A dynamic model for the Iceland Plume and the North Atlantic based on tomography and gravity data   总被引：1，自引：0，他引：1  

Gabriele Marquart  Harro Schmeling 《Geophysical Journal International》2004,159(1):40-52

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On the effect of a low viscosity asthenosphere on the temporal change of the geoid—A challenge for future gravity missions     

Gabriele Marquart  Bernhard Steinberger  Karen Niehuus 《Journal of Geodynamics》2005,39(5):493

New satellite technology to measure changes in the Earth’s gravity field gives new possibilities to detect layers of low viscosity inside the Earth. We used density models for the Earth mantle based on slab history as well as on tomography and fitted the viscosity by comparison of predicted gravity to the new CHAMP gravity model. We first confirm that the fit to the observed geoid is insensitive to the presence of a low viscosity anomaly in the upper mantle as long as the layer is thin ( 200 km) and the viscosity reduction is less than two orders of magnitude. Then we investigated the temporal change in geoid by comparing two stages of slablet sinking based on subduction history or by advection of tomography derived densities and compared the spectra of the geoid change for cases with and without a low viscosity layer, but about equal fit to the observed geoid. The presence of a low viscosity layer causes relaxation at smaller wavelength and thus leads to a spectrum with relatively stronger power in higher modes and a peak around degrees 5 and 6. Comparing the spectra to the expected degree resolution for GRACE data for a 5 years mission duration shows a weak possibility to detect changes in the Earth’s gravity field due to large scale mantle circulation, provided that other causes of geoid changes can be taken into account with sufficient accuracy. A discrimination between the two viscosity cases, however, demands a new generation of gravity field observing satellites.  相似文献   

Estimating the effective elastic thickness of the lithosphere of the Iberian peninsula based on multitaper spectral analysis   总被引：1，自引：0，他引：1  

D. Gómez-Ortiz  R. Tejero  J. Ruiz  R. Babín-Vich  J. M. González-Casado 《Geophysical Journal International》2005,160(2):729-735

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Hydromechanical coupling in response to earthquakes: on the possible consequences for aftershocks   总被引：1，自引：0，他引：1  

Pierre Gavrilenko 《Geophysical Journal International》2005,161(1):113-129

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Response of active tectonics on the alluvial Baghmati River, Himalayan foreland basin, eastern India   总被引：1，自引：2，他引：1  

Vikrant Jain  R. Sinha 《Geomorphology》2005,70(3-4):339

Active tectonics in a basin plays an important role in controlling a fluvial system through the change in channel slope. The Baghmati, an anabranching, foothills-fed river system, draining the plains of north Bihar in eastern India has responded to ongoing tectonic deformation in the basin. The relatively flat alluvial plains are traversed by several active subsurface faults, which divide the area in four tectonic blocks. Each tectonic block is characterized by association of fluvial anomalies viz. compressed meanders, knick point in longitudinal profiles, channel incision, anomalous sinuosity variations, sudden change in river flow direction, river flow against the local gradient and distribution of overbank flooding, lakes, and waterlogged area. Such fluvial anomalies have been identified on the repetitive satellite images and maps and interpreted through DEM and field observations to understand the nature of vertical movements in the area. The sub-surface faults in the Baghmati plains cut across the river channel and also run parallel which have allowed us to observe the effects of longitudinal and lateral tilting manifested in avulsions and morphological changes.  相似文献   

Re-examination of the magnetic lineations of the Gascoyne and Cuvier Abyssal Plains, off NW Australia     

Masako S. Robb  Brian Taylor  Andrew M. Goodliffe 《Geophysical Journal International》2005,163(1):42-55

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Temporal and spatial cyclicity of accretion at slow-spreading ridges—evidence from the Reykjanes Ridge     

Christine Peirce  Alex Gardiner  Martin Sinha 《Geophysical Journal International》2005,163(1):56-78

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Upper Ocean Four-Dimensional Variational Data Assimilation in the Arabian Sea and Bay of Bengal     

Suneet Dwivedi  Atul Srivastava  Alok Kumar Mishra 《Marine Geodesy》2018,41(3):230-257

A regional ocean circulation model with four-dimensional variational data assimilation scheme is configured to study the ocean state of the Indian Ocean region (65°E–95°E; 5°N–20°N) covering the Arabian Sea (AS) and Bay of Bengal (BoB). The state estimation setup uses 10 km horizontal resolution and 5 m vertical resolution in the upper ocean. The in-situ temperature and salinity, satellite-derived observations of sea surface height, and blended (in-situ and satellite-derived) observations of sea surface temperature alongwith their associated uncertainties are used for data assimilation with the regionally configured ocean model. The ocean state estimation is carried out for 61 days (1 June to 31 July 2013). The assimilated fields are closer to observations compared to other global state estimates. The mixed layer depth (MLD) of the region shows deepening during the period of assimilation with AS showing higher MLD compared to the BoB. An empirical forecast equation is derived for the prediction of MLD using the air–sea forcing variables as predictors. The surface and sub-surface (50 m) heat and salt budget tendencies of the region are also investigated. It is found that at the sub-surface, only the advection and diffusion temperature and salt tendencies are important.  相似文献   

Geochemical and isotopic characterization of trace fossil infillings: New insights on tracemaker activity after the K/Pg impact event     

《Cretaceous Research》2016

Geochemical and isotopic analyses of the Cretaceous–Paleogene (K/Pg) boundary deposits were conducted at the Caravaca section (External Subbetic, southeast of Spain) in order to evaluate the recovery of the macrobenthic tracemaker community and the bioturbational disturbance. Samples from the infilling material of several lower Danian dark-colored trace fossils (Chondrites, Planolites, Thalassinoides and Zoophycos) located in the uppermost 8-cm of the light upper Maastrichtian strata, as well as samples from the host sedimentary rock of these trace fossils, were analyzed and compared with data from the lower Danian deposits. The values of element ratios indicative of extraterrestrial contamination (Cr/Al, Co/Al and Ni/Al) are higher in the infilling trace fossil material than in the upper Maastrichtian and lower Danian deposits, which suggests a contribution of the ejecta layer. Regarding the isotope composition, the δ¹³C values are lower in the infilling material than in the Maastrichtian host sedimentary rocks surrounding the traces, while the δ¹⁸O are higher in the infilling material. The geochemical and isotopic compositions of the infilling material evidence the unconsolidated character of the sediment, including the red boundary layer. Softground conditions confirm a relatively rapid recovery by the macrobenthic tracemaker community, starting a few millimeters above the K/Pg boundary layer. The mixture of the infilling material of the trace fossils moreover reveals a significant macrobenthic tracemaker activity affecting K–Pg boundary transition sediments that may have significantly altered original signatures.  相似文献   

天山南麓雷暴日短期预报研究     

柳志慧  王式功  尚可政  孔德兵  赵文婧  王昀 《沙漠与绿洲气象(新疆气象)》2016,10(2):43-49

利用阿克苏及邻近地区12个气象站1980—2013年雷暴资料,以及同期高空资料,统计了各站年均雷暴日数,对发生区域雷暴天气的环流形势进行分类,归纳出各型的入型指标。通过逐步回归法,建立阿克苏及邻近地区区域雷暴概率回归预报模型,并对2013年进行试预报。结果表明:(1)阿克苏及邻近地区区域雷暴的影响系统主要分为4类:巴湖低槽型、急流型、西北气流型和温度槽型。(2)对2002—2012年5—9月(共1683 d)历史资料进行判别,满足入型条件的样本数为876 d,消空率为48%;对2013年5—9月(共153 d)历史资料进行判别,入型样本数为80 d,消空率为48%。(3)对2002—2012年5—9月所有入型样本进行回代检验,平均准确率为72.0%(平均TS评分为30.1%);对2013年5—9月所有入型样本进行试预报,平均准确率为63.2%(平均TS评分为28.2%)。  相似文献