Constraining lunar lower-mantle attenuation using ScSH-SH amplitude ratios

Summary Seismic attenuation in lunar lower mantle can provide critical constraints on thermal state and composition of the deep interior; however, previous estimates based on path-integrated amplitudes are strongly influenced by near-surface scattering, especially for narrow-band waveforms recorded by Apollo’s sparse seismic stations. Here we show that the amplitude ratio between ScSH and SH from the same station can mitigate this limitation. We measure these ratios from narrow-band records and invert for lower-mantle Q by matching them with synthetic predictions that account for geometric spreading, source radiation, and interface transmission. Synthetic tests verify that the method recovers Q within 10 per cent for SNR ≥ 10 and remains robust to scattering and source mechanism uncertainties. Application to a terrestrial deep earthquake recovers Q = 308 (IQR: 280–340), consistent with the PREM reference value (Q ≈ 312), confirming its feasibility on real data. Application to Apollo deep moonquake records (10 stacked records) shows that the amplitude ratios exhibit the expected single-peak distance trend and yield broadly consistent Q estimates across narrow bands, though the limited data warrant interpreting these results as a feasibility demonstration. This framework provides a practical and complementary constraint on lunar lower-mantle attenuation and is transferable to other planetary datasets with similar data limitations.