Pareto Joint Inversion of 2D Magnetotelluric and Gravity Data — Towards Practical Applications

In this paper, a Pareto inversion based global optimization approach, to obtain results of joint inversion of two types of geophysical data sets, is formulated. 2D magnetotelluric and gravity data were used for tests, but presented solution is flexible enough to be used for combination of any kind of two or more target functions, as long as misfits can be calculated and forward problems solved. To minimize dimensionality of the solution, space and introduce straightforward regularization Sharp Boundary Interface (SBI) method was applied. As a main optimization engine, Particle Swarm Optimization (PSO) was used. Synthetic examples based on a real geological model were used to test proposed approach and show its usefulness in practical applications.     

A Variscan continental collision of the West Sudetes and the Brunovistulian terrane: a contribution from structural and metamorphic record of the Stronie Formation,the Orlica-Śnieżnik Dome,SW Poland

Structural, petrological and geochronological data from marbles and mica schists combined with those from highly disputable gneisses and eclogites of the Orlica-Śnieżnik Dome (OSD), gave new insights into Variscan evolution of eastern borderland of the West Sudetes. It is shown that the Variscan tectonometamorphic evolution of the OSD began with E–W oriented subhorizontal shortening (D1 stage) related to the collision of the West Sudetes terranes and the Brunovistulian terrane. The shortening led to generally upright folding, which resulted in formation of the steep N–S trending metamorphic planar fabric S1, thickening of the lithosphere and burial of the Stronie Formation under greenschist facies conditions. As a consequence of subsequent, near-coaxial gravity-controlled vertical shortening (D2), the S1 foliation was deformed in tight recumbent folds F2. The flattening strain was associated with the progression to amphibolite-facies conditions (from ca. 510 upto ca. 620°C) and uplift from depths corresponding to 9–10 kbar to depths corresponding to 7–8 kbar. On microscale, the flattening strain is documented by rotation of the mineral fabric overgrown by syn-D2 prograde garnet porphyroblasts. The Sm–Nd Grt–WR isochron age, correlated with the D2 event yields 346.5 ± 4.4 Ma. Further deformation and progressive metamorphism led to development of the subhorizontally disposed S2 axial plane schistosity, which terminated at the metamorphic temperature peak. During retrogression but still under ductile conditions of deformation, the S2 planes were reactivated during successive top-to-the-N shear movement of the OSD (D3 stage). Due to the mutual interaction of the OSD with the adjacent terranes the shear deformations were localized within marginal parts of these units. Finally, as a result of the NE–SW and the NW–SE oriented shortenings (D4 stage and D5 stage, respectively), both the structural surfaces and metamorphic isograds were regionally folded with W(NW)-ward plunges. A synthesis of new and existing data shows an overall similarity in sequence of Variscan deformations (D1–D2–D3) in the West Sudetes borderland to that observed in the eastern flank of the Moldanubian domain.     

Aerosol removal coefficients based on 7Be, 210Pb,and 210Po radionuclides in the urban atmosphere

Journal of Atmospheric Chemistry - In this study, the aerosol removal coefficients based on 7Be, 210Pb and 210Po radionuclides in the urban air, in Lodz, Poland, were investigated over 3 years,...     

Comparison of source parameters estimated in the frequency and time domains for seismic events at the Rudna copper mine,Poland

Source parameters estimated in the frequency domain for 100 selected seismic events from the Rudna copper mine, with moment magnitude ranging from 1.4 to 3.6, were collected to study their scaling relations and to compare them with the parameters estimated in the time domain. The apparent stress and static stress drop, corrected for the limited bandwidth recording, increase slightly in a similar manner with increasing seismic moment. The ratio of apparent stress to static stress drop, a measure of radiation efficiency, is practically constant and its mean value is close to 0.1. For 37 seismic events, with moment magnitude between 1.9 and 3.4, source parameters were estimated in the time domain from relative source time functions, that displayed unilateral rupture propagation, and their rupture velocity could be estimated. It ranges from 0.23 to 0.80 of shear wave velocity and is almost independent of seismic moment. The fault length, estimated from the average source pulse width and rupture velocity, is clearly dependent on seismic moment and is smaller than the source radius estimated from the corner frequency on the average by about 25 percent. There is no correlation between the values of static stress drop estimated in the frequency and time domains, but the time domain stress drop is in general similar to that estimated in the frequency domain. The apparent stress increases with increasing rupture velocity, and the ratio of apparent stress to static stress drop seems also to depend on rupture velocity.     

Remarks on the thermal conductivity and heat flow density of the Indian Craton

The virtual or effective thermal conductivity (ETC) of the Indian subcontinental crust model is calculated from geochemical/geothermal data on the mean radiogenic heat production and on the real thermal conductivity (TC) of crystalline rocks of India. This ETC, amounting to about 3.45 W/m·K, is 1.4 time greater than the mean real TC value (about 2.5 W/m·K). This is in good agreement with the empirical relation between the surface heat flow density and the Curie depth for the Indian Craton.     

Periglacial and Fluvial Factors Controlling the Sedimentation of Pleistocene Breccia in NW Poland

Breccias were investigated on the terrace of the Toruń‐Eberswalde ice‐marginal valley at Rozwarzyn (NW Poland). Breccia layers include soft‐sediment clasts with diameters between 2 and 256 mm and soft‐sediment megaclasts with diameters from 256 mm to 7 m. The shape of the soft‐sediment clasts and megaclasts (derived from frozen sediments) in the breccia is diverse: from angular and irregular in the case of debris‐flow breccias to slightly rounded and tabular in fluvial breccias. These two types of breccias were developed during the Late Weichselian when the periglacial climate favored extensive lateral erosion by currents of frozen braided channels in the ice‐marginal valley. The dual presence of breccias of fluvial and debris‐flow origin in channel deposits is unique for Quaternary sediments. Zones of breccias existed in the channels where scours and obstacle marks related to megaclasts developed. The study of breccias shed new light on the fluvial processes in ice‐marginal valleys during the Pleistocene and can be considered as diagnostic for fluvio‐periglacial conditions.     

Gamma Emitters on Micro-Becquerel Activity Level in Air at Kraków (Poland)

The Petryanov air filters combined into half-year sets were analyzed for the presence of ⁴⁰K, ¹³⁷Cs and ²²Na by means of low-background gamma rays spectrometry. Each sample contains aerosols from more than 1 Mm³ of air. Samples were collected in ground level air at Kraków (Southern Poland) from 1996 to 2002. Activity concentrations of ⁴⁰K are almost constant with the mean of 14.7± 4.5 Bq m^–3. Activity concentrations of ¹³⁷Cs, which are on the level of single Bq m^{– 3} show exponential decrease with effective half-life time of 7.07± 0.77 years. The cosmogenic ²²Na shows a strong seasonal variation with significant different mean values activity concentration between 0.333± 0.095 Bq m^–3 and 0.137± 0.045 Bq m^–3, for summer and winter, respectively. Moreover, the activity ratio for two cosmogenic radionuclides: ²²Na and measured previously ⁷Be show also changes with statistically significant seasonal differences. The lower values were found during winters. The mechanisms which might govern this ratio are discussed. The conclusion is that transport of ²²Na during summer seems to be so much effective, that results in kind of relative depletion of stratosphere of this nuclide.     

Exploring large wood retention and deposition in contrasting river morphologies linking numerical modelling and field observations

Large wood tends to be deposited in specific geomorphic units within rivers. Nevertheless, predicting the spatial distribution of wood deposits once wood enters a river is still difficult because of the inherent complexity of its dynamics. In addition, the lack of long‐term observations or monitored sites has usually resulted in a rather incomplete understanding of the main factors controlling wood deposition under natural conditions. In this study, the deposition of large wood was investigated in the Czarny Dunajec River, Polish Carpathians, by linking numerical modelling and field observations so as to identify the main factors influencing wood retention in rivers. Results show that wood retention capacity is higher in unmanaged multi‐thread channels than in channelized, single‐thread reaches. We also identify preferential sites for wood deposition based on the probability of deposition under different flood scenarios, and observe different deposition patterns depending on the geomorphic configuration of the study reach. In addition, results indicate that wood is not always deposited in the geomorphic units with the highest roughness, except for low‐magnitude floods. We conclude that wood deposition is controlled by flood magnitude and the elevation of flooded surfaces in relation to the low‐flow water surface. In that sense, the elevation at which wood is deposited in rivers will differ between floods of different magnitude. Therefore, together with the morphology, flood magnitude represents the most significant control on wood deposition in mountain rivers wider than the height of riparian trees. Copyright © 2015 John Wiley & Sons, Ltd.