Seismic and flood structural risk in Motozintla,Chiapas, Mexico

Natural Hazards - Using the methodology developed by the Mexican National Disaster Prevention Centre (CENAPRED), we assessed the housing’s structural risk to earthquakes and floods of the...     

Pb-derived ages for the reconstruction of terrestrial contaminant history into the Mexican Pacific coast: Potential and limitations

²¹⁰Pb is widely used for dating recent sediments in the aquatic environment; however, our experiences working in shallow coastal environments in the Pacific coast of Mexico have demonstrated that the potential of ²¹⁰Pb for reliable historical reconstructions might be limited by the low ²¹⁰Pb atmospheric fallout, sediment mixing, abundance of coarse sediments and the lack of ¹³⁷Cs signal for ²¹⁰Pb corroboration. This work discusses the difficulties in obtaining adequate sedimentary records for geochronological reconstruction in such active and complex settings, including examples of ²¹⁰Pb geochronologies based on sediment profiles collected in two contrasting areas coastal areas (mudflats associated to coastal lagoons of Sinaloa State and the continental shelf of the Gulf of Tehuantepec), in which geochemical data was used to support the temporal frame established and the changes in sediment supply recorded in the sediment cores which were related to the development of land-based activities during the last century.     

Flare forecasting based on sunspot-groups characteristics

Our comprehension of solar flares is still lacking in many aspects and the possibility of observing active regions during the first phases of flare occurrence is limited by our capability of doing accurate flare forecasting. In order to give a contribution to this aspect, we focused our attention on the characteristics that must be fulfilled by sunspot-groups in order to be flare-productive. We addressed this problem using a statistical approach: first, we analyzed sunspot-groups parameters (i.e., Zürich class, magnetic configuration, area, morphology of the penumbra) and evolution; then, we performed a flare forecasting campaign, based on the results obtained in the first phase and on real-time observations. The results obtained by comparing the flare forecasting probability with the number of flares that have actually occurred are quite encouraging; we plan to improve this procedure by including a bigger statistical sampling.     

Comparison of marine and river water humic substances in a Patagonian environment (Argentina)

Structural aspects of humic substances (HSs) in marine waters of Engaño Bay (Atlantic Ocean) and water from the Chubut River (Patagonia, Argentina) were compared. The HSs were isolated, purified, and analyzed using a multiple-method approach for structural characterization: elemental analysis, nuclear magnetic resonance (¹³C and ¹H NMR), infrared spectroscopy (FTIR), UV-visible absorption and fluorescence. Similarities between the marine and freshwater components were evaluated on the basis of N and O contents, H/C and C/N atomic ratios, infrared bands from nitrogen-containing and carboxylic groups, percentage of functional groups obtained from NMR spectra, spectral slope coefficient of absorption spectra, absorbance ratios at 250 and 365 nm (E ₂/E ₃), aromaticity, excitation–emission matrices and fluorescence quantum yield. Both the Engaño Bay and Chubut River waters have HSs that are mainly composed of fulvic acids (FAs); although they are very similar, they may be distinguished from one another. Similarities include the predominance of aliphatic carbon content (low aromatic content); however, the water bodies differed in their content of proteins and carboxylic acids. The Engaño Bay FAs have mainly an aquatic origin; although the Chubut River FAs suggest a similar aquagenic origin, there is also evidence of contributions from pedogenic FAs.     

Inventory and geometrical changes in small glaciers covering three Northern Patagonian summits using remote sensing and GIS techniques

In the last few decades, a large quantity of research has been performed to elucidate the current behavior of glaciers in southern Chile, especially with respect to the volumetric changes in the outlets of the Northern and Southern Patagonian Icefields (NPI and SPI, respectively). Calculations have shown a generalized thinning and withdrawal, which greatly contributes to the increase in sea level attributed to the ice melt from non-polar glaciers. However, these icefields are surrounded by many small icecaps, which have yet to be studied in detail. A precise estimation of the volume of ice located in these mountain chains could provide new information with respect to this area's exact contribution to the increase in sea level. Thus, this study presents an inventory of relatively small Northern Patagonian glaciers in the surrounding of the three summits: Mount Queulat, and the Macá and Hudson volcanoes. The study used remote sensing techniques in a GIS environment to determine the margins, surface areas, thickness changes and hypsometry for the glaciated zones. Landsat images from different dates were analyzed using standard band ratio and screen delineation techniques. Additionally, digital elevation models from different dates were compared using map algebra, calculating thickness changes. Based on the results, we propose that there are important volumetric changes in the glaciers studied, which could be explained by precipitation trends in a general context, and an influence of the glaciers' sizes in some local response. Therefore, we suggest the exact contribution of the Patagonia to the increase in sea level corresponds to a regional pattern rather than just the behavior of a single ice field.     

Functional diversity of fish and invertebrates in coral and rocky reefs of the Eastern Tropical Pacific

To define the functional groups of fish and macroinvertebrates in the Eastern Tropical Pacific (ETP), visual censuses were performed in 18 areas of four biogeographic provinces: Cortés, Mexican, Panamic and Oceanic Islands. A total of 257 fish and macroinvertebrate species were recorded, and from them, 27 morpho‐functional groups (MFGs) were constructed on the basis of trophic level, maximum size, taxonomy and morphology. Biomass, richness, diversity and evenness of MFGs were calculated for each province and compared statistically; a regression analysis between taxonomic and functional diversity was conducted to observe the relationship between these two indicators. There were significant differences in all ecological indices (p < .002), highlighting the high biomass and richness of MFGs in the Cortés and Oceanic Islands provinces (>400 g/m²), associated with the influence of cold currents in the northernmost region and less fishing pressure in protected areas. A decreasing pattern of MFG richness towards the tropics was observed, which demonstrates that in the ETP, the relationship between habitat heterogeneity and species diversity has been translated into functional complexity. The Mexican province was the most functionally diverse (biomass well distributed in the MFG; H′ = 0.46 ± 0.009). Related to this, it is predicted that biomass is biased towards certain functional groups (i.e., large carnivores), which shows that the H′ index of the MFG is not a good indicator of the conservation status of ETP reefs. Finally, regression analysis suggests that functional diversity increases at low species diversity but eventually reaches an asymptote (almost all possible functions are represented).     

A sapping erosion susceptibility model for the southern Cantabrian Range, North Spain

A susceptibility model of sapping-related depressions has been produced by analysing the statistical relationship between the location of depressions and topographical variables. Sapping erosion plays an important role in the growth of gullies developed over poorly-consolidated quartzite conglomerates in the northern sector of the Duero Tertiary Basin (the Cantabrian Mountain Range of Spain). Gullies, topsoil subsidence depressions related to sapping processes, and shallow slides have been identified over sandy soils in an area of 37 km². This area underwent major changes in land use during the 20th century, leading to the expansion of gully erosion processes. On the surface, depressions of several meters in diameter, caused by internal erosion related to sapping processes, can be identified. Using the topographical location of these topsoil depressions and several topographical variables, 14 discriminate functions were derived to provide information about the influence of topography on the development of sapping erosion processes. The functions have accuracy levels varying from 56 to 81%. The most accurate function was regionalized by means of a Geographical Information System and was used to complete a land classification method which is based on the Mahalanobis distance to the multivariate average (centroid) of a sapping erosion form group. The classification of this model allows the identification of areas with different relative probabilities of sapping processes and the resultant growth of gullies.     

A search for wide visual companions of exoplanet host stars: The Calar Alto Survey

We have carried out a search for co‐moving stellar and substellar companions around 18 exoplanet host stars with the infrared camera MAGIC at the 2.2 m Calar Alto telescope, by comparing our images with images from the all sky surveys 2MASS, POSS I and II. Four stars of the sample namely HD80606, 55 Cnc, HD46375 and BD–10°3166, are listed as binaries in the Washington Visual Double Star Catalogue (WDS). The binary nature of HD80606, 55 Cnc, and HD46375 is confirmed with both astrometry as well as photometry, thereby the proper motion of the companion of HD46375 was determined here for the first time.We derived the companion masses as well as the longterm stability regions for additional companions in these three binary systems. We can rule out further stellar companions around all stars in the sample with projected separations between 270AU and 2500AU, being sensitive to substellar companions with masses down to ∼60 M_Jup (S /N = 3). Furthermore we present evidence that the two components of the WDS binary BD–10°3166 are unrelated stars, i.e this system is a visual pair. The spectrophotometric distance of the primary (a K0 dwarf) is ∼67 pc, whereas the presumable secondary BD–10°3166B (a M4 to M5 dwarf) is located at a distance of 13 pc in the foreground. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Cancelling magnetic feature and filament activation

We report in this paper the analysis of the evolution of a magnetic fragment observed in NOAA 9445 on 5 May, 2001. This magnetic fragment emerged laterally to a filament which later split into two parts. The bifurcation site coincided with the magnetic fragment location and the part of the filament which split was later destabilized and a flare occurred. The magnetic flux variations in the magnetic fragment and in the surrounding area were analyzed and, considering their trends and other observational signatures (Hα brightenings and associated plasma motions), we could infer that it was a cancelling magnetic feature (CMF).We determined some geometrical and physical parameters of the CMF (area, magnetic flux variation, cancellation speed and flux cancellation rate) using high resolution magnetograms taken by BBSO. We compared the observed parameters of the CMF with the parameters of low‐lying reconnection current sheets given in the model proposed by Litvinenko (1999) and found good agreement between observed and theoretical values. Therefore, we conclude that a low‐lying magnetic reconnection process might be the cause of the filament activation. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)