The Wenchuan earthquake and thoughts on relavant issues

A devastating earthquake of magnitude 8.0 called Wenchuan earthquake struck Sichuan on May 12,2008.It resulted in huge casualties and property losses in the Longmen region of Sichuan and the southern Shaanxi and southern Gansu.The paper introduces the tectonic settings and the general situation of the Wenchuan earthquake.It presents the authors' thought on the issues of the causative structure of the earthquake,the Longmen earthquake safety period after the earthquake,the earthquake safety of the Chengdu-Deyang-Mianyang economic zone,and the impaction of the earthquakes on the hydrocarbon accumulation and dissipation in West Sichuan.The authors put forward the following new opinions:(1) the causative structure of this earthquake may be the Peng-Guan fault,not the Beichuan-Yingxiu fault(central fault);(2) it is almost impossible for a devastating earthquake to occur in the urban areas of the Chengdu-Deyang-Mianyang economic zone;the main earthquake threat to these cities still comes from Longmen Mountains,and the menace from Longquan Mountains should also be taken into account;(3) the earthquake may lead to hydrocarbon dissipation in Longmen Mountains,but it may be favorable to the forming of the fractured reservoir and hydrocarbon accumulation in the West Sichuan depression;(4) The uplift of Longmen Mountains and the earthquakes in Longmen mountains may be controlled by the bilateral compressive forces from the Songpan-Ganzi block on the west side and Sichuan Basin on the east side.The authors put forward two tentative ideas: one is to estimate the rhythm of a strong earthquake in Longmen Mountains by calculating the balance between the accumulation and dissipation of the compressed strain energy,and another is to monitor the changes of the Earth stress in deep by using the pressure data measured from oil or gas producing wells.