Shallow-generated damage within non-planar strike-slip fault zones: role of sedimentary rocks in slip accommodation,SW Holy Cross Mountains,Poland

International Journal of Earth Sciences - We investigated exhumed damage zones of dextral strike-slip faults dissecting the south-western part of the Mesozoic cover of the Late Palaeozoic Holy...     

Arbitrary order numerical solutions conserving the Jacobi constant in the motion near the equilibrium points

In the paper a modification of the polynomial extrapolation for solving the problem of motion nearby the equilibrium points is presented. It appears that the modification yields a better approximation of the exact solution than the convential polynomial extrapolation and other methods. Moreover, the modification conserves the Jacobi constant of motion. Computer examples for orbits nearby the equilibrium points of the Sun-Jupiter system are given.     

Diffraction by plane sectors and polygons

Time-domain theory of edge and edge-and-vertex diffraction is briefly reviewed and its applications to diffraction by polygons, pyramids and curved reflectors are discussed. The time-domain theory is based on canonical functions defined in terms of inverse trigonometric and algebraic functions, which ensures its numerical efficiency.     

An algorithm for the optimum distribution of a regional seismic network—I

Summary An algorithm for the optimum distribution of any number of regional seismic stations is formulated. The information needed from a given region is the relative distribution of seismic intensity and the travel times of seismic waves used in earthquake location procedure. To define the optimum distribution of a regional network, some generalization of D-planning (minimization of the ellipsoid volume of earthquake location errors) was applied. The D-optimum criterion is generalized for a case where equations describing the process are nonlinear and when the most probable values of the sought parameters (origin time and earthquake focus coordinates) are not known.As an example of the algorithm application, the optimum distribution of seismic stations in the central district of the Lublin Coal Basin in Poland is given.     

An estimate of probabilistic seismic hazard for five cities in Greece by using the parametric-historic procedure

A probabilistic procedure was applied to assess seismic hazard for the sites of five Greek cities (Athens, Heraklion, Patras, Thessaloniki and Volos) using peak ground acceleration as the hazard parameter. The methodology allows the use of either historical or instrumental data, or a combination of both. It has been developed specifically for the estimation of seismic hazard at a given site and does not require any specification of seismic sources or/and seismic zones. A new relation for the attenuation of peak ground acceleration was employed for the shallow seismicity in Greece. The computations involved the area- and site-specific parts. When assessing magnitude recurrence for the areas surrounding the five cities, the maximum magnitude, m_max, was estimated using a recently derived equation. The site-specific results were expressed as probabilities that a given peak ground acceleration value will be exceeded at least once during a time interval of 1, 50 and 100 years at the sites of the cities. They were based on the maximum peak ground acceleration values computed by assuming the occurrence of the strongest possible earthquake (of magnitude m_max) at a very short distance from the site and using the mean value obtained with the help of the attenuation law. This gave 0.24 g for Athens, 0.53 g for Heraklion (shallow) and 0.39 g Heraklion (intermediate-depth seismicity), 0.30 g for Patras, 0.35 g for Thessaloniki and 0.30 g for Volos. In addition, the probabilities of exceedance of the estimated maximum peak ground acceleration values were calculated for the sites. The standard deviation of the new Greek attenuation law demonstrates the uncertainty and large variation of predicted peak ground acceleration values.     

Point-to-curve ray tracing in complicated geological models1

Boundary-value problems (BVPs) for seismic rays generally have multiple solutions. In practical applications the number of solutions can be large. The algorithm presented below solves a one-parameter family of BVPs and makes it easy to obtain all the solutions of a BVP.     

Estimation of earthquake hazard parameters for incomplete and uncertain data files

The maximum likelihood estimation of earthquake hazard parameters (maximum regional magnitudem _max, activity rate λ, and theb parameter in the Gutenberg-Richter distribution) is extended to the cases of incomplete and uncertain data. The method accepts mixed data containing only large (extreme) events and a variable quality of complete data with different threshold magnitude values. Uncertainty of earthquake magnitude is specified by two values, the lower and upper magnitude limits. It is assumed that such an interval contains the real unknown magnitude. The proposed approach allows the combination of different quality catalog parts, e.g. those where the assignment of magnitude is questionable and those with magnitudes precisely determined. As an illustration of the method, the seismic hazard analysis for western Norway and adjacent sea area (4–8°E, 58–64°N) is presented on the basis of the strongest earthquakes felt during the period 1831–1889 and three complete catalog parts, covering the period 1890–1987.     

Effects of an ultrasonic field on the flotation selectivity of barite from a barite-fluorite-quartz ore

The influence of an ultrasonic field frequency of 22 kHz and intensity of 0.5 W/cm² has been examined on the flotation of barite, fluorite and quartz as well as on their ability to adsorb dodecyl- and cetylsulphates. The tests affected the flotation of pure minerals in a Hallimond tube as well as the flotation of a natural barite-fluorite ore. It has been found that ultrasonic pretreatment of minerals causes an increase in the flotation rate of barite and a decrease in the flotation rate of fluorite. Ultrasonic pretreatment of the natural barite-fluorite ore before its flotation is the most advantageous. In this case it is possible to obtain concentrates of barite composed of a low amount of CaF₂. This may be explained by the different effects of ultrasonic vibrations on barite and fluorite which cause some improvement of the selectivity of their flotation separation.For a full explanation of these results the effects of ultrasonic pretreatment of the minerals on their adsorption properties and surface topography have been investigated, as well as the direct influence of ultrasound on the adsorption process.     

Response of the ionosphere to the Baltic Sea earthquake of 21 September 2004

GPS observations of the European permanent network were used to identify seismo-ionospheric precursors of Baltic Sea earthquake of 21 September 2004. It is a very rare event for this region of Europe (magnitude of about 5.0). This value is the threshold for the occurrence of seismic effects in the ionosphere. In total electron content (TEC) data over the region of the earthquake, a specific ionospheric anomaly appeared one day before the earthquake was detected. The ionospheric variability had a positive sign with an enhancement of about 4–5 TECU (1 TECU = 10¹⁶ electrons/m²) relative to the non-disturbed state of the ionosphere. The anomaly had a duration of 4–5 hours in the day time. The special size of this anomaly was about 1000 km. The characteristic parameters of the anomaly show that it can be associated with ionospheric precursors of an earthquake.     

Features of the ionosphere behavior before the Kythira 2006 earthquake

In this paper we present specific features of TEC (total electron content of the ionosphere) behavior as possible precursors of Kythira (Southern Greece) earthquake of January 8, 2006 (M6.8). For this purpose, we used both the TEC data of GPS-IGS stations nearest to the epicenter, and TEC maps over Europe. The favorable circumstance for this analysis was the quiet geomagnetic situation during the period prior to the earthquake. One day before the earthquake, a characteristic anomaly was found out as the day-time significant increase of TEC at the nearest stations, up to the value of 50% relative to the background condition. To estimate the spatial dimensions of seismo-ionospheric anomaly, the differential mapping method was used. The ionosphere modification as a cloud-like increase of electron concentration situated in the immediate vicinity of the forthcoming earthquake epicenter has been revealed. The amplitude of modification reached the value of 50% relative to the non-disturbed condition and was in existence from 10:00 till 22:00 UT. The area of significant TEC enhancement had a size of about 4000 km in longitude and 1500 km in latitude.