Abstract: The M_S 8.0 Wenchuan earthquake caused tremendous disaster to the country and people,and meanwhile it also gives us many lessons worth thinking about.The severe earthquake disaster tells us the necessity of evaluating and surveying the seismic and geological environment in urban and township construction so as to avoid the unfavorable terrain conditions and keep away from the instable sites prone to landslide,soil liquefaction and mud-rock flow and etc,complying stringently the standards for disaster fortification regulated by the state and the relevant technical code for seismic design of buildings,including the houses in rural area,and intensifying the study on active tectonics to avoid the active faults and possible seismogenic tectonics.Since the historical earthquake record is too short and the recurrence interval of earthquakes is long within the continent,we should be cautious when using the principle of recurrence of historical earthquake in seismic hazard assessment,but promote the study on paleoearthquakes on active tectonics,so as to fully understand the history of earthquake recurrence.Big earthquake may also occur on low-slip-rate active fault,but with longer recurrence interval.So special attention be paid to the elapsed time of the latest event on it.The source rupture of the M_S 8.0 Wenchuan earthquake is characterized by a multi-point rupturing process,resulting from the expansion of deep fault from the detachment zone to the front-end ramp,and shown as double-ramp faulting on the surface.In the source rupture propagating process,the nature of the rupture changed.The southwest section is characterized with thrust faulting,and the northeast section turns to be dominated by strike-slipping.The initial thrust-type rupture occurring in the middle of the Longmenshan tectonic belt ran through its northeast section and became a new fault.The 1997 Mani,the 2001 west pass of Kunlun Mountains and the 2008 Wenchuan earthquakes with MS 7～8 are all the products of the movement of the Bayahar block.After the Wenchuan earthquake,a series of earthquakes with magnitude around 6 occurred in the Qinghai-Tibetan Fault block region,which characterizes the new episode of seismic activity of the Qinghai-Tibet Plateau block region.

Key words: M_S 8.0 Wenchuan earthquake, seismotectonics, Longmenshan tectonic belt, earthquake disaster reduction

摘要： 汶川8.0级地震给我们国家和人民带来巨大的灾难,也向我们提出许多值得进一步思考与吸取的教训。严重的震灾告诉我们:城镇建设必须进行地震地质环境评价和检查,避免不利地形地貌条件,避开容易产生滑坡、砂土液化和泥石流等非稳定地区;应严格按国家规定的抗震设防标准进行设防,房屋建筑,包括农村民房建筑都应严格执行有关抗震技术规程;应加强活动构造研究,查明活动断裂分布和可能的发震构造;由于历史地震记载时间太短,大陆内部地震复发周期又长,在进行地震危险性评价时,一定要慎用历史地震重复原则,而要加强活动构造与古地震研究,以尽可能全面掌握大地震复发的历史;低滑动速率的活动构造也可能发生大地震,但其重复间隔更长,要特别注意其最后一次事件至今的离逝时间;汶川8.0级地震震源破裂是一个多点破裂过程,是深部断裂由滑脱带向前端断坡扩展的结果,地表表现为双断坡活动,在震源破裂扩展的过程中,破裂性质发生转换,西南段以逆断层为主,东北段转变为以走滑作用为主,逆断层型初始破裂发生于龙门山构造带中段,随后的走滑破裂已突破中段,并穿过龙门山构造带的东北段,成为一条新生破裂带。1997年玛尼、2001年昆仑山口西和2008年汶川7～8级地震系列是巴颜喀喇断块整体活动的产物,汶川8.0级地震后,多次6级地震所形成的6级地震系列在青藏高原断块区活动,它们表征青藏高原断块区处于一个新的地震活动时期。

关键词: 汶川8.0级地震, 地震构造, 龙门山构造带, 减轻地震灾害