Vulnerability assessment of masonry buildings on slow-moving landslides through 3D displacement

Slow-moving landslides pose prolonged and severe damage to buildings. The assessment of building vulnerability is a critical step in quantifying the risk of slow-moving landslides. Accurately retrieving the real displacement of landslides is essential for developing a more reliable vulnerability model of buildings. However, remote sensing observations acquired from a single orbit are insufficient to capture the three-dimensional (3D) displacement of landslides, which consequently limits the advancement of building vulnerability modeling.

To this aim, this study integrates multi-source displacement monitoring, including synthetic aperture radar (SAR) imagery, optical imagery, and global navigation satellite system (GNSS), to assess the vulnerability of masonry buildings affected by slow-moving landslides. A total of 32 ENVISAT and 193 Sentinel-1A images were collected and processed using the multi-temporal differential interferometric SAR (MT-InSAR) technique to derive the vertical displacement of the landslide. Meanwhile, horizontal displacement was estimated from high-resolution optical imagery through pixel offset tracking. Then the real displacement of landslide can be retrieved by combining GNSS observations. We take 6 slow-moving landslides and masonry buildings on them in the Three Gorges Reservoir Area (TGRA) of China as the research objects. About 50 damaged masonry buildings were found out among near 500 residential buildings on landslides in field survey. These buildings are classified considering crack width on walls. Based on this, we then developed vulnerability curves using Polynomial, Exponential, Logistic, Weibull, and Sigmoid nonlinear regression functions.

The results indicate that building damage responds more acutely to surface deformation in the vertical direction. In terms of fitting functions, the performance of different functions is affected by the choice of intensity parameter. Vulnerability curve derived from cumulative displacement is more suitable for the slow-moving landslides with low temporal heterogeneity in movement. Furthermore, 3D displacement measurements contribute to a comprehensive understanding of landslide movement characteristics and facilitates the development of reliable building vulnerability models. This provides essential guidance for the quantitative assessment of slow-moving landslide risk to buildings.