基于数值模拟的潮汐应力触发月球深震机制的探讨

A discussion about how the deep moonquakes are triggered by tidal stress

月震发生在约700~1 200 km的深度,且具有27天多的活动周期.本文对月球所受地球引力而产生的固体潮汐作用的位移场和应力场进行百万网格的并行有限元方法计算模拟.计算结果显示最大剪应力随深度变化,如果月球可能有半径为700 km左右的液态核,或者虽然月核较小,但月幔底部处于部分熔融状态,则月震发生深度恰好就是剪应力最大的深度.月核是否存在一直没有直接的地震学观测证据,本文的计算从另一个角度在一定程度上支持了液态月核可能存在的观点.

Most moonquakes recorded are deep moonquakes that occur at depths of 700-1 200 km,and have a period of about 27 days. We use parallel finite element method and a model with million grids to simulate the tidal stress field and displacement field of the moon numerically. The results show that the maximum shear stress varies with depth. If the moon has a liquid core with a radius of about 700 km or if the moon has a smaller core but the materials at the bottom of lunar mantle are partially molten,the depth of the maximum shear stress will coincide with the depth of the deep moonquakes. The proposition that the moon has a core is lack of sound seismological evidence. Our calculation provides another approach and our result inclines to the suggestion that the moon has a liquid core.