Multiple-tracers-aided surface-subsurface hydrological modeling for detailed characterization of regional catchment water dynamics in Kumamoto area,southern Japan

Hydrogeology Journal - Integrated watershed modeling techniques have been applied in recent years to examine surface and subsurface interactions. Model performance is often evaluated by best fit of...     

Evolution of high-Mg–Al granulites from Sunkarametta, Eastern Ghats, India: evidence for a lower crustal heating–cooling trajectory

A suite of high-Mg–Al granulites from Sunkarametta, Eastern Ghats Belt, India, shows contrasting prograde assemblages of extremely aluminous orthopyroxene+cordierite+sapphirine and similarly aluminous orthopyroxene+Ti-rich spinel in closely associated domains. Textural and compositional characteristics indicate that both were derived from prograde dehydration–melting of biotite–plagioclase–quartz-bearing protoliths. The former assemblage was stabilized at relatively more magnesian bulk composition. Geothermobarometric data and petrogenetic grid considerations place 'peak' metamorphic conditions at c. 950 °C and 9 kbar. Subsequent to peak metamorphism, the rocks cooled to c . 700–750 °C, with slight lowering of pressure, and the retrograde reactions also involved melt–solid interaction. The inferred P – T  trajectory is one of heating–cooling at lower crustal (25–30 km) depths.     

Quantitative assessment on the influence of heavy rainfall on the crystalline schist landslide by monitoring system -case study on Zentoku landslide, Japan

On Shikoku Island, which is one of the four main islands of Japan, a large number of large-scale crystalline schist landslides have been revealed and are being monitored by an observation system. Seasonal heavy rainfall is the most active meteorological factor that can threaten the stability of this kind of site-specific landslide. In this paper, on the basis of the study of the rainfall-related behavior of a typical crystalline schist landslide, the Zentoku landslide, by analyzing the precisely and continuously observed piezometric and movement data, a method was developed to quantitatively assess the effect of heavy rainfall on a large-scale landslide. The results indicated that heavy rainfall-induced landslide displacement shows good correlation with the variation of groundwater levels. Variations of groundwater level have been simulated with the use of a tank model. The simulation using this model permits the change in water levels for future rainfall events to be predicted. By combining the predicted results with the empirical relation between displacements and water levels, rainfall-induced landslide movement during extreme rainfall events can be estimated in advance. The effect of heavy rainfall on sliding behavior can be quantified in terms of the change in displacement. Thus warning information or advisories for the local residents can be provided.     

Genetic reinterpretation of crystallographicintergrowths of jacobsite andhausmannite from natural assemblages

Summary Crystallographic intergrowths of jacobsite and hausmannite (vredenburgite) occur in association with braunite in the Precambrian Sausar Group of rocks, India, that were metamorphosed under 600-700°C and P 6 kb. Quartz, hematite, rhodochrosite and a later hausmannite may occasionally occur as minor associates. Detailed characterization of the intergrown phases reveals that hausmannite lamellae, oriented in 4 or 5 crystallographic directions in the jacobsite host, show a wide variation in thickness and tapered intersections at low angles. The lamellae may be locally deformed. Analytical data reveal that the composition of natural hausmannite and jacobsite in the intergrowths cannot be approximated within the system Fe₃O₄ -Mn₃O₄, as has been conventionally done. These really belong to the Fe₂O₃-Mn₃O₄ subsystem. In the two phase intergrowths, hausmannite is depleted and the jacobsite is enriched in Fe in higher grade rocks. Mineral associations and petrographic considerations suggest that the jacobsite-hausmannite intergrowth originated through prograde decarbonation-oxidation reactions of a carbonatic precursor in an unbuffered X CO₂ situation, but f O₂ was held between hematite-magnetite and bixbyite-hausmannite buffers at the ambient physical conditions of metamorphism. Subsequent oxidation yielded a strong oxygenbuffering assemblage jacobsite, hausmannite, braunite, hematite and quartz. This study negates the commonly held idea that hausmannite jacobsite crystallographic intergrowth (vredenburgite) originates through unmixing of a high ([ldvredenburgite) originates through unmixing of a high temperature spinel_ss temperature spinel_ss during cooling.

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Genetische Reinterpretation der kristallographischen Verwachsungen von Jakobsit und Hausmannit in natürlichen Vorkommen

Zusammenfassung Kristallographische Verwachsungen von Jakobsit und Hausmannit (Vredenburgit) treten in Verbindung mit Braunit in Gesteinen der präkambrischen Sausargruppe in Indien auf. Die Gesteine wurden bei Drucken von ca. 6 kbar und Termperaturen von 600–700°C metamorphosiert. Quarz, Hämatit, Rhodochrosit, und Hausmannit als Spätphase treten gelegentlich als untergeordnete Gemengteile auf. Hausmannit-Lamellen, die in vier oder fünf kristallographischen Richtungen in Jakobsit orientiert sind, haben sehr unterschiedliche Durchmesser und bilden versetzte Zwickel in kleinem Winkel mit dem Jakobsit. Die Lamellen können lokal deformiert sein. Analytische Daten zeigen, daß die Zusammensetzung von natürlichem Hausmannit und Jakobsit in Verwachsungen nicht, wie bisher angenommen, in dem System Fe₃O₄-Mn₃O₄ dargestellt werden kann. Diese Verwachsungen gehören vielmehr in das Fe₂O₃-Mn₃O₄ System. In höher-gradigen metamorphen Gesteinen ist Fe in zwei-phasigen Verwachsungen im Hausmannit ab- und im Jakobsit angereichert. Die Mineralzusammensetzung und petrographische Gesichtspunkte lassen darauf schließen, daß die Jakobsit/Hausmannit Verwachsung durch prograde Dekarbonatisierung/Oxydationsreaktion eines karbonatischen Vorläufers in einem nicht gepufferten X CO₂ Milieu entstanden ist. F O₂ wurde durch Hämatit-Magnetit und Bixbyit-Hausmannit Puffer unter den gegebenen physikalischen Bedingungen der Metamorphose stabil gehalten. Eine nachfolgende Oxydation führte zu einer starken Sauerstoff-puffernden Assoziation von Jakobsit, Hausmannit, Braunit, Hämatit und Quarz. Diese Untersuchungen widerlegen die allgemein verbreitete Ansicht, daß die kristallographische Verwachsung von Hausmannit und Jakobsit (Vredenburgit) durch Entmischung eines Hochtemperatur-Spinells während der Abkühlung entstanden ist.

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Undrained dynamic-loading ring-shear apparatus and its application to landslide dynamics

Landslides are gravitational mass movements of rock, debris or earth. Some move very slowly, thus conforming to the field of statics, but some move rapidly. Study of the initiation and motion of rapid landslides needs to develop Landslide Dynamics involving dynamic loading and dynamic generation/dissipation of excess pore-water pressure. New developments in science can be facilitated by new technological advances. This study aimed to develop a new apparatus that can geotechnically simulate the formation of the shear zone and the following long and rapid shear displacement that occurs in high-velocity landslides. Professor K. Sassa and his colleagues at DPRI (Disaster Prevention Research Institute), Kyoto University, have worked to develop an undrained dynamic-loading ring-shear apparatus for this purpose. A series of different types of apparatus (DPRI-3, 4, 5, 6, 7) have been developed from 1992 to the present. This paper describes the development of this apparatus and its application to the study of earthquake-induced landslides and the latest landslide-triggered debris flow in Japan. Also, tests of the latest version (DPRI-7) with a transparent shear box for direct observation of the shear zone during a rapid shearing are described.     

Anisotropic phase transition of rutile under shock compression

Shock recovery experiments for single crystal and powdered specimens of TiO₂ with the rutile structure were performed in the pressure range up to 72 GPa. Single crystal specimens were shocked parallel to [100], [110] and [001] directions. X-ray powder diffraction analysis showed that the amount of -PbO₂ type TiO₂ produced by shock-loading depended strongly on the shock propagation direction. The maximum yield (about 70%) was observed for shock loading to 36 GPa parallel to the [100] direction. In the [001] shock direction, the yield is much smaller than that of the [100] direction. This anisotropic yield was consistent with the observed anisotropy of the phase transition pressure in shock compression measurements. However, transformation to the -PbO₂ type cannot explain the large volume change observed above about 20 GPa. On the basis of the high pressure behavior of MnF₂, we assumed that the high pressure phase was either fluorite or distorted fluorite type and that the phase conversion to the -PbO₂ type was induced spontaneously in the pressure reduction process.We present a displacive mechanism of phase transition under shock compression from the rutile structure to the fluorite structure, in which the rutile [100] is shown to correspond to the fluorite [001] or [110] and the rutile [001] to the fluorite [110]. Direct evidence is obtained by examining the [100] shocked specimen by high resolution electron microscopy.     

Formation process of two massive dams following rainfall-induced deep-seated rapid landslide failures in the Kii Peninsula of Japan

Extreme heavy rainfall due to Typhoon Talas on September 2–4, 2011 in the Kii Peninsula, Japan, triggered numerous floods and landslides. This study investigates the mechanism and the entire process of rainfall-induced deep-seated landslides forming two massive dams in the Kuridaira and Akatani valleys, respectively. The mechanism of the rapid deep-seated landslides is examined through a series of laboratory experiments on samples from sliding surfaces by using undrained high-stress dynamic-loading ring-shear apparatus. The test results indicate that the failure of samples is triggered by excess pore water pressure generation under a shear displacement from 2 to 7 mm with a pore pressure ratio ranging from 0.33 to 0.37. The rapid movement of landslides is mainly attributed to high mobility due to the liquefaction behavior of both sandstone-rich and shale samples. Geomorphic settings and landslide mobility are major contributing factors to the dam formation. Additionally, shear displacement control tests show that a certain amount of shear displacement between 2 and 7 mm along the sliding surfaces of the gravitationally deformed slopes might have led to the failures. Importantly, computer simulation with LS-RAPID software using input parameters obtained from physical experiments is employed to interpret the entire formation process of the abovementioned two landslide dams. The simulation results are examined in accordance with the observed on-site geomorphic features and recorded data to explain the possibility of sliding processes. The results further point out that local failures are initiated from the lower middle part of the landslide bodies where the geological boundary exists. This condition most probably influences the landslide initiation in the two case studies. This research is therefore helpful for hazard assessment of slopes that are susceptible to deep-seated landslides and other sequential processes in areas with geology and geomorphology similar to that of the Kii Peninsula.     

The luminosity function for the globular cluster M15

We obtained the luminosity function from the Main-Sequence turnoff region to the subgiants for M15 (V=17.0–19.6), using plates taken by the Kitt Peak 4 m reflector. The measured region isr=2.5–8.0 zone. We extrapolated the star counts to the cluster center and to the tidal limit, using King's (1966) photometry, Kinget al.'s (1968) counts, Peterson and King's (1975) result, and Simoda and Iben's (1970) theoretical results.The comparison of the observed function with the theoretical ones by Simoda and Iben (1970) indicates that the observation is consistent with the theory forX0.9±0.1, thus marginally inconsistent with the Big Bang cosmology value (X=0.76). The comparison with Bertelliet al. (1970) theoretical ones gives contradictory results. Possible causes of this problem are the improper extrapolation of star counts to the cluster center and/or the inaccuracies of the theoretical luminosity functions so far published, and/or the impropriety of the canonical structure and evolution theory of Population II stars. In the last two cases, the ages and the helium abundances of globular clusters may vary.We also obtained the luminosity function for blue horizontal branch stars fromV=17.0 to 19.6.Kitt Peak National Observatory, U.S.A., which is operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.     

Contrasting Episodes of Regional Granulite-Facies Metamorphism in Enclaves and Host Gneisses from the Aravalli Delhi Mobile Belt, NW India

The Aravalli–Delhi Mobile Belt in the northwestern partof India demonstrates how granulite enclaves and their hostgneisses can be utilized to unravel multistage metamorphic historiesof orogenic belts, using three suites of metamorphic rocks:(1) an enclave of pelitic migmatite gneiss–leptynite gneiss;(2) metamorphosed megacrystic granitoids, intrusive into theenclave; (3) host tonalite–trondhjemite–granodiorite(TTG) gneisses associated with an interlayered sequence of garnetiferousmetabasite and psammo-pelitic schist, locally migmatitic. Basedon integrated structural, petrographic, mineral compositional,geothermobarometric studies and P–T pseudosection modellingin the systems NCKFMASH and NCFMASH, we record three distincttectonothermal events: an older, medium-pressure granulite-faciesmetamorphic event (M₁) in the sillimanite stability field, whichis registered only in the enclave, a younger, kyanite-gradehigh-pressure granulite-facies event (M₂), common to all thethree litho-associations, and a terminal amphibolite-faciesmetamorphic overprint (M₃). The high-P granulite facies eventhas a clockwise P–T loop with a well-constrained prograde,peak (M₂, P 12–15 kbar, T 815°C) and retrograde (M_2R,6·1 kbar, T 625°C) metamorphic history. M₃ is recordedparticularly in late shear zones. When collated with availablegeochronological data, the metamorphic P–T conditionsprovide the first constraint of crustal thickening in this belt,leading to the amalgamation of two crustal blocks during a collisionalorogeny of possible Early Mesoproterozoic age. M₃ reactivationis inferred to be of Grenvillian age. KEY WORDS: Northwestern India; polycyclic granulite enclave; pseudosection; high-pressure metamorphism; P–T path