Optimal design of a regional seismological network for the Arab countries

The Arab countries cover a large portion of the African and Arabian plates, a region characterized by seismic activity along complex continental collision zones, active seafloor spreading, rifting, and intraplate earthquakes. Establishing a standardized regional seismic network in these countries, then, is of great importance. Considerable effort of some Arab countries and UNESCO under project PAMERAR is under way to achieve this goal. A design for the spatial distribution of a regional seismic network in the area, based on a D-optimal planning criterion, is proposed in this paper. The method, which involves optimizing the geographical locations of stations, is based on the probability of earthquake occurrence at a given point in the seismic region, travel times of seismic waves, and minimization of the ellipsoid volume of earthquake location errors.     

A Lower Palaeozoic shallow water sequence in the eastern European Variscides (SW Poland): provenance and depositional history

The Gackowa Formation of inferred Cambrian —Ordovician age is part of the metamorphosed pre-Variscan basement of the southern Kaczawa Mountains of the Sudetes region, south-west Poland. Previously variously interpreted as lavas, tuffs and sandstones, it is shown to consist of about 200 m of originally well-sorted siliclastic sedimentary rocks within a sequence of predominantly mafic volcanic rocks. Four facies have been distinguished based on relict sedimentary structures and textures and these suggest that deposition took place on a storm-dominated shelf, mostly above the wave base. The petrography, detrital zircon morphologies and geochemistry suggest affinity with, and derivation in large part from, acid volcanic rocks at a comparable stratigraphic position in a separate tectonostratigraphic unit to the south. The Gackowa Formation and its acid volcanic source rocks have a clear continental geochemical signature, in contrast with the mantle-derived basic/bimodal volcanic rocks below and above; it is suggested that the parent acid magma originated by crustal melting during the ascent of these mantle-derived magmas. A continental crust setting is inferred for the deposition of the Gackowa Formation sandstones, thus suggesting a continental setting for the associated within-plate basalts. The entire volcanic/sedimentary succession resembles elements of the Lower Palaeozoic of Germany, and all may have formed in an initial rift setting during Late Precambrian to Ordovician times.     

Liapunov instability of the hypoplastic model for soils

The hypoplastic constitutive model is known for its numerous application to the problems of soil mechanics and also for its excessive ratcheting. The paper shows that this deficiency can be interpreted as Liapunov instability in dynamic case. This is demonstrated with a simple one-dimensional swinger. Infinitesimally small as well as finite oscillations are analytically examined and the variability of stiffness upon a single cycle is considered. Several methods to circumvent the problem of ratcheting are discussed: implementation of ‘elastic’ range by means of so-called intergranular strain, usage of overlay modelling with parallel coupling of hypoplastic materials as originally proposed by Valanis in his endochronic theory and a special coupling of hypoplastic models based on comparison of partial stiffnesses.     

Propagation of Pulses in Viscoelastic Media

— It is shown that in hereditary models of media with regular convolution kernels discontinuities propagate with the wavefronts. A singularity always remains sharp and propagates with the wavefront. Oscillatory signals lag behind the wavefronts and are preceded by distortions. In media with singular memory, signals lag behind wavefronts. Singular signals are immediately smoothed and spread out.     

Three-Dimensional Geographically Weighted Inverse Regression (3GWR) Model for Satellite Derived Bathymetry Using Sentinel-2 Observations

Current trends of development of satellite derived bathymetry (SDB) models rely on applying calibration techniques including analytical approaches, neuro-fuzzy systems, regression optimization and others. In most of the cases, the SDB models are calibrated and verified for test sites, that provide favorable conditions for the remote derivation of bathymetry such as high water clarity, homogenous bottom type, low amount of sediment in the water and other factors. In this paper, a novel 3-dimensional geographical weighted regression (3GWR) SDB technique is presented, it binds together methods already presented in other studies, the geographically weighted local regression (GWR) model, with depth dependent inverse optimization. The proposed SDB model was calibrated and verified on a relatively difficult test site of the South Baltic near-shore areas with the use of multispectral observations acquired by a recently launched Sentinel-2 satellite observation system. By conducted experiments, it was shown that the proposed SDB model is capable of obtaining satisfactory results of RMSE ranging from 0.88 to 1.23[m] depending on the observation and can derive bathymetry for depths up to 12m. It was also shown, that the proposed approach may be used operationally, for instance, in the continuous assessment of temporal bathymetry changes, for areas important in the context of ensuring local maritime safety.     

Charge States of Krypton and Xenon in the Solar Wind

We calculate charge state distributions of Kr and Xe in a model for two different types of solar wind using the effective ionization and recombination rates provided from the OPEN_ADAS data base. The charge states of heavy elements in the solar wind are essential for estimating the efficiency of Coulomb drag in the inner corona. We find that xenon ions experience particularly low Coulomb drag from protons in the inner corona, comparable to the notoriously weak drag of protons on helium ions. It has been found long ago that helium in the solar wind can be strongly depleted near interplanetary current sheets, whereas coronal mass ejecta are sometimes strongly enriched in helium. We argue that if the extraordinary variability of the helium abundance in the solar wind is due to inefficient Coulomb drag, the xenon abundance must vary strongly. In fact, a secular decrease of the solar wind xenon abundance relative to the other heavier noble gases (Ne, Ar, Kr) has been postulated based on a comparison of noble gases in recently irradiated and ancient samples of ilmenite in the lunar regolith. We conclude that decreasing solar activity and decreasing frequency of coronal mass ejections over the solar lifetime might be responsible for a secularly decreasing abundance of xenon in the solar wind.     

Hydric potential of the river basin: Prądnik,Polish Highlands

Human society deals with floods, drought and water pollution. Facing those problems, the question how to prevent or at least to minimalize the adverse effects of water-related issues is asked of the landscape managers. In this way, any help given to landscape managers seems to be an additional useful tool. Within this paper, an approach leading to mitigation of water-related problems is presented that relates the retention of precipitation and the use of ecosystems as a tool for improving the quality, quantity of water resources and availability throughout the region. One approach is the determination of the landscape’s hydric potential (LHP). This study examines one example of using this method within the conditions of Poland. The results of the research show that national data are entirely appropriate for implementation of the LHP method. Further, this approach revealed the classes of the hydric potential of the Pr?dnik river basin which was selected as the experimental territory. LHP results reflect the ecosystem attributes of the model river basin; areas of average LHP cover 63.26%, areas of high and limited hydric potential cover approximately 18.3% each. The spatial distribution of LHP means the results of this study provide a baseline for management of the river basin.     

Refinement of the Hardening Soil model within the small strain range

Acta Geotechnica - The popularity of the elasto-plastic Hardening Soil (HS) model is based on simple parameter identification from standard testing and empirical formulas. The HS model is...