| Περίληψη: |
Among the reported seismic events on the Moon, shallow moonquakes are known for their unique features, such as high‐frequency energy excitation, similarity to intraplate earthquakes, and the largest energy release of all reported moonquakes. Despite these interesting features, a small number of samples (<80 events) and sparse seismic network observations prevented us from gaining an in‐depth understanding of shallow moonquakes. In this study, by using the Apollo 17 gravimeter as a pseudo‐seismometer, we extend the Apollo lunar seismic network and located a few shallow moonquakes more accurately. In addition, comparing the located shallow‐moonquake epicenters with surface/subsurface geological features indicates that at least one event may be better explained by deep‐seated faults within the crust. Along with a previous demonstration of low‐frequency moonquakes, our analysis of high‐frequency events shows that the Apollo 17 gravimeter can serve as a seismometer over a broader frequency range than previously considered. Plain Language Summary: Even half a century after the Apollo seismic observations, new discoveries about lunar seismicity and the internal structure have been reported through the analysis of the Apollo seismic data. Here, we report another progress, especially on understanding shallow moonquakes. Shallow moonquakes are known for their uniqueness in terms of high‐frequency energy excitation, large magnitude, and similarity to intraplate earthquakes. Despite these remarkable features, the detailed nature of shallow moonquakes remains incomprehensible due to the limited number of samples and sparse seismic network observations. In this study, by analyzing the Apollo 17 gravimeter along with Apollo seismometers, we locate a few shallow moonquakes more accurately. Following previous analysis of low‐frequency moonquakes (deep moonquakes), we demonstrate that the Apollo 17 gravimeter is also useful for analyzing high‐frequency events (shallow moonquakes). In addition to the methodological advance, we also provide a new insight into the shallow‐moonquake mechanism by comparing the relocated three shallow‐moonquake epicenters with the spatial distribution of surface/subsurface geological features. Our results indicate that at least one shallow‐moonquake epicenter overlaps with a pronounced gravity anomaly associated with one of the largest dike intrusions in the crust, possibly supporting a deep‐seated fault scenario rather than one related to superficial tectonic processes. Key Points: We relocate three shallow moonquakes by analyzing the Apollo 14, 15, and 16 short‐period seismic data and the Apollo 17 gravimeter dataBy adding the gravimeter data, the shallow‐moonquake sources are located more accurately than those determined using only seismic dataBy comparing relocated shallow‐moonquake epicenters with geological features, we provide new implications for the source mechanism [ABSTRACT FROM AUTHOR] |