Experimental Evaluation of DAS Under Strong Shaking and Interpretation of Observed Strain Signals via Internal Cable Modeling

Abstract Distributed Acoustic Sensing (DAS) is particularly useful for linear and spatially extensive infrastructure systems such as railway networks. To enable the effective use of DAS in earthquake early warning and disaster response applications, it is essential to understand its performance under strong‐motion conditions. However, its behavior during strong shaking is still not well understood. This study investigates the performance of DAS under strong‐motion conditions using large‐scale vibration table experiments and numerical modeling. In these experiments, a fiber‐optic cable was affixed to a shaking table and subjected to sinusoidal excitation. Remarkably, the DAS recorded measurable strain rate signals, even though the fiber moved nearly as a rigid body. At input accelerations below 400 cm/s 2 , a linear relationship was observed between the strain rate and the co‐located MEMS accelerometer data. However, this relationship deteriorated above 400 cm/s 2 despite the absence of cycle skipping, suggesting nonlinearity in the cable response. A simple numerical model was developed to clarify how strain is recorded during the shaking‐table experiments, which assumes partial bonding between the fiber core and the outer jacket. The model represents this internal structure using Voigt elements—parallel combinations of springs and dashpots—between the core and the jacket. Simulations demonstrated that internal viscoelastic relaxation can produce measurable strain rate signals with phase coherence across adjacent DAS channels without wave propagation. These results successfully reproduced key experimental features, suggesting that internal cable mechanics, alongside wave propagation and external coupling, play a significant role in the overall strain measurement mechanism of DAS.