Numerical simulation of the 1992 Flores tsunami: Interpretation of tsunami phenomena in northeastern Flores Island and damage at Babi Island

Numerical analysis of the 1992 Flores Island, Indonesia earthquake tsunami is carried out with the composite fault model consisting of two different slip values. Computed results show good agreement with the measured runup heights in the northeastern part of Flores Island, except for those in the southern shore of Hading Bay and at Riangkroko. The landslides in the southern part of Hading Bay could generate local tsunamis of more than 10 m. The circular-arc slip model proposed in this study for wave generation due to landslides shows better results than the subsidence model, It is, however, difficult to reproduce the tsunami runup height of 26.2 m at Riangkroko, which was extraordinarily high compared to other places. The wave propagation process on a sea bottom with a steep slope, as well as landslides, may be the cause of the amplification of tsunami at Riangkroko. The simulation model demonstrates that the reflected wave along the northeastern shore of Flores Island, accompanying a high hydraulic pressure, could be the main cause of severe damage in the southern coast of Babi Island.     

Relationship between crude-oil properties and geology in some oil and gas fields in the Niigata basin,Japan

The crude oil separately sampled from every producing well in the two fields in the Niigata Neogene sedimentary basin was analysed chemically and tested physically. The data obtained were interpreted, taking the geological conditions of the reservoir fully into consideration.     

Seismic response controlled structure with Active Variable Stiffness system

The Active Variable Stiffness (AVS) system is proposed as a seismic response control system. It actively controls structural characteristics, such as stiffness of a building, to establish a non-resonant state against earthquake excitations, thus suppressing the building's response. It consumes a relatively small amount of energy and maintains the safety of the building in moderate to severe earthquakes. In order to accumulate practical data and investigate them, a building has been constructed as a trial. This paper describes the applied system, the control algorithm, verification of stiffness selection, results of tests for verifying system characteristics, some observed earthquake records and simulation analyses. Responses in controlled and uncontrolled states have been compared to show the effectiveness of the proposed system.     

An evaluation of the apparent dissociation constants of carbonic acid in seawater

The internal consistency of five sets of apparent dissociation constants of carbonic acid in seawater obtained by Buch (1951), Lyman (1956), Edmond and Gieskes (1970), Hansson (1973) and Mehrbach et al. (1973) have been tested using the GEOSECS Atlantic data for the total alkalinity, the total CO₂ concentration and the partial pressure of CO₂. As a measure of the consistency for each of the five sets of the dissociation constants with the data, the 77 measured values of the partial pressure of CO₂ have been compared with those calculated from the alkalinity and total CO₂ values determined for these samples. It has been found that: (1) the apparent dissociation constants of Lyman (1956), Hansson (1973) and Mehrbach et al. (1973) appear to be internally consistent with the data, whereas those of Buch (1951) and of Edmond and Gieskes (1970) appear to be markedly inconsistent with the GEOSECS data; and (2) on the basis of a statistical analysis of the data grouped in three temperature ranges, the dissociation constants of Lyman (1956) and of Mehrbach et al. (1973) appear to be most satisfactory.     

Thermal history of iherzolite xenoliths—I. Petrology of iherzolite xenoliths from the ichinomegata crater,oga peninsula,northeast Japan

The thermal history of four spinel lherzolites (Lhz-13. Lhz-28, Lhz-29 and Lhz-53) from tuff breccia of the Ichinomegata crater, northeast Japan, has been studied in detail. Lhz-13 and Lhz-53 showed nearly perfect chemical homogeneity of the constituent minerals, and increase of Ca near the rim of olivine is the only disequilibrium evidence observed. In addition to the Ca zoning in olivine, Lhz-28 and Lhz-29 revealed compositional zoning in the Mg/Mg + Fe ratio and Ca content in ortho- and clinopyroxenes. Lhz-13 and Lhz-53 equilibrated at about 800°C in the upper mantle, based on Fe/Mg partitioning between olivine/spinel and olivine/clinopyroxene, and on the mutual solubility of Ca between olivine and pyroxenes. Lhz-28 and Lhz-29 also equilibrated originally at about 800°C, but were preheated at about 1000°C prior to their entrapment by the ascending host magma. The Fe/Mg partitioning between olivine /spinel and olivine/clinopyroxene reequilibrated during the preheating event: however, the Ca solubility did not reequilibrate. Olivine alone has rehomogenized with a high-Ca content but pyroxenes were compositionally zoned with Ca. The preheating event, indicated by the high-Ca content in the core of olivine, is recognized from about a half of the Ichinomegata Iherzolites (50 xenoliths were studied).The duration of heating during the transport of the xenolith by the magma (estimated from the width of the Ca zoning in the rim of olivine) ranges between several hours to a year depending on the rock specimen. From the requirement to reset olivine core compositions, the duration of the preheating event was estimated as greater than 1000 yr.     

Isotopic anomalies of noble gases in meteorites and their origins—VII. C3V carbonaceous chondrites

Noble gases were measured in bulk samples of the C3V chondrites Grosnaja, Vigarano, and Leoville, and in HF,HCl-insoluble residues before and after etching with HNO₃. The residues were characterized by INAA and SEM. Gas components were determined, directly or by subtraction, for the following fractions: HF,HCl-solubles (?98% of the meteorite), ‘sphase Q’, a poorly characterized trace mineral that is insoluble in HCl-HF but soluble in HNO₃, and an insoluble residue, consisting of ferrichromite, carbonaceous matter, and spinel.Bulk meteorites show some correlation of the noble-gas pattern with McSween's subclasses: two ‘oxidized’ C3V's—Allende (LEWIS et al, 1975) and Grosnaja— have lower Ar/Xe but higher Ne/Xe ratios than the ‘reduced’ C3V's—Vigarano and Leoville—which are transitional to LL3's and C3O chondrites in both respects. An HCl-soluble mineral of high Ar/Xr ratio seems to be responsible. In other respects, the 3 C3V's of this study resemble Allende, with only moderate differences. Phase Q contains most of the Ar, Kr, Xe, but only small amounts of Ne; the etched residues contain planetary Ne ($\text{Ne}{}^{20}\text{Ne}{}^{22}\text{? 8.5}$) and the controversial CCFXe component, enriched in the heavy Xe isotopes ($\text{Xe136}\text{Xe132 ? 0.4–0.5}$). The CCFXe is accompanied by an ‘L-Xe’ component that is enriched in the light Xe isotopes. The proportion of the two is virtually constant in C3V's. as in all other C-chondrites. in contrast to the ~ 2-fold variation in ordinary chondrites.C3V's have systematically higher $\text{Xe}{}^{136}\text{Xe}{}^{132}$ ratios, and hence higher ratios of CCFXe to planetary Xe, than do other chondrite classes. This may reflect some peculiarity in their formation conditions, favoring uptake of CCFXe.     

A strategy for the use of bomb-produced radiocarbon as a tracer for the transport of fossil fuel CO2 into the deep-sea source regions

Because the equilibration time for CO₂ gas between the surface ocean and atmosphere is an order of magnitude shorter than the equilibration time for the isotopes of carbon, bomb-produced radiocarbon cannot be simply used as a tracer for fossil fuel CO₂. This difference is especially important for the areas of deep water formation. In this paper we derive the relationship between the isotopic equilibration time and chemical equilibration times for carbon between sea and air. We also show that if the distribution of a second transient tracer is measured, it is possible to circumvent the ambiguity associated with this exchange time difference. Tritium, while adequate in purely diffusive models, is not ideal as the second transient in models involving advection (i.e., downwelling). For such models⁸⁵Kr or freon is a much better choice.     

Ries impact crater,southern Germany: search for meteoritic material

Twenty-three samples from the Ries crater, representing a wide range of shock metamorphism, were analyzed for seven siderophile elements (Au, Ge, Ir, Ni, Os, Pd, Re) and five volatile elements (Ag, Cd, Sb, Se, Zn). Taking Ir as an example, we found siderophile enrichments over the indigenous level of 0.015 ppb Ir occur in only eight samples. The excess is very modest; even the most enriched samples (a weakly shocked biotite gneiss and a metal-impregnated amphibolite) have Ir, Os corresponding to ~4 × 10^?4 C1 chondrite abundances. Of five flädle glasses analyzed only one shows excess Ir. Suevite matrix and vesicular glass have slight enrichment, but homogenous glass from the same rock does not. In flädle glasses, Ni and Se are strongly correlated and apparently reside in Ir, Os-poor Sulfides [pyrrhotite, chalcopyrite, pentlandite(?)]of terrestrial, probably sedimentary, origin. The Ir, Os and Ni enrichments of the metal-bearing amphibolite are compatible with chondritic ratios, but these are ill-defined because of uncertainty in Ni. In the other samples enriched in siderophiles Ir(Os), Ni and Se are mutually correlated; $\text{Ni}\text{Ir}$ and $\text{Ni}\text{Os}$ ~ 11 × C1 and are much higher than any chondritic ratios; $\text{Se}\text{Ni}\text{~ 2 × C1}$ and suggests a sulfide phase, rather than metal may be the host of the correlated elements. Lacking a plausible local source, this material is apparently meteoritic in origin. The unusual elemental ratios, coupled with the very low enrichments, tend to exclude chondrites and most irons as likely projectile material. Of the achondrites, aubrites seem slightly preferable. Ratios of excess siderophiles in Ries materiel match tolerably those of an aubrite (possibly atypical) occurring as an inclusion in the Bencubbin meteorite, Australia. The Hungaria group of Mars-crossing asteroids may be a source of aubritic projectiles.     

Petrologic model of the crust and upper mantle of the Japanese Island arcs

Mafic and ultramafic xenoliths, in the Holocene calc-alkali andesite of Ichinomegata(1) crater in Oga peninsula and those in the Plio-Pleistocene alkali-olivine basalts of Oki-Dōgo island in the Japan Sea, have been studied in detail. Based on geothermometry and geobarometry, and relative abundance of the rock types of the xenoliths, petrologic models of the crust and upper mantle beneath these two areas were constructed. The crust and upper mantle beneath Ichinomegata crater are characterized by hydrous and relatively low temperature conditions. On the other hand, the crust and upper mantle beneath Oki-Dōgo island are characterized by nearly anhydrous and high temperature conditions, and presence of thick lavers of peridotite and pvroxenite cumulates in the uppermost mantle. The crust and upper mantle of the western part of the Northeast Honshū Arc can be considered as similar to those beneath Ichinomegata crater, because of the common occurrence of similar mafic xenoliths from many andesite volcanoes in this area. The crust and upper mantle of the northern part of the Southwest Honshū Arc, in the same way, can be regarded as similar to those beneath Oki-Dōgo island. Differences in amount of hydrous minerals of deep-seated rocks between the two areas can be interpreted as due to the presence of migrating water derived from the subducting Pacific plate in the Northeast Honshū Arc. Difference in slope of the geotherm may be due to the difference in temperature of the partial melt zones beneath these two areas. Bulk chemical compositions of the lower crustal materials of the Japanese island arcs, 85 mafic inclusions from 15 volcanoes, are listed, and it is concluded that they are cumulates or metamorphosed cumulates in the lower crust.     

Melting kinetics of a plagioclase feldspar

Partial melting experiments on plagioclase feldspar have been carried out to investigate textures and kinetics of the melting. A labradorite single crystal was heated at one atmosphere pressure and temperatures within its melting interval as a function of time. So called honeycomb, fingerprint, or sieve textures were produced except for the runs just below the liquidus. The melting was initiated by heterogeneous nucleation of melt at the surface and/or interior (cracks and possively dislocations) of the crystal. The pattern of the melt is dendritic with a few μm arm spacing. After the melt develops throughout the crystal, the volumes of melt and residual crystal become larger and smaller, respectively, without changing the arm spacings. The melt is homogeneous and has the approximate temperature dependent liquidus composition irrespective of the time. There are compositional gradients in the residual crystal after short periods of melting. The An content of the crystals increases with increasing time until it finally reaches equilibrium with the melt after several thousands minutes of heating. It is concluded that the enlargement of the melt, the main process of the melting, is controlled by diffusion in the crystal. The fact that partial melts have the composition of the equilibrium liquidus even from the first several minutes strongly suggests that the local equilibrium at the crystal-liquid interface is satisfied during the melting. Some of the honeycomb, fingerprint, and sieve textures found in xenoliths and phenocrysts of sodic plagioclase in volcanic rocks would be caused by heating events (such as magma mixing) during which temperatures of magmas were temporarily higher than the solidus of some of the minerals.