La question foncière a fait, à la faveur de la hausse historique des prix, un retour en force su... more La question foncière a fait, à la faveur de la hausse historique des prix, un retour en force sur la scène de l'aménagement en Ile-de-france. Planification, grands projets, coopérations métropolitaines, établissements publics foncier, les initiatives en faveur d'une "meilleure maîtrise" du foncier régional ne manquent pas.... Entre difficultés réelles et fantasmées, cet ouvrage propose de faire le point sur dix idées reçues, dix questions pour dix auteurs, chercheurs ou praticiens, pour une approche à la fois académique et pratique d'une question au coeur des problèmatiques d'aménagement aujourd'hui et de demain
Le Pichon, X., Lyb&is, N., Angelier, J. and . Strain distribution over the east Mediterranean rid... more Le Pichon, X., Lyb&is, N., Angelier, J. and . Strain distribution over the east Mediterranean ridge: a synthesis incorporating new Sea-Beam data. In: X. Le Pichon, S.S. Augustithis and J. Mar&e (Editors), Geodynamics of the Hellenic Arc and Trench. Tect~~physies, 86: 243-274.
Kaiko surveys over the Nankai Trough made available new magnetic and structural data for the nort... more Kaiko surveys over the Nankai Trough made available new magnetic and structural data for the northern Shikoku Basin. A survey of the oceanic lithosphere subducting below Southwest Japan along the central Nankai Trough revealed the existence of several north-south basement troughs. They are probably transform faults related to a north-south spreading system. We examine the possibility of a late phase of north-south spreading limited to the axial northernmost Shikoku Basin, active between 14 and 12 Ma. If this system was already active before that time, i.e. during the N55° opening of the southeastern basin, then a triple junction should be found between both areas. Based on these data and previous studies we present a new interpretation of magnetic anomalies over the whole basin. From early east-west rifting to late north-south spreading, opening of the Shikoku Basin proceeded through multiple episodes of spreading. The analysis of magnetic anomalies constrains the kinematic evolution of the basin through time and space. Two successive counter-clockwise rotations of the spreading direction are postulated, at anomaly 6 (19 Ma) and at anomaly 5B (14 Ma), involving segmentation and rotation of the spreading ridge.
Detailed bathymetric investigations were performed in four zones of the Hellenic trench system in... more Detailed bathymetric investigations were performed in four zones of the Hellenic trench system in 1978, using the multi-narrow beam echo-sounder "Sea-Beam" on R.V. "Jean Charcot". In 1979, a field-study using the 3000 m submersible "Cyana" was conducted in three of the four sites covered by Sea-Beam. We summarize here the principal tectonic results of these studies and publish the corresponding Sea-Beam maps. It is shown that compressional structures affect the sedimentary cover of the outer wall and trench whereas extensional tectonics is present on the inner wall. In addition, there is evidence that most of the upper sedimentary cover is not subducted but rather piles up in front of the trench to form the Mediterranean ridge. We suggest that the surface limit of the zone of mechanical decoupling occurs near the base of the inner wall. We show that the gross structure of the trench as well as the strain pattern observed is controlled by the kinematics of subduction and we discuss its evolution since its initiation about 13 m.y. ago.
We present the study of the magnetoresitance (MR) in a two dimensional electron gas in a Si/SiGe ... more We present the study of the magnetoresitance (MR) in a two dimensional electron gas in a Si/SiGe heterostructure. We show that the sign of this MR can change with temperature depending on the sample. We analyze the observed magnetoresistance in terms of the recent theory of interaction induced MR (Phys. Rev. B, 69, 045313 (2003)).
Huchon, P., Lybtris, N., Angelier, J., Le Pichon, X. and . Tectonics of the Hellenic trench: a sy... more Huchon, P., Lybtris, N., Angelier, J., Le Pichon, X. and . Tectonics of the Hellenic trench: a synthesis of "Sea-Beam" and submersible observations. In: X. Le Pichon, S.S. Augustithis and J. Mascle (Editors), Geodynamics of the Hellenic Arc and Trench. Tectonophysics, 86: 69-112.
We present deep penetration seismic time sections obtained in the last two years with the "single... more We present deep penetration seismic time sections obtained in the last two years with the "single-bubble" pulse generating method using marine seismic airguns. Whole crustal penetration and resolution have been obtained on the Ionian quasi oceanic basin and its margin, on the continental crust of the Aegean Sea, on the continental margins, and oceanic basin of the Gulf of Biscay. We show that this method is more efficient than others in radiating the lower frequencies returned by deep structure, without loosing resolution. Hence it allows deep crustal imaging from relatively low-power academic ships, and if the method is applied to powerful industrial vessels, it may open the subcrustal lithosphere to imaging.
Physica E: Low-dimensional Systems and Nanostructures, 2004
... Corresponding Author , a , c , EB Olshanetky b , ZD Kvon b , JC Portal a , c , d , NJ Woods e... more ... Corresponding Author , a , c , EB Olshanetky b , ZD Kvon b , JC Portal a , c , d , NJ Woods e , J. Zhang f and JJ Harris f. ... 8. YY Proskuryakov, AK Savchenko, SS Safonov, M. Pepper, MY Simons and DA Ritchie. ... E. Abrahams, PW Anderson, DC Licciardello and TV Ramakrishnan. ...
The Barents Sea is underlain by a thick (up t o 5 km) sedimentary basin. Seismic refraction has o... more The Barents Sea is underlain by a thick (up t o 5 km) sedimentary basin. Seismic refraction has outlined four main velocity discontinuities which have been correlated with geological units o n the basis of the geological history of the region. The basin is underlain by a crystalline basement, the nature of which cannot be determined on the basis of seismic velocity alone. Metamorphosed Paleozoic units (velocities around 5-4 km/sec) lie over this basement. Their thickness is not well established but appears to reach 1 or 2 km in some cases. Avery distinct and thick (up to 2.5 km) layer (4.1 km/sec) is found almost everyurhere and is thought t o correspond to a major discontinuity at the end o t the Paleozoic. This discontinuity is followed by a variable velocity layer (2.4-4 kmlsec, up to 1.2 km thick) which includes Mesozoic and Cenozoic sediments and is limited to the south of the Barents Sea. The absence of thick Tertiary deposits support the idea that the Barents shelf was emergent at that time. Recent low-velocity sediments are found close to the shelf edge. -Gravity anomaly trends reflect a series of depressions of the 5.4-km/sec layer isobath map and suggest that the deeper part of the basin is made of a succession of faulted blocks or intense folds. * Contribution no. 274 of the Département Scientifique, Centre Océanologique de Bretagne.
... Printed in The Netherlands [5J FROM SUBDUCTION TO TRANSFORM MOTION A SEABEAM SURVEY OF THE HE... more ... Printed in The Netherlands [5J FROM SUBDUCTION TO TRANSFORM MOTION A SEABEAM SURVEY OF THE HELLENIC TRENCH SYSTEM XAVIER LE PICHON 1 ... Region, Athens, 1977 (in press) 6 P Le Quellec, J Mascle, J Vittori, H Got and L Mirabile, La fosse de Matapan ...
The Kaiko project was a French-Japanese cooperative scientific effort to investigate the structur... more The Kaiko project was a French-Japanese cooperative scientific effort to investigate the structures and geodynamic processes in the deep trenches surrounding the Japanese islands. Seabeam mapping, as well as detailed geophysical investigation of eight selected areas in the Nankai, Suruga and Sagami Troughs and in the Japan Trench, including the trench triple junction, were performed in 1984. Twenty-seven manned dives, to a maximum depth of 6000 m, were made over five of these areas at carefully selected sites in 1985. The main results of the project are presented in this special issue together with a set of coloured bathymetric maps and block diagrams. They illustrate a great diversity of tectonic styles, from the turbidite-filled trenches of the Shikoku Basin with a well developed accretionary prism, to the much deeper Japan Trench with widespread evidence for large-scale slumping and erosion over the inner wall. Special insight has been gained into the processes involved in the subduction of seamounts and of volcanic ridges. Benthic communities, associated with chemosynthetic processes, were discovered at several locations during manned dives in the Nankai Trough as well as in the Japan Trench. They thus appear to be a common feature of deep-sea trenches. Thermal, geochemical and biogeochemical measurements, coupled with tectonic observations, indicate that they are related to overpressure fluid advections along zones of active surface deformation.
Kaiko surveys over the Nankai Trough made available new magnetic and structural data for the nort... more Kaiko surveys over the Nankai Trough made available new magnetic and structural data for the northern Shikoku Basin. A survey of the oceanic lithosphere subducting below Southwest Japan along the central Nankai Trough revealed the existence of several north-south basement troughs. They are probably transform faults related to a north-south spreading system. We exanune the possibility of a late phase of north-south spreading limited to the axial northernmost Shikoku Basin, active between 14 and 12 Ma. If this system was already active before that time, i.e. during the N55 ° opening of the southeastern basin, then a triple junction should be found between both areas.
Abstract Recently, a new type of magnetoresistance oscillations beyond Shubinikov-de Hass (SdH) e... more Abstract Recently, a new type of magnetoresistance oscillations beyond Shubinikov-de Hass (SdH) effect have been observed in a plain high-mobility two-dimensional electron gas (2DEG) in GaAs-AlGaAs heterostructures [Zudov et al., APS Bulletin 44, 1572 (1999)]. Being periodic in 1/B these new oscillations appear at weak magnetic field (B< 0.3 T) and only in a narrow temperature range (3< T< 7 K), where SdH oscilations are already suppressed. Remarkably, these oscillations can be understood in terms of interaction of 2DEG and ...
La question foncière a fait, à la faveur de la hausse historique des prix, un retour en force su... more La question foncière a fait, à la faveur de la hausse historique des prix, un retour en force sur la scène de l'aménagement en Ile-de-france. Planification, grands projets, coopérations métropolitaines, établissements publics foncier, les initiatives en faveur d'une "meilleure maîtrise" du foncier régional ne manquent pas.... Entre difficultés réelles et fantasmées, cet ouvrage propose de faire le point sur dix idées reçues, dix questions pour dix auteurs, chercheurs ou praticiens, pour une approche à la fois académique et pratique d'une question au coeur des problèmatiques d'aménagement aujourd'hui et de demain
Le Pichon, X., Lyb&is, N., Angelier, J. and . Strain distribution over the east Mediterranean rid... more Le Pichon, X., Lyb&is, N., Angelier, J. and . Strain distribution over the east Mediterranean ridge: a synthesis incorporating new Sea-Beam data. In: X. Le Pichon, S.S. Augustithis and J. Mar&e (Editors), Geodynamics of the Hellenic Arc and Trench. Tect~~physies, 86: 243-274.
Kaiko surveys over the Nankai Trough made available new magnetic and structural data for the nort... more Kaiko surveys over the Nankai Trough made available new magnetic and structural data for the northern Shikoku Basin. A survey of the oceanic lithosphere subducting below Southwest Japan along the central Nankai Trough revealed the existence of several north-south basement troughs. They are probably transform faults related to a north-south spreading system. We examine the possibility of a late phase of north-south spreading limited to the axial northernmost Shikoku Basin, active between 14 and 12 Ma. If this system was already active before that time, i.e. during the N55° opening of the southeastern basin, then a triple junction should be found between both areas. Based on these data and previous studies we present a new interpretation of magnetic anomalies over the whole basin. From early east-west rifting to late north-south spreading, opening of the Shikoku Basin proceeded through multiple episodes of spreading. The analysis of magnetic anomalies constrains the kinematic evolution of the basin through time and space. Two successive counter-clockwise rotations of the spreading direction are postulated, at anomaly 6 (19 Ma) and at anomaly 5B (14 Ma), involving segmentation and rotation of the spreading ridge.
Detailed bathymetric investigations were performed in four zones of the Hellenic trench system in... more Detailed bathymetric investigations were performed in four zones of the Hellenic trench system in 1978, using the multi-narrow beam echo-sounder "Sea-Beam" on R.V. "Jean Charcot". In 1979, a field-study using the 3000 m submersible "Cyana" was conducted in three of the four sites covered by Sea-Beam. We summarize here the principal tectonic results of these studies and publish the corresponding Sea-Beam maps. It is shown that compressional structures affect the sedimentary cover of the outer wall and trench whereas extensional tectonics is present on the inner wall. In addition, there is evidence that most of the upper sedimentary cover is not subducted but rather piles up in front of the trench to form the Mediterranean ridge. We suggest that the surface limit of the zone of mechanical decoupling occurs near the base of the inner wall. We show that the gross structure of the trench as well as the strain pattern observed is controlled by the kinematics of subduction and we discuss its evolution since its initiation about 13 m.y. ago.
We present the study of the magnetoresitance (MR) in a two dimensional electron gas in a Si/SiGe ... more We present the study of the magnetoresitance (MR) in a two dimensional electron gas in a Si/SiGe heterostructure. We show that the sign of this MR can change with temperature depending on the sample. We analyze the observed magnetoresistance in terms of the recent theory of interaction induced MR (Phys. Rev. B, 69, 045313 (2003)).
Huchon, P., Lybtris, N., Angelier, J., Le Pichon, X. and . Tectonics of the Hellenic trench: a sy... more Huchon, P., Lybtris, N., Angelier, J., Le Pichon, X. and . Tectonics of the Hellenic trench: a synthesis of "Sea-Beam" and submersible observations. In: X. Le Pichon, S.S. Augustithis and J. Mascle (Editors), Geodynamics of the Hellenic Arc and Trench. Tectonophysics, 86: 69-112.
We present deep penetration seismic time sections obtained in the last two years with the "single... more We present deep penetration seismic time sections obtained in the last two years with the "single-bubble" pulse generating method using marine seismic airguns. Whole crustal penetration and resolution have been obtained on the Ionian quasi oceanic basin and its margin, on the continental crust of the Aegean Sea, on the continental margins, and oceanic basin of the Gulf of Biscay. We show that this method is more efficient than others in radiating the lower frequencies returned by deep structure, without loosing resolution. Hence it allows deep crustal imaging from relatively low-power academic ships, and if the method is applied to powerful industrial vessels, it may open the subcrustal lithosphere to imaging.
Physica E: Low-dimensional Systems and Nanostructures, 2004
... Corresponding Author , a , c , EB Olshanetky b , ZD Kvon b , JC Portal a , c , d , NJ Woods e... more ... Corresponding Author , a , c , EB Olshanetky b , ZD Kvon b , JC Portal a , c , d , NJ Woods e , J. Zhang f and JJ Harris f. ... 8. YY Proskuryakov, AK Savchenko, SS Safonov, M. Pepper, MY Simons and DA Ritchie. ... E. Abrahams, PW Anderson, DC Licciardello and TV Ramakrishnan. ...
The Barents Sea is underlain by a thick (up t o 5 km) sedimentary basin. Seismic refraction has o... more The Barents Sea is underlain by a thick (up t o 5 km) sedimentary basin. Seismic refraction has outlined four main velocity discontinuities which have been correlated with geological units o n the basis of the geological history of the region. The basin is underlain by a crystalline basement, the nature of which cannot be determined on the basis of seismic velocity alone. Metamorphosed Paleozoic units (velocities around 5-4 km/sec) lie over this basement. Their thickness is not well established but appears to reach 1 or 2 km in some cases. Avery distinct and thick (up to 2.5 km) layer (4.1 km/sec) is found almost everyurhere and is thought t o correspond to a major discontinuity at the end o t the Paleozoic. This discontinuity is followed by a variable velocity layer (2.4-4 kmlsec, up to 1.2 km thick) which includes Mesozoic and Cenozoic sediments and is limited to the south of the Barents Sea. The absence of thick Tertiary deposits support the idea that the Barents shelf was emergent at that time. Recent low-velocity sediments are found close to the shelf edge. -Gravity anomaly trends reflect a series of depressions of the 5.4-km/sec layer isobath map and suggest that the deeper part of the basin is made of a succession of faulted blocks or intense folds. * Contribution no. 274 of the Département Scientifique, Centre Océanologique de Bretagne.
... Printed in The Netherlands [5J FROM SUBDUCTION TO TRANSFORM MOTION A SEABEAM SURVEY OF THE HE... more ... Printed in The Netherlands [5J FROM SUBDUCTION TO TRANSFORM MOTION A SEABEAM SURVEY OF THE HELLENIC TRENCH SYSTEM XAVIER LE PICHON 1 ... Region, Athens, 1977 (in press) 6 P Le Quellec, J Mascle, J Vittori, H Got and L Mirabile, La fosse de Matapan ...
The Kaiko project was a French-Japanese cooperative scientific effort to investigate the structur... more The Kaiko project was a French-Japanese cooperative scientific effort to investigate the structures and geodynamic processes in the deep trenches surrounding the Japanese islands. Seabeam mapping, as well as detailed geophysical investigation of eight selected areas in the Nankai, Suruga and Sagami Troughs and in the Japan Trench, including the trench triple junction, were performed in 1984. Twenty-seven manned dives, to a maximum depth of 6000 m, were made over five of these areas at carefully selected sites in 1985. The main results of the project are presented in this special issue together with a set of coloured bathymetric maps and block diagrams. They illustrate a great diversity of tectonic styles, from the turbidite-filled trenches of the Shikoku Basin with a well developed accretionary prism, to the much deeper Japan Trench with widespread evidence for large-scale slumping and erosion over the inner wall. Special insight has been gained into the processes involved in the subduction of seamounts and of volcanic ridges. Benthic communities, associated with chemosynthetic processes, were discovered at several locations during manned dives in the Nankai Trough as well as in the Japan Trench. They thus appear to be a common feature of deep-sea trenches. Thermal, geochemical and biogeochemical measurements, coupled with tectonic observations, indicate that they are related to overpressure fluid advections along zones of active surface deformation.
Kaiko surveys over the Nankai Trough made available new magnetic and structural data for the nort... more Kaiko surveys over the Nankai Trough made available new magnetic and structural data for the northern Shikoku Basin. A survey of the oceanic lithosphere subducting below Southwest Japan along the central Nankai Trough revealed the existence of several north-south basement troughs. They are probably transform faults related to a north-south spreading system. We exanune the possibility of a late phase of north-south spreading limited to the axial northernmost Shikoku Basin, active between 14 and 12 Ma. If this system was already active before that time, i.e. during the N55 ° opening of the southeastern basin, then a triple junction should be found between both areas.
Abstract Recently, a new type of magnetoresistance oscillations beyond Shubinikov-de Hass (SdH) e... more Abstract Recently, a new type of magnetoresistance oscillations beyond Shubinikov-de Hass (SdH) effect have been observed in a plain high-mobility two-dimensional electron gas (2DEG) in GaAs-AlGaAs heterostructures [Zudov et al., APS Bulletin 44, 1572 (1999)]. Being periodic in 1/B these new oscillations appear at weak magnetic field (B< 0.3 T) and only in a narrow temperature range (3< T< 7 K), where SdH oscilations are already suppressed. Remarkably, these oscillations can be understood in terms of interaction of 2DEG and ...
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