suggest that vent distribution and morphology can be partly forecasted using knowledge of magma rheology and the regional tectonic framework.