中国岩石层底面地幔对流状态的探讨

本文应用卫星测量地球重力场的球谐函数系数和地幔流体力学方程,计算了中国地区岩石层下的地幔对流状态。计算中选用了三种不同的模式:模式Ⅰ,完全场（2-30阶）;模式Ⅱ,高阶场（13-25阶）;模式ⅢI,低阶场（4-18阶）。其目的是探求一种与我国地质和地球物理实测资料相符合的最佳模式。考虑到岩石层厚度与所假定的地幔对流区厚度相比是很薄的,因而可以把地幔流对岩石层底面产生的拖曳力近似地看作岩石层内构造力。将上述三个模式分别与中国及邻区的131个地震（1961-1977,M≥5）震源机制解和近代地质构造形变等资料进行比较。结果表明,模式Ⅰ与我国大多数地区的实测资料符合得最好,该模式所显示的地幔对流特征与相应各地区近代构造运动特点相符。模式Ⅰ为探讨近代构造运动的力源问题,提供了新的线索。

MANTLE CONVECTION PATTERN UNDER LITHOSPHERE OF CHINA

We have applied the harmonic coefficients of Earth's gravity field from satellite measurements and hydrodynamical equations for the earth mantle and calculated three mantle convection models: model Ⅰ, complete field （2-30 degree）; model Ⅱ, higher field and model Ⅲ, lower field. To choose an appropriate one from the three models, we compared them with the focal mechanism solutions for 131 earthquakes （1961-1977, M≥5） and the features of recent tectonic movements in China. The results show that model I is better consistent with geophysical and geological observation data than model Ⅱ and model Ⅲ.