Kalman filter finite element method applied to dynamic ground motion     

Yusuke Kato  Mutsuto Kawahara  Naoto Koizumi 《国际地质力学数值与分析法杂志》2009,33(9):1135-1151

The purpose of this paper is to investigate the estimation of dynamic elastic behavior of the ground using the Kalman filter finite element method. In the present paper, as the state equation, the balance of stress equation, the strain–displacement equation and the stress–strain equation are used. For temporal discretization, the Newmark ¼ method is employed, and for the spatial discretization the Galerkin method is applied. The Kalman filter finite element method is a combination of the Kalman filter and the finite element method. The present method is adaptable to estimations not only in time but also in space, as we have confirmed by its application to the Futatsuishi quarry site. The input data are the measured velocity, acceleration, etc., which may include mechanical noise. It has been shown in numerical studies that the estimated velocity, acceleration, etc., at any other spatial and temporal point can be obtained by removing the noise included in the observation. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Characteristics of an atypical large-meander path of the Kuroshio current south of Japan formed in September 2017     

Nagano  Akira  Yamashita  Yusuke  Hasegawa  Takuya  Ariyoshi  Keisuke  Matsumoto  Hiroyuki  Shinohara  Masanao 《Marine Geophysical Researches》2019,40(4):525-539

Since September 2017, the Kuroshio has taken a large-meander (LM) path in the region south of Japan. We examined characteristics of the 2017–present LM path in comparison with previous LM paths, using tide gauge, altimetric sea surface height, and bottom pressure data. The 2017–present LM path was formed from a path passing through a channel south of Hachijo-jima Island, while a typical LM path originated from a path through a channel north of Miyake-jima Island. The meander trough of this atypical path was found to be shifted far to the east and to vary on a timescale of months. These characteristics are different from those of a typical LM path but they are similar to those of the 1981–1984 LM path. Therefore, we identified two types of LM path; a stable and unstable LM paths. The 2017–present unstable type large meander has a zonal scale greater than that of the 2004–2005 stable type large meander and protrudes from the eastern boundary of the Shikoku Basin, i.e., Izu-Ogasawara Ridge. No significant bottom pressure depression was observed, associated with the formation of the 2017–present LM path, indicating that baroclinic instability was not important in the formation of this LM path. Due to no significant bottom steering, even during the 2017–present LM period, a mesoscale current path disturbance occurred southeast of Kyushu, propagated eastward, and amplified the offshore displacement of the Kuroshio.

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U–Pb zircon geochronology of the North Pole Dome adamellite in the eastern Pilbara Craton          下载免费PDF全文

Hisashi Asanuma  Yusuke Sawaki  Shuhei Sakata  Hideyuki Obayashi  Kazue Suzuki  Kouki Kitajima  Takafumi Hirata  Shigenori Maruyama 《Island Arc》2018,27(4)

Supracrustal rocks around the North Pole Dome area, Western Australia, provide valuable information regarding early records of the evolution of crustal processes, surface environments, and biosphere. Owing to the occurrence of the oldest known microfossils, the successions at the North Pole Dome area have attracted interest from many researchers. The Paleoarchean successions (Warrawoona Group) mainly comprise mafic‐ultramafic greenstones with intercalated cherts and felsic lavas. Age constraints on the sediments have been mainly based on zircon U–Pb geochronology. However, many zircon grains have suffered from metamictization and contain anomalously high contents of common Pb, which makes interpretation of the U–Pb data complicated. In order to provide more convincing chronological constraints, an U–Pb Concordia age is widely accepted as the best estimate. Most zircons separated from two adamellites also suffered from severe metamictization. In our analyses, less metamictized domains were selected using a pre‐ablation technique in conjunction with elemental mapping, and then their U–Pb isotopic compositions were determined with a laser ablation inductively coupled plasma mass spectrometry. Most analyzed domains contained certain amounts of common Pb (²⁰⁴Pb/²⁰⁶Pb > 0.000 1), whereas three and five U–Pb data points with less common Pb (²⁰⁴Pb/²⁰⁶Pb < 0.000 1) were obtained. These U–Pb datasets yielded U–Pb Concordia ages of ca 3 445 Ma and 3 454 Ma, respectively. These ages represent the timing of the adamellite intrusion, and constrain the minimum depositional age of the Warrawoona Group. In addition, a single xenocrystic zircon grain showed a ²⁰⁷Pb/²⁰⁶Pb age of ca 3 545 Ma, supporting the idea that the sialic basement of the Pilbara Craton existed prior to 3 500 Ma. The in situ U–Pb zircon dating combined with the pre‐ablation technique has the potentials to identify non‐metamictized parts and to yield precise and accurate geochronological data even from partially metamictized zircons.  相似文献   

Geochemical characteristics of zircons in the Ashizuri A‐type granitoids: An additional granite topology tool for detrital zircon studies          下载免费PDF全文

Yusuke Sawaki  Kazue Suzuki  Hisashi Asanuma  Satoki Okabayashi  Kentaro Hattori  Takuya Saito  Takafumi Hirata 《Island Arc》2017,26(6)

Zircon is resistant to alteration over a wide range of geological environments, and isotopic ratios within the mineral provide constraints on ages and their parental magmas. Trace element compositions in zircon are also expected to reflect those of their parent magmas, and have a potential as essential indicators for their host rocks. Because most detrital zircons that accumulate at river mouths are derived primarily from granitoids, the classification of zircon within granitoids is potentially meaningful. This study employs the conventional classification scheme of granites (I‐, S‐, M‐, and A‐types). To clarify geochemical characteristics of zircons in A‐type granites, trace element compositions of zircons extracted from the A‐type Ashizuri granitoids were examined. Zircons from the Ashizuri granitoids commonly show enrichments of heavy rare earth elements and positive Ce anomalies, indicating that these zircons were igneous in origin. In addition, zircons in these A‐type granites are characterized by enrichments of Nb, Y, Ta, Th, and U and strong negative Eu anomalies, which exhibit good positive correlations with those in their whole rocks. This fact indicates that these signatures in zircons reflect well those in their parental bodies and are useful in identifying zircons derived from A‐type granite. Based on compilations of available data, zircons from A‐type granites can be clearly discriminated from other‐types of granites within Nb/Sr–Eu anomaly, U/Sr–Eu anomaly, Nb/Sr–U/Sr, and Nb/Sr–Ta/Sr cross‐plots. All indices used in these diagrams were selected based on the geochemical features of both zircon and whole rock of A‐type granites. Application of these discrimination diagrams to detrital zircons will likely provide further insights. For example, some Hadean detrital zircons plot in similar fields to A‐type granites, implying the existence of A‐type magmatism in the Earth's earliest history.  相似文献   

Development of collapse-consistent loading protocols for experimental testing of steel columns     

Yusuke Suzuki  Dimitrios G. Lignos 《地震工程与结构动力学》2020,49(2):114-131

In order to effectively utilize results from quasi-static cyclic testing on structural components for the earthquake-induced collapse risk quantification of structures, the need exists to establish collapse-consistent loading protocols representing the asymmetric lateral drift demands of structures under low-probability of occurrence earthquakes. This paper summarizes the development of such protocols for experimental testing of steel columns prone to inelastic local buckling. The protocols are fully defined with a deformation- and a force-controlled parameter. They are generally applicable to quantify the capacity and demands of steel columns experiencing constant and variable axial load coupled with lateral drift demands. Through rigorous nonlinear earthquake collapse simulations, it is found that the building height, the column's local slenderness ratio, and ground motion type have the largest influence on the dual-parameter loading protocol indexes. Comprehensive comparisons with measured data from full-scale shake table collapse tests suggest that unlike routinely used symmetric cyclic loading histories, the proposed loading protocol provides sufficient information for modeling strength and stiffness deterioration in steel columns at large inelastic deformations.  相似文献   

Interaction between cladding and structural frame observed in a full‐scale steel building test     

Taichiro Okazaki  Masayoshi Nakashima  Keiichiro Suita  Tomohiro Matusmiya 《地震工程与结构动力学》2007,36(1):35-53

Interaction between the external wall cladding and the seismic load resisting frame was examined in a full‐scale cyclic loading test of a three‐storey steel building structure. The building specimen had Autoclaved Lightweight Concrete (ALC, also designated as Autoclaved Aerated Concrete) panels installed and anchored to the structural frame as external wall cladding, using a standard Japanese method developed following the 1995 Kobe earthquake. ALC panelling is among the most widely used material for claddings in Japan. In the test, the ALC panel cladding contributed little to the stiffness and strength of the overall structure, even under a very large storey drift of 0.04 rad. No visible damage was noted in the ALC panels other than minor cracks and spalling of the bottom of the panels in the first storey. Consequently, in a Japanese steel building with properly installed ALC panel cladding, the structural frame is likely to be little affected by its cladding, and the ALC panels are capable of accommodating the maximum storey drift generally considered in structural design without sustaining discernible damage. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Viscous effects on the interaction between the coplanar decretion disc and the neutron star in Be/ X-ray binaries     

A. T. Okazaki  M. R. Bate  G. I. Ogilvie  J. E. Pringle 《Monthly notices of the Royal Astronomical Society》2002,337(3):967-980

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Biological production in meso-scale eddies caused by frontal disturbances of the Kuroshio Extension   总被引：1，自引：0，他引：1  

Kimura  Shingo; Nakata  Hideaki; Okazaki  Yuji 《ICES Journal of Marine Science》2000,57(1):133-142

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The Ediacaran radiogenic Sr isotope excursion in the Doushantuo Formation in the Three Gorges area,South China     

Yusuke Sawaki  Takeshi Ohno  Miyuki Tahata  Tsuyoshi Komiya  Takafumi Hirata  Shigenori Maruyama  Brian F. Windley  Jian Han  Degan Shu  Yong Li 《Precambrian Research》2010,176(1-4):46-64

The Ediacaran period was one of the most important times for the evolution of life. However, the scarcity of well-preserved outcrops of Ediacaran rocks still leaves ambiguity in decoding ambient surface environmental changes and biological evolution.The Ediacaran strata in South China are almost continuously exposed, comprise mainly carbonate rocks with subordinate black shales and sandstones, and they contain many fossils, suitable for study of environmental and biological changes in the Ediacaran. We conducted drilling through the Doushantuo Fm at four sites in the Three Gorges area to obtain continuous, fresh samples without surface alteration and oxidation. We analyzed ⁸⁷Sr/⁸⁶Sr and ⁸⁸Sr/⁸⁶Sr ratios of the fresh carbonate rocks, selected on the basis of microscopic observations and the geochemical signatures of Sr contents, Mn/Sr and Rb/Sr ratios, and δ¹⁸O values, with a multiple collector-inductively coupled plasma-mass spectrometer (MC-ICP-MS).The chemostratigraphy of the ⁸⁷Sr/⁸⁶Sr ratios of the drilled samples displays a smooth curve and two large positive shifts during Ediacaran time. The combination of the detailed chemostratigraphies of δ¹³C, δ¹⁸O and ⁸⁷Sr/⁸⁶Sr values and Mn and Fe contents enables us to decode the surface environmental changes and their causes in the Ediacaran. The first large positive excursion of ⁸⁷Sr/⁸⁶Sr occurred together with negative δ¹³C and positive δ¹⁸O excursions. The higher ⁸⁷Sr/⁸⁶Sr values indicate an enhancement of continental weathering, whereas the positive δ¹⁸O excursion suggests global cooling. Global regression due to global cooling enhanced the oxidative decay of exposed marine organic sediments and continental weathering. Accelerated influx of nutrients promoted primary productivity, resulting in oxidation of dissolved organic carbon (DOC), whereas active sulfate reduction due to a higher sulfate influx from the continents caused remineralization of the large DOC, both of which caused a negative δ¹³C anomaly. The 580 Ma Gaskiers glaciation accounts for the close correlation among the positive ⁸⁷Sr/⁸⁶Sr, negative δ¹³C and positive δ¹⁸O excursions.The second large positive shift of ⁸⁷Sr/⁸⁶Sr firstly accompanied a positive δ¹³C excursion, and continued through the Shuram δ¹³C negative excursion. The positive correlation of δ¹³C and ⁸⁷Sr/⁸⁶Sr values is consistent with an enhanced continental weathering rate due to continental collisions that built Trans-Gondwana mountain chains, and with a higher primary activity due to the enhancement of continental weathering and consequent higher nutrient contents in seawater. The accompanied increase in Mn and Fe contents implies a gradual decline of the seawater oxygen content due to more active aerobic respiration and oxidation of reductive materials flowing in the oceans. In the Shuram excursion, higher ⁸⁷Sr/⁸⁶Sr values and a transition from increase to decrease in Mn and Fe contents were accompanied by the large negative δ¹³C excursion. The higher ⁸⁷Sr/⁸⁶Sr values are the first compelling evidence for enhanced continental weathering, which was responsible for the large δ¹³C anomaly through the remineralization of the DOC by more active sulfate reduction due to a higher sulfate influx. Higher Mn and Fe contents in the early and middle stages of the excursion suggest a decline in the oxygen content of seawater due to oxidative decay of the DOC, whereas in the late stages the decrease in Mn and Fe contents is consistent with oceanic oxygenation.The emergence of Ediacara biota after the Gaskiers glaciation and the prosperity of the latest Ediacaran is concomitant with the formation of more radiogenic seawater with high ⁸⁷Sr/⁸⁶Sr values, suggesting that enhanced continental weathering, and the consequent higher influx of nutrients, played an important role in biological evolution.  相似文献   

Late Holocene marine terraces of the Cartagena region,southern Caribbean: The product of neotectonism or a former high stand in sea-level?     

J. Ignacio Martínez  Yusuke Yokoyama  Andres Gomez  Adriana Delgado  Hiroyuki Matsuzaki  Esteban Rendon 《Journal of South American Earth Sciences》2010,29(2):214-224

The detailed stratigraphic survey and paleontological study (mollusks, corals, foraminifera and ostracods) of four low-level, ～3 m, marine terrace sections: Punta Canoas, Manzanillo del Mar, Playa de Oro, and Tierra Bomba Island, from the Cartagena region, southern Caribbean, supplemented with 22 radiocarbon dates, reveals that the northern terraces were deposited as parasequences in a clastic depositional system compared to the Tierra Bomba Island succession that was deposited in a carbonate depositional system between ～3600 and ～1700 cal yrs BP. Drier conditions and the southern location of the ITCZ at about 3 ka triggered stronger easterly Trades and more dynamic southwestward sediment drift fed by the Magdalena River mouth, thus promoting the formation of sand spits that ultimately isolated the Cienaga de Tesca coastal lagoon from the Caribbean Sea. Our estimates support the hypothesis that the present position of the terraces is the product of neotectonism rather than a higher 3 ka, sea-level. Upheaval of the terraces varies between ～3.8 mmyr^?1 at Punta Canoas and ～2.2 mmyr^?1 at Tierra Bomba to ～1.5 mmyr^?1 at Manzanillo del Mar and Playa de Oro terraces. Our study corroborates previous contentions on the role of mud diapirism and the dynamics of the Dique Fault as late Holocene upheaval mechanisms.  相似文献