Breaking the Black Box: Inherently Interpretable Physics‐Constrained Machine Learning With Weighted Mixed‐Effects for Imbalanced Seismic Data

Abstract Ground motion models (GMMs) are critical for seismic risk mitigation and infrastructure design. Machine learning (ML) is increasingly applied to GMM development due to expanding strong motion databases. However, existing ML‐based GMMs operate as “black boxes,” creating opacity that undermines confidence in engineering decisions. Moreover, seismic data sets exhibit severe imbalance, with scarce large‐magnitude near‐field records causing systematic underprediction of critical high‐hazard ground motions. Despite these limitations, research addressing both interpretability and data imbalance remains limited. This study develops an inherently interpretable neural network employing independent additive pathways with novel HazBinLoss and concurvity regularization. HazBinLoss integrates physics‐constrained weighting with inverse bin count scaling to address underfitting in sparse, high‐hazard regions. Concurvity regularization enforces pathway orthogonality, reducing inter‐pathway correlation. The model achieves robust performance: mean squared error = 0.6235, mean absolute error = 0.6230, and coefficient of determination = 88.48%. Pathway scaling corroborates es