Time variation of the European gravity field from superconducting gravimeters   总被引：1，自引：0，他引：1  

David Crossley  Jacques Hinderer  Jean-Paul Boy 《Geophysical Journal International》2005,161(2):257-264

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Current states of stress in the northern Andes as indicated by focal mechanisms of earthquakes   总被引：1，自引：3，他引：1  

Martín Corts  Jacques Angelier 《Tectonophysics》2005,403(1-4):29-58

Systematic inversion of double couple focal mechanisms of shallow earthquakes in the northern Andes reveals relatively homogeneous patterns of crustal stress in three main regions. The first region, presently under the influence of the Caribbean plate, includes the northern segment of the Eastern Cordillera of Colombia and the western flank of the Central Cordillera (north of 4°N). It is characterized by WNW–ESE compression of dominantly reverse type that deflects to NW–SE in the Merida Andes of Venezuela, where it becomes mainly strike–slip in type. A major bend of the Eastern thrust front of the Eastern Cordillera, near its junction with the Merida Andes, coincides with a local deflection of the stress regime (SW–NE compression), suggesting local accommodation of the thrust belt to a rigid indenter in this area. The second region includes the SW Pacific coast of Colombia and Ecuador, currently under the influence of the Nazca plate. In this area, approximately E–W compression is mainly reverse in type. It deflects to WSW–ENE in the northern Andes south of 4°N, where it is accommodated by right-lateral displacement of the Romeral fault complex and the Eastern front of the northern Andes. The third, and most complex, region is the area of the triple junction between the South American, Nazca and Caribbean plates. It reveals two major stress regimes, both mainly strike–slip in type. The first regime involves SW–NE compression related to the interaction between the Nazca and Caribbean plates and the Panama micro-plate, typically accommodated in an E–W left-lateral shear zone. The second regime involves NW–SE compression, mainly related to the interaction between the Caribbean plate and the North Andes block which induces left-lateral displacement on the Uramita and Romeral faults north of 4°N.Deep seismicity (about 150–170 km) concentrates in the Bucaramanga nest and Cauca Valley areas. The inversion reveals a rather homogeneous attitude of the minimum stress axis, which dips towards the E. This extension is consistent with the present plunge of the Nazca and Caribbean slabs, suggesting that a broken slab may be torn under gravitational stresses in the Bucaramanga nest. This model is compatible with current blocking of the subduction in the western northern Andes, inhibiting the eastward displacement of slabs, which are forced to break and sink in to the asthenosphere under their own weight.  相似文献   

Analysis of the interannual variability of annual daily extreme water levels in the St Lawrence River and Lake Ontario from 1918 to 2010          下载免费PDF全文

Ali A. Assani  Raphaëlle Landry  Stacey Biron  Jean‐Jacques Frenette 《水文研究》2014,28(13):4011-4022

We compared the interannual variability of annual daily maximum and minimum extreme water levels in Lake Ontario and the St Lawrence River (Sorel station) from 1918 to 2010, using several statistical tests. The interannual variability of annual daily maximum extreme water levels in Lake Ontario is characterized by a positive long‐term trend showing two shifts in mean (1929–1930 and 1942–1943) and a single shift in variance (in 1958–1959). In contrast, for the St Lawrence River, this interannual variability is characterized by a negative long‐term trend with a single shift in mean, which occurred in 1955–1956. As for annual daily minimum extreme water levels, their interannual variability shows no significant long‐term change in trend. However, for Lake Ontario, the interannual variability of these water levels shows two shifts in mean, which are synchronous with those for maximum water levels, and a single shift in variance, which occurred in 1965–1966. These changes in trend and stationarity (mean and variance) are thought to be due to factors both climatic (the Great Drought of the 1930s) and human (digging of the Seaway and construction of several dams and locks during the 1950s). Despite this change in means and variance, the four series are clearly described by the generalized extreme value distribution. Finally, annual daily maximum and minimum extreme water levels in the St Lawrence and Lake Ontario are negatively correlated with Atlantic multidecadal oscillation over the period from 1918 to 2010. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Sensitivity of soil parameters in unsaturated zone modelling and the relation between effective,laboratory and in situ estimates     

J. Mertens  H. Madsen  M. Kristensen  D. Jacques  J. Feyen 《水文研究》2005,19(8):1611-1633

Simulation of soil moisture content requires effective soil hydraulic parameters that are valid at the modelling scale. This study investigates how these parameters can be estimated by inverse modelling using soil moisture measurements at 25 locations at three different depths (at the surface, at 30 and 60 cm depth) on an 80 by 20 m hillslope. The study presents two global sensitivity analyses to investigate the sensitivity in simulated soil moisture content of the different hydraulic parameters used in a one‐dimensional unsaturated zone model based on Richards' equation. For estimation of the effective parameters the shuffled complex evolution algorithm is applied. These estimated parameters are compared to their measured laboratory and in situ equivalents. Soil hydraulic functions were estimated in the laboratory on 100 cm³ undisturbed soil cores collected at 115 locations situated in two horizons in three profile pits along the hillslope. Furthermore, in situ field saturated hydraulic conductivity was estimated at 120 locations using single‐ring pressure infiltrometer measurements. The sensitivity analysis of 13 soil physical parameters (saturated hydraulic conductivity (K_s), saturated moisture content (θ_s), residual moisture content (θ_r), inverse of the air‐entry value (α), van Genuchten shape parameter (n), Averjanov shape parameter (N) for both horizons, and depth (d) from surface to B horizon) in a two‐layer single column model showed that the parameter N is the least sensitive parameter. K_s of both horizons, θ_s of the A horizon and d were found to be the most sensitive parameters. Distributions over all locations of the effective parameters and the distributions of the estimated soil physical parameters from the undisturbed soil samples and the single‐ring pressure infiltrometer estimates were found significantly different at a 5% level for all parameters except for α of the A horizon and K_s and θ_s of the B horizon. Different reasons are discussed to explain these large differences. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Provenance of buried esker groundwater: the case of Vars-Winchester esker aquifer,Eastern Ontario,Canada     

Jacques Sauriol 《Hydrogeology Journal》2016,24(1):123-139

An innovative mode of groundwater recharge to a buried esker aquifer is considered. The current conceptual model affords a natural safeguard to underlying aquifers from the overlying muds. A hypothesis of groundwater recharge to a buried esker aquifer via preferential pathways across its overlying muds is tested here by heuristic numerical one-dimensional and two-dimensional modeling simulations. The hypothesis has been tested against two other conventionally accepted scenarios involving: (1) distal esker outcrop areas and (2) remote shallow-bedrock recharge areas. The main evidence comes from documented recharge pressure pulses in the overlying mud aquitard and in the underlying esker hydraulic-head time series for the Vars-Winchester esker aquifer in Eastern Ontario, Canada. These perturbations to the potentiometric surface are believed to be the aquifer response to recharge events. The migration rate of these pressure pulses is directly related to the hydraulic diffusivity of the formation. The measured response time and response amplitude between singular radar precipitation events and well hydrographs constituted the heuristic model calibration targets. The main evidence also includes mud-layering deformation (water escape features) which was observed in seismic surveys of the over-esker muds. These disturbed stratigraphic elements provide a realistic mechanism for migrating water to transit through the muds. The effective hydraulic conductivities of these preferential pathways in the muds were estimated to be between 2?×?10^?6 and 7?×?10^?6 m/s. The implications of these findings relate to the alleged natural safeguard of these overlying muds.  相似文献   

Stress changes induced at neighbouring faults by the June 2000 earthquakes,South Iceland Seismic Zone     

Romain Plateaux  Jacques Angelier  Françoise Bergerat  Frederic Cappa  Ragnar Stefánsson 《地学学报》2010,22(2):79-86

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Record of enhanced late Pliocene tectono‐volcanic activity in the Lesser Antilles forearc basin: Insights into the long‐term behaviour of the Lesser Antilles subduction zone          下载免费PDF全文

Jean‐Len Léticée  Mélody Philippon  Jean‐Jacques Cornée  Philippe Münch  Lyvane De Min  Mélanie Noury  Auran Randrianasolo  Jean‐Frédéric Lebrun 《地学学报》2017,29(4):245-252

In this study, we investigate the Lesser Antilles forearc basin, focusing on the late Pliocene to Pleistocene sedimentary archives in order to track the occurrence of extreme events triggered by enhanced subduction‐related tectono‐volcanic activity. We identify late Piacenzian deposits covering a major regional erosional surface, displaying sedimentary dykes and large marine boulders embedded in a mixed continental–marine matrix, characteristic of tsunamites. We interpret this episode of platform emersion and the successive cataclysmic deposits as resulting from enhanced tectonic activity at the interface of the subduction zone, synchronous with the initiation of the Lesser Antilles volcanic arc. We then discuss the implications in terms of the mechanical behaviour of the Lesser Antilles subduction zone.  相似文献   

Petroleum accumulation and leakage in a deeply buried carbonate reservoir,Níspero field (Mexico)     

Julien Bourdet  Jacques Pironon  Gilles Levresse  Jordi Tritlla 《Marine and Petroleum Geology》2010

The filling history of the Níspero deeply buried Lower Cretaceous carbonate reservoir (below 4000 m) from the south part of Gulf of Mexico was studied using a combination of data from petrography, stable isotopes and fluid inclusions and compared with a one-dimensional burial model to derive timing.  相似文献   

Multisite surface reaction versus transport control during the hydrolysis of a complex oxide     

Christophe Guy  Jacques Schott 《Chemical Geology》1989,78(3-4):181-204

Dissolution experiments of a tholeiite basalt glass carried out at different pH and T (up to 300°C) using a rotatingdisc apparatus show that, depending on pH and T, dissolution can be controlled by one of the following steps: (1) surface reaction; (2) transport of reactants in solution; and (3) mixed reaction. The activation energies of these different processes were found to be 60, 9 and 15–50 kJ mol⁻¹, respectively. Taking account of these results, it appears likely that surface reactions are not rate limiting for the hydrolysis of most crystalline silicate minerals in hydrothermal and metamorphic processes, and that caution should be exercised when predicting rate of reactions at high temperatures solely on the basis of activation energies measured at low temperatures.

Comparison of experimental and theoretical potentiometric titrations of the basalt glass and its constituent oxides indicates that the adsorption of H⁺ and OH⁻ ions at the basalt surface is metal cation specific and that the net adsorption can be predicted from the sole knowledge of the acidity constants of the network-forming constituent oxides. We found that in the acidic pH region dissolution is promoted by the adsorption of H⁺ on al and Fe surface sites while in the basic region, dissolution is promoted by the adsorption of OH⁻ on Si sites. The combination of the two distinct types of surface sites, Al and Fe on the one hand, and Si on the other hand, results in a dissolution rate minimum at a pH-value between the pH_zpc of the two groups of oxide components. Linear regressions with a slope n=3.8 are observed both in acid and alkaline solutions in logarithmic plots of the rate of dissolution vs. the surface charge. The value of n, which represents the number of protonation or hydroxylation steps prior to metal detachment, has been found equal to the mean valence of the network-forming metals.

Combining concepts of surface coordination chemistry with transition state theory afforded characterisation of the activated complexes involved in basalt dissolution processes. From the values obtained for the thermodynamic properties of activation for basalt dissolution it is assumed that the activated complexes formed during the H₂O-promoted dissolution of the basalt glass are more tightly bonded than those formed during H⁺- or OH⁻-promoted dissolution.  相似文献   

Gravimetry on the Erimo Seamount, Japan     

Jacques Dubois  Christine Deplus   《Tectonophysics》1989,160(1-4):267-275

A gravimetric survey on the sea-bottom was performed on the Erimo Seamount by the French submersible “Nautile”. It took place during the second phase of the Kaiko French-Japanese Program. The reference station was established on the Erimo submarine observatory at a depth of 3942 m and from this point the survey of four stations was carried out. The obtained accuracy of the gravity field measurements was about 0.1 mGal.

A three-dimensional model of the seamount and its surroundings was constrained by the free-air anomaly values from the sea surface and from the sea bottom and by the perfect Seabeam topography survey of the whole area. The model which fitted the observed values best, allowed us to identify a low-density layer of coral limestones and volcaniclastics capping the seamount and to define the geometry of the interface between basalts and coral rocks.  相似文献