Using the Fisher–Shannon method to characterize continuous seismic signal during volcanic eruptions: application to 2011–2012 El Hierro (Canary Islands) eruption

We investigated the dynamics of the continuous seismic signal recorded before and during the 2011–2012 El Hierro eruption (Canary Islands) using the innovative approach of the Fisher–Shannon method, a suitable statistical tool for detecting dynamic changes in complex systems. Our findings identify dynamic changes in the seismic signal that can be correlated with different stress states of the magmatic setting and the plumbing system in the volcano at El Hierro. The results contribute to the understanding of the fracturing pattern in the crust during a new intrusion and eruption of an overpressurized batch of magma.     

Improving the representation of soil moisture by using a semi‐analytical infiltration model

Soil moisture is widely recognized as a fundamental variable governing the mass and energy fluxes between the land surface and the atmosphere. In this study, the soil moisture modelling at sub‐daily timescale is addressed by using an accurate representation of the infiltration component. For that, the semi‐analytical infiltration model proposed by Corradini et al. (1997) has been incorporated into a soil water balance model to simulate the evolution in time of surface and profile soil moisture. The performances of this new soil moisture model [soil water balance module‐semi‐analytical (SWBM‐SA)] are compared with those of a precedent version [SWBM‐Green–Ampt (GA)] where the GA approach was employed. Their capability to reproduce in situ soil moisture observations at three sites in Italy, Spain and France is analysed. Hourly observations of quality‐checked rainfall, temperature and soil moisture data for a 2‐year period are used for testing the modelling approaches. Specifically, different configurations for the calibration and validation of the models are adopted by varying a single parameter, that is, the saturated hydraulic conductivity. Results indicate that both SWBMs are able to reproduce satisfactorily the hourly soil moisture temporal pattern for the three sites with root mean square errors lower than 0.024 m³/m³ both in the calibration and validation periods. For all sites, the SWBM‐SA model outperforms the SWBM‐GA with an average reduction of the root mean square error of ~20%. Specifically, the higher improvement is observed for the French site for which in situ observations are measured at 30 cm depth, and this is attributed to the capability of the SA infiltration model to simulate the time evolution of the whole soil moisture profile. The reasonable models performance coupled with the need to calibrate only a single parameter makes them useful tools for soil moisture simulation in different regions worldwide, also in scarcely gauged areas. Copyright © 2013 John Wiley & Sons, Ltd.     

Isotopic fingerprints of Milankovitch cycles in Pennsylvanian carbonate platform‐top deposits: the Valdorria record,Northern Spain

Sedimentary cyclic sequences deposited during the Late Palaeozoic Ice Age are widespread. Glacio‐eustatic control of the cyclic patterns is commonly accepted, and the durations of the cyclothems generally match the short‐ and long‐eccentricity Milankovitch orbital parameters. Nevertheless, geochemical fingerprints of orbital parameters are poorly documented in deep‐time sedimentary records. Here, we report on well‐exposed Bashkirian cyclothems of c. 123 ka and c. 400 ka durations from the Valdorria platform. The shorter‐term cyclothems can be grouped into longer‐term composite sequences that are consistent with generally accepted durations of c. 125 ka and c. 400 ka for Milankovitch eccentricity cycles. The stratigraphic pattern is mirrored by the isotope geochemical signals, which show distinct recurring trends. These trends are confirmed by statistical tests. Whereas intrinsic factors and/or subaerial exposure related to sea‐level lowstands might have truncated cycle patterns in tectonically stable basins, rapid subsidence of the Valdorria platform's foreland basin appears to have contributed to a faithful recording of cyclothems of different orders. The patterns and biostratigraphic constraint revealed in this study demonstrate the power of orbital forcing in imprinting sedimentary and geochemical signals in the rock record.     

Three thousand years of flank and central vent eruptions of the San Salvador volcanic complex (El Salvador) and their effects on El Cambio archeological site: a review based on tephrostratigraphy

The volcanic events of the last 3,000?years at San Salvador volcanic complex are reviewed using detailed stratigraphic records exposed in new excavations between 2005 and 2007, at El Cambio archeological site (Zapotitán Valley, El Salvador), and in other outcrops on the northern and northwestern sectors of the complex. The sequences that overlie Tierra Blanca Joven (cal. 429?±?107?ad), from the Ilopango caldera, comprise the Loma Caldera (cal. 590?±?90?ad) and El Playón (1658?C1671) deposits and the San Andrés Tuff (cal. 1031?±?29?ad), related to El Boquerón Volcano. The surge deposits within the El Playón, San Andrés Tuff and overlying Talpetate II sequences indicate the significance of phreatomagmatic phases in both central vent and flank eruptions during the last 1,600?years. Newly identified volcanic deposits underlying Tierra Blanca Joven at El Cambio extend the stratigraphic record of the area to 3,000?years?bp. Paleosols interstratified with those deposits contain cultural artifacts which could be associated with the Middle Preclassic period (900?C400?bc). If correct, human occupation of the site during the Preclassic period was more intense than previously known and volcanic eruptions must have affected prehistoric settlements. The archeological findings provide information on how prehistoric populations dealt with volcanic hazards, thousands of years ago in the eastern Zapotitán Valley, where several housing projects are currently being developed. The new stratigraphic and volcanological data can be used as a basis for local and regional hazard assessment related to future secondary vent activity in the San Salvador Volcanic Complex.     

The potential added value of Regional Climate Models in South America using a multiresolution approach

This paper aims to identify those regions within the South American continent where the Regional Climate Models (RCMs) have the potential to add value (PAV) compared to their coarser-resolution global forcing. For this, we used a spatial-scale filtering method based on the wavelet theory to distinguish the regional climatic signal present in atmospheric surface fields from observed data (CPC and TRMM) and 6 RCM simulations belonging to the CORDEX Project. The wavelet used for filtering was Haar wavelet, but a comparative analysis with Daubechies 4 wavelet indicated that meteorological fields or regional indices were not very sensitive to the wavelet selected. Once the longer wavelengths were filtered, we focused on analyzing the spatial variability of extreme rainfall and the spatiotemporal variability of maximum and minimum surface air temperature on a daily basis. The results obtained suggest essential differences in the spatial distribution of the small-scale signal of extreme precipitation between TRMM and regional models, together with a large dispersion between models. While TRMM and CPC register a large signal throughout the continent, the RCMs place it over the Andes Cordillera and some over tropical South America. PAV signal for surface air temperature was found over the Andes Cordillera and the Brazilian Highlands, which are regions characterized by complex topography, and also on the coasts of the continent. The signal came specially from the small-scale stationary component. The transient part is much smaller than the stationary one, except over la Plata Basin where they are of the same order of magnitude. Also, the RCMs and CPC showed a large spread between them in representing this transient variability. The results confirm that RCMs have the potential to add value in the representation of extreme precipitation and the mean surface temperature in South America. However, this condition is not applicable throughout the whole continent but is particularly relevant in those terrestrial regions where the surface forcing is strong, such as the Andes Cordillera or the coasts of the continent.     

Absorption effects in sixHii regions

We have measured the profile of the 21-cm line of neutral hydrogen in the direction of sixHii regions (RCW 38, RCW 49, RCW 57 (b), RCW 74, W22, and W37). By comparison with line profiles outside the nebulae we have deduced the absorption profiles corresponding to eachHii region. We compare our results with those of other authors in the 21-cm line, in the line of OH, and in the recombination lines of hydrogen.     

The climate in Zafra from 1750 to 1840: history and description of weather observations

Weather observations in Zafra during the period 1750 to 1840 have been compiled and studied. Zafra was the capital of the Duchy of Feria, located in the southwest of the Iberian Peninsula. The documentary sources used in this work are weekly reports submitted to the Duke (who lived in Madrid) that contain a section describing the weather of the preceding week or less. Regular and updated meteorological information was vital to the government of this Duchy as farming and ranching constituted the bases of the economic activity in this region, allowing the estimation of crop yield and quality and a better management of the trade of agricultural products. Therefore, this documentary source is exceptional to study the climate of SW Iberia due to its continuity, homogeneity and high temporal-resolution.     

Importance of porosity and transfer of matter in the rock weathering processes: two examples in central Spain

Some physical properties (bulk and free porosity, pore size distribution), and the chemical composition and mass balance of two deeply weathered profiles one developed on Hercynian granodiorite and the other on pre-Cambrian slates were studied. Hydric and mercury porosimetry, nitrogen adsorption techniques, chemical analyses and XRD techniques were used. On granodiorite, weathering has created increased porosity with a pore diameter <5 μm, whereas on slates the weathering has produced of ca. 1 μm in diameter. These pore sizes have played an important role in the weathering processes. Assuming that weathering preserves volumes, except in the uppermost part of the profiles, it brought about a loss of matter of more than 12% (~300 kg/m³) on granodiorite and ca. 30% (~800 kg/m³) on slates. These changes are related to shifts in the mineralogical evolution, with the appearance of new 2:1 and 1:1 phyllosilicates and Fe oxy-hydroxides as the main authigenic minerals. The release of matter, at least since the upper Neogene until the present, has led to the lowering of relief in a more or less homogeneous way, giving rise to gentle hillsides and flat surfaces below which the current river networks are incised. Porosity studies have the potential to explain several specific landforms as well as affecting landscape development in general.     

Long-term response analysis of FPSO mooring systems

The design of mooring systems for floating production units usually considers extreme environmental conditions as a primary design parameter. However, in the case of FPSO (Floating, Production, Storage and Offloading) units, the worst response for the mooring system may be associated with other sea state conditions due to the fact that its extreme response may be associated with a resonant period instead of an extreme wave height. The best way to deal with this problem is by performing long-term analysis in order to obtain extreme response estimates. This procedure is computationally very demanding, since many short-term environmental conditions, and their associated stochastic nonlinear time domain numerical simulations of the mooring lines, are required to obtain such estimates. A simplified approach for the long-term analysis is the environmental contour-line design approach. In this paper a Monte Carlo-based integration procedure combined with an interpolation scheme to obtain the parameters of the short-term response distribution is employed to hasten the long-term analysis. Numerical simulations are carried out for an FPSO at three different locations considering a North Sea joint probability distribution for the environmental parameters. The long-term analysis results are compared against those obtained using extreme environmental conditions and environmental contour-line methodology. These results represent the characteristic load effect for the design of mooring systems of floating units using the reliability analysis for mooring line. The results show that the long-term results are usually more critical than those obtained with the other approaches and even different mooring lines can be identified as the critical ones.