Probabilistic seismic hazard assessment of Switzerland: best estimates and uncertainties

We present the results of a new genera tion of probabilistic seismic hazard assessment for Switzerland. This study replaces the previous intensity-based generation of national hazard maps of 1978. Based on a revised moment-magnitude earthquake catalog for Switzerland and the surrounding regions, covering the period 1300–2003, sets of recurrence parameters (a and b values, M _max ) are estimated. Information on active faulting in Switzerland is too sparse to be used as source model. We develop instead two models of areal sources. The first oriented towards capturing historical and instrumental seismicity, the second guided largely by tectonic principles and express ing the alterative view that seismicity is less stationary and thus future activity may occur in previously quiet regions. To estimate three alterna tive a and b value sets and their relative weighting, we introduce a novel approach based on the modified Akaike information criterion, which allows us to decide when the data in a zone deserves to be fitted with a zone-specific b value. From these input parameters, we simulate synthetic earthquake catalogs of one-million-year duration down to magnitude 4.0, which also reflect the difference in depth distribution between the Alpine Foreland and the Alps. Using a specific predictive spectral ground motion model for Switzerland, we estimate expected ground motions in units of the 5% damped acceleration response spectrum at frequencies of 0.5–10 Hz for all of Switzerland, referenced to rock sites with an estimated shear wave velocity of 1,500 m/s² in the upper 30 m. The highest hazard is found in the Wallis, in the Basel region, in Graubünden and along the Alpine front, with maximum spectral accelerations at 5 Hz frequency reaching 150 cm/s² for a return period of 475 years and 720 cm/s² for 10,000 years. Electronic supplementary material The online version of this article (doi: ) contains supplementary material, which is available to authorized users.     

Shocked monazite chronometry: integrating microstructural and in situ isotopic age data for determining precise impact ages

Monazite is a robust geochronometer and occurs in a wide range of rock types. Monazite also records shock deformation from meteorite impact but the effects of impact-related microstructures on the U–Th–Pb systematics remain poorly constrained. We have, therefore, analyzed shock-deformed monazite grains from the central uplift of the Vredefort impact structure, South Africa, and impact melt from the Araguainha impact structure, Brazil, using electron backscatter diffraction, electron microprobe elemental mapping, and secondary ion mass spectrometry (SIMS). Crystallographic orientation mapping of monazite grains from both impact structures reveals a similar combination of crystal-plastic deformation features, including shock twins, planar deformation bands and neoblasts. Shock twins were documented in up to four different orientations within individual monazite grains, occurring as compound and/or type one twins in (001), (100), \(\left( 10\bar{1} \right)\), \(~\{110\}\), \(\left\{ 212 \right\},\) and type two (irrational) twin planes with rational shear directions in \([0\bar{1}\bar{1}]\) and \([\bar{1}\bar{1}0]\). SIMS U–Th–Pb analyses of the plastically deformed parent domains reveal discordant age arrays, where discordance scales with increasing plastic strain. The correlation between discordance and strain is likely a result of the formation of fast diffusion pathways during the shock event. Neoblasts in granular monazite domains are strain-free, having grown during the impact events via consumption of strained parent grains. Neoblastic monazite from the Inlandsee leucogranofels at Vredefort records a ²⁰⁷Pb/²⁰⁶Pb age of 2010?±?15 Ma (2σ, n?=?9), consistent with previous impact age estimates of 2020 Ma. Neoblastic monazite from Araguainha impact melt yield a Concordia age of 259?±?5 Ma (2σ, n?=?7), which is consistent with previous impact age estimates of 255?±?3 Ma. Our results demonstrate that targeting discrete microstructural domains in shocked monazite, as identified through orientation mapping, for in situ U–Th–Pb analysis can date impact-related deformation. Monazite is, therefore, one of the few high-temperature geochronometers that can be used for accurate and precise dating of meteorite impacts.     

Systemic geopolitical modeling. Part 2: subjectivity in prediction of geopolitical events

This paper studies subjective priorities for the data amounts in the processing of geopolitical data accoding to Mazis I. Th., theoretical paradigm of Systemic Geopolitical Analysis. After defining geopolitical plans and geopolitical focus sets, they are introduced geopolitical preferences and geopolitical management capacities. The geopolitical rational choice is studied, as well as the geopolitical preference-capacity distributions. Then, they are investigated geopolitical contrasts of subjective priorities by several geopolitical operators, and it is shown that there are cores and equilibriums of geopolitical contrasts, the study of which may provide useful information.     

A note on John Playfair and the statistics of directional data

John Playfair recommended the resultant vector method of averaging directions as early as 1802.     

Interactions of marine plankton with transuranic elements. II. Influence of dissolved organic compounds on americium and plutonium accumulation in a diatom

To assess the significance of naturally occurring dissolved organic matter (DOM) on complexation of transuranic elements in seawater, a series of bioassay experiments was conducted in which the effect of DOM on the accumulation of ²⁴¹ Am, ²³⁷Pu (III–IV), and ²³⁷Pu (V–VI) by the marine diatom Thalassiosira pseudonana was measured. EDTA at 0.3μM complexed both metals substantially, resulting in reduced radio-isotope uptake by the diatom; the greatest effect was on Pu (III–IV). In contrast, there was no apparent complexation of either element by equimolar concentrations of marine fulvic (MFA) or humic acids (MHA), naturally occurring photooxidizable DOM (uncharacterized), or diatom exudates, as none of these materials reduced isotope uptake; on the contrary, there were indications that some of this DOM enhanced transuranic bioaccumulation in the diatom slightly. Subsequent experiments showed this enhancement was probably due to complexation of transition metals by the DOM, leading to fewer ambient ions ‘competing’ for binding sites on the cells; ²⁴¹ Am uptake rates were negatively correlated (r =? 0.846, P < .01) with Σ ASV-labile Cu + Zn + Cd + Pb. These experiments suggest that naturally occurring DOM may not appreciably complex Am or Pu or greatly affect their bioavailability in the sea.     

Late Cretaceous basement foundering of the Rosario embayment, Peninsular Ranges forearc basin: backstripping of the El Gallo Formation, Baja California Norte, Mexico

Excellent exposure, well-controlled palaeobathymetry, and tightly-spaced, high-precision radiometric age control in the El Gallo Fm. permit rigorous quantitative analysis. Backstripping of these proximal nonmarine, forearc basin deposits reveals that, during the Late Cretaceous, the Rosario embayment of the Peninsular Ranges forearc was undergoing an episode of rapid tectonic subsidence. This subsidence had several marked effects on the sedimentology of the Rosario embayment: formation of a broad alluvial plain consisting of coarse-grained clastics; rapid (∼ 600 m Myr^-1) aggradation of sediments; and a retrogradational succession of facies, capped by a marine transgression, as deposition failed to keep pace with eustatic rise and subsidence.
Long-term sedimentation is driven by some combination of two allocyclic mechanisms: tectonic subsidence and eustatic sea-level rise. In order to evaluate which force predominated during deposition of the El Gallo Fm., the processes of sedimentation, compaction, and isostasy are evaluated through the interval in question. A sensitivity analysis is performed, in which the maximum tectonic and maximum eustatic contributions are estimated, along with the best-fit model. These results are qualitatively the same: tectonic subsidence was the major driving force of sedimentation in the Rosario embayment in late Campanian time. Regional sedimentological similarities suggest that this tectonic subsidence may have characterized the Peninsular Ranges forearc margin at this time, reflecting an episode of active down-faulting during the Late Cretaceous.     

Suggestions for some single dish radio astronomy standards

In this paper we examine the possibility of adopting standards within the context of radio astronomy and the benefits to be derived thereby. In particular we consider the application of standards within the three areas of the receiver hardware, the control and communication between different parts of the observing system, and the interface with the astronomer. The adoption of such standards will increase flexibility of observing systems, allow the easy interchange of equipment between observatories and greatly simplify guest observing. In this paper we will only consider the application of standards within the field of millimetre-wave and sub-millimetre-wave single dish astronomy. However, the principle can be easily extended to other astronomical wavebands. We describe some current developments at the Onsala Space Observatory which illustrate the proposed philosophy and show how such standards may be implemented. Naturally, the detailed definition of such standards would have to be agreed in conjunction with other interested astronomical institutions.