Late Quaternary faulting along the western margin of the Poronaysk Lowland in central Sakhalin, Russia     

Hiroyuki Tsutsumi  Yasuhiro Suzuki  Andrei I. Kozhurin  Mihail I. Strel'tsov  Takeyuki Ueki  Hideaki Goto  Koji Okumura  Rustam F. Bulgakov  Hiroyuki Kitagawa 《Tectonophysics》2005,407(3-4):257-268

Sakhalin Island straddles an active plate boundary between the Okhotsk and Eurasian plates. South of Sakhalin, this plate boundary is illuminated by a series of M_w 7–8 earthquakes along the eastern margin of the Sea of Japan. Although this plate boundary is considered to extend onshore along the length of Sakhalin, the location and convergence rate of the plate boundary had been poorly constrained. We mapped north-trending active faults along the western margin of the Poronaysk Lowland in central Sakhalin based on aerial photograph interpretation and field observations. The active faults are located east of and parallel to the Tym–Poronaysk fault, a terrane boundary between Upper Cretaceous and Neogene strata; the active faults appear to have reactivated the terrane boundary at depth in Quaternary time. The total length of the active fault zone on land is about 140 km. Tectonic geomorphic features such as east-facing monoclinal and fault scarps, back-tilted fluvial terraces, and numerous secondary faults suggest that the faults are west-dipping reverse faults. Assuming the most widely developed geomorphic surface in the study area formed during the last glacial maximum at about 20 ka based on similarities of geomorphic features with those in Hokkaido Island, we obtain a vertical component of slip rate of 0.9–1.4 mm/year. Using the fault dip of 30–60°W observed at an outcrop and trench walls, a net slip rate of 1.0–2.8 mm/year is obtained. The upper bound of the estimate is close to a convergence rate across the Tym–Poronaysk fault based on GPS measurements. A trenching study across the fault zone dated the most recent faulting event at 3500–4000 years ago. The net slip associated with this event is estimated at about 4.5 m. Since the last faulting event, a minimum of 3.5 m of strain, close to the strain released during the last event, has accumulated along the central portion of the active strand of the Tym–Poronaysk fault.  相似文献   

Effective time-domain soil-structure interaction analysis based on FFT algorithm with causality condition     

Yasuhiro Hayashi  Hiroshi Katukura 《地震工程与结构动力学》1990,19(5):693-708

We propose an effective and reliable time-domain substructure technique which takes soil-structure interaction effects into account and uses the flexibility coefficients of unbounded soil obtained in the frequency domain. Compared with previous methods, the frequency points to calculate flexibility coefficients, and computational loads in the calculation of time-domain interaction forces, are reduced. In the formulation, we have assumed the flexibility coefficient to be a periodic function, obtained within the bandlimited frequency range, which also includes the predominant frequencies of the structure and incident wave. Then we simulate the periodic flexibility coefficients using discrete impulse responses in the time-domain analyses. However, the real and imaginary parts of the bandlimited flexibility coefficients do not form a Hilbert transform pair; the discrete impulse responses should be modified to be causal for the time-domain analyses. We present various discrete impulse responses which have been obtained from only the real part, only the imaginary part and from both the real and imaginary parts of the frequency-domain flexibility coefficients by FFT with causality conditions. Through a numerical example the relationship between the modified discrete impulse responses and the validity of the time-domain substructure method is presented.  相似文献   

Analysis of saturated dense sand-structure system and comparison with results from shaking table test     

Kiyoshi Fukutake  Akira Ohtsuki  Masayoshi Sato  Yasuhiro Shamoto 《地震工程与结构动力学》1990,19(7):977-992

An effective stress method is presented for the analysis of liquefaction of ground including soil-structure interaction, based on an explicit-implicit finite element method. A simple constitutive model is developed to be incorporated in the effective stress method. The constitutive model consists of the Ramberg-Osgood model extended to two-dimensional problems and a new dilatancy model. The effectiveness of the constitutive model is examined with results of a simple shear test. Besides, the effective stress method is verified by comparing its numerical results with results of a shaking table test. It is found that the present method can simulate well the response of a saturated dense sand-structure system. The difference of the response computed by the effective stress method and the total stress method is discussed. It is found that the total stress method can simulate the response of the saturated sand within an accumulating excess pore water pressure of less than 70 per cent of the initial overburden stress.  相似文献   

A Simple Method for Precise Determination of 23 Trace Elements in Granitic Rocks by ICP-MS after Lithium Tetraborate Fusion   总被引：1，自引：0，他引：1  

Shunsaku Awaji    Kentaro Nakamura  Tatsuo Nozaki  Yasuhiro Kato 《Resource Geology》2006,56(4):471-478

Abstract. An improved alkali fusion method followed by HF-HNO₃-HC1O₄ treatment is performed for simultaneous determination of 23 trace elements (Sr, Y, Zr, Nb, Ba, Hf, Ta, Th, U, and REE) by ICP-MS in rock reference materials: basaltic rocks (JB-2, JB-3) and granitic rocks (JG-la, JG-2, JG-3). Our improved method offers several advantages including: (1) suppression of whitish precipitates probably composed of insoluble fluorides by addition of HCIO4, (2) simple and reliable preparation procedure, (3) instrument calibration which enables straightforward simultaneous multi-elemental analysis, and (4) the very low background levels by using pure lithium tetraborate flux. We obtained the analytical results with a reproducibility of mostly <2 % (1) for the basaltic rocks and <7 % for the granitic rocks. The higher relative standard deviation (RSD) values for granitic rocks may be attributed to sample heterogeneity of coarse-grained granitic rocks. The analytical results of the granitic rocks demonstrate that Zr and Hf abundances are consistent with the compiled values and that REE concentrations agree well with recently published data, suggesting that the Li₂B₄O₇ fusion method applied in the present study is suitable for the analysis of the granitic rocks.  相似文献   

Whole-rock Geochemistry of Basic Schists from the Besshi Area, Central Shikoku: Implications for the Tectonic Setting of the Besshi Sulfide Deposit     

Tatsuo Nozaki    Kentaro Nakamura  Shunsaku Awaji  Yasuhiro Kato 《Resource Geology》2006,56(4):423-432

Abstract. Whole-rock chemical compositions of the Besshi basic schist closely associated with the Besshi massive sulfide deposit from the Sanbagawa Belt are reported. Studied samples were collected from four outcrops around the Dozan-goe, central Shikoku. Common metamorphic mineral assemblage of the basic schist is albite + epidote + actinolite + chlorite ± muscovite ± quartz. Major element contents are similar to those of typical tholeiitic basalts. Trace element patterns of the basic schist normalized to normal mid-ocean ridge basalt (N-MORB) are generally flat, although concentrations of highly mobile large-ion lithophile elements are quite variable. Chondrite-normalized rare earth element (REE) patterns are flat to slightly light REE-depleted patterns. In the Hf-Th-Ta and Nb-Zr-Y discrimination diagrams, basic schist samples closely associated with the sulfide deposit are plotted within the N-MORB field. The Th/Nb ratios of the basic schist are also comparable to those of N-MORB. These geo-chemical lines of evidence indicate that the protolith of the Besshi basic schist is N-MORB and the Besshi sulfide deposit was formed by hydrothermal activity in conjunction with MOR volcanism.  相似文献   

Spatio-temporal estimation of shallow landslide hazard triggered by rainfall using a three-dimensional model     

Cheng Qiu  Tetsuro Esaki  Mowen Xie  Yasuhiro Mitani  Chunxiang Wang 《Environmental Geology》2007,52(8):1569-1579

A shallow landslide triggered by rainfall can be forecast in real-time by modeling the relationship between rainfall infiltration and decrease of slope stability. This paper describes a promising approach that combines an improved three-dimensional slope stability model with an approximate method based on the Green and Ampt model, to estimate the time–space distribution of shallow landslide hazards. Once a forecast of rainfall intensity and slope stability-related data, e.g., terrain and geology data, are acquired, this approach is shown to have the ability to estimate the variation of slope stability of a wide natural area during rainfall and to identify the location of potential failure surfaces. The effectiveness of the estimation procedures described has been tested by comparison with a one-dimensional method and by application to a landslide-prone area in Japan.  相似文献   

On the importance of accurately ray-traced troposphere corrections for Interferometric SAR data     

Thomas Hobiger  Youhei Kinoshita  Shingo Shimizu  Ryuichi Ichikawa  Masato Furuya  Tetsuro Kondo  Yasuhiro Koyama 《Journal of Geodesy》2010,84(9):537-546

Numerical weather models offer the possibility to compute corrections for a variety of space geodetic applications, including remote sensing techniques like interferometric SAR. Due to the computational complexity, exact ray-tracing is avoided in many cases and mapping approaches are applied to transform vertically integrated delay corrections into slant direction. Such an approach works well as long as lateral atmospheric gradients are small enough to be neglected. But since such an approximation holds only for very rare cases it is investigated how horizontal gradients of different atmospheric constituents can evoke errors caused by the mapping strategy. Moreover, it is discussed how sudden changes of wet refractivity can easily lead to millimeter order biases when simplified methods are applied instead of ray-tracing. By an example, based on real InSAR data, the differences of the various troposphere correction schemes are evaluated and it is shown how the interpretation of the geophysical signals can be affected. In addition, it is studied to which extend troposphere noise can be reduced by applying the exact ray-tracing solution.  相似文献   

Nitrate-nitrogen isotopic patterns in surface waters of the western and central equatorial pacific     

Chisato Yoshikawa  Yasuhiro Yamanaka  Takeshi Nakatsuka 《Journal of Oceanography》2006,62(4):511-525

To understand the processes transporting nitrate to the surface layer of the western and central equatorial Pacific, we measured the nitrogen isotopic ratio of nitrate (δ ¹⁵NO ₃ ⁻ ), which is a very useful tracer of the source of nitrate, above 200 m depth in this region in December 1999. δ ¹⁵NO ₃ ⁻ is higher (about 13.0‰) in the surface water than in the subsurface water (where it is about 6.5‰) due to isotopic fractionation during nitrate uptake by phytoplankton. The δ ¹⁵NO ₃ ⁻ value has a roughly linear relationship with the natural logarithm of nitrate concentration (ln[NO ₃ ⁻ ]). However, for values above 150 m depth, the intercept of this linear relationship varies with position from east to west. On the other hand, the data at 200 m depth at all observation stations are concentrated around a single point (ln[NO ₃ ⁻ ] = 2.5 and δ ¹⁵NO ₃ ⁻ = 6.5‰) and do not fit the linear relationships for the shallower values. To examine the meaning of the observed distributions of δ ¹⁵NO ₃ ⁻ and nitrate concentration we developed a box model including nitrogen and nitrogen isotopic cycles. By reproducing the observed relationship between δ ¹⁵NO ₃ ⁻ and nitrate concentration using this model we found that most nitrate is transported horizontally from the eastern equatorial Pacific. We also conducted case studies and investigated the effects of differences in pathways of nitrate transport on the distributions of δ ¹⁵NO ₃ ⁻ and nitrate concentration. From these studies we concluded that the observed linear relationships between δ ¹⁵NO ₃ ⁻ and ln[NO ₃ ⁻ ], having a common slope around 6‰ but different intercepts at each station, are evidence of the significant horizontal transport of nitrate to the surface water in this area.  相似文献   

Roles of Physical Processes in the Carbon Cycle Using a Simplified Physical Model     

Masahiko Fujii  Motoyoshi Ikeda  Yasuhiro Yamanaka 《Journal of Oceanography》2000,56(6):655-666

A simplified physical model is proposed in this article to describe differences among basins in substance distributions which were not well described by previous simplified models. In the proposed model, the global ocean is divided into the Pacific/Indian Ocean (PI), the Atlantic Ocean (AT), the Southern Ocean and the Greenland/Iceland/Norwegian Sea. The model is consisted of five physical parameters, namely the air-sea gas exchange, the thermohaline circulation, the horizontal and vertical diffusions, and the deep convection in the high-latitude regions. Individual values of these parameters are chosen by optimizing model distribution of natural ¹⁴C as a physical tracer. The optimal value for a coefficient of vertical diffusion in the low-latitude region is 7.5 × 10^–5 [m²s^–1]. Vertical transports by the Antarctic Bottom Water and the North Atlantic Deep Water are estimated at 1.0 Sv and 9.0 Sv. Global-mean air-sea gas exchange time is calculated at 9.0 years. Using these optimal values, vertical profiles of dissolved inorganic carbon without biological production in PI and AT are estimated. Oceanic responses to anthropogenic fluctuations in substance concentrations in the atmosphere induced by the industrialization and nuclear bomb are also discribed, i.e., the effects appear significantly in AT while a signal is extremely weak in PI. A time-delay term is effective to make the PI water older near the bottom boundary.  相似文献   

Characterization of Banded Iron Formations by Two-Dimensional XRF Imaging and XANES Analyses     

Masaya MATSUNAGA  Katsunori FUKUDA  Yasuhiro KATO  Izumi NAKAI 《Resource Geology》2000,50(1):75-81

Abstract: Synchrotron radiation-induced X–ray fluorescence (SR–XRF) and conventional X-ray fluorescence (XRF) analyses were applied to determine the distributions of iron, manganese, calcium, titanium, and silicon, and chemical forms of iron and trace manganese in three banded iron formation (BIF) samples. The XRF imagings on the weathered and altered BIF from the Cleaverville Formation (3. 3–3. 1 Gyr), Western Australia, showed redistributions of iron, calcium, and manganese with the disappearance of the primary bandings, while, in contrast, titanium preserved its primary depositional distribution. The XRF imagings on the BIF from the Hamersley Group (2. 5 Gyr), Western Australia, showed that manganese and titanium distribute originally at boundary region between the iron-rich mesoband and the silica-rich mesoband. The X-ray Absorption Near Edge Structure (XANES) analysis revealed that the chemical forms of manganese and iron well represent the rhythmic change of the bandings.  相似文献