Simulation of ground motion in the Moscow region using the empirical Green’s function     

V. V. Bykova  S. S. Aref’ev  L. Rivera 《Izvestiya Physics of the Solid Earth》2010,46(1):19-33

Historically, the Moscow region regularly experienced rather weak but quite perceptible seismic vibrations produced by intermediate-depth earthquakes of the Vrancea zone (Romania), located at a distance of 1400 km from Moscow. The coincidence of a number of unique factors such as a slowly varying focal depth, predominant source mechanisms, weak attenuation of seismic radiation in the north-northeast direction provide favorable conditions for application of the empirical Green’s function method. Using the digital seismogram of the Vrancea Mw-5.8 earthquake recorded at the Moscow seismic station, we simulated synthetic seismograms of a scenario (expected maximum) earthquake with Mw = 8.0, by application of the empirical Green’s function method adjusted for the given conditions. The calculation procedure was verified using analog records of strong earthquakes available at the Moscow seismic station. Digital records of the Obninsk seismic station included in the Incorporated Research Institutions for Seismology (IRIS) system were used for additional control. Here, the scenario earthquake was modeled using the data on a much stronger earthquake of 1990 (MW = 6.9). It is shown that, despite a certain scatter (quite adequately assessed in the scope of the method), the ultimate estimates of expected seismic impacts are quite reliable and can be recommended for practical use.  相似文献   

Numerical simulation of groundwater flow in regional rock aquifers, southwestern Quebec, Canada   总被引：1，自引：1，他引：0  

M. Nastev  A. Rivera  R. Lefebvre  R. Martel  M. Savard 《Hydrogeology Journal》2005,13(5-6):835-848

The St. Lawrence Lowlands platform, Quebec, Canada, is a densely-populated area, heavily dependent on groundwater resources. In 1999, the Geological Survey of Canada initiated a large-scale hydrogeological assessment study over a 1,500 km² region northwest of Montreal. The objectives were to define the regional groundwater flow, and to give quantitative estimates of the groundwater dynamic parameters and of the available groundwater resources. The applied approach consisted of defining the hydrogeologic framework, hydraulic properties of the aquifer units, and groundwater dynamic components. Lower Paleozoic sedimentary rocks represent regional aquifer units. Coarse Quaternary fluvio-glacial sediments locally overlay the rock sequence and constitute an interface aquifer unit. Fine marine sediments confine most of the regional aquifers. Collected GIS based information was synthesized in a finite element numerical model. The regional saturated steady-state flow was calibrated under current stress conditions assuming an equivalent porous medium approach. Water budget calculations show that the total groundwater flow in regional aquifers amounts to 97.7 Mm³/y. Infiltration from precipitation provides 86.6% of the groundwater supply, while 9.6% comes from subsurface inflow and the remaining 3.8% is induced recharge from surface waters. Discharge from regional aquifers occurs through flow to streams (76.9%), groundwater withdrawal (18.4%), and underground outflow (4.7%).

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Resumen La plataforma de Tierras Bajas San Lorenzo, Quebec, Canadá, es un área densamente poblada que depende fuertemente de recursos de agua subterránea. En 1999 el Servicio Geológico de Canadá inició un estudio de evaluación hidrogeológica a gran escala sobre un área de 1,500 km² en la región noroeste de Montreal. Los objetivos fueron definir el flujo regional de agua subterránea y aportar estimados cuantitativos de los parámetros dinámicos de agua subterráne y de los recursos disponibles de agua subterránea. El enfoque aplicado consistió en definir el marco hidrogeológico, propiedades hidráulicas de las unidades acuíferas, y los componentes dinámicos de agua subterránea. Rocas sedimentarias del Paleozoico Inferior representan unidades regionales de acuíferos. Sedimentos fluvio-glaciares Cuaternarios gruesos sobreyacen localmente la secuencia rocosa y constituyen una unidad acuífera interfacial. Sedimentos marinos finos confinan la mayoría de acuíferos regionales. Información colectada basada en SIG se sintetizó en un modelo numérico de elemento finito. El flujo regional saturado en régimen permanente se calibró bajo condiciones de stress asumiendo un enfoque de medio poroso equivalente. Los cálculos de balance hídrico muestran que el flujo total de agua subterránea en acuíferos regional alcanza 97.7 Mm³/año. Infiltración a partir de lluvia aporta el 86.6% del abastecimiento al agua subterránea, mientras que el 9.6% proviene de entradas subsuperficiales y el restante 3.8% consiste de recarga inducida a partir de aguas superficiales. La descarga proveniente de acuíferos regionales ocurre a través de flujo a ríos (76.9%), utilización de agua subterránea (18.4%), y salida subterránea (4.7%).

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Résumé La plateforme Lowllands du Saint-Laurent, Québec, Canada, est une aire densément peuplée, dépendant grandement des ressources en eau souterraine. En 1999, le Service Géologique du Canada a initié une étude hydrogéologique à grande-échelle sur 1500 km² au Nord-Ouest de Montréal. Le sobjectifs ont été de définir la dynamique de lécoulement régional, et de donner des estimations quantitatives des paramètres dynamiques des ressources disponibles en eau souterraine. Lapproche utilisée consista à définir le cadre hydrogéologique de travail, les propriétés hydrauliques des unités aquifères, et les composantes dynamiques des eaux souterraines. Les roches sédimentaires du Paléozoïque Inférieur représentent les unités aquifères régionales. Les sédiments marins fins confinent la plus grande partie des aquifères régionaux. Les informations de base, collectées dans un SIG, ont été synthétisées dans un modèle numérique aux éléments finis. Lécoulement permanent régional, en zone saturée, a été calibré en conditions de stress en assumant une approche de milieu poreu équivalent. Les calculs du bilan hydrologique montrent que lécoulement total des eaux souterraines dans les aquifères régionaux atteind 97,7 Mm³/an. Linfiltration à partir des précipitations apporte 86.6% de leau souterraine exploitée; sachant que 9,6% proviennent découlement de subsurfaces, et que les 3,8% restants proviennent de la recharge via les eaux de surface. Le débit pompé des aquifères régionaux apparaît à travers lécoulement des cours deau, le rabattement des eaux souterraines (18.4%), et lécoulement ascendant (4.7%).

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Intermittency of riometer auroral absorption observed at South Pole     

M.V. Stepanova  E.E. Antonova  A.J. Foppiano  T.J. Rosenberg  E.M. Ovalle 《Journal of Atmospheric and Solar》2005,67(17-18):1876

Auroral radio-wave absorption values measured at South Pole for 3 years using a riometer are analyzed in order to test whether they show evidence of intermittency. The properties of the parameters of the probability density functions determined for several magnetic local time sectors are found to be significantly different. The probability density functions for the pre-midnight sector show the typical shape associated to intermittency. No results are given for the afternoon sector because few auroral absorption events meet the selection criteria to give statistically significant results. It is suggested that if the precipitating particle population responsible for the riometer auroral absorption shared the intermittency features of the absorption then the present results would allow the study of the properties of the induction component of magnetospheric turbulence.  相似文献   

A bitter cup: climate change profile of global production of Arabica and Robusta coffee   总被引：4，自引：3，他引：1  

Christian Bunn  Peter Läderach  Oriana Ovalle Rivera  Dieter Kirschke 《Climatic change》2015,129(1-2):89-101

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Book review: Groundwater for the 21st Century: A Primer for Citizens of Planet Earth,by John A. Conners (McDonald & Woodward Publishing Co., USA, 2013)     

Alfonso Rivera 《Hydrogeology Journal》2014,22(6):1487-1488

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Assessment of the distribution of sponge chips in the sediment of East Pacific Ocean reefs          下载免费PDF全文

Jose Luis Carballo  Humberto Ovalle‐Beltrán  Benjamin Yáñez  Eric Bautista‐Guerrero  Héctor Nava‐Bravo 《Marine Ecology》2017,38(1)

Sponges are one of the principal agents of bioerosion and sediment production in coral reefs. They generate small carbonate chips that can be found in the sediments, and we investigated whether these could provide a means for assessment of bioerosion applicable to reef monitoring. We tested this hypothesis on samples from 12 Mexican coral reefs distributed along the Pacific coast, where boring sponges were particularly abundant, and quantified the amount of chips in samples of superficial sediment in three grain‐size fractions: fine (<44 μm), medium (44–210 μm) and coarse (>210 μm). The grain‐size distribution varied among reefs, with the majority of the sediment of most reefs being composed of coarse sands, and the medium and fine fractions dominating only at La Entrega and Playa Blanca. All the reefs presented clear evidence of bioerosion by sponges, with the characteristic chips present in the sediment, although at most sites the percentage of chips was very low (from 1% to 3% of the total sediment). Only at La Entrega and Playa Blanca did they constitute a significant fraction of the total sediment (18% and 16%, respectively). While not statistically significant, there was an interesting trend between sponge chips versus sponge abundance that suggests that quantification of the chips in the sediment could be used as a proxy for sponge erosion of the entire community, which cannot be estimated in by laboratory experiments. However, while this methodology could provide an integrated approach to monitor sponge bioerosion, more studies are necessary due to the influence of environmental factors on the transport and deposition of these chips.  相似文献   

Functional diversity of fish and invertebrates in coral and rocky reefs of the Eastern Tropical Pacific          下载免费PDF全文

Georgina Ramírez‐Ortiz  Luis E. Calderon‐Aguilera  Hector Reyes‐Bonilla  Arturo Ayala‐Bocos  Luis Hernández  Francisco Fernández Rivera‐Melo  Andres López‐Pérez  Arturo Dominici‐Arosamena 《Marine Ecology》2017,38(4)

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).  相似文献   

Emplacement age of the Markagunt gravity slide in southwestern Utah,USA     

McKenna E. Holliday  Tiffany Rivera  Brian Jicha  Robin B. Trayler  Robert F. Biek  Michael J. Braunagel  W. Ashley Griffith  David B. Hacker  David H. Malone  Danika F. Mayback 《地学学报》2023,35(1):66-72

The Markagunt gravity slide (MGS) is a large-volume landslide in southwestern Utah that originated within the Oligocene-Miocene Marysvale volcanic field. Gravity slides are single emplacement events with long runout distances and are now recognized as a new class of volcanic hazard. Accumulation of volcanic material on a structurally weak substrate along with voluminous shallow intrusive events led to collapse. Here, ⁴⁰Ar/³⁹Ar data for landslide-generated pseudotachylyte, the landslide-capping Haycock Mountain Tuff and the deformed Osiris Tuff are combined with a Bayesian age model to determine an emplacement age of 23.05 + 0.22/−0.20 Ma for the MGS. The results suggest a lag time of <200 kyr between the caldera-forming eruption of the Osiris Tuff, additional buildup of the unstable volcanic pile and subsequent mass movement.  相似文献