Takeshi Hashimoto

Abstract: Broadband magnetotelluric (MT) measurements were conducted in 2010 and 2011 in the vicinity of Shinmoe-dake Volcano in the Kirishima volcano group, Japan, where sub-Plinian eruptions took place 3 times during 26–27 January 2011. By combining the new observations with previous MT data, it is found that an anomalous phase in excess of 90° is commonly observed in the northern sector of the Kirishima volcano group. Because the anomalous phase is not explained by 1-D or 2-D structure with isotropic resistivity media, 3-D inversions were performed. By applying small errors to the anomalous phase, we successfully estimated a 3-D resistivity structure that explains not only the normal data but also the anomalous phase data. The final model shows a vertical conductor that is located between a deep-seated conductive body (at a depth greater than 10 km) and a shallow conductive layer. By applying the findings of geophysical and petrological studies of the 2011 sub-Plinian eruptions, we infer that the subvertical conductor represents a zone of hydrothermal aqueous fluids at temperatures over 400°C, in which a magma pathway (interconnected melt) is partially and occasionally formed before magmatic eruptions. To the north of the deep conductor, earthquake swarms occurred from 1968 to 1969, suggesting that these earthquakes were caused by volcanic fluids.

TL;DR: In this paper, the authors conducted self-potential surveys sequentially from part to part over the central cones of Aso volcano since August 1998 by December 2001, and the compiled self-Potential (SP) map revealed large SP anomalies on the central cone.

TL;DR: In this article, wideband magnetotelluric (MT) soundings were carried out on Mt.Fuji volcano along a northeast to southwest axis and it was found by two-dimensional inversion using the highest quality data (in the frequency range 1-300 Hz) that a good conductor (resistivity of approximately a few ohm m) was located beneath the summit with a lateral extent of approximately 4 km.

TL;DR: A plume gas composition, sulfur dioxide flux and thermal image measurements and particle sampling were carried out using the unmanned aerial vehicle for three field campaigns on November 20 and 21, 2014, and June 2, 2015 as mentioned in this paper.

TL;DR: In this article, the magnetic and electric field variations associated with the 2000 eruption of Miyake-jima volcano are summarized and attributed to electrokinetic effect most probably due to forced injection of fluids from the source, while the magnetic field to the piezomagnetic effect due to increased pressure.