Variations in phytoplankton development in the eastern Gulf of Finland

Materials of seasonal observations of phytoplankton at two permanent stations in the inner and outer parts of the Neva estuary. The obtained data demonstrate the changes that took place in the species composition and the quantitative development of phytoplankton during the past two decades. The authors associate these changes with anthropogenic factors, hydrological characteristics, and large-scale cyclic variations in hydrometeorological conditions.     

Estimation of the nutrient load on the Gulf of Finland from the Russian part of its catchment

The nutrient load on the Gulf of Finland, the Baltic Sea, is estimated taking into account the export of nutrients from Lake Ladoga with Neva runoff, from the Chudsko-Pskovskoe Lake with Narva runoff, from a partial watershed of the Gulf of Finland, and wastewater discharges from St. Petersburg. The data used include the materials of state monitoring of water bodies and state statistical reports on northwestern Russia, materials of GUP Vodokanal Sankt Peterburga, the results of earlier researches of water quality formation in Lake Ladoga, the Gulf of Finland, and on their catchment, and the results of calculation of nutrient load on the gulf with the use of a model developed in the Institute of Limnology, RAS. Currently, the annual nutrient load on the Gulf of Finland is ∼5200 t P_tot and 70800 t N_tot. The phosphorus load exceeds the admissible levels recommended by the Helsinki Commission, thus suggesting the need to search for real ways to reduce the load in the future.     

The concentration and composition of polyaromatic hydrocarbons in small rivers in the drainage area of the eastern Gulf of Finland

The results of examining the concentrations of 16 major polycyclic aromatic hydrocarbons are given. The examined samples were taken in the territory of Leningrad province and in the eastern Gulf of Finland in different seasons. Two seasonal natural profiles of polycyclic aromatic hydrocarbons were constructed, conventionally, for the spring and the autumn. The dominating effect on the formation of the profile of polycyclic aromatic hydrocarbons is exerted by pyrogenous pollution sources in winter and petrogenic pollution sources in summer.     

Groundwater Runoff into the Gulf of Finland

Groundwater discharge into the Gulf of Finland is examined. Qualitative and quantitative estimates of groundwater runoff are given. It is established that, notwithstanding the relatively low rate of groundwater runoff, it has an essential effect on the environmental state of the coastal zone of the gulf.     

2005年1月18日乳山ML4.3地震序列

对2005年1月18日乳山ML4.3地震序列特征及烈度分布进行了介绍, 认为乳山ML4.3地震序列是一次能量衰减较快、频度起伏衰减的主-余型地震序列, 序列本身不具有明显的前兆意义.     

浅析2016年1月14日谢通门震群

通过对2016年1月14日西藏谢通门震群所在区域的地质构造背景、历史震例、震源机制和震情序列等参数分析,对该震群发震构造和震群序列类型进行判定.认为该震群发生在历史地震相同走向的构造断层上,为前兆性震群,该地区周边发生中强地震发震可能性较大.     

Source Parameters of the ML 3.8 Earthquake on January 20, 2000 near Meckenheim, Germany

In the early morning hours on January 20,2000 at 03:03:17 (UTC) an M_L = 3.8earthquake occurred east of the city ofMeckenheim. It awakened many people in theMeckenheim-Bonn-Siegburg area. At least 200people called the police or fire brigade inBonn. The earthquake was felt as far asLimburg (Westerwald) and east Belgium. Themaximum intensity (EMS) in theMeckenheim-Adendorf area was 5. Theinstrumental epicenter was located at50.60^° N latitude and 7.08^° Elongitude. Source depth was 9.5 km. Localmagnitude M_L was 3.8 ± 0.3 andseismic moment was 1.86*10¹⁴ Nm,corresponding to a momentmagnitude M_W of 3.4± 0.2.Following the Brune model, the sourceradius was 0.45 km with an averagedislocation of 1.0 cm and a 0.8 MPa stressdrop. The source mechanism from a firstmotion fault plane solution shows a normalfault mechanism with a significant strikeslip contribution. Trend and plunge of themajor and minor principal axes P/T are168^°/54^° and275^°/12^°, respectively. Aninversion of the moment tensor fromamplitudes of direct waves reveals a doublecouple mechanism with a smaller strike slipcontribution than the first motion faultplane solution, but also shows asignificant 16% non-double couplecomponent of the total moment. Theintensity epicenter was determined by agrid search algorithm and was found to be14 km east from the instrumental epicenter.The macroseismic magnitude was 3.6.     

Scenario of the January 1997 West Bohemia Earthquake Swarm

In order to learn more about the nature of the dynamic processes taking place in the West Bohemia/Vogtland earthquake swarm region, we investigated the temporal and spatial variations of the source mechanisms of the January 1997 swarm beneath Nový Kostel (NKC). Visual analyses of WEBNET seismograms of over 800 events revealed that a specific feature of this swarm was the occurrence of eight classes of multiplet events. The result of single-source, absolute moment tensor inversion of the P and SH peak amplitudes of a subset of 70 events representing all multiplet classes indicated that eight statistically significant types of mechanisms occurred during the swarm. Two of them, types A and B in our denotation, comprised all M _L 1.3 events and predominated in the swarm. Type A were pure strike-slip mechanisms or strike-slip mechanisms containing a small normal component, with a nearly pure double-couple source. For class B events, oblique-thrust faulting and non-double-couple components significant at a fairly high confidence level were typical. Type A events predominated in the southern subcluster of the swarm, whereas most of type B events occurred in the subcluster northwards from NKC. This indicates that two major seismogenic planes were active during the swarm. The swarm essentially developed in four phases: in the first, type A events prevailed and the southern plane was active; during the second, characterised by the occurrence of both type A and B events (the former in the southern, the latter predominantly in the northern subcluster), the activity of the swarm culminated; in the third and fourth, the occurrence of type B events in the northern plane predominated, and only weak single events occurred southwards from NKC. Mechanisms of types AB , C , D , E , F and G , which were typical for M _L 1.2 events, occurred randomly throughout the swarm. Type AB events were identified in both the southern and northern clusters, type C , E , F and G mechanisms only southwards from NKC. Type D events exhibited a large scatter of hypocentres which fell in neither the southern nor the northern cluster. Focal mechanisms like those reported in this study and with analogous temporal and spatial variations were observed by other authors already fifteen years ago in the 1985/86 earthquake swarm and may, therefore, be typical for the region under study.     

Modelling ice conditions in the easternmost Gulf of Finland in the Baltic Sea

To model ice conditions in the eastern Gulf of Finland, a high-resolution three-dimensional hydrodynamic model is coupled with the advanced sea-ice model HELMI (Haapala et al., 2005). To test the model in extreme situations, the ice pattern in the eastern Gulf of Finland was simulated for a mild ice winter (2007–2008) and for a moderate one (2003–2004). The reference runs were performed on the assumption that the ice in the model domain is fast ice if the sea depth is less than 10 m. Using this assumption, the ice thickness averaged over the Neva Bay (the easternmost part of the Gulf of Finland) is overestimated by the model for almost the entire wintertime in the mild winter and during the ice formation and melting periods in the moderate winter, as compared with the thickness reported in ice charts.     

北部湾6级地震前区域地震活动过程及预测启迪

对北部湾6级地震前后雷琼地区的地震活动阶段及过程进行了研究，介绍了由此所得到的区域地震预测思路的启迪，为非理想条件下依据地震孕育发展过程探索分析预报程序提供借鉴。     

从历史上的带头地震看1998年1月10日张北尚义地震的发震日期

用我们在１９９０年提出的带头地震,即异年倍九法来讨论１９９８年１月１０日张北尚义６．２级地震的发震日期,以供今后在临震预报中参考。     

Focal Fault and Stress Field of the Yao‘ an M 6.5 Earthquake on January15,2001

Using the 78 focal mechanism solutions of the fore shocks, main shock and after shocks of the earthquake sequence for the Yao'an earthquake, the characteristics of the focal faults and stress field for the earthquake sequence are analyzed. The results show that the main rupture plane of the Yao'an earthquake sequence is a tectonic fault with N50°W strike and steep dip and all the main shock, the fore shocks and the vast majority of after shocks occurred on the main rupture plane. A tectonic fracture with NNE-NE strike also participated in development process of the sequence. The focal stress field of the sequence dominated by principal compressional stress with nearly horizontal orientation SSE is consistent with the regional tectonic stress field. In the sequence development, the stress field in the focal region was complex with multi-azimuths and multi-action models and the focal rupture showed complex features with multi-directions and multi-patterns.     

1999年1月25日哥伦比亚6.0级地震概况

１９９９年１月２５日哥伦比亚西部发生６．０级地震,造成生命和财产的严重损失。文章概述了这次地震的情况,内容包括;震源参数,破坏和伤亡,救援情况,发震背景及地震造成的社会和经济影响。     

Sea level rise in the north-western part of the Arabian Gulf

Relative sea level variations in the north-western part of the Arabian Gulf have been estimated in the past using no more than 10 to 15 years of observations. In this study, we have almost doubled the period to 28.7 years by examining all available tide gauge data in the area and constructing a mean gauge time-series from seven coastal tide gauges. We found for the period 1979–2007 a relative sea level rise of 2.2 ± 0.5 mm/year. Using the subsidence observed at 6 GPS stations within a radius of 100 km of the tide gauges as an indication of the vertical land motion, the corresponding absolute sea level rise is 1.5 ± 0.8 mm/year that is in agreement with the global estimate of 1.9 ± 0.1 mm/year (Church and White, 2011) for the same studied period. By taking into account the temporal correlations we conclude that previous published results underestimate the true sea level rate uncertainty in this area by a factor of 5–10.     

Field Survey of the March 28, 2005 Nias-Simeulue Earthquake and Tsunami

On the evening of March 28, 2005 at 11:09?p.m. local time (16:09 UTC), a large earthquake occurred offshore of West Sumatra, Indonesia. With a moment magnitude (M _w) of 8.6, the event caused substantial shaking damage and land level changes between Simeulue Island in the north and the Batu Islands in the south. The earthquake also generated a tsunami, which was observed throughout the source region as well as on distant tide gauges. While the tsunami was not as extreme as the tsunami of December 26th, 2004, it did cause significant flooding and damage at some locations. The spatial and temporal proximity of the two events led to a unique set of observational data from the earthquake and tsunami as well as insights relevant to tsunami hazard planning and education efforts.     

Radiogeochemical zoning and mapping of bottom sediments in the Eastern Gulf of Finland

A procedure is proposed for geochemical mapping of the water area bottom based on the subdivision of raw data into two components, i.e., systematic (regional) and random (local). The former is used to determine regional characteristic of the spatial radionuclide distributions in bottom sediments to be utilized to identify large radiogeochemical regions, while the latter is used to identify local anomalies and evaluate their characteristics. The systematic component of the radiogeochemical field is determined by trend analysis. Next, cluster analysis, i.e., hierarchic clusterization of the results of trend analysis followed by associative classification, is used for radiochemical zoning of the water area. After that, maps are constructed, showing contour lines of the local component of radiogeochemical fields, represented by deviations of the value in the given point from the trend. The result is a single map showing the radiogeochemical regions with contour lines of normalized anomalous activities of the radionuclides under study. The practical application of the method is illustrated by radiogeochemical mapping of the bed in the Eastern Gulf of Finland.     

2022年1月8日青海门源6.9级地震短临异常跟踪分析

2022年1月8日青海门源县发生6.9级地震,此次地震前青海地区出现了大量地球物理观测异常。2021年10月下旬青海地区出现地磁垂直强度极化高值异常,10月27日异常台站最多,并在门源-祁连至兴海地区形成一个面积约为6.6×10⁴km²的高值异常区;此外,2021年7—11月青海地区8项地下流体观测数据出现准同步异常变化。结合青海及周边地区历史震例的分析结果,认为2021年11月23日至2022年1月23日,青海西北部地磁垂直强度极化高值区内可能发生5.6～6.4级地震。门源6.9级地震发生在地磁垂直强度极化异常出现后的73天,震中位于预测区的边缘,地震的发生时间和地点与预测意见一致,但震级超出预测意见上限值0.5级。此次地震前基于地球物理观测地震预测指标体系开展的短临异常跟踪分析过程,对中国大陆西部地震预报工作具有一定的参考意义。     

2001年1月26日印度古吉拉特邦7.8级地震综述

2001年1月26日印度古吉拉特邦发生7．8级地震，造成生命和财产的严重损失，这是该地区历史上发生的第二次大地震，引起国际社会的普遍关注，本文综述了这次地震的情况，内容包括：震源参数，发震背景，震灾情况，救援情况，地震造成的社会和经济影响以及值得思考的几个问题。