Revisiting SH‐Wave Data Using Love‐Wave Analysis

Although Love waves are widely analyzed in earthquake seismology, there is much less attention on utilizing Love waves than Rayleigh waves by the near-surface community. Unlike incident P and Sv waves, a plane SH wave for a series of horizontal layers refracts and reflects only SH waves, which makes the shallow SH-wave refraction method more popular to define shear (S)-wave velocity in nearsurface geologic applications. For this reason, abundant SH-wave refraction data have been acquired and S-wave velocities have been determined using their first arrivals. If signals are recorded long enough, Love-wave energy can be clearly observed on SH-wave refraction data. Wave conversion may occur in an SH-wave refraction and Love-wave analysis only results in SH-wave velocities, which suggest that we may benefit from revisiting the existing SH-refraction data using multichannel analysis of Love waves (MALW). We used numerical modeling results and real-world examples to demonstrate three advantages of revisiting SH-wave data using the MALW method. Owing to a long geophone spread commonly used in SH-wave refraction survey, a sharp image of Love-wave energy can be generated, allowing better pickings for the phase velocities of Love waves. Because Love waves are independent of P-wave velocity, “mode crossing” in an image of Love-wave energy is less common than in Rayleighwave images. Fewer unknowns in the method MALW make dispersion curves of Love waves are simpler, which leads to more stable inversion of Love waves and reduces the degree of nonuniqueness.