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IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy
(S) - IASPEI - International Association of Seismology and Physics of the Earth's
Interior
JSS014 Oral Presentation 2259
GPS Constrain on Active Faulting and Block Rotation in deforming Asia
Dr. Wang Qi
Institute of Seismology China Earthquake Administration IASPEI
We explore a synthesized geodetic velocity field consisting ~2000 GPS velocities from the Crustal
Movement Observation Network of China (CMONOC ) and various campaigns throughout a period of
1991-2006. Our analysis of densified velocity data reveals a lot of unspecified features of active
deformation. A velocity profile along the direction of N15E across Tibet shows a pattern of localized
deformation on narrow zones of 50-100 km-wide associated with major Quaternary faults and sutures.
The maximum velocity gradient is located on the E-W trending Gangdes, Gaize-Amdo and Fenghuoshan
Thrusts. The thrusting slip rates are in range of 6-8 mm/yr comparable with striking-slip rates on the
sub-parallel Karakorum-Jiali, Manyi-Ganzi and Kunlun faults. The geodetic slip rates of major faults in
Tibet are 4-9 mm/yr. The fast rate of 14-18 mm/yr occurs on frontal thrusts at Himalaya, Pamir and
southwest Tienshan , and less than 4 mm/yr elsewhere outside Tibet. The overall geodetic velocity field
is predicted well within the uncertainty of 1-2 mm/yr in terms of rigid rotation model of 30 crustal blocks
intersected by the Quaternary faults. The GPS inferred rates are in general agreement with that of long
term faulting or its lower bound on the most faults. For example , the current geodetic rates are l one
factor of 2-3 smaller than the long tern rates of 20-30 mm/yr inferred from fault offset feature since
Holocene on the Altyn Tagh fault and Karakorum fault. Internal deformation within ~30 intervening
blocks hundreds of kilometers in dimension is relatively minor at level of several nano-strain /yr. The
GPS-inferred slip rates on the major faults in Tibet indicate that the fault slip associated with a
combination of crustal-scale block subducting, rifting and lateral extruding, has played a dominating role
in accommodating continental convergence on India-Eurasia plate boundary. Our block model suggests
that the tenet of plate tectonics may be applicable to characterize crustal deformation in Asia, though
the large-scale extrusion out of Tibet through rapid slip-rate faulting is not necessarily invoked.
Keywords: gps, active deformation, china