SORTAN: An Analytical Method to Determine Fault Slip as Induced by Stress

We propose an analytical method, namely the SORTAN method, to determine the sense of slip on faults as induced by stresses. This method is useful to infer the sense of motion along faults whose surface cannot be directly accessed, such as faults imaged in the subsurface. Because the SORTAN method is based on the Wallace–Bott hypothesis, we assume that the shear stress vector applied to a given fault is parallel to the slip vector on this fault. The assumptions allow for simplification of the method that in turn implies very short calculation times. A concise formalism is adopted. We introduce the stress ratio ' that accounts for (1) the type of stress regime (i.e., strike-slip, reverse or normal) and (2) the degree of anisotropy of the stress state. The formalism of the SORTAN method permits an easy exploration and imaging of the complete collection of slip motions that may theoretically occur on fault planes. The input parameters are the fault plane orientation, the type and anisotropy of the stress regime, and the azimuth of the horizontal stress axes.     

Soil frost effects on soil water and runoff dynamics along a boreal forest transect: 1. Field investigations

To determine how soil frost changes flowpaths of runoff water along a hillslope, a transect consisting of four soil profiles directed towards a small stream in a mature forest stand was investigated at Svartberget, near Vindeln in northern Sweden. Soil temperature, unfrozen water content, groundwater level and snow depth were investigated along the transect, which started at the riparian peat, and extended 30 m upslope into mineral soils. The two, more organic‐rich profiles closest to the stream had higher water retention and wetter autumn conditions than the sandy mineral soils further upslope. The organic content of the soil influenced the variation in frost along the transect. The first winter (1995–96) had abnormally low snow precipitation, which gave a deep frost down to 40–80 cm, whereas the two following winters had frost depths of 5–20 cm. During winter 1995–96, the two organic profiles close to the stream had a shallower frost depth than the mineral soil profile higher upslope, but a considerably larger amount of frozen water. The fraction of water that did not freeze despite several minus degrees in the soil was 5–7 vol.% in the mineral soil and 10–15 vol.% in the organic soil. From the measurements there were no signs of perched water tables during any of the three snowmelt periods, which would have been strong evidence for changed water flowpaths due to soil frost. When shallow soil layers became saturated during snowmelt, especially in 1997 and 1998, it was because of rising groundwater levels. Several rain on frozen ground events during spring 1996 resulted in little runoff, since most of the rain either froze in the soil or filled up the soil water storage. Copyright © 2001 John Wiley & Sons, Ltd.     

Hydraulic characteristics of a small Coastal Plain stream of the southeastern United States: effects of hydrology and season

Various physical and biological properties affect solute transport patterns in streams. We measured hydraulic characteristics of Payne Creek, a low‐gradient upper Coastal Plain stream, using tracer experiments and parameter estimation with OTIS‐P (one‐dimensional transport with inflow and storage with parameter optimization). The primary objective of this study was to estimate the effects of varying discharge, season, and litter accumulation on hydraulic parameters. Channel area A ranged from 0·081 to 0·371 m² and transient storage area A_s ranged from 0·027 to 0·111 m². Dispersion D ranged from 1·5 to 11·1 m² min⁻¹ and exchange coefficient α ranged from 0·009 to 0·038 min⁻¹. Channel area and dispersion were positively correlated to discharge Q, whereas storage area and exchange coefficient were not. Relative storage size A_s/A ranged from 0·17 to 0·59, and was higher during fall than other seasons under a similar Q. The fraction of median travel time due to transient storage ranged from 8·8 to 34·5% and was significantly correlated with Q through a negative power function. Both metrics indicated that transient storage was a significant component affecting solute transport in Payne Creek, especially during the fall. Comparison between the measured channel area A_c and A suggested that surface storage was dominant in Payne Creek. During fall, accumulation of leaf litter resulted in larger A and A_s and lower velocity and D than during other seasons with similar discharge. Seasonal changes in discharge and organic matter accumulation, and dynamic channel morphology affected the magnitude of transient storage and overall hydraulic characteristics of Payne Creek. Copyright © 2005 John Wiley & Sons, Ltd.     

南海夏季风期间海-气通量整体输送系数分析

利用 2 0 0 0年南海海 气通量观测资料 ,建立了南海季风期间海 气通量整体输送系数的计算公式 ;同时 ,利用2 0 0 0和 2 0 0 2年观测资料与邻近海区同类公式进行了对比试验研究。结果表明 ,使用邻近海区的同类公式计算的海 气通量的误差高于新建立公式所得结果。因此 ,开展南海海 气通量观测试验对建立适合于南海的整体输送系数的计算公式是必要的     

黑河中游非均匀地表能量通量的卫星遥感参数化

对黑河中游非均匀地表区域地表能量通量和蒸发(或蒸散)的研究是一个十分重要但又是一个难点问题。文中提出了2个基于卫星遥感和地面观测的参数化方案,并把其用于黑河中游地区。同时利用2个景的陆地资源卫星Landsat TM资料进行了分析研究,得到了一些有关非均匀地表的沙漠化地区的区域地表特征参数、植被参数和地表能量通量的新概念。文章最后还讨论了所提出的参数化方案的适用范围和所需的改进之处。     

Dissolved oxygen distribution and O2 fluxes across the sea-air interface in East China Sea waters

This study on the sectional and vertical distribution of dissolved oxygen (DO) and the O₂ fluxes across the sea-air interface in East China Sea (ESC) waters shows that the waters were in steady state and that the difference of DO was great in upper and bottom waters in Apr. 1994; but that seawater mixing was strong and the difference of DO was small in upper and bottom waters in Oct. 1994. The above conclusions were specially obvious in continental shelf waters under 100 m. The DO maximum in subsurface layer waters appeared only at several stations and in general the DO in the waters decreased with depth. The horizontal distributions of O₂ fluxes across the sea-air interface appeared in stripes in Leg 9404 when most regions covered were supersaturated with O₂ seawater to air flux was large, and that on section No. 1 was 1.594 L/m²·d. The horizontal distribution of O₂ fluxes across the sea-air interface appeared lumpy in Leg 9410, when most regions covered were unsaturated with O₂·O₂ was dissolved from air to seawater, and the fluxes were 0.819 L/m²·d on section No. 1 in Leg 9310, 0.219 L/m²·d in Leg 9410. The main reasons for DO change in surface layer seawater were the mixture of upper and bottom layer water, and the exchange of O₂ across the sea-air interface. The variation of DO by biological activity was only 20% of total change of DO. Contribution No. 2716 from Institute of Oceanology, Chinese Academy of Sciences.     

三峡井网地下流体动态在水库蓄水前后的变化

在系统分析长江三峡诱发地震地下水动态监测井网2001～2002年8个井台16个测项的地下流体正常动态及其影响因素的基础上，调查研究了井网外围50km范围内两个中等地震震例，对比分析了2003年三峡水库蓄水前后各测项动态的变化。发现水库蓄水对三峡井网地下流体动态的影响是局部的．推测三峡库首区近期诱发中等以上水库地震的可能性不大；同时分析了受水库蓄水影响测项的异常特征及其机理，认为深入研究此类问题对推进地震监测与预报科学的发展有重要意义。     

Utility of Assimilating Surface Radiometric Temperature Observations for Evaporative Fraction and Heat Transfer Coefficient Retrieval

Recent advances in land data assimilation have yielded variational smoother techniques designed to solve the surface energy balance based on remote observations of surface radiometric temperature. These approaches have a number of potential advantages over existing diagnostic models, including the ability to make energy flux predictions between observation times and reduced requirements for ancillary parameter estimation. Here, the performance of a recently developed variational smoother approach is examined in detail over a range of vegetative and hydrological conditions in the southern U.S.A. during the middle part of the growing season. Smoother results are compared with flux tower observations and energy balance predictions obtained from the two-source energy balance model (TSM). The variational approach demonstrates promise for flux retrievals at dry and lightly vegetated sites. However, results suggest that the simultaneous retrieval of both evaporative fraction and turbulent transfer coefficients by the variational approach will be difficult for wet and/or heavily vegetated land surfaces. Additional land surface information (e.g. leaf area index (L_AI) or the rough specification of evaporative fraction bounds) will be required to ensure robust predictions under such conditions. The single-source nature of the variational approach also hampers the physical interpretation of turbulent transfer coefficient retrievals. Intercomparisons between energy flux predictions from the variational approach and the purely diagnostic TSM demonstrate that the relative accuracy of each approach is contingent on surface conditions and the accuracy with which L_AI values required by the TSM can be estimated.     

The urban boundary-layer field campaign in marseille (ubl/clu-escompte): set-up and first results

The UBL/CLU (urban boundary layer/couche limite urbaine) observation and modelling campaign is a side-project of the regional photochemistry campaign ESCOMPTE. UBL/CLU focuses on the dynamics and thermodynamics of the urban boundary layer of Marseille, on the Mediterranean coast of France. The objective of UBL/CLU is to document the four-dimensional structure of the urban boundary layer and its relation to the heat and moisture exchanges between the urban canopy and the atmosphere during periods of low wind conditions, from June 4 to July 16, 2001. The project took advantage of the comprehensive observational set-up of the ESCOMPTE campaign over the Berre–Marseille area, especially the ground-based remote sensing, airborne measurements, and the intensive documentation of the regional meteorology. Additional instrumentation was installed as part of UBL/CLU. Analysis objectives focus on (i) validation of several energy balance computational schemes such as LUMPS, TEB and SM2-U, (ii) ground truth and urban canopy signatures suitable for the estimation of urban albedos and aerodynamic surface temperatures from satellite data, (iii) high resolution mapping of urban land cover, land-use and aerodynamic parameters used in UBL models, and (iv) testing the ability of high resolution atmospheric models to simulate the structure of the UBL during land and sea breezes, and the related transport and diffusion of pollutants over different districts of the city. This paper presents initial results from such analyses and details of the overall experimental set-up.