GPS观测得到的中国大陆地壳垂直运动

利用中国地壳运动观测网络基准站的GPS连续观测及基本站非连续GPS观测结果，分析了基准站垂直位移的年周期变化特点，讨论了获得中国大陆垂直位移长趋势速率的条件，说明由基本站（连同基准站）多期GPS观测得到的长趋势垂直位移速率是较为可靠的。由于不少GPS观测站有幅度达数cm的年周期变化及大部分区域站观测次数少，由1999年、2001年两期区域站GPS观测难以得到可靠的长趋势垂直构造运动速率。基本站的观测结果表明中国大陆长趋势垂直构造运动主要特点是，速率较低，北升，南降，东强，西弱，西部相对东部略有下降。     

Measurement of ice flow velocities from GPS positions logged by short-period seismographs in East Antarctica

The ice flow velocity is a basic feature of glaciers and ice sheets. Measuring ice flow velocities is very important for estimating the mass balance of ice sheets in the Arctic and Antarctic. Traditional methods for measuring ice flow velocity include the use of stakes, snow pits and on-site geodetic GPS and remote sensing measurement methods. Geodetic GPS measurements have high accuracy, but geodetic GPS monitoring points only sparsely cover the Antarctic ice sheets. Moreover, the resolution and accuracy of ice flow velocities based on remote sensing measurements are low. Although the accuracy of the location data recorded by the navigation-grade GPS receivers embedded in short-period seismographs is not as good as that of geodetic GPS,the ice flow velocity can be accurately measured by these navigation-grade GPS data collected over a sufficiently long period. In this paper, navigation-grade GPS location data obtained by passive seismic observations during the 36 th Chinese National Antarctic Research Expedition were used to accurately track the movement characteristics of the ice sheet in the Larsemann Hills of East Antarctica and the Taishan Station area. The results showed that the ice sheet in the two study areas is basically moving northwestward with an average ice flow velocity of approximately 1 m mon-1. The results in the Taishan Station area are basically consistent with the geodetic GPS results, indicating that it is feasible to use the embedded GPS location data from shortperiod seismographs to track the movement characteristics of ice sheets. The ice flow characteristics in the Larsemann Hills are more complex. The measured ice flow velocities in the Larsemann Hills with a resolution of 200 m help to understand its characteristics. In summary, the ice flow velocities derived from GPS location data are of great significance for studying ice sheet dynamics and glacier mass balance and for evaluating the systematic errors caused by ice sheet movements in seismic imaging.     

基于GPS观测的地壳垂向季节性运动研究进展

介绍了基于GPS观测获取的地壳垂向季节性运动组成及相应的分析方法,阐述了地壳季节性运动在GPS流动垂向季节性修正、区域负荷质量变化监测、应力扰动与地震活动性的季节性变化分析、区域地壳结构反演等方面的应用研究进展,认为利用GPS观测研究地壳季节性运动的应用正向多手段、多学科融合发展,但需进一步完善数据处理模型(策略)、削弱解算结果中的误差,且各区域的地壳季节性运动机理值得深入分析。     

Formation of Vertical Thermal Structure in Lakes in Northwestern Russia and Finland

Vertical distribution of average annual temperature of water in lakes in the period of maximum water heating is analyzed as a function of zonal climatic factors and lake morphometry. Regression analysis is applied to hydrometeorological data on water temperature measurements at standard horizons made from 1958 to 1989 in 58 lakes in northwester Russia and eight lakes in Finland. The temperature of the top five-meter layer is found to depend mainly on the latitude. The major factors at a depth of 10 and lower are the lake morphometry and river water inflow.     

Angular velocities of Nubia and Somalia from continuous GPS data: implications on present-day relative kinematics

This study focuses on the break-up of the African tectonic plate into separate Nubian and Somalian blocks, based on recent Global Positioning System (GPS) data. A new, unique velocity field has been obtained by processing all available observations of permanent GPS stations on Africa since 1996. The quantity and distribution of the stations and the length of the time-series of observations exceed that of previous studies by a considerable margin, allowing one to derive a reliable estimate of the differential motion between the Nubia and Somalian plates, which are considered as a single (African) block in the prevailing global tectonic plate models. The estimated relative pole of rotation of Somalia with respect to Nubia is located at 54.8°S; 37.0°E with magnitude −0.069°/Ma, implying distinct opening in the Ethiopian Rift of magnitude ≈7 mm/year and azimuth ≈N94°E, whereas in southeastern South Africa this value is reduced to ≈2 mm/year in almost the same direction. This is in accordance with some of the independent geological and geophysical tectonic models of the Nubia-Somalia plate boundary region. However, the spatial density of the current tracking network is still not optimal to establish the exact location of the entire Somalia-Nubia plate boundary; in particular, the possible branch east of Lake Victoria and heading towards the Mozambique Channel is impossible to confirm or reject at this moment.     

Results of the application of tropospheric corrections from different troposphere models for precise GPS rapid static positioning

In many surveying applications, determination of accurate heights is of significant interest. The delay caused by the neutral atmosphere is one of the main factors limiting the accuracy of GPS positioning and affecting mainly the height coordinate component rather than horizontal ones. Estimation of the zenith total delay is a commonly used technique for accounting for the tropospheric delay in static positioning. However, in the rapid static positioning mode the estimation of the zenith total delay may fail, since for its reliable estimation longer observing sessions are required. In this paper, several troposphere modeling techniques were applied and tested with three processing scenarios: a single baseline solution with various height differences and a multi-baseline solution. In specific, we introduced external zenith total delays obtained from Modified Hopfield troposphere model with standard atmosphere parameters, UNB3m model, COAMPS numerical weather prediction model and zenith total delays interpolated from a reference network solution. The best results were obtained when tropospheric delays derived from the reference network were applied.     

区域网GPS观测得到的汶川大地震前后的地壳垂直运动

中国地壳运动观测网络1000个观测站的GPS非连续观测区域网分别在1999年、 2001年、 2004年、 2007年和2009年作了5次观测。 2008年5月12日汶川8.0 级地震震中(31.0°N, 103.4°E)恰好在区域网GPS观测站密集的地区。 区域网长期、 多期GPS观测可降低年周期变化影响, 有利于获取此次地震前后的垂直位移趋势变化。 简要讨论了GPS垂直位移观测的精度。 分析了垂直位移观测的主要干扰地面沉降, 特别是华北地区因大量抽取地下水产生的严重地面沉降。 为获取汶川地震前垂直运动信息, 首先剔除因大量抽取地下水产生的大幅度沉降干扰结果, 通过趋势面分析中国大陆垂直位移空间分布, 显示了3个垂直位移沉降最显著区域。 对比分析表明, 临近汶川震区的沉降区, 未见大量抽取地下水干扰影响。 汶川地震前1999—2007年区域网GPS观测站得到的垂直位移表明, 汶川地震紧临显著沉降区的西北侧, 龙门山断层北段垂直运动闭锁。 该沉降区与另两个沉降区的时空变化明显不同, 也与区域网水平应变异常区的空间分布不同, 但该沉降区与区域网水平应变异常区同时出现。 大幅度同震垂直位移集中在龙门山断层北段震前垂直位移闭锁区。 这些事实表明, 汶川地震前GPS观测到的紧临震中的沉降区及垂直运动闭锁区与汶川地震的发生存在密切关系。     

鄂尔多斯块体周缘地区现今地壳水平运动与应变

位于青藏块体和华北块体之间的鄂尔多斯块体及其周缘地区是中国大陆构造活动最活跃的地区之一,从1300年至今,在块体周边断陷盆地和西南缘断裂带上发生了五次8级以上的地震.为了了解该地区现今地壳运动、应变状态以及断裂滑动分布,我们收集了中国大陆构造环境监测网络2009-2013年、国家GPS控制网、跨断陷盆地的8个GPS剖面等共527个流动站和32个连续站GPS观测数据,获得了高空间分辨率的地壳水平运动速度场,进一步用均匀弹性模型计算了应变率分布.结果表明,块体内部GPS站点向NEE方向运动,速度变化较小,应变率大多在（-1.0~1.0）×10-8/a之间;山西断陷带构造运动与变形最为强烈,盆地相对于鄂尔多斯块体为拉张变形,应变率为（1.0~3.0）×10-8/a,相对于东部山地则为挤压变形,应变率为（-2.0~-3.0）×10-8/a,盆地西侧断裂（如罗云山断裂、交城断裂）以拉张运动为主,拉张速率为2~3 mm·a-1,盆地东侧断裂主要以右旋缩短运动为主,速率为1~3 mm·a-1;河套断陷带西部的临河凹陷处于较强的张性应变状态,应变率为（2.0~3.0）×10-8/a;块体西南边缘处于压缩应变状态,应变率为（-1.0~-2.0）×10-8/a,六盘山断裂存在明显的地壳缩短运动,速率约为2.1 mm·a-1,速率在断裂附近逐渐减小,反映了断裂处于闭锁状态;相对于鄂尔多斯块体内部渭河断裂带为左旋运动,速率为1.0 mm·a-1,盆地处在弱拉张变形状态.     

Vertical plasma drift velocities in the polarization jet observation by ground Doppler measurements and driftmeters on DMSP satellites

Vertical and horizontal plasma drifts are investigated during the polarization jet (PJ) detection in the F2 ionospheric layer based on the Doppler measurements at the Yakutsk meridian chain of subauroral ionospheric stations. It is shown that the velocities of vertical and horizontal drifts are significantly higher than the background motion during PJ observation periods. The ionospheric plasma motion direction changes from upward to downward on the polar edge of the main ionospheric trough. Doppler measurements on the DPS-4 ionosondes are compared with the simultaneous measurements of the plasma drift on the DMSP satellites during their passage near the Yakutsk meridian. The two kinds of measurements are in good agreement with each other. During the magnetic storm of June 23, 2005, by measurements of the DMSP satellites, the velocities of upward plasma flows were 1.0–1.4 km/s at a satellite altitude of 850 km. In the ionospheric F region, this speed corresponds to 150 m/s. According to satellite measurements, the westward drift velocity reached 2.5 km/s. The development of the polarization jet in the ionosphere was accompanied by a tenfold decrease in the electron density in 15–30 min.     

Vertical velocities associated with gravity waves measured in the mesosphere and lower thermosphere with the EISCAT VHF radar

The EISCAT VHF radar (69.4°N, 19.1°E) has been used to record vertical winds at mesopause heights on a total of 31 days between June 1990 and January 1993. The data reveal a motion field dominated by quasi-monochromatic gravity waves with representative apparent periods of 30–40 min, amplitudes of up to 2.5 m s^–1 and large vertical wavelength. In some instances waves appear to be ducted. Vertical profiles of the vertical-velocity variance display a variety of forms, with little indication of systematic wave growth with height. Daily mean variance profiles evaluated for consecutive days of recording show that the general shape of the variance profiles persists over several days. The mean variance evaluated over a 10 km height range has values from 1.2 m²s^–2 to 6.5 m²s^–2 and suggests a semi-annual seasonal cycle with equinoctial minima and solsticial maxima. The mean vertical wavenumber spectrum evaluated at heights up to 86 km has a slope (spectral index) of -1.36 ± 0.2, consistent with observations at lower heights but disagreeing with the predictions of a number of saturation theories advanced to explain gravity-wave spectra. The spectral slopes evaluated for individual days have a range of values, and steeper slopes are observed in summer than in winter. The spectra also appear to be generally steeper on days with lower mean vertical-velocity variance.     

Determination of recent crustal deformations based on precise GPS measurements in the Vogtland earthquake area

This paper presents methods and results of recent geodetic investigations in the Saxon part of the NW Bohemia/Vogtland earthquake area. The technique of precise GPS measurements and the intercomparison of successive observation epochs are described in detail. Horizontal surface deformations of the earth's crust were determined with an accuracy level of 1 mm over a range of some 10⁴ m. The results of five GPS campaigns carried out from 1994 to 2001 reveal significant relative displacements of up to 5 mm between successive observation epochs. Furthermore, there are clear indications that the deformation process is not linear with time but correlated with the seismic activity.     

GPS垂直分量与温度、气压的相关性分析及影响机制探讨

选取新疆9个GPS观测站数据和所在地区的气温、 气压数据, 运用相关和回归分析方法进行研究, 并探讨了温度、 气压对GPS垂直分量影响的物理机制。 研究结果表明: ① GPS垂直分量周期近似为1 a的变化为气温的影响; ② 气压对GPS垂直分量的影响基本是同步的, 主要表现为短周期的震荡; ③ GPS周年振幅随着纬度的升高而增大的原因是年温差随纬度的升高而增大。     

Present day geodynamics in Iceland monitored by a permanent network of continuous GPS stations

Iceland is located on the Mid-Atlantic Ridge and thereby offers a rare opportunity to study crustal movements at a divergent plate boundary. Iceland is not only characterized by the divergence of the Eurasian and North American Plates, as several active volcanoes are located on the island. Moderate size earthquakes occur in the transform zones, causing measurable crustal deformation. In 1999 the installation of a permanent network of continuous GPS stations (ISGPS) was initiated in order to observe deformation due to unrest in the Hengill volcanic system and at the Katla volcano. The ISGPS network has been enlarged over the years and consists today of more than 25 CGPS stations. Most of the stations are located along the plate boundary, where most of the active deformation takes place. Uplift due to post-glacial rebound due to the melting of the largest glacier in Europe, Vatnajökull, is also detected by the ISGPS network. This study presents results from analysis of 9 years of data from the ISGPS network, in the global reference frame PDR05, which has been evaluated by the Potsdam-Dresden-Reprocessing group with reprocessed GPS data only. We thus determine subsidence or land uplift in a global frame. The horizontal station velocities clearly show spreading across the plate boundary of about 20 mm/a. Stations in the vicinity of the glacier Vatnajökull indicate uplift in the range of 12 mm/a, while a station in the central part of Iceland shows uplift rates of about 25 mm/a. Tide gauge readings in Reykjavik and current subsidence rates observed with CGPS agree also quite well.     

Seismic zoning of the southern slope of Greater Caucasus from the fractal parameters of the earthquakes, stress state, and GPS velocities

By complex analysis of GPS velocities, seismicity, fractal dimensions of the spatial distribution of seismic epicenters, focal mechanisms of the earthquakes, and stress state of the Earth’s crust, four seismic zones (Balaken-Zagatala, Sheki-Gabala, Shamakhy-Ismailly, and Absheron) are revealed within the southern slope of the Greater Caucasus. The suggested method can be used as a criterion in seismotectonic zoning; it could also be useful in the assessment of seismic hazards in the collision zones.     

声波测井中的相速度与群速度讨论(英文)

声波测井过程中获取的速度到底是相速度还是群速度,目前仍存在一些争议,本文从理论分析和数值模拟的角度,使用三种模型对这一问题进行了研究。首先,构造一个相速度与群速度可调的稳态声波传播模型——不同声速的两个平面波叠加模型,利用慢度时间相关(STC)方法提取声波波速,数值模拟结果表明,无论相速度较大或是群速度较大,STC方法提取出来的波速都是相速度;其次,通过频散分析和割线积分得到刚性壁圆柱流体模型中的频散曲线与分波波形,使用STC方法得到的速度与相速度的频散曲线吻合较好,而直接读取波至获得的速度与群速度的频散曲线趋势一致;最后,利用频散分析和实轴积分方法,获得偶极子在慢地层中激发的模式及全波波形,得到的结果再次验证了刚性壁圆柱流体模型中的结论。     

华北地区大范围精密水准和GPS垂直运动分析

利用华北地区2005-2007年大面积水准观测数据和1999年以来364个GPS测站(包括流动站和连续站)观测数据,分别获取其速度场。结果表明,该地区大面积水准和GPS重叠地区的垂直运动趋势基本一致,大致以太行山构造带为界,西部地区以隆升运动为主,东部地区以下沉运动为主,个别地区大面积水准和GPS的差异性运动可能是由于观测资料的时间跨度不一致和测点分布不尽相同所致。     

Vertical dynamics of summer phytoplankton in a stratified estuary (Gulf of Finland,Baltic Sea)

We present the results of multiparametric observations designed to follow the phytoplankton dynamics and interrelated physical, chemical and biological processes in the Gulf of Finland (Baltic Sea). Data were acquired by an autonomous moored water column profiler, an acoustic Doppler current profiler, a flow-through system installed aboard a ferry and by profiling and discrete water sampling aboard research vessels in July and August 2009. The main aim of the study was to investigate the processes responsible for the formation and maintenance of sub-surface maxima of phytoplankton biomass. We suggest that the environmental conditions caused by the prevailing atmospheric and oceanographic forcing (wind; vertical stratification; basin-wide, mesoscale and sub-mesoscale processes) are preferred by certain species/taxonomic groups and explain the migration patterns of phytoplankton. Nocturnal downward migration of phytoplankton with a swimming speed up to 1.6 m h⁻¹ occurred when the community was dominated by the dinoflagellate Heterocapsa triquetra. The observed splitting of the population into two vertically separated biomass maxima suggests that the H. triquetra cells, which reached the sub-surface layers with high nutrient concentrations, experienced bi-diurnal or asynchronous (when swimming upwards) vertical migration. The most intense sub-surface biomass maxima, on some occasions with the biomass much higher than that in the surface layer, were detected in connection to the sub-mesoscale intrusions below the depth of the strongest vertical density gradient.     

Recent crustal deformation of İzmir, Western Anatolia and surrounding regions as deduced from repeated GPS measurements and strain field

To investigate contemporary neotectonic deformation in İzmir, Western Anatolia and in its neighborhood, a relatively dense Global Positioning System (GPS) monitoring network was established in 2001. Combination of three spatially dense GPS campaigns in 2001, 2003 and 2004 with temporally dense campaigns between 1992 and 2004 resulted in a combined velocity field representing active deformation rate in the region. We computed horizontal and vertical velocity fields with respect to Earth-centered, Earth-fixed ITRF2000, to Eurasia and to Anatolia as well.The rates of principal and shear strains along with rigid-body rotation rates were derived from velocity field. Results show east–west shortening between Karaburun Peninsula and northern part of İzmir Bay together with the extension of İzmir Bay in accordance with general extension regime of Western Anatolia and Eastern Agea. East–west shortening and north–south extension of Karaburun Peninsula are closely related to right-lateral faulting and a clockwise rotation. There exists a block in the middle of the peninsula with a differential motion at a rate of 3–5 ± 1 mm/year and 5–6 ± 1 mm/year to the east and south, respectively.As is in Western Anatolia, north–south extension is dominant in almost all parts of the region despite the fact that they exhibit significantly higher rates in the middle of the peninsula. Extensional rates along Tuzla Fault lying nearly perpendicular to İzmir Bay and in its west are maximum in the region with an extension rate of 300–500 ± 80–100 nanostrain/year and confirm its active state. Extensional rates in other parts of the region are at level of 50–150 nanostrain/year as expected in the other parts of Western Anatolia.