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61.
Claudia Beatriz Quinteros Cartaya Fidencio Alejandro Nava Pichardo Ewa Glowacka José Duglas Frez Cárdenas 《Pure and Applied Geophysics》2014,171(7):1367-1383
In order to analyze observed seismicity in central Japan and Venezuela, we applied a new method to identify semi-periodic sequences in the occurrence times of large earthquakes, which allows for the presence of multiple periodic sequences and/or events not belonging to any sequence in the time series. We also explored a scheme for diminishing the effects of a sharp cutoff magnitude threshold in selecting the events to analyze. A main four-event sequence with probability P c = 0.991 of not having occurred by chance was identified for earthquakes with M ≥ 8.0 in central Japan. Venezuela is divided, from West to East, into four regions; for each of these, the magnitude ranges and identified sequences are as follows. Region 1: M ≥ 6.0, a six-event sequence with P c = 0.923, and a four-event sequence with P c = 0.706. Region 2: M ≥ 5.6, a five-event sequence with P c = 0.942. Region 3: M ≥ 5.6, a four-event sequence with P c = 0.882. Region 4: M ≥ 6.0, a five-event sequence with P c = 0.891. Forecasts are made and evaluated for all identified sequences having four or more events and probabilities ≥0.5. The last event of all these sequences was satisfactorily aftcast by previous events. Whether the identified sequences do, in fact, correspond to physical processes resulting in semi-periodic seismicity is, of course, an open question; but the forecasts, properly used, may be useful as a factor in seismic hazard estimation. 相似文献
62.
Fidencio Alejandro Nava Pichardo Claudia Beatriz Quinteros Cartaya Ewa Glowacka José Duglas Frez Cárdenas 《Pure and Applied Geophysics》2014,171(7):1355-1366
We present a new method to identify semi-periodic sequences in the occurrence times of large earthquakes, which allows for the presence of multiple semi-periodic sequences and/or events not belonging to any identifiable sequence in the time series. The method, based on the analytic Fourier transform, yields estimates of the departure from periodicity of an observed sequence, and of the probability that the sequence is not due to chance. These estimates are used to make and to evaluate forecasts of future events belonging to each sequence. Numerous tests with synthetic catalogs show that the method is surprisingly capable of correctly identifying sequences, unidentifiable by eye, in complicated time series. Correct identification of a given sequence depends on the number of events it contains, on the sequence’s departure from periodicity, and, in some cases, on the choice of starting and ending times of the analyzed time window; as well as on the total number of events in the time series. Some particular data combinations may result in spectra where significant periods are obscured by large amplitudes artifacts of the transform, but artifacts can be usually recognized because they lack harmonics; thus, in most of these cases, true semi-periodic sequences may not be identified, but no false identifications will be made. A first example of an application of the method to real seismicity data is the analysis of the Parkfield event series. The analysis correctly aftcasts the September 2004 earthquake. Further applications to real data from Japan and Venezuela are shown in a companion paper. 相似文献
63.
Isidro A. Pérez M. Luisa Sánchez M. Ángeles García Beatriz de Torre 《Theoretical and Applied Climatology》2009,98(3-4):269-277
CO2 in the rural atmosphere is related to respiration–photosynthesis processes, although the evolution of the low atmosphere is also a determinant factor. CO2 concentrations were measured at surface and meteorological variables obtained from a radio acoustic sounding system sodar at a flat rural site during a 3-year campaign. Yearly and daily cycles of CO2 were described. Maxima were observed in spring and autumn during the night. Wind speed and thermal structure of the lower atmosphere were analysed. Low level jets were observed during the night, their core proving lower in summer. Surface inversions observed with low winds reached up to 100 m. The turbulence layer which developed during the day extended up to 300–400 m and was capped by a stable layer. Median vertical wind speed reached 1 m s?1 in super-adiabatic conditions in summer. Determination of decoupled low level jets proved difficult with the device used and corresponding concentrations were slightly higher than medians calculated with all the observations. The bulk Richardson number was calculated in the lower atmosphere and four intervals were considered: drainage, transitional, shear flows and unstable conditions. Median CO2 concentrations were split according to these intervals. Higher values corresponded to drainage flow, which was associated to more stable conditions being less frequent and lower values to shear flow and unstable conditions, revealing a satisfactory link between the bulk Richardson number as a turbulence indicator in the low atmosphere and CO2 surface concentrations. 相似文献
64.
The upper Kimmeridgian outcrops in Jabaloyas (NE Spain) studied here have significant similarity in terms of carbonate ramp morphology and its facies architecture with Member D of the Upper Jurassic Arab Formation reservoirs in the Middle East. Geological models from analogue outcrops enhance or challenge the understanding of multi-scale sedimentological and diagenetic heterogeneities in the subsurface hydrocarbon reservoir models by providing morphometric parameters. For this purpose, conventional diagenetic studies (petrographic microscopy analysis and cathodoluminescence) have been performed to assess the impact of diagenetic modifications through burial. More than 50 thin sections have been used to define a full paragenetic sequence. Additional mineralogical mapping (Qemscan®) on a selection of thin sections serves as a calibration tool for semiquantitative analytic studies of every mineral phases and the proposed porosity evolution. This work unravels the whole paragenetic diagenetic processes and focused on those that occurred right after deposition to shallow burial (eogenesis). High-sequence stratigraphy allows linking these events to variations of the environmental domains that, in fact, respond most likely to sea-level fluctuations. In particular, it provides key parameters to frame the diagenetic overprint such as cementation processes plugging primary interparticle porosity and selective dissolution linked to master bounding surfaces: calcite meniscus cements in vadose zones and selective dissolution processes linked to firmgrounds. Ultimately, they offer valuable trends that would be potentially relevant to decipher and characterize reservoir parameters for the upscaling workflow of fabrics from microscopic to inter-well scale in carbonate hydrocarbon reservoirs. 相似文献
65.
Beatriz Melba Honnorez-Guerstein 《Mineralium Deposita》1971,6(2):111-121
The copper deposit La Leona consists of ore veins in a granite batholite which intruded into Permian sediments. In these veins the following minerals are observed: pyrite, sphalerite, chalcopyrite, galena, betekhtinite, two Bisulfosalts, electrum, bornite, chalcocite, enargite, tennantite, Zn-Fahlerz, cuprite, delafossite, molybdenite, hematite and iron hydroxides, and copper carbonates with quartz and iron carbonates as gangue. The betekhtinite, (CuFe)10Pb S6, found for the first time in Argentina, the Zn-Fahlerz and the sulfosalts (Cu3.2Bi1.2Pb1.2S8.5) and (Cu9.3Bi1.1S6.8) were studied in detail under the microscope, by X-rays and by microprobe. Specifically, the paragenesis of these three minerals with galena, chalcocite and bornite is discussed.
Résumé Le gisement de cuivre de la mine «La Leona» est formé de filons de minerais recoupant un batholite granitique qui a fait intrusion dans des sédiments permiens. Les minéraus suivants ont été observés: pyrite, blende, chalcopyrite, galène, bétekhtinite, deux sulfosels de Bi, électrum, bornite, chalcosine, énargite, tennantite, «Zn-Fahlerz», cuprite, delafossite, molybdénite, hématite et hydroxydes de fer, des carbonates de cuivre, dans une gangue de quartz et de carbonates de fer. La bétekhtinite (Cu Fe)10Pb S6, trouvée pour la première fois en Argentine, le «Zn-Fahlerz» et les sulfosels (Cu3.2Bi1.2Pb1.2S8.5) et (Cu9.3Bi1.1S6.8) ont été spécialement étudiés à l'aide de la microscopie, de la diffraction des rayons-X et de la microsonde. La paragénèse formée par ces trois mineraux associés à la galène, la chalcosine et la bornite est discutée.相似文献
66.
67.
Torres MA Testa CP Gáspari C Masutti MB Panitz CM Curi-Pedrosa R de Almeida EA Di Mascio P Filho DW 《Marine pollution bulletin》2002,44(9):923-932
Digestive glands of the mangrove mussel Mytella guyanensis, collected at one non-polluted site (site 1) and two polluted sites (sites 2 and 3), were analysed for different antioxidant defenses, lipid peroxidation and DNA damage. Thiobarbituric acid-reactive substance (TBARS) and 8-oxo-7,8-dihydro-2'-deoxyguanosine levels were enhanced at the polluted sites. With the exception of superoxide dismutase, the activities of catalase and glutathione peroxidase were also higher at the polluted sites. Greater increases were observed in glutathione reductase, glutathione S-transferase and etoxyresorufine-O-deethylase activities at the polluted sites. Conversely, reduced glutathione content was higher at the control site. Trace metal contents in mussels collected at polluted sites were increased compared to the control site, and there were strong positive correlations between TBARS and Cu and Pb contents. M. guyanensis is routinely exposed to an oxidative stress condition at both polluted sites, and considering xenobiotic bioaccumulation in bivalve molluscs, the mangrove mussel represents an excellent bioindicator for environmental monitoring studies. 相似文献
68.
Maria Socorro Lozano-García Beatriz Ortega-Guerrero Margarita Caballero-Miranda Jaime Urrutia-Fucugauchi 《Quaternary Research》1993,40(3)
In order to establish paleoenvironmental conditions during the late Quaternary, four cores from the Basin of Mexico (central Mexico) were drilled in Chalco Lake, located in the southeastern part of the basin. The upper 8 m of two parallel cores were studied, using paleomagnetic, loss-on-ignition, pollen, and diatom analyses. Based on 11 14C ages, the analyzed record spans the last 19,000 14C yr B.P. Volcanic activity has affected microfossil abundances, both directly and indirectly, resulting in absence or reduction of pollen and diatom assemblages. Important volcanic activity took place between 19,000 and 15,000 yr B.P. when the lake was a shallow alkaline marsh and an increase of grassland pollen suggests a dry, cold climate. During this interval, abrupt environmental changes with increasing moisture occurred. From 15,000 until 12,500 yr B.P. the lake level increased and the pollen indicates wetter conditions. The highest lake level is registered from 12,500 to ca. 9000 yr B.P. The end of the Pleistocene is characterized by an increase in humidity. From 9000 until ca. 3000 yr B.P. Chalco Lake was a saline marsh and the pollen record indicates warmer conditions. After 3000 yr B.P. the lake level increased and human disturbance dominates the lacustrine record. 相似文献
69.
During a summer period we studied the vertical variation of in vivo and chlorophyll a specific phytoplankton absorption spectra in relation to the underwater light climate of ten deep North Patagonian Andean lakes of Argentina. The lakes were thermally stratified, and the underwater light climate was characterized by extended euphotic zones which included highly illuminated epilimnetic layers (both UVR and PAR) and metalimnia exposed to dim blue-green light. Most of the lakes presented the development of Deep Chlorophyll Maxima (DCM) at the metalimnetic layers, near 1% of surface PAR irradiance. Analyzing the fourth-derivative plots of in vivo phytoplankton absorption spectra [dIVaph(λ)], we were able to identify several maxima absorption values attributed to different pigments. Considering lakes with DCM, a significant positive linear relationship was found between dIVaph (495–500 nm) normalized by chlorophyll a and downward irradiance. Indeed, a negative significant relationship was found between dIVaph (495–500 nm) normalized by chlorophyll a and diffuse PAR attenuation coefficients. These results point out an increase in the relative concentration of different carotenoids at surface layers indicating the role of photoprotection of these pigments. On the other hand, significant negative linear relationships were found between fourth-derivative spectra normalized by chlorophyll a at 650, 590–595, 560–565 and 520–525 nm and downward irradiance. These results indicated an increase in the relative concentration of photosynthetic accessory pigments at deep layers of the euphotic zone. Furthermore, we found a decrease in depth of specific absorption spectra at 440, 670 nm and in the ratio aph* (440 nm) to aph* (670 nm). This pattern was associated with the package effect concept. The increase in relative photosynthetic accessory pigment concentrations and the decrease in values of specific absorption spectra at the bottom of the euphotic zone were attributed to changes in phytoplankton communities between surface and deep layers. These outcomes pointed out that the underwater light climate and temperature water structure are, like in marine systems, very important factors governing the distribution of phytoplanktonic organisms. In addition, the possession of specific photosynthetic accessory pigments suggests that dominant species in the DCM are well adapted to these dim blue-green light scenarios. 相似文献
70.
Autieres Teixeira Faria Matheus Freitas Souza Ana Beatriz Rocha de Jesus Passos Antonio Alberto da Silva Daniel Valadão Silva José Cola Zanuncio Paulo Roberto Ribeiro Rocha 《Environmental Earth Sciences》2018,77(5):214
Underground contamination water by herbicides depends on the interactions between their molecules with physical and chemical soil characteristics and climatic conditions. Studies with columns can estimate the leaching potential of herbicides in soils. This study aimed to determine the effect of soil pH on tebuthiuron leaching, and capacity of bioindicators to detect tebuthiuron residues in three Brazilian soils. Cucumber plants (Cucumis sativus) were more negatively affected when grown in soils with lower amounts of organic matter and clay, and in these soils, the tebuthiuron levels reached greater depths in the column. There was a positive correlation between tebuthiuron concentration and cucumber intoxication, and a negative correlation between tebuthiuron concentration and dry matter cucumber in all soils. The tebuthiuron leached up to 50 cm depth even in soils with higher organic matter and clay content. The increasing of soil pH can affect the leaching of nonionic herbicides, and liming practice may elevate the environmental contamination risk by tebuthiuron. The bioindicator method using Cucumis sativus is viable and can be recommended to detect tebuthiuron concentrations above 0.2 mg kg?1. 相似文献