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Seismic anisotropy beneath Tibet: evidence for eastward extrusion of the Tibetan lithosphere? 总被引：11，自引：0，他引：11
J. Lav J.P. Avouac R. Lacassin P. Tapponnier J.P. Montagner 《Earth and Planetary Science Letters》1996,140(1-4):83-96
Strong seismic anisotropy beneath Tibet has recently been reported from the study of SKS shear wave splitting. The fast split waves are generally polarized in an easterly direction, close to the present day direction of motion of the Tibetan crust relative to stable Eurasia, as deduced from Holocene slip rates on the major active faults in and around Tibet. This correlation may be taken to suggest that the whole Tibetan lithosphere is being extruded in front of indenting India and that the anisotropic layer is the deforming asthenosphere, that accommodates the motion of the Tibetan lithosphere relative to the fixed mantle at depth. Uncertainties about this motion are at present too large to bring unambiguous support to that view. Assuming that this view is correct however, a simple forward model is used to compute theoretical delay times as a function of the thickness of the anisotropic layer. The observed delay times would require a 50–100 km thick anisotropic layer beneath south-central Tibet and an over 200 km thick layer beneath north-central Tibet, where particularly hot asthenosphere has been inferred. This study suggests that the asthenospheric anisotropy due to present absolute block motion might be dominant under actively deforming continents. 相似文献
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The ML 5.3 Épagny (French Alps) earthquake of 1996 July 15: a long-awaited event on the Vuache Fault
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The 1356 Basel earthquake was the strongest event to have shaken NW Europe in the last thousand years. The peculiar location of this historical event makes it possible to relate it to normal faulting along the edges of the Rhine Graben, as well as to reverse faulting along the Jura frontal thrust or to fault reactivation within the Hercynian basement. Alternate hypotheses are discussed and their implications compared taking into account available structural data and results of the morphotectonic study performed in the epicentral area. This study combines field observations with the analysis of SPOT satellite imagery, aerial photographs, and detailed topography. It is concluded that the Basel earthquake most probably reactivated a basement fault (reverse or wrench fault) beneath the shallow-depth aseismic detachment that underlies the Jura Mountains. 相似文献
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李海兵 Franck Valli 许志琴杨经绥 Paul Tapponnier Robin Lacassin 陈松永戚学祥 Marie-Luce Chevalier 《中国地质》2006,33(2):239-255
喀喇昆仑断裂的变形特征、形成时代、构造演化以及它的构造意义一直存在着争议。在喀喇昆仑断裂东南段阿伊拉日居山地区,沿断裂出露具右旋剪切应变的糜棱岩和糜棱岩化片麻岩-花岗岩,显微构造研究表明其存在高温右旋剪切变形特征,并伴随淡色同构造花岗岩的产生,同构造结晶锆石所记录的U-Pb同位素年龄,暗示了喀喇昆仑断裂的形成时代在23-25Ma以前,其连续变形作用持续到-12Ma,之后伴随阿伊拉日居山的快速隆升以及噶尔盆地开始形成。综合分析表明喀喇昆仑断裂生长过程可能是由南东向北西扩展的过程,是印度板块与欧亚大陆持续碰撞的结果。断裂的累积位移量至少为280km,其长期平均滑移速率约为11mm／a。通过块体间运动学分析,表明在-23-25Ma以后青藏高原物质以约16．2mmn/a的速率向-N108°方向挤出。 相似文献
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P.H. Leloup N.O. ArnaudG. Mahéo J.L. PaquetteS. Guillot F. ValliH. Li Z. XuR. Lacassin P. Tapponnier 《Gondwana Research》2012,21(1):37-52
Field study, thermochronology and geochemistry of the east Lungmu Co (LMC) range highlight some of the geological events that shaped western Tibet. The LMC fault zone has long been interpreted as the boundary between the Tianshuihai terrane of Laurasian affinity and the Qiangtang block of Gondwanian affinity. In the LMC range, the Paleozoic series is intruded by the Mangtsa leucogranite whose zircon have a U/Pb age of 116.9 ± 1 Ma and by mafic rocks with U/Pb zircon ages ranging from 116.9 ± 1 to 95.1 ± 1.7 Ma. Geochemistry of the mafic rocks indicates that they have been emplaced in a supra-subduction zone setting, probably the north dipping Nujiang suture zone. 40Ar/39Ar micas ages of the granite indicate that cooling below ~ 350 °C occurred between 105 and 85 Ma. 40Ar/39Ar K-feldspar data suggest a fast cooling event at 60-55 Ma, which we relate to the reactivation of the LMC suture zone as a thrust at the onset of the India-Eurasia collision. The last, and still active, deformation event corresponds to left-lateral strike-slip faulting along the ENE-WSW LMC fault. 相似文献
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Unconformity of red sandstones in north Vietnam: field evidence for Indosinian orogeny in northern Indochina? 总被引：1，自引：0，他引：1
We re-examine several unconformity sites in northwestern Vietnam where the Indosinian orogenesis has been defined. Field observations in the Black-River (Song Da) region, near Son La, demonstrate that red sandtones and conglomerates, reportedly of Cretaceous age, occur unconformably above schistosed epimetamorphic middle-Triassic sediments. A mesozoic unconformity thus really exists in this region, though the age of deformation is poorly contrained (upper Triassic to upper Cretaceous). In most places, however, the unconformity is strongly deformed, folded Triassic limestones are often thrusted onto the Cretaceous rocks. This implies that Tertiary deformations probably due to the India–Asia collision have been strong in the northern part of the Indochina block. 相似文献
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