地幔快速隆起对构造地震的触发作用

THE TRIGGER ACTION OF THE QUICKLY UPLIFTED MANTLE FOR THE SHELLOW TECTONIC EARTHQUAKE

摘要:

本文应用弹性半无限空间内均匀膨胀的球体对球上介质的作用,作为地幔快速上涌触发构造地震的力学模型。按照地面垂直位移的年变化率,利用这个模型反推出这种虚拟的膨胀球的半径和澎胀强度。並计算出它在地壳中产生的附加应力。尽管此种附加应力比驱动地壳水平运动的力要小得多,但它能在高倾角断层上引起张性的法向应力,而且在隆起区内还有较高的附加剪应力。这些应力比固体潮、地极移动和地球转速变化等因素产生的附加应力都大得多。因此,地幔快速上涌对构造地震的触发作用应该比上述诸因素更大。由于近十余年来我国不少地区的走滑型强震大都发生在地壳上隆区或者在其边缘,而且发震断层都是高倾角断层,因此,本文能够对此作粗浅的解释。

Abstract:

A homogeneous dilated sphere in the hemi-infinite elastic space is ta-ken as the mechanical model of the quickly uplifted mantle.With this model the radius and the dilative intensity of the sphere can be com-puted from the value of the vertical displacement on the earth's surfa-ce.The supplementary stress deduced from the uplifted is determined.The computing result showes that the deduced stress on the fault with high inclined angle is tensile,but the shearing stress is also found in the upliftel region of the earth's crust.The amount of these stresses deduced from the quickly uplifted mantle greatly overcomes the stresses deduced from the gravimetric earth-tide,the diviation of the polar axis and the variation of rotational velocity of earth.Consequently,the quickly uplifted mantle has more trigger action than above-menti-oned factors for the occurance of the shallow tectonic earthquake.Ow-ing to the fact that many large earthquakes occur ed recently in China have been affected in the uplifted region of earth's crust or in its ne-ighborhood and these earthquake faults have high inclined angle,their occurance can be explained by the results described in this paper.