Localization and characterization of an active fault in an urbanized area in central Guatemala by means of geoelectrical imaging

The Polochic and Motagua faults define the active plate boundary between the North American and Caribbean plates in central Guatemala. A splay of the Polochic Fault traverses the rapidly growing city of San Miguel Uspantan that is periodically affected by destructive earthquakes. This fault splay was located using a 2D electrical resistivity tomography (ERT) survey that also characterized the fault damage zone and evaluated the thickness and nature of recent deposits upon which most of the city is built. ERT images show the fault as a similar to 50 m wide, near-vertical low-resistivity anomaly, bounded within a few meters by high resistivity anomalies. Forward modeling reproduces the key aspects of the observed electrical resistivity data with remarkable fidelity thus defining the overall location, geometry, and internal structure of the fault zone as well as the affected lithologies. Our results indicate that the city is constructed on a similar to 20 m thick surficial layer consisting of poorly consolidated, highly porous, water-logged pumice. This soft layer is likely to amplify seismic waves and to liquefy upon moderate to strong ground shaking. The electrical conductivity as well as the major element chemistry of the groundwater provides evidence to suggest that the local aquifer might, at least in part, be fed by water rising along the fault. Therefore, the potential threat posed by this fault splay may not be limited to its seismic activity per se, but could be compounded its potential propensity to enhance seismic site effects by injecting water into the soft surficial sediments. The results of this study provide the basis for a rigorous analysis of seismic hazard and sustainable development of San Miguel Uspantan and illustrate the potential of ERT surveying for paleoseismic studies.

Note on seismic hazard assessment using gradient of uplift velocities on the Turan Block (Central Asia)

Uplift gradients can provide the location of highly strained zones, which can be considered to be seismic. The Turan block (Central Asia) contains zones with high gradient of uplift velocities, above the threshold 0.04mm km-1year-1. Some of these zones are associated with important seismic activity and others are not correlated with any recent important recorded earthquakes, however, recent faults scarps as well as diverted rivers may indicate a recent tectonic activity. This threshold of gradient is probably a significant rheologic property of the upper crust. On the basis of these considerations the Uzboy river area is proposed as a potential high seismic hazard zone.

Global mass wasting during the Middle Ordovician: Meteoritic trigger or plate-tectonic environment ?

Mass wasting at continental margins on a global scale during the Middle Ordovician has recently been related to high meteorite influx. Although a high meteorite influx during the Ordovician should not be neglected, we challenge the idea that mass wasting was mainly produced by meteorite impacts over a period of almost 10 Ma. Having strong arguments against the impact-related hypothesis, we propose an alternative explanation, which is based on a re-evaluation of the mass wasting sites, considering their plate-tectonic distribution and the global sea level curve. A striking and important feature is the distribution of most of the mass wasting sites along continental margins characterised by periods of magmatism, terrane accretion and continental or back-arc rifting, respectively, related to subduction of oceanic lithosphere. Such processes are commonly connected with seismic activity causing earthquakes, which can cause downslope movement of sediment and rock. Considering all that, it seems more likely that most of this mass wasting was triggered by earthquakes related to plate-tectonic processes, which caused destabilisation of continental margins resulting in megabreccias and debris flows. Moreover, the period of mass wasting coincides with sea level drops during global sea level lowstand. In some cases, sea level drops can release pore-water overpressure reducing sediment strength and hence promoting instability of sediment at continental margins. Reduced pore-water overpressure can also destabilise gas hydrate-bearing sediment, causing slope failure, and thus resulting in submarine mass wasting. Overall, the global mass wasting during the Middle Ordovician does not need meteoritic trigger. (C) 2010 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

Fluid evolution at the Variscan front in the vicinity of the Aachen thrust

Quartz-carbonate-chlorite veins were studied in borehole samples of the RWTH-1 well in Aachen. Veins formed in Devonian rocks in the footwall of the Aachen thrust during Variscan deformation and associated fluid flow. Primary fluid inclusions indicate subsolvus unmixing of a homogenous H(2)O-CO(2)-CH(4)-(N(2))-Na-(K)-Cl fluid into a H(2)O-Na-(K)-Cl solution and a vapour-rich CO(2)-(H(2)O, CH(4), N(2)) fluid. The aqueous end-member composition resembles that of metamorphic fluids of the Variscan front zone with salinities ranging from 4 to 7% NaCl equiv. and maximum homogenisation temperatures of close to 400A degrees C. Pressure estimates indicate a burial depth between 4,500 and 8,000 m at geothermal gradients between 50 and 75A degrees C/26 MPa, but pressure decrease to sublithostatic conditions is also indicated, probably as a consequence of fracture opening during episodic seismic activity. A second fluid system, mainly preserved in pseudo-secondary and secondary fluid inclusions, is characterised by fluid temperatures between 200 and 250A degrees C and salinities of < 5% NaCl equiv. Bulk stable isotope analyses of fluids released from vein quartz, calcite, and dolomite by decrepitation yielded delta D(H2O) values from -89 to -113 aEuro degrees, delta(13)C(CH4) from -26.9 to -28.9aEuro degrees (VPDB) and delta(13)C(CO2) from -12.8 to -23.3aEuro degrees (VPDB). The low delta D and delta(13)C range of the fluids is considered to be due to interaction with cracked hydrocarbons. The second fluid influx caused partial isotope exchange and disequilibrium. It is envisaged that an initial short lived flux of hot metamorphic fluids expelled from the epizonal metamorphic domains of the Stavelot-Venn massif. The metamorphic fluid was focused along major thrust faults of the Variscan front zone such as the Aachen thrust. A second fluid influx was introduced from formation waters in the footwall of the Aachen thrust as a consequence of progressive deformation. Mixing of the cooler and lower salinity formation water with the hot metamorphic fluid during episodic fluid trapping resulted in an evolving range of physicochemical fluid inclusion characteristics.

Eleven-year physical activity trends in a Swiss urban area.

OBJECTIVE: Regular physical activity is a major health determinant. Little is known about physical activity trends. We evaluated whether adult physical activity levels are changing in a Swiss urban state (Geneva). METHOD: We analyzed 11-year trends of physical activity indicators, including 3+MET-minutes per week and physical activity outside working hours, in population representative adults (n=9320, aged 35-74years, 50% women), relating declared physical activity to socioeconomic status, lifestyle, and clinical and blood markers. RESULTS: Combining yearly cohorts from 1999 to 2009, we found a significant trend for increased physical activity levels. Weekly age and sex adjusted 3+MET-minutes per week increased from 3023 to 3752, between 1999 and 2009 (P=0.02). The increase also concerned physical activity outside working hours (+18kcal/day/year). There was a shift from low levels of physical activity levels towards higher activities. Physical activity indicators were associated with socioeconomic status, comorbidities, and biological and anthropometric measures. The trend for increased physical activity was more prominent over the latter 5years. CONCLUSION: We found that physical activity levels have increased in an urban Swiss state. The increase is significant but small, and further efforts to promote physical activity are therefore warranted.

Increased activation in Broca's area after cognitive remediation in schizophrenia.

Functional magnetic resonance imaging (fMRI) was used to measure changes in cerebral activity in patients with schizophrenia after participation in the Cognitive Remediation Program for Schizophrenia and other related disorders (RECOS). As RECOS therapists make use of problem-solving and verbal mediation techniques, known to be beneficial in the rehabilitation of dysexecutive syndromes, we expected an increased activation of frontal areas after remediation. Executive functioning and cerebral activation during a covert verbal fluency task were measured in eight patients with schizophrenia before (T1) and after (T2) 14 weeks of RECOS therapy. The same measures were recorded in eight patients with schizophrenia who did not participate in RECOS at the same intervals of time (TAU group). Increased activation in Broca's area, as well as improvements in performance of executive/frontal tasks, was observed after cognitive training. Metacognitive techniques of verbalization are hypothesized to be the main factor underlying the brain changes observed in the present study.

Control of landslide retrogression by discontinuities: Evidence by the integration of airbone- and ground-based geophysical information

The objective of this work is to present a multitechnique approach to define the geometry, the kinematics, and the failure mechanism of a retrogressive large landslide (upper part of the La Valette landslide, South French Alps) by the combination of airborne and terrestrial laser scanning data and ground-based seismic tomography data. The advantage of combining different methods is to constrain the geometrical and failure mechanism models by integrating different sources of information. Because of an important point density at the ground surface (4. 1 points m?2), a small laser footprint (0.09 m) and an accurate three-dimensional positioning (0.07 m), airborne laser scanning data are adapted as a source of information to analyze morphological structures at the surface. Seismic tomography surveys (P-wave and S-wave velocities) may highlight the presence of low-seismic-velocity zones that characterize the presence of dense fracture networks at the subsurface. The surface displacements measured from the terrestrial laser scanning data over a period of 2 years (May 2008?May 2010) allow one to quantify the landslide activity at the direct vicinity of the identified discontinuities. An important subsidence of the crown area with an average subsidence rate of 3.07 m?year?1 is determined. The displacement directions indicate that the retrogression is controlled structurally by the preexisting discontinuities. A conceptual structural model is proposed to explain the failure mechanism and the retrogressive evolution of the main scarp. Uphill, the crown area is affected by planar sliding included in a deeper wedge failure system constrained by two preexisting fractures. Downhill, the landslide body acts as a buttress for the upper part. Consequently, the progression of the landslide body downhill allows the development of dip-slope failures, and coherent blocks start sliding along planar discontinuities. The volume of the failed mass in the crown area is estimated at 500,000 m3 with the sloping local base level method.

Imaging molasse and quaternary sediments in Lake Geneva, Switzerland, with 3-D high-resolution seismic reflection methods: A case study

A high-resolution three-dimensional (3-D) seismic reflection survey was conducted in Lake Geneva, near the city of Lausanne, Switzerland, as part of a project for developing such seismic techniques. Using a single 48-channel streamer, the 3-D site with an area of 1200 m x 600 m was surveyed in 10 days. A variety of complex geologic structures (e.g. thrusts, folds, channel-fill) up to similar to150 m below the water bottom were obtained with a 15 in.(3) water gun. The 3-D data allowed the construction of an accurate velocity model and the distinction of five major seismic facies within the Lower Freshwater Molasse (Aquitanian) and the Quaternary sedimentary units. Additionally, the Plateau Molasse (PM) and Subalpine Molasse (SM) erosional surface, "La Paudeze" thrust fault (PM-SM boundary) and the thickness of Quaternary sediments were accurately delineated in 3-D.

Early functional differentiation in the chick embryonic disc: interaction between mechanical activity and extracellular matrix

The mechanical behaviour of ectodermal cells in the area opaca and the supracellular organization of fibronectin in the adjacent extracellular matrix were studied in whole chick blastoderms developing in vitro. The pattern of spontaneous mechanical activity and its modification by immunoglobulins against fibronectin were determined using a real-time image-analysis system. The pattern of fibronectin was studied using immunocytochemical techniques. It was found that the ectodermal cells in the area opaca actively develop a radially oriented contraction, which leads to a distension of the area pellucida from which the embryo develops. Abnormally increased tension resulted in perturbations of gastrulation and neurulation. An optimized mechanical equilibrium within the blastoderm seems to be necessary for normal development. Anti-fibronectin antibodies applied to the basal side of the blastoderm led rapidly and reversibly to an increase of tension in the contracted cells. This observation indicates that modifications of the extracellular matrix can be transmitted to cytoskeletal elements within adjacent cells. The extracellular matrix of the area opaca contains fibronectin arranged in radially oriented fibrils. This orientation corresponds to the direction of migration of the mesodermal cells. Interestingly, the radial pattern of fibronectin is found in the regions where the ectodermal cells are contracted and develop radially oriented forces. This observation suggests that the supracellular assembly of the extracellular materials could be influenced by the mechanical activity of adjacent cells. Possible modulations of the supracellular organization of extracellular matrix by other factors, e.g. diffusible metabolites, is also discussed. The presence of characteristically organized extracellular matrix components, of spatially differentiated cell activities and of reciprocal interactions between them makes the young chick blastoderm an excellent system for physiological studies of the coordinated cellular activities that lead to changes in form, complexity and function.

Regulation of inflammasome activity.

Summary Interleukin-1beta (IL-1beta) is a potent inflammatory cytokine, which is implicated in acute and chronic inflammatory disorders. The activity of IL-1beta is regulated by the proteolytic cleavage of its inactive precursor resulting in the mature, bioactive form of the cytokine. Cleavage of the IL-1beta precursor is performed by the cysteine protease caspase-1, which is activated within protein complexes termed 'inflammasomes'. To date, four distinct inflammasomes have been described, based on different core receptors capable of initiating complex formation. Both the host and invading pathogens need to control IL-1beta production and this can be achieved by regulating inflammasome activity. However, we have, as yet, little understanding of the mechanisms of this regulation. In particular the negative feedbacks, which are critical for the host to limit collateral damage of the inflammatory response, remain largely unexplored. Recent exciting findings in this field have given us an insight into the potential of this research area in terms of opening up new therapeutic avenues for inflammatory disorders.

Alterations in phosphatidylinositol 3-kinase activity and PTEN phosphatase in the prefrontal cortex of depressed suicide victims.

BACKGROUND: Recent studies have reported alterations in protein kinase B (PKB)/Akt and in its downstream target, glycogen synthase kinase 3β, in depression and suicide. The aim of the present study was to investigate possible impairment of the upstream regulators, namely phosphatidylinositol 3-kinase (PI3K) and PTEN. METHODS: The ventral prefrontal cortex (Brodmann's area 11) of 24 suicide victims and 24 drug-free nonsuicide subjects was used. The antemortem diagnoses of major depression disorder were obtained from the institutional records or psychological autopsy, and toxicological analyses were performed. Protein levels of PI3K and PTEN were assayed using the immunoblot method, and the kinase activity of PI3K and Akt was determined by phosphorylation of specific substrates. RESULTS: A decrease was observed in the enzymatic activity of PI3K [ANOVA: F(3, 44) = 9.20; p < 0.001] and Akt1 [ANOVA: F(3, 44) = 13.59; p < 0.001], without any change in protein levels, in both depressed suicide victims and depressed nonsuicide subjects (p < 0.01 and p < 0.002, respectively). PTEN protein levels were increased in the same groups [ANOVA: F(3, 44) = 10.5; p < 0.001]. No change was observed in nondepressed suicide victims. CONCLUSION: This study concludes that attenuation of kinase activity of PKB/Akt in depressed suicide victims may be due to the combined dysregulation of PTEN and PI3K resulting in insufficient phosphorylation of lipid second messengers. The effect is associated with major depression rather than with suicide per se. Given the cellular deficits reported in major depression, the study of enzymes involved in cell survival and neuroplasticity is particularly relevant to neurotrophic factor dysregulation in depression.

Detailed 3D seismic imaging of a fault zone beneath Lake Geneva, Switzerland

An efficient high-resolution (HR) three-dimensional (3D) seismic reflection system for small-scale targets in lacustrine settings was developed. In Lake Geneva, near the city of Lausanne, Switzerland, the offshore extension of a complex fault zone well mapped on land was chosen for testing our system. A preliminary two-dimensional seismic survey indicated structures that include a thin (<40 m) layer of subhorizontal Quaternary sediments that unconformably overlie south-east-dipping Tertiary Molasse beds and a major fault zone (Paudeze Fault Zone) that separates Plateau and Subalpine Molasse (SM) units. A 3D survey was conducted over this test site using a newly developed three-streamer system. It provided high-quality data with a penetration to depths of 300 m below the water bottom of non-aliased signal for dips up to 30degrees and with a maximum vertical resolution of 1.1 m. The data were subjected to a conventional 3D processing sequence that included post-stack time migration. Tests with 3D pre-stack depth migration showed that such techniques can be applied to HR seismic surveys. Delineation of several horizons and fault surfaces reveals the potential for small-scale geologic and tectonic interpretation in three dimensions. Five major seismic facies and their detailed 3D geometries can be distinguished. Three fault surfaces and the top of a molasse surface were mapped in 3D. Analysis of the geometry of these surfaces and their relative orientation suggests that pre-existing structures within the Plateau Molasse (PM) unit influenced later faulting between the Plateau and SM. In particular, a change in strike of the PM bed dip may indicate a fold formed by a regional stress regime, the orientation of which was different from the one responsible for the creation of the Paudeze Fault Zone. This structure might have later influenced the local stress regime and caused the curved shape of the Paudeze Fault in our surveyed area.

High-resolution seismic images of potentially seismogenic structures beneath the northwest Canterbury Plains, New Zealand

The transpressional boundary between the Australian and Pacific plates in the central South Island of New Zealand comprises the Alpine Fault and a broad region of distributed strain concentrated in the Southern Alps but encompassing regions further to the east, including the northwest Canterbury Plains. Low to moderate levels of seismicity (e. g., 2 > M 5 events since 1974 and 2 > M 4.0 in 2009) and Holocene sediments offset or disrupted along rare exposed active fault segments are evidence for ongoing tectonism in the northwest plains, the surface topography of which is remarkably flat and even. Because the geology underlying the late Quaternary alluvial fan deposits that carpet most of the plains is not established, the detailed tectonic evolution of this region and the potential for larger earthquakes is only poorly understood. To address these issues, we have processed and interpreted high-resolution (2.5 m subsurface sampling interval) seismic data acquired along lines strategically located relative to extensive rock exposures to the north, west, and southwest and rare exposures to the east. Geological information provided by these rock exposures offer important constraints on the interpretation of the seismic data. The processed seismic reflection sections image a variably thick layer of generally undisturbed younger (i.e., < 24 ka) Quaternary alluvial sediments unconformably overlying an older (> 59 ka) Quaternary sedimentary sequence that shows evidence of moderate faulting and folding during and subsequent to deposition. These Quaternary units are in unconformable contact with Late Cretaceous-Tertiary interbedded sedimentary and volcanic rocks that are highly faulted, folded, and tilted. The lowest imaged unit is largely reflection-free Permian Triassic basement rocks. Quaternary-age deformation has affected all the rocks underlying the younger alluvial sediments, and there is evidence for ongoing deformation. Eight primary and numerous secondary faults as well as a major anticlinal fold are revealed on the seismic sections. Folded sedimentary and volcanic units are observed in the hanging walls and footwalls of most faults. Five of the primary faults represent plausible extensions of mapped faults, three of which are active. The major anticlinal fold is the probable continuation of known active structure. A magnitude 7.1 earthquake occurred on 4 September 2010 near the southeastern edge of our study area. This predominantly right-lateral strike-slip event and numerous aftershocks (ten with magnitudes >= 5 within one week of the main event) highlight the primary message of our paper: that the generally flat and topographically featureless Canterbury Plains is underlain by a network of active faults that have the potential to generate significant earthquakes.

Regulation of inflammasome activity.

Summary Interleukin-1beta (IL-1beta) is a potent inflammatory cytokine, which is implicated in acute and chronic inflammatory disorders. The activity of IL-1beta is regulated by the proteolytic cleavage of its inactive precursor resulting in the mature, bioactive form of the cytokine. Cleavage of the IL-1beta precursor is performed by the cysteine protease caspase-1, which is activated within protein complexes termed 'inflammasomes'. To date, four distinct inflammasomes have been described, based on different core receptors capable of initiating complex formation. Both the host and invading pathogens need to control IL-1beta production and this can be achieved by regulating inflammasome activity. However, we have, as yet, little understanding of the mechanisms of this regulation. In particular the negative feedbacks, which are critical for the host to limit collateral damage of the inflammatory response, remain largely unexplored. Recent exciting findings in this field have given us an insight into the potential of this research area in terms of opening up new therapeutic avenues for inflammatory disorders.