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1.
Introduction Earthquake magnitude is the most common measure of an earthquake′s size,and is one of the basic parameters of an earthquake.There are three most familiar scales of earthquake magnitude:ML(local earthquake magnitude),MS(surface wave magnitude)and mB/mb(body wave magni-tude).Richter(1935)introduced ML when studying earthquakes in Southern California.In1945,Gutenberg(1945a)put forward surface wave magnitude scale to determine earthquake magnitude(MS)using surface waves(20s)of s… 相似文献
2.
Rapid afterslip and short-term viscoelastic relaxation following the 2008 M_W7.9 Wenchuan earthquake
Zhigang Shao Rongjiang Wang Yanqiang Wu Langping Zhang Institute of Earthquake Science China Earthquake Administration Beijing China GFZ German Research Center for Geosciences D- Potsdam Germany 《地震学报(英文版)》2011,(2):163-175
Significant postseismic deformation of the 2008 M W 7.9 Wenchuan earthquake has been observed from GPS data of the first 14 days after the earthquake. The possible mechanisms for the rapid postseismic deformation are assumed to be afterslip on the earthquake rupture plane and viscoelastic relaxation of coseismiclly stress change in the lower crust or upper mantle. We firstly use the constrained least squares method to find an afterslip model which can fit the GPS data best. The afterslip model can explain n... 相似文献
3.
Two distinct, conflicting, land-use planning paradigms affect drylands: one seeking environmentally sustainable outcomes and one addressing political-demographic concerns. The environmental paradigm is relatively new and is couched in the lexicon of sustainable development, combating desertification and biodiversity conservation. These concerns proscribe planning principles that allow for human settlement in drylands while minimizing its environmental impact. The latter paradigm has a longer history, born in central governments’ desire to secure sovereignty over outlying regions. These concerns result in planning goals that conflict with environmental goals. The environmental paradigm encourages compact development and efficient land-use, while the political-demographic one encourages in-migration of ‘friendly’ populations and the establishment of a physical presence on a maximum amount of land. Using Israel’s Negev Desert and China’s Xinjiang region as case studies, we suggest that successful implementation of sustainable dryland management depends on recognizing the challenge presented by political-demographic planning motivations. As such, successful implementation of environmental planning requires resolution of existing political conflicts. Since drylands are characteristically geographic and demographic frontiers, they are ideal settings in which to study the conflict between environmental and political-demographic goals and they provide an opportunity to better understand how this conflict creates a barrier to sustainable development. 相似文献
4.
Steven P. Hamburg Matthew A. Vadeboncoeur Andrew D. Richardson Amey S. Bailey 《Climatic change》2013,116(3-4):457-477
Observing the full range of climate change impacts at the local scale is difficult. Predicted rates of change are often small relative to interannual variability, and few locations have sufficiently comprehensive long-term records of environmental variables to enable researchers to observe the fine-scale patterns that may be important to understanding the influence of climate change on biological systems at the taxon, community, and ecosystem levels. We examined a 50-year meteorological and hydrological record from the Hubbard Brook Experimental Forest (HBEF) in New Hampshire, an intensively monitored Long-Term Ecological Research site. Of the examined climate metrics, trends in temperature were the most significant (ranging from 0.7 to 1.3 °C increase over 40–50 year records at 4 temperature stations), while analysis of precipitation and hydrologic data yielded mixed results. Regional records show generally similar trends over the same time period, though longer-term (70–102 year) trends are less dramatic. Taken together, the results from HBEF and the regional records indicate that the climate has warmed detectably over 50 years, with important consequences for hydrological processes. Understanding effects on ecosystems will require a diversity of metrics and concurrent ecological observations at a range of sites, as well as a recognition that ecosystems have existed in a directionally changing climate for decades, and are not necessarily in equilibrium with the current climate. 相似文献
5.
Nutrient loading to estuaries with heavily populated watersheds can have profound ecological consequences. In evaluating policy
options for managing nitrogen (N), it is helpful to understand current and historic spatial loading patterns to the system.
We modeled N inputs to Narragansett Bay from 1850 to 2000, using data on population, human waste disposal, livestock, fertilizer,
and atmospheric deposition. We found that total N loading to the bay increased 250% from 1850 to 2000, and 80% from 1900 to
2000. Loading to the upper bay increased far more than that to the lower bay, and the most important source shifted from non-point
animal waste to human waste concentrated at sewage treatment facilities. We also modeled future N loads in 2015 under four
management scenarios. Planned improvements in sewage treatment would reduce N loads 9% below business-as-usual, to the 1990
loading rate. Greater reductions, to circa 1900 rates of loading, may be possible. 相似文献
6.
Nicolas Thomas 《紫金山天文台台刊》1996,(3)
Amajor objective of the Infrared Space Observatory (ISO) is the determination of the sized and albedoes of several objects in the "Kuiper disc".The method by which this will be achieved is described.It is shown that the unknown shapes and surface thermal properties proviede additional complications to the interpretation of ISO data.The requirement for ground-based measurements of the visual light curves of these objects is demonstrated and the implications of the results of the ISO observ Vations is discussed. 相似文献
7.
Chongjiang DU Dr. Institute for Hydraulic Structures Agricultural Engineering University of Karlsruhe Kaiserstr. D- Karlsruhe Germany Franz NESTMANN Prof Dr. Institute for Hydraulic Structures Agricultural Engineering University of 《国际泥沙研究》1997,(3)
LINTRODUCTIONTerrainmodellingisatermtodescribetheprocessofrepresentingthesurfaceoftheEarth.Mathemahcally,theproblemcanbedescribedas;Givenasetofn(3sn相似文献
8.
Geochemical Characteristics of a Veinlet Kupferschiefer Profile from the Lubin Mine, Southwestern Poland 总被引:3,自引:0,他引:3
Previous studies have shown that the ascending, oxidizing brines play a very important role in Kupferschiefer mineralization. Fractures could be the pathway of the brines. In order to clarify the influences of the brines on bulk organic matter, aromatic hydrocarbons and Kupferschiefer mineralization, one veinlet Kupferschiefer profile from the Lubin mine, southwestern Poland was studied with the microscopic, geochemical and Rock-Eval methods. The microscopic results indicate that organic matter of the veinlet sample consists dominantly of bitumen. Its extract content is higher than in other samples. The dominant aromatic compounds are naphthalene and alkylated naphthalenes (Na-PAH), which have migrated into the veinlet sample from other sediments. The content of phenanthrene and its methylated derivatives (Ph-PAH) is much lower than in other samples. The reason may be due to their heavier mass than Na-PAH. It is more difficult for Ph-PAH to migrate. The Na-PAH was probably removed from the shale by dist 相似文献
9.
Mineral weathering in soils is an important source of many nutrients to forest ecosystems. Apatite, a Ca phosphate mineral, occurs in trace amounts in virtually all igneous and metamorphic rocks and is often found as small mineral inclusions in more weathering-resistant silicate minerals. To better understand the distribution of apatite in soils and its exposure to soil solutions, a sequential extraction method was developed to selectively dissolve minerals from soils so that the amount of apatite in contact with soil solutions versus that armored by silicate minerals could be quantified. The use of three molarities of HNO3 (0.01, 0.1 and 1 M) at three temperatures (0, 10, or 20 °C) was explored and it was found that apatite congruently dissolved in 1 M HNO3 at all three temperatures, but did not completely dissolve in weaker HNO3 solutions. Soil horizons, glacial till (i.e., soil parent material), and individual minerals separated from till collected from the Hubbard Brook Experimental Forest (HBEF), NH, were subjected to a 4-step sequential extraction. Chemical analyses of the extracts indicate that 1 M NH4Cl (pH 7; 20 °C) removes exchangeable ions, 1 M HNO3 at 20 °C primarily dissolves apatite in contact with solutions, 1 M HNO3 at 200 °C primarily dissolves biotite and chlorite (and apatite armored by them), and a mixture of concentrated HNO3, HCl, and HF at 200 °C dissolves the more refractory minerals including muscovite, alkali feldspar, plagioclase feldspar and quartz (and apatite armored by these minerals). This extraction method was applied to soil profiles from HBEF to demonstrate that it could be used to interpret the abundance of apatite and other minerals as a function of depth. Approximately 70% of the apatite in the HBEF soil parent material is exposed to soil solutions; the remaining 30% is armored in more weathering-resistant micas and feldspars. In the upper soil horizons, the only apatite that has not been weathered from the soil occurs as inclusions in micas and feldspars and thus the rate of dissolution of apatite in weathered soil horizons is controlled by silicate mineral dissolution. 相似文献
10.
WU Zhenhan JIANG Wan Peter Blisniuk BI Siwen ZHANG Shukun Olaf Kuchel MAO Yi Institute of Geomechanics CAGS Minzu Xueyuan Nanlu Beijing Institut fur Geowissenschaften Universitat Potsdam Postfach D- Potsdam Germany Liu Xinzhu 《《地质学报》英文版》1999,73(3):289-293
The Shuanghu basin is a NE-trending rift basin bounded by NE-striking normal faults and NW-striking shear-extensional faults of the northern Tibetan Plateau. Four samples from calcite veins in marginal faults and one sample from mudstone (S-3) were collected for dating the evolution of the Shuanghu basin by using the ESR spectrograph of EXM-type. Ages were calculated according to the close-equilibrium model on the basis of the measured ESR signal spectra of samples, providing good chronological information. It is known from the ESR dating that the extensional faulting and rifting of the Shuanghu area began at 4.92 Ma B.P., followed by regional folding in 3.56-1.36 Ma, NW-striking faulting in 0.60 Ma and normal faulting in 0.024 Ma in the Shuanghu basin. 相似文献