The center of lateral iso-density contours for inclined cosmic air showers

The horizontal lateral density of a cosmic air shower with a non-zero zenith angle is asymmetric. The asymmetry consist of a stretching of the iso-density contours to ellipses and to a shift of the center of the elliptic contours with respect to the core of the shower. The shift is caused by atmospheric attenuation. The modeling of the attenuation results in an equation for the shift as a function of zenith angle and the size of the iso-density contours. A more accurate equation is obtained by investigating the shift in lateral densities of simulated showers. It is shown how the shift can be incorporated in an elliptic lateral density function. A linear approximation for the shift allows for an analytical solution for the shifted elliptic density. Its predictions for the polar variations of the density are compared with data of simulated showers.Comment: 30 pages, 20 figure

Constraints on crustal attenuation and three-dimensional spatial distribution of stress drop in Switzerland

We employ two different methods to estimate attenuation-corrected source spectra and calculate Brune stress drops of small to medium earthquakes in Switzerland and the surrounding region. We test trade-offs between source and travel path contributions by comparing results between a data-driven and a model-dependent method of distinguishing between the two. Systematic differences between results from both methods can best be reconciled by assuming intrinsic whole-path attenuation to be frequency dependent. A two-parameter grid search based on a power-law Q( f ) function reveals trade-offs that prevent us from quantifying a more exact frequency dependence. However, a comparison of the two-source parameter inversion methods with synthetic tests provide evidence for a non-negligible frequency dependence of Q between 1 and 30 Hz. Consideration of these implications on the attenuation model, as well as consideration of lateral and vertical variations of velocity and quality factor reduces the scatter of the obtained stress drop estimates. Synthetic tests confirm that both methods are able to robustly resolve lateral variations of Brune stress drop with quantifiable uncertainty estimates. Resulting lateral variations show reduced stress drop along the Alpine deformation front. This pattern points to tectonic causes and may be due to variations in differential stres

Surface-wave group-delay and attenuation kernels

We derive both 3-D and 2-D Fréchet sensitivity kernels for surface-wave group-delay and anelastic attenuation measurements. A finite-frequency group-delay exhibits 2-D off-ray sensitivity either to the local phase-velocity perturbation δc/c or to its dispersion ω(∂/∂ω)(δc/c) as well as to the local group-velocity perturbation δC/C. This dual dependence makes the ray-theoretical inversion of measured group delays for 2-D maps of δC/C a dubious procedure, unless the lateral variations in group velocity are extremely smooth

The 3D Attenuation Structure of Deception Island (Antarctica)

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Source and dynamics of a volcanic caldera unrest : Campi Flegrei, 1983–84

Acknowledgements We thank Tiziana Vanorio, Antonella Amoruso, Luca Crescentini, Nicholas Rawlinson, Yasuko Takei, and David Cornwell for the valuable suggestions regarding the methodology and interpretation. Reviews from Tim Greenfield and two anonymous reviewers helped improving both clarity of the manuscript and interpretation. The Royal Society of Edinburgh - Accademia dei Lincei Bilateral Agreement, the Santander Mobility Award of the College of Physical Sciences, University of Aberdeen, and the TIDES EU COST action granted L.D.S. travel grants for the realisation of this study. E.D.P. has been supported by the EPHESTO and KNOWAVES projects, funded by the Spanish Ministry of Education and Science.Peer reviewedPublisher PD