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541.
John B. Rundle Paul B. Rundle Andrea Donnellan P. Li W. Klein Gleb Morein D.L. Turcotte Lisa Grant 《Tectonophysics》2006,413(1-2):109
Observations indicate that earthquake faults occur in topologically complex, multi-scale networks driven by plate tectonic forces. We present realistic numerical simulations, involving data-mining, pattern recognition, theoretical analyses and ensemble forecasting techniques, to understand how the observable space–time earthquake patterns are related to the fundamentally inaccessible and unobservable dynamics. Numerical simulations can also help us to understand how the different scales involved in earthquake physics interact and influence the resulting dynamics. Our simulations indicate that elastic interactions (stress transfer) combined with the nonlinearity in the frictional failure threshold law lead to the self-organization of the statistical dynamics, producing 1) statistical distributions for magnitudes and frequencies of earthquakes that have characteristics similar to those possessed by the Gutenberg–Richter magnitude–frequency distributions observed in nature; and 2) clear examples of stress transfer among fault activity described by stress shadows, in which an earthquake on one group of faults reduces the Coulomb failure stress on other faults, thereby delaying activity on those faults. In this paper, we describe the current state of modeling and simulation efforts for Virtual California, a model for all the major active strike slip faults in California. Noting that the Working Group on California Earthquake Probabilities (WGCEP) uses statistical distributions to produce earthquake forecast probabilities, we demonstrate that Virtual California provides a powerful tool for testing the applicability and reliability of the WGCEP statistical methods. Furthermore, we show how the simulations can be used to develop statistical earthquake forecasting techniques that are complementary to the methods used by the WGCEP, but improve upon those methods in a number of important ways. In doing so, we distinguish between the “official” forecasts of the WGCEP, and the “research-quality” forecasts that we discuss here. Finally, we provide a brief discussion of future problems and issues related to the development of ensemble earthquake hazard estimation and forecasting techniques. 相似文献
542.
543.
Susanna F. Jenkins Christina R. MagillK. John McAneney 《Journal of Volcanology and Geothermal Research》2007
Volcanic events comprising multiple eruptive stages are common in the historical and geological record and display activity of variable intensity ranging, in some cases, through to several centuries. To better understand the characteristics of such events globally, this study explores a database of historical events having Volcanic Explosivity Indices 4 or greater. The database was compiled for the most part from published and unpublished material provided by the Smithsonian Institution. The database was examined to find common statistical relationships, within and between the variables characterising multi-stage explosive events. 相似文献
544.
A brief review of ophiolites in China 总被引:7,自引:0,他引:7
Qi Zhang Christina Yan Wang Dunyi Liu Ping Jian Qing Qian Guoqing Zhou Paul T. Robinson 《Journal of Asian Earth Sciences》2008,32(5-6):308-324
Ophiolites are widely distributed in western, southwestern and northern China, where they fall into four principal age groups; Neoproterozoic, Early Paleozoic, Late Paleozoic and Mesozoic–Cenozoic. Neoproterozoic ophiolites are known only in the North Qinling orogenic belt, in NE Jiangxi Province and in western Sichuan Province. Phanerozoic ophiolites are grouped into the Paleo-Asian, Tethyan and Circum-Pacific series. The Paleo-Asian ophiolites crop out in the western and northern parts of China between the Siberian and North China Blocks, and range in age from early to late Paleozoic. All of these ophiolites are of the Franciscan (formerly Cordilleran) type and many are superimposed on one another, suggesting repeated accretion of arc assemblages in an environment similar to the present-day western Pacific Ocean. Mediterranean-type (formerly Tethyan-type) ophiolites are confined to SW China, particularly Tibet and Yunnan Province. Paleo-Tethyan ophiolites are characterized by MORB-type lavas and are typically bounded by old continental lithosphere, suggesting that they formed in small, intercontinental ocean basins. Neo-Tethyan ophiolites contain a range of lava types including MORB, IAT and boninite, indicating formation in a variety of suprasubduction zone (SSZ) environments. Circum-Pacific ophiolites occur sporadically in Taiwan and NE China, where they form tectonic mélanges composed mainly of metaperidotite, gabbro and basalt. 相似文献
545.
M. Klein 《地球表面变化过程与地形》1981,6(2):173-178
The study deals with the relationship between specific conductance and water flow in a small catchment. Three flow types were studied: (a) channel flow; (b) overland flow; (c) subsurface flow. The study of the three flow types demonstrates the important role of the flushing effect in small basins. The flushing effect is seen as an increase in water conductivity in the early stage of an event. Flushing is probably a function of accumulation in the basin. Accumulation is best defined as a function of time elapsing since the last heavy rain. The study has been carried out in the School of Geography at Leeds University, Leeds LS2 9JT, England. 相似文献
546.
Anna Bohman Erik Glaas Johannes Klein Mia Landauer Tina-Simone Neset Björn-Ola Linnér Sirkku Juhola 《Climatic change》2018,149(2):121-129
This essay discusses the concept of usefulness of research for climate change adaptation. Based on prior research and stakeholder interactions with policymakers and practitioners in the Nordic countries, we contend that critical issues related to the usefulness of adaptation research seem less associated with content (i.e. research outputs), but rather centre around the efforts made to design and communicate research, that is, to put research at the service of society and make the case for adaptation on the political agenda. This, we argue, to some extent mirrors the situation and political context in the Nordic countries, where adaptation in many locations still is an issue in its infancy, not firmly established on the political agendas, and where working procedures are not yet institutionally settled. In this context, science is considered and sometimes used as a discursive tool to make the case for adaptation. Based on the calls for research that inspires, raises hope and helps to raise the issue of adaptation on the political agendas, we elaborate the role of honest issue advocates for researchers in the field of adaptation science. 相似文献
547.
Martin Schmidt Doris Klein Christopher Conrad Stefan Dech Heiko Paeth 《Theoretical and Applied Climatology》2014,115(1-2):341-353
Vegetation cover is a crucial component of the Earth’s climate system but, still, our understanding of the mechanisms governing the reciprocal influence between atmosphere and vegetation is limited. In this study, we investigate the unilateral atmospheric impact on vegetation cover in tropical and northern Africa, differentiated into regions with different circulation regimes and into detailed land-cover classes. In contrast to former studies, climate predictors from a regional climate model are used as input for a multiple regression model. Climate models provide consistent data without gaps at high spatial resolution, a considerably larger set of available climate variables and the perspective to transfer the statistical relationships to future projections, e.g., in the context of anthropogenic climate change. Indeed, robust climate predictors which drive up to 70 % of observed interannual vegetation variability could be extracted from the climate model. Besides precipitation and temperature, global radiation, and relative humidity play an important role. The statistical transfer functions are plausible in terms of the affected regions and land-cover classes and draw a rather complex picture of the atmosphere–vegetation relation in Africa. 相似文献
548.
Atmospheric teleconnection mechanisms of extratropical North Atlantic SST influence on Sahel rainfall 总被引:1,自引:0,他引:1
Yuwei Liu John C. H. Chiang Chia Chou Christina M. Patricola 《Climate Dynamics》2014,43(9-10):2797-2811
Extratropical North Atlantic cooling has been tied to droughts over the Sahel in both paleoclimate observations and modeling studies. This study, which uses an atmospheric general circulation model (GCM) coupled to a slab ocean model that simulates this connection, explores the hypothesis that the extratropical North Atlantic cooling causes the Sahel droughts via an atmospheric teleconnection mediated by tropospheric cooling. The drying is also produced in a regional climate model simulation of the Sahel when reductions in air temperature (and associated geopotential height and humidity changes) from the GCM simulation are imposed as the lateral boundary conditions. This latter simulation explicitly demonstrates the central role of tropospheric cooling in mediating the atmospheric teleconnection from extratropical North Atlantic cooling. Diagnostic analyses are applied to the GCM simulation to infer teleconnection mechanisms. An analysis of top of atmosphere radiative flux changes diagnosed with a radiative kernel technique shows that extratropical North Atlantic cooling is augmented by a positive low cloud feedback and advected downstream, cooling Europe and North Africa. The cooling over North Africa is further amplified by a reduced greenhouse effect from decreased atmospheric specific humidity. A moisture budget analysis shows that the direct moisture effect and monsoon weakening, both tied to the ambient cooling and resulting circulation changes, and feedbacks by vertical circulation and evaporation augment the rainfall reduction. Cooling over the Tropical North Atlantic in response to the prescribed extratropical cooling also augments the Sahel drying. Taken together, they suggest a thermodynamic pathway for the teleconnection. The teleconnection may also be applicable to understanding the North Atlantic influence on Sahel rainfall over the twentieth century. 相似文献
549.
550.
Geoffrey M. Morrison Sonia Yeh Anthony R. Eggert Christopher Yang James H. Nelson Jeffery B. Greenblatt Raphael Isaac Mark Z. Jacobson Josiah Johnston Daniel M. Kammen Ana Mileva Jack Moore David Roland-Holst Max Wei John P. Weyant James H. Williams Ray Williams Christina B. Zapata 《Climatic change》2015,131(4):545-557