The Influence of Moho Reflection on Ground Motion: A Case Study of the 2023 Ms 4.7 Pulandian, Liaoning, Earthquake

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Abstract
The significant amplification of ground-motion records associated with Moho-reflected S waves (SmS) has been well documented in previous studies. The deployment of the Chinese earthquake early warning system has provided denser station coverage, enabling deeper investigation into SmS behavior, particularly the interaction between local site effects and successive SmS arrivals. During the 2023 Ms 4.7 earthquake in Pulandian, Liaoning, peak ground acceleration was notably enhanced at stations located approximately 80 km from the epicenter. The reflected SmS exhibited an average peak amplitude 1.86 times that of the direct S wave. Notably, northeastern stations exhibited amplification, with SmS amplitudes reaching up to approximately eight times that of the S wave. Further analysis suggests that resonance between the SmS dominant frequency and the fundamental site frequency contributed to additional ground-motion amplification. These results imply that current ground-motion prediction equations may underestimate the structural damage potential associated with SmS waves in the far field. However, incorporating such effects into prediction equations is not straightforward, as it requires more detailed constraints on crustal velocity structure, source depth, and 3D path effects.

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