EVALUATION OF RILL AND EPHEMERAL GULLY EROSION IN CULTIVATED AREAS OF NAVARRE （SPAIN）

Although there is much evidence of intense soil erosion in cultivated areas of Navarre （Spain）, scarce information currently is available regarding soil loss rates, the spatial and temporal distribution of erosion, and the factors controlling these processes. Rills and ephemeral gullies are frequently responsible for a high percentage of total soil erosion, and these features can be considered a good approximation for the minimum erosion rates. With the main purpose of determining the annual soil loss rates in cultivated areas of Central Navarre, a detailed assessment of rainfall and rill and gully erosion was made in 19 small watersheds cultivated with winter grains or vineyards. The study period spanned from 1995 to 2001. For cereal watersheds, soil losses were caused by only one or two rainfall events each year. High erosion rates were observed （0.20-11.50 kg/m^2 per year）. In vineyards, soil losses were caused by several rainfall events each year, occurring year round. High erosion rates were observed in these vineyards （0.33 y 16.19 kg/m^2 per year）. No erosion was observed in those cultivated watersheds with no-till practices. It can be concluded that rill and ephemeral gully erosion can be very significant in Mediterranean regions, and much more attention should be paid to the problem.     

Regional modelling of groundwater flow and salt and environmental tracer transport in deep aquifers in the Paris Basin

A hydrodynamic model which takes into account the aquitard storage effect was developed for the deep multilayered system including the Dogger aquifer and its surroundings in the Paris Basin. It provides a good explanation for a series of observations in the Dogger concerning, for instance, the hydraulic head, the salinity and the transmissivity. The calibration of the model also makes it possible to estimate some unmeasured parameters such as the aquifer and aquitard storage coefficients. Finally, the results of simulations of the transport of ⁴He and ¹⁴C strengthen the representativeness of the model. The Darcy average horizontal velocity in the Dogger, obtained with the model, is of the order of 0.33m year⁻¹.     

Self-sustained oscillations at Volcán de Colima (México) inferred by Independent Component Analysis

We have analyzed Long-Period (LP) seismic events of Volcán de Colima (Mexico) recorded by four three-component broad-band seismometers during January 2006. Frequency-domain analysis shows spectra mainly peaked in the range 0.3–2 Hz and characterized by a monotonic decreasing envelope, as those produced in a cylindrically-symmetric self-oscillating cavity interacting with a confined jet. Independent Component Analysis, a time-series decomposition method, extracts two or three nonlinear oscillation modes depending on the station, with the fundamental one peaked at 0.4–0.5 Hz. These decomposed waves have a well defined spectral content and are self-sustained oscillations with low dimensionality, as shown by dynamic system reconstruction methods. Moreover, they show radial polarization in near field and transverse polarization in far field in North-West South-East direction. Finally, we hypothesize a branched plumbing system with two principal conduits having alignments orthogonal to one another.     

辽宁省防震减灾“九五”重点项目实施概况及建设成果

“九五”期间，辽宁省地震局按照中国地震局的统一部署，应用先进的数字技术、网络技术和计算机技术，对原有的前兆与地震观测的模拟技术系统进行了改造，新建了辽宁省地震信息网络系统和防震减灾指挥中心，这是辽宁省第一次这样大规模地对防震减灾技术系统进行建设和改造。本文对“九五”重点项目的任务、技术系统构成及建设成果进行了阐述。