Extending the double difference location technique—improving hypocenter depth determination

Locating the seismic event hypocenter is the very first issue undertaken when studying any seismological problem. Thus, the accuracy of the obtained solution can significantly influence consecutive stages of an analysis, so there is a continuous demand for new, more efficient, and accurate location algorithms. It is well recognized that there exists no single universal location algorithm which performs equally well in all situations. Seismic activity and its spatial variability over time, seismic network geometry, and the controlled area’s geological complexity are factors influencing the performance of location algorithms. For example, in the case of mining applications, the planarity of the seismic network usually operated at the exploitation level becomes an important issue limiting the accuracy of location of the hypocenter depths. In this paper, we push forward the discussion on the performance of the newly proposed location algorithm called the extended double difference (EDD), concentrating on the reliability of source depth estimation for mining-induced seismic events. We demonstrate that the EDD algorithm very efficiently uses information originating from the nonplanarity of the seismic network, improving the hypocenter depth estimates with respect to the classical double difference technique. Methodological considerations are illustrated by real data analysis of selected events from the Rudna copper mine (Poland).     

The cryosphere and glacial permafrost as its integral component

Since Earth sciences have undertaken studies of other celestial bodies, its various fields have moved beyond the scope of study assigned to them by name. Interest in space makes it necessary to abandon research geocentrism and reverse relations when comparing the structure of the Earth with other celestial bodies. As an exceptional place in the universe, it should not be the Earth which constitutes a reference point, especially in cryospheric research, but rather the other celestial bodies of our planetary system. This approach, referred to as ??Spatial Uniformitarianism,?? is the basis for determining the place of ice in the environment and for assigning it to the lithosphere. Ice can be penetrated by frost just as other minerals and rocks, so the occurrence of permafrost may yet be attributed to glaciers and ice-caps. In the article, the occurrence of glacial permafrost has been worked out on the basis of a thermal classification of glaciers with a thorough understanding of the phenomenon. This allows us to specify permafrost??s presence beneath glaciers and ice-caps, a concept which had been needlessly vague. Further, by considering rock glaciers as a mixture of two types of rocks, and by understanding the importance of movement in their evolution, we are now closer to fruitfully determining their role in the environment, their geomorphological significance.     

Study of vertical structure of aerosol optical properties with sun photometers and ceilometer during the MACRON campaign in 2007

This paper presents the measurements of a vertical structure of aerosol optical properties performed during the MACRON (Maritime Aerosol, Clouds and Radiation Observation in Norway) campaign, which took place in July and August 2007 at ALOMAR observatory on Andøya island (69.279°N, 16.009°E, elevation 380 m a.s.l.). The mean value of the aerosol optical thickness (AOT) at 500 nm during campaign was 0.12. Significant increase of the AOT above longtime mean value was observed on 7 and 8 August 2007 when the AOT exceeded 0.4 at 500 nm. Analyses of back trajectories show the aerosol transported from over Africa and Central Europe. The aerosol extinction coefficient obtained from the synergy of ceilometer and sun photometer observations reached 0.05–0.08 km^?1 (at 1064 nm) in the dust layer. The single scattering albedo at the ALOMAR observatory decreased during the dust episode to 0.93–0.94, which indicates some absorptive aerosols in the lower PBL.     

The New Algorithm for Fast Probabilistic Hypocenter Locations

The spatial location of sources of seismic waves is one of the first tasks when transient waves from natural (uncontrolled) sources are analysed in many branches of physics, including seismology, oceanology, to name a few. It is well recognised that there is no single universal location algorithm which performs equally well in all situations. Source activity and its spatial variability in time, the geometry of recording network, the complexity and heterogeneity of wave velocity distribution are all factors influencing the performance of location algorithms. In this paper we propose a new location algorithm which exploits the reciprocity and time-inverse invariance property of the wave equation. Basing on these symmetries and using a modern finite-difference-type eikonal solver, we have developed a new very fast algorithm performing the full probabilistic (Bayesian) source location. We illustrate an efficiency of the algorithm performing an advanced error analysis for 1647 seismic events from the Rudna copper mine operating in southwestern Poland.     

Microstructure measures and the minimum size of a representative volume element: 2D numerical study

In the paper, a numerical study of the size of a representative volume element (RVE) for both the heat flow as well as the linear elasticity problems is presented. A particular two-phase random microstructure is studied and the method is applied to the digital image of reconstructed 2D realization of random media. The minimum size of RVE is determined by the investigation of the convergence of apparent properties as the size of RVE is increasing. Then, two estimates of the minimum RVE size are proposed and it is shown that the estimates are in a good agreement with the results determined by the investigation of the convergence of apparent properties. The minimum size of RVE can be successfully predicted based only on the microstructure morphology. The statistical measures used in this work are: the two-point probability and the linealpath functions.     

New marine reptile fossils from the Late Jurassic of Poland with implications for vertebrate faunas palaeobiogeography

A new marine vertebrate assemblage from the Late Jurassic (late Kimmeridgian) at Krzy?anowice near I??a in the NE margin of the Holy Cross Mountains in Poland is described. This new locality is rich in fossils of coastal and pelagic reptiles. The most frequent fossils are plesiochelyid turtle shell fragments and pliosaurid skull bones and teeth. The Krzy?anowice vertebrate assemblage is similar to the Late Jurassic Boreal/Sub-Boreal localities of the Kimmeridge Clay in Great Britain and Svalbard Archipelago in the Arctic, in the presence of pliosaurids and long-necked plesiosaurids. However, plesiochelyid turtles and crocodylomorphs are similar to those from the Mediterranean/Sub-Mediterranean sites of the northern border of the Tethys Ocean, as, for example, in the Swiss Jura Mountains and Southern Germany. This unique composition of the Krzy?anowice vertebrate fauna demonstrates that, during the Late Jurassic this new locality was located in the transitional palaeobiogeographic line referred to in this paper as the “Matyja-Wierzbowski Line”. The new palaeobiogeographical reconstructions of Late Jurassic of Europe are based on the composition of the Krzy?anowice locality and other sites with similar turtle-pliosaurid faunas which formed a long-term, stable ecological sympatry in marine ecosystems of the European Archipelago.     

Response of unconfined turbidity current to deep‐water fold and thrust belt topography: Orthogonal incidence on solitary and segmented folds

Sea‐floor topography of deep‐water folds is widely considered to have a major impact on turbidity currents and their depositional systems, but understanding the flow response to such features was limited mainly to conceptual notions inspired by small‐scale laboratory experiments. High‐resolution three‐dimensional numerical experiments can compensate for the lack of natural‐scale flow observations. The present study combines numerical modelling of thrusts with fault‐propagation folds by Trishear3D software with computational fluid dynamics simulations of a natural‐scale unconfined turbidity current by MassFlow‐3D? software. The study reveals the hydraulic and depositional responses of a turbidity current (ca 50 m thick) to typical topographic features that it might encounter in an orthogonal incidence on a sea‐floor deep‐water fold and thrust belt. The supercritical current (ca 10 m sec^?1) decelerated and thickened due to the hydraulic jump on the fold backlimb counter‐slope, where a reverse overflow formed through current self‐reflection and a reverse underflow was issued by backward squeezing of a dense near‐bed sediment load. The reverse flows were re‐feeding sediment to the parental current, reducing its waning rate and extending its runout. The low‐efficiency current, carrying sand and silt, outran a downslope distance of >17 km with only modest deposition (<0·2 m) beyond the fold. Most of the flow volume diverted sideways along the backlimb to surround the fold and spread further downslope, with some overspill across the fold and another hydraulic jump at the forelimb toe. In the case of a segmented fold, a large part of the flow went downslope through the segment boundary. Preferential deposition (0·2 to 1·8 m) occurred on the fold backlimb and directly upslope, and on the forelimb slope in the case of a smaller fold. The spatial patterns of sand entrapment revealed by the study may serve as guidelines for assessing the influence of substrate folds on turbiditic sedimentation in a basin.     

Estimating Flood Quantiles on the Basis of Multi-Event Rainfall Simulation — Case Study

This paper presents an approach to estimating the probability distribution of annual discharges Q based on rainfall-runoff modelling using multiple rainfall events. The approach is based on the prior knowledge about the probability distribution of annual maximum daily totals of rainfall P in a natural catchment, random disaggregation of the totals into hourly values, and rainfall-runoff modelling. The presented Multi-Event Simulation of Extreme Flood method (MESEF) combines design event method based on single-rainfall event modelling, and continuous simulation method used for estimating the maximum discharges of a given exceedance probability using rainfall-runoff models. In the paper, the flood quantiles were estimated using the MESEF method, and then compared to the flood quantiles estimated using classical statistical method based on observed data.