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Understanding micro-seismicity is a critical question for earthquake hazard assessment. Since the devastating earthquakes of Izmit and Duzce in 1999, the seismicity along the submerged section of North Anatolian Fault within the Sea of Marmara (comprising the “Istanbul seismic gap”) has been extensively studied in order to infer its mechanical behaviour (creeping vs locked). So far, the seismicity has been interpreted only in terms of being tectonic-driven, although the Main Marmara Fault (MMF) is known to strike across multiple hydrocarbon gas sources. Here, we show that a large number of the aftershocks that followed the M 5.1 earthquake of July, 25th 2011 in the western Sea of Marmara, occurred within a zone of gas overpressuring in the 1.5–5 km depth range, from where pressurized gas is expected to migrate along the MMF, up to the surface sediment layers. Hence, gas-related processes should also be considered for a complete interpretation of the micro-seismicity (~M < 3) within the Istanbul offshore domain.

Understanding micro-seismicity is a critical question for earthquake hazard assessment. Since the devastating earthquakes of Izmit and Duzce in 1999, the seismicity along the submerged section of North Anatolian Fault within the Sea of Marmara (comprising the “Istanbul seismic gap”) has been extensively studied in order to infer its mechanical behaviour (creeping vs locked). So far, the seismicity has been interpreted only in terms of being tectonic-driven, although the Main Marmara Fault (MMF) is known to strike across multiple hydrocarbon gas sources. Here, we show that a large number of the aftershocks that followed the M 5.1 earthquake of July, 25th 2011 in the western Sea of Marmara, occurred within a zone of gas overpressuring in the 1.5–5 km depth range, from where pressurized gas is expected to migrate along the MMF, up to the surface sediment layers. Hence, gas-related processes should also be considered for a complete interpretation of the micro-seismicity (~M < 3) within the Istanbul offshore domain.

Understanding micro-seismicity is a critical question for earthquake hazard assessment. Since the devastating earthquakes of Izmit and Duzce in 1999, the seismicity along the submerged section of North Anatolian Fault within the Sea of Marmara (comprising the “Istanbul seismic gap”) has been extensively studied in order to infer its mechanical behaviour (creeping vs locked). So far, the seismicity has been interpreted only in terms of being tectonic-driven, although the Main Marmara Fault (MMF) is known to strike across multiple hydrocarbon gas sources. Here, we show that a large number of the aftershocks that followed the M 5.1 earthquake of July, 25th 2011 in the western Sea of Marmara, occurred within a zone of gas overpressuring in the 1.5–5 km depth range, from where pressurized gas is expected to migrate along the MMF, up to the surface sediment layers. Hence, gas-related processes should also be considered for a complete interpretation of the micro-seismicity (~M < 3) within the Istanbul offshore domain.

Understanding micro-seismicity is a critical question for earthquake hazard assessment. Since the devastating earthquakes of Izmit and Duzce in 1999, the seismicity along the submerged section of North Anatolian Fault within the Sea of Marmara (comprising the “Istanbul seismic gap”) has been extensively studied in order to infer its mechanical behaviour (creeping vs locked). So far, the seismicity has been interpreted only in terms of being tectonic-driven, although the Main Marmara Fault (MMF) is known to strike across multiple hydrocarbon gas sources. Here, we show that a large number of the aftershocks that followed the M 5.1 earthquake of July, 25th 2011 in the western Sea of Marmara, occurred within a zone of gas overpressuring in the 1.5–5 km depth range, from where pressurized gas is expected to migrate along the MMF, up to the surface sediment layers. Hence, gas-related processes should also be considered for a complete interpretation of the micro-seismicity (~M < 3) within the Istanbul offshore domain.

Understanding micro-seismicity is a critical question for earthquake hazard assessment. Since the devastating earthquakes of Izmit and Duzce in 1999, the seismicity along the submerged section of North Anatolian Fault within the Sea of Marmara (comprising the “Istanbul seismic gap”) has been extensively studied in order to infer its mechanical behaviour (creeping vs locked). So far, the seismicity has been interpreted only in terms of being tectonic-driven, although the Main Marmara Fault (MMF) is known to strike across multiple hydrocarbon gas sources. Here, we show that a large number of the aftershocks that followed the M 5.1 earthquake of July, 25th 2011 in the western Sea of Marmara, occurred within a zone of gas overpressuring in the 1.5–5 km depth range, from where pressurized gas is expected to migrate along the MMF, up to the surface sediment layers. Hence, gas-related processes should also be considered for a complete interpretation of the micro-seismicity (~M < 3) within the Istanbul offshore domain.

Understanding micro-seismicity is a critical question for earthquake hazard assessment. Since the devastating earthquakes of Izmit and Duzce in 1999, the seismicity along the submerged section of North Anatolian Fault within the Sea of Marmara (comprising the “Istanbul seismic gap”) has been extensively studied in order to infer its mechanical behaviour (creeping vs locked). So far, the seismicity has been interpreted only in terms of being tectonic-driven, although the Main Marmara Fault (MMF) is known to strike across multiple hydrocarbon gas sources. Here, we show that a large number of the aftershocks that followed the M 5.1 earthquake of July, 25th 2011 in the western Sea of Marmara, occurred within a zone of gas overpressuring in the 1.5–5 km depth range, from where pressurized gas is expected to migrate along the MMF, up to the surface sediment layers. Hence, gas-related processes should also be considered for a complete interpretation of the micro-seismicity (~M < 3) within the Istanbul offshore domain.

Understanding micro-seismicity is a critical question for earthquake hazard assessment. Since the devastating earthquakes of Izmit and Duzce in 1999, the seismicity along the submerged section of North Anatolian Fault within the Sea of Marmara (comprising the “Istanbul seismic gap”) has been extensively studied in order to infer its mechanical behaviour (creeping vs locked). So far, the seismicity has been interpreted only in terms of being tectonic-driven, although the Main Marmara Fault (MMF) is known to strike across multiple hydrocarbon gas sources. Here, we show that a large number of the aftershocks that followed the M 5.1 earthquake of July, 25th 2011 in the western Sea of Marmara, occurred within a zone of gas overpressuring in the 1.5–5 km depth range, from where pressurized gas is expected to migrate along the MMF, up to the surface sediment layers. Hence, gas-related processes should also be considered for a complete interpretation of the micro-seismicity (~M < 3) within the Istanbul offshore domain.

Understanding micro-seismicity is a critical question for earthquake hazard assessment. Since the devastating earthquakes of Izmit and Duzce in 1999, the seismicity along the submerged section of North Anatolian Fault within the Sea of Marmara (comprising the “Istanbul seismic gap”) has been extensively studied in order to infer its mechanical behaviour (creeping vs locked). So far, the seismicity has been interpreted only in terms of being tectonic-driven, although the Main Marmara Fault (MMF) is known to strike across multiple hydrocarbon gas sources. Here, we show that a large number of the aftershocks that followed the M 5.1 earthquake of July, 25th 2011 in the western Sea of Marmara, occurred within a zone of gas overpressuring in the 1.5–5 km depth range, from where pressurized gas is expected to migrate along the MMF, up to the surface sediment layers. Hence, gas-related processes should also be considered for a complete interpretation of the micro-seismicity (~M < 3) within the Istanbul offshore domain.

Understanding micro-seismicity is a critical question for earthquake hazard assessment. Since the devastating earthquakes of Izmit and Duzce in 1999, the seismicity along the submerged section of North Anatolian Fault within the Sea of Marmara (comprising the “Istanbul seismic gap”) has been extensively studied in order to infer its mechanical behaviour (creeping vs locked). So far, the seismicity has been interpreted only in terms of being tectonic-driven, although the Main Marmara Fault (MMF) is known to strike across multiple hydrocarbon gas sources. Here, we show that a large number of the aftershocks that followed the M 5.1 earthquake of July, 25th 2011 in the western Sea of Marmara, occurred within a zone of gas overpressuring in the 1.5–5 km depth range, from where pressurized gas is expected to migrate along the MMF, up to the surface sediment layers. Hence, gas-related processes should also be considered for a complete interpretation of the micro-seismicity (~M < 3) within the Istanbul offshore domain.

We reply to the comments of J. Philip regarding the structure of La Nerthe range (southern Provence, France) and the timing of the deformation. We first agree with J. Philip on the structural independence of La Nerthe and L’Etoile ranges. We then discuss the allochthonous and autochthonous models. The allochthonous model mainly relies on a reactivation of a N-verging thrust during the Oligocene. There are no evidences for a Middle Rupelian thrusting event and the interpretation of the Oligocene series in southern Provence area was entirely revised. J. Philip’s Argumentation is solely based on the existence of steep dipping Rupelian limestones. However we demonstrate that they could be tilted along normal faults as it is the case in the Marseille basin. Recent works clearly show that the Oligocene Marseille and Saint-Pierre basins have a similar tectonic history resulting from two main extensional events. The last point debated by J. Philip is the age of the strike-slip faults. As it is pointed in our contribution the strike-slip fault planes cut folded strata and were reactivated during an extensional event. This strike-slip faulting event occurred between the latest stages of the main Bartonian compressional event and the beginning of the Early Rupelian extensional tectonics. As pointed by J. Philip the E-trending faults of Saint-Pierre basin acted as normal faults during the Oligocene. We however suggest that these faults were inherited from the Late Eocene strike-slip tectonics and reactivated during the Oligocene.

The submerged section of the North Anatolian fault within the Marmara Sea was investigated using acoustic techniques and submersible dives. Most gas emissions in the water column were found near the surface expression of known active faults. Gas emissions are unevenly distributed. The linear fault segment crossing the Central High and forming a seismic gap - as it has not ruptured since 1766, based on historical seismicity [Ambraseys, N.N., and Jackson, J.A., (2000), Seismicity of the Sea of Marmara (Turkey) since 1500, Geophys. J. Int., 141, (3), F1-F6. (doi:10.1046/j.1365-246x.2000.00137.x: Ambraseys, N., (2002), The seismic activity of the Marmara Region over the last 2000 years, Bull. Seism. Soc. Am., 92, 1-18; Parson, T., (2004), Recalculated probability of M >= 7 earthquakes beneath the Sea of Marmara, Turkey,J. Geophys. Res., 109, B05304, doi: 10.1029/2003JB002667: Pondard, N., Armijo, R., King, G.C.P., Meyer, B., Flerit, F, (2007), Fault interactions in the Sea of Marmara pull-apart (North Anatolian Fault): earthquake clustering and propagating earthquake sequences, Geophys. J. hit., 171, 1185-1197, doi: 10;1111/j.1365-246X.2007.03580.x] -, exhibits relatively less gas emissions than the adjacent segments. In the eastern Sea of Marmara, active gas emissions are also found above a buried transtensional fault zone [Carton, H., Singh, S.C., Hirn, A., Bazin, S., de Voogd, B., Vigner, A., Ricolleau, A., Cetin, S., Ocakoglu, N., Karakoc, F. and Sevilgen, V., (2007), Seismic imaging of the three-dimensional architecture of the Cmarcik Basin along the North Anatolian Fault,J. Geophys. Res., 180, B06101, doi:10.1029/2006JB004548; Okay, A.I., Kashlar-Ozcan, A., Imren, C., Boztepe-Guney, A., Demirbag, E., and Kuscu, I., (2000). Active faults and evolving strike-slip basins in the Sea of Marmara, northwest Turkey: a multichannel seismic reflection study, Tectonophysics, 321,189-218], which displayed micro-seismic activity after the 1999 events [Ozalabey, S., Ergin, M.

The submerged section of the North Anatolian fault within the Marmara Sea was investigated using acoustic techniques and submersible dives. Most gas emissions in the water column were found near the surface expression of known active faults. Gas emissions are unevenly distributed. The linear fault segment crossing the Central High and forming a seismic gap - as it has not ruptured since 1766, based on historical seismicity [Ambraseys, N.N., and Jackson, J.A., (2000), Seismicity of the Sea of Marmara (Turkey) since 1500, Geophys. J. Int., 141, (3), F1-F6. (doi:10.1046/j.1365-246x.2000.00137.x: Ambraseys, N., (2002), The seismic activity of the Marmara Region over the last 2000 years, Bull. Seism. Soc. Am., 92, 1-18; Parson, T., (2004), Recalculated probability of M >= 7 earthquakes beneath the Sea of Marmara, Turkey,J. Geophys. Res., 109, B05304, doi: 10.1029/2003JB002667: Pondard, N., Armijo, R., King, G.C.P., Meyer, B., Flerit, F, (2007), Fault interactions in the Sea of Marmara pull-apart (North Anatolian Fault): earthquake clustering and propagating earthquake sequences, Geophys. J. hit., 171, 1185-1197, doi: 10;1111/j.1365-246X.2007.03580.x] -, exhibits relatively less gas emissions than the adjacent segments. In the eastern Sea of Marmara, active gas emissions are also found above a buried transtensional fault zone [Carton, H., Singh, S.C., Hirn, A., Bazin, S., de Voogd, B., Vigner, A., Ricolleau, A., Cetin, S., Ocakoglu, N., Karakoc, F. and Sevilgen, V., (2007), Seismic imaging of the three-dimensional architecture of the Cmarcik Basin along the North Anatolian Fault,J. Geophys. Res., 180, B06101, doi:10.1029/2006JB004548; Okay, A.I., Kashlar-Ozcan, A., Imren, C., Boztepe-Guney, A., Demirbag, E., and Kuscu, I., (2000). Active faults and evolving strike-slip basins in the Sea of Marmara, northwest Turkey: a multichannel seismic reflection study, Tectonophysics, 321,189-218], which displayed micro-seismic activity after the 1999 events [Ozalabey, S., Ergin, M.

The submerged section of the North Anatolian fault within the Marmara Sea was investigated using acoustic techniques and submersible dives. Most gas emissions in the water column were found near the surface expression of known active faults. Gas emissions are unevenly distributed. The linear fault segment crossing the Central High and forming a seismic gap - as it has not ruptured since 1766, based on historical seismicity [Ambraseys, N.N., and Jackson, J.A., (2000), Seismicity of the Sea of Marmara (Turkey) since 1500, Geophys. J. Int., 141, (3), F1-F6. (doi:10.1046/j.1365-246x.2000.00137.x: Ambraseys, N., (2002), The seismic activity of the Marmara Region over the last 2000 years, Bull. Seism. Soc. Am., 92, 1-18; Parson, T., (2004), Recalculated probability of M >= 7 earthquakes beneath the Sea of Marmara, Turkey,J. Geophys. Res., 109, B05304, doi: 10.1029/2003JB002667: Pondard, N., Armijo, R., King, G.C.P., Meyer, B., Flerit, F, (2007), Fault interactions in the Sea of Marmara pull-apart (North Anatolian Fault): earthquake clustering and propagating earthquake sequences, Geophys. J. hit., 171, 1185-1197, doi: 10;1111/j.1365-246X.2007.03580.x] -, exhibits relatively less gas emissions than the adjacent segments. In the eastern Sea of Marmara, active gas emissions are also found above a buried transtensional fault zone [Carton, H., Singh, S.C., Hirn, A., Bazin, S., de Voogd, B., Vigner, A., Ricolleau, A., Cetin, S., Ocakoglu, N., Karakoc, F. and Sevilgen, V., (2007), Seismic imaging of the three-dimensional architecture of the Cmarcik Basin along the North Anatolian Fault,J. Geophys. Res., 180, B06101, doi:10.1029/2006JB004548; Okay, A.I., Kashlar-Ozcan, A., Imren, C., Boztepe-Guney, A., Demirbag, E., and Kuscu, I., (2000). Active faults and evolving strike-slip basins in the Sea of Marmara, northwest Turkey: a multichannel seismic reflection study, Tectonophysics, 321,189-218], which displayed micro-seismic activity after the 1999 events [Ozalabey, S., Ergin, M.

The submerged section of the North Anatolian fault within the Marmara Sea was investigated using acoustic techniques and submersible dives. Most gas emissions in the water column were found near the surface expression of known active faults. Gas emissions are unevenly distributed. The linear fault segment crossing the Central High and forming a seismic gap – as it has not ruptured since 1766, based on historical seismicity, exhibits relatively less gas emissions than the adjacent segments. In the eastern Sea of Marmara, active gas emissions are also found above a buried transtensional fault zone, which displayed micro-seismic activity after the 1999 events. Remarkably, this zone of gas emission extends westward all along the southern edge of Cinarcik basin, well beyond the zone where 1999 aftershocks were observed. The long term monitoring of gas seeps could hence be highly valuable for the understanding of the evolution of the fluid-fault coupling processes during the earthquake cycle within the Marmara Sea.

The submerged section of the North Anatolian fault within the Marmara Sea was investigated using acoustic techniques and submersible dives. Most gas emissions in the water column were found near the surface expression of known active faults. Gas emissions are unevenly distributed. The linear fault segment crossing the Central High and forming a seismic gap – as it has not ruptured since 1766, based on historical seismicity, exhibits relatively less gas emissions than the adjacent segments. In the eastern Sea of Marmara, active gas emissions are also found above a buried transtensional fault zone, which displayed micro-seismic activity after the 1999 events. Remarkably, this zone of gas emission extends westward all along the southern edge of Cinarcik basin, well beyond the zone where 1999 aftershocks were observed. The long term monitoring of gas seeps could hence be highly valuable for the understanding of the evolution of the fluid-fault coupling processes during the earthquake cycle within the Marmara Sea.

Trench-parallel thrust faults verging both landward and seaward were mapped in the portion of wedge located between northern Sumatra and the Indian-Indonesian boundary. The spatial aftershocks distribution of the 26th December 2004 earthquake shows that the post-seismic motion is partitioned along two thrust faults, the Lower and Median Thrust Faults, the latter being right-laterally offset by a N-S lower plate fracture zone located along the 93.6 degrees N meridian. Between February 2005 and August 2005, the upper plate aftershock activity shifted from southeast of this fracture zone to northwest of it, suggesting that the lower plate left-lateral motion along the fracture zone may have induced a shift of the upper plate post-seismic activity along the Median Thrust Fault. Based on swath bathymetric and 3.5 kHz data, co-seismic deformations were weak close to the trench. Joint seismic-geodetic determination of slip distribution and time arrivals and heights of tsunami waves suggest that the co-seismic slip was maximum along a portion of the Upper Thrust Fault located north of the Tuba Ridge, suggesting that the Upper Thrust Fault might be a splay fault originated at the interplate fault plane. As the Upper Thrust Fault is steeper than the slab, the vertical motion of the adjacent Outer Arc and overlying water is much larger compared to the one resulting from slip on the megathrust alone, increasing tsunamogenic effects.

Trench-parallel thrust faults verging both landward and seaward were mapped in the portion of wedge located between northern Sumatra and the Indian-Indonesian boundary. The spatial aftershocks distribution of the 26th December 2004 earthquake shows that the post-seismic motion is partitioned along two thrust faults, the Lower and Median Thrust Faults, the latter being right-laterally offset by a N-S lower plate fracture zone located along the 93.6 degrees N meridian. Between February 2005 and August 2005, the upper plate aftershock activity shifted from southeast of this fracture zone to northwest of it, suggesting that the lower plate left-lateral motion along the fracture zone may have induced a shift of the upper plate post-seismic activity along the Median Thrust Fault. Based on swath bathymetric and 3.5 kHz data, co-seismic deformations were weak close to the trench. Joint seismic-geodetic determination of slip distribution and time arrivals and heights of tsunami waves suggest that the co-seismic slip was maximum along a portion of the Upper Thrust Fault located north of the Tuba Ridge, suggesting that the Upper Thrust Fault might be a splay fault originated at the interplate fault plane. As the Upper Thrust Fault is steeper than the slab, the vertical motion of the adjacent Outer Arc and overlying water is much larger compared to the one resulting from slip on the megathrust alone, increasing tsunamogenic effects.

Trench-parallel thrust faults verging both landward and seaward were mapped in the portion of wedge located between northern Sumatra and the Indian-Indonesian boundary. The spatial aftershocks distribution of the 26th December 2004 earthquake shows that the post-seismic motion is partitioned along two thrust faults, the Lower and Median Thrust Faults, the latter being right-laterally offset by a N-S lower plate fracture zone located along the 93.6 degrees N meridian. Between February 2005 and August 2005, the upper plate aftershock activity shifted from southeast of this fracture zone to northwest of it, suggesting that the lower plate left-lateral motion along the fracture zone may have induced a shift of the upper plate post-seismic activity along the Median Thrust Fault. Based on swath bathymetric and 3.5 kHz data, co-seismic deformations were weak close to the trench. Joint seismic-geodetic determination of slip distribution and time arrivals and heights of tsunami waves suggest that the co-seismic slip was maximum along a portion of the Upper Thrust Fault located north of the Tuba Ridge, suggesting that the Upper Thrust Fault might be a splay fault originated at the interplate fault plane. As the Upper Thrust Fault is steeper than the slab, the vertical motion of the adjacent Outer Arc and overlying water is much larger compared to the one resulting from slip on the megathrust alone, increasing tsunamogenic effects.

Active deformation of the sea-floor of the Hellenic trench has been observed using the Cyana SP-3000 submersible. The strain pattern observed on a scale of a few kilometers is similar to the one deduced from an analysis of Seabeam morphological maps on a scale of tens of kilometers. The overall strain pattern is compatible with subduction of the Mediterranean sea-floor toward the northeast. It is characterized by underthrusting in the Western Ionian branch and left-lateral strike-slip faulting in the Eastern Strabo branch.

Deep-sea hydrothermal deposits were observed, mapped and sampled in situ with the submersible "Cyana" in the Famous area of the Mid-Atlantic Ridge.Two neighbouring fields, each covering an area of about 600 m2, are associated with low, E-W trending sediment-covered ridges that lie at a depth of about 2 700 m close to the axis of Transform Fault "A".In each field the deposits are thicker (up to about 1 m) close to the small, fissure-like vents through which they were evidently delivered. Despite their heterogeneous composition, their mineralogical and chemical variations have an orderly pattern.The principal constituents are a green clay-rich material, and Fe-Mn oxides in the form of black concretions. The relative abundances of these products vary with distance from the source-vent.The green clay-rich material, abundant near the vent, consists of hydromica, smectite and an amorphous Fe-Si compound.Further away, the Fe-Mn concretions, made up of rancieite and todorokite, are the dominant components. [NOT CONTROLLED OCR], La soucoupe plongeante " Cyana » a permis d'observer, de cartographier et d'échantillonner in situ des dépôts hydrothermaux dans la zone Famous de la dorsale médio-atlantique.Deux sites voisins, chacun recouvrant une surface d'environ 600 m2 forment des monticules très peu sédimentés et allongés dans une direction E-W à une profondeur d'environ 2 700 m au voisinage de l'axe de la Faille Transformante "A".Dans chaque site les dépôts sont plus épais (ils atteignent 1 m) près des griffons en forme de fissures. Les dépôts sont formés soit d'argile, en général de couleur verte, soit de concrétions noires de fer et de manganèse.Malgré leurs caractères hétérogènes la minéralogie et la chimie des dépôts montrent une zonation.L'abondance relative des dépôts varie avec la distance aux griffons : les dépôts de couleur verte enrichis en argile (smectite, hydromica et matériel amorphe enrichi en Fe-Si), sont abondants près des sorties; les concrétions de Fe-Mn deviennent abondantes au fur et à mesure que l'on s'en éloigne. Parmi les principaux produits de Fe-Mn notons la todorokite et la rancieite. [OCR NON CONTRÔLE]

Active deformation of the sea-floor of the Hellenic trench has been observed using the Cyana SP-3000 submersible. The strain pattern observed on a scale of a few kilometers is similar to the one deduced from an analysis of Seabeam morphological maps on a scale of tens of kilometers. The overall strain pattern is compatible with subduction of the Mediterranean sea-floor toward the northeast. It is characterized by underthrusting in the Western Ionian branch and left-lateral strike-slip faulting in the Eastern Strabo branch.

Deep-sea hydrothermal deposits were observed, mapped and sampled in situ with the submersible "Cyana" in the Famous area of the Mid-Atlantic Ridge.Two neighbouring fields, each covering an area of about 600 m2, are associated with low, E-W trending sediment-covered ridges that lie at a depth of about 2 700 m close to the axis of Transform Fault "A".In each field the deposits are thicker (up to about 1 m) close to the small, fissure-like vents through which they were evidently delivered. Despite their heterogeneous composition, their mineralogical and chemical variations have an orderly pattern.The principal constituents are a green clay-rich material, and Fe-Mn oxides in the form of black concretions. The relative abundances of these products vary with distance from the source-vent.The green clay-rich material, abundant near the vent, consists of hydromica, smectite and an amorphous Fe-Si compound.Further away, the Fe-Mn concretions, made up of rancieite and todorokite, are the dominant components. [NOT CONTROLLED OCR], La soucoupe plongeante " Cyana » a permis d'observer, de cartographier et d'échantillonner in situ des dépôts hydrothermaux dans la zone Famous de la dorsale médio-atlantique.Deux sites voisins, chacun recouvrant une surface d'environ 600 m2 forment des monticules très peu sédimentés et allongés dans une direction E-W à une profondeur d'environ 2 700 m au voisinage de l'axe de la Faille Transformante "A".Dans chaque site les dépôts sont plus épais (ils atteignent 1 m) près des griffons en forme de fissures. Les dépôts sont formés soit d'argile, en général de couleur verte, soit de concrétions noires de fer et de manganèse.Malgré leurs caractères hétérogènes la minéralogie et la chimie des dépôts montrent une zonation.L'abondance relative des dépôts varie avec la distance aux griffons : les dépôts de couleur verte enrichis en argile (smectite, hydromica et matériel amorphe enrichi en Fe-Si), sont abondants près des sorties; les concrétions de Fe-Mn deviennent abondantes au fur et à mesure que l'on s'en éloigne. Parmi les principaux produits de Fe-Mn notons la todorokite et la rancieite. [OCR NON CONTRÔLE]

Active deformation of the sea-floor of the Hellenic trench has been observed using the Cyana SP-3000 submersible. The strain pattern observed on a scale of a few kilometers is similar to the one deduced from an analysis of Seabeam morphological maps on a scale of tens of kilometers. The overall strain pattern is compatible with subduction of the Mediterranean sea-floor toward the northeast. It is characterized by underthrusting in the Western Ionian branch and left-lateral strike-slip faulting in the Eastern Strabo branch.

Deep-sea hydrothermal deposits were observed, mapped and sampled in situ with the submersible "Cyana" in the Famous area of the Mid-Atlantic Ridge.Two neighbouring fields, each covering an area of about 600 m2, are associated with low, E-W trending sediment-covered ridges that lie at a depth of about 2 700 m close to the axis of Transform Fault "A".In each field the deposits are thicker (up to about 1 m) close to the small, fissure-like vents through which they were evidently delivered. Despite their heterogeneous composition, their mineralogical and chemical variations have an orderly pattern.The principal constituents are a green clay-rich material, and Fe-Mn oxides in the form of black concretions. The relative abundances of these products vary with distance from the source-vent.The green clay-rich material, abundant near the vent, consists of hydromica, smectite and an amorphous Fe-Si compound.Further away, the Fe-Mn concretions, made up of rancieite and todorokite, are the dominant components. [NOT CONTROLLED OCR], La soucoupe plongeante " Cyana » a permis d'observer, de cartographier et d'échantillonner in situ des dépôts hydrothermaux dans la zone Famous de la dorsale médio-atlantique.Deux sites voisins, chacun recouvrant une surface d'environ 600 m2 forment des monticules très peu sédimentés et allongés dans une direction E-W à une profondeur d'environ 2 700 m au voisinage de l'axe de la Faille Transformante "A".Dans chaque site les dépôts sont plus épais (ils atteignent 1 m) près des griffons en forme de fissures. Les dépôts sont formés soit d'argile, en général de couleur verte, soit de concrétions noires de fer et de manganèse.Malgré leurs caractères hétérogènes la minéralogie et la chimie des dépôts montrent une zonation.L'abondance relative des dépôts varie avec la distance aux griffons : les dépôts de couleur verte enrichis en argile (smectite, hydromica et matériel amorphe enrichi en Fe-Si), sont abondants près des sorties; les concrétions de Fe-Mn deviennent abondantes au fur et à mesure que l'on s'en éloigne. Parmi les principaux produits de Fe-Mn notons la todorokite et la rancieite. [OCR NON CONTRÔLE]

Active deformation of the sea-floor of the Hellenic trench has been observed using the Cyana SP-3000 submersible. The strain pattern observed on a scale of a few kilometers is similar to the one deduced from an analysis of Seabeam morphological maps on a scale of tens of kilometers. The overall strain pattern is compatible with subduction of the Mediterranean sea-floor toward the northeast. It is characterized by underthrusting in the Western Ionian branch and left-lateral strike-slip faulting in the Eastern Strabo branch.

Deep-sea hydrothermal deposits were observed, mapped and sampled in situ with the submersible "Cyana" in the Famous area of the Mid-Atlantic Ridge.Two neighbouring fields, each covering an area of about 600 m2, are associated with low, E-W trending sediment-covered ridges that lie at a depth of about 2 700 m close to the axis of Transform Fault "A".In each field the deposits are thicker (up to about 1 m) close to the small, fissure-like vents through which they were evidently delivered. Despite their heterogeneous composition, their mineralogical and chemical variations have an orderly pattern.The principal constituents are a green clay-rich material, and Fe-Mn oxides in the form of black concretions. The relative abundances of these products vary with distance from the source-vent.The green clay-rich material, abundant near the vent, consists of hydromica, smectite and an amorphous Fe-Si compound.Further away, the Fe-Mn concretions, made up of rancieite and todorokite, are the dominant components. [NOT CONTROLLED OCR], La soucoupe plongeante " Cyana » a permis d'observer, de cartographier et d'échantillonner in situ des dépôts hydrothermaux dans la zone Famous de la dorsale médio-atlantique.Deux sites voisins, chacun recouvrant une surface d'environ 600 m2 forment des monticules très peu sédimentés et allongés dans une direction E-W à une profondeur d'environ 2 700 m au voisinage de l'axe de la Faille Transformante "A".Dans chaque site les dépôts sont plus épais (ils atteignent 1 m) près des griffons en forme de fissures. Les dépôts sont formés soit d'argile, en général de couleur verte, soit de concrétions noires de fer et de manganèse.Malgré leurs caractères hétérogènes la minéralogie et la chimie des dépôts montrent une zonation.L'abondance relative des dépôts varie avec la distance aux griffons : les dépôts de couleur verte enrichis en argile (smectite, hydromica et matériel amorphe enrichi en Fe-Si), sont abondants près des sorties; les concrétions de Fe-Mn deviennent abondantes au fur et à mesure que l'on s'en éloigne. Parmi les principaux produits de Fe-Mn notons la todorokite et la rancieite. [OCR NON CONTRÔLE]

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