丽江7.0级和唐山7.8级地震前形变场动态演化与异常特征     

王双绪  江在森 《大地测量与地球动力学》1997,(4)

对１９９６年丽江７．０级和１９７６年唐山７．８级地震前的形变场动态演化过程做了对比分析，结果表明：①两次强震前形变场均存在大范围垂直差异运动增强以及与构造相关的形变高梯度带（区）；②震前数年（或更长）垂直形变场的趋势改变，并出现形变局部化。结合强震前区域地震活动，研究了这两次地震前垂直形变场动态演化与孕震形变的异常特征，认为与构造相关的强烈差异运动是孕震应变能积累的主要方式。  相似文献   

关于港口经济和港城一体化的理论分析   总被引：4，自引：0，他引：4  

徐质斌  朱毓政 《广东海洋大学学报》2004,24(5):7-13

运用经济资源配置中的成本—收益分析、区域经济生长的极核理论等 ,对港口的经济性、港城经济一体化发生的内在机理和模型、建设重点等进行理论分析  相似文献   

南极地区地磁扰日变化S_D场特征          下载免费PDF全文

刘长发  张平  杨友华  刘春节  汪阳 《极地研究》1996,8(3):57-63

利用南极地磁资料研究了地磁扰日变化ＳＤ场特征。１）ＳＤ场变化不如Ｓｑ场变化规则,无明显的昼夜差异;太阳活动高年（１９９１年）比下降年（１９９４年）ＳＤ场变化更强烈。２）极隙区中山站ＳＤ场变幅比亚极光区长城站和北半球低纬区北京台的ＳＤ场变幅大１０倍以上。３）中山站Ｓ０Ｄ（Ｈ）变化呈“正弦波”形态,与长城站和北京台Ｓ０Ｄ（Ｈ）变化形态相反。４）中山站Ｓ０Ｄ等效电流矢量在早晨－下午（０２～１５ｈ）矢量方向为反时针西向,下午－夜间（１５～０２ｈ）矢量方向为顺时针东向,这是由极区东向、西向电射流和极区电流涡旋所引起;长城站与北京台Ｓ０Ｄ等效电流矢量很小,这是由极区东向和西向电射流的影响所致。  相似文献   

A real time processing system of seismic waves using personal computers — Function and characteristics     

Jun Fan  Tian-Chang Chen  Wei-Bin Han  Jian Zeng  Si-Hua Zheng  Akira Hasegawa  Shigeki Horiuchi 《地震学报(英文版)》1998,11(3):375-379

Conclusions The real-time processing system of CTSN performs following: A/D conversion; automatic event detection; event data saving; automatic measure of P and S arrivals; event location and print out the calculated results. It is corrected at ny moment by using the off-line system. Since December 1993, this system has been operating normally in the CTSN. More than 4 000 earthquakes have been recorded in the system. It has high accuracy in automatic picking P and S arrivals. The location of the earthquakes determined by on-line system are close to those given in published catalogues which are determined by manual procedure. This system can finish locate event in three minutes. It also gives satisfactory epicenter locations for distant events by inputting manually S arrivals in the off-line system. The operation of this system had brought the technical superiority of the CTSN. It not only reduces the labor intensity and simplifies the working procedure, but also makes our research facility into the superior ranks in this field of our country. In conclusion, the real-time processing system of seismic wave provides technical support for the daily requirements of monitoring seismic activity as well as a lot of digital waveform data used seismic research in Sichuan area. This subject is sponsored by the Scientific and Technical Committee of Sichuan Province.  相似文献   

The microeconomics of mineral extraction under capacity constraints     

Robert D. Cairns 《Natural Resources Research》1998,7(3):233-244

The mineral investment decision under certainty is discussed in the context of broad microeconomic features of the industry, the central one being that production is constrained by capacity. The assumptions of the economic literature on natural resources are evaluated in the context of these features and the assumptions that permit the modeling of such facts are examined. Several characteristics of extraction and equilibrium, and some implications of uncertainty, are considered.  相似文献   

The effect of the temporal resolution of the wind forcing on a central Mediterranean Sea model     

《Dynamics of Atmospheres and Oceans》2021

The impact of the wind forcing temporal resolution in the central Mediterranean Sea is addressed using a numerical ocean circulation model. The model uses interactive surface fluxes based on the ERA-Interim 6-hourly atmospheric reanalyses except for the 10 m wind for which ERA5 hourly reanalyses are used. Additional temporal resolution (2, 3, 6, 12 and 24 h) wind sets are deduced from the ERA5 hourly data. An ensemble of simulations (six members) is then performed where only the temporal resolution of the wind forcing is changed. The impact of the temporal resolution is studied based on this set of simulations. The dependence of the surface wind stress and heat flux on the wind resolution is derived based on an analytical expression where the Weibull distribution is used to characterise the probability density function of the wind speed. Results from the analytical model are found close to those from the numerical model when a linear increase of the exchange coefficients with the wind speed is considered. Power input into the sea and surface heat loss both increase with the increase of the temporal resolution but at lower rates when approaching hourly forcing values. The increase of the latent heat loss at these high resolutions is small (~−0.8 Wm^-2) but still important, around 10–20% the Mediterranean basin heat budget (−5 to −7 Wm^-2). The increase of the wind forcing temporal resolution decreases the sea surface temperature (SST) and increases the sea surface salinity (SSS) with largest values in the shallow area of the Gulf of Gabès (eastern coast of Tunisia). A decrease of SSS is however noticed in some areas mainly northwest of the Tunisia coast. Hydrographical changes are also found in the Tunisia-Sicily channel. They are characterised by mesoscale structures with no remarkable change of the major water veins.  相似文献   

Improving runoff prediction using agronomical information in a cropped,loess covered catchment          下载免费PDF全文

Marie Lefrancq  Paul Van Dijk  Victor Jetten  Matthieu Schwob  Sylvain Payraudeau 《水文研究》2017,31(6):1408-1423

Predicting runoff hot spots and hot‐moments within a headwater crop‐catchment is of the utmost importance to reduce adverse effects on aquatic ecosystems by adapting land use management to control runoff. Reliable predictions of runoff patterns during a crop growing season remain challenging. This is mainly due to the large spatial and temporal variations of topsoil hydraulic properties controlled by complex interactions between weather, growing vegetation, and cropping operations. This interaction can significantly modify runoff patterns and few process‐based models can integrate this evolution of topsoil properties during a crop growing season at the catchment scale. Therefore, the purpose of this study was to better constrain the event‐based hydrological model Limburg Soil Erosion Model by incorporating temporal constraints for input topsoil properties during a crop growing season (LISEM). The results of the temporal constraint strategy (TCS) were compared with a classical event per event calibration strategy (EES) using multi‐scale runoff information (from plot to catchment). The EES and TCS approaches were applied in a loess catchment of 47 ha located 30 km northeast of Strasbourg (Alsace, France). A slight decrease of the Nash–Sutcliffe efficiency criterion on runoff discharge for TCS compared to EES was counterbalanced by a clear improvement of the spatial runoff patterns within the catchment. This study showed that limited agronomical and climatic information added during the calibration step improved the spatial runoff predictions of an event‐based model. Reliable prediction of runoff source, connectivity, and dynamics can then be derived and discussed with stakeholders to identify runoff hot spots and hot‐moments for subsequent land use and crop management modifications.  相似文献   

Probability of combined high sea levels and large rains in Malmö, Sweden,southern Öresund          下载免费PDF全文

Lars Bengtsson 《水文研究》2016,30(18):3172-3183

Observations of sea level and precipitation in Malmö, Sweden in the southeastern part of the sound Öresund have been used to estimate the probabilities of local compound events of high sea level and large daily and hourly rains. There are observations of sea level and daily rains extending back to 1930. The observations of short‐term rainfall are from 1980 and onwards. Most large rainfalls come in the summer, while the highest sea levels are in the autumn and in the winter. The highest observed sea level is about 130 cm above mean sea level, and the largest daily rain is close to 100 mm. However, the highest sea level observed during a day with rainfall corresponding to the 1‐year rain is less than 60 cm. The highest sea level observed during an hour with 1‐year hourly rainfall is 30 cm. From the statistics of daily rains, hourly rains and sea level, extreme values for each of them have been computed. For events with frequency higher than one per four years the probabilities of combined events sea level – rainfall are determined directly from the observations. For more rare events, marginal distributions of sea level and rainfall are determined. Copulas and conditional probabilities are used. When the sea level exceeds 20 cm above mean sea level, daily rains exceeding 10 mm are almost independent of the sea level and so are hourly rains exceeding 5 mm. It is extremely rare that large rains occur when the sea level is very high. The combination of 1‐year rainfall and the 1‐year sea level has a return period of more than 200 years.  相似文献   

Modelling of steady‐state fluid flow in 3D fractured isotropic porous media: application to effective permeability calculation     

Minh‐Ngoc Vu  Ahmad Pouya  Darius M. Seyedi 《国际地质力学数值与分析法杂志》2013,37(14):2257-2277

In this paper, 3D steady‐state fluid flow in a porous medium with a large number of intersecting fractures is derived numerically by using collocation method. Fluid flow in the matrix and fractures is described by Darcy's law and Poiseuille's law, respectively. The recent theoretical development presented a general potential solution to model the steady‐state flow in fractured porous media under a far‐field condition. This solution is a hypersingular integral equation with pressure field in the fracture surfaces as the main unknown. The numerical procedure can resolve the problem for any form of fractures and also takes into account the interactions and the intersection between fractures. Once the pressure field and then the flux field in fractures have been determined, the pressure field in the porous matrix is computed completely. The basic problem of a single fracture is investigated, and a semi‐analytical solution is presented. Using the solution obtained for a single fracture, Mori‐Tanaka and self‐consistent schemes are employed for upscaling the effective permeability of 3D fractured porous media. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Thermal and magnetically driven instabilities in a non-constantly stratified fluid layer     

J. Boda 《地球物理与天体物理流体动力学》2013,107(1-4):77-90

Abstract

The linear hydromagnetic stability of a non-constantly stratified horizontal fluid layer permeated by an azimuthal non-homogeneous magnetic field is investigated for various widths of the stably stratified part of the layer in the geophysical limit q→0 (q is the ratio of thermal and magnetic diffusivities). The choice of the strength of the magnetic field B_o is as in Soward (1979) (see also Soward and Skinner, 1988) and the equations for the disturbances are treated as in Fearn and Proctor (1983). It was found that convection is developed in the whole layer regardless of the width of its stably stratified part. The thermal instability penetrates essentially from the unstably stratified part of the layer into the stably stratified part for A ～ 1 (A characterises the ratio of the Lorentz and Coriolis forces). When the magnetic field is strong (A>1) the thermal convection is suppressed in the stably stratified part of the layer. However, in this case, it is replaced by the magnetically driven instability; which is fully developed in the whole layer. The thermal instabilities always propagate westward and exist for all the modes m. The magnetically driven instabilities propagate either westward or eastward according to the width of the stably and unstably stratified parts and exist only for the mode m=1.  相似文献