2000年下半年全球地震活动     

范洪顺 《国际地震动态》2001,(9):14-17

2000年下半年全球共发生Mw≥6．5地震27次，其中23次为浅源地震，深源地震4次。发生Mw≥7．0地震5次，最大震级达Mw8．0。11月16日和17日，在俾斯麦群岛和所罗门群岛交界地区，发生了3次Mw≥7．8地震。2000年，全球地震活动处于1976年以来的较高水平。  相似文献   

新丰江余震震群的“应力窗口”效应与华南地区的地震活动     

蒋维强 《华南地震》1991,11(4):35-38

本文取1962至1990年12月广东省新丰江地震的余震序列资料，从应变释放的角度定量地分析新丰江的余震活动特点以及与华南地区中强地震活动的关系，并与理论分析结果对比。发现新丰江地震的余震应变释放过程具有4次明显的应变异常增加，而且，从新丰江地震以来，华南地区发生的所有5.0以上中强地震都与新丰江余震应变释放的明显异常增加相“联系”，新丰江余震震群的出现是华南地区构造应力场增强的背景下余震区应力加强的效应，可以起到监视华南地区5.0级以上中强地震的“应力窗口”作用。从1986年以来，新丰江地区的余震活动有所加强，其应变释放明显增加，表明华南地区的构造应力场在加强，其地震活动可能达到较高的水平。  相似文献   

Transformation of phosphorus species in settling seston and during early sediment diagenesis   总被引：9，自引：0，他引：9  

M. Hupfer  R. Gächter  R. Giovanoli 《Aquatic Sciences - Research Across Boundaries》1995,57(4):305-324

Sequential P extraction was combined with electron microscop and X-ray spectroscopy to characterise various P species and to study their transformation in settling seston and in recent sediment. During early diagenesis most of the particulate P formed in the water was redissolved. No net transformation into species that would resist dissolution was observed.It was shown that

•	the phosphorus (P) content and the P flux of settling particles varied seasonally over one order of magnitude
•	particles became enriched with reductant soluble P (BD-P) while settling through the hypolimnion
•	changes in BD-P were highly significantly correlated with changes in reductant soluble iron (BD-Fe)
•	bacteria oxidising Fe and Mn seemed to be mainly responsible for this increase in P concentration
•	other fractions including organic P did not change during sedimentation
•	most of the organic P and of the Fe bound P and 70% of TP was released from the sediment during early diagenesis
•	the sediment surface did not act as a trap for P migrating upwards from deeper sediment layers
•	CaCO3 sedimentation contributed little to P sedimentation but significantly to the permanent burial of P.

  相似文献   

人为热释放:全球分布的估算及其气候效应的探索   总被引：1，自引：0，他引：1  

陈兵  陈良富  董理  石广玉 《大气科学》2016,40(2):289-295

人类生产和生活中大量消费各种形式的能源,除了向大气里排放温室气体和气溶胶外,还释放大量热量。人为热释放伴随着人类社会发展而长期存在,随着全球人口增长和经济发展,其影响效应不断加剧。人为热释放具有典型地域集中、不均匀分布的特征:虽然全球平均人为热释放通量仅约为0.03 W m-2,在人口密集的城市地区,人为热释放可高达每平方米数百瓦,足以影响局地气候。伴随全球经济的发展,人口的增长及城市化进程的加剧,人为热释放分布更集中,影响气候的范围逐步扩大,其对气候的影响能力逐步增强。全球气候模式的结果表明:人为热释放能够对全球大气环流产生影响,进而影响到全球气候变化。人为热释放可以导致全球地表温度增温约0.06 K,500 hPa温度场平均升温约0.04 K,尤其对北半球中高纬度升温效应明显。研究结果表明,人为热释放虽然没有温室气体如二氧化碳等影响因子对全球气候的影响那么显著,但是其仍然能够对全球气候产生影响,是全球气候变化不可忽视的影响因子。  相似文献   

Environmental inequality and pollution advantage among immigrants in the United States     

《Applied geography (Sevenoaks, England)》2017

Environmental inequality scholarship has paid little attention to the disproportional exposure of immigrants in the United States (U.S.) to unfavorable environmental conditions. This study investigates whether new international migrants in the U.S. are exposed to environmental hazards and how this pattern varies among immigrant subpopulations (e.g., Hispanics, Asian, European). We combine sociodemographic information from the American Community Survey with toxicity-weighted chemical concentrations (Toxics Release Inventory) to model the relationship between toxin exposure and the relative population of recent immigrants across Public Use Microdata Areas (PUMAs, n = 2054) during 2005–2011. Results from spatial panel models show that immigrants tend to be less exposed to toxins, suggesting resilience instead of vulnerability. This pattern was pronounced among immigrants from Europe and Latin America (excluding Mexico). However, our results revealed that Mexican immigrants are disproportionately exposed to environmental hazards in wealthy regions.  相似文献   

胶州湾近岸沉积物-海水汞的释放研究   总被引：2，自引：0，他引：2  

单长青  刘汝海  单红仙 《海洋湖沼通报》2006,(4):44-51

本文通过模拟实验研究了胶州湾海泊河口和李村河口沉积物中的汞在不同环境条件下向海水的释放,并对汞的释放动力学数据进行了拟合。总体上两种沉积物汞的释放浓度分别为1.41~5.99μg/L和1.06~3.62μg/L,最大释放率分别为2.7%和3.4%,对胶州湾潮间带水质产生较大的影响。海水的pH值、温度和沉积物厚度都会影响汞的释放。pH<7时,汞的释放作用随pH值的升高而降低,pH>7时,汞的释放作用随pH值的升高而增大;海水温度越高,汞的释放作用越强;随沉积物厚度的增加,汞的释放量增加,释放率降低,海泊河口和李村河口沉积物的有效厚度分别为3.5cm和2.5cm。汞的释放动力学拟合结果表明多个方程都能较好的描述汞的释放动力学过程,其中以Ho的二级动力学方程拟合结果最好。  相似文献   

Study on the Release of Grouper Epinephelus for Stock Enhancement     

薄治礼  周婉霞 《海洋通报(英文版)》2003,5(1):88-96

Two methods,tagging and ink injection,are used in the grouper releasing experiment.The studied fishes are the juvenile of Epinephelus akaara and Epinephelus awoara both artificially cultivated and caught from natural waters,and their wild adults.Experimental results show that the inhabiting behaviours for both juvenile and adult fishes show distinct regionality,which move within an area of 2n mile diameter 651 days and 48 days after being released,respectively,With the tagging method,the tagged fishes could only be recaptured in the year of release while,with the injection method,they could be caught in the lst,2nd and 3rd years,It is confirmed that in the cement tank,the tagged fishes lose their 1/3 tags.That means that the tagging method is not fit for the release research while the injection method is .Generally,the recaptured rates of injected fishes are 1.4-4.5%,3.1-13.4%and 2.7%for the lst,1nd and 3rd years,respectively.  相似文献   

Evaluating fine sediment mobilization and storage in a gravel‐bed river using controlled reservoir releases     

E. L. Petticrew  A. Krein  D. E. Walling 《水文研究》2007,21(2):198-210

Two controlled flow events were generated by releasing water from a reservoir into the Olewiger Bach, located near Trier, Germany. This controlled release of near bank‐full flows allowed an investigation of the fine sediment (<63 µm) mobilized from channel storage. Both a winter (November) and a summer (June) release event were generated, each having very different antecedent flow conditions. The characteristics of the release hydrographs and the associated sediment transport indicated a reverse hysteresis with more mass, but smaller grain sizes, moving on the falling limb. Fine sediment stored to a depth of 10 cm in the gravels decreased following the release events, indicating the dynamic nature and importance of channel‐stored sediments as source materials during high flow events. Sediment traps, filled with clean natural gravel, were buried in riffles before the release of the reservoir water and the total mass of fine sediment collected by the traps was measured following the events. Twice the mass of fine sediment was retained by the gravel traps compared with the natural gravels, which may be due to their altered porosity. Although the amount of fine sediment collected by the traps was not significantly related to measures of gravel structure, it was found to be significantly correlated to measures of local flow velocity and Froude number. A portion of the traps were fitted with lids to restrict surface exchange of water and sediment. These collected the highest amounts of event‐mobilized sediments, indicating that inter‐gravel lateral flows, not just surface infiltration of sediments, are important in replenishing and redistributing the channel‐stored fines. These findings regarding the magnitude and direction of fine sediment movement in gravel beds are significant in both a geomorphic and a biological context. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Parameter estimation for multiple post-wildfire hydrologic models     

Brian A. Ebel  John A. Moody 《水文研究》2020,34(21):4049-4066

Predictions of post-wildfire flooding and debris flows are needed, typically with short lead times. Measurements of soil-hydraulic properties necessary for model parameterization are, however, seldom available. This study quantified soil-hydraulic properties, soil-water retention, and selected soil physical properties within the perimeter of the 2017 Thomas Fire in California. The Thomas Fire burn scar produced catastrophic debris flows in January 2018, highlighting the need for improved prediction capability. Soil-hydraulic properties were also indirectly estimated using relations tied to soil-water retention. These measurements and estimates are examined in the context of parameterizing post-wildfire hydrologic models. Tension infiltrometer measurements showed significant decreases (p < .05) in field-saturated hydraulic conductivity (K_fs) and sorptivity (S) in burned areas relative to unburned areas. Wildfire effects on soil water-retention were dominated by significant decreases in saturated soil-water content (θ_S). The van Genuchten parameters α, N, and residual water content did not show significant wildfire effects. The impacts of the wildfire on hydraulic and physical soil properties were greatest in the top 1 cm, emphasizing that measurements of post-fire soil properties should focus on the near-surface. Reductions in K_fs, θ_s, and soil-water retention in burned soils were attributed to fire-induced decreases in soil structure evidenced by increases in dry bulk density. Sorptivity reductions in burned soils were attributed to increases in soil-water repellency. Rapid post-fire assessments of flash flood and debris flow hazards using physically-based hydrologic models are facilitated by similarities between K_fs, S, and the Green–Ampt wetting front potential (ψ_f) with measurements at other southern CA burned sites. We suggest that ratios of burned to unburned K_fs (0.37), S (0.36), and ψ_f (0.66) could be used to scale unburned values for model parameterization. Alternatively, typical burned values (K_fs = 20 mm hr⁻¹; S = 6 mm hr^−0.5; ψ_f = 1.6 mm) could be used for model parameterization.  相似文献   

巷旁切顶对采场下位岩层垮落特征的影响机制     

刘斌慧  杨军  田锋  付强 《岩土力学》2023,44(1):289-302

巷旁切顶打断了巷道与采场下位顶板的连续性,促进了采场顶板垮落形成碎石帮,深入研究切顶对采场下位岩层垮落特征的影响机制具有重要意义。对采场支架载荷进行了分析,并对上覆岩层建立了力学建模,明确了上覆岩层运动与典型位置采场支架载荷特征的关系。在此基础上,针对6个巷旁切顶的工作面,给出了典型位置支架的载荷数据,从而分析得到巷旁切顶对采场下位岩层垮落特征的影响机制。同时,建立了数值模型,分析了不同的切顶起始位置和下位顶板强度对下位岩层垮落特征的影响。结果表明,121工法的“垮落线”具有对称的弧形边界,110工法的“垮落线”在切顶侧向工作面充分移动,N00工法介于上述两者之间。此外,不同切顶起始位置和顶板强度条件下,切顶的作用效果存在差异。研究结果有利于进一步深化巷旁切顶对采场下位岩层垮落特征影响的认识。  相似文献