Vertical Crustal Motion along the Mediterranean and Black Sea Coast Derived from Ocean Altimetry and Tide Gauge Data

Tide gauge (TG) data along the northern Mediterranean and Black Sea coasts are compared to the sea-surface height (SSH) anomaly obtained from ocean altimetry (TOPEX/Poseidon and ERS-1/2) for a period of nine years (1993–2001). The TG measures the SSH relative to the ground whereas the altimetry does so with respect to the geocentric reference frame; therefore their difference would be in principle a vertical ground motion of the TG sites, though there are different error sources for this estimate as is discussed in the paper. In this study we estimate such vertical ground motion, for each TG site, from the slope of the SSH time series of the (non-seasonal) difference between the TG record and the altimetry measurement at a point closest to the TG. Where possible, these estimates are further compared with those derived from nearby continuous Global Positioning System (GPS) data series. These results on vertical ground motion along the Mediterranean and Black Sea coasts provide useful source data for studying, contrasting, and constraining tectonic models of the region. For example, in the eastern coast of the Adriatic Sea and in the western coast of Greece, a general subsidence is observed which may be related to the Adriatic lithosphere subducting beneath the Eurasian plate along the Dinarides fault.     

集成奇异谱分析和自回归滑动平均预测日本近海海平面变化

本文从日本沿岸选取了28个验潮站及联测的GPS站,利用奇异谱分析（Singular Spectrum Analysis,SSA）和SSA+自回归滑动平均（Auto Regression Moving Average,ARMA）方法预测了2014—2018年的近海海平面变化和地壳垂直变化.并用同时段的验潮及GPS的实际测量值进行验证,结果显示,SSA+ARMA预测的相对海平面精度为0.0357~0.0607 m,地壳垂直运动的精度为0.0049~0.0077 m,绝对海平面的精度为0.0433~0.0683 m,且三者SSA+ARMA的预测结果均优于只用SSA预测的结果.在此基础上本文利用SSA+ARMA预测了日本沿岸2019—2023年的近海绝对海平面变化,结果显示,2019—2023年的平均海面高较往年（2014—2018）升高0.0353 m,2003—2023年绝对海平面的变化率为0.0039 m·a^-1,预测结果较为理想.     

Geodetic Measurements of Crustal Deformation in the Western Mediterranean and Europe

—Geodetic measurements of crustal deformation over large areas deforming at slow rates (<5 mm/yr over more than 1000 km), such as the Western Mediterranean and Western Europe, are still a challenge because (1) these rates are close to the current resolution of the geodetic techniques, (2) inaccuracies in the reference frame implementation may be on the same order as the tectonic velocities. We present a new velocity field for Western Europe and the Western Mediterranean derived from a rigorous combination of (1) a selection of sites from the ITRF2000 solution, (2) a subset of sites from the European Permanent GPS Network solution, (3) a solution of the French national geodetic permanent GPS network (RGP), and (4) a solution of a permanent GPS network in the western Alps (REGAL). The resulting velocity field describes horizontal crustal motion at 64 sites in Western Europe with an accuracy on the order of 1 mm/yr or better. Its analysis shows that Central Europe behaves rigidly at a 0.4 mm/yr level and can therefore be used to define a stable Europe reference frame. In that reference frame, we find that most of Europe, including areas west of the Rhine graben, the Iberian peninsula, the Ligurian basin and the Corsica-Sardinian block behaves rigidly at a 0.5 mm/yr level. In a second step, we map recently published geodetic results in the reference frame previously defined. Geodetic data confirm a counterclockwise rotation of the Adriatic microplate with respect to stable Europe, that appears to control the strain pattern along its boundaries. Active deformation in the Alps, Apennines, and Dinarides is probably driven by the independent motion of the Adriatic plate rather than by the Africa-Eurasia convergence. The analysis of a global GPS solution and recently published new estimates for the African plate kinematics indicate that the Africa-Eurasia plate motion may be significantly different from the NUVEL1A values. In particular, geodetic solutions show that the convergence rate between Africa and stable Europe may be 30–60% slower than the NUVEL1A prediction and rotated 10–30° counterclockwise in the Mediterranean.     

Trace organic contamination in the Americas: An overview of the US National Status & Trends and the International ‘Mussel Watch’ programmes

The National Status & Trends (NS&T, 1986–1993) and the International Mussel Watch (IMW, 1991–1992) programmes provide a good coverage of a broad range of environmental conditions along the North, Central and South American coasts. Total concentrations of DDTs, chlordane-related compounds, PCBs and PAHs present fairly homogeneous distributions along the northern Gulf of Mexico coast, with very few sites showing extremely high or low concentrations. In contrast, a larger variability in the geographical distribution of some of these organic contaminants was observed for IMW sites. For example, high concentrations of DDT and its metabolites, DDD and DDE, were generally found in tropical and subtropical areas as compared to more temperate zones of South America. ‘Industrial’ contaminants, such as PCBs and PAHs, have similar distributions with the highest concentrations encountered generally along the southern South Atlantic coast. An overall comparison of the concentrations of these organic contaminants measured at NS&T and IMW sites indicates that contamination is significantly higher along the northern coast of the Gulf of Mexico.     

Comparative analysis of upwelling influence between the western and northern coast of the Iberian Peninsula

Upwelling conditions have been simultaneously analyzed along the western and northern coast of the Iberian Peninsula in terms of wind forcing and water temperature response. The wind forcing analysis showed that the season under more upwelling favorable conditions corresponds to spring-summer (April-September) along the western coast and only to summer (June-August) along the northern one. Taking into account the upwelling period common to both coasts (June-August), it was observed that the occurrence of upwelling events simultaneously along both coasts is the most probable situation (∼46%) followed by upwelling unfavorable conditions also along both coasts (∼26%). The analysis of sea surface temperature data also showed the existence of an upwelling season in spring-summer along both coasts, although upwelling events are more frequent and intense along the western coast than along the northern one. Chlorophyll concentrations showed a high seasonal variability at the western coast with the highest concentrations values in spring-summer months while at the northern coast the maximum values were observed in spring and autumn.     

Crustal loading in vertical GPS time series in Fennoscandia

We compare time series of vertical position from GPS with modelled vertical deformation caused by variation in continental water storage, variation in the level of the Baltic Sea, and variation in atmospheric pressure. Monthly time series are used. The effect of continental water storage was calculated from three different global models. The effect of non-tidal variation in Baltic Sea level was calculated using tide gauge observations along the coasts. Atmospheric loading was computed from a numerical weather model. The loading time series are then compared with three different GPS time series at seven stations in Fennoscandia. A more detailed analysis is computed at three coastal stations. When the monthly GPS time series are corrected using the load models, their root-mean-square scatter shows an improvement between 40 and 0%, depending on the site and on the GPS solution. The modelled load effect shows a markedly seasonal pattern of 15 mm peak-to-peak, of which the uncorrected GPS time series reproduce between 60 and 0%.     

Rocky-shore communities as indicators of water quality: a case study in the Northwestern Mediterranean

The collection of 152 samples from the upper sublittoral zone along the rocky coasts of Catalonia (Northwestern Mediterranean) was carried out in 1999 in order to test the suitability of littoral communities to be used as indicators of water quality in the frame of the European Water Framework Directive. Detrended correspondence analysis were performed to distinguish between different communities and to relate communities composition to water quality. Samples collected in reference sites were included in the analysis. Mediterranean rocky shore communities situated in the upper sublittoral zone can be used as indicators of the water quality: there is a gradient from high to bad status that comprises from dense Cystoseira mediterranea forests to green algae dominated communities. The geographical patterns in the distribution of these communities show that the best areas are situated in the Northern coast, where tourism is the main economic resource of the area, and the worst area is situated close to the metropolitan zone of Barcelona with high population and industrial development. Thus, Mediterranean sublittoral rocky shore communities are useful indicators of water quality and multivariate analysis are a suitable statistical tool for the assessment of the ecological status.     

Monitoring Sea Level in the Coastal Zone with Satellite Altimetry and Tide Gauges

We examine the issue of sustained measurements of sea level in the coastal zone, first by summarizing the long-term observations from tide gauges, then showing how those are now complemented by improved satellite altimetry products in the coastal ocean. We present some of the progresses in coastal altimetry, both from dedicated reprocessing of the radar waveforms and from the development of improved corrections for the atmospheric effects. This trend towards better altimetric data at the coast comes also from technological innovations such as Ka-band altimetry and SAR altimetry, and we discuss the advantages deriving from the AltiKa Ka-band altimeter and the SIRAL altimeter on CryoSat-2 that can be operated in SAR mode. A case study along the UK coast demonstrates the good agreement between coastal altimetry and tide gauge observations, with root mean square differences as low as 4 cm at many stations, allowing the characterization of the annual cycle of sea level along the UK coasts. Finally, we examine the evolution of the sea level trend from the open to the coastal ocean along the western coast of Africa, comparing standard and coastally improved products. Different products give different sea level trend profiles, so the recommendation is that additional efforts are needed to study sea level trends in the coastal zone from past and present satellite altimeters. Further improvements are expected from more refined processing and screening of data, but in particular from the constant improvements in the geophysical corrections.     

北京地区区域性形变场与近期强震危险性研究

分析1998－2000年期间水准和GPS测量给出的北京地区区域性形变场的背景值及其与定点断层形变观测值的关系。结果表明：（1）该地区的大面积垂直形变速率及速率梯度值在华北地区的通常 数值之下，也低于若干大地震前的相应异常特征值；（2）该区由GPS方法显示的大面积水平形变速率也属于较低水平；（3）定点观测的断层形变速率（垂直向和水平向）与区域性的背景值相当；（4）根据大面积形变场的 断层形变异常水平，预计近期（1－3年内）北京地区不会发生较强地震。     

New insights on the tsunami recording of the May, 21, 2003, Mw 6.9 Boumerdès earthquake from tidal data analysis

We analyzed sea level data from a set of tide gauge stations located in the central and western Mediterranean Sea, that recorded the tsunami generated by the Mw 6.8 Boumerdès earthquake striking the coast of Algeria on May 21, 2003. This earthquake caused more than 2200 victims and thousands of injured. The causative fault was located a few kilometers offshore and during the rupture a tsunami was triggered. Waves were felt along a large part of the western and northern Mediterranean coasts, and in the Balearic islands waves higher that 2 m were measured. In this paper we analyze a more complete tidal data set, with respect to previous studies, now consisting of 22 tidal stations located in Italy, France and Spain. To characterize the change of the tidal signal at each station we used the Empirical Mode Decomposition (EMD). By means of this technique, which is suitable to analyze and to characterize the dynamical behavior of non-stationary time series, we provide a precise measurement of the arrival times and amplitudes at the tidal stations and identify how this tsunami affected the principal and long term tidal components. Our findings improve previous results for this earthquake, since they allow the detection of significant amplitude fluctuations associated with the tsunami in the majority of stations, including the farthest ones.     

5·12汶川地震地表破裂基本参数的再论证及其构造内涵分析

地震地表破裂基本参数是反演地震破裂过程的基本约束条件和预测其他活动断层地震危险性不可缺少的物理量.以野外地表破裂带重要观测点全站仪或差分GPS仪实测数据为基础,结合高分辨率遥感资料解译、先存断层陡坎构造地貌标志的识别、以及地形测绘资料的考证等,重新论证了5·12汶川地震地表破裂带展布样式、长度、最大同震位移值等基本参数.结果表明,地震地表破裂带长度可达240 km,最大垂直位移为6.5±0.5 m,最大右旋走滑位移4.9 m,基于倾角向下变缓逆断层模型推测汶川地震在龙门山推覆构造带中段产生了最大~7 m的地壳缩短量,说明青藏高原东缘横向逆断层为将高原内部东向水平运动转换为高原隆升的转换构造,这一研究结果有助于深化认识青藏高原东缘隆升机理.     

Structure of the present-day velocity field of the crust in the area of the Central-Asian GPS network

The structure of the vector field of present-day horizontal velocities on the Earth’s surface is investigated with the use of the territory covered by the Central-Asian GPS network as an example. A method of identification of groups of GPS points (statistically rigid clusters), for which the rate of change in distances between them is virtually zero, is proposed and realized. Sites of the Earth’s surface (regions) containing such groups of GPS points, within the required measurement accuracy, move in the horizontal plane as two-dimensional rigid bodies. The clustering algorithm, which is based on the Student t statistics in determining the so-called statistical “sample cost,” is developed and carefully tested. The results of identification of regions take into account possible random errors in velocity measurements and do not depend on the chosen frame of reference. The method of identification of regions is sufficiently stable with respect to variations in the number of GPS sites used for clustering. Of all the sites of the Central-Asian GPS network, 323 points were selected for clustering. These sites were measured from 3 to 11 times over an 11-year interval of observations (1995–2005). The estimates of errors of velocity measurement for these sites must not exceed 1.0 mm/yr. As a result, 29 statistically rigid clusters, containing from 3 to 17 GPS sites, were identified, and the kinematic regimes of motion of regions corresponding to these clusters were determined with respect to the stable part of Eurasia. With the general direction of the translatory motion of regions toward the north, the majority of them rotate counterclockwise. Nearly one third of GPS sites do not participate in the formation of clusters; these points fall into the interregional space (IRS), which is characterized by increased strain rates. The IRS structure is partitioned into zones with four directions, of which two directions virtually coincide with directions of the principal axes of the regional strain rate tensor, and the two other directions are oriented diagonally to the principal axes. The axis of the maximum rate of the regional shortening has a north-northwestern orientation. It is in this direction (mainly along the IRS) that the crust’s contraction takes place. There is no spatial correlation between IRS zones and geological faults; however, their angular distributions and the directions of strike-slips on them are interrelated. The resulting patterns of regional motions and IRS deformations consistently reflect the dynamic action of the Indian plate on the territory under investigation.     

Mass-induced sea level variations in the Red Sea from GRACE,steric-corrected altimetry,in situ bottom pressure records,and hydrographic observations

An annual amplitude of ∼18 cm mass-induced sea level variations (SLV) in the Red Sea is detected from the Gravity Recovery and Climate Experiment (GRACE) satellites and steric-corrected altimetry from 2003 to 2011. The annual mass variations in the region dominate the mean SLV, and generally reach maximum in late January/early February. The annual steric component of the mean SLV is relatively small (<3 cm) and out of phase of the mass-induced SLV. In situ bottom pressure records at the eastern coast of the Red Sea validate the high mass variability observed by steric-corrected altimetry and GRACE. In addition, the horizontal water mass flux of the Red Sea estimated from GRACE and steric-corrected altimetry is validated by hydrographic observations.     

Parasite communities in the red mullet, Mullus barbatus L., respond to small-scale variation in the levels of polychlorinated biphenyls in the Western Mediterranean

We examined parasite populations and communities in the Mediterranean sentinel fish species, Mullus barbatus, sampled at a small-scale PCB gradient at the shelf sediments off Catalonian coasts of the Western Mediterranean. A recurrent feature at both the population and community level was the differentiation of the samples along the increasing PCB levels simultaneously registered in the sediments. Both directly transmitted ectoparasites and endoparasites with complex life-cycles transmitted via food chains exhibited a decrease in abundance with the increase in PCB levels. Parasite numerical responses translated into significant differences in infracommunity structure with decreasing predictability associated with increasing PCB levels. The abundance of two species, the specialist Opecoeloides furcatus and the generalist nematode Hysterothylacium fabri, contributed substantially to the observed dissimilarity between infracommunity samples along the gradient. The observed parasite responses to moderate levels of pollution were simultaneously validated by both chemical monitoring and effect biomarkers.     

Coupling of phytoplankton and ciliate biomasses to environmental factors along the north coast of Sfax (Tunisia,Eastern Mediterranean Sea)

The phytoplankton and ciliate biomasses coupled with environmental factors were investigated in 15 transects in north coasts of Sfax (Tunisia, Eastern Mediterranean Sea) in July 2007. The phytoplankton biomass was dominated by Bacillariophyceae (89.66%), followed by Dinophyceae (10.07%), Coccolithophorideae (0.96%), Cyanobacteriae (0.21%), Chlorophyceae (0.03%) and Euglenophyceae (0.01%). Coscinodiscus sp. (93.26%) was the most abundant species of Bacillariophyceae group and associated with a high nutrient availability. Ciliate biomass was highly variable, with a large dominance of Spirotrichea, up to 96.2%. Biomass followed distinct patterns because of differences in the observed organism biovolumes. The spatial distribution of the ciliates biomass seems to be dependent on environmental factors and probably on their capacity to exploit a wide range of food resources including phytoplankton. The pollution generated by the phosphate-treating manufactory influenced the spatial phytoplankton and ciliate community’s distribution and their diversity along the north coast of Sfax.     

Comparison of Snow Data Assimilation System with GPS reflectometry snow depth in the Western United States

In this study, we compare gridded snow depth estimates from the Snow Data Assimilation System (SNODAS) with snow depth observations derived from GPS interferometric reflectometry (GPS‐IR) from roughly 100 Plate Boundary Observatory sites in the Western United States spanning four water‐years (2010–2013). Data from these sites are not assimilated by SNODAS; thus, GPS‐IR measurements provide an independent data set to evaluate SNODAS. Our results indicate that at 80% of the sites, SNODAS and GPS‐IR snow depth agree to better than 15‐cm root mean square error, with correlation coefficients greater than 0.6. Significant differences are found between GPS‐IR and SNODAS for sites that are distant from other point measurements, are located in complex terrain or are in areas with strong vegetation heterogeneities. GPS‐IR estimates of snow depth are shown to provide useful error characterization of SNODAS products across much of the Western United States and may have potential as an additional data assimilation source that could help improve SNODAS estimates. © 2014 The Authors. Hydrological Processes published by John Wiley & Sons Ltd.     

Realization of the Hungarian geodynamic GPS reference network

The Pannonian Basin, which includes Hungary, tectonically belongs to the Eurasian Plate and is considered to be relatively quiet. Detailed geological studies revealed four main tectonic units in this area—the Tisza, Pelso, Austro-Alpine and Vepor units. All of these can be genetically related to tectonic processes in the Mediterranean and Alpine-Adria region.In 1989 the Satellite Geodetic Observatory (SGO) in cooperation with several institutions has initiated the establishment of a geodynamic global positioning system (GPS) Reference Network (HGRN) for three-dimensional deformation studies in Hungary. The HGRN consists of 13 primary sites which were selected according to geological and geophysical considerations and satisfied international standards for tectonic studies with the GPS technique. Particular care was devoted to the point marks concerning mechanical stability and the repeatability of antenna set-ups at the HGRN sites, therefore a point mark and a mechanical adapter to mount the GPS antenna had been developed at the SGO for this purpose. This point mark has been used at all HGRN sites. A GPS Datum Point was also established for Hungary in 1990 at the Satellite Geodetic Observatory; here quasi continuous observations are foreseen. The Penc station has been accepted as a fiducial station of the International GPS Geodynamic Service (IGS).The zero epoch measurements were completed in fall 1991 and monitoring is planned every second year at least for the next 10 years.Preliminary processing of the data has been carried out in the SGO, Penc and at the Lustbühel Observatory at Graz, using the TRIMVEC PLUS and BERNESE V3.2 programs respectively     

用多种数据构建2008年汶川特大地震同震位移场

本文主要以GPS、精密水准观测和卫星SAR遥感图像分析2008年汶川特大地震同震位移特征.GPS数据包括:(1)四川盆地和川西高原地区各类国家等级GPS网点复测;(2)沿破裂带国家天文大地网GPS复测.前者推算的同震位移测定精度优于2 cm,后者6~8 cm.SAR遥感资料包括:(1)ALOS 卫星升轨相位干涉图像,精度优于8 cm;(2)ALOS和ENVISAT卫星影像合成的三维位移图,精度优于0.5 m.同震位移场显示,断层下盘(四川盆地)变形总体呈扇形集中指向震中,断层上盘(龙门山)变形总体上呈逆时针旋转态势,最大的实测水平位移5.5 m.汶川、理县、茂县等地测站位移指向破裂带方向,而平武、青川等地测站逐渐转变为平行,乃至远离破裂带方向,与汶川地震逆冲兼走滑的破裂特征一致.断层上盘大幅隆升,下盘靠近断层的区域以下沉为主,远场表现为幅度很小的隆升,垂直升降区域间,有一条与龙泉山断裂带平行的升降过渡带,调节龙泉断层的应力状态.用实测变形场检验多个地震波破裂模型表明,近场(距离断层50 km) 模型形变准确度可达40~50 cm, 远场精度优于5 cm.     

Benthic primary producers--a neglected environmental problem in Mediterranean maricultures?

Marine fish farming is increasing rapidly in the Mediterranean and in contrast to the Atlantic the coastal zone in the Mediterranean is characterized by clear waters with high transparency. This allows benthic primary producers such as the slow-growing seagrass Posidonia oceanica to grow at large depths at locations suitable for fish farming and generating a conflict between the conservation of these meadows and the growth of aquaculture operations in the Mediterranean. In this paper we review the current knowledge on environmental interactions between fish farming and benthic primary producers with particular focus on P. oceanica, as this seagrass is a key component along Mediterranean coasts. The recovery times of P. oceanica are very long, in the order of centuries, and losses of this species are thus considered to be irreversible at managerial time scales.     

北斗导航定位系统（BDS）下地壳运动监测精度分析

为分析北斗导航定位系统（BDS）在地壳运动监测领域的数据精度,选取中国大陆构造环境监测网络（陆态网络）2018—2019年川滇地区GPS、BDS多系统观测站点数据,分别对GPS、BDS记录的数据进行解算,从三维坐标解、位置时间序列及速度场等方面,对比分析二者在地壳运动监测中的不同,综合分析BDS对地壳运动监测精度。结果表明,BDS定位精度达到cm级,但仍低于GPS精度,BDS、GPS速度场模型运动方位和速度值有所不同,垂向差异较为明显。总体来看,北斗系统数据满足高精度定位解算要求,可用于监测形变量较大的区域地壳运动。