Permeability-control on volcanic hydrothermal system: case study for Mt. Tokachidake, Japan, based on numerical simulation and field observation

We investigate a volcanic hydrothermal system by using numerical simulation with three key observables as reference: the magnetic total field, vent temperature, and heat flux. We model the shallow hydrothermal system of Mt. Tokachidake, central Hokkaido, Japan, as a case study. At this volcano, continuous demagnetization has been observed since at least 2008, suggesting heat accumulation beneath the active crater area. The surficial thermal manifestation has been waning since 2000. We perform numerical simulations of heat and mass flow within a modeled edifice at various conditions and calculate associated magnetic total field changes due to the thermomagnetic effect. We focus on the system’s response for up to a decade after permeability is reduced at a certain depth in the modeled conduit. Our numerical simulations reveal that (1) conduit obstruction (i.e., permeability reduction in the conduit) tends to bring about a decrease in vent temperature and heat flux, as well as heat accumulation below the level of the obstruction, (2) the recorded changes cannot be consistently explained by changing heat supply from depth, and (3) caprock structure plays a key role in controlling the location of heating and pressurization. Although conduit obstruction may be caused by either physical or chemical processes in general, the latter seems more likely in the case of Mt. Tokachidake

Seismic refraction and wide-angle reflection exploration by JARE-43 on Mizuho Plateau, East Antarctica

The 43rd Japanese Antarctic Research Expedition (JARE-43) carried out seismic exploration experiments on Mizuho Plateau,East Antarctica,in the austral summer season of ,2001-2002. The exploration was composed of seven large explosions and 161seismic stations distributed along the 151 km-long seismic line.The first arrival time data are analyzed by a refraction method.It is found that the ice sheet is composed of two layers:the upper layer with P wave velocity of 2.7-2.9 km/s has thickness of 35-45 m,and the lower layer with P wave velocity of 3.7-3.9 km/s continues to the bedrock.Lateral velocity variation in the upper-most crust is revealed:P wave velocity for the upper-most crust in the southern and central parts is 6.1-6.2 km/s and that in the northern part is5.9 km/s. This result implies that the geological boundary observed along the coast in the Lu tzow-Holm Bay and Prince Olav Coast regions possibly continues to the inland area.The S wave velocity is also obtained to be roughly 3.5km/s for the whole upper-most crust.Travel time analysis of two distinct reflection phases shows two horizontal reflecting planes located at 19 and 40km depth; the latter corresponds to the Moho discontinuity

Lung adenocarcinoma with giant cyst formation showing a variety of histologic patterns: a case report

<p>Abstract</p> <p>Introduction</p> <p>Lung cancer with large cyst formation is relatively rare. This is a case report of a patient with lung cystic adenocarcinoma with multiple histologic patterns. This type of lung adenocarcinoma is believed to be the first reported case in English language medical literature.</p> <p>Case presentation</p> <p>A 60-year-old Japanese woman was admitted to hospital complaining of dyspnea and died of respiratory failure. She had been suffering from lung cancer with pleural effusion for five years. Autopsy analysis revealed lung adenocarcinoma with large cyst formation showing a variety of histologic patterns.</p> <p>Conclusions</p> <p>Autopsy analysis of this atypical case of lung cancer may provide insight and lead to a better understanding of the heterogeneity and clonal expansion of lung adenocarcinoma.</p

Performance Test of Infrasound Sensor in Low-temperature Environment ─ Potential for Application in Antarctic Observation ─

For infrasound monitoring in Antarctica, there is a need for infrasound sensors with low power consumption and high resistance to low-temperature environments. A new-type infrasound sensor (TYPE7744N/5002A) manufactured by ACO Co., Ltd. (Japan) with the cooperation of the Earthquake Research Institute, the University of Tokyo, achieves less than half the power consumption of existing models. To evaluate the applicability of the new sensor to Antarctic observation, we conducted a low-temperature (－30℃) test for four types of sensors, including the new one. We compared the results to those from a room temperature (21℃) test and examined changes in amplitude-phase characteristics based on a reference sensor (Model60Vx2, Chaparral Physics), proven in use in polar regions. There were no problems in the operation of the new sensor during the 30 days of the test. Spectral power ratio to the reference sensor changed up to 19% compared to the room temperature test, suggesting that the sensitivity fluctuates with temperature. Phase characteristics were not significantly affected by low temperatures. Future trials are desired to evaluate the long-term stability of the new sensor, e.g., by conducting experimental overwintering observations at Syowa Station

Petrological architecture of a magmatic shear zone: A multidisciplinary investigation of strain localisation during magma ascent at Unzen volcano, Japan

Shearing of magma during ascent can promote strain localisation near the conduit margins. Anymechanical and thermal discontinuities associated with such events may alter the chemical, physicaland rheological stability of the magma and thus its propensity to erupt. Lava spines can record suchprocesses, preserving a range of macroscopic and microscopic deformation textures, attributed toshearing and friction, as magma ascends through the viscous-brittle transition. Here, we use a multi-disciplinary approach combining petrology, microstructures, crystallography, magnetics and experi-mentation to assess the evidence, role and extent of shearing across a marginal shear zone of the1994–1995 lava spine at Unzen volcano, Japan. Our results show that crystals can effectively moni-tor stress conditions during magma ascent, with viscous remobilisation, crystal plasticity and com-minution all systematically increasing towards the spine margin. Accompanying this, we find anincrease in mineral destabilisation in the form of pargasitic amphibole breakdown displaying tex-tural variations across the shear zone, from symplectitic to granular rims towards the spine margin.In addition, the compaction of pores, chemical and textural alteration of interstitial glass and mag-netic variations all change systematically with shear intensity. The strong correlation between thedegree of shearing, crystal deformation and disequilibrium features, together with distinct magneticproperties, implies a localised thermal input due to shear and frictional processes near the conduitmargin during magma ascent. This was accompanied by late-stage or post-emplacement fluid- andgas-induced alteration of the gouge, as well as oxidation and glass devitrification. Understandingand recognising evidence for strain localisation during magma ascent may, therefore, be vital whenassessing factors that regulate the style of volcanic eruptions, which may provide insights into thecryptic shifts from effusive to explosive activity as observed at many active lava dome

Seismicity controlled by resistivity structure : the 2016 Kumamoto earthquakes, Kyushu Island, Japan

The M JMA 7.3 Kumamoto earthquake that occurred at 1:25 JST on April 16, 2016, not only triggered aftershocks in the vicinity of the epicenter, but also triggered earthquakes that were 50–100 km away from the epicenter of the main shock. The active seismicity can be divided into three regions: (1) the vicinity of the main faults, (2) the northern region of Aso volcano (50 km northeast of the mainshock epicenter), and (3) the regions around three volcanoes, Yufu, Tsurumi, and Garan (100 km northeast of the mainshock epicenter). Notably, the zones between these regions are distinctively seismically inactive. The electric resistivity structure estimated from one-dimensional analysis of the 247 broadband (0.005–3000 s) magnetotelluric and telluric observation sites clearly shows that the earthquakes occurred in resistive regions adjacent to conductive zones or resistive-conductive transition zones. In contrast, seismicity is quite low in electrically conductive zones, which are interpreted as regions of connected fluids. We suggest that the series of the earthquakes was induced by a local accumulated stress and/or fluid supply from conductive zones. Because the relationship between the earthquakes and the resistivity structure is consistent with previous studies, seismic hazard assessment generally can be improved by taking into account the resistivity structure. Following on from the 2016 Kumamoto earthquake series, we suggest that there are two zones that have a relatively high potential of earthquake generation along the western extension of the MTL