亚洲中东部岩石圈塑性流动网络与构造应力场

PLASTIC-FLOW NETWORKS AND TECTONIC STRESS FIELD IN THE LITHOSPHERE IN CENTRAL-EASTERN ASIA

:板块边缘驱动作用主要通过岩石圈下层的网络状塑性流动实现其向板内的远程传递 ,并控制上层的构造变形。相应地造成构造应力场的的多层分布格局 ,主要包括下层 (含下地壳和岩石圈地幔 )、多震层 (属于上部地壳 )和浅层 (浅表地壳 )应力场。这些层中最大压应力方向可分别采用塑性流动网络共轭角平分线、震源机制解和井孔应力测量等方法加以确定。根据对亚洲中—东部下层与多震层应力场的对比表明 ,大部分地区二者的应力方向基本一致 ,表明了下层对上层的控制 ,这对了解板内应力场的一般趋势与格架提供了基础。靠近驱动边界的局部地段 ,由于上部地壳直接的传递作用 ,往往导致上、下层应力方向的显著偏差 。

The long-range transmission of plate-boundary driving force into the interior of the plate is carried out mainly by the netlike plastic-flow in the lower lithosphere, which controls tectonic deformation in the overlying layers and, correspondingly, results in the formation of multi-layer tectonic stress field in the lithosphere, including the stress fields in the lower lithosphere(i.e. the lower crust and lithospheric mantle), the seismogenic layer(in the upper crust) and the shallow layer(i.e. the shallow and near-surface crust). The maximum compressive stress directions in these layers can be estimated respectively by using the methods of (1) bisecting conjugate angles of plastic-flow network, (2) focal mechanism solutions and (3) in-situ stress measurements in boreholes. The comparison between the stress fields in the lower lithosphere and the seismogenic layer in central-eastern Asia indicates that the stress directions both in them for most areas are identical with each other, showing the control of the lower layer to the upper one, which provides the basis for understanding the general tendency and framework of the intraplate stress field. In addition to these areas, however, some areas closed to the driving boundaries tend to show considerable deviations in stress directions between the lower and upper layers owing to the transmission of plate-boundary driving forces directly along the upper crust, and it is possible to be used as an approach to investigation of the relation and deference between the deeper and shallower layers.