深部地壳镁铁质岩石波速的研究

镁铁质、超镁铁质岩石波速实验测量在高压700-800MPa、高温800-1100℃下进行．波速-温度曲线的斜率以温度系数dVp／dT表示，大体在700℃以内，8个标本的温度系数平均为-1．86×10-4km·S^-1／℃，比资料值小得多，即在此温度范围内，波速随温度的降幅不大．在这一温度限以上，大多岩石开始脱水出溶，相组合发生变化，同时波速大幅度下降．曲线发生转折的机制是岩石中液相的产生．角闪岩波速曲线斜率也从700℃开始发生改变，950℃后速度直线下降，到1008℃时，岩石中液量达30％，波速Vp值下降到487km／s．最后，依岩类不同以及岩石出溶和相变对波速的影响划分出5个速度-温度区，讨论了华北断块内构造隆起区和沉降区下地壳可能存在的岩石及其状态．     

APPLICATION OF UAVLS TO RAPID GEOLOGICAL SURVEYS

Three-dimensional scanning with LiDAR has been widely used in geological surveys. The LiDAR with high accuracy is promoting geoscience quantification. And it will be much more convenient, efficient and useful when combining it with the Unmanned Aerial Vehicle (UAV). This study focuses on UAV-based Laser Scanning (UAVLS)geological field mapping, taking two examples to present advantages of the UAVLS in contrast with other mapping methods. For its usage in active fault mapping, we scanned the Nanpo village site on the Zhangxian segment of the West Qinling north-edge fault. It effectively removed the effects of buildings and vegetation, and uncovered the fault trace. We measured vertical offset of 1.3m on the terrace T₁ at the Zhang river. Moreover, we also scanned landslide features at the geological hazard observatory of Lanzhou University in the loess area. The scanning data can help understand how micro-topography affects activation of loess landslides. The UAVLS is time saving in the field, only spending about half an hour to scan each site. The amount of average points per meter is about 600, which can offer topography data with resolution of centimeter. The results of this study show that the UAVLS is expected to become a common, efficient and economic mapping tool.     

体应变地震波最大振幅与地震震级和震中距的统计关系探讨

Based on the body strain record of Tiantanghe station from 2008 to 2014,we make a statistical analysis of the relationship between the maximum amplitude of the body strain record and the surface-wave magnitude,epicenter distance of the earthquakes,which occurred in the Chinese mainland and its surrounding areas with MS≥6. 0 and the rest of the world with MS≥7. 0. According to statistical results,we propose a statistical formula between the surface-wave magnitude of earthquake and the maximum amplitude of the body strain record,the epicenter distance: M_S~*= 0. 37 ln A_max+ 0. 57 ln D + 0. 07. We can also derive a theoretical estimation formula for the maximum amplitude: A_max=e~(2. 7(M_S~*-0. 07))D~(-1. 54). This demonstrates that the maximum amplitude of the body strain record increases exponentially with the increase of the surface-wave magnitude, and decreases with the increase of the epicenter distance,and shows a negative correlation with their product. We further discuss the necessity of adding instruments with high frequency sampling to earthquake monitoring, and dicuss the prospects for precise earthquake prediction in future.     

基于高分辨率影像的九寨沟7.0级地震道路震害评估

2017年8月8日九寨沟7.0级地震引发贯通重灾区的S301省道、Z120县道多处损坏,给应急救援和灾后重建带来较大困难。利用高分辨率无人机和卫星影像可以对道路震害情况进行评估。本文首先对道路震害进行破坏类型和破坏等级的划分,针对不同分辨率影像所表现的道路破坏特征,建立各破坏等级、各损坏类型的解译标志,并完成灾区遥感图像覆盖范围内主要道路震害的研判与评估。经统计分析,研究区域共出现110处明显破坏,其中,68处为部分损坏,42处为完全损毁,道路整体破坏严重。     

山东地磁台网受宁东高压直流输电干扰预处理质量分析

为进一步提高山东地磁台网受高压直流输电干扰的预处理质量,通过中国地震前兆数据处理系统中相对差值检测和预处理检测功能,对山东地磁台网多年来受宁东高压直流输电干扰预处理情况进行了总结分析。结果表明,经过数据预处理,宁东高压直流输电干扰基本被去除,但仍然存在高压直流输电干扰误判、起止时间错判、干扰幅度计量不精确等问题。针对上述问题,对数据进行复核和校对,应用"缓变台阶"功能重新处理,并加强对H、D分量干扰特征的研究。     

Paleoproterozoic juvenile magmatism within the northeastern sector of the São Francisco paleocontinent: Insights from the shoshonitic high Ba–Sr Montezuma granitoids

New,integrated petrographic,mineral chemistry,whole rock geochemical,zircon and titanite UPb geochronology,and zircon Hf isotopic data from the Montezuma granitoids,as well as new geochemical results for its host rocks represented by the Corrego Tingui Complex,provides new insights into the late-to post-collisional evolution of the northeastern Sao Francisco paleocontinent.U-Pb zircon dates from the Montezuma granitoids spread along the Concordia between ca.2.2 Ga to 1.8 Ga and comprise distinct groups.Group I have crystallization ages between ca.2.15 Ga and 2.05 Ga and are interpreted as inherited grains.Group II zircon dates vary from 2.04 Ga to1.9 Ga and corresponds to the crystallization of the Montezuma granitoids,which were constrained at ca.2.03 Ga by the titanite U-Pb age.Inverse age zoning is common within the ca.1.8 Ga Group III zircon ages,being related to fluid isotopic re-setting during the Espinhaco rifiting event.Zircon ε_(Hf)(t) analysis show dominantly positive values for both Group I(-4 to+9) and Ⅱ(-3 to+8) zircons and T_(DM2) model ages of 2.7-2.1 Ga and 2.5-1.95 Ga,respectively.Geochemically,the Montezuma granitoids are weakly peraluminous to metaluminous magnesian granitoids,enriched in LILES and LREE,with high to moderate Mg#and depleted in some of the HFSE.Their lithochemical signature,added to the juvenile signature of both inherited and crystallized zircons,allowed its classification as a shoshonitic high Ba-Sr granitoid related to a late-to post-collisional lithosphere delamination followed by asthenospheric upwelling.In this scenario,the partial melting of the lithospheric mantle interacted with the roots of an accreted juvenile intra-oceanic arc,being these hybrid magma interpreted as the source of the Montezuma granitoids.The Corrego Tingui Complex host rocks are akin to a syn-to late-collisional volcanic arc granitoids originated from the partial melting of ancient crustal rocks.The results presented in this study have revealed the occurrence of juvenile rocks,probably related to an island arc environment,that are exotic in relation to the Paleo-to Neoarchean crust from the Sao Francisco paleocontinent's core.     

Solute provenance,transport and denudation in a high arctic glacierized catchment

Recent understanding of chemical weathering in glacierized catchments has been focused on mid-latitude, Alpine catchments; comparable studies from the high latitudes are currently lacking. This paper attempts to address this deficiency by examining solute provenance, transport and denudation in a glacierized catchment at 78°N in the Svalbard High Arctic archipelago. Representative samples of snow, glacier ice, winter proglacial icing and glacier meltwater were obtained from the catchment during spring and summer 1993 and analysed for major ion chemistry. Seasonal variations in the composition of glacier meltwater occur and are influenced by proglacial solute acquisition from the icing at the very start of the melt season, and subsequently by a period of discharge of concentrated snowmelt caused by snowpack elution; weathering within the ice-marginal channels that drain the glacier, particularly carbonation reactions, continues to furnish solute to meltwater when suspended sediment concentrations increase later in the melt season. Partitioning the solute flux into its various components (sea-salt, crustal, aerosol and atmospheric sources) shows that c. 25% of the total flux is sea salt derived, consistent with the maritime location of the glacier, and c. 71% is crustally derived. Estimated chemical denudation, 160 meq m⁻² a⁻¹ sea salt-corrected cation equivalent weathering rate, is somewhat low compared with other studied glacierized catchments (estimates in the range 450–1000 meq m⁻² a⁻¹), which is probably attributable to the relatively short melt season and low specific runoff in the High Arctic. A positive relationship was identified between discharge and CO₂ drawdown owing to carbonation reactions in turbid meltwater. © 1997 John Wiley & Sons, Ltd.     

高精度温度计在水温观测中的仪器稳定性分析

利用宁波地震台水温10年来的单测项、6年来的同层比测资料,对高精度温度计的仪器短期和长期稳定性进行分析对比。研究发现仪器长期存在漂移现象,漂移量的大小与每套仪器的系统特性有关,但随着观测时间的延续,漂移量逐渐减少,认为该现象对地震前兆观测影响不大;短期稳定性存在不明原因的阶跃和脉冲现象,但次数不多,幅度不大,如果不是并行观测,较难判别。因此,在资料分析时要考虑仪器的这些问题。有时仪器短期非常稳定,数天至20天整点值为同一测值。     

锦州沈家台水氡高值波动异常识别

讨论了锦州沈家台水氡活度浓度出现的高幅度波动异常变化与地震活动的关系。 沈家台水氡测项自2004年开始观测以来, 数据变化稳定, 氡活度浓度一般在4~5 Bq/L范围波动, 且具有很好的年周期变化规律。 但在2016年11月20日开始出现高幅度异常变化, 较正常波动范围平均高出约5 Bq/L。 针对此次出现的异常变化, 在排除外界干扰的基础上, 应用临界慢化方法进行高频异常识别分析。 结果表明, 提取的水氡高频信息成分和方差均存在异常变化, 且高频异常与原始数据异常出现时间具有同步性变化特征。 综合测点映震效能、 区域地震活动性、 井水地球化学分析及水氡异常形成机理等分析结果, 认为这次沈家台水氡出现的异常变化与辽西及环渤海地区应力场调整关系密切, 该区应力增强及井水文地质条件的制约是造成水氡出现高值波动的主要原因。