Holocene beach deposits for assessing coastal uplift of the northeastern Boso Peninsula, Pacific coast of Japan     

Toru Tamura  Fumitoshi Murakami 《Quaternary Research》2010,74(2):227-234

This paper presents a case study that assessed spatial variations in the tectonic uplift rates of beach deposits in the relict Kujukuri strand plain, situated on the northeastern coast of the Boso Peninsula, eastern Japan. The southern Boso Peninsula is tilted downward to the northeast due to plate subduction along the Sagami Trough. However, the cause of the northeastern coast uplift creating the relict strand plain is unclear, due to the absence of a Holocene raised marine terrace sequence. Elevations and ages of beach deposits were collected from drilled cores and ground-penetrating radar profiles along three shore-normal sections in the southern Kujukuri strand plain. From this, alongshore variations in the relative sea level since the mid-Holocene could be seen. These corresponded to north-to-northeast downward tilting at a rate of 0.4 m/ka for an interval 10 km and are concordant with the longer term tilting of the last interglacial marine terrace surrounding the plain. Although it is difficult to assess shore-normal variations of uplift based on the present dataset, the recognized tilting apparently continues to the tilting of the southern Boso Peninsula, implying the Sagami Trough probably affects the uplift of the Kujukuri coast.  相似文献   

Why is Shirase Glacier turning its flow direction eastward?     

Kazuki Nakamura  Koichiro Doi  Kazuo Shibuya 《Polar Science》2007,1(2-4):63-71

We applied an image correlation method to Japanese Earth Resources Satellite-1 (JERS-1) synthetic aperture radar (SAR) data obtained from 1996 to 1998 to examine flow velocity within Shirase Glacier, Antarctica. From the grounding line to the downstream region of the glacier, the obtained ice-flow velocity was systematically higher on the western streamline than the eastern. The differences between the two streamlines were 0.31 km/a in 1996 and 0.37 km/a in 1998, significantly larger than the error estimate of 0.03 km/a. The direction of ice flow was about 312° at the grounding line and changed to 327° at 10 km, 346° at 20 km and 2° at 30 km downstream from the grounding line. The total accumulated deflection is 50° to the east. Under the assumption of the conservation of ice mass across the glacier, the observed eastward change in flow direction can be explained by an asymmetric deepening of bedrock topography, that is, across the 8 km width of the glacier, the eastern side is 50 m (10%) deeper than the western side. This eastward turning of flow direction appears to be accelerated by tributary inlets, that flow to the north and northeast at 60–75% of the velocity of inlets on the western streamline.  相似文献   

Natural and anthropogenic aquatic environmental changes reconstructed by paleolimnological analyses in Lake Kitaura,central Japan     

Tomonori Naya  Yoshihiro Tanimura  Yutaka Kanai  Fujio Kumon  Kazuo Amano 《Journal of Paleolimnology》2007,37(4):547-563

In order to assess the recent anthropogenic environmental changes in Lake Kitaura, central Japan, changes during the past few centuries were reconstructed from results of radiometric and tephrochlonological age determination, magnetic susceptibility measurements, total organic carbon analyses, total nitrogen analyses and fossil diatom analyses on a sediment core from the lake. A total of six major and sub-zones are recognized according to the diatom fossil assemblages, and we discuss aquatic environmental change in Lake Kitaura mainly based on these diatom assemblage change. Zone Ia and Zone Ib (older than AD 1707) are marine to brackish. In Zone IIa (AD␣1707–AD 1836), most of the brackish diatoms disappeared, and were replaced by freshwater species indicating a decrease in salinity. We interpret the salinity decrease in Zone I–IIa as a sea-level fall during the Little Ice Age. The salinity of the lake decreased to near freshwater conditions in Zone IIb (AD 1836–AD 1970), which could arise from alteration in River Tone or development of a sandspit in the mouth of River Tone in addition to sea-level change. In Zone IIIa (AD 1970–AD 1987), the diatom assemblage indicates a freshwater environment, and sedimentation rates increase rapidly. These changes reflect sedimentary environment change and an ecosystem transition due to the construction of the tide gate. In Zone IIIb (AD 1987–AD 2002), the diatom flux (valves cm⁻² y⁻¹) increased and species composition changed. The changes in Zone IIIb show a good agreement with limnological monitoring data gathered from the lake. These paleolimnological data suggest that the recent human-induced changes of the aquatic environment of the lake after the 1970s exceed rates during the period concerned in this study.  相似文献   

Fault induced permanent ground deformations: Experimental verification of wet and dry soil, numerical findings’ relation to field observations of tunnel damage and implications for design     

Jrgen Johansson  Kazuo Konagai 《Soil Dynamics and Earthquake Engineering》2007,27(10):938-956

Few building codes contains provisions fault surface ruptures and accompanying soil deformations which constitutes a great risk to human lives, buildings and infrastructure. A numerical and experimental comparison show a fair agreement of result. Analysis of “real” scale show the how water increases the incompressibility of wet soil causing shear deformations to become larger and conjugate ruptures to appear for reverse faults. Field observations and numerical analysis indicates that horizontal compression of soil surrounding underground structures should be taken into account in design.  相似文献   

Correcting the Smoothing Effect of Ordinary Kriging Estimates   总被引：2，自引：0，他引：2  

Jorge Kazuo Yamamoto 《Mathematical Geology》2005,37(1):69-94

The smoothing effect of ordinary kriging is a well-known dangerous effect associated with this estimation technique. Consequently kriging estimates do not reproduce both histogram and semivariogram model of sample data. A four-step procedure for correcting the smoothing effect of ordinary kriging estimates is shown to be efficient for the reproduction of histogram and semivariogram without loss of local accuracy. Furthermore, this procedure provides a unique map sharing both local and global accuracies. Ordinary kriging with a proper correction for smoothing effect can be revitalized as a reliable estimation method that allows a better use of the available information.  相似文献   

Quantitative assessment on the influence of heavy rainfall on the crystalline schist landslide by monitoring system -case study on Zentoku landslide, Japan   总被引：2，自引：1，他引：2  

Yong Hong  Hiromasa Hiura  Kazuo Shino  Kyoji Sassa  Hiroshi Fukuoka 《Landslides》2005,2(1):31-41

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.  相似文献   

Origin of the Palau and Yap trench-arc systems     

Kazuo Kobayashi 《Geophysical Journal International》2004,157(3):1303-1315

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Data archives of seismic fault-induced damage   总被引：1，自引：0，他引：1  

Kazuo Konagai   《Soil Dynamics and Earthquake Engineering》2005,25(7-10):559-570

The study of earthquake engineering requires an understanding of various processes by which structures are seriously damaged. For this, archiving available data in a systematic way will be quite necessary. Taskforces of both Japan Society of Civil Engineers (JSCE) and Japan Geotechnical Society (JGS), with a mission of establishing remedial measures for fault-inflicted damage to civil infrastructures, have been investigating previous examples of fault-related damages. Some of their important activities were further expanded as a subject of EqTAP project (Development of Earthquake and Tsunami Disaster Mitigation Technologies and Their Integration for the Asia-Pacific Region). This paper introduces some examples from the JSCE/JGS/EqTAP Data Archives, which can give some hints for rational remedial or design measures for civil-infrastructures whose constructions across faults were/are unavoidable.  相似文献   

Antiferromagnetic transition of fayalite under high pressure studied by Mössbauer spectroscopy     

Mitsuhiko Hayashi  Ichiro Tamura  Osamu Shimomura  Hiroshi Sawamoto  Haruki Kawamura 《Physics and Chemistry of Minerals》1987,14(4):341-344

Néel temperature (Tm _N of α-Fe₂SiO₄ (fayalite) was measured as a function of pressure by means of Mössbauer spectroscopy in the pressure range 0–16 Gpa. High pressure was generated using a clamp-type miniature diamond anvil cell which was inserted into a cryostat. The Néel temperature increased linearly with increasing pressure at a rate of dT _N /dp=2.2±0.2 K/GPa. The result is discussed on the basis of the model proposed for the magnetic structure of fayalite by Santoro et al. (1966). The observed dT _N /dp suggests that the superexchange interactions vary as the ?10/3 power of the volume while the volume dependence of the direct exchange interactions is positive and small.  相似文献   

Glacio-geophysical implication of an NNSS positioning in and around Syowa Station, East Antarctica     

Kazuo Shibuya 《Journal of Geodynamics》1986,6(1-4)

Utilization of the two-wave NNSS receiver drastically improved the positioning accuracy on the ice sheet of Antarctica. The NNSS positioning gives us 3 m three-dimensional convergence with 25 accepted satellite passes, and is most useful for the measurement of ice flow velocity. The flow velocity vectors along Route S-H-Z on Mizuho plateau, East Antarctica were obtained by estimating positional change of glaciological traverse stations after 7 years' interval. The transformation of the coordinate system was necessary before the comparison of the positioning in 1973 by the geodetic traverse method on the Bessel Reference Ellipsoid with that in 1980 by the satellite Doppler method on the NWL-8E Ellipsoid. NNSS receiving experiments at astronomical datum point in Syowa Station enabled us to estimate the translation of the coordinate origin of the Bessel Reference Ellipsoid against the geocentric NWL-8E Ellipsoid and correction terms for coordinate transformation. The obtained flow velocity is 15 m/a at H17 of around 1000 m a.s.l. and 70 m/a at Z2 of around 2000 m a.s.l. with ±6% uncertainty, and is too large to be explained only by the laminar flow of the ice sheet. The obtained velocity vectors are found to be mostly parallel to the maximum slope of the free-air gravity anomaly contours and can be interpreted as the ice sheet sliding down the slope of the subglacial mound of 2400 m relative height from the average subglacial bedrock topography. If such bedrock sliding occurrs over the whole region of Mizuho Plateau, the related thinning of the ice sheet may be detected by the precise measurement of the height change of the same marker station. By dynamically modelling the ice sheet and substituting the observed parameters such as precipitation, principal strain rate, etc., into the equation of ice thickness change the submergence velocity of around −1 m/a is expected and will be detected by carefully designed repetitive NNSS receiving experiments after several year's interval.  相似文献