Geodetic constraints to the kinematics of the Kapareli fault, reactivated during the 1981, Gulf of Corinth earthquakes

Comparison of historical and of post-seismic triangulation data is used to model vertical crustal movements in the vicinity of the Kapareli Fault (or the Alkynonides earthquakes North Fault), one of the two antithetic normal faults which reactivated during the 1981, Gulf of Corinth (Ms = 6.7) earthquakes. This fault is characterized by a much smaller geomorphological signature than the South (or Perachora) fault of the same seismic sequence. Analysis of geodetic data on the basis of polynomial filtering and elastic dislocation modelling, as well as analysis of structural and coastal change data permits us to conclude that the upper bound in the uncertainty level of most of the available elevation changes is 20–30 cm, usually lower than the corresponding dislocation signal. In addition, the available geodetic data have a systematic pattern and are consistent with structural data. For this reason they permit more precise constraints on the geometry and the role of the Kapareli Fault (or the Alkyonides earthquakes North Fault): its total length is estimated about 17 km, about 50% longer than its surface trace; about 30–40 cm subsidence of its hanging wall, as well as at least 15 cm maximum uplift of its footwall is also inferred. This new evidence suggests that although in the long-term the Kapareli fault may represent a rather secondary, antithetic fault to the Alkyonides earthquakes South (Perachora) fault, during the 1981 earthquakes it probably had a more important structural role.     

Rare and new small-celled taxa of Navicula s. str. in the Gulf of Gdansk and in its freshwater affluents

Presented are results of morphological (LM and SEM) and taxonomical investigations on very small-sized Navicula spp. from the brackish waters of the Gulf of Gdansk and some freshwater affluents. Detailed studies revealed that most of the taxa in question are either new for science or previously described but rather poorly known. Dominant in that assemblage of extraordinarily small-celled Navicula species, specimens mostly below 10 μm in length, are Navicula germanopolonica Witkowski & Lange-Bertalot and Navicula paulschulzii Witkowski & Lange-Bertalot as established taxa. New for science are Navicula aleksandrae, Navicula bozenae and Navicula viminoides ssp. cosmomarina. From common freshwater habitats no species are known that could be confused with the new taxa.     

Sources, distribution and composition of the suspended sediments, Kuwait Bay, Northern Arabian Gulf

Qualitative and quantitative assessment of suspended sediment levels and transport pathways in Kuwait's northern territorial waters are described, with special reference to Kuwait Bay. Near-surface water samples were collected from 12 stations, covering the whole of the embayment. Suspended sediment concentrations (SSCs) were derived. Heavy metal concentrations, mineralogical composition and grain size constituents were derived for the suspended sediments retained on the filter papers.The distribution pattern of the suspended sediments indicates the possibility of tidal current activity, dust fallout contribution and to a lesser extent, the effect of the Shatt Al-Arab (especially in northeastern Kuwait Bay). The distribution of various types of sediments and the variations of their textural, compositional and concentrations are controlled largely by the hydrodynamic conditions, nature of sediments.The results demonstrate clearly the potential impact of the Gulf War as manifested by the increase of SSC in 1992, compared to 1989/1990. Such an input may be attributed also to drainage processes from the Iraqi marshes. More studies are required to understand the environmental impacts of the suspended matter and the associated pollutants.     

Dating recent colluvial sequences with Pb and Cs along an active fault scarp, the Eliki Fault, Gulf of Corinth, Greece

Reliable dating is an essential element of palaeoseismological studies, yet whilst a suite of geochronological methods can now provide late Quaternary age control it remains very difficult to date modern events (i.e., those occurring within the last 150 years). This is significant because the starting point for many palaeoseismological investigations is a modern surface-rupturing event, whose geological effects need to be disentangled in trench stratigraphies from palaeoseismic ruptures. Two dating methods which, in combination, can provide robust dating control in recently deposited sediments are the ²¹⁰Pb and ¹³⁷Cs dating methods. Here, we test the applicability of using ²¹⁰Pb and ¹³⁷Cs to date colluvial sediments exposed in three trenches excavated across an earthquake fault—the Eliki fault, Gulf of Corinth, Greece—which ruptured in an earthquake in 1861. The ²¹⁰Pb and ¹³⁷Cs profiles observed in these colluvial sequences are relatively erratic due to the mixed nature of the sediments, i.e., their deposition in an environment where the supply of slope sediments is driven by seasonal rainfall, causing non-uniform sediment accretion and sediment reworking. In one trench, however, ²¹⁰Pb dating, corroborated by ¹³⁷Cs dating, indicates that a proposed post-1861 surface colluvial unit has been deposited over the period 1950 AD–present (at a rate of ca. 9 mm/year), and overlies a significantly older unit (>120 years old). The dating control provided here by ²¹⁰Pb and ¹³⁷Cs dating corroborates the published interpretation of the trench stratigraphy, and refines the ¹⁴C-based estimated dates for the upper unit. At two other trenches ²¹⁰Pb and ¹³⁷Cs dating only provided minimum ages (based on the presence or absence of ²¹⁰Pb_excess and ¹³⁷Cs). Such approximate ages, however, may still useful in corroborating interpretations made using the trench stratigraphy, or, at sites which have long earthquake recurrence intervals, determining which earthquake event was responsible for a particular bed offset.     

Seismic strain rates and distributed continental deformation in the northern Andes and three-dimensional seismotectonics of northwestern South America

Remote sensing and field studies of several extensional basins along the northern margin of the Gulf of Aden in Yemen show that Oligocene–Miocene syn-rift extension trends N20°E on average, in agreement with the E–W to N120°E strike of main rift-related normal faults, but oblique to the main trend of the Gulf (N70°E). These faults show a systematic reactivation under a 160°E extensional stress that we interpret also as syn-rift. The occurrence of these two successive phases of extension over more than 1000 km along the continental margin suggests a common origin linked to the rifting process. After discussing other possible mechanisms such as a change in plate motion, far-field effects of Arabia–Eurasia collision, and stress rotations in transfer zones, we present a working hypothesis that relates the 160°E extension to the westward propagation since about 20 Ma of the N70°E-trending, obliquely spreading, Gulf of Aden oceanic rift. The late 160°E extension, perpendicular to the direction of rift propagation, could result from crack-induced extension associated with the strain localization that characterises the rift-to-drift transition.     

北部湾经济圈的形成和开发设想

随着中越关系的改善以及南昆铁路即将通车,大西南与北部湾的联系日渐密切。以北部湾 中心,将迅速形成区域合作体系－经济圈。文中分析了北部湾的战略区位及其形成经济圈的区域环境的条件,认为其区位优越,且无论是国际大环境还是区域内部小环境都有利于经济圈的形成;还分析了北部湾经济圈形成所必需的物质基础,认为其具有大储量的现代共业资源、曲折的海岸线和众多的优良港湾、丰富的热带来势带作物资源和海洋生物资源以及特有