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Speaker: Alice Turner, Postdoctoral Fellow, University of Texas Institute for Geophysics

Host: Sean Gulick

Title: Lunar tectonics – insights from deep and shallow moonquakes

Abstract: During the 7-year operation of the Apollo seismic network, researchers detected and cataloged tens of thousands of seismic signals. This included signals from impacts, as well as shallow and deep moonquakes. The lunar seismic activity detected by these instruments, which are over 50 years old, still offers valuable information about the moon’s tectonics and dynamics. In this talk, split into two parts, I will discuss my work to unravel some of the puzzles of deep and shallow moonquakes.

Firstly, I will focus on deep repeating moonquakes. Deep moonquakes occur in clusters at 700–1,200-km depth and provide unique insight into the stresses deep in the lunar interior. Using observations of deep moonquake waveforms, I find tidal stresses to be the main driver of deep moonquakes. Based on these results, I intend to discuss the potential implications for lunar structure and the mechanism of deep moonquakes.

Secondly, I will focus on my recent work here at UTIG on shallow moonquakes. Classifying seismic signals correctly is key for evaluating the moon’s impact and seismicity rates. Yet, 60% of the original Nakamura et al. (1981) catalog events remain unclassified because the highly scattered lunar waveforms appear visually similar. In this work, we have developed a precise and quantitative method to distinguish between shallow moonquakes and impacts. Our preliminary results identify six features that differ between shallow moonquakes and impacts and suggest we may robustly and semi-automatically classify new or previously unclassified events.

Finally, I present my current and future research directions.