西藏班公湖-怒江缝合带中段侏罗纪高镁安山质岩石对中特提斯洋演化的制约   总被引：2，自引：1，他引：1  

唐跃  翟庆国  胡培远  肖序常  王海涛  王伟  朱志才  吴昊 《岩石学报》2019,35(10):3097-3114

班公湖-怒江缝合带中段地区南北向分布了三条分支蛇绿岩亚带,它们记录了该地区中特提斯洋复杂的构造演化过程。目前对于该地区洋盆俯冲消减动力学过程一直缺乏有效制约。为探讨这一问题,本文对班公湖-怒江缝合带中段新近厘定的安山岩和闪长岩开展了系统的野外、岩石地球化学和锆石U-Pb年代学研究。安山岩主要呈不整合覆盖于晚三叠世沉积地层之上,或与侏罗纪俯冲增生杂岩和橄榄岩以断层接触,闪长岩主要呈岩脉体侵入于橄榄岩中。锆石U-Pb定年表明,安山岩和闪长岩均形成于中晚侏罗世(165～161Ma)。安山岩和闪长岩地球化学组成类似,它们大都具有高的MgO含量和Mg#值,这与高镁安山岩相类似。稀土和微量元素组成显示出典型的岛弧岩浆岩特征,富集轻稀土(LREE)和Rb、Th、U、Pb等元素,亏损Ba和高场强元素(HFSE; Nb,Ta和Ti)。同时,样品还显示出较低的Ba/Th和较高的(La/Sm)N比值,以及负的锆石εHf(t)值和古老的锆石Hf模式年龄。这些特征表明这些高镁安山岩和闪长岩是大洋板片俯冲沉积物部分熔融的熔体交代地幔楔的产物。结合区域地质和前人研究,认为这些岩石可能形成于靠近海沟的大陆边缘环境,是班公湖-怒江中特提斯洋中段北拉-拉弄分支洋盆初始俯冲消减的产物,该初始俯冲作用可能与安多微陆块和南羌塘地块碰撞导致的俯冲南向跃迁有关。  相似文献   

Research on Initial Modeling Method for TTI Anisotropic Parameters Based on Local Tomography     

Kai Guo 《地球科学进展》2019,34(10):1060-1068

The initial modeling method based on TTI anisotropy can provide an initial model for the fine modeling of tomographic inversion, and the quality of the initial model directly affects the efficiency and accuracy of tomographic inversion. It is necessary to study the accurate initial modeling method of TTI anisotropy. Based on the conventional flow of the initial modeling method of TTI anisotropic, in this paper the anisotropic parameter extraction formula was perfected, a local tomography method to optimize the flow of the initial modeling method of TTI anisotropy was introduced, and the accuracy of the initial model was further improved, which is more consistent with the actual geological conditions and conducive to the fine modeling of the later tomographic inversion. The processing results of model and filed data show that the initial modeling method of TTI anisotropy based on local tomography is effective and practical.  相似文献   

Shenandoah Watershed Study-Virginia Trout Stream Sensitivity Study (SWAS-VTSSS): Stream water quality and hydrologic monitoring data for mid-Appalachian headwater streams     

Ami L. Riscassi  Todd M. Scanlon  Suzanne W. Maben  James N. Galloway 《水文研究》2021,35(4):e14164

The Shenandoah Watershed Study (established in 1979) and the Virginia Trout Stream Sensitivity Study (established in 1987) serve to increase understanding of hydrological and biogeochemical changes in western Virginia mountain streams that occur in response to acidic deposition and other ecosystem stressors. The SWAS-VTSSS program has evolved over its 40+ year history to consist of a temporally robust and spatially stratified monitoring framework. Currently stream water is sampled for water quality bi-hourly during high-flow events at three sites and weekly at four sites within Shenandoah National Park (SHEN), and quarterly at 72 sites and on an approximately decadal frequency at ~450 sites within the wider western Virginia Appalachian region. Stream water is evaluated for pH, acid neutralizing capacity (ANC), base cations (calcium, magnesium, sodium and potassium ion), acid anions (sulphate, nitrate and chloride), silica, ammonium, and conductivity with a subset of samples evaluated for monomeric aluminium and dissolved organic carbon. Hourly stream discharge (four sites) and in-situ measurements of conductivity, water and air temperature (three sites) are also measured within SHEN. Here we provide an overview and timeline of the SWAS-VTSSS stream water monitoring program, summarize the field and laboratory methods, describe the water chemistry and hydrologic data sets, and document major watershed disturbances that have occurred during the program history. Website links and instructions are provided to access the stream chemistry and time-series monitoring data in open-access federal databases. The purpose of this publication is to promote awareness of these unique, long-term data sets for wider use in catchment studies. The water chemistry and hydrologic data can be used to investigate a wide range of biogeochemical research questions and provide key inputs for models of these headwater stream ecosystems. SWAS-VTSSS is an ongoing program and quality assured data sets are uploaded to the databases annually.  相似文献   

A Time Monte Carlo method for addressing uncertainty in land-use change models     

Ahmed Mustafa  Ismaïl Saadi  Mario Cools  Jacques Teller 《International journal of geographical information science》2018,32(11):2317-2333

One of the main objectives of land-use change models is to explore future land-use patterns. Therefore, the issue of addressing uncertainty in land-use forecasting has received an increasing attention in recent years. Many current models consider uncertainty by including a randomness component in their structure. In this paper, we present a novel approach for tuning uncertainty over time, which we refer to as the Time Monte Carlo (TMC) method. The TMC uses a specific range of randomness to allocate new land uses. This range is associated with the transition probabilities from one land use to another. The range of randomness is increased over time so that the degree of uncertainty increases over time. We compare the TMC to the randomness components used in previous models, through a coupled logistic regression-cellular automata model applied for Wallonia (Belgium) as a case study. Our analysis reveals that the TMC produces results comparable with existing methods over the short-term validation period (2000–2010). Furthermore, the TMC can tune uncertainty on longer-term time horizons, which is an essential feature of our method to account for greater uncertainty in the distant future.  相似文献   

太湖水体理化指标在夏季短时间尺度上的分层及其控制因素   总被引：5，自引：4，他引：1  

赵林林  朱梦圆  冯龙庆  刘笑菡  朱广伟  陈元芳  秦伯强 《湖泊科学》2011,23(4):649-656

通过连续9d(2010年7月24日至2010年8月1日)对太湖水体理化指标垂向分层的高频率观测,揭示太湖多指标垂向分层规律.观测表明:(1)太湖中各水质指标频繁出现分层现象,但不稳定;(2)分层的主要控制因素包含气温的日变化、蓝藻水华堆积与风浪扰动等;(3)气温和太阳辐射日变化影响水温分层,水温垂向变幅可达3.94℃,...  相似文献   

上海淀山湖水生高等植物现状及其近30年变化   总被引：2，自引：0，他引：2  

施文  刘利华  达良俊 《湖泊科学》2011,23(3):417-423

于2009年8月至2010年5月调查淀山湖水生高等植物现状.并结合历史资料分析其近30年变化,探讨水生植被的发展趋势及退化原因.淀山湖现有水生高等植物29种,隶属18科,25属,栽培种、外来种比例较过去升高.30年来水生植被(尤其是沉水植被)面积严重萎缩,主要植被类型从沉水植物占优势转变为漂浮植物占优势,沉水植被主要优...  相似文献   

一次梅雨锋暴雨过程的模拟诊断分析   总被引：1，自引：3，他引：1  

贺哲  沈桐立 《南京气象学院学报》2004,27(4):487-494

利用中尺度数值模式MM5对1998年7月28—29日发生于长江中下游的梅雨锋暴雨过程进行了模拟和诊断分析。结果表明，低层温湿扰动对于强对流的发展及暴雨的出现具有重要作用。低空急流核和切变线配合的存在有利于大暴雨的产生。湿位涡场结构在暴雨增幅期与暴雨增幅前期和暴雨减弱期有明显不同。  相似文献   

成灌高铁运行对成都地磁台观测数据干扰测试     

钟李彬  林建  李雪浩  胡俊明  李国超  颜晓晔 《地震地磁观测与研究》2017,38(5):81-85

成都地磁台距成灌高铁运行线路垂直距离约1.5 km,使用数字化磁通门磁力仪GM4,在轨道沿线不同距离处进行野外测试。测试结果表明,轨道交通的运行对周围地磁观测环境产生干扰,干扰距离约6 km,干扰主要来自轨道泄露电流及输电线路产生的磁场。  相似文献   

河北省及邻区数字电扰动干扰分析   总被引：1，自引：1，他引：0  

乔子云  罗娜  贾立峰  寇海川  牛淑瑜  茅远哲 《地震地磁观测与研究》2017,38(4):158-164

通过对河北省及邻区数字电扰动观测资料进行分析和环境调查,发现主要干扰因素为供电或漏电干扰。如:昌黎地震台地电阻率整点测量受到供电干扰,三河地震台受到恒远自动化仪表厂工作时段供电干扰,高碑店地震台受到商场大型设备供电干扰,广平地震台受到UPS交流电源漏电干扰,昌平地震台受到地铁运行漏电干扰等。电扰动干扰形态相似,均为超过本底值几倍、数十倍乃至上百倍的高值脉冲变化。  相似文献   

新疆天山地区的波速比异常分析     

张琳琳  高朝军 《中国地震研究》2017,31(1):39-50

Based on the seismic observation report data provided by the Xinjiang Digital Seismic Network from 2009 to 2014,we calculate the wave velocity ratio and its background value for medium and small earthquakes by using the multi-station method in Tianshan,Xinjiang.This paper analyzes the variation of the wave velocity ratio disturbance value to highlight the abnormal,and also back-traces 7 moderate earthquakes at the research area.The results show that:(1)the background value of the wave velocity ratio is almost 1.70,the wave velocity ratio obviously decreases in the middle-eastern part of Tianshan and the region near the Puchang fault;(2)the wave velocity ratio disturbance value is mostly low in the epicenter before four earthquakes of M≥5.0 from 2011 to 2013 in the study area;(3)before 7 moderate strong earthquakes,the earthquake events with low value of the wave velocity ratio account for over 60% of corresponding total events near the epicenters,and the low value of the wave velocity ratio is relatively obvious before moderate earthquakes.  相似文献