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601.
Elizabeth Dologlou 《International Journal of Earth Sciences》2014,103(6):1725-1728
An independent approach, based on a power law relation interconnecting the lead time of precursory signals and the stress drop of forthcoming earthquake, confirms the reported evidence that the observed magnetic field anomaly and consequently, according to Maxwell’s laws, electric field anomaly prior to Mw 6.3 Aquila earthquake in 2009 exhibit features of criticality. Precisely, by inserting the data from Aquila earthquake in this power law, we get an exponent α = 0.329, which is in excellent agreement with previously found ones and falls within the range values (0.3–0.4) for critical exponents for fracture. This fact implies that upon the initiation of the observed magnetic field anomaly and the associated electric signal prior to Aquila earthquake, the prefocal area enters into a critical stage where nonlinear dynamic processes, typical behaviour of a system close to criticality, prevail. 相似文献
602.
Ofelia Morton-Bermea Juan Miguel Gómez-Bernal María Aurora Armienta Rufino Lozano Elizabeth Hernández-Álvarez Francisco Romero Javier Castro-Larragoitia 《Environmental Earth Sciences》2014,71(12):5207-5213
The present work aims to assess the efficiency of heavy metal accumulation of native species growing in contaminated soils in the mining district of Taxco, Mexico. Soil and tailing sampling was conducted in three study sites: La Concha, El Fraile, and a control site. The study localities present diverse metal concentrations with significant differences in their proportion in the geochemical fractions. Results show that species Cupressus lindleyi and Juniperus deppeana accumulate Zn and Mn in anomalous concentrations at La Concha, where Zn is present in soluble fractions. Manganese, despite not being present mostly in the soluble fraction in soils and tailings, seems to have been increased in the soluble fraction after the plant growth. In contrast, samples of the same species taken at El Fraile and in the control site, where Zn and Mn are mainly contained in the residual fraction, do not show an anomalous enrichment. Other analyzed species growing under the same contamination conditions in La Concha (Jacaranda mimosifolia and Psidium guajava) do not show anomalous concentrations. These facts confirm the Zn and Mn accumulation capacity of C. lindleyi and Ju. deppeana, which depends on their accumulation ability and on the concentration of these elements in the soluble fraction. 相似文献
603.
Ricardo Vega-Granillo Alicia Sarmiento-Villagrana Sergio Salgado-Souto Elizabeth Araux-Sánchez 《International Geology Review》2017,59(7):812-828
The Western Sonobari Complex in northwestern Mexico consists of metamorphosed rocks mostly derived from Palaeozoic (?) sedimentary and Mesozoic igneous protoliths. Rocks of this complex display amphibolite facies orogenic metamorphism, pervasive foliation, migmatization, and four folding phases. These features are ascribed to a contractional tectonic event with NNW–SSE shortening direction, which caused thrusting, thickening of the crust, and sinking of the lithological units. U–Pb geochronology of migmatitic leucosome bands indicates that peak metamorphic conditions were reached between ~93 and 89 Ma. Post-tectonic Late Cretaceous peraluminous aplite-pegmatite dikes transect the metamorphic foliation. Traditional thermobarometry in the metamorphic rocks yields average pressures and temperatures of 9.0–7.1 kbar and 745–663°C, typical of intermediate P/T Barrovian metamorphism. On the basis of its age and contractional character, the thickening event originating the metamorphism may be related to collision of the Alisitos island arc against crustal blocks of Mexico. Thermobarometric data of post-tectonic intrusives including Late Cretaceous granodiorite and Eocene gabbro indicate emplacement within an overthickened crust, while P-T conditions of post-tectonic dikes point towards an almost isothermal decompression path along the amphibolite facies field. Rock units of similar age and metamorphic character are discontinuously exposed from the Islas Marias offshore the Nayarit coast to the Peninsular Ranges batholith of Baja California, and even extend north into the Sierra Nevada batholith and the Sevier hinterland. This extensive belt of Barrovian metamorphic rocks thus provides a record of middle Cretaceous shortening and crustal thickening related to arc-continent collision followed by subduction resuming. 相似文献
604.
Petrologic and experimental evidence for the movement and heating of the pre-eruptive Minoan rhyodacite (Santorini, Greece) 总被引:1,自引:1,他引:0
Elizabeth Cottrell James E. Gardner Malcolm J. Rutherford 《Contributions to Mineralogy and Petrology》1999,135(4):315-331
Hydrothermal experiments combined with petrologic observations form the basis for a new two-stage model for the evolution
of the pre-eruption Minoan magma chamber at Santorini, Greece. Ninety-nine percent of the erupted volume is two-pyroxene,
rhyodacitic magma that had been stored at a temperature of ∼885 °C, based on magnetite-ilmenite and QUILF geothermometry.
The rest of the volume is basaltic to andesitic magma, which occurs as <10 cm scoria clasts and as small inclusions in rhyodacite
pumices. Petrologic observations show that these magmas mixed at different scales and at different times (i.e., multiple batches
of mafic magma). Hydrothermal experiments were carried out on samples of rhyodacite and a mafic scoria in order to determine
magma storage conditions and the mixing history of the two magmas. At 885 °C, the rhyodacite must have been stored at water-saturated
pressures of ∼50 MPa, based on its phase assemblage, matrix-glass composition, and crystal content. However, glass inclusions
inside rhyodacitic plagioclase phenocrysts contain more than 6 wt% H2O, indicating they formed at pressures >200 MPa. In addition, the composition of the plagioclase hosts (An56 ± 6) of the inclusions require temperatures of 825 ± 25 °C at pressures >200 MPa. This demonstrates that the Minoan rhyodacitic
magma underwent a two-stage evolution, first crystallizing at ∼825∘C and >200 MPa, and then rinsing to a shallow ∼50 MPa storage region with a concomitant rise in temperature to ∼885 °C. We
suggest that the episodic intrusion of mafic magmas provided the necessary heat and perhaps contributed to the ascent of the
magma to shallow crustal depths where it reequilibrated before the cataclysmic eruption. Phase equilibria suggest that much
of the heating of the rhyodacite occurred in the shallow storage region. Thermal budget calculations suggest that the rhyodacite
magma could have been heated by intrusions of basalt rising at reasonable upwelling rates and injected into the storage zone
over several hundred years. Preservation of amphibole in the mafic scoria indicate that injection of mafic magma continued
up until days before the cataclysmic eruption, perhaps triggering the event.
Received: 30 September 1997 / Accepted: 5 October 1998 相似文献
605.
Local vs. Regional Groundwater Flow Delineation from Stable Isotopes at Western North America Springs 下载免费PDF全文
The recharge location for many springs is unknown because they can be sourced from proximal, shallow, atmospheric sources or long‐traveled, deep, regional aquifers. The stable isotope (18O and 2H) geochemistry of springs water can provide cost‐effective indications of relative flow path distance without the expense of drilling boreholes, conducting geophysical studies, or building groundwater flow models. Locally sourced springs generally have an isotopic signature similar to local precipitation for that region and elevation. Springs with a very different isotopic composition than local meteoric inputs likely have non‐local recharge, representing a regional source. We tested this local vs. regional flow derived hypothesis with data from a new, large springs isotopic database from studies across Western North America in Arizona, Nevada, and Alberta. The combination of location‐specific precipitation data with stable isotopic groundwater data provides an effective method for flow path determination at springs. We found springs in Arizona issue from a mix of regional and local recharge sources. These springs have a weak elevation trend across 1588 m of elevation where higher elevation springs are only slightly more depleted than low elevation springs with a δ18O variation of 5.9‰. Springs sampled in Nevada showed a strong elevation‐isotope relationship with high‐elevation sites discharging depleted waters and lower elevation springs issuing enriched waters; only a 2.6‰ difference exists in 18O values over an elevation range of more than 1500 m. Alberta's springs are mostly sourced from local flow systems and show a moderate elevation trend of 1200 m, but the largest range in δ18O, 7.1‰. 相似文献
606.
Samuel V. Panno Walton R. Kelly John Scott Wei Zheng Rachel E. McNeish Nancy Holm Timothy J. Hoellein Elizabeth L. Baranski 《Ground water》2019,57(2):189-196
Groundwater in karst aquifers constitutes about 25% of drinking water sources globally. Karst aquifers are open systems, susceptible to contamination by surface-borne pollutants. In this study, springs and wells from two karst aquifers in Illinois, USA, were found to contain microplastics and other anthropogenic contaminants. All microplastics were fibers, with a maximum concentration of 15.2 particles/L. The presence of microplastic was consistent with other parameters, including phosphate, chloride and triclosan, suggesting septic effluent as a source. More studies are needed on microplastic sources, abundance, and impacts on karst ecosystems. 相似文献
607.
Konstantinos Papadopoulos Elizabeth Vintzileou Ioannis N. Psycharis 《地震工程与结构动力学》2019,48(13):1432-1450
This paper presents a numerical study of the response to earthquake actions of eight ancient Greek multidrum columns, which were chosen as representative of a broad spectrum of the ancient columns preserved to date. The study was conducted using the FE software Abaqus, in three steps. At first, the software efficiency to predict the rocking response of dry-stone structures was verified. Afterwards, various numerical models of one typical ancient multidrum column were seismically excited. Records of four real earthquakes differing in frequency content were used for the excitation of the models. Each column model was different from the others at least in one geometric or modeling parameter. Although the examined parameters affected the numerical results, their variation did not alter significantly the overall behavior of the column. In the last step of the study, numerical models of eight columns were seismically excited using four seismic records. In these analyses, among the simulation approaches tested in the second step, the simpler one was adopted. On the basis of the numerical results, conclusions were drawn regarding the seismic resistance of the columns and its correlation with the dynamic characteristics of the columns (size, slenderness, and frequency parameter) and with the basic intensity measures and frequency content indicator of the seismic motions (PHA, PHV, PHD, and Tg). Thus, criteria of seismic collapse for the multidrum columns are proposed, which can be used for the approximate assessment of the seismic vulnerability of free-standing ancient columns, provided that the columns are in good preservation state. 相似文献
608.
Soils‐based evidence derived from thin section micromorphology is used to explore contrasts in pre‐Hispanic and Hispanic arable land management practices associated with raised fields in an inter‐Andean valley of Ecuador. Differences in textural pedofeature characteristics suggest that, where they are found in the same locality, camellón systems were more intensively manured and cultivated than wachu systems. Both, however, were more intensively managed than traditional Hispanic arable fields. The importance of the camellón in pre‐Hispanic agriculture is emphasized by soils‐based evidence that highlights the efforts made to clear these fields of volcanic ash after the Quilotoa eruption of ca. A.D. 1280. This research suggests that, in an andosol context, pre‐Hispanic and Hispanic arable land management practices leave relict and fossil soil micromorphology features that can be used to interpret land use intensities. © 2002 Wiley Periodicals, Inc. 相似文献