Stochastic delineation of wellhead protection area in fractured aquifers and parametric sensitivity study

 In many countries, the setup of protection areas around every drinking water well was instituted at a national level in order to preserve the quality of water as well as the perennially of the resource. Wellhead protection surfaces have been defined using capture zones showing the area influenced by a well within a certain time. A stochastic method is developed for delineating time-related capture zones in fractured aquifers characterised by a low porosity and a high degree of fracturing. The flow velocity within the fractures is determined statistically depending on the distribution of the fracture features and the mass transfer solution is obtained through a particle tracking algorithm. Probabilistic capture zone curves are obtained as a function of the travel time of particles to the well and the percentage of particles apt to be extracted up to this time. A sensitivity study of fracture network parameters leads to the conclusion that orientations and aperture distribution of the fracture sets are of primary importance to the wellhead protection delineation.     

Influence of different GPS receiver antenna calibration models on geodetic positioning

To better understand how receiver antenna calibration models contribute to GPS positioning error budget, we compare station positions estimated with different calibration models: igs05.atx, igs08.atx and individual antenna calibrations. First, the impact of switching from the igs05.atx antenna calibration model to the igs08.atx antenna calibration model is investigated using the EUREF Permanent Network historical data set from 1996 until April 2011. It is confirmed that these position offsets can be effectively represented by the igs05.atx to igs08.atx latitude-dependent model. Then, we demonstrate that the position offsets resulting from the use of individual calibrations instead of type mean igs08.atx calibrations can reach up to 1 cm in the up component, while in the horizontal, the offsets generally stay below 4 mm. Finally, using six antennas individually calibrated by a robot as well as in an anechoic chamber, we observe a position agreement of 2 mm in the horizontal component and a bias of 5 mm in the up component. Larger position offsets, dependent on the antenna/radome type, are, however, found when these individual calibrations are compared to type mean calibrations of two tested antennas.     

Properties and Comparison of Some Kriging Sub-model Aggregation Methods

Mathematical Geosciences - Kriging is a widely employed technique across computer experiments, machine learning and geostatistics. An important challenge for kriging is its high costs when dealing...     

The DynaMICCS perspective

The DynaMICCS mission is designed to probe and understand the dynamics of crucial regions of the Sun that determine solar variability, including the previously unexplored inner core, the radiative/convective zone interface layers, the photosphere/chromosphere layers and the low corona. The mission delivers data and knowledge that no other known mission provides for understanding space weather and space climate and for advancing stellar physics (internal dynamics) and fundamental physics (neutrino properties, atomic physics, gravitational moments...). The science objectives are achieved using Doppler and magnetic measurements of the solar surface, helioseismic and coronographic measurements, solar irradiance at different wavelengths and in-situ measurements of plasma/energetic particles/magnetic fields. The DynaMICCS payload uses an original concept studied by Thalès Alenia Space in the framework of the CNES call for formation flying missions: an external occultation of the solar light is obtained by putting an occulter spacecraft 150 m (or more) in front of a second spacecraft. The occulter spacecraft, a LEO platform of the mini sat class, e.g. PROTEUS, type carries the helioseismic and irradiance instruments and the formation flying technologies. The latter spacecraft of the same type carries a visible and infrared coronagraph for a unique observation of the solar corona and instrumentation for the study of the solar wind and imagers. This mission must guarantee long (one 11-year solar cycle) and continuous observations (duty cycle > 94%) of signals that can be very weak (the gravity mode detection supposes the measurement of velocity smaller than 1 mm/s). This assumes no interruption in observation and very stable thermal conditions. The preferred orbit therefore is the L1 orbit, which fits these requirements very well and is also an attractive environment for the spacecraft due to its low radiation and low perturbation (solar pressure) environment. This mission is secured by instrumental R and D activities during the present and coming years. Some prototypes of different instruments are already built (GOLFNG, SDM) and the performances will be checked before launch on the ground or in space through planned missions of CNES and PROBA ESA missions (PICARD, LYRA, maybe ASPIICS).     

Calculating the long-term displacement rates of a normal fault from the high-resolution stratigraphic record (early Tethyan rifting, French Alps)

Displacement rates of normal faults deduced from stratigraphic data are often unreliable. Here we calculate the velocity of motion on a normal fault from the variations in accommodation potential on both sides of the fault within a high‐resolution time‐frame established by biostratigraphy and physical stratigraphy. Our example is the Ornon normal fault bounding the Early Jurassic Bourg‐d'Oisans Basin formed during Tethyan rifting. We show that motion on the fault was discontinuous when examined at high resolution and over a long time interval. During a first interval (Hettangian to Sinemurian Arietites bucklandi zone) a low rate of displacement (=202–423 m Myr^?1) coeval with diffused extensional deformation throughout the sedimentary basin is observed. A second interval of localized deformation (Early Sinemurian Caenisites turneri zone) is characterized by higher rates of displacement on the fault (1846 m Myr^?1). Our results concur with recent numerical models identifying the main stages of extensional deformation.     

鲜水河断裂带乾宁段岩石特征与内部结构及其物理-化学性质

断裂带的变形行为和断层滑移机制是目前地震研究关注的热点,断裂带岩石特征、内部结构与物理化学性质是确定断层蠕滑或粘滑行为以及断层滑移机制的基础和关键。本文以鲜水河断裂带乾宁段地表出露的断裂岩为研究对象,通过野外地质调查、室内光学显微镜、扫描电镜、粒度统计、粉末X射线衍射分析（XRD）和薄片X射线荧光光谱分析（XRF）等多种研究方法,对鲜水河断裂带岩石特征、结构构造、物性、矿物成分及化学元素分布开展了详细的分析,并探讨了相关变形行为和滑移机制。分析表明：（1）断裂带核部主要由黑色断层泥、浅黄色及黄色断层角砾岩和灰色碎裂岩、灰色断层角砾岩组成,呈单核对称结构;（2）黑色断层泥厚3~5cm,具有快速滑动结构特征,表现为断层粘滑行为。断层泥可划分出13个滑移带,最窄滑移带厚约40μm,至少代表13期古地震事件;（3）断层泥主要由伊利石、高岭石和石英等矿物组成,其中边部伊蒙混层含量异常高,为最新一次古地震的主滑移带。由于伊利石和伊蒙混层（或蒙脱石）为主要黏土矿物的断层泥渗透率低、孔隙流体压力大,以及发现断层泥楔入脉,表明地震过程中断层滑动存在热增压弱化机制;（4）从断层泥不同滑动带中碎块蚀变程度和矿物分布特征来看,地震主滑动带有向碎裂岩方向迁移的趋势。推测断层在滑动过程中,更趋向于向弱矿物含量高（如伊利石、伊蒙混层）、强矿物含量低（如方解石、高岭石）的围岩一侧迁移。

     

青藏高原西部喀喇昆仑断裂活动构造研究进展综述（英文）

喀喇昆仑断裂系(KF)位于青藏高原西缘,具有右旋走滑性质,从帕米尔高原至尼泊尔西部延绵1 000多km。长期以来,对于喀喇昆仑断裂活动的起始时间、总位移量、在不同时间尺度上的滑移速率以及断层两端的精确位置等问题,都存在较大争议。为了更好的了解喀喇昆仑断裂现今的运动学特征及其与喜马拉雅—青藏高原陆内碰撞造山带的关系,确定喀喇昆仑断裂的滑移速率历史以及它随时间和/或空间的变化规律是极其重要的。目前研究表明,从现今的大地测量学尺度到几个百万年的地质学尺度,喀喇昆仑断裂走滑速率的变化范围为3～10 mm/yr。本论文对断裂各段的分布情况进行了详细描述,阐述了获得晚第四纪以来走滑速率的方法,回顾了喀喇昆仑断裂在大地测量学、晚第四纪以及地质学等不同时间尺度的走滑速率,并重点讨论了晚第四纪以来断裂的走滑速率。然后,确定了喀喇昆仑断裂北端的精确位置、讨论了其运动学意义和地震灾害效应。鉴于喀喇昆仑断裂具有长期的活动历史、规模巨大、运动速率较高,我们认为即使板块内部小尺度的似连续变形非常发育,板块模型依然可以很好的解释由于印度-亚洲板块碰撞造成的喜马拉雅北部的岩石圈变形。喀喇昆仑断裂、阿尔金断裂、昆仑断裂及龙木错—郭扎错断裂等青藏高原周缘的主要走滑断裂对青藏高原向东的挤出起着重要的调节作用。     

Determining the drivers of long‐term aridity variability: a southern African case study

This paper highlights the importance of differentiating between precipitation amount and moisture availability (‘humidity’/‘aridity’) when considering proxy records of climate change. While the terms are sometimes used interchangeably, moisture availability is determined by both (i) precipitation amount and (ii) temperature, through its influence on potential evapotranspiration. As many palaeoenvironmental proxies reflect changes in this water balance rather than purely precipitation amount, it is important to distinguish between the potential relative influences of precipitation and temperature if those records are to be interpreted in terms of climate mechanisms and/or compared with model outputs. As a case study, we explore how precipitation and temperature have determined moisture availability in South Africa's summer rainfall zone over the last 45 000 years. Using quantitative reconstructions of mean annual temperature, summer rainfall amount and an aridity index, our analysis reveals strong spatiotemporal variability in the relative influences of precipitation and temperature on aridity. Temperature is shown to have exerted a considerable and even dominant influence on moisture availability, resulting in elevated humidity during the last glacial period, despite significant reductions in precipitation amount.