东亚地区现今构造应力图的编制

A PRESENT-DAY TECTONIC STRESS MAP FOR EASTERN ASIA REGION

利用 2 993个浅源地震的地震矩张量解、 40 4个 P波初动方向震源机制解和 47个深井孔的孔壁崩落资料 ,编制了东亚地区现今地壳构造应力场主应力方向和应力类型分布图 .按2 0 0 km的等距格点 ,算出有资料地区各格点半径为 2 0 0 km范围内的平均应力方向 ,绘制了平均主应力方向分布图 ,并绘制了东亚地区的震源机制解分布图 .主应力方向分布特征表明 ,东亚地区的现今构造应力场除受印度 -欧亚板块碰撞的强烈影响外 ,俯冲带的弧后扩张亦有重要影响 .喜马拉雅山弧处的大陆碰撞和缅甸山弧处的弧后扩张之联合作用可能形成了青藏高原东南部主应力方向的显著转动 .菲律宾海板块与欧亚板块在台湾的碰撞与琉球岛弧弧后扩张的联合作用影响了中国东部的应力场 .爪哇海沟俯冲带的弧后大片地区现今没有强震活动 ,这里的弧后扩张可能是造成东南亚地区物质容易向南运动的因素 .青藏高原内部大致以昆仑山为界 ,北部和东北部是大陆内部的宽阔挤压带 。

Based on the data of earthquake Centroid Moment Tensor solution, P-wave first m o tion focal mechanism solution and deep hole breakouts, a present-day tectonic s t ress map for eastern Asia region is compiled. The original stress data are smoot hed for every 200 km×200 km area by taking the average of all stress indicato r s within each sub-region. The stress map shows the spatial distribution of the o rientation of principal stress axes and the stress regimes An earthquake focal m echanism map for the eastern Asia is also given. The maps of orientation of prin cipal stress axes show that, apart from the strong influence of the collision be tween the Indian Ocean plate and Eurasian plate, the present-day tectonic stres s in eastern Asia is significantly affected by the back-arc extension of the sub d uction zones. The joint effect of the continental collision at the Himalaya arc and back-arc extension in the Burma arc region may be responsible for the remar k able rotation of the principal stress orientations in southeastern part of the T ibetan plateau. The joint action of the collision between the Philippine Sea pla te and Eurasian plate at Taiwan Island and the back-arc extension of the Ryukyu a r c affects the stress field in eastern China. There are no strong earthquakes in the present day in the vast back-arc region of the Java trench subduction zone. The back-arc extension there may create a condition which is favorable to the s o uthward flow of the lithosphere material in southeastern Asia. In the inner part of the Tibetan plateau region, roughly demarcated by the Kunlun Mountain, the n orthern and northeastern part is a broad intracontinental compressive zone, whil e the southern and southwestern part is generally in a normal-faulting stress s tate.