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131.
A re-assessment of the historic seismicity of the central sector of the Colombian Eastern Cordillera (EC) is made by revision of bibliographic sources, by calibration with modern instrumental earthquakes, and by interpretations in terms of current knowledge of the tectonics and seismicity of the region. Throughout the process we have derived an equation to estimate Mw for shallow crustal earthquakes in Colombia using the length of isoseismal VIII, LVIII:
We also derived an equation to evaluate Mw for Colombian crustal earthquakes using the rupture length, L, estimated generally from the aftershock distribution of strong earthquakes:
We calculated average attenuation parameters for intermediate depth and shallow earthquakes that may be used, combined with other observations, to estimate the focal depth of historical events. Our final picture shows three distinct regions of the Colombian Eastern Cordillera (EC) where historical earthquakes are distributed. (a) The southern sector, from the Páramo de Sumapaz down to the Colombian Massif where the largest crustal earthquakes have occurred (1827, M 7 3/4; 1967, Mw = 7.0). (b) The central sector, between the Páramo de Sumapaz and Tunja with moderate to large earthquakes associated to the reverse faults on the piedmonts (the 1805 earthquake, M 6 3/4, on the western flank, and the 1743, 1923 and 1995 with M 6 1/2, 6 3/4, and 6.5, respectively, on the eastern flank). (c) The northern sector, to the north of Tunja, which is characterized by recurrent earthquakes probably associated with major reverse faults in the axial zone (e.g., 1646, I0 = VIII; 1724, M 6 3/4; 1755, I0 VIII; and 1928, M 5 3/4). Two events appear to be related to the axial faults to the south of Bogotá: those in 1644 (M 6) and 1917 (M = 7.1). The 1785 earthquake might have been an intraplate event in the subducting plate under the EC. Events in 1616 and 1826, which caused damage along the axial zone of the Cordillera near Bogotá, have no historical records precise enough to allow the estimation of their location and size, but their epicentres are probably not farther than some tens of kilometers from Bogotá. 相似文献
132.
Representations of the radiated energy in earthquakes 总被引:7,自引:0,他引:7
133.
Vincent J. Pacific Brian L. McGlynn Diego A. Riveros‐Iregui Daniel L. Welsch Howard E. Epstein 《水文研究》2011,25(5):811-827
Variability in soil respiration at various spatial and temporal scales has been the focus of much research over the last decade aimed to improve our understanding and parameterization of physical and environmental controls on this flux. However, few studies have assessed the control of landscape position and groundwater table dynamics on the spatiotemporal variability of soil respiration. We investigated growing season soil respiration in a ~393 ha subalpine watershed in Montana across eight riparian–hillslope transitions that differed in slope, upslope accumulated area (UAA), aspect, and groundwater table dynamics. We collected daily‐to‐weekly measurements of soil water content (SWC), soil temperature, soil CO2 concentrations, surface CO2 efflux, and groundwater table depth, as well as soil C and N concentrations at 32 locations from June to August 2005. Instantaneous soil surface CO2 efflux was not significantly different within or among riparian and hillslope zones at monthly timescales. However, cumulative integration of CO2 efflux during the 83‐day growing season showed that efflux in the wetter riparian zones was ~25% greater than in the adjacent drier hillslopes. Furthermore, greater cumulative growing season efflux occurred in areas with high UAA and gentle slopes, where groundwater tables were higher and more persistent. Our findings reveal the influence of landscape position and groundwater table dynamics on riparian versus hillslope soil CO2 efflux and the importance of time integration for assessment of soil CO2 dynamics, which is critical for landscape‐scale simulation and modelling of soil CO2 efflux in complex landscapes. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
134.
135.
Tree-ring reconstructed dry season rainfall in Guatemala 总被引:1,自引:0,他引:1
Anchukaitis Kevin J. Taylor Matthew J. Leland Caroline Pons Diego Martin-Fernandez Javier Castellanos Edwin 《Climate Dynamics》2015,45(5-6):1537-1546
Climate Dynamics - Drought in Guatemala has negative consequences for agriculture and potable water supplies, particularly in regions of the country with highly seasonal rainfall. General... 相似文献
136.
Integrated assessment of smallholder farming’s vulnerability to drought in the Brazilian Semi-arid: a case study in Ceará 总被引:1,自引:0,他引:1
Diego Pereira Lindoso Juliana Dalboni Rocha Nathan Debortoli Izabel Ibiapina Parente Flávio Eiró Marcel Bursztyn Saulo Rodrigues-Filho 《Climatic change》2014,127(1):93-105
Smallholder farming is among the most vulnerable sectors due to its great social and economic sensitivity. Despite future climate change, current climate variability is already an issue of concern that justifies adaptation efforts. In Brazil, the Semi-Arid Region is a climate hotspot, well known for both historic socioeconomic setbacks, and agriculture failures caused by dry spells and severe droughts. In 2010, the Brazilian government enacted the National Policy on Climate Change, which states as one of its key goals the identification of vulnerabilities and the adoption of adequate measures of adaptation to climate change. The improvement of vulnerability assessment tools is a response to the growing demand of decision makers for regular information and indicators with high spatial and temporal resolution. This article aims at undertaking a comparative assessment of smallholder farming’s vulnerability to droughts. An integrated assessment system has been developed and applied to seven municipalities located in the Brazilian Semi-Arid Region (within the State of Ceará). Results show regional vulnerability contrasts driven by institutional and socioeconomic factors, beyond climatic stressors. 相似文献
137.
Avellaneda PM Englehardt JD Olascoaga J Babcock EA Brand L Lirman D Rogge WF Solo-Gabriele H Tchobanoglous G 《Marine pollution bulletin》2011,62(10):2157-2169
A relative risk assessment of biosolids disposal alternatives for cruise ships is presented in this paper. The area of study encompasses islands and marine waters of the Caribbean Sea. The objective was to evaluate relative human health and ecological risks of (a) dewatering/incineration, (b) landing the solids for disposal, considering that in some countries land-disposed solids might be discharged in the near-shore environment untreated, and (c) deep ocean disposal. Input to the Bayesian assessment consisted of professional judgment based on available literature and modeling information, data on constituent concentrations in cruise ship biosolids, and simulations of constituent concentrations in Caribbean waters assuming ocean disposal. Results indicate that human health and ecological risks associated with land disposal and shallow ocean disposal are higher than those of the deep ocean disposal and incineration. For incineration, predicted ecological impacts were lower relative to deep ocean disposal before considering potential impacts of carbon emissions. 相似文献
138.
Luca Caricchi Anne Pommier Mattia Pistone Jonathan Castro Alain Burgisser Diego Perugini 《Bulletin of Volcanology》2011,73(9):1245-1257
Experiments have been performed to determine the effect of deformation on degassing of bubble-bearing melts. Cylindrical specimens
of phonolitic composition, initial water content of 1.5 wt.% and 2 vol.% bubbles, have been deformed in simple-shear (torsional
configuration) in an internally heated Paterson-type pressure vessel at temperatures of 798–848 K, 100–180 MPa confining pressure
and different final strains. Micro-structural analyses of the samples before and after deformation have been performed in
two and three dimensions using optical microscopy, a nanotomography machine and synchrotron tomography. The water content
of the glasses before and after deformation has been measured using Fourier Transform Infrared Spectroscopy (FTIR). In samples
strained up to a total of γ ∼ 2 the bubbles record accurately the total strain, whereas at higher strains (γ ∼ 10) the bubbles
become very flattened and elongate in the direction of shear. The residual water content of the glasses remains constant up
to a strain of γ ∼ 2 and then decreases to about 0.2 wt.% at γ ∼ 10. Results show that strain enhances bubble coalescence
and degassing even at low bubble volume-fractions. Noticeably, deformation produced a strongly water under-saturated melt.
This suggests that degassing may occur at great depths in the volcanic conduit and may force the magma to become super-cooled
early during ascent to the Earth’s surface potentially contributing to the genesis of obsidian. 相似文献
139.
Barbara Borzi Fabio Dell��Acqua Marta Faravelli Paolo Gamba Gianni Lisini Mauro Onida Diego Polli 《Bulletin of Earthquake Engineering》2011,9(2):675-690
The aim of this paper is to disseminate knowledge in the seismic science community about a possible tool which is not largely
popular, despite its potential usefulness. In this paper it will be shown how satellite remotely sensed images may represent
a powerful source of information where traditional sources of information are unable to deliver it, or at least to do so timely.
Even when traditional information flow can ensure delivery, an advantage may still be found in terms of sooner availability
and smaller amount of labour required. In the case shown here a vulnerability study was made on a vast industrial area in
the gulf of Siracusa, Sicily, Italy. A series of concurrent factors made it particularly troublesome to obtain information
on the structures found in the site (tanks, pipes, chimneys, roads, ...), required to suitably carry out the study. Satellite
images were then acquired to obtain the information needed. Processing of the images was carried out relying on in-house software
formerly developed for similar information extraction issues, and integrated with new, specifically developed elements, some
pieces of information were obtained useful for seismic risk evaluation. In particular, location, footprint, elevation of significant
structures (e.g. tanks, chimneys) could be evaluated, obtaining results in a format compatible with the most widespread GIS
(Geographic Information System) standards. Such compatibility allowed a considerable savings on labour time required to lay
a GIS of the area, which is a fundamental tool for risk and vulnerability analyses. 相似文献
140.