中国西部地区地壳结构特征与强震活动相关性研究          下载免费PDF全文

姜迪迪  江为为  胥颐  郝天珧  胡卫剑  余景锋 《地球物理学报》2014,57(12):4029-4040

中国西部地区是地震活动十分强烈的地区,天山、阿尔泰、帕米尔和西昆仑都是著名的地震构造带,在这些地震构造带和周边地区发生了多次震级大于5级的强震.本文通过分析西部地区的重力场特征,根据重力数据结合地震剖面、应用Parker-Oldenburg方法反演得到了研究区莫霍面深度,通过对比地震层析成像的反演结果,分析了研究区的地壳结构特征.计算结果表明,研究区地壳结构不均匀特征明显,在造山带地区一般是莫霍面坳陷区,盆地则是莫霍面隆起区,主要造山带地壳速度结构表现为高速区,盆地和主要凹陷区为低速区.根据计算结果和以往强震震中位置分析了地壳构造与强震活动的相关性,西部地区的地震活动与地壳结构的横向不均匀密切相关,强震主要发生在地壳速度变化带附近和地壳速度结构差异较大的地区,在构造应力作用下,这些地壳介质非均匀地区易发生强震,这是中国西部造山带和盆-山边界附近频发强震的构造原因之一.  相似文献   

Drivers of phytoplankton,bacterioplankton, and zooplankton carbon biomass in tropical hydroelectric reservoirs     

《Limnologica》2014

Studies of carbon sources in plankton communities are important because carbon content has become the main currency used in functional studies of aquatic ecosystems. We evaluated the contribution to the total organic carbon pool from different plankton communities (phytoplankton, bacterioplankton, and zooplankton – C-biota) and its drivers in eight tropical hydroelectric reservoirs with different trophic and hydrological status and different physical features. Our systems were separated into three groups based on trophic status and water residence time: (i) mesotrophic with low residence time (ML); (ii) mesotrophic with high residence time (MH); and (iii) eutrophic with low residence time (EL). Our hypothesis that reservoirs with low water residence times and low nutrient concentrations would show the lowest C-biota was supported. Phytoplankton carbon (C-phy) showed the highest concentrations in the EL, followed by MH and ML systems. The EL group also showed significantly higher zooplankton carbon (C-zoo). No significant difference was observed for bacteria carbon (C-bac) among the three system groups. In addition to trophic status and water residence time, regression analyses revealed that water temperature, light, pH, and dissolved organic carbon concentrations were the main drivers of plankton communities in these large tropical hydroelectric reservoirs.  相似文献   

Magnetic fabric of Plio-Pleistocene sediments from the Crotone fore-arc basin: Insights on the recent tectonic evolution of the Calabrian Arc (Italy)     

《Journal of Geodynamics》2014

Low-field anisotropy of magnetic susceptibility (AMS) analyses were performed on 532 samples collected in 36 (mostly lower Pliocene to lower Pleistocene) marine clay sites from the Crotone basin, a fore-arc basin located on top of the external Calabrian accretionary wedge. The Crotone basin formed since mid-late Miocene under a predominant extensional tectonic regime, but it was influenced thereafter by complex interactions with NW–SE left-lateral strike-faults bounding the basin, which also yielded post-1.2 Ma ∼30° counterclockwise block rotations. The basin is filled by continental to marine sediments yielding one of the thickest and best-exposed Neogene succession available worldwide. The deep-marine facies – represented by blue-grey marly clays gave the best results, as they both preserved a clear magnetic fabric, and provided accurate chronology based on previously published magnetostratigraphy and calcareous plankton (i.e. foraminifers and nannofossils) biostratigraphy. Magnetic susceptibility range and rock magnetic analyses both indicate that AMS reflects paramagnetic clay matrix crystal arrangement. The fabric is predominantly oblate to triaxial, the anisotropy degree low (<1.06), and the magnetic foliation mostly subparallel to bedding. Magnetic lineation is defined in 30 out of 36 sites (where the e12 angle is <35°). By also considering local structural analysis data, we find that magnetic fabric was generally acquired during the first tectonic phases occurring after sediment deposition, thus validating its use as temporally dependent strain proxy. Although most of the magnetic lineations trend NW–SE and are orthogonal to normal faults (as observed elsewhere in Calabria), few NE–SW compressive lineations show that the Neogene extensional regime of the Crotone basin was punctuated by compressive episodes. Finally, compressive lineations (prolate magnetic fabric) documented along the strike-slip fault bounding the basin to the south support the significance of Pleistocene strike-slip tectonics. Thus the Crotone basin shows a markedly different tectonics with respect to other internal and western basins of Calabria, as it yields a magnetic fabric still dominated by extensional tectonics but also revealing arc-normal shortening episodes and recent strike-slip fault activity. The tectonics documented in the Crotone basin is compatible with a continuous upper crustal structural reorganization occurring during the SE-migration of the Calabria terrane above the Ionian subduction system.  相似文献   

云南地区近期地壳活动特征   总被引：5，自引：0，他引：5  

洪敏  张勇  邵德盛  王伶俐  王岩 《地震研究》2014,37(3)

基于云南省的GNSS连续观测资料,通过最小二乘、克里金插值等方法进行速度场、应变参数的求解,获得了自2010年起至今云南地区的地壳活动特征。结果表明,云南地区最大剪应变变化速率存在西强东弱,北强南弱的特征,目前滇西北地区最大剪应变增强最快,滇南至滇西南等区域挤压应变积累最明显,且2011年缅甸7.2级地震的发生未改变这一地区的应变积累趋势。  相似文献   

运用H-k扫描和人工读取震相到时两种方法对比研究云南地区地壳结构   总被引：1，自引：0，他引：1  

龙飞  胡家富  杨海燕  陈俊磊 《地震研究》2014,37(4)

利用云南及其邻区59个宽频地震台站记录到的30°~100°远震资料,采用P波接收函数方法对云南地区的地壳厚度和地壳平均泊松比分布进行分析。研究结果显示:用H-k扫描和人工读取震相到时两种方法得到的云南地区地壳厚度和泊松比分布情况较为吻合。研究区域内Moho面埋深南浅北深,横向变化达30~40 km。在川滇菱形块体东南缘,地壳厚度等值线呈东南向舌状突出。泊松比呈块体分布特征,断裂两侧差异显著。高泊松比的分布主要集中在滇缅泰块体内和研究区域北部以及小江断裂附近,这与该区处于印度板块与欧亚板块碰撞俯冲前缘的特殊地理位置有关。  相似文献   

滁州地区构造活动特征分析     

赵朋  郑颖平  翟洪涛  潘纪顺  曹均峰  王立会 《华南地震》2014,(3):96-103

通过对安徽滁州地区主要断层活动特征调查、坳陷与断坳发育演化的分析,得出两类构造活动具有一致性,且第四纪以来整体表现为弱活动特点。考虑研究区西侧的郯庐断裂带和东北侧的苏北盆地两个中强构造活动区影响,认为滁州地区处于协调区域构造应力释放的活动状态,地震活动水平较低。  相似文献   

唐山7.8级地震前的震中迁移与远台前兆的关系     

郭增建  郭安宁 《华北地震科学》2014,(4):1-3

以震中迁移始发点的前兆讨论了唐山7.8级地震震中位置的预测,并以此为例分析了汶川8级地震和芦山7级地震的前兆问题。另外,从震中迁移延长线上的前兆来讨论了唐山大震的发生时间。  相似文献   

The provenance of Gansu Group in Longxi region and implications for tectonics and paleoclimate     

LIANG MeiYan  WANG ZhiXiang  ZHOU Sen  ZONG KeQing  HU ZhaoChu 《中国科学:地球科学(英文版)》2014,57(6):1221-1228

The Neogene sediments of Gansu Group from northwestern China contain eolian and fluvial deposits.The origins of these sediments are very important for exploring the onset of Asian inland aridification,the pattern of paleo-atmospheric circulation,and the regional tectonics and geomorphic evolution during the Miocene.Here we present detrital-zircon age spectra of typical eolian and fluvial deposits from highlands and subsidence basin,and compare them with those of surrounding eroded mountain(such as the West Qinling Mountains and Liupan Mountains)materials and Quaternary loess derived from the Asian inlands.The results reveal that(1)the detrital-zircon age spectrum of the Miocene eolian sample is remarkably different from the eroded materials of the West Qinling Mountains and the Miocene fluvial deposits from Tianshui region,but very similar to the Quaternary loess deposits.This indicates that the provenance of Miocene eolian sediments is similar with the Quaternary loess,and thus further confirms the previous conclusions that the distribution of Asian arid lands and the pattern of atmospheric circulation during the Miocene are broadly similar with the Quaternary.(2)The detrital-zircon age spectrum of the fluvial deposits(with age about 11.5 Ma)from Tianshui region is different from the eroded materials of West Qinling Mountains,but similar with that of the Liupan Mountains to the east,which may suggest that the Liupan Mountains have already been exhumed by11.5 Ma.  相似文献   

基于MODIS数据的新疆叶尔羌河流域山区积雪特征分析     

贾翔  陈蜀江  黄铁成  黄佛君  赵彩凤  李琪  梁艳  党洁 《冰川冻土》2014,36(2):296-303

科学监测新疆叶尔羌河流域山区积雪面积及其变化特征对该区域的气候研究、雪水资源开发利用、环境灾害预报和生态环境保护等方面有重要意义. 利用2000-2012年近13 a的MOD10A2积雪产品提取研究区域内积雪,结合DEM数据分析研究区内积雪面积的动态变化特征. 结果显示：新疆叶尔羌河流域山区的积雪面积的年际变化幅度较大,其中,2005年和2009年积雪面积较大,2007年则为典型少雪年;年内变化差异显著,总体上呈现“M”型的特点,12月和3月处于高位,2月和8月处于低谷. 叶尔羌河流域山区积雪覆盖率随着海拔的上升逐渐增大,稳定积雪主要分布在海拔5 000 m以上的地区;不同坡向的积雪覆盖率差异比较明显,西北坡、东坡、东北坡的积雪覆盖率比北坡、东南坡、西坡、南坡的积雪覆盖率高,西北坡高达52.8%,南坡仅为20%. 叶尔羌河流域山区的积雪面积与气温呈负相关,与降水量呈正相关,积雪面积变化对气温因素更为敏感.  相似文献   

不同视角下InVEST模型的土壤保持功能对比   总被引：9，自引：0，他引：9  

胡胜  曹明明  刘琪  张天琪  邱海军  刘闻  宋进喜 《地理研究》2014,33(12):2393-2406

土壤保持是生态系统的重要服务功能之一。黄土高原是世界上水土流失最严重的地区,黄河中游地区是黄河泥沙的主要来源,继续开展黄河中游地区土壤保持研究,对于当地的水土保持、土地利用结构调整、退耕还林、生态补偿以及水库管理具有重大意义。以黄河一级支流无定河的源头(营盘山库区)为研究区,采用生态系统服务和交易的综合评估模型InVEST(Integrated Valuation of Ecosystem Services and Trade-offs),从水文和土地利用两个角度出发,对研究区地块截留能力、输出能力和保持能力进行对比研究,重点探讨哪种角度的结果更科学合理,并进一步研究清淤情境下2010年营盘山库区的土壤保持能力及其空间格局特征。结果表明：① 基于子流域边界和土地利用边界的计算结果差异悬殊,水文学意义的子流域边界可以保证沉积物沿水文路径迁移过程的完整性,评价结果更科学合理;InVEST沉积物模型应该采用水文意义上的自然流域边界,而不宜将土地利用边界作为子流域单元进行评价。② 2010年营盘山库区在清淤情境下的沉积物截留总量为586482.60 t,输出总量为129868.61 t,平均输出量为12.93 t/hm²,保留总量为1559198.40 t,平均保留量为151.57 t/hm²。③ 地块的沉积物截留能力从上游至下游逐渐增强,而沉积物输出能力却刚好相反。无定河西侧支流的土壤保持能力比东侧支流偏高,两大支流平均土壤保持量低值区均出现在河流上游地区。  相似文献