Three‐dimensional computational axial tomography scan of a volcano with cosmic ray muon radiography

Abstract

Cosmic ray muon radiography can measure the density distribution within a volcano. Unidirectional radiography shows a precise cross‐sectional view of a conduit and a magma body through a volcano parallel to the plane of the detector. However, it only resolves the average density distribution along individual muon paths. Precise size and shape of underground structure, such as a conduit or a magma body, provide clear and pervasive information on understanding dynamics of volcanic eruption. Here we show a highly resolved three‐dimensional tomographic image of an active volcano Asama in Japan. Specifically, we developed a portable power‐effective muon radiography telescope that can be operated stable with a realistically sized solar panel so as to place it around an active volcano where commercial electric power is not available. The resulting image below the crater floor shows that a local low‐density region accumulates sufficient gas pressure to cause Vulcanian eruption. The present muon computational axial tomography scan has a resolving power with a resolution of 100 m, allowing it to see great detail in volcanoes.