Obtaining shear wave input for 1d site response analysis: a frequency adjustment method based on strong motion records – part i: formulation and theoretical validation

Significant discrepancies exist between strong motion records and the actual incident wave field across frequency bands, impacting wave propagation analysis accuracy. This paper proposes a frequency-domain adjustment method (AWIM) to derive realistic incident wave fields from recorded motions. The method constructs site-specific frequency adjustment curves by analyzing the steady-state response of soil layers to harmonic excitations using wave propagation theory and recursive calculations of reflection/transmission across layers. Results reveal that soft soil sites exhibit strong frequency-dependent effects: low-frequency waves undergo significant amplification (nearly twice the incident wave amplitude), while high-frequency waves show complex interactions – distinct bands experience notable amplification or attenuation.