Stochastic modeling of seismic surface rotations

In this paper, a stochastic analysis of surface rotations during earthquakes is presented. The surface motion is modeled by a spacetime random field. A method to obtain rotation based on direct differentiation of the random field is proposed with a reference to a second method based on wave decomposition. The first method leads to a spectral density of surface rotations in terms of point translation spectral density, coherence function and apparent waves velocity, while the second method formulates the rotational spectrum in terms of point translation spectral density and wave parameters. The advantages and disadvantages of both methods are discussed in detail.On leave from: Faculty of Civil Engineering, Technical University, ul. Katowicka 48, 45–951 Opole Poland.     

Statistics of Scalar Fields in the Atmospheric Boundary Layer Based on Large-eddy Simulations. Part 1: Free Convection

Convection in a quasi-steady, cloud-free, shear-free atmospheric boundary layer is investigated based on a large-eddy simulation model. The performed tests indicate that the characteristic (peak) values of statistical moments at the top of the mixed layer are proportional to the interfacial scales (from gradients of scalars in the interfacial layer). Based on this finding a parameterization is proposed for profiles of scalar variances. The parameterization employs two, semi-empirical similarity functions F_m(z/z_i) andF_i(z/z_i), multiplied by a combination of the mixed-layer scales and the interfacial scales.     

Improving Non-local Parameterization of the Convective Boundary Layer

We propose improvements in the “non-local” parameterization scheme of the convective boundary layer. The countergradient terms for components of the momentum fluxes are introduced in a form analogous to those for other scalars. The scheme also includes explicit expressions for entrainment fluxes of momentum, temperature, and humidity. A simplified procedure for calculating the boundary-layer height is proposed, consisting of two steps: the evaluation of the convection level, followed by the assessment of the depth of the interfacial layer.     

Distribution of time lags between successive petroleum exploration activities

Four time lags are studied: (1) drilling activity behind seismic activity; (2) oil and gas reserves discovered behind drilling activity; (3) oil and gas production behind reserves discovered; and (4) oil and gas production behind drilling activity. A ridge regression method is used to estimate the distributions of these lags for 50 countries and regions active in petroleum exploration. A complete review of obtained results is given as well as an interpretation of estimated models and failed ridge regressions. Five types of distributions have been found: decreasing monotonically, unimodal, bimodal, uniform, and increasing monotonically. The distributions allow estimating the capital freezing in the exploration process and assessing the resulting policy made by all companies active in a country. For example, the actual exploration history in Poland is analyzed with the use of distributed time-lag approach and net present-value concept. An overinvestment in drilling in comparison with petroleum infrastructure has been stated on the basis of the excessive lagging of production behind drilling activity. A direction of further lag studies is also suggested.     

Rockburst induced ground motion—a comparative study

While rockbursts from underground copper mining in Western Poland normally produce surface peak ground accelerations (PGA) and velocities of 0.05–0.1 g and 1–3 cm/s, occasionally these peak motions may exceed 0.15 g and 10 cm/s, respectively. These larger motions are of considerable concern and an investigation has been undertaken to define the nature of these larger induced ground motions. This paper compares these rockburst motions with low intensity earthquakes. Various strong motion parameters such as PGA, peak ground velocity (PGV) and displacements as well as strong motion duration, Arias intensity, Fourier and response spectra are compared with those from earthquakes. It is concluded that although short duration is the most obvious parameter that differentiates rockbursts from earthquakes, in fact their high dominant frequencies, which result in high PGA/PGV ratios differentiate them the most. Two types of rockburst-induced ground motions are indicated in this paper: typical—with 3–6 months return period and characteristic, high frequency content—as well as rare events similar to shallow, low intensity earthquakes.     

On the vertical distribution of passive species in the atmospheric boundary layer

A similarity theory presented by Sorbjan (1986) is extended by taking into consideration diffusion of passive species (e.g., specific humidity) in the atmospheric boundary layer. Theoretical similarity functions are obtained for the convective and stable-continuous regimes.On leave from Institute of Environmental Engineering, Warsaw Technical University, Poland.     

Statistics of shallow convection on Mars based on large-eddy simulations. Part 2: effects of wind shear

Effects of wind on quasi-steady, shallow convection in the Martian boundary layer are studied using a large-eddy simulation model. Convection in the model is generated by the radiative flux divergence and the strength of the surface heat flux, which do not vary in time. The resulting convective boundary layer exhibits transient, irregular, horizontal cellular structures, transported by wind, and a lack of well-pronounced regular horizontal rolls, observed for analogous conditions on Earth. The dimensionless statistics of turbulence are generally similar to those generated in the windless conditions, and depend on the ratio F, defined in terms of the integrated radiative and turbulent heating rates in the boundary layer. The simulations show that variations of the radiative heating influence the temperature statistics, while their effects on the wind velocity are relatively small. The horizontal velocity variances do not show a strong dependence on parameter F, in contrast with the vertical velocity variances, which are strongly dependent on F.     

Fe–S mineralization in the Jurassic biogenic remains (Częstochowa,Poland)

Various Fe–S minerals of the mackinawite–greigite–pyrite association, ubiquitous in biogenic remains from Jurassic mudstones, have been described in detail in an SEM–EDS study. Two diagenetic stages of Fe sulphide formation and preservation in the Jurassic organic skeletons are identified. In the first stage, pyrite formed as euhedra and framboids shortly after deposition, mainly in the interiors of the skeletons which still contained labile organic matter. The second stage of iron sulphide formation was related to the later stages of diagenesis, when the influence of the surrounding sediment was more dominant, although some organic matter was still present in the biogenic skeletons. A Fe-rich carbonate–aluminosilicate cement was then introduced between the earliest iron sulphides and later subsequently sulphidized, to form a metastable iron monosulphide of mackinawite composition and then greigite.     

Damage reconstruction of 3D frames using genetic algorithms with Levenberg–Marquardt local search

A damage detection method based on harmonic structural vibrations has been applied to reconstruct typical damage patterns of reinforced concrete beams and frames vibrating in three dimensions. It has been shown that comparison of harmonic vibrations of damaged and intact structures makes it possible to formulate optimization criterion which can be solved effectively for large number of unknowns. The application of combined genetic algorithms and Levenberg–Marquardt local search enabled to reconstruct vectors of distinct stiffness distributions containing up to 32 elements with stiffness loss as low as 5% and with accuracy of 1%. To test the algorithm in more realistic environment of practical data acquisition, measuring noise with various levels has been added to the analyzed signal. Such a method of damage detection can be quite effective during post-earthquake assessment of civil engineering structures or if one wants to control the stiffness loss of a reinforced concrete structure after it was accidentally overloaded.