The December 26, 2004, off the west coast of northern Sumatra, Indonesia, M _W=9.0, earthquake and the critical-point-like model of earthquake preparation     

Jiang Chang-sheng  Wu Zhong-liang 《地震学报(英文版)》2005,18(3):290-296

Long-term seismic activity prior to the December 26, 2004, off the west coast of northern Sumatra, Indonesia, M _W=9.0 earthquake was investigated using the Harvard CMT catalogue. It is observed that before this great earthquake, there exists an accelerating moment release (AMR) process with the temporal scale of a quarter century and the spatial scale of 1 500 km. Within this spatial range, the M _W=9.0 event falls into the piece-wise power-law-like frequency-magnitude distribution. Therefore, in the perspective of the critical-point-like model of earthquake preparation, the failure to forecast/predict the approaching and/or the size of this earthquake is not due to the physically intrinsic unpredictability of earthquakes. Foundation item: Ministry of Science and Technology Project (2004CB418406). Contribution No. 05FE3010, Institute of Geophysics, China Earthquake Administration.  相似文献   

北京城近郊区土壤中Cd的释放、形态转化与演变趋势     

李志萍  黄怀曾  冯流  迟宝明  黄毅 《地质通报》2005,(Z1)

在对北京城近郊区主要类型土壤(潮土和褐土)中Cd形态分析的基础上,研究pH与土壤中Cd的释放量及其形态转化的关系。结果表明:潮土和褐土中Cd的释放量曲线都呈下凹的弧形,在pH=6～7之间释放量最低。pH对土壤中Cd释放的影响,其本质是土壤中Cd的化学形态发生了变化,各形态间的转化以水溶态为中介体。所有的形态转化中,pH对交换态和碳酸盐结合态影响最大,且这两者之间的转化对生物有效量起决定性作用。进而根据北京城近郊区土壤中生物有效Cd的分布状况,结合北京市近12年监测的大气pH值,对北京城近郊区土壤Cd污染进行预警。  相似文献   

地质灾害预报预警方法探讨——以岫岩县气象预报预警为例     

周宏清  李仁锋关丽 高静 《地质找矿论丛》2005,20(8):152-155

岫岩县存在着以崩塌、滑坡、泥石流为主的多种地质灾害。文章野外地质灾害调查和收集的各种资料，建立Acess数据库，并运用MAPGIS软件平台投影转换、空间分析等功能，对岫岩县地质灾害易发程度进行分区。结合地质灾害发生与气象因素的相互关系，提出了各易发区的群发性地质灾害临界降雨量，初步建立了地质灾害气象预报预警和信息的发布程序。  相似文献   

不同还田方式下稻草的腐解速率及养分释放规律     

李逢雨涂仕华  王昌全冯文强孙锡发  秦鱼生 《山地学报》2006,24(B10):92-97

采用尼龙网袋法和砂滤管法研究了稻草不同还田方式下的腐解及养分释放规律。结果表明：稻草还田后，前期腐解快，后期较慢。翻埋还田的稻草腐解速率明显快于覆盖还田稻草，整个试验期间（210d）翻埋还田的稻草腐解率达到76．55％，而覆盖还田的稻草仅为53．50％。稻草覆盖与翻埋两种还田方式下养分释放速率均以钾（K）最快，磷（P）次之，氮（N）最慢。还田10d内，两种方式下K分别释放了50．32％和90．13％。稻草与土壤充分混合条件下，稻草和土壤矿化释放的氮以NO3-N为主（〉80％），NH4-N和可溶性有机氮较少；在稻草还田后的前40d存在土壤微生物与作物竞争土壤矿质氮的现象，40d之后此现象消失，稻草开始氮的净矿化；在稻草埋入土壤时同时配施适量的氮肥，则不会出现微生物的夺氮现象。整个试验期间，该土壤氮净矿化量达90．4mg／kg土。  相似文献   

H+和有机酸对可变电荷土壤铝释放的动力学研究   总被引：4，自引：0，他引：4  

王代长  蒋新  贺纪正  邓建才  卞永荣 《地球化学》2006,35(6):651-659

利用流动搅动法研究了在模拟酸雨和低分子量有机酸条件下可变电荷土壤铝释放的动力学特征,结果表明,在pH3.5的模拟酸雨作用下,红壤和黄壤中流出液铝的浓度范围约为15～40μmol/L,铝的释放快反应来源于土壤交换性铝和有机络合态铝,铝的释放慢反应对应于含铝矿物的溶解。赤红壤和砖红壤上在0～300min内流出液铝的浓度范围约为1～5μmol/L,流出液pH值大于4.5,对H 的缓冲作用表现为阳离子交换、SO24-的专性吸附释放OH-和矿物表面的质子化;当流出液pH值小于4.5时,H 开始溶解土壤中的含铝固相,铝释放的最后浓度为20～30μmol/L。用相近pH值的有机酸溶出土壤铝的浓度比pH3.5的模拟酸雨要高,特别是在砖红壤上,开始就有大量铝的释放,其浓度为20～75μmol/L,红壤上是70～150μmol/L,随时间延长,流出液中的铝浓度分别为10～20μmol/L和20～30μmol/L。有机酸作用下铝的释放机制主要是有机酸被土壤吸附后,有机酸与位于表面晶格中的铝原子形成络合体,促进了铝的溶解;其次是有机酸的吸附掩盖了土壤表面的质子化过程,增强了酸的溶解,以及有机配体对铝的络合作用,增加了铝的释放量。不同有机酸对铝的溶出能力也有不同,其释放铝能力的大小为:柠檬酸>酒石酸>苹果酸,这取决于有机配体与铝的络合能力。  相似文献   

Damage to structures by pyroclastic flows and surges, inferred from nuclear weapons effects     

Greg A. Valentine 《Journal of Volcanology and Geothermal Research》1998,87(1-4)

In order to define the risk from explosive eruptions, one must constrain both the probability of explosive events and the effects, or consequences, of those events. This paper focuses on the effects of pyroclastic flows and surges (here termed ‘pyroclastic density currents', or PDCs) on buildings, infrastructure elements, and to some extent on vehicles. PDCs impart a lateral force to such structures in the form of dynamic pressure, which depends on the bulk density of the PDC (which in turn depends mainly on particle concentration) and its velocity. For reasonable ranges of particle concentration (10⁻³ to 0.5) and velocities (10 to 300 m/s), dynamic pressure on the upstream face of a structure ranges from 0.1 kPa to 10⁴ kPa. Lateral loads ranging up to about 100 kPa were produced during nuclear weapons tests in the 1940s and 1950s that were designed to study the effects of such loading on a variety of structures for civil defense and emergency response purposes in the event of nuclear war. Although considerable simplifications are involved, the data from these weapon tests provide useful analog information for understanding the effects of PDCs. I reviewed data from the nuclear tests, describing the expected damage from different loadings. Tables are provided that define the response of different structural elements (e.g., windows, framing, walls) and whole structures to loading in probabilistic terms, which in principle account for variations in construction quality, orientation, and other factors. Finally, damage documented from historical eruptions at Mt. Lamington (1951), Herculaneum (AD 79 Vesuvius eruption), and St. Pierre (1902 Mt. Pelee eruption) is reviewed. Damage patterns, combined with estimates of velocity, provide an independent estimate of particle concentration in the PDCs. Details of structural damage should be recorded and mapped around future eruptions in order to help refine this aspect of consequence analysis. Another fruitful approach would be to combine numerical simulations of eruption scenarios, which can produce simulated maps of dynamic pressure, with GIS-based data on structures for a given region; the result would be predictions of consequences that could be used for planning and emergency response training.  相似文献   

The basal ash deposit of the Sovana Eruption (Vulsini Volcanoes, central Italy): the product of a dilute pyroclastic density current     

D. M. Palladino  J. Taddeucci 《Journal of Volcanology and Geothermal Research》1998,87(1-4)

A low aspect ratio, decimeter-thick ash deposit, axisymmetrically distributed around the Latera Caldera (Western Vulsini Volcanoes, central Italy) has been studied by means of field and laboratory investigations. Field studies comprise facies analysis at centimeter scale and maximum clast size and deposit thickness measurements. Grain size and component distribution, chemical composition and particle morphoscopic features have been determined on selected samples. We discuss the co-ignimbrite ash fall vs. pyroclastic surge origin of the deposit and the hydrovolcanic vs. magmatic eruption nature. Complex facies association, textural features and grain size data rule out an ash fall origin for the whole deposit. The hydrovolcanic nature of the eruption has been discarded on the grounds of componentry and morphoscopic features of vitric fragments. We propose that the main body of the ash deposit formed from a radially expanding, dilute, turbulent pyroclastic density current, originated by a continuous collapse of a low-altitude (a few kilometers) eruptive column with a possible radial jet component.  相似文献   

Application of mechanical and statistical models to the study of seismicity of synthetic earthquakes and the prediction of natural ones     

Yao-Lin Shi  Jie Liu  David Vere-Jones  Jian-Cang Zhuang  Li Ma 《地震学报(英文版)》1998,11(4):421-430

Based on a cellular automata model, which obeys rules produced by a spring-damper-slider model of fault network, a synthetic earthquake catalog of deterministic chaos can be produced. It is a challenge to inverse the model parameters and predict the synthetic earthquakes from the synthetic catalog. We apply an improved statistical model of coupled stress release to the synthetic catalog, it does successfully inverse the stress evolution of the system, but effectively prediction of the earthquakes from the stresses remains a problem. This research is partially supported by the Chinese Joint Seismological Science Foundation and Asian 2000 Foundation of New Zealand.  相似文献   

Estimates of global N2O emissions from cattle, pig and chicken manure, including a discussion of CH4 emissions     

M. G. M. Berges  P. J. Crutzen 《Journal of Atmospheric Chemistry》1996,24(3):241-269

Humans seem to have doubled the global rate of terrestrial nitrogen fixation. Globally 50–70% (85 Tg, 1 Tg=10¹² g) of the nitrogen supplied in fertilizer (80 Tg N/a) and leguminous crops (40–80 Tg N/a) are used to feed cattle. The aim of the present study was to derive some estimates of global N₂O production from animal manure. As the parameter giving the most stable numerical basis for regional and global extrapolation we adopted the molar emission ratios of N₂O to NH₃. These ratios were measured in cattle, pig and chicken housings with different manure handling systems, in dung-heaps and in liquid manure storage tanks. Individual molar emission ratios from outside manure piles varied over two orders of magnitude, strongly dependent on the treatment of the manure. A median emission ratio of 1.6×10^-2 (n=65) was obtained in cow-sheds with slatted floors and liquid manure stored underneath and a median ratio of 24×10^-2 (n=31) was measured in a beef cattle housing with a solid manure handling system.We next extrapolated to global NH₃ emissions from those estimated for Europe, using N uptake by the animals as a scaling factor. Multiplication with observed N₂O to NH₃ ratios next provided some estimates of regional and global N₂O emissions. To account for the great variability of the emission ratios of N₂O/NH₃, we developed upper and lower case emission scenarios, based on lower and upper quartiles of measured emission ratios. The global emission from cattle and swine manure is in the range of 0.2–2.5 Tg N-N₂O/a, representing 44+-39% of the annual atmospheric accumulation rate. This N₂O emission arises from about 40 Tg N/a of cattle and pig manure stored in or at animal housings. We did not account for N₂O emissions from another 50 Tg N/a excreted by grazing cattle, goats and sheep, and application of the manure to agricultural fields. Our study makes it clear that major anthropogenic N₂O emissions may well arise from animal manure. The large uncertainty of emission ratios, which we encountered, show that much more intense research efforts are necessary to determine the factors that influence N₂O emissions from domestic animal manure both in order to derive a more reliable global estimate of N₂O release and to propose alternative waste treatment methods causing smaller N₂O releases. In our studies we found large enhancements in N₂O releases when straw was added to the manure, which is a rather common practice. In view of the ongoing discussion in Europe to re-install the traditional solid manure system (bed down cattle) for environmental and animal welfare reasons, it is noteworthy that our measurements indicate highest N₂O release from this particulary system.In a similar manner, but based on a smaller data set, we also estimated the release of CH₄ from cattle and swine manure and from liquid manure only to be about 9 Tg/year in good agreement with the estimate by the Environmental Protection Agency (1994) of 8.6+-2.6 Tg/year. A total annual methane release as high as 34 Tg/a was derived for solid and liquid cattle and pig manure from animals in housings.  相似文献   

Evidence for periodic seismicity in the inner Aegean seismic zone     

G. A. Papadopoulos  Ph. Voidomatis 《Pure and Applied Geophysics》1987,125(4):613-628

The most complete and reliable data of strong (M _s6.5), shallow (h<70 km) earthquakes which occurred in the inner Aegean seismic zone have been utilized to describe its seismicity time variation during 1800–1986 by two independent statistical models. The first is a sequentially stationary model of seismicity rates which shows that intervals of low seismicity rate, lasting for some 37 years, alternate with high rate intervals of 8–12 years duration. The second model is a statistical model according which seismic energy released within 5-year time windows approximates a harmonic curve within a period of about 50 years. This model is in agreement with the notion that the time series of strong earthquake occurrences in the inner Aegean seismic zone consists of a random (shocks withM _s=6.5–6.8) and a nonrandom component (M _s6.9). Maxima and minima of the harmonic curve coincide with the high and low rate intervals, respectively. A model of regional stationary accumulation of thermal stresses along certain seismic belts and their cyclic relaxation may explain this periodicity.  相似文献