Retrieving sea-wave spectra using satellite-imagery spectra in a wide range of frequencies

A method to register sea-wave spectra using optical aerospace imagery has been developed. The method is based on the use of retrieval operators both in areas of high and low spatial frequencies, including the areas of spectral maximum. The approach to adjust and validate the method developed using sea truth data obtained by string wave recorders has been suggested. This paper presents the results of using the suggested method to study sea-wave spectra using high-resolution satellite imagery for various water areas under different conditions of wave generation.     

Possible manifestations of underwater mud volcanoes based on results of sonar investigations in region of Taman Peninsula

This paper presents the results of three-dimensional acoustic seabed mapping in the region of the Taman Peninsula in the Black Sea using an interferometric side-scan sonar and an acoustic profiler. Mapping has revealed underwater objects identified as manifestations of underwater mud volcanism. Detailed analysis of sonar images of the relief and seabed profiles in the region of the objects has confirmed the original hypothesis.     

Sources of Zircons from Cretaceous and Lower Paleogene Terrigenous Sequences of the Southern Koryak Upland and Western Kamchatka

The mineral composition of sandstones from Cretaceous–Lower Paleocene terrigenous sequences of the western Kamchatka–Ukelayat zone (southern Koryak Upland, western Kamchatka) suggests that the Okhotsk–Chukot volcanogenic belt and fragments of the Uda–Murgal island arc served as the most probable provenance. Fission-track dating of zircon showed that sandstones from this zone contain detrital zircon of several different-age populations. Fission tracks in zircon grains were nor subjected to secondary ignition. The age of young zircon population coincides with the biostratigraphic age of host sequences. Thus, results of dating of detrital zircon grains from sandstones, which did not experience heating above 215–240°C, indicate that this method is appropriate for dating fossil-free terrigenous sequences. The young zircon population in the sandstones is related to erosion of plagiogranite and diorite intrusions of the Uda–Murgal arc and outer zone of the Okhotsk–Chukot volcanic belt exposed at the day surface owing to differential vertical movements and rapid exhumation of blocks.     

Numerical algorithm for the dynamic analysis of base-isolated structures with dry friction

This paper deals with the techniques for solving ordinary differential equations with essential nonlinearity arising from the representation of frictional force by the sign function of the relative velocity. This problem is connected with dynamic behavior studies of base-isolated structures with dry friction devices.Mathematical evidence is presented concerning the inaccuracies of the solution which are connected with the representation of the frictional force by the sign function. An approximation of this sign model is made on the basis of the appropriate linearization of a small part of the frictional force function. A numerical algorithm for the dynamic analysis of base-isolated structures with dry friction is proposed. Numerical tests are carried out for establishing the exactness of the proposed techniques. The obtained results prove the accuracy of the techniques.     

Near-vertical seismic reflection image using a novel acquisition technique across the Vrancea Zone and Foscani Basin, south-eastern Carpathians (Romania)

The DACIA PLAN (Danube and Carpathian Integrated Action on Process in the Lithosphere and Neotectonics) deep seismic sounding survey was performed in August–September 2001 in south-eastern Romania, at the same time as the regional deep refraction seismic survey VRANCEA 2001. The main goal of the experiment was to obtain new information on the deep structure of the external Carpathians nappes and the architecture of Tertiary/Quaternary basins developed within and adjacent to the seismically-active Vrancea zone, including the Focsani Basin. The seismic reflection line had a WNW–ESE orientation, running from internal East Carpathians units, across the mountainous south-eastern Carpathians, and the foreland Focsani Basin towards the Danube Delta. There were 131 shot points along the profile, with about 1 km spacing, and data were recorded with stand-alone RefTek-125s (also known as “Texans”), supplied by the University Texas at El Paso and the PASSCAL Institute. The entire line was recorded in three deployments, using about 340 receivers in the first deployment and 640 receivers in each of the other two deployments. The resulting deep seismic reflection stacks, processed to 20 s along the entire profile and to 10 s in the eastern Focsani Basin, are presented here. The regional architecture of the latter, interpreted in the context of abundant independent constraint from exploration seismic and subsurface data, is well imaged. Image quality within and beneath the thrust belt is of much poorer quality. Nevertheless, there is good evidence to suggest that a thick (10 km) sedimentary basin having the structure of a graben and of indeterminate age underlies the westernmost part of the Focsani Basin, in the depth range 10–25 km. Most of the crustal depth seismicity observed in the Vrancea zone (as opposed to the more intense upper mantle seismicity) appears to be associated with this sedimentary basin. The sedimentary successions within this basin and other horizons visible further to the west, beneath the Carpathian nappes, suggest that the geometry of the Neogene and recent uplift observed in the Vrancea zone, likely coupled with contemporaneous rapid subsidence in the foreland, is detached from deeper levels of the crust at about 10 km depth. The Moho lies at a depth of about 40 km along the profile, its poor expression in the reflection stack being strengthened by independent estimates from the refraction data. Given the apparent thickness of the (meta)sedimentary supracrustal units, the crystalline crust beneath this area is quite thin (< 20 km) supporting the hypothesis that there may have been delamination of (lower) continental crust in this area involved in the evolution of the seismic Vrancea zone.     

Paleoproterozoic quartz-pebble conglomerate type uranium mineralisation in Mankarhachua area,Angul district,Orissa

Ground Radiometric survey of Paleoproterozoic pyritiferous quartz-pebble conglomerate (QPC) occurring to the north of Pallahara area led to the discovery of a QPC type uranium mineralisation near Mankarhachua village. Significant radioactivity is recorded in three sub-parallel uraniferous QPC horizons with metamorphosed pebbly to medium grained recrystallised massive sandstones. Detrital grains of uranothorite, thorite, radioactive allanite, monazite, zircon, minute uraninite grains in carbonaceous matter and thucolite contributes to the radioactive phases present in QPC matrix. Adsorbed U on limonite and goethite, secondary uranyl minerals in matrix, along bedding planes and fractures are commonly observed. This discovery has opened up a new horizon for future exploration for QPC type uranium mineralization in the area. The paper presents observations on geology, radioactivity, petrological and geochemical nature of the uraniferous QPC horizons.     

Geoarchaeological evidence on a Late Bronze Age earthquake,Ohrid Basin (North Macedonia)

Geoarchaeological investigations on the northeastern shore of Lake Ohrid revealed 3.5 m thick deepwater lacustrine sediments overlying terrestrial vegetation macrofossils, worked wood and abundant potsherds dated to the Late Bronze Age (LBA). Distinct contact of deepwater sediment with the sub-aerial weathered limestone bedrock point to a sudden increase in lake level. According to radiocarbon data, catastrophic flooding occurred shortly after 1214 yr bc. Because the area is located in a highly active seismic zone, we propose that this event was caused by tectonically induced, metre-scale coseismic subsidence related to faults bordering the Ohrid alluvial plain. Moreover, this event coincides well with a dramatic switch in the habitation and settlement strategy in the region. More important, however, is the finding that the age of the proposed massive tectonic event and change in habitation lies within the interval of the proposed ‘earthquake storm’ in the eastern Mediterranean dated to 1225–1175 bc. As the Ohrid-Korça zone belongs to the same tectonic province, a relationship between the abovementioned earthquakes and the proposed event can be expected. This research therefore might provide the first direct evidence of a large-scale earthquake event linkable to the LBA collapse of Europe's first urban civilisation in the Aegean.     

Deep seismically active fracture zones in ecuador and northern peru

Summary A system of 8 seismically active fracture zones was delineated on the basis of the distribution of earthquake foci in the continental lithosphere of Ecuador. The position and width of the outcrop, thickness, dip and maximum depth of the individual fracture zones were estimated and correlated with surface geological and tectonic phenomena, volcanism and hydrothermal manifestations. The existence and strike of the fracture zones was independently confirmed by the occurrence of historical disastrous earthquakes.

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Visiting professors at Instituto Geofísico and Facultad de Geología, Minas y Petróleos, Escuela Politécnica Nacional, Quito (Ecuador).     

Morphological peculiarities of Calanus finmarchicus and Calanus glacialis in the areas of the co-existence of their populations

Morphological studies of the females of Calanus finmarchicus, C. glacialis, and C. hyperboreus were performed for specimens sampled in different areas of the Greenland, Barents, Kara, and Laptev seas. Intraspecific variability was found for the ratio of the specimens characterized by different types of setae patterns on the endopodites of C. glacialis and C. finmarchicus. The variability of this parameter did not relate to the environmental peculiarities of the sampling sites and did not depend on the temperature regime. We assume that such differences may be the result of the hybridization of C. glacialis and C. finmarchicus due to the similarity of their reproduction systems and the overlapping of the body size ranges.