上海65 m口径射电望远镜方位轨道力学分析

对上海65 m口径射电望远镜方位轨道进行了静态力学分析。用温克尔弹性地基梁模型对轨道承载弯矩及地基受力作了估算,用赫兹接触理论对滚轮与轨道接触面的接触应力作了分析计算,为合理选择轨道材料和制定轨道焊接工艺方案提供了设计理论依据。     

Petrogenetic implications and geochronology of middle Miocene Tannayama igneous rocks,Goto Islands,Japan Sea southern margin,northwestern Kyushu,Japan

The subduction of “hot” Shikoku Basin and the mantle upwelling related to the Japan Sea opening have induced extensive magmatism during the middle Miocene on both the back-arc and island-arc sides of southwest Japan. The Goto Islands are located on the back-arc side of northwestern Kyushu, and middle Miocene granitic rocks and associated volcanic, hypabyssal, and gabbroic rocks are exposed. The igneous rocks at Tannayama on Nakadori-jima in the Goto Islands consist of gabbronorite, granite, granite porphyry, diorite porphyry, andesite, and rhyolite. We performed detailed geological mapping at a 1:10 000 scale, as well as petrographical and geochemical analyses. We also determined the zircon U–Pb age dating of the igneous rocks from Tannayama together with a granitic rock in Yagatamesaki. The zircon U–Pb ages of the Tannayama igneous rocks show the crystallization ages of 14.7 Ma ± 0.3 Ma (gabbronorite), 15.9 Ma ± 0.5 Ma (granite), 15.4 Ma ± 0.9 Ma (granite porphyry), and 15.1 Ma ± 2.1 Ma (rhyolite). Zircons from the Yagatamesaki granitic rock yield 14.5 Ma ± 0.7 Ma. Considering field relationships, new zircon data indicate that the Tannayama granite formed at ~16–15 Ma, and the gabbronorite, granite porphyry, diorite porphyry, andesite, and subsequently rhyolite formed at 15–14 Ma, which overlaps a plutonic activity of the Yagatamesaki. The geochemical characteristics of the Tannayama igneous rocks are similar to those of the tholeiitic basalts and dacites of Hirado, and the granitic rocks of Tsushima in northwestern Kyushu. This suggests that the Tannayama igneous rocks can be correlated petrogenetically with the igneous rocks in those areas, with all of them generated by the upwelling of hot mantle diapirs during crustal thinning in an extensional environment during the middle Miocene.     

Age and associated stress field of middle Miocene back-arc basalt magmatism in Northeast Japan

A large volume of middle Miocene basaltic rocks is widely distributed across the back-arc region of Northeast Japan, including around the Dewa Mountains. Petrological research has shown that basaltic rocks of the Aosawa Formation around the Dewa Mountains were generated as a result of the opening of the Sea of Japan. To determine the precise ages of the middle Miocene basaltic magmatism, we conducted U–Pb and fission-track (FT) dating of a rhyolite lava that constitutes the uppermost part of the Aosawa Formation. In addition, we estimated the paleostress field of the volcanism using data from a basaltic dike swarm in the same formation. The rhyolite lava yields a U–Pb age of 10.73 ±0.22 Ma (2σ) and a FT age of 10.6 ±1.6 Ma (2σ), and the paleostress analysis suggests a normal-faulting stress regime with a NW–SE-trending σ₃-axis, a relatively high stress ratio, and a relatively high magma pressure. Our results show that the late Aosawa magmatism occurred under NW–SE extensional stress and ended at ~ 11 Ma.     

Geochemistry,geochronology, and zircon Hf isotopes of Late Jurassic–Early Cretaceous granitoids in the Xing'an Massif,NE China: Implication for the Late Mesozoic tectonic evolution and crustal growth

This paper presents new zircon U–Pb geochronological, Hf isotopic and whole-rock geochemical data for the granitic plutons in the Xing'an Massif, Northeast China, to constrain the Late Mesozoic tectonic evolution of the Mongol-Okhotsk Ocean and the Paleo-Pacific Ocean. The zircon U–Pb ages indicate that the granitoids emplaced during the Late Jurassic–Early Cretaceous. The granodiorites show an adakitic affinity with high Sr/Y ratios and low Yb (< 1.30 μg/g) contents. The monzogranites exhibit high SiO₂, low MgO contents, enrichment in LILEs (Rb, K, and Th), and depletion in HSFEs (Ta, Nb, Zr, P, and Ti). Petrological and geochemical features of these monzogranites suggest that they are highly fractionated I-type granitoids. In addition, the zircon ε_Hf(t) values and two-stage model ages (T_DM2 ) are in the range of +2.6 to +8.1 and 669–1011 Ma, respectively, indicating that primary magma was generated by partial melting of juvenile lower-crustal materials, and there was a significant crustal growth in the Phanerozoic in the Northeast China. Combined with the coeval granitoids widely exposed in the Xing'an Massif, we conclude that the Late Jurassic magma in Northeast China was generated in an extensional setting related to the closure of the Mongol-Okhotsk Ocean, but the Early Cretaceous magma was related to the subduction of the Paleo-Pacific Plate.     

Detection and monitoring of offshore oil seeps using ERS/ENVISAT SAR/ASAR data and seep-seismic studies in Krishna–Godavari offshore basin,India

An attempt has been made to use synthetic aperture radar (SAR) data for detection and monitoring of offshore oil seeps in the eastern offshore areas of the Krishna–Godavari Basin, which has been supplemented and correlated with collateral free-air gravity and seismic data. Images of the study area obtained from ENVISAT ASAR image mode were processed and analysed in detail. A number of natural oil seepages were identified and distinguished from pollution and biogenic slicks. These were subsequently studied using different parameters to assign various degrees of confidence. The repetitiveness of the identified seepages was studied and a total of five areas of seep repetitions had been recognized in the study area. The seeps that are repeated in images of different dates are more likely to be of natural origin than others. Simulation and modelling of a particular oil slick arising has been attempted over the Krishna–Godavari offshore using MIKE 21 software.     

Hydrological behaviour of a drained agricultural peat catchment in the tropics. 2: Time series transfer function modelling approach

Abstract

Transfer function models of the rainfall–runoff relationship with various complexities are developed to investigate the hydrological behaviour of a tropical peat catchment that has undergone continuous drainage for a long time. The study reveals that a linear transfer function model of order one and noise term of ARIMA (1,0,0) best represents the monthly rainfall–runoff relationship of a drained peat catchment. The best-fitted transfer function model is capable of illustrating the cumulative hydrological effects of the catchment when subjected to drainage. Transfer function models of daily rainfall–runoff relationships for each year of the period 1983–1993 are also developed to decipher the changes in hydrological behaviour of the catchment due to drainage. The results show that the amount of rain water temporarily stored in the peat soil decreased and the catchment has become more responsive to rainfall over the study period.

Editor Z.W. Kundzewicz; Associate editor D. Hughes

Citation Katimon, A., Shahid, S., Abd Wahab, A.K., and Shabri, A., 2013. Hydrological behaviour of a drained agricultural peat catchment in the tropics. 2: Time series transfer function modelling approach. Hydrological Sciences Journal, 58 (6), 1310–1325.     

Climate change impacts on groundwater hydrology – where are the main uncertainties and can they be reduced?

ABSTRACT

This paper assesses how various sources of uncertainty propagate through the uncertainty cascade from emission scenarios through climate models and hydrological models to impacts, with a particular focus on groundwater aspects from a number of coordinated studies in Denmark. Our results are similar to those from surface water studies showing that climate model uncertainty dominates the results for projections of climate change impacts on streamflow and groundwater heads. However, we found uncertainties related to geological conceptualization and hydrological model discretization to be dominant for projections of well field capture zones, while the climate model uncertainty here is of minor importance. How to reduce the uncertainties on climate change impact projections related to groundwater is discussed, with an emphasis on the potential for reducing climate model biases through the use of fully coupled climate–hydrology models.

Editor D. Koutsoyiannis; Associate editor not assigned     

Ant colony optimization of tuned mass dampers for earthquake oscillations of high-rise structures including soil–structure interaction

This paper investigates the optimized parameters for tuned mass dampers (TMDs) to decrease the earthquake vibrations of tall buildings; involving soil–structure interaction (SSI) effects. The time domain analysis based on Newmark method is employed in this study. To illustrate the results, Tabas and Kobe earthquakes data are applied to the model, and ant colony optimization (ACO) method is utilized to obtain the best parameters for TMD. The TMD mass, damping coefficient and spring stiffness are assumed as design variables, and the objective is to reduce both the maximum displacement and acceleration of stories. It is shown that how the ACO can be effectively applied to design the optimum TMD device. It is also indicated that the soil type greatly affects the TMD optimized parameters and the time response of structures. This study helps the researchers to better understanding of earthquake vibrations, and leads the designers to achieve the optimized TMD for high-rise buildings.