Evidence for an active fault below the northwestern Alpine foreland of Switzerland

This study is devoted to the analysis of a prominent concentration of earthquakes whose epicenters delineate an active 20-30 km long N—S trending tectonic feature near the town of Fribourg, in the Molasse Basin of western Switzerland. This feature coincides with the possible southward continuation of the NNE—SSW trending Rhine Graben located approximately 80 km further north. In addition these epicenters are located in the vicinity of the Fribourg Syncline and the Alterswil Culmination, whose structural axes are oriented N—S in this area, instead of being aligned with the predominant regional NE—SW structural trend. Most of the earthquakes belong to one of three series of events that occurred over a time span of 2-4 months in 1987, 1995 and 1999. They include four events with magnitudes between 3 and 4 and one with a magnitude of 4.3. Focal depths, constrained by modelling sPMP-PMP traveltime differences with synthetic seismograms, are around 2 km, which places these events in the sedimentary cover. Fault plane solutions correspond to almost pure strike-slip mechanisms with nearly N—S and E—W oriented nodal planes. High-precision relative locations of individual events within the different earthquake clusters as well as of the relative locations of the clusters to each other show that these earthquakes are associated with left lateral motion along a N—S trending fault system. Deep reaching large scale flower structures in the Mesozoic and Tertiary overburden are observed on interpreted seismic profiles, close to the hypocenters. The unusual N—S trend of the Fribourg Syncline can be attributed to movements along these faults during Oligocene and Miocene times. Also magnetic data support the assumption of a N—S striking fault system in the Fribourg area, possibly related to a Permo-Carboniferous trough. Though the direct link between the fault traces in the overburden and the active fault system at depth could not be established in this study, their similar deformational style and their vicinity suggest that they are related. The total length of the inferred fault carries the potential of a magnitude 6 earthquake and thus constitutes a significant source of seismic hazar

High-resolution 3-D P-wave model of the Alpine crust

The 3-D P-wave velocity structure of the Alpine crust has been determined from local earthquake tomography using a set of high-quality traveltime data. The application of an algorithm combining accurate phase picking with an automated quality assessment allowed the repicking of first arriving P-phases from the original seismograms. The quality and quantity of the repicked phase data used in this study allows the 3-D imaging of large parts of the Alpine lithosphere between 0 and 60 km depth. Our model represents a major improvement in terms of reliability and resolution compared to any previous regional tomographic studies of the Alpine crust. First-order anomalies like crust—mantle boundary (Moho) and the Ivrea body in the Western Alps are well resolved and in good agreement with previous studies. In addition, several (consistent) small-scale anomalies are visible in the tomographic image. A clear continuation of the lower European crust beneath the Adriatic Moho in the Central Alps is not observed in our results. The absence of such a signature may indicate the eclogitization of the subducted European lower crust in the Central Alps. In agreement with previous results, the additional analysis of focal depths in our new 3-D P-wave model shows that all studied earthquakes in the northern foreland have occurred within the European crust. Waveforms and focal depths suggest that at least one of the analysed events south of the Alps is located in the Adriatic mantl

HiHi fMRI: A data-reordering method for measuring the hemodynamic response of the brain with high temporal resolution and high SNR

There is emerging evidence that sampling the blood-oxygen-level-dependent (BOLD) response with high temporal resolution opens up new avenues to study the in vivo functioning of the human brain with functional magnetic resonance imaging. Because the speed of sampling and the signal level are intrinsically connected in magnetic resonance imaging via the T1 relaxation time, optimization efforts usually must make a trade-off to increase the temporal sampling rate at the cost of the signal level. We present a method, which combines a sparse event-related stimulus paradigm with subsequent data reshuffling to achieve high temporal resolution while maintaining high signal levels (HiHi). The proof-of-principle is presented by separately measuring the single-voxel time course of the BOLD response in both the primary visual and primary motor cortices with 100-ms temporal resolution

A comprehensive approach for correcting voxel‐wise b‐value errors in diffusion MRI

Purpose In diffusion MRI, the actual b‐value played out on the scanner may deviate from the nominal value due to magnetic field imperfections. A simple image‐based correction method for this problem is presented. Methods The apparent diffusion constant (ADC) of a water phantom was measured voxel‐wise along 64 diffusion directions at b = 1000 s/mm2. The true diffusion constant of water was estimated, considering the phantom temperature. A voxel‐wise correction factor, providing an effective b‐value including any magnetic field deviations, was determined for each diffusion direction by relating the measured ADC to the true diffusion constant. To test the method, the measured b‐value map was used to calculate the corrected voxel‐wise ADC for additionally acquired diffusion data sets on the same water phantom and data sets acquired on a small water phantom at three different positions. Diffusion tensor was estimated by applying the measured b‐value map to phantom and in vivo data sets. Results The b‐value‐corrected ADC maps of the phantom showed the expected spatial uniformity as well as a marked improvement in consistency across diffusion directions. The b‐value correction for the brain data resulted in a 5.8% and 5.5% decrease in mean diffusivity and angular differences of the primary diffusion direction of 2.71° and 0.73° inside gray and white matter, respectively. Conclusion The actual b‐value deviates significantly from its nominal setting, leading to a spatially variable error in the common diffusion outcome measures. The suggested method measures and corrects these artifacts

Amplitude study of the Pg phase

The amplitude of the Pg phase, as recorded in explosion seismology studies, is analyzed with the aid of synthetic seismograms. Parameters such as source frequency, low-velocity cover above the crust (sediments or weathered layer), low-velocity layers within the upper crust, velocity gradients, thickness of the gradient zone, attenuation and Poisson's ratio strongly influence the amplitude-distance pattern of the Pg phase. A systematic study clearly shows that different models of the continental upper crust display distinct amplitude-distance characteristics. These models could not be distinguished by travel-time interpretation alone. In the presence of gradient zones the amplitude-distance curve shows different patterns depending on the source frequency. The higher the frequency, the more pronounced are the relative maxima in the amplitudes. The presence of a low-velocity cover at the surface accentuates the character of the amplitude-distance curves even if the cover is thin (a few hundred meters). Moreover, a low-velocity cover produces P to S conversions and multiples following the Pg which obscure possible secondary crustal phases. The thickness of the velocity gradient zone influences the amplitude decay and the width of the relative maxima. Low-velocity layers within the upper crust cause a faster drop-off of the amplitudes than would be expected from ray theory. Detailed Pg amplitude studies are thus useful in improving the knowledge of the physical properties of the upper continental crust. The application of the derived criteria to two sets of real data allow us to determine fine details of the velocity-depth function which are of great importance for the understanding of the Earth's crust.           ARK: https://n2t.net/ark:/88439/y083748 Permalink: https://geophysicsjournal.com/article/291 &nbsp

Optimized EPI for fMRI studies of the orbitofrontal cortex: compensation of susceptibility-induced gradients in the readout direction

Object Most functional magnetic resonance imaging (fMRI) studies record the blood oxygen leveldependent (BOLD) signal using gradient-echo echo-planar imaging (GE EPI). EPI can suffer from substantial BOLD sensitivity loss caused by magnetic field inhomogeneities. Here, BOLD sensitivity losses due to susceptibility- induced gradients in the readout (RO) direction are characterized and a compensation approach is developed

Understanding Eurasian convergence: Application of kohonen self-organizing maps

Kohonen self-organizing maps (SOMs) are employed to examine economic and social convergence of Eurasian countries based on a set of twenty-eight socio-economic measures. A core of European Union states is identified that provides a benchmark against which convergence of post-socialist transition economies may be judged. The Central European Visegrád countries and Baltics show the greatest economic convergence to Western Europe, while other states form clusters that lag behind. Initial conditions on the social dimension can either facilitate or constrain economic convergence, as discovered in Central Europe vis-à-vis the Central Asian Republics. Disquiet in the convergence literature is resolved by providing an analysis of the Eurasian states over time. Copyright © 2006 JMASM, Inc

Determining a Role for Ventromedial Prefrontal Cortex in Encoding Action-Based Value Signals During Reward-Related Decision Making

Considerable evidence has emerged to implicate ventromedial prefrontal cortex in encoding expectations of future reward during value-based decision making. However, the nature of the learned associations upon which such representations depend is much less clear. Here, we aimed to determine whether expected reward representations in this region could be driven by action–outcome associations, rather than being dependent on the associative value assigned to particular discriminative stimuli. Subjects were scanned with functional magnetic resonance imaging while performing 2 variants of a simple reward-related decision task. In one version, subjects made choices between 2 different physical motor responses in the absence of discriminative stimuli, whereas in the other version, subjects chose between 2 different stimuli that were randomly assigned to different responses on a trial-by-trial basis. Using an extension of a reinforcement learning algorithm, we found activity in ventromedial prefrontal cortex tracked expected future reward during the action-based task as well as during the stimulus-based task, indicating that value representations in this region can be driven by action–outcome associations. These findings suggest that ventromedial prefrontal cortex may play a role in encoding the value of chosen actions irrespective of whether those actions denote physical motor responses or more abstract decision options

Tribute to Tinbergen: The Place of Animal Behavior in Biology

Tinbergen is famous for emphasizing behavioral fieldwork and experimentation under natural circumstances, for founding the field of ethology, for getting a Nobel Prize, and for mentoring Richard Dawkins. He is known for dividing behavior studies into physiology, development, natural selection, and evolutionary history. In the decades since Tinbergen was active, some of the best research in animal behavior fuses Tinbergen\u27s questions, connecting genes to behavioral phenotypes, for example. Behavior is the most synthetic of the life sciences, because observing the actions of an organism can tell us what all those physical and physiological traits are for. Insights from behavior tell us how traits in one individual impact those in another in ways that challenge our definition of an organism. Behavioral conflict and cooperation among animals has led to theory that explains within-organism conflict and cooperation and human malfunctions of many kinds. Darwin certainly began the evolutionary study of behavior, but Tinbergen brought it forward to the heart of biology. The challenge for the future is to apply concepts from animal behavior across biology with tools that would have amazed Tinbergen

Population Distribution, Settlement Patterns and Accessibility across Africa in 2010

The spatial distribution of populations and settlements across a country and their interconnectivity and accessibility from urban areas are important for delivering healthcare, distributing resources and economic development. However, existing spatially explicit population data across Africa are generally based on outdated, low resolution input demographic data, and provide insufficient detail to quantify rural settlement patterns and, thus, accurately measure population concentration and accessibility. Here we outline approaches to developing a new high resolution population distribution dataset for Africa and analyse rural accessibility to population centers. Contemporary population count data were combined with detailed satellite-derived settlement extents to map population distributions across Africa at a finer spatial resolution than ever before. Substantial heterogeneity in settlement patterns, population concentration and spatial accessibility to major population centres is exhibited across the continent. In Africa, 90% of the population is concentrated in less than 21% of the land surface and the average per-person travel time to settlements of more than 50,000 inhabitants is around 3.5 hours, with Central and East Africa displaying the longest average travel times. The analyses highlight large inequities in access, the isolation of many rural populations and the challenges that exist between countries and regions in providing access to services. The datasets presented are freely available as part of the AfriPop project, providing an evidence base for guiding strategic decisions