Abstract
Muography is a novel method to highly resolve the internal structure of active volcanoes by taking advantage of the cosmic muon’s strong penetration power. In this paper, we present the first high-definition image in the vicinity of craters of an erupting volcano called Sakurajima, Kyushu, Japan. The muography observation system based on the technique of multi-wire proportional chamber (mMOS) has been operated reliably during the data taking period of 157 days. The mMOS measured precisely the flux of muons up to the thickness of 5,000 meter-water-equivalent. It was shown that high-definition density maps around the Craters A, B and Showa could be determined with a precision of less than 7.5 × 7.5 m2 which earlier had not yet been achieved. The observed density distribution suggests that the fall back deposits filled the magma pathway and increased their density underneath Craters A and B.
Highlights
Accurate measurements of the size and shape of the uppermost part of a given volcanic conduit provides useful information to us, in particular for modeling eruption dynamics; there is a large number of studies on shallow conduit flow processes and resultant lava dome behavior[1,2,3]
We developed a high definition muography observation system for practical volcano monitoring based on the scintillator-based Muography Observation System that successfully imaged the sequential magma movement in Satsuma-Iwojima volcano[10]
The MWPC-based Muography Observation System (mMOS) was installed at the Sakurajima volcano, Kyushu, Japan
Summary
Accurate measurements of the size and shape of the uppermost part of a given volcanic conduit provides useful information to us, in particular for modeling eruption dynamics; there is a large number of studies on shallow conduit flow processes and resultant lava dome behavior[1,2,3]. Higher resolution muography systems may be developed using gaseous detectors with improved resolution or using nuclear emulsions For the former, one needs to consider using non-flammable gas mixtures for implementation of long term standalone field operation. E. nuclear emulsion, has the potential to create a high resolution image (better than 10 mrad) This technique cannot be used for real-time monitoring. By designing a system that takes advantage of multi-wire proportional chamber (MWPC) technology[15,16] while eliminating the necessity of using flammable gas, it becomes more practical for field works[16,17,18] With this newly developed system, called MWPC-based Muography Observation System (mMOS), we generated a muographic image with the highest definition yet achieved in Sakurajima, Japan with sufficiently low background noise. The first high-definition muographic image of the internal structure of Sakurajima will be shown
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