Calculation of Moho Depth by Gravity Anomalies in Qinghai–Tibet Plateau Based on an Improved Iteration of Parker–Oldenburg Inversion     

Chong Zhang  Danian Huang  Guochao Wu  Guoqing Ma  Yuan Yuan  Ping Yu 《Pure and Applied Geophysics》2015,172(10):2657-2668

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Topography-Dependent Eikonal Traveltime Tomography for Upper Crustal Structure Beneath an Irregular Surface   总被引：2，自引：0，他引：2  

Ting Ma  Zhongjie Zhang 《Pure and Applied Geophysics》2015,172(6):1511-1529

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临震天体引潮力和地面长波辐射OLR异常     

任静  康春丽  马未宇  杨天青  林向洋 《中国地震》2015,31(2):447-455

利用天体引潮力周期变化模型和地面长波辐射(OLR)数据资料,分析2010~2011年云南、西藏地区的4次M5.0以上地震震前OLR异常,探讨了诱发地震的外部因素,即天体引潮力周期与红外异常发展的关联特征。结果显示:以临近发震时刻所在周期引潮力值最低点日期为OLR参照背景,获取的地震前后NOAA长波辐射OLR日增量分布图像显示:震中附近热异常明显,异常受构造控制,且其分布与断裂关系密切;异常演化经历起始-加强-高峰-衰减-再增强-发震-平静的过程,符合岩石因应力增加而破裂的规律。一方面表明地应力的临界状态演化过程可通过OLR辐射变化来反映。另一方面表明引潮力可以改变构造内部地应力的状态。  相似文献   

Semiannual and annual oscillations of sea level and their impact on asymmetry between El Niño and La Niña episodes     

Małgorzata Świerczyńska  Tomasz Niedzielski  Wiesław Kosek 《Studia Geophysica et Geodaetica》2014,58(2):302-325

The purpose of this paper is twofold. First, we demonstrate that the asymmetry between El Niño and La Niña events recorded in sea level variation occurs only during extreme episodes of El Niño/Southern Oscillation. Second, we explain that the asymmetry is controlled by certain regular cycles which have time-variable amplitudes. Gridded maps of sea level anomaly that form a spatial-temporal time series (spatial resolution: 1° × 1°, sampling interval: 1 week) spanning the time interval from 14/10/1993 to 18/04/2012 were used. We examined those time series and found that certain regular harmonic signals (periods: 365, 182, 120, 90 and 62 days) are dominant terms of their temporal variability. By subtracting those oscillations from sea level anomaly data, residuals were determined. Using skewness and kurtosis as measures of asymmetry and nonlinearity — after adopting 10-year moving window — we found that the extreme El Niño 1997/1998 has been a dominant driving force of the asymmetry and nonlinearity of El Niño/Southern Oscillation since the end of 1993. In order to detect residual signals that are responsible for the asymmetry, we applied the Fourier Transform Band Pass Filter and found that there are two important oscillations remaining in the residual sea level anomaly data, i.e. the annual and semiannual ones with time-varying amplitudes. We hypothesize that temporarily uneven amplitudes have meaningful impact on the aforementioned asymmetry.  相似文献   

突发性灾害事件信息搜集整理与服务——以汶川地震为例     

马小玲 《国际地震动态》2014,(8):31-34

以汶川地震信息服务为例,从突发性灾害事件不同时期和阶段信息产出的特点、范围以及提供多元化信息综合服务,探索了突发性灾害事件中信息的搜集整理及服务模式。从多角度阐述了突发性灾害事件发生时如何快速捕捉相关信息资料、科学分类整理以及迅速组织起应对性的信息管理与服务,达到为政府和公众赢得减灾实效的目的。  相似文献   

Spatiotemporal characteristics of precipitation and extreme events on the Loess Plateau of China between 1957 and 2009   总被引：1，自引：0，他引：1       下载免费PDF全文

L. Wan  X. P. Zhang  Q. Ma  J. J. Zhang  T. Y. Ma  Y. P. Sun 《水文研究》2014,28(18):4971-4983

Spatiotemporal trends in precipitation may influence vegetation restoration, and extreme precipitation events profoundly affect soil erosion processes on the Loess Plateau. Daily data collected at 89 meteorological stations in the area between 1957 and 2009 were used to analyze the spatiotemporal trends of precipitation on the Loess Plateau and the return periods of different types of precipitation events classified in the study. Nonparametric methods were employed for temporal analysis, and the Kriging interpolation method was employed for spatial analysis. The results indicate a small decrease in precipitation over the Loess Plateau in last 53 years (although a Mann–Kendall test did not show this decrease to be significant), a southward shift in precipitation isohyets, a slightly delayed rainy season, and prolonged return periods, especially for rainstorm and heavy rainstorm events. Regional responses to global climate change have varied greatly. A slightly increasing trend in precipitation in annual and sub‐annual series, with no obvious shift of isohyets, and an evident decreasing trend in extreme precipitation events were detected in the northwest. In the southeast, correspondingly, a more seriously decreasing trend occurred, with clear shifts of isohyets and a slightly decreasing trend in extreme precipitation events. The result suggests that a negative trend in annual precipitation may have led to decreased soil erosion but an increase in sediment yield during several extreme events. These changes in the precipitation over the Loess Plateau should be noted, and countermeasures should be taken to reduce their adverse impacts on the sustainable development of the region. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

2013 年芦山7.0 级地震前后重力场变化特征     

郑兵  易天阳  杨洋  苏琴  蒲晓霞  马伶俐  李菲菲 《中国地震》2014,30(4):543-550

利用四川地区2010 ～ 2013 年流动重力观测数据作出的重力场动态变化图像和重力段差时序变化图像,对芦山7. 0 级地震前后的重力场动态演化特征进行了研究,结果表明:震前重力场经历了约3 年的重力增大和约1 年的减小变化,重力变化呈“上升→加速上升→减速上升→加速下降→减速下降”特征; 芦山地震发生在重力场变化由下降转为上升的回调过程中;震后重力场变化以较快的速度恢复到接近震前状况,并出现重力正值变化异常区域;临震前震中区域重力场变化数值较小,构造带活动速度变慢。  相似文献   

基于COSMIC掩星数据分析全球NmF2周年和半年变化特征     

马新欣  焦立果  刘晓灿 《地震地磁观测与研究》2014,35(5):97-100

使用COSMIC掩星提供的NmF2数据,利用傅里叶分析方法,研究全球F2层峰值电子密度的周年和半年分布特征,分析2010年LT12：00 14：00 NmF2周年和半年变化幅度及2008-2011年年平均值变化.结果显示,电离层NmF2周年和半年变化幅度在中高纬地区相对较大;在赤道和低纬地区相对较小,且NmF2以半年变化为主.太阳活动增强期间,NmF2年平均值增大.  相似文献   

Upper crustal structure under Jingtai–Hezuo profile in Northeastern Tibet from topography-dependent eikonal traveltime tomography          下载免费PDF全文

Ting Ma  Zhongjie Zhang  Peng Wang  Yingkang Li 《地震科学（英文版）》2014,27(2):137-148

The Northeastern Tibetan plateau records Caledonian Qilian orogeny and Cenozoic reactivation by continental collision between the Indian and Asian plates. In order to provide the constraint on the Qilian orogenic mechanism and the expansion of the plateau, wide-angle seismic data was acquired along a 430 km-long profile between Jingtai and Hezuo. There is strong height variation along the profile, which is dealt by topography flattening scheme in our crustal velocity structure reconstruction. We herein present the upper crustal P-wave velocity structure model resulting from the interpretation of first arrival dataset from topography-dependent eikonal traveltime tomography. With topography flattening scheme to process real topography along the profile, the evenness of ray coverage times of the image area (upper crust) is improved, which provides upper crustal velocity model comparable to the classic traveltime tomography (with model expansion scheme to process irregular surface). The upper crustal velocity model shows zoning character which matches with the tectonic division of the Qaidam-Kunlun-West Qinling belt, the Central and Northern Qilian, and the Alax blocks along the profile. The resultant upper crustal P-wave velocity model is expected to provide important base for linkage between the mapped surface geology and deep structure or geodynamics in Northeastern Tibet.  相似文献   

拟建哈—佳铁路工程地震安评抗断参数研究——以依兰-伊通断裂为例   总被引：1，自引：1，他引：0  

余中元  韦庆海  王丽梅  马艳丽  张立忱  欧阳兆国 《震灾防御技术》2014,9(1):53-63

在对依兰-伊通断裂通河段晚第四纪活动参数获取的基础上,对该断裂的几何学特征和晚第四纪活动特征及有关拟建铁路地震安全的设防参数进行了探讨.研究结果表明,依兰-伊通断裂通河段总体走向N30-40°E,由3条断层组成,中支最新活动时代为全新世.该断裂未来发生7级地震时的水平位移量可能达2.2m左右,垂直位错量约为1.1m左右.该断裂全新世以来的活动性质表现为右旋走滑为主,兼具逆冲活动.根据探槽结果和野外地震地质调查得出断裂垂直位错约（1.0±0.2）m,右旋位错量约为（2.7±0.1）m,（1730-30）aB.P.以来的垂直滑动速率和水平滑动速率分别约为（0.57±0.11）mrn/a和（1.57±0.06）mm/a.未来100年内若遭遇地震,其最大水平位错量约2.87m,垂直位错值为1.04m.断层影响带宽度约为8m.该研究结果为拟建哈—佳铁路工程可能遭受的断层影响和抗震设防提供了一定的数据基础,也为地震安评中线状工程的抗断评价问题提供了一定的参考.  相似文献