Holocene history and environmental reconstruction of a Hercynian mire and surrounding mountain landscape based on multiple proxies     

Lydie Dudová  Petra Hájková  Věra Opravilová  Michal Hájek 《Quaternary Research》2014

We discovered the first peat section covering the entire Holocene in the Hrubý Jeseník Mountains, representing an island of unique alpine vegetation whose history may display transitional features between the Hercynian and Carpathian regions. We analysed pollen, plant macrofossils (more abundant in bottom layers), testate amoebae (more abundant in upper layers), peat stratigraphy and chemistry. We found that the landscape development indeed differed from other Hercynian mountains located westward. This is represented by Pinus cembra and Larix during the Pleistocene/Holocene transition, the early expansion of spruce around 10,450 cal yr BP, and survival of Larix during the climatic optimum. The early Holocene climatic fluctuations are traced in our profile by species compositions of both the mire and surrounding forests. The mire started to develop as a calcium-rich percolation fen with some species recently considered to be postglacial relicts (Meesia triquetra, Betula nana), shifted into ombrotrophy around 7450 cal yr BP by autogenic succession and changed into a pauperised, nutrient-enriched spruce woodland due to modern forestry activities. We therefore concluded that its recent vegetation is not a product of natural processes. From a methodological viewpoint we demonstrated how using multiple biotic proxies and extensive training sets in transfer functions may overcome taphonomic problems.  相似文献   

Automated calibration of advanced soil constitutive models. Part II: hypoplastic clay and modified Cam-Clay     

Kadlíček  Tomáš  Janda  Tomáš  Šejnoha  Michal  Mašín  David  Najser  Jan  Beneš  Štěpán 《Acta Geotechnica》2022,17(8):3439-3462

This paper introduces an automated deterministic method for the calibration of the Modified Cam-Clay and hypoplastic clay model. The calibration is structured in a hierarchical order established based on the apriori sensitivity study performed. The proposed method favours the clear physical meaning of the model parameters to a complete optimization of the objective error function. The method requires only basic laboratory experiments and it is currently implemented in the free-to-use online application called ExCalibre.

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Urban field classification by “local climate zones” in a medium-sized Central European city: the case of Olomouc (Czech Republic)     

Michal Lehnert  Jan Geletič  Jan Husák  Miroslav Vysoudil 《Theoretical and Applied Climatology》2015,122(3-4):531-541

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Variscan deformation,microstructural zonation and extensional exhumation of the Moravian Cadomian basement     

Michal Lobkowicz  Karel Schulmann  Radek Melka 《Geodinamica Acta》2013,26(2-3):119-137

Abstract

The Cadomian Dyje Batholith, in the foot–wall of the Variscan Moravian nappe pile, has been involved in Variscan ductile deformation. The Cadomian Brunovistulian rocks were obliquely underthrusted during Carboniferous dextral transpression.

Strain intensity is inversely proportional to the distance from the contact of the Variscan thrust front. The microstructures of deformed granodiorites and quartz–diorites show a characteristic zonality marked by relatively high temperature flow in the west (550–580 °C) characterized by dynamic recrystallization of feldspars and grain boundary migration recrystallization of quartz. The size of quartz grains decreases with decreasing strain towards the east. At the easternmost part of the autochthonous Dyje massif, fracturing of feldspar and subgrain rotation recrystallization of quartz predominate. Flow stress estimates calculated from recrystallized quartz grain size show a regional increase of stress intensity from the highly strained margin towards the less deformed core of the Dyje massif. This microstructural zonation is oblique with respect to the major thrust boundary and corresponds roughly to metamorphic isogrades. The microstructural zonation reflects underthrusting of the Brunovistulian domain below the Moldanubian nappe.

The main ductile tectonic event D₁ is followed by a retrogressive brittle–ductile and brittle deformation D₂. D₂ results in the development of shear zones and faults superimposed on the D₁ mylonite fabric. D₂ is related to extension oblique to the D₁ fabric, associated with detachment and the westward movement of the Moravian nappes. © Elsevier, Paris  相似文献   

Integral transformations of deflections of the vertical onto satellite-to-satellite tracking and gradiometric data     

Michal Šprlák  Pavel Novák 《Journal of Geodesy》2014,88(7):643-657

With the advent of geodetic satellite missions mapping almost globally the Earth’s gravitational field, new methods and theoretical approaches have been developed and investigated to fully exploit the potential of their new observables. Besides estimating values of numerical coefficients in harmonic series of the gravitational potential, new applications emerged such as data validation and combination. In this contribution, new integral transformations are presented which transform principal components of the terrestrial deflection of the vertical onto disturbing satellite-to-satellite tracking and gradiometric data at altitude. Using spherical approximation, necessary integral kernel functions are derived in both spectral and closed forms. The behaviour of isotropic kernel functions is studied and the new integral transformations are tested in a closed-loop simulation using synthetic terrestrial and satellite data synthesized from a global gravitational model. New integral transformations can be used for data validation and combination purposes.  相似文献   

Model Fusion and Joint Inversion   总被引：1，自引：1，他引：0  

Eldad Haber  Michal Holtzman Gazit 《Surveys in Geophysics》2013,34(5):675-695

Inverse problems are inherently non-unique, and regularization is needed to obtain stable and reasonable solutions. The regularization adds information to the problem and determines which solution, out of the infinitely many, is obtained. In this paper, we review and discuss the case when a priori information exists in the form of either known structure or in the form of another inverse problem for a different property. The challenge is to include such information in the inversion process. To use existing known structure, we review the concept of model fusion, where we build a regularization functional that fuses the inverted model to a known one. The fusion is achieved by four different techniques. Joint inversion of two data sets is achieved by using iterative data fusion. The paper discusses four different methods for joint inversion. We discuss the use of correspondence maps or the petrophysics of the rocks, as well as structure. In particular, we suggest to further stabilize the well-known gradient cross product and suggest a new technique, Joint Total Variation, to solve the problem. The Joint Total Variation is a convex functional for joint inversion and, as such, has favorable optimization properties. We experiment with the techniques on the DC resistivity problem and the borehole tomography and show how model fusion and joint inversion can significantly improve over existing techniques.  相似文献   

泰国近岸古环境Toarcian-Aalenian期风暴沉积初探     

Assanee MEESOOK  Michal KROBICKI 《地球学报》2012,33(S1):40-40

Jurassic deposits of the Malayan Peninsula (Thailand) are stratigraphically limited to Toarcian and Aalenian only (Meesook & Sha, 2010, and literature cited therein). These are represented by wide spectrum of both clastic and carbonate rocks with full develop-ment of transitional ones. In the middle part of penin-sula (vicinity of Krabi) distribution of Jurassic facies suggest occurrence of full marine palaeoenvironments in NE part of it with gentle transition by lagoonal (brackish?) and tidal environments up to terrestrial ones in the SW part of peninsula. Sections studied, close to Thung Song city, are represented by 20 m thick sequence of thin-bedded limestones and marls of the Khlong Min Formation, most probably lagoonal palaeoenvironments (transitional = restricted ma-rine-brackish), indicated by specific benthic fauna dominated by different kind of ethological group of bivalves – infaunal, epifaunal and encrusted (epibion-tic) species like Protocardia, Praemytilus, Modiolus, Myrene, and Actinostreon. Very characteristic is a lack of full marine, stenohaline, other invertebrates – brachiopods, crinoids, echinoids etc.  相似文献   

SfM-MVS Photogrammetry for Splash Erosion Monitoring under Natural Rainfall     

Tomáš Laburda  Josef Krása  David Zumr  Jan Devátý  Michal Vrána  Nives Zambon  Lisbeth Lolk Johannsen  Andreas Klik  Peter Strauss  Tomáš Dostál 《地球表面变化过程与地形》2021,46(5):1067-1082

An understanding of splash erosion is the basis to describe the impact of rain characteristics on soil disturbance. In typical splash cup experiments, splashed soil is collected, filtered, and weighed. As a way to collect additional data, our experiments have been supplemented by a photogrammetric approach. A total of three soils were tested across three sites, one in the Czech Republic and two in Austria, all equipped with rain gauges and disdrometers to measure rainfall parameters. The structure from motion multiview stereo (SfM-MVS) photogrammetric method was used to measure the raindrops impact on the soil surface. The images were processed using Agisoft PhotoScan, resulting in orthophotos and digital elevation models (DEMs) with a resolution of 0.1 mm/pix. The surface statistics included the mean surface height (whose standard deviation was used as a measure of surface roughness), slope, and other parameters. These parameters were evaluated depending on soil texture and rainfall parameters. The results show a linear correlation between consolidation and splash erosion with a coefficient of determination (R²) of approximately 0.65 for all three soils. When comparing the change in soil volume with rainfall parameters, the best correlation was found with the maximum 30-minintensity (I₃₀), resulting in R² values of 0.48 (soil A, silt loam, 26% clay), 0.59 (soil B, silt loam, 18% clay), and 0.68 (soil C, loamy sand, 12% clay). The initial increase in the sample volume for the lowest splashed mass corresponds with the increase in the clay content of each of the soils. Soil A swells the most. Soil B swells less. Soil C does not swell at all and consolidates the most. We derived the relationship between the photogrammetrically measured change in surface height and the splash erosion (measured by weight) by accounting for the effect of the clay content.  相似文献   

Analytical expression for fresnel volumes and interface fresnel zones of seismic body waves. Part 1: Direct and unconverted reflected waves     

Michal Kvasnička  Vlastislav Červený 《Studia Geophysica et Geodaetica》1996,40(2):136-155

Summary Fresnel volumes, plane-sectional Fresnel zones and interface Fresnel zones of direct and unconverted reflected waves are studied. Exact analytical expressions for various parameters of Fresnel volumes and Fresnel zones are derived and discussed. Among others, these expressions are related to semi-axes of Fresnel zones, to overshooting and penetration distances, and to the off-ray shifts of Fresnel zones.  相似文献   

Using external tropospheric corrections to improve GNSS positioning of hot-air balloon     

Pavel Vaclavovic  Jan Dousa  Michal Elias  Jakub Kostelecky 《GPS Solutions》2017,21(4):1479-1489

High accurate global navigation satellite systems (GNSS) require to correct a signal delay caused by the troposphere. The delay can be estimated along with other unknowns or introduced from external models. We assess the impact of the recently developed augmentation tropospheric model on real-time kinematic precise point positioning (PPP). The model is based on numerical weather forecast and thus reflects the actual state of weather conditions. Using the G-Nut/Geb software, we processed GNSS and meteorological data collected during the experiment using a hot-air balloon flying up to an altitude of 2000 m. We studied the impacts of random walk noise setting of zenith total delay (ZTD) on estimated parameters and the mutual correlations, the use of external tropospheric corrections, the use of data from a single or dual GNSS constellation and the use of Kalman filter and backward smoothing processing methods. We observed a significant negative correlation of the estimated rover height and ZTD which depends on constraining ZTD estimates. Such correlation caused a degraded performance of both parameters when estimated simultaneously, in particular for a single GNSS constellation. The impact of ZTD constraining reached up to 50-cm differences in the rover height. Introducing external tropospheric corrections improved the PPP solution regarding: (1) shortened convergence, (2) better overall robustness, particularly, in case of degraded satellite geometry, (3) less adjusted parameters with lower correlations. The numerical weather model-driven PPP resulted in 9–12- and 5–6-cm uncertainties in the rover altitude using the Kalman filter and the backward smoothing, respectively. Compared to standard PPP, it indicates better performance by a factor of 1–2 depending on the availability of GNSS constellations, the troposphere constraining and the processing strategy.  相似文献