Interseismic Strain Localization in the San Jacinto Fault Zone

We investigate interseismic deformation across the San Jacinto fault at Anza, California where previous geodetic observations have indicated an anomalously high shear strain rate. We present an updated set of secular velocities from GPS and InSAR observations that reveal a 2–3 km wide shear zone deforming at a rate that exceeds the background strain rate by more than a factor of two. GPS occupations of an alignment array installed in 1990 across the fault trace at Anza allow us to rule out shallow creep as a possible contributor to the observed strain rate. Using a dislocation model in a heterogeneous elastic half space, we show that a reduction in shear modulus within the fault zone by a factor of 1.2–1.6 as imaged tomographically by Allam and Ben-Zion (Geophys J Int 190:1181–1196, 2012) can explain about 50 % of the observed anomalous strain rate. However, the best-fitting locking depth in this case (10.4 ± 1.3 km) is significantly less than the local depth extent of seismicity (14–18 km). We show that a deep fault zone with a shear modulus reduction of at least a factor of 2.4 would be required to explain fully the geodetic strain rate, assuming the locking depth is 15 km. Two alternative possibilities include fault creep at a substantial fraction of the long-term slip rate within the region of deep microseismicity, or a reduced yield strength within the upper fault zone leading to distributed plastic failure during the interseismic period.     

Assessment of the decadal morphodynamic evolution of a mixed energy inlet using ocean color remote sensing

A consistent time series of synoptic and high-frequency bathymetric observations is fundamental to improving our understanding and predictive capabilities regarding the morphological behavior of large coastal inlets. Based on satellite observations, an original approach is proposed to characterize the long-term morphological evolution of the Arcachon lagoon inlet and to describe sediment bypassing and breaching mechanisms. The almost 26-year-long remotely sensed data archive used in this study is built from 78 suitable SPOT images (1986–2012) collected in the framework of the KALIDEOS-Littoral program. Bathymetric information is derived from satellite data using a physics-based model. A validation exercise performed on a large bathymetric survey data set (N?=?43,949) demonstrates that the inversion model performs excellently in estimating the depth of mildly to moderately turbid shallow waters. The performance of the model suggests that the minimum requirements are fulfilled to apply the SPOT-derived bathymetry to morphodynamic applications. We demonstrate that high-spatial-resolution multispectral sensors are well adapted to analyzing the morphological evolution of small- (i.e., sand dunes), medium- (i.e., sandbanks and channels), and large- (i.e., the entire inlet-lagoon system) scale sedimentary structures present in coastal inlets. For the first time, the long-term evolution of a flood and ebb-tidal delta is characterized by observations at a seasonal timescale. Finally, migration rates of sedimentary entities are quantified, and fundamental mechanisms driving the sediment transport cross the inlet are confirmed.     

Revealing the Nature of the Obscured High Mass X-ray Binary IGR J16318-4848

The X-ray source IGR J16318-4848 was the first source discovered by INTEGRAL on January 29, 2003. The high energy spectrum exhibits such a high column density that the source is undetectable in X-rays below 2 keV. On February 23–25, 2003 we triggered a Target of Opportunity (ToO) Program using the EMMI and SOFI instruments on the New Technology Telescope of the European Southern Observatory (La Silla) to get optical and near-infrared (NIR) observations. We discovered the optical counterpart, and confirmed the already proposed candidate in the NIR. NIR spectroscopy revealed a large amount of emission lines, including forbidden iron lines and P-Cygni profiles, showing a strong similarity with CI Cam, another strongly absorbed source. Together with the spectral energy distribution (SED), these data point to a high luminosity, high temperature source, with an intrinsic absorption greater than the interstellar absorption, but two orders of magnitude below the X-ray absorption. All these observations show that IGR J16318-4848 is a high mass X-ray binary (HMXB) at a distance between 0.9 and 6.2 kpc, the mass donor being an early-type star, probably a sgB[e] star, surrounded by a dense and absorbing circumstellar material. This would make the second HMXB with a sgB[e] star as the mass donor after CI Cam. Other sources, discovered by INTEGRAL near IGR J16318-4848 in the direction of the Norma arm, present the same characteristics, at least in X-rays. Such sources may represent a different evolutionary state of X-ray binaries previously undetected with the lower energy space telescopes; if it is so, a new class of strongly absorbed X-ray binaries is being unveiled by INTEGRAL. Out of the 15 sources present in this region, only one might be associated with an unidentified EGRET source: IGR J16393-4643. Therefore these obscured INTEGRAL sources do not seem to be powerful high energy (E > 100 MeV) emitters. Based on observations collected at the European Southern Observatory, Chile (proposal ESO N^∘ 70.D-0340).     

Enhancement of regional variations in salinity and temperature in a coral reef lagoon, New Caledonia

The variability in salinity and temperature in the southwest lagoon of New Caledonia (2100 km²) under non-storm conditions is analysed using a 4-year dataset (1997–2001). Seasonal and interannual variations in salinity are amplified nearshore. Temperature is larger in bays than in the open lagoon during summer, the reverse is true in winter. El Niño Southern Oscillation (ENSO) related nearshore temperature variations parallel those at regional scale, but with seasonal variations amplified. Haline stratification, if any, is enhanced in coastal areas. To cite this article: S. Ouillon et al., C. R. Geoscience 337 (2005).     

Thermodynamic properties of chlorite and berthierine derived from calorimetric measurements

In the context of the deep waste disposal, we have investigated the respective stabilities of two iron-bearing clay minerals: berthierine ISGS from Illinois [USA; (Al_0.975FeIII_0.182FeII_1.422Mg_0.157Li_0.035Mn_0.002)(Si_1.332Al_0.668)O₅(OH)₄] and chlorite CCa-2 from Flagstaff Hill, California [USA; (Si_2.633Al_1.367)(Al_1.116FeIII_0.215Mg_2.952FeII_1.712Mn_0.012Ca_0.011)O₁₀(OH)₈]. For berthierine, the complete thermodynamic dataset was determined at 1 bar and from 2 to 310 K, using calorimetric methods. The standard enthalpies of formation were obtained by solution-reaction calorimetry at 298.15 K, and the heat capacities were measured by heat-pulse calorimetry. For chlorite, the standard enthalpy of formation is measured by solution-reaction calorimetry at 298.15 K. This is completing the entropy and heat capacity obtained previously by Gailhanou et al. (Geochim Cosmochim Acta 73:4738–4749, 2009) between 2 and 520 K, by using low-temperature adiabatic calorimetry and differential scanning calorimetry. For both minerals, the standard entropies and the Gibbs free energies of formation at 298.15 K were then calculated. An assessment of the measured properties could be carried out with respect to literature data. Eventually, the thermodynamic dataset allowed realizing theoretical calculations concerning the berthierine to chlorite transition. The latter showed that, from a thermodynamic viewpoint, the main factor controlling this transition is probably the composition of the berthierine and chlorite minerals and the nature of the secondary minerals rather than temperature.     

Economics of climate policy and collective decision making

This paper explores the reasons why economic instruments of climate change are reluctantly applied and stresses the need for interdisciplinary research linking economic theory and empirical testing to deliberative political procedures. It is divided in three parts. The first one recalls the main issues in implementing Cost-Benefit Analysis such as information problems, uncertainties, discounting the future and irreversibilities. The second part shows how these issues can be treated in integrated assessment and techno-economic models and presents a case study, which shows that

• The chosen scenario tends to stabilize atmospheric CO₂ concentration at around 550 ppm in the long run.
• Exclusion of possibility to trade CO₂ emission permits under a cap regime would increase the cost of emission abatement for OECD countries.
• Combining different flexibility instruments might lead to significant gains in the overall cost of climate policy.

The third part presents results of a survey conducted among the main economic and environmental associations in Switzerland. The survey reveals conflicting views on economic instruments. It shows how the social acceptability of these instruments can be improved in taking explicitly into account these opposing views of special interest groups. Therefore, policy scenarios should be selected in combining techno-economic models with empirical studies about their political and normative context.     

A combined modelling and geochemical study of the fate of terrigenous inputs from mixed natural and mining sources in a coral reef lagoon (New Caledonia)

Open-cast mining for Ni, Cr and Co was conducted in the south-west part of New Caledonia during the 20th century. Abandoned mining and prospecting sites were severely affected by erosion, resulting in an increase in the load of terrigenous particles transported to the coral reef lagoon. This article assesses the impact of a typical small catchment area (La Coulée River, 85 km2 watershed) on two bays (Boulari and Sainte Marie) located near Noumea, New Caledonia's main city. This multi-disciplinary study combines geochemical, sedimentological, and hydrodynamic approaches. Ni and Cr concentrations contained in the geochemical matrix phase of the pelitic fraction were determined. The study of the geochemical signatures together with sedimentological data and 3D numerical simulations of the transport of non-settling particles throughout the lagoon demonstrated that terrigenous inputs from the Coulée River were mainly transported and deposited along the shoreline, reaching areas as distant as Sainte Marie Bay. Although quantitatively low (about 3% of the pelite mass of the bay sediments), the terrigenous inputs in Sainte Marie Bay originating from the Coulée River could be traced. The metal content in suspended matter was over 7000 mg kg(-1) for Ni and 4200 mg kg(-1) for Cr.     

Considering groundwater use to improve the assessment of groundwater pumping for irrigation in North Africa

Groundwater resources in semi-arid areas and especially in the Mediterranean face a growing demand for irrigated agriculture and, to a lesser extent, for domestic uses. Consequently, groundwater reserves are affected and water-table drops are widely observed. This leads to strong constraints on groundwater access for farmers, while managers worry about the future evolution of the water resources. A common problem for building proper groundwater management plans is the difficulty in assessing individual groundwater withdrawals at regional scale. Predicting future trends of these groundwater withdrawals is even more challenging. The basic question is how to assess the water budget variables and their evolution when they are deeply linked to human activities, themselves driven by countless factors (access to natural resources, public policies, market, etc.). This study provides some possible answers by focusing on the assessment of groundwater withdrawals for irrigated agriculture at three sites in North Africa (Morocco, Tunisia and Algeria). Efforts were made to understand the different features that influence irrigation practices, and an adaptive user-oriented methodology was used to monitor groundwater withdrawals. For each site, different key factors affecting the regional groundwater abstraction and its past evolution were identified by involving farmers’ knowledge. Factors such as farmer access to land and groundwater or development of public infrastructures (electrical distribution network) are crucial to decode the results of well inventories and assess the regional groundwater abstraction and its future trend. This leads one to look with caution at the number of wells cited in the literature, which could be oversimplified.     

Turbulent Structures in a Pine Forest with a Deep and Sparse Trunk Space: Stand and Edge Regions

Forested landscapes often exhibit large spatial variability in vertical and horizontal foliage distributions. This variability may affect canopy-atmosphere exchanges through its action on the development of turbulent structures. Here we investigate in neutral stratification the turbulent structures encountered in a maritime pine forest characterized by a high, dense foliated layer associated with a deep and sparse trunk space. Both stand and edge regions are considered. In situ measurements and the results of large-eddy simulations are used and analyzed together. In stand conditions, far from the edge, canopy-top structures appear strongly damped by the dense crown layer. Turbulent wind fluctuations within the trunk space, where the momentum flux vanishes, are closely related to these canopy-top structures through pressure diffusion. Consequently, autocorrelation and spectral analyses are not quite appropriate to characterize the vertical scale of coherent structures in this type of canopy, as pressure diffusion enhances the actual scale of structures. At frequencies higher than those associated with canopy-top structures, wind fluctuations related to wake structures developing behind tree stems are observed within the trunk space. They manifest themselves in wind velocity spectra as secondary peaks in the inertial subrange region, confirming the hypothesis of spectral short-cuts in vegetation canopies. In the edge region specific turbulent structures develop just below the crown layer, in addition to canopy-top structures. They are generated by the wind shear induced by the sub-canopy wind jet that forms at the edge. These structures provide a momentum exchange mechanism similar to that observed at the canopy top but in the opposite direction and with a lower magnitude. They may develop as in plane mixing-layer flows, with some perturbations induced by canopy-top structures. Wake structures are also observed within the trunk space in the edge region.