太阳物理研究组知识库

大量研究表明深源月震的周期性是由地球对月球的潮汐作用引起，但固体潮汐差应力的最大值远小于深源月震发生所需的岩体破裂应力，因此在潮汐力以外，应存在其他背景构造应力.此外，由于月球上并没有活跃的板块运动，浅源月震的发生机制也有待解决.本文用参量化模型初步模拟了月球冷却和岩石圈增厚的历史，并初步计算了月球内部的热应力增长速率以及长期应力松弛下累积至今的热应力，特别关注了深、浅源月震区域近期应力特征.研究结果显示：浅源月震区域内，热应力大小可以造成浅源月震区岩体破裂，且热应力以水平挤压为主，足以产生逆掩断层月震，与实际观测吻合；深源月震区域内，热应力虽然也有集中，但其量级大小并不足以成为造成无水干月岩破裂的主要原因.我们推测深源月震很可能与月幔最下层的部分熔融层释放的流体有关.本文的研究初步揭示了月球冷却收缩热应力与深、浅源月震产生机理间的关系，对未来的进一步深入研究提供了基础. 

Numerous studies have shown that the periodicity of deep moonquakes is caused by the tidal force from the earth to the moon. However, the maximum tidal stress is too small to cause rock fracture for the occurrence of deep moonquakes, which indicates that there should be other background stresses. Due to the lack of plate activity, the mechanism of shallow moonquakes also remains to be resolved. We developed a parameterization scheme to simulate the cooling history of the moon. The thermal stress accumulated after a short period of time is calculated, as well as the long-time thermal stress with relaxation. We pay special attention to the characteristics of recent stress accumulation in the deep and shallow moonquake zone. The study shows that thermal stress in the shallow moonquake area causes mainly horizontal extrusion, resulting in overthrust fault moonquakes, which is consistent with observation. Although the thermal stress concentrates in the deep moonquake area either, it is not sufficient to cause the failure of dry rocks. We speculate that the fluid from the part melt layer may be a possible origin of deep moonquakes. The results in this article preliminarily reveal the relationship between the thermal stress and the mechanism of deep and shallow moonquakes, which may be helpful for future analysis of these two types of moonquakes.