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RECORD OF block rotation AND MAGNETIC FIELD REVERSALS IN THE TETHYAN HIMALAYA(HIDDEN VALLEY,CENTRAL NEPAL)

地学前缘 2000年第S1期7卷 56-57页

作者： C.Crouzet H.Stang E.Schill E.Appel Institut für Geologie und Pal█ontologie Abteilung GeophysikUniversitat TübingenSigwartstrasse 1072076 TübingenGermany

Metasediments from the Tethyan Himalaya (TH) were sampled for paleomagnetic studies in several areas. In this paper, we will present the first results from Carboniferous and Early Triassic marly limestones from Hidden Valley (Central Nepal).. The paleomagnetic directions reflect a Tertiary overprint probably synchronous with the metamorphism. In this area, the metamorphic conditions reached during Tertiary are poorly constrained. Temperatures are probably in between 300 and 400℃. The age of the thermal event is still debated. No geochronological data is available in this area. Previously published geochronological data from the northern part of TH metasediments in India ranges from 47 to 42Ma (Ar/Ar Illite) after Weissman et al. (1999) and Bonhomme and Garzanti (1991). While in the southern part (close to HHC), biotite Ar/Ar data ranges from 30 to 26Ma in Marsyandi Valley (Coleman and Hodges, 1998) and muscovite Ar/Ar ranges from 18 to 12Ma in the upper Kali Gandaki Valley (Godin et al., 1998).. In this context, the age of the magnetization can′t be defined with precision.

关键词： paleomagnetism Central Nepal Tethyan Himalaya block rotation thermal evolution

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Crustal block rotations in Chinese mainland revealed by GPS measurements

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Earthquake Science 2009年第6期22卷 639-649页

作者： Wei Wang Shaomin Yang Qi Wang Institute of Seismology China Earthquake Administration Wuhan 430071 China Institute of Geophysics China Earthquake Administration Beijing 100081 China Research Center of Space Science and Technology China University of Geosciences Wuhan 430074 China

We simulate GPS horizontal velocity field in terms of rotations of crustal blocks to describe deformation behavior of the Chinese mainland and its neighboring areas. 31 crustal blocks are bounded primarily by -30 Quaternary faults with distinct geometries and variable long-term rates of 〈20 mm/a, and 1 683 GPS velocities were determined from decade-long observations mostly with an averaged uncertainty of 1-2 mm/a. We define GPS velocity at a site by the combination of motion of rigid block and elastic strain induced by the fault that is locking during a seismic cycle. Model velocities predicted from the preferable block model match well with the GPS velocities to an uncertainty of-l.7mm/a. The slip rates inferred from this model is in a range of 6-18 mm/a for the major faults in Tibet and its margins and 1-4 mm/a in eastern China, consistent with geological observations. Our numerical simulation suggests that the crustal blocks deform internally at a level of-10× 10^-9/a, quite small in comparison with significant deformation localized along fault zones of 50-100 km wide. We conclude that the pattern of continental deformation is not continuous-like but block-like, and the tenet of plate tectonics may be applicable to characterize the active deformation in Asia.

关键词： GPS Chinese mainland active block block rotation crustal deformation

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