Showing papers by "Philippe Huchon published in 1992"

Two‐ship deep seismic soundings in the basins of the Eastern Mediterranean Sea (Pasiphae cruise)

Abstract: SUMMARY New results from a two-ship refraction and oblique reflection deep seismic cruise are presented to discuss the nature of the crust in the Ionian, Sirte and Herodotus abyssal plains These expanding spread profiles were processed and analysed in both the x–t and p domains Arrival times of reflected and refracted branches are matched by ray tracing in both domains In spite of a shallow evaporitic sequence (messinian evaporites) deposited on top of a thick sedimentary pile responsible for velocity inversions on many profiles, we obtain excellent velocity control down to Moho depth PmP and Pn (84–86 km s-1) arrivals are observed The three basins have a relatively thin crust (8 to 11 km) overlain by a thick sedimentary cover, up to 10km in the Herodotus abyssal plain The Moho boundary and main crustal units identified in the basins can be followed beneath the Calabrian prism to the west, and beneath the Mediterranean Ridge to the east The crustal structure is of oceanic type for both the Ionian and Sirte basins, where typical oceanic layer 2 and 3 are recognized The thin crust of the Herodotus basin may be interpreted either as oceanic or thinned continental crust (about 10 km thick) The top of the crust of the Herodotus basin is much deeper Therefore, the Herodotus basin is probably significantly older than the Ionian basin, Triassic versus Early Cretaceous in age

Cenozoic intracontinental dextral motion in the Okhotsk-Japan Sea Region

Abstract: A right-lateral shear zone trending northerly along more than 2000 km is recognized from central Japan to northern Sakhalin. It was active mainly during the Neogene and has accommodated several hundreds of kilometers of displacement. The whole structure of Sakhalin is built on this shear zone. En echelon sigmoidal folds and thrusts, en echelon narrow Miocene basins, and a major discontinuity which is observed along more than 600 km, the Tym-Poronaisk fault, characterize the deformation there. In Hokkaido, en echelon folds and thrusts and a ductile shear zone with high-temperature metamorphism constitute the southern extension of this transpressional shear zone. It continues to the south as a zone of transtensional deformation along the eastern margin of Japan Sea, as en echelon basins and dextral transfer faults observed as far south as Noto peninsula and Yatsuo basin. The style of the shear zone thus evolves from transpressional in the north far from the subduction zone, to transtensional in the south in the back-arc region. Strike-slip motion along this shear zone was primarily responsible for the dextral pull-apart opening of Japan Sea during the early and middle Miocene. Dextral motion is still active in the north along the Tym-Poronaisk fault in Sakhalin as well as on the continental margin of Japan Sea (Korea and Asia mainland). Active E-W compression replaced the dextral motion along the eastern margin of Japan Sea in late Miocene time, and incipient subduction began in the early Quaternary.