论重力归算

利用构造参考地球模型的观点解释重力归算的物理意义。通过对不同模型的比较表明,厘米级大地水准面的确定必须考虑地球内部质量分布的不均匀性，且密度数据的精度应达到0.001 g/cm ³。     

重力极潮的小波分析

分别分析Brussels台站的观测记录,首先扣除数据序列中的合成潮得到重力残差,接着用小波带通滤波器将残差滤波,得到256～512 d时间尺度上的序列,然后运用最小二乘法估算Chandler和周年项的潮汐因子.由于小波滤波器能更有效地消除仪器漂移,计算结果具有更小的均方差,更加可靠.     

Comment on " Volume of magma accumulation or withdrawal estimated from surface uplift or subsidence, with application to the 1960 collapse of Kīlauea volcano" by P. T. Delaney and D. F. McTigue

 In volcanoes that store a significant quantity of magma within a subsurface summit reservoir, such as Kīlauea, bulk compression of stored magma is an important mode of deformation. Accumulation of magma is also accompanied by crustal deformation, usually manifested at the surface as uplift. These two modes of deformation – bulk compression of resident magma and deformation of the volcanic edifice – act in concert to accommodate the volume of newly added magma. During deflation, the processes reverse and reservoir magma undergoes bulk decompression, the chamber contracts, and the ground surface subsides. Because magma compression plays a role in creating subsurface volume to accommodate magma, magma budget estimates that are derived from surface uplift observations without consideration of magma compression will underestimate actual magma volume changes. Received: 30 September 1998 / Accepted: 27 July 1999     

Distribution and facies patterns of Lower Cretaceous sediments in northern Germany: a review

Marine sediments of Early Cretaceous age (Berriasian–Albian) have a widespread distribution in the Lower Saxony Basin of northern Germany. This basin, which is about 400 km long and 100 km wide, formed the southernmost extension of the North Sea Basin. Sediments attaining a maximum thickness of up to several hundred metres are represented by shallow marine siliciclastics in the west, south and easternmost part of the basin. These interfinger with the basin facies represented by dark mudstones up to 2000 m thick. The distribution and facies patterns of the sediments as well as thicknesses are related to three factors: differential subsidence, local tectonics and sea-level changes. For various parts of the basin and certain stratigraphic intervals it is possible to distinguish between these causes. Sedimentary thicknesses are clearly a result of differential subsidence from Kimmeridgian to Albian times onwards, being controlled by tectonic movements along northwest–southeast trending faults. These result in an asymmetric trough, bound to the north and south by synsedimentary faults with sedimentation rates highest in the north. Local tectonics are clearly caused by salt diapirs mainly in the eastern part of the basin and along the western, southern and eastern margins. These areas in particular include parts of the western Emsland and the Salzgitter area. Sedimentary patterns vary considerably over less than a kilometre, showing an extreme range of different lithologies. This is ideally observed in the Salzgitter area. Sea-level changes finally are reflected by widespread facies patterns and particularly by fossils of different provenance. The following sea-level-related events can be followed throughout the basin: the Wealden regressive phase, the Early Valanginian transgression, the early Late Valanginian transgression, the mid Hauterivian transgression, the Barremian regression, deposition of the Early Aptian anoxic sediments, and accumulation of the mid Albian hemipelagic marls.     

Arsenic toxicity of groundwater in parts of the Bengal basin in India and Bangladesh: the role of Quaternary stratigraphy and Holocene sea-level fluctuation

 Arsenic toxicity in groundwater in the Ganges delta and some low-lying areas in the Bengal basin is confined to middle Holocene sediments. Dissected terraces and highlands of Pleistocene and early Holocene deposits are free of such problems. Arsenic-rich pyrite or other arsenic minerals are rare or absent in the affected sediments. Arsenic appears to occur adsorbed on iron hydroxide-coated sand grains and clay minerals and is transported in soluble form and co-precipitated with, or is scavenged by, Fe(III) and Mn(IV) in the sediments. It became preferentially entrapped in fine-grained and organic-rich sediments during mid-Holocene sea-level rises in deltaic and some low-lying areas of the Bengal basin. It was liberated subsequently under reducing conditions and mediated further by microbial action. Intensive extraction of groundwater for irrigation and application of phosphate fertilizer possibly triggered the recent release of arsenic to groundwater. This practice has induced groundwater flow, mobilizing phosphate derived from fertilizer, as well as from decayed organic matter, which has promoted the growth of sediment biota and aided the further release of arsenic. However, the environment is not sufficiently reducing to mobilize iron and arsenic in groundwater in the Ganges floodplains upstream of Rajmahal. Thus, arsenic toxicity in the groundwater of the Bengal basin is caused by its natural setting, but also appears to be triggered by recent anthropogenic activities. Received: 23 August 1999 · Accepted: 16 November 1999     

由PREM模型参数计算地球自转的周期变化

弹性地球在日月引潮力势作用下的形变引起其转动惯量的改变，从而导致地球自转速率的变化．本文利用PREM地球模型所给的物质密度和弹性等参数分布．计算日月引潮力势产生的地球形变附加势，进而计算转动惯量的变化．最后得到一系列包含周期同引潮势带谐项、振幅大于1微秒的自转速率周期变化系数．     

Effects of anthropogenic intervention in the land hydrologic cycle on global sea level rise

Recent studies suggest that anthropogenic modification of land hydrology (e.g. through groundwater mining, dam building, irrigation, deforestation, wetlands drainage, and urbanization) could significantly impact sea-level rise, although the magnitude and sign of this effect have been widely debated. This paper attempts a comprehensive overview of the effects of human activities on land hydrology. Estimates are provided for the volumes of water associated with each of the major anthropogenic processes and the corresponding equivalent in sea level.Groundwater mining; and runoff from paved and built-up areas are two major sources of water added to the ocean. In contrast, storage of water behind dams, losses through percolation, and evapotranspiration from irrigated fields withhold water that would otherwise flow to the sea. The net effect of these processes holds back the equivalent of 0.8 +- 0.4 mm/yr from sea-level rise. This is a magnitude comparable to, but in the opposite direction from the currently observed sea-level rise of 1–2 mm/yr. These estimates are still preliminary, awaiting better documentation. Coupling of improved land hydrology models with GCMs will help in analysis of feedbacks, especially the partitioning of water among runoff, infiltration, and evaporation.     

A review of the environmental history of Iceland, 13 000-9000 yr BP

A synthesis of the main environmental changes that are interpreted to have occurred in Iceland during the period 13-9 ka BP is presented. Most of the evidence available relates to variations in the position of ice margins, although some limited information on vegetation history and soil stability is also referred to. Only qualitative and limited climatic inferences can be made for this period because of the lack of detailed evidence. A summary curve of the relative extent of ice cover is presented.