Detecting a mass change inside a volcano by cosmic-ray muon radiography (muography): First results from measurements at asama volcano, Japan

Abstract

A visual detection and monitoring of volcanic eruptions is the most essential information. In February 2, 2009, Asama volcano, Japan erupted and a large amount of volcanic ash was ejected from the vent. We have observed the activity at Asama since October 12, 2008. For eruption monitoring we used cosmic-ray muon radiography (muography), a new volcano monitoring system recently developed by Tanaka et al. (2009). We measured a quantitative mass loss inside the crater during the eruption event although no changes were found below the crater. The measured value of 30,780 tons is consistent with a model calculation of volcanic ash flow as observed on February 2, 2009. The obtained radiographic image suggests that a "boiling liquid expanding vapor explosion" occurred and a part of an old lava mound was exploded. This picture is consistent with die analytical result of the volcanic ash ejected on February 2, 2009. Copyright 2009 by the American Geophysical Union.