Seismic Exploration Using Active Sources at Kuchierabujima Volcano, Southwest Japan

Seismic exploration using artificial sources was conducted at Kuchierabujima volcano, southwest Japan in November 2004 by 40 participants from 9 national universities andJapan Meteorological Agency to investigate the subsurface seismic structure. The exploration was the 11th joint experiment under the National Project for Prediction of Volcanic Eruptions. A total of 183 temporal stations equippedwith a 2 Hz vertical component seismometer (including 75 3component seismometers) and a portable data logger were deployed on Kuchierabu Island. Dynamite shots with charges of 10-115 kg were detonated at 19 locations, and seismic signals were successfully recorded. To reveal the P-wave velocity structure, 2955 arrival times of the first motion were picked from the seismograms, and 2187 were classified into ranks A and B. From the record sections and the arrival time data, characteristics reflecting the geological structure were identified. Refracted waves of 5 km/s were observed at stations＞5km from the shot points. Apparent velocities near the shot points depend on the surface geology around the shots. P-wave arrived earlier at stations near the summits. Strongly scattered waves were observed similarly near the summits

Seismic exploration at Fuji volcano with active sources : The outline of the experiment and the arrival time data

Fuji volcano (altitude 3,776m) is the largest basaltic stratovolcano in Japan. In late August and early September 2003, seismic exploration was conducted around Fuji volcano by the detonation of 500 kg charges of dynamite to investigate the seismic structure of that area. Seismographs with an eigenfrequency of 2 Hz were used for observation, positioned along a WSW-ENE line passing through the summit of the mountain. A total of 469 seismic stations were installed at intervals of 250-500 m. The data were stored in memory on-site using data loggers. The sampling interval was 4 ms. Charges were detonated at 5 points, one at each end of the observation line and 3 along its length. The first arrival times and the later-phase arrival times at each station for each detonation were recorded as data. P-wave velocities in the surface layer were estimated from the travel time curves near the explosion points, with results of 2.5 km/s obtained for the vicinity of Fuji volcano and 4.0 km5/s elsewhere

Characteristics of the Moho as revealed from explosion seismic reflections beneath the Mizuho Plateau, East Antarctica

Seismic exploration was conducted on the Mizuho Plateau, East Antarctica, during the 1999-2000 austral summer season by the 41st Japanese Antarctic Research Expedition (JARE-41) Seismic shot records were obtained with clear arrivals of the later reflected phases by a total amount of 3300 kg dynamite charges in seven explosions along the Mizuho traverse route 180 km in length The purpose of this study is to investigate characteristics of the Moho discontinuity from reflective evidence by using explosive seismic waves First, we used the mirror image method for the travel time data of Moho reflected waves (PmP phases) Optimal image points were determined to minimize root-mean-square residuals between the observed and the calculated travel times by an iterative grid search at 1 km intervals The depth of the reflected Moho and the averaged incident angles were determined by taking the P wave velocity of the crust as a parameter The obtained Moho depth and the associated dipping angle were well correlated with those from the previous reflection study Amplitude spectrum analysis was also applied to obtain the difference in peak frequency of the spectrum between the PmP phases and the direct P phases The observed spectral ratios of the reflected PmP phases to the direct P phases indicate spectral peaks at 9 5 and 19 0 Hz, and a spectral trough at 13 8 Hz, respectively This pair of spectral peaks and the trough can be explained by the existence of a thin reflecting layer of 690-860 m thickness just beneath the Moho discontinuity The thin layer may have relatively lower velocities of 7 0-7 8 km/s than those of the surrounding uppermost mantle These relatively low velocity layers around the Moho are considered to be composed of clino-pyroxenite and/or pyroxenehornblende gneiss by comparison with high-pressure laboratory measurements of metamorphic rocks from the Liitzow-Holm Comple

Feasibility study on a multi-channeled seismometer system with phase-shifted optical interferometry for volcanological observations

A new Phase-Shifted Optical Interferometry seismometer system was tested in terms of its feasibility for multi-channeled volcanological observations in two volcanos in Japan. The system is capable of both sensing ground motions and transferring its signals through optical means. The prototype of this system comprises three optical-wired stations and optical components, and was deployed in Sakurajima Volcano in 2016 and in Asama Volcano in 2017. The system successfully operated for 134 days in total and provided seismograms that are in good agreement with those obtained using conventional systems. Several obstacles for putting this system to practical use that need to be solved were found through tests. Their solutions will be explored in subsequent research

Hybrid Chiral MoS₂ Layers for Spin‐Polarized Charge Transport and Spin‐Dependent Electrocatalytic Applications

【研究成果】電流中の“スピン”の制御により水電解の効率化を実現 --水素エネルギーによる持続可能な社会へ大きく貢献--. 京都大学プレスリリース. 2022-05-06.The chiral-induced spin selectivity effect enables the application of chiral organic materials for spintronics and spin-dependent electrochemical applications. It is demonstrated on various chiral monolayers, in which their conversion efficiency is limited. On the other hand, relatively high spin polarization (SP) is observed on bulk chiral materials; however, their poor electronic conductivities limit their application. Here, the design of chiral MoS₂ with a high SP and high conductivity is reported. Chirality is introduced to the MoS₂ layers through the intercalation of methylbenzylamine molecules. This design approach activates multiple tunneling channels in the chiral layers, which results in an SP as high as 75%. Furthermore, the spin selectivity suppresses the production of H₂O₂ by-product and promotes the formation of ground state O₂ molecules during the oxygen evolution reaction. These potentially improve the catalytic activity of chiral MoS₂. The synergistic effect is demonstrated as an interplay of the high SP and the high catalytic activity of the MoS₂ layer on the performance of the chiral MoS₂ for spin-dependent electrocatalysis. This novel approach employed here paves way for the development of other novel chiral systems for spintronics and spin-dependent electrochemical applications

P-wave velocity structure of the ice sheet and the shallow crust beneath the Mizuho traverse route, East Antarctica, from seismic refraction analysis

A seismic survey with a high density network was conducted by the 41st Japanese Antarctic Research Expedition (JARE-41) in the austral summer of 1999-2000. The seismic line was 190 km long, along the Mizuho traverse route from the base camp S16. 160 temporary seismic stations using data loggers were installed. The first arrival times were analyzed by the refraction method. The structure of the upper crust and overlying ice-sheet are revealed down to 7 km from refraction analysis of the first arrival times. A three layered structure is estimated. The first layer with a velocity of 3.8 km/s appears to be ice-sheet. The second layer with a velocity of 6.2 km/s of P-wave velocity is the surface layer of the continental crust. The thickness of this second layer is estimated to be approximately 5 km. The third layer is defined by the P-wave velocity of 6.5 km/s. Its shape of the upper interface is not declared. The topography of the basement determined from seismic refraction matches well with that determined from ice-radar sounding except for a small difference in the estimated depth of the basement. Two abrupt changes of the second layer depth are found near shot S-1 and shot S-4. The former includes a velocity change in the second layer. The latter discontinuity corresponds to the echo-less points of the ice-radar sounding. Velocity changes in the first and second layers are not detected across the latter discontinuity

Observation of Gonio Structures during Microhook Ab Interno Trabeculotomy Using a Novel Digital Microscope with Integrated Intraoperative Optical Coherence Tomography

Purpose. Observation of ocular structures using microscope-integrated intraoperative optical coherence tomography (iOCT) has been adopted. Using the novel digital ophthalmic microscope, ARTEVO 800 with iOCT, we tested the feasibility of trabecular meshwork (TM) imaging during microhook ab interno trabeculotomy, a minimally invasive glaucoma surgery. Methods. The nasal and temporal sides of the TM/inner wall of Schlemm’s canal were incised more than 3 clock hours in 14 glaucomatous eyes of 10 patients. To observe the trabeculotomy site, iOCT was performed with the real-time five-line scan mode under observation using a Swan-Jacob gonioprism lens. The success of the imaging and visibility of the trabeculotomy cleft and its incisional patterns (i.e., anterior, middle, or posterior pattern) were determined by reviewing the iOCT video files. Results. OCT images of the region of interest were acquired successfully in 100% of the 28 nasal or temporal sides in 14 eyes, although the trabeculotomy cleft was not visualized in four (14%) sides due to blockage of the OCT signal by a blood clot. Based on the predominant locations of the TM flaps in 24 of the acquired images, the trabeculotomy clefts were classified as anterior incisional patterns in 13 (54%), middle incisional patterns in nine (38%), and posterior incisional patterns in two (8%). Conclusion. Intraoperative imaging of the gonio structures including the trabeculotomy cleft was feasible using the ARTEVO 800 with iOCT in combination with a gonioprism