排序方式： 共有10条查询结果，搜索用时 78 毫秒
1
1.
K. Perrot J. Francheteau M. Maia C. Tisseau 《Earth and Planetary Science Letters》1998,160(3-4):593-607
The distributions of crustal depths as a function of age have been analysed for the southeast Pacific region, along the East Pacific Rise, between the Equator and the Easter microplate (23°S). Using age data and a new compilation of bathymetric data, subsidence rates (for both eastern and western flanks), asymmetry of subsidence and zero-age depths, are computed within flow-line corridors on the Nazca and Pacific plates. Variations of subsidence rates, axial depths and subsidence asymmetry are examined both in space (within corridors) and time (within several age intervals). The variability in these parameters along the strike of the East Pacific Rise is systematic and serves to define several orders of ridge segmentation. The largest variations of these parameters are correlated with the large-scale segmentation of the ridge axis (i.e. transform faults and very large overlapping spreading centres) and are interpreted as related to variations in mantle heterogeneities mainly dependent upon temperature. Smaller variations of subsidence parameters are correlated with second- (and sometimes third-) order segmentation of the ridge axis, which could be related to variations in axial magmatic supply. Across-strike variations of subsidence suggest the existence of small lateral temperature and density variations in the mantle. When analysing the slope of the distribution of depth versus square root of age within corridors, we have observed the existence of changes in the slope which occur at specific age limits. We have estimated the subsidence over different age ranges in order to determine the temporal evolution of subsidence parameters (rates and asymmetry). Such an analysis may inform on the past axial segmentation and on the persistence of axial discontinuities in time. A linear relationship between subsidence rates and axial depths is determined for each age range and suggests that shallower segments subside faster than deeper segments. Although a similar, statistically defined linear relationship exists for any mid-ocean spreading ridge (both for intermediate or fast–ultrafast spreading), the resultant slopes of this relationship vary from ocean to ocean and show that this relationship is not universal over all oceans. 相似文献
2.
V. V. Mordvinova A. Deschamps T. Dugarmaa J. Deverchére M. Ulziibat V. A. Sankov A. A. Artem’ev J. Perrot 《Izvestiya Physics of the Solid Earth》2007,43(2):119-129
The S wave velocity distribution in the Earth’s crust and the first two hundred kilometers of the upper mantle is inferred from data of a seismological linear network including 18 broadband stations installed in the framework of the international teleseismic experiment carried out in 2003 in the south of Siberia and in Mongolia. Models were constructed by using P-to-S received function inversion beneath each station. Vertical cross sections of S wave velocities from the surface to depths of 65 and 270 km covering the entire 1000-km profile are constructed by the linear spline interpolation of individual velocity models. The vertical sections are also represented as anomalies relative to the standard velocity model. The most intense low velocity anomalies (from ?3 to ?6%) in the crust and upper mantle are identified beneath the Sayan, Khamar-Daban, and Khangai highlands and the Djida fold zone and agree both with other geophysical data and with the distribution of Late Cenozoic volcanic fields. The results of this work suggest that the activation of Mongolian-Siberian highlands is largely connected with uplift of the asthenosphere to the base of the crust. 相似文献
3.
—On May 25th, 1992, an M s = 6.9 earthquake occurred off the southwestern tip of Cuba, along the boundary between the Caribbean and North American plates. This earthquake was the largest to strike southern Cuba since 1917 and the largest ever recorded in that region by global seismic networks. It is therefore a key element for our understanding of the tectonic and kinematic regime along the northern Caribbean plate boundary. In order to test the previously proposed source parameters of the Cabo Cruz earthquake and to better constrain its focal mechanism, we derived a new set of source parameters from unfiltered broad-band teleseismic records. We used a hybrid ray tracing method that allows us to take into account propagation effects of seismic waves in a realistic crustal model around the source. Our solution is consistent with the long-period focal mechanism solution of Virieux et al. (1992). Our solution also models the higher frequency crustal and water layer phases. The primarily strike-slip focal mechanism has a small thrust component. Its shows an east-west trending nodal plane dipping 55° to the north that we interpret as the rupture plane since it corresponds to the geometry of the major active fault in that area. The displacement on this plane is a left-lateral strike-slip combined with a small amount of southward thrust. The result is in good agreement with the active tectonic structures observed along the Oriente fault south of Cuba. The small thrust component demonstrates that, contrary to prior belief, the transpressive regime extends along this whole segment of the Caribbean/North American plate boundary. Together with historical seismicity, it suggests that most of the stress accumulated by the Caribbean/North American plate motion is released seismically along the southern Cuban margin during relatively few but large earthquakes. 相似文献
4.
Morgann Perrot Alain Tremblay Gilles Ruffet Loic Labrousse Félix Gervais Fabien Caroir 《Journal of Metamorphic Geology》2020,38(1):3-27
The Connecticut Valley–Gaspé (CVG) trough represents a major, orogen-scale Silurian–Devonian basin of the Northern Appalachians. From Gaspé Peninsula to southern New England, the CVG trough has experienced a contrasting metamorphic and structural evolution during the Acadian orogeny. Along its strike, the CVG trough is characterized by increasing strain and polyphase structures, and by variations in the intensity of regional metamorphism and contrasting abundance of c. 390–370 Ma granitic intrusions. In southern Quebec and northern Vermont, a series of NW–SE transects across the CVG trough have been studied in order to better understand these along-strike variations. Detailed structural analyses, combined with phase equilibria modelling, Raman spectrometry, and muscovite 40Ar/39Ar dating highlight a progressive and incremental deformation involving south–north variation in the timing of metamorphism. Deformation evolves from a D1 crustal thickening event which originates in Vermont and progresses to southern Québec where it peaked at 0.6 GPa/380°C at c. 375 Ma. This was followed by a D2 event associated with continuous burial in Vermont from 378 to 355 Ma, which produced peak metamorphic conditions of 0.85 GPa/380°C and exhumation in Quebec from 368 to 360 Ma. The D3 compressional exhumation event also evolved from south to north from 345 to 335 Ma. D1 to D3 deformation events form part of a continuum with an along-strike propagation rate of ~50 km/Ma During D1, the burial depth varied by more than 15 km between southern Quebec and Vermont, and this can be attributed to the occurrence of a major crustal indenter, the Bronson Hill Arc massif, in the New England segment of the Acadian collision zone. 相似文献
5.
6.
P. L. Gonthier R. Van Guilder A. K. Harding I. A. Grenier C. A. Perrot 《Astrophysics and Space Science》2005,297(1-4):71-80
We present results of a population synthesis study of radio-loud and radio-quiet γ-ray pulsars from the Galactic plane and
the Gould Belt. The simulation includes the Parkes multibeam pulsar survey, realistic beam geometries for radio and γ-ray
emission from neutron stars and the new electron density model of Cordes and Lazio. Normalizing to the number of radio pulsars
observed by a set of nine radio surveys, the simulation suggests a neutron star birth rate of 1.4 neutron stars per century
in the Galactic plane. In addition, the simulation predicts 19 radio-loud and 7 radio-quiet γ-ray pulsars from the plane that
EGRET should have observed as point sources. Assuming that during the last 5 Myr the Gould Belt produced 100 neutron stars,
only 10 of these would be observed as radio pulsars with three radio-loud and four radio-quiet γ-ray pulsars observed by EGRET.
These results are in general agreement with the recent number of about 25 EGRET error boxes that contain Parkes radio pulsars.
Since the Gould Belt pulsars are relatively close by, the selection of EGRET radio-quiet γ-ray pulsars strongly favors large
impact angles, β, in the viewing geometry where the off-beam emission from curvature radiation provides the γ-ray flux. Therefore,
the simulated EGRET radio-quiet γ-ray pulsars, being young and nearby, most closely reflect the current shape of the Gould
Belt suggesting that such sources may significantly contribute to the EGRET unidentified γ-ray sources correlated with the
Gould Belt. 相似文献
7.
8.
On the failure of a discrete axial chain using a continualized nonlocal Continuum Damage Mechanics approach 
下载免费PDF全文
下载免费PDF全文 The failure of a discrete elastic‐damage axial system is investigated using both a discrete and an equivalent continuum approach. The Discrete Damage Mechanics approach is based on a microstructured model composed of a series of periodic elastic‐damage springs (axial Discrete Damage Mechanics lattice system). Such a discrete damage system can be associated with the finite difference formulation of a Continuum Damage Mechanics evolution problem. Several analytical and numerical results are presented for the tensile failure of this axial damage chain under its own weight. The nonlocal Continuum Damage Mechanics models examined in this paper are mainly built from a continualization procedure applied to centered or uncentered finite difference schemes. The asymptotic expansion of the first‐order upward difference equations leads to a first‐order nonlocal model, whereas the asymptotic expansion of the centered finite difference equations leads to a second‐order nonlocal Eringen's approach. To complete this study, a phenomenological nonlocal gradient approach is also examined and compared with the first continualization methods. A comparison of the discrete and the continuous problems for the chains shows the effectiveness of the new micromechanics‐based nonlocal Continuum Damage modeling, especially for capturing scale effects. For both continualized approaches, the length scale of the nonlocal models depends only on the cell size, while for the so‐called phenomenological approach, the length scale may depend on the loading parameter. This apparent load‐dependent length scale, already discussed in the literature with numerical arguments, is found to be sensitive to the postulated structure of the nonlocal model calibrated according to a lattice approach. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
9.
10.
From rifting to spreading in the eastern Gulf of Aden: a geophysical survey of a young oceanic basin from margin to margin 总被引：1，自引：0，他引：1
Sylvie Leroy Pascal Gente Marc Fournier Elia d'Acremont Philippe Patriat Marie-Odile Beslier Nicolas Bellahsen Marcia Maia Angelina Blais Julie Perrot Ali Al-Kathiri Serge Merkouriev Jean-Marc Fleury Pierre-Yves Ruellan Claude Lepvrier Philippe Huchon 《地学学报》2004,16(4):185-192
A geophysical survey in the eastern Gulf of Aden, between the Alula–Fartak (52°E) and the Socotra (55°E) transform faults, was carried out during the Encens–Sheba cruise. The conjugate margins of the Gulf are steep, narrow and asymmetric. Asymmetry of the rifting process is highlighted by the conjugate margins (horst and graben in the north and deep basin in the south). Two transfer fault zones separate the margins into three segments, whereas the present‐day Sheba Ridge is divided into two segments by a transform discontinuity. Therefore segmentation of the Sheba Ridge and that of the conjugate margins did coincide during the early stages of oceanic spreading. Extensive magma production is evidenced in the central part of the western segment. Anomaly 5d was identified in the northern and southern parts of the oceanic basin, thus confirming that seafloor spreading in this part of Gulf of Aden started at least 17.6 Ma ago. 相似文献
1