A parameterization model to analyze lunar thermal history and thermal stress for inducing moonquakes

Abstract:

The lunar seismometers placed on the moon during the Apollo program recorded a large amount of lunar seismic data, among which the most special were deep moonquakes, which periodically occur at depths of 700 to 1200 kilometers. Previous studies have shown that the periodicity of deep moonquakes is triggered by tidal force of the earth. However, the maximum tidal stress is much less than the stress required for the occurrence of deep moonquakes, which indicates that there should be another background stress besides tidal force. Different from deep moonquakes, shallow moonquakes seldom happen and have no obvious periodicity, but their magnitude is much larger than deep moonquakes. The mechanism of shallow moonquakes is not clear yet. In this study, a novel parameterization lunar model was developed to exploring the cooling history and the thermal stress accumulation history of the moon. The simulation results show that 1) the thermal stress can make significant contributions to the occurrence of both deep moonquakes and shallow moonquakes, and 2) the accumulation rate of thermal stress can provide sufficient elastic energy for the occurrences of deep moonquakes and shallow moonquakes which is helpful for understanding the long-term lunar dynamic evolution in the mantle.