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151.
František Marek Reviewer F. Janák Reviewer V. Kropáček 《Studia Geophysica et Geodaetica》1971,15(1):100-104
Summary Virtual geomagnetic poles, corresponding to the directions of primary remanent magnetization of the neovolcanic occurrences studied in the Lower Jeseník, form a close group which is positionally considerably removed from the present geographic pole. By comparison with some published data on the extent of the secular variation of the geomagnetic field, a conclusion was drawn that the assumption of a practically simultaneous generation of the considered volcanites (over a period of about one third of the longest secular variation cycle) is at least twice as probable as the assumption of an expressive difference in their age. 相似文献
152.
Tomasz Janik Marek Grad Aleksander Guterch Ryszard Dadlez Jukka Yliniemi Timo Tiira G. Randy Keller Edward Gaczyski CELEBRATION Working Group 《Tectonophysics》2005,411(1-4):129-156
The large-scale CELEBRATION 2000 seismic experiment investigated the velocity structure of the crust and upper mantle between western portion of the East European Craton (EEC) and the eastern Alps. This area comprises: the Trans-European Suture Zone, the Carpathian Mountains, the Pannonian Basin and the Bohemian Massif. This experiment included 147 chemical shots recorded by 1230 seismic stations during two deployments. Good quality data along 16 main and a few additional profiles were recorded. One of them, profile CEL03, was located in southeastern Poland and was laid out as a prolongation of the TTZ profile performed in 1993. This paper focuses on the joint interpretation of seismic data along the NW–SE trending TTZ–CEL03 transect, located in the central portion of the Trans-European Suture Zone. First arrivals and later phases of waves reflected/refracted in the crust and upper mantle were interpreted using two-dimensional tomographic inversion and ray-tracing techniques. This modelling established a 2-D (quasi 3-D) P-wave velocity lithospheric model. Four crustal units were identified along the transect. From northwest to southeast, thickness of the crust varies from 35 km in the Pomeranian Unit (NW) to 40 km in the Kuiavian Unit, to 50 km in the Radom–Łysogóry Unit and again to 43 km in the Narol Unit (SE). The first two units are thought to be proximal terranes detached from the EEC farther to the southeast and re-accreted to the edge of the EEC during the Early Palaeozoic. The origin of the remaining two units is a matter of dispute: they are either portions of the EEC or other proximal terranes. In the area of the Polish Basin (first two units), the P-wave velocity is very low (Vp < 6.1 km/s) down to depths of 15–20 km indicating that a very thick sedimentary and possibly volcanic rock sequence, whose lower portion may be metamorphosed, is present. The velocity beneath the Moho was found to be rather high, being 8.25 km/s in the northwestern portion of the transect, 8.4 km/s in the central sector, and 8.1 km/s in the southeastern sector. 相似文献
153.
154.
Determination of three-dimensional in situ stresses from anelastic strain recovery measurement of cores at great depth 总被引:5,自引:0,他引:5
In order to examine whether the anelastic strain recovery (ASR) method can be applied for determining the in situ stress in hard rocks at great depths, the anelastic strain recovery of oriented cores was measured in six independent directions. The core specimens were taken from four depths within the range of about 2400–4500 m MD at the METI Niitsu well in Japan; the rock materials were mudstone, dolerite, basalt and andesite. For all the rocks the expansional anelastic strains were obtained, the magnitude of the strains in various directions continuously measured for 1 or 2 weeks was of the order of 1000 × 10− 6 in mudstone; in contrast, strains of the other cores did not exceed a few hundred microstrains. These strains were used for a three-dimensional analysis of the principal in situ stresses. At the third depth, the principal stress directions were considered to be affected by fractures pre-existing near the core, and showed the features of a very local stress state. With the exception of this data, the directions determined by the ASR method were in agreement with those determined using other in situ measurement methods. Based on two assumptions, i.e., (i) the rock stress in vertical direction is equal to density-related gravitational overburden stress, (ii) the ratio of anelastic strain recovery compliance of shear deformation mode and the compliance of volumetric deformation mode is equal to 2, the values of the three principal stresses were estimated. The values of the minimum principal stress in the plane perpendicular to the well axis determined in this study were in agreement with those determined based on extended leak-off tests (ELOT or XLOT) conducted at the same well. Therefore, it can be said that the ASR method is well suited for use in directly determining the directions of principal in situ stresses in three dimensions and in estimating the magnitude of the stresses in isotropic rocks at great depths, such as those encountered when drilling deep into a submarine seismogenic zone. 相似文献
155.
Andreas Dittrich Annette Schulte-Rentrop Michael Marek Volker Späth 《Acta Geophysica》2007,55(1):33-46
Flow in rivers and on floodplains is complex as it is affected by several interconnected factors such as topography, sediment
transport and vegetation characteristics. The resulting processes are explained by the measure “Hartheim” planned for retention
purposes at the Upper Rhine river. On the basis of existing formulas and instruments it is demonstrated that a good estimation
of the development of the measure is possible. The proposed procedure is a useful tool for estimating morphological developments
of restored river sections. 相似文献
156.
Christopher K. Shuler Henrietta Dulai Randel DeWees Marek Kirs Craig R. Glenn Aly I. El-Kadi 《Ground Water Monitoring & Remediation》2019,39(1):20-35
Wells designated as groundwater under the direct influence (GUDI) of surface water have caused an ongoing boil-water advisory afflicting the island of Tutuila, American Samoa for almost a decade. Regulatory testing at these wells found turbidity and indicator bacteria spikes correlated with heavy rainfall events. However, the mechanism of this contamination has, until now, remained unknown. Surface water may reach wells through improperly sealed well casings, or through the aquifer matrix itself. In this study, three independent surface water tracers, turbidity, indicator bacteria, and water isotopes were used to assess recharge timing and determine contamination mechanisms. Results from each method were reasonably consistent, revealing average GUDI well breakthrough times of 37 ± 21 h for turbidity, 18 to 63 h for bacteria, and 1 to 5 days for water isotopes. These times match well with estimated subsurface flow rates through highly permeable aquifer materials. In contrast, where one well casing was found to be compromised, turbidity breakthrough was observed at 3 to 4 h. These results support local management decisions and show repairing or replacing wells will likely result in continued GUDI contamination. Additionally, differences in observed rainfall response for each tracer provide insight into the recharge dynamics and subsurface flow characteristics of this and other highly conductive young-basaltic aquifers. 相似文献
157.
Jonathan Obrist-Farner Andreas Eckert Marek Locmelis James L. Crowley Byron Mota-Vidaure Emanuele Lodolo Joshua Rosenfeld Edward Duarte 《Basin Research》2020,32(6):1347-1364
The Lake Izabal Basin in Guatemala is a major pull-apart basin along the sinistral Polochic Fault, which is part of the North American and Caribbean plate boundary. The basin infill contains information about the tectonic and sedimentological processes that have imparted a significant control on its sedimentary section. The inception of the basin has been linked to the relative importance of the Polochic Fault in the tectonic history of the plate boundary; yet, its sedimentological record and its inception age have been poorly documented. This study integrates diverse datasets, including industry reports, well logs and reports, well cuttings, vintage seismic data, outcrop observations and geochronological data to constrain the initial infill and age of inception of the basin. The integrated data show that during the Oligocene–Miocene, a marine carbonate platform was established in the region which was later uplifted and eroded in the early Miocene. The fluvial–lacustrine deposits above this carbonate platform are part of the initial infill of the basin and are constrained with zircon weighted-mean 206Pb/238U ages of 12.060 ± 0.008 from a volcanic tuff ~30 m above the unconformity. Sandstone, mudstone and coal dominate the interval from 12 to 4 Ma, with an increase in conglomerate correlating to the uplift of the Mico Mountains and San Gil Hill at 4 Ma. Fault switch activity between the Polochic and Motagua faults has been hypothesized to explain total offset along the Polochic Fault and the geologic and geodetic slip rates along the two faults. The 12 Ma age determined for the initial infill of the basin confirms this hypothesis. Consequently, our study confirms that at ~12 Ma the Polochic Fault served as the main fault of the plate boundary with inferred slip rates ranging from 13 to 21 mm/yr with a strong possibility that the Polochic Fault was, at some point between 15 Ma and 7 Ma, the only active fault of the plate boundary. The results of this study show that tectonic records preserved in sediments of strike-slip basins improve the understanding of the relative significance of individual faults and the implications with respect to strain partitioning throughout its tectonic history. 相似文献
158.
159.
Effects of stratocumulus clouds on the dispersion of contaminants are studied in the nocturnal atmospheric boundary layer. The study is based on a large-eddy simulation (LES) model with a bulk parametrization of clouds. Computations include Lagrangian calculations of atmospheric dispersion of a passive tracer released from point sources at various heights above the ground. The results obtained show that the vertical diffusion is non-Gaussian and depends on the location of a source in the boundary layer. 相似文献
160.
Marek J. Sarna Ene Ergma Jelena Gerkevit-Antipova 《Monthly notices of the Royal Astronomical Society》2000,316(1):84-96
We present a detailed calculation of the evolution of low-mass (<0.25 M⊙ ) helium white dwarfs. These white dwarfs (the optical companions to binary millisecond pulsars) are formed via long-term, low-mass binary evolution. After detachment from the Roche lobe, the hot helium cores have a rather thick hydrogen layer with mass between 0.01 and 0.06 M⊙ . As a result of mixing between the core and outer envelope, the surface hydrogen content ( X surf ) is 0.5–0.35 , depending on the initial value of the heavy element Z and the initial secondary mass. We found that the majority of our computed models experience one or two hydrogen shell flashes. We found that the mass of the helium dwarf in which the hydrogen shell flash occurs depends on the chemical composition. The minimum helium white dwarf mass in which a hydrogen flash takes place is 0.213 M⊙ ( Z =0.003), 0.198 M⊙ ( Z =0.01), 0.192 M⊙ ( Z =0.02) or 0.183 M⊙ ( Z =0.03). The duration of the flashes (independent of chemical composition) is between a few ×106 and a few ×107 yr. In several flashes the white dwarf radius will increase so much that it forces the model to fill its Roche lobe again. Our calculations show that the cooling history of the helium white dwarf depends dramatically on the thickness of the hydrogen layer. We show that the transition from a cooling white dwarf with a temporarily stable hydrogen-burning shell to a cooling white dwarf in which almost all residual hydrogen is lost in a few thermal flashes (via Roche lobe overflow) occurs between 0.183 and 0.213 M⊙ (depending on the heavy element value). 相似文献