Chemical monitoring of volcanic gas using remote FT-IR spectroscopy at several active volcanoes in Japan

Chemical compositions of volcanic gases of several Japanese active volcanoes have been monitored from distant safe places since the beginning of the 1990s using an FT-IR spectral radiometer. For absorption measurements, an infrared light source behind volcanic gas emissions is necessary in a volcanic environment. In the early observations, infrared radiation from hot lava domes (Unzen volcano) and hot ground heated by high-temperature fumaroles (Usu, Aso, and Satsuma-Iwojima volcanoes) were used as infrared light sources. However, these sources were not available in many cases. This remote FT-IR method became more commonly applied to chemical monitoring of volcanic gases emitted from the summit or slopes of active volcanoes using scattered solar infrared light as infrared light sources (Sakurajima, Miyakejima, and Asama volcanoes). To date, eight species have been measured using this method: SO₂, HCl, HF, CO, CO₂, COS, SiF₄, and H₂O. The observations indicate that volcanic gases for each volcano have different chemical composition on a SO₂–HCl–HF ternary diagram in spite of similar tectonic settings, suggesting that vapor/melt volume ratios during volcanic gas formation differ among volcanoes. During more than 15 years of monitoring, chemical changes in volcanic gases attributable to ascent of magma were observed only at Asama, where HCl/SO₂ and HF/HCl ratios in the eruptive period were higher than those in non-eruptive period because of scrubbing of more soluble components in surface hydrothermal systems in the non-eruptive stage or solubility-controlled fractionation processes. Results show that these parameters are the most prospective ones among the various parameters measured using the remote FT-IR method to monitor volcanic activities.     

A static predictor of seismic demand on frames based on a post‐elastic deflected shape

Predictors of seismic structural demands (such as inter‐storey drift angles) that are less time‐consuming than nonlinear dynamic analysis have proven useful for structural performance assessment and for design. Luco and Cornell previously proposed a simple predictor that extends the idea of modal superposition (of the first two modes) with the square‐root‐of‐sum‐of‐squares (SRSS) rule by taking a first‐mode inelastic spectral displacement into account. This predictor achieved a significant improvement over simply using the response of an elastic oscillator; however, it cannot capture well large displacements caused by local yielding. A possible improvement of Luco's predictor is discussed in this paper, where it is proposed to consider three enhancements: (i) a post‐elastic first‐mode shape approximated by the deflected shape from a nonlinear static pushover analysis (NSPA) at the step corresponding to the maximum drift of an equivalent inelastic single‐degree‐of‐freedom (SDOF) system, (ii) a trilinear backbone curve for the SDOF system, and (iii) the elastic third‐mode response for long‐period buildings. Numerical examples demonstrate that the proposed predictor is less biased and results in less dispersion than Luco's original predictor. Copyright © 2006 John Wiley & Sons, Ltd.     

Chemical mass balance in a reaction zone between serpentinite and metapelites in the Nishisonogi metamorphic rocks, Kyushu, Japan: Implications for devolatilization

Abstract   Reaction zones of 0.5–10.0 m thick are commonly observed between serpentinite and pelitic schist in the Nishisonogi metamorphic rocks, Kyushu, Japan. Each reaction zone consists of almost monomineralic or bimineralic layers of talc + carbonates, actinolite (or carbonates + quartz), chlorite, muscovite and albite from serpentinite to pelitic schist. Magnesite + quartz veins extend into the serpentinite from the talc + carbonates layer, while dolomite veins extend into the pelitic schist from the muscovite layer. These veins are filled by subhedral minerals with oriented growth features. Primary fluid inclusions yield the same homogenization temperatures (145–150°C) both in the reaction zone and in the veins, suggesting their simultaneous formation. Mass-balance calculations using the isocon method indicate that SiO₂, MgO, H₂O and K₂O are depleted in the reaction zone relative to the protoliths. These components were probably extracted from the reaction zone as fluids during the formation of the reaction zone.     

Mineralogy of augite-bearing ureilites and the origin of their chemical trends

Abstract— Three augite-bearing ureilites from Antarctica, Y74130, MET78008 and ALH82106, have been studied by electron microprobe, scanning electron microscope (SEM), and analytical transmission electron microscope (TEM). The first two belong to the low-¹⁶O subgroup of Clayton and Mayeda (1988) and are closely related; ALH82106 belongs to the high-¹⁶O subgroup. MET78008 is an augite-olivine ureilite, similar to the augite-bearing part of the Y74130. Augites poikilitically include ellipsoidal pigeonites, and low-Ca pyroxene poikilitically encloses ellipsoidal olivine and augite. The temperature of last equilibration deduced from an orthopyroxene-pigeonite-augite assemblage is above 1200 °C. The ALH82106 pigeonite contains irregular augite inclusions produced by decomposition. Augites in Y74130, MET78008 and ALH82106 (decomposed one) all show similar spinodal decomposition textures on the TEM scale. Cooling rates estimated from an experimentally calibrated diagram for the wavelengths of spinodal decomposition versus cooling rates are about 20 °C/hr. The calcic trend for the low-¹⁶O subgroup including Y74130 and MET78008 shows large Ca variations in pyroxene with similar Mg/Fe ratio; differentiation involving reduction was not an important process. Augite in ALH82106 is a minor phase and contains lower Na₂O contents than Y74130 and MET78008, confirming that ALH82106 is not directly related to them.     

Semi-empirical estimation of ground motion using observed records at a site in Shikoku, Japan

A semi-empirical approach using fore- or after-shockrecords as Green's functions is applicable to thesimulation of strong ground motion, however suchrecords are obviously not available for predictionpurposes. Thus we have predicted ground motion fora hypothetical large earthquake from other minorevents by adopting a distance correction based ongeometrical spreading. Another difficulty inprediction is fault modeling. Surface traces weresimplified as fault models 27, 46, 55, and 77 km inlength. Further, the actual fault rupture may beinhomogeneous, so an asperity distribution isassumed. This asperity model assumes thatdislocation and stress drop are double than theaverage values. Although, the near field term isneglected in our simulation, no significantdifference was seen in the motions estimated byindividual models for periods up to 2.0 seconds. This indicates that the dependence of source size issmall for strong motion, perhaps as a result of therandom summation of high-frequency phases.     

Estimating ground motions using recorded accelerograms

A procedure for estimating ground motions using recorded accelerograms is described. The premise of the study is the assumption that future ground motions will be similar to those observed for similar site and tectonic situations in the past. Direct techniques for scaling existing accelerograms have been developed, based on relative estimates of local magnitude,M _L . Design events are described deterministically in terms of fault dimension, tectonic setting (stress drop), fault distance, and site conditions. A combination of empirical and theoretical arguments is used to develop relationships betweenM _L and other earthquake magnitude scales. In order to minimize scaling errors due to lack of understanding of the physics of strong ground motion, the procedure employs as few intermediate scaling laws as possible. The procedure conserves a meaningful measure of the uncertainty inherent when predicting ground motions from simple parameterizations of earthquake sources and site conditions.     

Range expansion and redefinition of a crop-raiding rodent associated with global warming and temperature increase

Since the 1970s, the crested porcupine Hystrix cristata has shown a marked range expansion in Italy. A web page has been created to collect occurrences of this species to monitor its distribution redefinition. Thus, aims of this work were (i) to identify the main predictors promoting the distribution of this large rodent in Italy and (ii) to predict its potential expansion under future climate change scenarios. A total of 1674 locations were used for this analysis, i.e., all those collected through the web page, with the exception of recently introduced populations (Sardinia, Western Liguria and Province of Varese). The current distribution of the crested porcupine covers a total of 135,177 km², as estimated through ensemble predictions. Future climate change scenarios for 2050 and 2070 show that a further range expansion by this species would occur up to 225,576 km², mainly towards areas where the species was historically absent. The increase of isothermality (i.e., the ratio between the mean diurnal and the annual temperature range) and the mean temperature of the driest months would help crested porcupines to reach high altitudes, e.g., in the Alps. In mountain habitats, the ongoing global warming is shifting the distribution of European forests to high elevations, thus potentially providing porcupines with suitable habitats. A reduction in snow cover and the snow period at ground level would remove an important barrier to the range expansion of the crested porcupine in Italy, and thus facilitate digging and food search by this large rodent. Despite being protected at national and international levels, the crested porcupine is reported to be an introduced species to Italy and, therefore, monitoring its range expansion is required. Furthermore, there are complaints about crop damage in agriculture ecosystems, and the species is still widely poached, thus additional management practices are required. Thus, given the conservation interest of this large rodent, an integrated and constantly updated monitoring system that sustains an addressed set of decision-making tools is recommended.     

Estimation of property loss and business interruption loss caused by storm surge inundation due to climate change: a case of Typhoon Vera revisit

This paper estimates property loss and business interruption loss under scenarios of storm surge inundation to explore the economic impact of climate change on Ise Bay, Japan. Scenarios-based analyses are conducted with respect to Typhoon Vera, which caused the most severe storm surge in the recorded history of Japan in 1959. Four different hazard scenarios are chosen from a series of typhoon storm surge inundation simulations: Typhoon Vera’s landfall with respect to the condition of the past seawall; Typhoon Vera’s landfall with respect to the condition of the current seawall; intensifying Typhoon Vera, but retaining its original tracks; and intensifying Typhoon Vera, but choosing the worst tracks from various possible typhoon tracks. Our economic loss estimation takes advantage of fine geographical scale census and economic census data that enable us to understand the spatial distribution of property loss and business interruption loss as well as identify the most potentially affected areas and business sectors on a sub-city scale. By comparing the property loss and business interruption loss caused by different hazard scenarios, the effect of different seawalls is evaluated and the economic impact of future climate change is estimated. The results indicate that although the current seawall can considerably reduce the scale of losses, climate change can cause Ise Bay to experience more serious storm surge inundation. Moreover, the resulting economic losses would increase significantly owing to a combination of climate change and the worst track scenario. It is, therefore, necessary to consider more countermeasures to adapt to climate change in this area.     

Sea level measurements for inferring ground deformations in Rabaul Caldera

Rabaul tide gauge records from 1968 through 1985 give the amount of vertical movement in the northern part of Rabaul Caldera. Monthly mean sea level data were compared with other regional tide gauge stations to remove large scale oceanographic effects. No large vertical movements (> 0.3 cm/yr) were noted in this portion of the caldera. The results of sea level measurements at other points around the caldera, from 1981 through 1983 are consistent with the 1 to 10 cm of uplift observed on Matupit Island from optical leveling surveys. There was relatively little vertical movement (～ 0.1 cm/yr) in the Vulcan area.     

Sea level measurements for Inferring ground deformations in Rabaul Caldera

Rabaul tide gauge records from 1968 through 1985 give the amount of vertical movement in the northern part of Rabaul Caldera. Monthly mean sea level data were compared with other regional tide gauge stations to remove large scale oceanographic effects. No large vertical movements (> 0.3 cm/yr) were noted in this portion of the caldera. The results of sea level measurements at other points around the caldera, from 1981 through 1983 are consistent with the 1 to 10 cm of uplift observed on Matupit Island from optical leveling surveys. There was relatively little vertical movement ( 0.1 cm/yr) in the Vulcan area.