Radon in soil anomaly observed at Los Azufres geothermal field,Michoacan: a possible precursor of the 1985 Mexico earthquake (Ms = 8.1)     

N. Segovia  S. de la Cruz-Reyna  M. Mena  E. Ramos  M. Monnin  J. L. Seidel 《Natural Hazards》1989,1(4):319-329

A radon anomaly in a nuclear track detector placed on a fault was detected prior to the destructive (Ms = 8.1) Mexican earthquake of 19 September 1985. The fault is a structural feature of the geothermal field Los Azufres, 260 km NE of the epicentral area. Since no other phenomenon can be found as a possible cause for the radon anomaly, it is proposed that preseismic regional stress perturbations may produce changes in the fluid transport patterns at the fault, suggesting that radon measurements in similar conditions could provide a good precursor in high seismic risk areas.  相似文献   

Three-dimensional joint elements applied to concrete-faced dams     

J. L. Justo  F. Segovia  A. Jaramillo 《国际地质力学数值与分析法杂志》1995,19(9):615-636

In the study of concrete-face dams it is essential to provide joint elements; otherwise the calculated stresses at the facing will be non-allowable. Three-dimensional joint elements must be simple so as not to increase in excess the CPU time. Seven non-incremental joint elements have been formulated or developed, and their relative advantages discussed. It is shown that quasi-linear or linear joint elements at the perimeter of the solid elements can have calculation advantages, specially for interfaces with ‘no tension’ resistance. A system of thin solid finite elements (FE) joints at the face may reproduce qualitatively the displacements and stresses, but not quantitatively. With a system of quasi-linear elements placed at the boundaries of the solid FE we have been able to predict correctly the displacements, strains and joint openings at Cethana concrete-faced rockfill dam.  相似文献   

On the advantage of sharing a holdfast: effects of density and occurrence of kin aggregation in the kelp Lessonia berteroana          下载免费PDF全文

Nicolás I. Segovia  Julio A. Vásquez  Sylvain Faugeron  Pilar A. Haye 《Marine Ecology》2015,36(4):1107-1117

We investigated the density‐dependent and genetic relatedness that regulate the occurrence of inter‐individual (genet) fusion forming plurigenotypic organisms in the brown alga Lessonia berteroana. Recruitment generally occurs at high densities in the inter‐tidal, allowing contact of neighbouring holdfasts as they grow and expand on the substrate. Algal density, by contrast, is regulated by the effects of herbivory and wave impact, which often lead to low holdfast density. Herein, we investigated whether the occurrence of plurigenotypic organisms and their genotypic composition (number of genotypes per plurigenotypic organism) are density dependent and affected by kin selection in the inter‐tidal kelp L. berteroana. Four microsatellite loci were used to analyse DNA from 260 samples obtained from shared and non‐shared holdfasts, at two sites with high and two site with low holdfast density. Analyses showed that fusions forming plurigenotypic organisms are extremely common. Interestingly, the frequency of fusions was higher in low‐density sites, in which 100% of the plants had at least two genotypes and the average was 3.5. In high‐density sites, 62% of plants were plurigenotypic, with an average of 2.8 genotypes per plant. Additionally, we found that genotypes that shared a holdfast had a significantly higher genetic relatedness than the average in the population, compatible with a kin structure. Density dependence and kin structure suggest that the occurrence of plurigenotypic organisms is linked to environmental quality, and that kin or multilevel selection may be favouring the fusion of genetically related genets.  相似文献   

Development of Bench‐Scale Bio‐Packed Column for Wastewater Treatment from Optical Emission Spectrometry     

Kuppusamy Vijayaraghavan  Elvagris Segovia 《洁净——土壤、空气、水》2013,41(11):1093-1099

An eco‐friendly and inexpensive technique for wastewater treatment originated from inductively coupled plasma‐optical emission spectrometry (ICP‐OES) is presented within this paper. The proposed process comprised of loading waste crab shells in packed column for adsorption of heavy metal ions, followed by desorption using 0.01 M HCl. An exhaustive physical and chemical characterization of ICP‐OES wastewater revealed the complex nature of effluent, including the presence of 15 different metals and metalloid under strong acidic condition (pH 1.3). Based on the preliminary batch experiments, it was identified that solution pH played a major role in metal sequestration by crab shell with pH 3.5 identified as optimum pH. Rapid metal biosorption kinetics along with complete desorption and subsequent reuse for three cycles was possible with crab shell‐based treatment process. Continuous flow‐through column experiments confirmed the high performance of crab shell towards multiple metal ions with the column able to operate for 22 h at a flow rate of 10 mL/min before outlet concentration of arsenic reached 0.25 times of its inlet concentration. Other metal ions such as Cu, Cd, Co, Cr, Pb, Ni, Zn, Mn, Al, and Fe were only in trace levels in the treated water until 22 h. The performance of the treatment process was compared with trade effluent discharge standards, and the process flow diagram along with cost analysis was suggested.  相似文献   

Radon emanometry in soil gases and activity in ashes from El Chichon Volcano     

S. De la Cruz-Reyna  M. Mena  N. Segovia  J. F. Chalot  J. L. Seidel  M. Monnin 《Pure and Applied Geophysics》1985,123(3):407-421

Radon (²²²Em) emanation measurements in soil gases are reported in connection with the 1982 eruptions of El Chichón Volcano.²²²Em detection is performed with LR-115 cellulose nitrate track detectors. Results show a general decreasing pattern of²²²Em concentration in soil with time after the eruptions. Activity measurements of radon daughters in ashes show that a large amount of²²²Em and²²⁰Em was released from magma degassing during the eruptions, and that only a fraction of the degassed magma was erupted. An important fluid interaction between the magma chamber and the surrounding sedimentary rock is also suggested.  相似文献   

Seismological study of the central Ecuadorian margin: Evidence of upper plate deformation     

Nicole Bethoux  Monica Segovia  Viviana Alvarez  Jean-Yves Collot  Philippe Charvis  Audrey Gailler  Tony Monfret 《Journal of South American Earth Sciences》2011,31(1):139-152

A seismic study of a segment of the convergent margin of Ecuador is presented. During the SISTEUR campaign a network of 24 Ocean Bottom Seismometers (OBS) was deployed on the Carnegie Ridge, one line along the main axes of the ridge and two lines across the strike of the edge of the ridge, during one month. This marine network was complemented with a land network of 20 stations distributed in two lines: one parallel to the margin and the other perpendicular to it.The seismic event recorded by these networks, were located using different crustal models defined from the wide-angle seismic data modeling. Relative location techniques were used to improve earthquake locations. Seismogram waveform modeling allowed us to constrain hypocentral location for events farther than ～50 km from the network. This modeling also provided additional information to constrain the focal mechanisms of these events. The upper limit of the Interplate Seismogenic Zone (ISZ) is estimated to be at a 10 km depth in the region. The background seismic activity of the upper plate provided new insights:1) A seismic cluster that reaches the base of the overriding plate is linked to the Jipijapa-Portoviejo fault. The reactivation of this Quaternary fault is confirmed by focal mechanisms that provide rupture planes parallel to its superficial projection (N10°–N25°).2) The focal mechanisms presented in this study are compatible with a homogeneous regional stress field corresponding to an E–W to ESE–WNW compression and an NNE–SSW extension. The presence of strike-slip deformation, with a reverse component, corresponds to the NNE escape of the North Andean Block. Normal faulting accommodating this movement suggests that this part of the North Andean Block cannot be considered as a rigid block.  相似文献   

Distribution and enrichment of trace metals and arsenic at the upper layer of sediments from Lerma River in La Piedad,Mexico: case history     

Benjamín Villalobos-Castañeda  Raúl Cortés-Martínez  Nuria Segovia  Otoniel Buenrostro-Delgado  Ofelia Morton-Bermea  Ruth Alfaro-Cuevas-Villanueva 《Environmental Earth Sciences》2016,75(23):1490

Lerma River is one of the largest rivers in Mexico. Over the past 20 years, unplanned population growth occurred along its course and the river has been used as the only outlet for industrial and domestic wastewater disposal. The aim of the present study was to determine trace metals such as Cr, Ni, Cu, Zn, Fe, Pb, and arsenic concentrations at the upper layer of sediments of the Lerma River meander in La Piedad, Michoacan, Mexico. Sediment samples were collected from eight different sites during the rainy and dry seasons. All samples were physically characterized, and concentration values of trace metals and As were determined. On the basis of protection criteria for freshwater sediments, concentrations of Fe, Zn, Cu, Ni, and Pb were found to exceed the lowest effect level; moreover, the concentrations were found to exceed the severe effect level at some sites, particularly for Cu. Statistical analyses showed significant differences between sampling seasons for Fe and As, and among sites for Ni, Cu, Zn, and Pb. In addition, the enrichment factor indicates the following order Zn > Cr > Cu > Ni > Pb > As, and the geoaccumulation index (I _geo) indicates contamination in the following order Zn > Cr > Cu > Ni > As > Pb. The Lerma River meander in La Piedad shows a reduction in pollution by trace metals and arsenic near the drain area and downstream of the meander. However, there are significantly higher concentrations of these elements in sediments of sites located in the middle part of the city.  相似文献