Seismic Site Response of Lunar Regolith: One-Dimensional Equivalent Linear Analysis of Apollo Landing Sites

Elizabeth Yoseph, Rashid Shams, & Chukwuebuka C. Nweke

Submitted August 30, 2026, SCEC Contribution #15312, 2026 SCEC Annual Meeting Poster #TBD

Understanding how near-surface lunar regolith modifies seismic ground motion is critical for the structural design of long-duration habitats, precision instrument deployment, and landing-site selection under Artemis and future lunar surface missions. Despite the wealth of geotechnical data returned by Apollo missions, only Apollo 17 recorded a shear-wave velocity profile, and no mission produced layered soil models suitable for engineering site response analysis. One-dimensional regolith profiles were developed for Apollo 11 through 17 using layer thickness, bulk density, and shear-wave velocity data. For Apollo 11 through 16, shear-wave velocities were assigned consistent with published site-level velocity ranges and expected stiffness increases with depth. For Apollo 17, the velocity structure from the Lunar Seismic Profiling Experiment was discretised into a simple layered model. A uniform small-strain damping ratio of 2.5% was applied across all layers following equivalent-linear assumptions for dry granular soils. Two independent equivalent-linear site response simulations were used to compute theoretical transfer functions, with results cross-validated to confirm methodological consistency. The analyses indicate substantial amplification within the shallow lunar regolith at all Apollo landing sites. Mare landing sites exhibit stronger resonance at lower frequencies, whereas highland sites show peak amplification at higher frequencies, reflecting their denser and stiffer near-surface materials. Sensitivity analyses using multiple input ground motions demonstrate that induced shear strains remain well below the threshold for significant nonlinear behaviour, with shear modulus retention exceeding 89% across all layers. These findings support the applicability of the equivalent-linear framework for the range of shaking levels considered. The low sampling rate of the Apollo seismometers limits recoverable frequency content to below the fundamental resonance frequencies identified through numerical simulation, revealing a critical instrumentation gap motivating future reprocessing efforts. Future work will focus on recovering higher-frequency content from the moonquake records, expanding shaking scenarios to evaluate nonlinear regolith response, and developing lunar-specific modulus reduction and damping curves to replace terrestrial assumptions currently applied in the absence of direct laboratory measurements.

Citation
Yoseph, E., Shams, R., & Nweke, C. C. (2026, 08). Seismic Site Response of Lunar Regolith: One-Dimensional Equivalent Linear Analysis of Apollo Landing Sites. Poster Presentation at 2026 SCEC Annual Meeting.

Related Projects & Working Groups
Ground Motions (GM)