Unusually low seismic activity in the focal region of the great Kanto earthquake of 1923     

Kunihiko Shimazaki 《Tectonophysics》1971

The epicenters of earthquakes which occurred in the vicinity of Tokyo during the period 1926–1967 have been plotted by an IBM 360/40 computer at the Earthquake Prediction Observation Center. As a result, a seismically quiescent area is found to the south of Tokyo. The area coincides with the shallower part of the focal plane of the great Kanto earthquake of 1923 as obtained from the analyses of seismological and geodetic data. In historical times, many large earthquakes having a magnitude of 7.0 or greater took place in this area. If it is assumed that the strain energy has been constantly accumulated in this area, an energy potentially equivalent to that of a large earthquake of which the magnitude exceeds 7.7 seems to be stored in the crust there.  相似文献   

Characterization of sulfate ion in travertine     

Bokuichiro Takano  Yasuhiro Asano  Kunihiko Watanuki 《Contributions to Mineralogy and Petrology》1980,72(2):197-203

The mode of incorporation of sulfate ion in travertine was discussed on the basis of chemical compositions, i.r. and laser Raman spectra. These data strongly suggest that most of the sulfate ions in the calcitic travertine replace carbonate ions. This conclusion is in good harmony with the facts that calcite incorporates more sulfate ions than aragonite does and that the sulfate content of manganoan calcite decreases with increasing manganese content (Takano et al. 1977). Based on this conclusion, retarding effect of sulfate ion on the precipitation of calcite from solution was discussed.  相似文献   

Lead isotopes and age of Hawaiian lherzolite nodules     

Masana Morioka  Kunihiko Kigoshi 《Earth and Planetary Science Letters》1975,25(2):116-120

The reaction between enstatite (En_95.3Fs_4.7) and CaCO₃ has been studied at pressures between 23 and 77 kbars and at temperatures between 800° and 1400°C. At 1000°C enstatite and CaCO₃ react to form dolomite and diopside solid solutions at pressures below approximately 45 kbars and magnesite and diopside solid solutions at higher pressures. The curve for the reaction dolomite_ss + enstatite_ss ? magnesite_ss + diopside_ss lies between 40 to 45 kbars at 1000°C and between 45 and 50 kbars at 1200°C. It is very close to the graphite-diamond transition curve. These experimental results indicate that calcite (or aragonite) is unstable in the presence of enstatite, and that dolomite and magnesite are the stable carbonates at high pressures. The forsterite + aragonite assemblage is, however, stable to at least 80 kbars at 800°C. It is suggested that in the upper mantle where enstatite is present, dolomite is stable to depths of about 150 km and magnesite is stable at greater depths in the continental regions, assuming that the partial pressure of CO₂ is equal or close to the total pressure. It is also suggested that carbonate inclusions in pyroxene can be used as an indicator of the depth of their equilibration; dolomite inclusions in enstatite would be formed at depths shallower than 150 km and magnesite inclusions in diopside at greater depths. Eclogite and peridotite inclusions in kimberlite may be classified on this basis.  相似文献   

Radiocarbon dates of elevated shorelines,Indonesia and Malaysia. Part 1     

H.D. Tjia  Shoji Fujii  Kunihiko Kigoshi  Arata Sugimura  Thomas Zakaria 《Quaternary Research》1972

Four new radiocarbon dates of elevated strandlines in tectonically active areas of eastern Indonesia and East Malaysia indicate average rates of uplift that range between 4.5 and 9 mm annually during the past 24,000 yr. These values are at least three times higher than former estimates from eastern Indonesia. Another radiocarbon date from the south arm of Sulawesi—also tectonically mobile—indicates a rate of uplift of 1.4–2.5 mm per year which corresponds with earlier determinations. This particular case, however, suggests that the sample was probably located close to a north-south axis about which southern Sulawesi was tilted during the Quaternary.  相似文献   

Composition of the first bulk melt sample from a volcanic region of Mars: Queen Alexandra Range 94201     

David A. KRING  James D. GLEASON  Timothy D. SWINDLE  Kunihiko NISHIIZUMI  Marc W. CAFFEE  Dolores H. HILL  A. J. Timothy JULL  William V. BOYNTON 《Meteoritics & planetary science》2003,38(12):1833-1848

Abstract— Antarctic meteorite Queen Alexandra Range (QUE) 94201 is a 12 g basaltic achondrite dominated by plagioclase (now maskelynite) and zoned low‐ and high‐Ca pyroxene. Petrologic, geochemical, and isotopic analyses indicate that it is related to previously described basaltic and Iherzolitic shergottites, which are a group of igneous meteorites that are believed to be from Mars. Unlike previous shergottites, however, QUE 94201 represents a bulk melt rather than a cumulate fraction, meaning it can be used to infer magmatic source regions and the compositions of other melts on Mars. This melt has much more Fe and P than basaltic melts produced on Earth and formed at a much lower oxygen fugacity. This has altered the crystallization sequence of the melt, removing olivine from the liquidus to produce a plagioclase and 2‐pyroxene assemblage. If the high‐phosphorus and low‐oxygen fugacity conditions represented by QUE 94201 are common in magmatic regions of Mars, then olivine may be rare in marrian basalts. No solar cosmic ray effects were seen in the concentrations of ¹⁰Be, ²⁶A1, and ³⁶C1 with depth in the meteorite, implying at least 3 cm of ablation during entry to Earth. Significant excesses of neutron capture noble gas isotopes (^80,82Kr and ^128,131Xe) suggest that the QUE 94201 sample came from a depth >22 cm in a meteoroid of at least that radius. The meteorite also has very low ²¹Ne/²²Ne, which would often be interpreted to mean little ablation (contradicting above evidence) but, in this case, appears to reflect a very low abundance of Mg (the principal target element for Ne) in the meteorite, consistent with our bulk chemical analyses. The meteorite has a terrestrial ³⁶C1 age of 0.29 ± 0.05 Myr and a ¹⁰Be exposure age of 2.6 ± 0.5 Myr in a 47π geometry, implying an ejection age of 2.9 ± 0.5 Myr.  相似文献   

Cosmic‐ray exposure age and preatmospheric size of the Bunburra Rockhole achondrite     

Kees C. WELTEN  Matthias M. M. MEIER  Marc W. CAFFEE  Matthias LAUBENSTEIN  Kunihiko NISHIZUMI  Rainer WIELER  Phil A. BLAND  Martin C. TOWNER  Pavel SPURNÝ 《Meteoritics & planetary science》2012,47(2):186-196

Abstract– Bunburra Rockhole is the first meteorite fall photographed and recovered by the Desert Fireball Network in Australia. It is classified as an ungrouped achondrite similar in mineralogical and chemical composition to eucrites, but it has a distinct oxygen isotope composition. The question is if achondrites like Bunburra Rockhole originate from the same parent body as the howardite‐eucrite‐diogenite (HED) meteorites or from several separate, differentiated parent bodies. To address this question, we measured cosmogenic radionuclides and noble gases in the Bunburra Rockhole achondrite. The short‐lived radionuclides ²²Na and ⁵⁴Mn confirm that Bunburra Rockhole is a recent fall. The concentrations of ¹⁰Be, ²⁶Al and ³⁶Cl as well as the ²²Ne/²¹Ne ratio indicate that Bunburra Rockhole was a relatively small object (R approximately 15 cm) in space, consistent with the photographic fireball observations. The cosmogenic ³⁸Ar concentration yields a cosmic‐ray exposure (CRE) age of 22 ± 3 Myr, whereas ²¹Ne and ³He yield approximately 30% and approximately 60% lower ages, respectively, due to loss of cosmogenic He and Ne, mainly from plagioclase. With a CRE age of 22 Myr, Bunburra Rockhole is the first anomalous eucrite that overlaps with the main CRE peak of the HED meteorites. The radiogenic K‐Ar age of 4.1 Gyr is consistent with the U‐Pb age, while the young U,Th‐He age of approximately 1.4 Gyr indicates that Bunburra Rockhole lost radiogenic ⁴He more recently.  相似文献   

Development of polygon shift method for generating 3D view map of buildings     

Shunji Murai  Vivarad Phonekeo  Kunihiko Ono  Shigetaka Yasue 《ISPRS Journal of Photogrammetry and Remote Sensing》1999,54(5-6)

The authors have developed a new method termed “Polygon Shift Method” that enables the generation of a 3D view map of a city with tall buildings with a simplified procedure to shift a polygon and check the overlap between the original and shifted polygon. Boolean operations are applied with a newly defined “Fore or Aft” side and a “Depth Distance” that functionally express the visibility criteria or hidden point processing in the 3D view. Since the polygon shift method can be operated with a raster-based structure, the computer processing for generation of a 3D view map of buildings with shadow is simple and efficient.  相似文献   

洪湖人类活动的沉积物记录   总被引：4，自引：0，他引：4  

陈萍  何报寅  远藤邦彦  杜耘  李世杰 《湖泊科学》2004,16(3):233-237

对洪湖150cm长的沉积物样芯进行了TOC、TN、TP、Ca、硫化物测试和AMS定年,在此基础上对洪湖地区人类活动的湖泊沉积响应进行了讨论.TOC和TN的含量呈现相似的变化规律,它们在样芯顶部和底部都出现显著峰值,而中部变化平坦,表示1500年来洪湖环境变演的三个显著不同的阶段;TP从过去到现在总体呈上升的趋势,但上升的幅度不大,这与磷在沉积物中复杂的循环机制有关;Ca的剖面变化显示为底部含量高上部低,其变化情况较复杂;硫化物在顶部15cm的含量比背景值略高,可能指示了上个世纪人类对铁矿和矿物燃料开采强度的增大.  相似文献   

A neutron capture study of the Jilin chondrite     

Hiroshi HIDAKA  Shigekazu YONEDA  Kunihiko NISHIIZUMI 《Meteoritics & planetary science》2010,45(12):1973-1981

Abstract– The isotopic compositions of Sm and/or Gd of nine documented drill core samples of the Jilin H5 chondrite were determined to study the neutron capture records of individual meteorite samples. All the samples showed significant isotopic shifts of ¹⁵⁰Sm/¹⁴⁹Sm and/or ¹⁵⁸Gd/¹⁵⁷Gd corresponding to neutron fluences of (1.3–1.7) × 10¹⁵ n cm^?2. Considering the short 4π irradiation age of 0.32 Ma during the second stage, the 2π irradiation of 7 Ma during the first stage is the main influence on the Sm and Gd isotopic shifts of the Jilin chondrite. Although a depth dependence of the neutron capture effects was expected from the isotopic variations of ¹⁵⁰Sm/¹⁴⁹Sm and ¹⁵⁸Gd/¹⁵⁷Gd in the Jilin chondrite core samples that were possibly drilled perpendicular to the surface of the large object with a radius of >10 m in the 2π‐geometry, no clear evidence was observed in this study. The data from the combination of the isotopic shifts between Sm and Gd defined as ε_Sm/ε_Gd suggest that the neutrons produced in the 2π‐geometry of the Jilin chondrite follow the similar energy spectra as the neutrons in lunar samples, although the present analytical quality is not enough to discuss a critical discussion for the thermalization of the neutron energy levels.  相似文献   

Exposure history of separated phases from the Kapoeta meteorite     

Marc W. CAFFEE  Kunihiko NISHIIZUMI 《Meteoritics & planetary science》2001,36(3):429-437

Abstract— The cosmogenic radionuclides, ¹⁰Be, ²⁶Al, ³⁶Cl, and ⁵³Mn were measured in selected clasts and matrix samples from the howardite Kapoeta. Previous measurements of cosmogenic ²¹Ne indicate higher cosmic‐ray exposure ages for bulk samples than for some separated clasts or mineral separates. A possible interpretation for this difference in apparent exposure ages is a complex recent exposure history for Kapoeta. In this scenario some constituents are exposed to cosmic rays in a 2π geometry as part of a larger body immediately preceding its 4π exposure in a smaller body. To test this scenario we measured cosmogenic radionuclides in several clasts from Kapoeta. These measurements are consistent with a simple single‐stage 4π exposure history during which the entire inventory of cosmogenic radionuclides was produced. Taken together, these data are most consistent with a single‐stage 4π exposure lasting ～3 Ma. This scenario is nevertheless consistent with models in which the exposure of some constituents of Kapoeta to energetic particles occurred at an earlier time, as is indicated by ²¹Ne measurements. However, from our data we conclude that insubstantial quantities of cosmogenic radionuclides were inherited from this earlier irradiation; this earlier exposure to energetic particles must have predated the recent exposure by at least ～10 Ma to allow for the decay of the long half‐life cosmogenic radionuclides.  相似文献