Strain release in relation to focal depth

Summary The world-wide strain release in relation to focal depth has been calculated for all shocks with magnitude 7 and over for the interval 1918–1952. The strain exhibits a strong maximum in the uppermost 75 km of the earth; it decreases exponentially with depth between 75 and 400 km, with an unimportant minimum corresponding to the asthenosphere low-velocity layer and another minimum at 275 km; after a pronounced minimum between 400 and 475 km it increases again approximately exponentially between 475 and 650 km, after which it drops rapidly to zero. The shape of the strain-depth curve is interpreted in terms of the physical conditions and the intensity of strain accumulation. In particular, the increase between 475 and 650 km is ascribed to a combined effect of temperature and pressure variation with depth with related phase changes and possible changes in composition. The depth curve for the number of shocks is nearly parallel to the strain-depth curve, and the average strain per earthquake shows only an insignificant decrease with depth.

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Zusammenfassung Es wird die Tiefenabhängigkeit der Deformationsauslösung in allen Erdbeben mit Magnitude 7 und darüber, im Zeitraum 1918–1952 untersucht. Die Deformationsauslösung hat ein ausgesprochenes Maximum in den obersten 75 km. Sie nimmt im Tiefenbereich zwischen 75 und 400 km exponential mit der Tiefe ab, wobei sich ein Minimum, das der Schicht mit niedriger Wellengeschwindigkeit entspricht, schwach andeutet, und ein zweites Minimum bei 275 km liegt. Nach einem ausgeprägten Minimum zwischen 400 und 475 km Tiefe, steigt die Deformationsauslösung erneut, etwa exponential, im Tiefenbereich zwischen 475 und 650 km an, und nimmt danach schnell ab. Der Verlauf der Deformationsauslösung in Abhängigkeit von der Tiefe wird an Hand der physikalischen Verhältnisse im Erdkörper, sowie der Intensität der Deformationsaufspeicherung gedeutet. Insbesondere wird der Anstieg zwischen 475 und 650 km einer Änderung der Temperatur und des Druckes mit der Tiefe, bei Phasensprung und möglicher Änderung in der Zusammensetzung des Materials zugeschrieben. Die Tiefenabhängigkeit der Anzahl der Beben und der Deformationsauslösung verlaufen annähernd parallel; die mittlere Deformationsauslösung pro Erdbeben zeigt lediglich eine unbedeutende Abnahme mit der Tiefe.

     

Propagation ofSn andPn to teleseismic distances

Summary Sn andPn waves propagated to teleseismic distances are investigated by means of short-period seismograph records of the Swedish network.Sn is found in the distance range of 2400 to 4600 km andPn in the range 3500 to 3900 km, but only provided the path is exceptionally homogeneous. Almost all paths are restricted to the Russian platform. There are probably very few areas in the world offering similar propagation paths. The velocities just under the Mohorovii discontinuity are found to be 4.72 km/sec and 8.26 km/sec for transverse and longitudinal waves respectively. In addition, other properties of the teleseismicSn andPn are investigated, such as periods, dispersion, amplitudes, particle motions, propagation mechanisms, and comparisons are made withPa, Sa, withLi, Lg1, Lg2 and withP. The fact that teleseismicPn occurs much more seldom than teleseismicSn could be explained by different velocity profiles just under the crust.     

A tectono-stratigraphic record of an extensional basin: the Lower Jurassic Ab-Haji Formation of east-central Iran

The Lower Jurassic Ab-Haji Formation consists of siliciclastic strata which are widespread and superbly exposed across the Tabas and Lut blocks of east-central Iran. The formation records the geodynamic history of central Iran during the Early Jurassic in the aftermath of the main Cimmerian event (near the Triassic–Jurassic boundary) through its sedimentary facies and stratigraphic architecture and allows palaeogeographic and palaeoenvironmental reconstructions. We measured and studied three well-exposed outcrop sections and identified lithofacies and facies associations (fluvial plain, delta plain, delta front, prodelta, and shallow-marine siliciclastic shelf). The integration of all geological, stratigraphic, and sedimentological data shows a west-to-east continental-to-marine gradient within the Ab-Haji Formation. Based on thickness variations, lateral facies changes, palaeocurrent patterns, and changes in the nature of the basal contact of the Ab-Haji Formation on the Tabas and Lut blocks, we locate the fault-bounded Yazd Block in the west and the Shotori Swell at the eastern edge of the Tabas Block as provenance regions. The pattern of thickness variations, rapid east–west facies changes, and provenance is best explained by a tectonic model invoking large tilted fault blocks in an extensional basin. The basal unit shows distinct increase in grain size at the base of the Ab-Haji Formation, similar to the Shemshak Group of the Alborz Mountains (the base of the Alasht Formation) and the non-marine time-equivalent succession of the Binalud Mountains of northeastern Iran. This grain size pattern may have been caused by rapid source area uplift due to slab break-off of the subducted Iran plate in the course of the Cimmerian collision in east-central Iran.     

A method to reconstruct flood scenarios using field interviews and hydrodynamic modelling: application to the 2017 Suleja and Tafa,Nigeria flood

Natural Hazards - The scarcity of model input and calibration data has limited efforts in reconstructing scenarios of past floods in many regions globally. Recently, the number of studies that use...     

Carbonation of lignite fly ash at ambient T and P in a semi-dry reaction system for CO2 sequestration

The global rise in atmospheric greenhouse gas concentrations calls for practicable solutions to capture CO₂. In this study, a mineral carbonation process was applied in which CO₂ reacts with alkaline lignite ash and forms stable carbonate solids. In comparison to previous studies, the assays were conducted at low temperatures and pressures and under semi-dry reaction conditions in an 8 L laboratory mixing device. In order to find optimum process conditions the pCO₂ (10-20%), stirring rate (500-3000 rpm) and the liquid to solid ratio (L/S = 0.03-0.36 L kg⁻¹) were varied. In all experiments a considerable CO₂ uptake from the gas phase was observed. Concurrently the solid phase contents of Ca and Mg (hydr)oxides decreased and CaCO₃ and MgCO₃ fractions increased throughout the experiments, showing that CO₂ was stabilized as a solid carbonate. The carbonation reaction depends on three factors: Dissolution of CO₂ in the liquid phase, mobilization of Ca and Mg from the mineral surface and precipitation of the carbonate solids. Those limitations were found to depend strongly on the variation of the process parameters. Optimum reaction conditions could be found for L/S ratios between 0.12 and 0.18, medium stirring velocities and pCO₂ between 10% and 20%.Maximum CO₂ uptake by the solid phase was 4.8 mmol g⁻¹ after 120 min, corresponding to a carbonation efficiency for the alkaline material of 53% of the theoretical CO₂ binding capacity. In comparison to previous studies both CO₂ uptake and carbonation efficiencies were in a similar range, but the reaction times in the semi-dry process were considerably shorter. The proposed method additionally allows for a more simple carbonation setup due to low T and P, and produces an easier to handle product with low water content.     

Assessment of Discharge through a Dike Breach and Simulation of Flood Wave Propagation

This paper presents a simple and fast method to calculate flow through a dike breach. The approach was based on two-dimensional numerical simulations of idealized dike breakages at straight river-sections. As a result, computation of discharge through a breach can be achieved by use of the new developed formula (denoted as dike break formula). Furthermore, a methodology that combines one-dimensional hydrodynamic modelling, the dike break formula and a simple GIS-based method to estimate inundation areas is described. This fast and easy-to-handle tool can be utilized for near real-time forecasting or evacuation decisions. Detailed predictions were made for a number of flood and dike break scenarios at the River Rhine to prove the accuracy of the new method compared with two-dimensional numerical models.     

Climate Change driven evolution of hazards to Europe’s transport infrastructure throughout the twenty-first century

Air circulation due to the urban heat island (UHI) effect can influence the dispersion of air pollutants in a metropolis. This study focusses on the influence of the UHI effect on particulate matter (PM; including PM_2.5 and PM_2.5–10) between May and September 2010–2012 in the Taipei basin. Meteorological and PM data were obtained from the sites, owned by the governmental authorities. The analysis was carried out using t test, relative indices (RIs), Pearson product–moment correlation and stepwise regression. The results show that the RI values for PM were the highest at moderate UHI intensity (MUI; 2 °C ≤ UHI < 4 °C) rather than at strong UHI intensity (SUI; 4 °C ≤ UHI) during the peak time for anthropogenic emissions (20:00 LST). Neither the accumulation of PM nor the surface convergence occurred in the hot centre, as shown by the case study. At MUI, more than 89 % of the synoptic weather patterns showed that the weather was clear and hot or that the atmosphere was stable. The variation in PM was associated with horizontal and vertical air dispersion. Poor horizontal air dispersion, with subsidence, caused an increase in PM at MUI. However, the updraft motion diluted the PM at SUI. The stepwise regression models show that the cloud index and surface air pressure determined the variation in PM_2.5–10, while cloud index, wind speed and mixing height influenced the variation in PM_2.5. In conclusion, a direct relationship between UHI effect and PM was not obvious.     

Generation of a consistent absolute phase-center correction model for GPS receiver and satellite antennas

The development and numerical values of the new absolute phase-center correction model for GPS receiver and satellite antennas, as adopted by the International GNSS (global navigation satellite systems) Service, are presented. Fixing absolute receiver antenna phase-center corrections to robot-based calibrations, the GeoForschungsZentrum Potsdam (GFZ) and the Technische Universität München reprocessed more than 10 years of GPS data in order to generate a consistent set of nadir-dependent phase-center variations (PCVs) and offsets in the z-direction pointing toward the Earth for all GPS satellites in orbit during that period. The agreement between the two solutions estimated by independent software packages is better than 1 mm for the PCVs and about 4 cm for the z-offsets. In addition, the long time-series facilitates the study of correlations of the satellite antenna corrections with several other parameters such as the global terrestrial scale or the orientation of the orbital planes with respect to the Sun. Finally, completely reprocessed GPS solutions using different phase-center correction models demonstrate the benefits from switching from relative to absolute antenna phase-center corrections. For example, tropospheric zenith delay biases between GPS and very long baseline interferometry (VLBI), as well as the drift of the terrestrial scale, are reduced and the GPS orbit consistency is improved.     

The contribution of Very Long Baseline Interferometry to ITRF2005

The contribution of the International VLBI Service for Geodesy and Astrometry (IVS) to the ITRF2005 (International Terrestrial Reference Frame 2005) has been computed by the IVS Analysis Coordinator’s office at the Geodetic Institute of the University of Bonn, Germany. For this purpose the IVS Analysis Centres (ACs) provided datum-free normal equation matrices in Solution INdependent EXchange (SINEX) format for each 24 h observing session to be combined on a session-by-session basis by a stacking procedure. In this process, common sets of parameters, transformed to identical reference epochs and a prioris, and especially representative relative weights have been taken into account for each session. In order to assess the quality of the combined IVS files, Earth orientation parameters (EOPs) and scaling factors have been derived from the combined normal equation matrices. The agreement of the EOPs of the combined normal equation matrices with those of the individual ACs in terms of weighted root mean square (WRMS) is in the range of 50–60 μas for the two polar motion components and about 3 μs for UT1−UTC. External comparisons with International GNSS Serive (IGS) polar motion components is at the level of 130–170 μas and 21 μs/day for length of day (LOD). The scale of the terrestrial reference frame realized through the IVS SINEX files agrees with ITRF2000 at the level of 0.2 ppb.     

Comparison of large-area land cover products with national forest inventories and CORINE land cover in the European Alps

Considerable efforts have recently resulted in the development of global land cover data at large spatial scales. The main objective of this study is a comparison of different AVHRR- and MODIS-based forest and land cover products at the scale of the European Alps: a large natural ecosystem that is exposed to both natural environmental threats and human impacts and exploitation. In a first test, the accuracy of land cover products in predicting the overall amount of forest across national boundaries was assessed using national forest inventory statistics. Both variants of forest class combinations resulted in a general overestimation of the forest area. The IGBP 2.0 cover performed best with an overall mean absolute error of 13% and a bias of 0%. In a second test, large-area land cover products were tested for accuracy in predicting 13 aggregated land cover types in a spatially explicit manner using CORINE land cover as reference dataset. Due to data inconsistencies, partly insufficient spatial resolution, steep terrain and land use heterogeneity of the European Alps, only partly satisfactory results were obtained.