Software defined radio for ground and airborne GNSS reflectometry

Software defined radio (SDR) appears as a\ua0suitable solution for dedicated GNSS reflectometry (GNSS-R)\ua0applications. Not only does the flexibility of SDR allow for\ua0easy and rapid prototyping, but also do recent technological\ua0developments of SDR front-ends support real-time operation\ua0of GNSS-R. Our presentation includes a discussion about the\ua0technical aspects of SDR for GNSS-R and we show results\ua0from a ground-based GNSS-R SDR receiver which was\ua0operated continuously over a more than a month at the\ua0Onsala Space Observatory. A summary of our current\ua0activities in relation to airborne GNSS-R solutions and initial\ua0results in the form of Delay-Doppler Maps (DDMs) will\ua0conclude the presentation

Application of Surface wave methods for seismic site characterization

Surface-wave dispersion analysis is widely used in geophysics to infer a shear wave velocity model of the subsoil for a wide variety of applications. A shear-wave velocity model is obtained from the solution of an inverse problem based on the surface wave dispersive propagation in vertically heterogeneous media. The analysis can be based either on active source measurements or on seismic noise recordings. This paper discusses the most typical choices for collection and interpretation of experimental data, providing a state of the art on the different steps involved in surface wave surveys. In particular, the different strategies for processing experimental data and to solve the inverse problem are presented, along with their advantages and disadvantages. Also, some issues related to the characteristics of passive surface wave data and their use in H/V spectral ratio technique are discussed as additional information to be used independently or in conjunction with dispersion analysis. Finally, some recommendations for the use of surface wave methods are presented, while also outlining future trends in the research of this topic

(Table 1, page 215) Chemical composition Mn deposits from the Middle Jurassic part of the Austrian Kalkalpen

The X-ray diffraction analyzes of two ferromanganese crust samples found at the base of the Klaus red Jurassic limestone beds of the Unterberg formation indicate pyrolusite as the main mineral. The crusts contain also a range of trace elements in concentrations comparable of present day oceanic deposits. The low Fe/Mn ratio found in sample 06-32a is in agreement with the geochemical data from Pacific Ocean manganese nodules and crusts of hydrothermal genesis. However, the simultaneously high contents in cerium and yttrium (rare earth metals) are more likely to suggest a precipitation of the manganese from the free water column (hydrogenetic origin). In addition, there are no identified hydrothermal sources in the vicinity of the hosting limestone beds. Iron-rich manganese nodules have also been found in the Jurrasic limestones beds of the Ruhpolding formation. In these deposits, hematite is the dominant mineral phase. The high Fe/Mn ratio as well the detritic material they contain (quartz, mica) lead to a possible continental margin origin for these nodules

Joint inversion of Rayleigh wave ellipticity and spatial autocorrelation measurements

The local soil structure (i.e. shear and pressure wave velocities) can be obtained by inversion of dispersion curves ranging over a sufficiently large frequency band. However, measurements of such dispersion curves using ambient seismic vibrations require a large number of seismometers and a long measuring time. As a simple alternative, we propose to invert Rayleigh wave ellipticity obtained by ambient seismic noise measurements at a single site using a method based on the random decrement technique (Hobiger et al., 2009). Indeed, the freSeismological Research Letters Volume 81, Number 2 March/April 2010 305 quency-dependency of Rayleigh wave ellipticity is tightly related to the shear wave profile of the soil. However, as different soil structures can result in the same ellipticity curve (e.g. homothetic structures in velocity and thickness), the inversion of ellipticity curves alone is ambiguous. Therefore, additional measurements fixing the shearwave velocity in the superficial layers have to be included into the inversion process. We suggest using a small number of seismic stations to measure spatial autocorrelation curves. In this way, three seismic sensors and one hour of measurements can be sufficient to invert the local soil structure. We will present the method to extract the Rayleigh wave ellipticity curve, show which parts of the ellipticity curve have to be included in the inversion process and demonstrate the benefit of the additional spatial autocorrelation curve measurements. Then, we will present an example application to real noise data collected within the framework of the European NERIES project at well-known European accelerometric sites and the results will be compared to thPublishedMontpellier, France4.1. Metodologie sismologiche per l'ingegneria sismicarestricte

Joint inversion of Rayleigh wave ellipticity and spatial autocorrelation measurements

The local soil structure (i.e. shear and pressure wave velocities) can be obtained by inversion of dispersion curves ranging over a sufficiently large frequency band. However, measurements of such dispersion curves using ambient seismic vibrations require a large number of seismometers and a long measuring time. As a simple alternative, we propose to invert Rayleigh wave ellipticity obtained by ambient seismic noise measurements at a single site using a method based on the random decrement technique (Hobiger et al., 2009). Indeed, the freSeismological Research Letters Volume 81, Number 2 March/April 2010 305 quency-dependency of Rayleigh wave ellipticity is tightly related to the shear wave profile of the soil. However, as different soil structures can result in the same ellipticity curve (e.g. homothetic structures in velocity and thickness), the inversion of ellipticity curves alone is ambiguous. Therefore, additional measurements fixing the shearwave velocity in the superficial layers have to be included into the inversion process. We suggest using a small number of seismic stations to measure spatial autocorrelation curves. In this way, three seismic sensors and one hour of measurements can be sufficient to invert the local soil structure. We will present the method to extract the Rayleigh wave ellipticity curve, show which parts of the ellipticity curve have to be included in the inversion process and demonstrate the benefit of the additional spatial autocorrelation curve measurements. Then, we will present an example application to real noise data collected within the framework of the European NERIES project at well-known European accelerometric sites and the results will be compared to t

Ground structure imaging by inversions of Rayleigh wave ellipticity : sensitivity analysis and application to European strong-motion sites

The knowledge of the local soil structure is important for the assessment of seismic hazards. A widespread, but time-consuming technique to retrieve the parameters of the local underground is the drilling of boreholes. Another way to obtain the shear wave velocity profile at a given location is the inversion of surface wave dispersion curves. To ensure a good resolution for both superficial and deeper layers, the used dispersion curves need to cover a wide frequency range. This wide frequency range can be obtained using several arrays of seismic sensors or a single array comprising a large number of sensors. Consequently, these measurements are time-consuming. A simpler alternative is provided by the use of the ellipticity of Rayleigh waves. The frequency dependence of the ellipticity is tightly linked to the shear wave velocity profile. Furthermore, it can be measured using a single seismic sensor. As soil structures obtained by scaling of a given model exhibit the same ellipticity curve, any inversion of the ellipticity curve alone will be ambiguous. Therefore, additional measurements which fix the absolute value of the shear wave velocity profile at some points have to be included in the inversion process. Small-scale spatial autocorrelation measurements or MASW measurements can provide the needed data. Using a theoretical soil structure, we show which parts of the ellipticity curve have to be included in the inversion process to get a reliable result and which parts can be omitted. Furthermore, the use of autocorrelation or high-frequency dispersion curves will be highlighted. The resulting guidelines for inversions including ellipticity data are then applied to real data measurements collected at 14 different sites during the European NERIES project. It is found that the results are in good agreement with dispersion curve measurements. Furthermore, the method can help in identifying the mode of Rayleigh waves in dispersion curve measurements