Abstract:

The Tibetan Plateau is a major region of earthquake activity in China.  Five major earthquakes occurred in the Tibetan Plateau during the last decade.  They are the 1997 Mani earthquake of magnitude Ms 75 in Xizang, the 2001 Kunlun Mountains earthquake of magnitude Ms 81 in Qinghai, the 2008 Yutian earthquake of magnitude Ms 73 in Xingjiang, the 2008 Wenchuan earthquake of magnitude Ms 80 in Sichuan, and the 2010 Yushu earthquake of magnitude Ms 71 in Qinghai.  All of them occurred around the boundaries of the Bayankala faultblock of the Tibetan faultblock region and represented most recent activity of the block.  Earthquakes occurred on the northern and southern boundaries of the block are strikeslip faulting events.  The Wenchuan earthquake on its eastern boundary is a reverse faulting event.  The Yutian earthquake on the western boundary is a normal faulting event.  The kinematics of these events suggest the southeastward movement of the Bayankala faultblock.  Major regional seismicity in the Tibetan faultblock region and the Bayankala faultblock has shown the multiperiod activities and migration from one region to another since 1900.  Most of strong earthquakes occurred along the northern boundary of the Tibetan faultblock region in the early period of the last century, took place mostly along the southern boundary of the region in the middle period of the last century, and were located around the Bayankala faultblock during the last decade.  This pattern of seismic activity and faultblock motions in the Tibetan faultblock region and the Bayankala faultblock may relate to the compression and penetration of the AustraliaIndian plate into the Eurasian plate. Thus, the earthquake activity in the Tibetan Plateau and in the Bayankala faultblock may also relate to strong earthquake activity in Sumatra along the boundary of the AustraliaIndian plate.  Because great earthquakes are still occurring in the Sumatra region, great attention should be paid to the great earthquake risks in the Bayankala faultblock and the southern part of the Tibetan Plateau.

Key words: Tibetan faultblock region, Bayankala faultblock, the KunlunWenchuan earthquake series