Hiroyuki Tanaka 교수

Radiographic imaging of magma dynamics in a volcanic conduit provides detailed information about ascent and descent of magma, the magma flow rate, the conduit diameter and inflation and deflation of magma due to volatile expansion and release. Here we report the first radiographic observation of the ascent and descent of magma along a conduit utilizing atmospheric (cosmic ray) muons (muography) with dynamic radiographic imaging. Time sequential radiographic images show that the top of the magma

Muon radiography can provide essentially a cross section through the object parallel to the plane of the detector, on which the average density along all the muon paths is projected, somewhat like X‐ray radiography. Very recently the use of emulsion films has given us a clue for visualization of the interior of volcanoes. To image a larger volcano in shorter time, we need a larger detector to collect more muon events. However, the time required for imaging will be proportional to the detection a

We developed a radiographic technique to image a subsurface conduit shape using cosmic‐ray muons. The test measurement was performed in Showa‐Shinzan lava dome located in Hokkaido, Japan as an example. A muon detector with an area of 6000 cm 2 was set up at the foot of the lava dome. Muon tracks recorded in nuclear emulsion films in the detector were analyzed to determine the level of energy absorption along different ray paths through subsurface beneath the lava dome. A typical angular resoluti

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 w

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 alth

We present a novel application of cosmic-ray muon radiography to image the shallow density structure beneath Asama Volcano, Japan. We use a single detector (emulsion cloud chamber) set up in an underground vault at an elevation of 2250 m on the eastern flank of Asama, 310 m below the summit of the edifice and 1 km away from the crater. The results point to two high-density anomalies located between the original pre-2004 eruption crater floor and post-2004 eruption crater profile. A third low-den

An emerging elementary particle imaging technique called muography has increasingly been used to resolve the internal structures of volcanoes with a spatial resolution of less than 100 m. However, land-based muography requires several days at least to acquire satisfactory image contrast and thus, it has not been a practical tool to diagnose the erupting volcano in a real time manner. To address this issue, airborne muography was implemented for the first time, targeting Heisei-Shinzan lava dome

High-energy muons that are generated via the reaction between primary cosmic rays and the Earth's atmosphere can be used to map out the density distribution in shallow parts of a volcano's interior. This new subterranean imaging technique called muography has been applied to three different kinds of volcano dynamics in Japan: lava dome formation, vulcanian explosions and magma convection. Taking all of the observational data together, it appears that muography can serve as a new and alternative

Lava domes are one of the conspicuous topographic features on volcanoes. The subsurface structure of the lava dome is important to discuss its formation mechanism. In the 1944 eruption of Volcano Usu, Hokkaido, a new lava dome was formed at its eastern foot. After the completion of the lava dome, various geophysical methods were applied to the dome to study its subsurface structure, but resulted in a rather ambiguous conclusion. Recently, from the results of the levelings, which were repeated du