利用GPS和GRACE分析四川地表垂向位移变化   总被引：1，自引：0，他引：1       下载免费PDF全文

丁一航  黄丁发  师悦龄  姜中山  陈婷 《地球物理学报》2018,61(12):4777-4788

陆地水储量的季节性变化是导致地表周期性负荷形变位移的主要因素,有效地剔除地表位移中的陆地水储量影响,是获取地壳构造垂向运动的必要过程.四川地处青藏高原东边缘,地形分区明显,境内以长江水系为主,水资源丰富,研究四川地区地表负荷形变位移,有助于分析陆地水储量的时空分布特性及地壳构造形变信息.本文利用研究区域内59个CORS站的GPS观测数据,计算了CORS站点的垂向位移,并将其与GRACE所得相应结果进行对比分析.结果显示,GPS和GRACE所得垂向位移时间序列的振幅大小整体相符,但存在明显的相位差.GPS站点振幅最大值为12.7 mm,对应HANY站,最小值为1.5 mm,对应SCMX站.GRACE所得的地表垂向位移振幅大小均为3~4 mm,且最大位移集中出现在7-9月份;而GPS站点出现最大位移的月份和地形相关,东部盆地、西北部高原和南部山地分别出现在7-8月份、10-11月份和10月份.GPS站点时间序列中的周年项与陆地水的季节性变化强相关,为了讨论陆地水储量对GPS站点位移的影响,本文利用改进的总体经验模态分解方法（MEEMD：Modified Ensemble Empirical Mode Decomposition）,从GPS垂向位移时间序列中提取出周年项及约2年的年际变化项.发现利用MEEMD获取的周年项改正原始GPS时间序列时可使其WRMS（Weight Root Mean Square）减少量减小约26%,结果优于最小二乘拟合方法提取的GPS周年项改正效果,验证了MEEMD方法在GPS坐标时间序列处理中的可行性及有效性.  相似文献   

利用广义三角帽方法评估GRACE反演中国大陆地区水储量变化的不确定性   总被引：1，自引：0，他引：1       下载免费PDF全文

姚朝龙  李琼  罗志才  王长委  张瑞  周波阳 《地球物理学报》2019,62(3):883-897

在无真实观测值的情况下,本文利用广义三角帽方法评估了五种GRACE时变重力场模型（CSR、GFZ、GRGS、HUST发布的球谐系数解和JPL发布的Mascon解）反演中国大陆地区2003-2013年水储量变化的不确定性.研究结果表明,CSR、GFZ、JPL、HUST和GRGS反演月水储量变化不确定性的区域平均RMS分别为14.4 mm、26.3 mm、25.3 mm、26.6 mm和56.1 mm,其中GRGS的结果未恢复泄漏信号;在季和年尺度上,模型的不确定性均小于月尺度;扣除周期和趋势信号后,各模型反演结果更为一致.除长江流域外,CSR在13个流域的不确定性均小于其他模型,GRGS反演各流域水储量变化的不确定性通常较大,且可能高估了温带大陆性气候地区水储量的波动;CSR和JPL的不确定性受流域周边水文特征、气候类型、流域面积和形状的影响相对较小,不确定性变化范围分别为2.3~17.1 mm和5.6~22.5 mm,GFZ和HUST受影响较大,不确定性变化范围分别为5.5~35.1 mm和4.0~40.6 mm.本文的研究结果为GRACE产品不确定性评估提供了新的途径,为GRACE时变重力场模型的选取提供参考.  相似文献   

南极格罗夫山陨石的磁化率     

罗红波  林杨挺  胡森  刘焘  冯璐  缪秉魁 《岩石学报》2009,25(5):1260-1274

我国在南极格罗夫山发现并收集到大量南极陨石,需要一种无损、快速简单的分类方法。陨石磁化率(χ)的主要贡献是其中的铁镍金属,因而有可能成为一种简便有效的分类参数。同时,磁化率是陨石的一个重要物理参数。我们在国内首次开展陨石磁化率的研究,通过对模拟陨石磁化率样品的测量,证明可以通过不同取向的测量平均,将样品的大小和形状等几何因素的影响减小在仪器的测量精度范围之内。完成了首批613块南格格罗夫山陨石的磁化率测量,除普通球粒陨石外,还包括火星陨石、灶神星陨石、碳质球粒陨石、中铁陨石、橄榄陨铁、橄辉无球粒陨石等特殊类型。根据质量磁化率,可以划分大部分H、L、LL群陨石。特别重要的是,磁化率对于划分非平衡的普通球粒陨石化学群提供了更为可靠的参数。格罗夫山H群陨石的磁化率分布与南极其他地区的陨石十分相似,二者相对降落型陨石均向低质量磁化率方向平移0.2（logχ, 10^-9m³/kg）,反映了风化作用对南极陨石磁化率的平均影响程度;格罗夫山L群陨石的质量磁化率分布同样较降落型陨石偏低0.2左右,但南极其他地区的陨石与沙漠陨石的磁化率分布相似,二者均更为离散和偏低,可能反映了不同的风化程度。  相似文献   

Rheological structure of the mantle of a super-Earth: Some insights from mineral physics     

Shun-ichiro Karato 《Icarus》2011,212(1):14-229

The rheological properties of the mantle of super-Earths have important influences on their orbital and thermal evolution. Mineral physics observations are reviewed to obtain some insights into the rheological properties of deep mantles of these planets where pressure can be as high as ∼1 TPa. It is shown that, in contrast to a conventional view that the viscosity of a solid increases with pressure (at a fixed temperature), viscosity will decrease with pressure (and depth) when pressure exceeds ∼0.1 TPa. The causes for pressure-weakening include: (i) the transition in diffusion mechanisms from vacancy to interstitial mechanism (at ∼0.1 TPa), (ii) the phase transition in MgO from B1 to B2 structure (at ∼0.5 TPa), (iii) the dissociation of MgSiO₃ into MgO and SiO₂ (at ∼1 TPa), and (iv) the transition to the metallic state (at ∼1 TPa). Some (or all) of them individually or in combination reduce the effective viscosity of constituent materials in the deep interior of super-Earths. Taken together, super-Earths are likely to have low viscosity deep mantle by at least 2-3 orders of magnitude less than the maximum viscosity in the lower mantle of Earth. Because viscosity likely decreases with pressure above ∼0.1 TPa (in addition to higher temperatures for larger planets), deep mantle viscosity of super-Earths will decrease with increasing planetary mass. The inferred low viscosity of the deep mantle results in high tidal dissipation and resultant rapid orbital evolution, and affects thermal history and hence generation of the magnetic field and the style of mantle convection.  相似文献   

Planetary core size: A seismological approach     

Martin Knapmeyer 《Planetary and Space Science》2011,59(10):1062-1068

A key parameter for understanding the geodynamics of a terrestrial planet is the size of its core. Numerical evaluation of 28 different interior structure models of Mercury, Venus, Earth, the Moon, and Mars suggests that there is an almost linear relationship between the core radius and the extent of the seismic P-wave core shadow. A scaling law is derived from a simple mantle density and velocity model that permits the interpretation of respective seismic measurements on terrestrial planetary bodies.  相似文献   

Core-collapse supernovae and the Younger Dryas/terminal Rancholabrean extinctions     

G. Robert Brakenridge 《Icarus》2011,215(1):101-106

Early predictions that some supernovae release large quantities of prompt high energy photons are now corroborated by optical identification of core-collapse supernovae associated with extragalactic GRBS (beamed γ-ray bursts) and XRFS (beamed or un-beamed X-ray flashes). Given the in-galaxy supernova frequency and GRB and XRF recurrence statistics, significant Earth-incident events during the past several million years very likely occurred and nearby events should have affected the Earth and other planetary atmospheres, including terrestrial surface solar UV, the Earth’s climate, and its ecology. The Younger Dryas Stadial (∼12,900 to 11,550 calendar yr BP) began with sharply cooler temperatures in the Earth’s northern hemisphere, regional drought, paleoecological evidence compatible with increased UV, and abrupt increases in cosmogenic ¹⁴C and ¹⁰Be in ice and marine cores and tree rings. In North America, stratigraphic and faunal sequences indicate that a major pulse of mammalian extinctions (at least 23-31 genera) began very close to 12,830 calendar yr BP and was sudden: deposits one century younger are devoid of diverse extinct fauna remains. A 10 s beamed GRB within 2 kpc of the Earth delivers 100 kJ m⁻² fluence to the Earth’s atmosphere, where it causes spallation and catalytic reactions depleting 35-50% O³, and producing excess NO_x species (which favor cooling, drought, and surface fertility), ¹⁴C, and ¹⁰Be. An un-beamed, 10⁵⁰ erg hard photon impulse at ∼250 pc produces similar terrestrial atmospheric effects. A well-characterized massive star supernova, the unusually close Vela event (d = 250 ± 30 pc; total energy of 1-2 × 10⁵¹ erg; age constrained from remnant nebula shock velocities considerations at 13,000-16,000 yr and from the pulsar characteristic age at ∼11,400 yr) may have initiated the Younger Dryas climate change, and caused the extinction of the terminal Rancholabrean fauna.  相似文献   

利用重力卫星GRACE监测亚马逊流域2002-2010年的陆地水变化   总被引：2，自引：0，他引：2       下载免费PDF全文

冯伟  Jean-Michel LEMOINE  钟敏  许厚泽 《地球物理学报》2012,55(3):814-821

本文利用GRACE (Gravity Recovery and Climate Experiment) 卫星重力资料研究了亚马逊流域2002-2010年的陆地水变化,并与水文模式和降雨资料进行了比较分析.在年际尺度上,GRACE结果表明:2002-2003年和2005年,亚马逊流域发生明显的干旱现象;2007年至2009年,陆地水呈逐年增加的趋势,并在2009年6月变化值达到最大,为772±181 km³;自2009年6月至2010年12月,陆地水总量又急剧减少了1139±262 km³,这相当于全球海平面上升3.2±0.7 mm所需的水量.水文模式得到的亚马逊流域陆地水在2010年也表现出明显的减少.降雨资料与GRACE观测资料有很好的一致性.在2005年和2010年的干旱期,亚马逊流域的降雨显著减少,说明降雨是亚马逊流域陆地水变化的重要因素.此外,本文采用的尺度因子的方法有效地降低了GRACE后处理误差的影响.  相似文献   

Quaternary alluvial-fan development, climate and morphologic dating of fault scarps in Laguna Salada, Baja California, Mexico     

Ronald M. Spelz  John M. Fletcher  Lewis A. Owen  Marc W. Caffee 《Geomorphology》2008,102(3-4):578-594

Late Quaternary slip across the Cañada David detachment has produced an extensive array of Quaternary scarps cutting alluvial-fans along nearly the entire length (~ 60 km) of the range-bounding detachment. Eight regional alluvial-fan surfaces (Q₁ [youngest] to Q₈ [oldest]) are defined and mapped along the entire Sierra el Mayor range-front. Terrestrial cosmogenic nuclide ¹⁰Be concentrations from individual boulders on alluvial-fan surfaces Q₄ and Q₇ yield surface exposure ages of 15.5 ± 2.2 ka and 204 ± 11 ka, respectively. Formation of the fans is probably tectonic, but their evolution is strongly moderated by climate, with surfaces developing as the hydrological conditions have changed in response to climate change on Milankovitch timescales. Systematic mapping reveals that the fault scarp array along active range-bounding faults in Sierras Cucapa and El Mayor can be divided into individual rupture zones, based on cross-cutting relationships with alluvial-fans. Quantitative morphological ages of the Laguna Salada fault-scarps, derived from linear diffusive degradation modeling, are consistent with the age of the scarps based on cross-cutting relationships. The weighted means of the maximum mass diffusivity constant for all scarps with offsets < 4 m is 0.051 and 0.066 m²/ka for the infinite and finite-slope solutions of the diffusion equation, respectively. This estimate is approximately an order of magnitude smaller than the lowest diffusivity constants documented in other regions and it probably reflects the extreme aridity and other microclimatic conditions that characterize the eastern margin of Laguna Salada.  相似文献   

不同陆地生态系统碳通量对GEOS-Chem模型模拟全球CO₂浓度的影响     

张珊  田向军  陈权亮  韩锐  张洪芹  张璐 《气候与环境研究》2019,24(5):552-566

大气中CO₂含量的增加速率已经超过了自然界所能吸收的速度,并逐步影响到全球气候变暖。利用模型模拟分析已经成为一个重要的工具用以深入对碳循环的理解。本文使用2008～2010年的生物模型SiB3（Simple Biosphere version 3）与优化后的CT2016（Carbon Tracker 2016）陆地生态系统碳通量驱动GEOS-Chem大气化学传输模型模拟全球CO₂浓度。通过分析模拟CO₂浓度的空间分布与季节变化,加深对全球碳源汇分布特点的理解,探究陆地生态系统碳通量不确定性对模拟结果的影响,进而认识陆地生态系统碳通量反演精度提升的重要性。SiB3与优化后的CT2016陆地生态系统碳通量都具有明显的季节变化,但在欧洲地区碳源汇的表现相反,其全球总量与空间分布也存在极大的不确定性。模拟CO₂浓度结果表明:在人为活动较少地区,陆地生态系统碳通量对近地面CO₂浓度空间分布起主导作用,尤其在南半球和欧洲地区模拟浓度有明显差异,且两种模拟结果的季节差异依赖于陆地生态系统碳通量的季节变化。将模拟结果与9个观测站点资料进行对比,以期选用合适的陆地生态系统碳通量来提升GEOS-Chem模拟CO₂浓度的精度。实验结果表明:两种模拟结果均能较好的模拟CO₂浓度的季节变化及其峰谷值,但CT2016模拟的CO₂浓度在多数站点处更接近观测资料,模拟准确性更高。  相似文献   

The potential of historic rock avalanches and man-made structures as chlorine-36 production rate calibration sites     

《Quaternary Geochronology》2013

Samples from three medieval rock avalanches from the French (Le Claps, Mont Granier) and Austrian Alps (Dobratsch) and a man-made structure, i.e. the Stephansdom in Vienna, have been analysed for in-situ produced ³⁶Cl by accelerator mass spectrometry (AMS). All four sampling sites of independently known exposure duration turned out to be not appropriate as calibration sites for the determination of the ³⁶Cl-production rate from Ca. Indeed, the determination of short exposure ages for dating rock avalanches and man-made structures by ³⁶Cl is hindered dramatically by inheritance, especially for samples characterized by high ^natCl-concentrations. Generally, there are hints that the theoretical calculation of ³⁶Cl-production from epithermal and thermal neutron-capture on ³⁵Cl is highly underestimated in all existing models, thus, asking for particular precaution if working on high-Cl samples for any project. Hence, this work evidences that potential high inheritance, even for samples reasonably shielded before exhumation, has to be considered especially when dealing with recently exposed surfaces such as glacially polished rocks, alluvial terraces, fault scarps etc.  相似文献