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Zhang Peizhen(Institute of Geology, China Seismological Bureau, Beijing 100029)  
hina is a country with high level of earthquake hazard. Statistics of globalearthquakes indicates that there have been more than 100 events with magnitude over7 occurred in China in this century , which takes up 10% of the total events (M7)in the world. Especially, about 38 Percent of global continental earthquakes occurredin continental China, which account for 52% of total global casualties caused byearthquake disasters. In China, more than 1 / 3 land surface, 1 / 2 cities, and 2 / 3megacities (population one million) are located in the areas that prone to earthquakeswith high intensity (above). As a tragic example, only from 1966 to 1978, therewere nine earthquakes() that successively struck China. These nine earthquakesoccurred in densely populated areas and caused approximately 300 000 casualties andmore than 2 billion US dollars in economic losses. Thus, seismic hazards pose amajor threat to the social and economic development of China.China is located in the southeastern part of the Eurasian plate bounded by theIndian, the Philippine Sea and the Pacific plates. The most remarkable feature is thatthe crust has been cut by huge Quaternary active faults forming active crustal blocksof different orders. These crustal blocks continue to be active from late Quaternary topresent. 104 historical earthquakes with magnitude over 7 occurred near boundaries ofdifferent crustal blocks. Thus, movements of the blocks and their interactions markthe characteristic of late Quaternary tectonic deformation.The active crust blocks are geological elements with late Quaternary tectonicactivities. Each crustal block has its own style, rate, and history of deformation.There is very little deformation in the interior of an active crustal block. Deformationcommonly takes places along their boundaries. Devastating earthquake (m7) mostlyoccurs along the major boundaries of active crustal blocks. On the basis of activetectonics and earthquake activity, continental China can be divided into blocks ofdifferent orders. different active crustal block subjects to different forces that result indifferent style of deformation and different behavior of earthquake activities.Tibetan Plateau is the most obvious active crustal block. Its southern boundaryconsists of several arc-shaped thrust faults along the Himalaya Mountains that controlgenerations of historical earthquakes of magnitude over 8. Nearly north-trend normalfaults and northwestern-trend strike-slip faults characterize southern part of the TibetanPlateau. Earthquakes often occur near the intersections of these two systems. Obliquethrusts of the Qilian Mountains onto the Alashan block is partitioned into thrustfaulting Perpendicular to and left lateral strike-slip along the Qilian Mountains thatcontrol occurrences of earthquakes along the northern boundary of the Tibetan Plateau.The Sichuan and Yunnan crustal block is another seismically active region. Therehave been 23 historical earthquakes with magnitude over 7 occurred along boundariesof the block. The Tianshan Mountains crustal block is characterized by north-southcompression and crustal shortening. The Tianshan Mountains thrusts toward bothdirections onto the Talimu block in the south and the Zhungarer block in the north.Most of earthquakes distributed along the southern and northern piedmonts of theTianshan Mountains. The tectonic activity within the Eerduosi active crustal block isvery low and there has been no earthquake with magnitude over 6 occurred in theinterior of the block. 19 historical earthquakes with magnitude over 7 take placearound the boundaries of the block. Crustal extension and right lateral shearingcharacterize the North China active crustal block. The northern and southernboundaries are marked by a series of discontinuous late Quaternary active faults.Devastating earthquakes, such as the 1976 Tangshan earthquake, often occur near thejunctions between the northern boundary of the block and the major faults in theinterior of foe block. Other crustal blocks can also be delineated in continental China,for example,
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