Flexural response of the oceanic lithosphere at an arc—arc junction: implication for the subduction of aseismic ridges     

Christine Deplus  Jacques Dubois 《Tectonophysics》1989,160(1-4):63-73

The deformation of the oceanic lithosphere subducting at the junction of two trenches is studied by means of a three-dimensional finite-element analysis. Results show that the existence of a junction (i.e. a change in trend of the trench axis) yields a specific shape of the outer topographic rise. In a convex junction area—such as the Japan and Kuril trenches, the topographic bulge presents a “dome”, whereas in a concave junction area—such as the Java and Sumatra trenches, this bulge is less pronounced. These theoretical results are confirmed by the bathymetry seaward of the junctions of the Japan and Kuril trenches and of the Peru-Chile trench. Moreover, the existence of the abnormal topographic dome in front of a convex junction contributes to the creation of normal faults which help the subduction of seamounts or of other bathymetric features in such areas.  相似文献   

The Japan Trench and its juncture with the Kuril Trench: cruise results of the Kaiko project, Leg 3     

Jean-Paul Cadet  Kazuo Kobayashi  Jean Aubouin  Jacques Boulgue  Christine Deplus  Jacques Dubois  Roland von Huene  Laurent Jolivet  Toshihiko Kanazawa  Junzo Kasahara  Kinichiro Koizumi  Serge Lallemand  Yasuo Nakamura  Guy Pautot  Kiyoshi Suyehiro  Shin Tani  Hidekazu Tokuyama  Toshitsugu Yamazaki 《Earth and Planetary Science Letters》1987,83(1-4)

This paper presents the results of a detailed survey combining Seabeam mapping, gravity and geomagnetic measurements as well as single-channel seismic reflection observations in the Japan Trench and the juncture with the Kuril Trench during the French-Japanese Kaiko project (northern sector of the Leg 3) on the R/V “Jean Charcot”. The main data acquired during the cruise, such as the Seabeam maps, magnetic anomalies pattern, and preliminary interpretations are discussed. These new data cover an area of 18,000 km² and provide for the first time a detailed three-dimensional image of the Japan Trench. Combined with the previous results, the data indicate new structural interpretations. A comparative study of Seabeam morphology, single-channel and reprocessed multichannel records lead to the conclusion that along the northern Japan Trench there is little evidence of accretion but, instead, a tectonic erosion of the overriding plate. The tectonic pattern on the oceanic side of the trench is controlled by the creation of new normal faults parallel to the Japan Trench axis, which is a direct consequence of the downward flexure of the Pacific plate. In addition to these new faults, ancient normal faults trending parallel to the N65° oceanic magnetic anomalies and oblique to the Japan trench axis are reactivated, so that two directions of normal faulting are observed seaward of the Japan Trench. Only one direction of faulting is observed seaward of the Kuril Trench because of the parallelism between the trench axis and the magnetic anomalies. The convergent front of the Kuril Trench is offset left-laterally by 20 km relative to those of the Japan Trench. This transform fault and the lower slope of the southernmost Kuril Trench are represented by very steep scarps more than 2 km high. Slightly south of the juncture, the Erimo Seamount riding on the Pacific plate, is now entering the subduction zone. It has been preceded by at least another seamount as revealed by magnetic anomalies across the landward slope of the trench. Deeper future studies will be necessary to discriminate between the two following hypothesis about the origin of the curvature between both trenches: Is it due to the collision of an already subducted chain of seamounts? or does it correspond to one of the failure lines of the America/Eurasia plate boundary?  相似文献   

Multibody approach for reactive transport modeling in discontinuous-heterogeneous porous media     

Socié  Adrien  Dubois  Frédéric  Monerie  Yann  Perales  Frédéric 《Computational Geosciences》2021,25(5):1473-1491

Computational Geosciences - In the context of long-term degradation of porous media, the coupling between fracture mechanics and reactive transport is investigated. A reactive transport model in a...  相似文献   

Isostatic response of the large-offset Atlantic Equatorial fracture zones     

Michel Diament  Jean-Claude Sibuet  Jacques Dubois 《Marine Geophysical Researches》1986,8(3):243-264

Spectral analysis techniques have been applied to data sets of gravity and topography selected across fracture zones with large offset in the Equatorial and Central Atlantic Ocean and processed independently for each fracture zone. Three simple compensation models, two in local isostatic equilibrium (Airy I and II) and one in regional equilibrium (Plate model) have been tested. It is found that the free-air anomalies are primarily controlled by the topography and its isostatic response. For short wavelengths, admittance can be explained either by the effect of uncompensated sea floor topography with high density basement or by the effect of uncompensated sea floor topography with normal oceanic basement density but accompanied by a crust of constant thickness. For intermediate wavelengths, admittance for the Romanche fracture zone agrees best with a local isostatic model in which compensation is achieved by a less dense material in the upper mantle. No such evidence exists for the Vema and Chain fracture zones for which topography could just as well be regionally supported by an elastic plate 3 to 10 km thick. For longer wavelengths, the admittances computed for the three fracture zones are compatible with a thermal compensation of the topography.  相似文献   

Bathymetry of the mid-atlantic ridge, 24°-31°N: A map series     

G. M. Purdy  J. -C. Sempere  H. Schouten  D. L. Dubois  R. Goldsmith 《Marine Geophysical Researches》1990,12(4):247-252

This paper presents a series of eleven maps of the bathymetry of a 900 km long section of the crestal region of the Mid-Atlantic Ridge. Along with a twelfth key map, this series defines the morphology of fifteen discrete spreading segments and shows convincingly that no transform faults exist between the Kane and Atlantis fracture zones. The publication of these multi beam bathymetry data with a contour interval of 50 m and at a scale of 30 inches per degree of longitude is intended to allow easy access by a broad community of marine earth scientists to this unique and powerful data set.  相似文献   

Modelling larval dispersal and settlement of the reef-building polychaete Sabellaria alveolata: Role of hydroclimatic processes on the sustainability of biogenic reefs     

Sakina-Dorothée Ayata  Céline Ellien  Franck Dumas  Stanislas Dubois  Éric Thiébaut 《Continental Shelf Research》2009

The honeycomb worm Sabellaria alveolata forms biogenic reefs which constitute diversity hotspots on tidal flats. The largest known reefs in Europe, located in the Bay of Mont-Saint-Michel (English Channel), are suffering increasing anthropogenic disturbances which raise the question of their sustainability. As the ability to recover depends partly on the recolonization of damaged reefs by larval supply, evaluating larval dispersal and the connectivity between distant reefs is a major challenge for their conservation. In the present study, we used a 3D biophysical model to simulate larval dispersal under realistic hydroclimatic conditions and estimate larval retention and exchanges among the two reefs of different sizes within the bay. The model takes into account fine-scale hydrodynamic circulation (800×800 m²), advection–diffusion larval transport, and gregarious settlement behaviour. According to the field data, larval dispersal was simulated for a minimal planktonic larval duration ranging from 4 to 8 weeks and the larval mortality was set to 0.09 d⁻¹. The results highlighted the role played by a coastal eddy on larval retention within the bay, as suggested by previous in situ observations. Very different dispersal patterns were revealed depending on the spawning reef location, although the two reefs were located only 15 km apart. The settlement success of the larvae released from the smallest reef was mainly related to tidal conditions at spawning, with the highest settlement success for releases at neap tide. The settlement success of the larvae from the biggest reef was more dependent on meteorological conditions: favourable W and SW winds may promote a ten-fold increase in settlement success. Strong year-to-year variability was observed in settlers’ numbers, with favourable environmental windows not always coinciding with the main reproductive periods of Sabellaria. Settlement kinetics indicated that the ability to delay metamorphosis could significantly improve the settlement success. Although bidirectional exchanges occurred between the two reefs, the highest settlers’ numbers originated from the biggest reef because of its stronger reproductive output. Because of the recent decline of this reef due to increasing anthropogenic disturbances larval supply in the bay may not be sufficient enough to ensure the sustainability of the remarkable habitat formed by Sabellaria alveolata reefs.  相似文献   

Testing asynchronous coupling on simple “ocean-atmosphere” dynamic systems     

M. A. Dubois  P. Yiou 《Climate Dynamics》1999,15(1):1-7

 Simulations of long-term climatic variations require the use of coupled oceanic and atmospheric models. Given their different scales in space and time and present computing limitations, asynchronous coupling schemes are often used. Comparing the evolutions of simple dynamic systems which we couple alternatively with synchronous and asynchronous schemes, we show that the behaviour can be modified, not only in minute details, but drastically, if asynchronous coupling is used with insufficient care. We study how it happens, then suggest methods to insure that the average behaviour of more realistic models is not modified with asynchronous schemes. Other branches of physics with coupled non-linear systems could make use of these remarks. Received: 19 February 1997 / Accepted: 17 June 1998  相似文献   

雅鲁藏布江蛇绿岩再研究:从地质调查到矿物记录   总被引：9，自引：0，他引：9  

王成善  李亚林  刘志飞  李祥辉  唐菊兴  REJEAN Hebert  COTE Dubois  VARFALVY V  HUOT F 《地质学报》2005,79(3):323-330

蛇绿岩带出现于全球大多数碰撞构造带上,通常是板块缝合带的标志,西藏雅鲁藏布江缝合带蛇绿岩带对于此种概念模型是毫无争议的。根据近年来现代洋壳和蛇绿岩研究成果以及分析技术,在20世纪80年代中法合作项目研究成果基础上,笔者再次对西起日喀则拉孜、东至泽当金鲁,长约500km的雅鲁藏布江缝合带蛇绿岩进行了研究。在野外调查基础上,对雅鲁藏布江蛇绿岩中500多个尖晶石样品的地球化学特征进行了分析研究,以探讨蛇绿岩的成因及其动力学背景,提出雅鲁藏布江蛇绿岩带属于超俯冲作用(suprasubduction)的产物,与近年来其他研究成果的认识一致。  相似文献   

Future projections of the surface heat and water budgets of the Mediterranean Sea in an ensemble of coupled atmosphere–ocean regional climate models     

C. Dubois  S. Somot  S. Calmanti  A. Carillo  M. Déqué  A. Dell’Aquilla  A. Elizalde  S. Gualdi  D. Jacob  B. L’Hévéder  L. Li  P. Oddo  G. Sannino  E. Scoccimarro  F. Sevault 《Climate Dynamics》2012,39(7-8):1859-1884

Within the CIRCE project “Climate change and Impact Research: the Mediterranean Environment”, an ensemble of high resolution coupled atmosphere–ocean regional climate models (AORCMs) are used to simulate the Mediterranean climate for the period 1950–2050. For the first time, realistic net surface air-sea fluxes are obtained. The sea surface temperature (SST) variability is consistent with the atmospheric forcing above it and oceanic constraints. The surface fluxes respond to external forcing under a warming climate and show an equivalent trend in all models. This study focuses on the present day and on the evolution of the heat and water budget over the Mediterranean Sea under the SRES-A1B scenario. On the contrary to previous studies, the net total heat budget is negative over the present period in all AORCMs and satisfies the heat closure budget controlled by a net positive heat gain at the strait of Gibraltar in the present climate. Under climate change scenario, some models predict a warming of the Mediterranean Sea from the ocean surface (positive net heat flux) in addition to the positive flux at the strait of Gibraltar for the 2021–2050 period. The shortwave and latent flux are increasing and the longwave and sensible fluxes are decreasing compared to the 1961–1990 period due to a reduction of the cloud cover and an increase in greenhouse gases (GHGs) and SSTs over the 2021–2050 period. The AORCMs provide a good estimates of the water budget with a drying of the region during the twenty-first century. For the ensemble mean, he decrease in precipitation and runoff is about 10 and 15% respectively and the increase in evaporation is much weaker, about 2% compared to the 1961–1990 period which confirm results obtained in recent studies. Despite a clear consistency in the trends and results between the models, this study also underlines important differences in the model set-ups, methodology and choices of some physical parameters inducing some difference in the various air-sea fluxes. An evaluation of the uncertainty sources and possible improvement for future generation of AORCMs highlights the importance of the parameterisation of the ocean albedo, rivers and cloud cover.  相似文献   

Can pelagic net heterotrophy account for carbon fluxes from eastern Canadian lakes?     

Kristal Dubois  Richard Carignan  Ján Veizer 《Applied Geochemistry》2009

Lakes worldwide are commonly oversaturated with CO₂, however the source of this CO₂ oversaturation is not well understood. To examine the magnitude of the C flux to the atmosphere and determine if an excess of respiration (R) over gross primary production (GPP) is sufficient to account for this C flux, metabolic parameters and stable isotopes of dissolved O₂ and C were measured in 23 Québec lakes. All of the lakes sampled were oversaturated with CO₂ over the sampling period, on average 221 ± 25%. However, little evidence was found to conclude that this CO₂ oversaturation was the result of an excess of pelagic R over GPP. In lakes Croche and à l’Ours, where CO₂ flux, R and GPP were measured weekly, the annual difference between pelagic GPP and R, or net primary production (NPP), was not sufficient to account for the size of the CO₂ flux to the atmosphere. In Lac Croche average annual NPP was 14.4 mg C m⁻² d⁻¹ while the average annual flux of CO₂ to the atmosphere was 34 mg C m⁻² d⁻¹. In Lac à l’Ours average annual NPP was −9.1 mg C m⁻² d⁻¹ while the average annual flux of CO₂ to the atmosphere was 55 mg C m⁻² d⁻¹. In all of the lakes sampled, O₂ saturation averaged 104.0 ± 1.7% during the ice-free season and the isotopic composition of dissolved O₂ (δ¹⁸O_DO) was 22.9 ± 0.3‰, lower than atmospheric values and indicative of net autotrophy. Carbon evasion was not a function of R, nor did the isotopic signature of dissolved CO₂ in the lakes present evidence of excess R over GPP. External inputs of C must therefore subsidize the lake to explain the continued CO₂ oversaturation. The isotopic composition of dissolved inorganic C (δ¹³C_DIC) indicates that the CO₂ oversaturation cannot be attributed to in situ aerobic respiration. δ¹³C_DIC reveals a source of excess C enriched in ¹³C, which may be accounted for by anaerobic sediment respiration or groundwater inputs followed by kinetic isotope fractionation during degassing under open system conditions.  相似文献