Abstract. Geo-social media posts can provide valuable real-time
information during natural disasters. However, assessing their relevance
for emergency response remains difficult. Most existing approaches
simplify relevance into discrete classes. To incorporate space and time,
they typically rely on manually engineered distance features,
overlooking the non-linear effects of spatial and temporal proximity.
This study introduces a more fine-grained approach for multimodal
relevance assessment that integrates spatio-temporal decay
transformations with ordinal regression. Using a multilingual,
geo-referenced X (formerly Twitter) dataset spanning floods, wildfires,
and earthquakes, we evaluated four decay transformations and
reformulated relevance assessment as a regression task. A stretched
exponential decay function best captured the non-linear decline of
relevance with increasing spatial and temporal distance. Incorporating
decay-transformed features into a multimodal meta-learning framework
improved both prediction performance and stability. Reformulating the
task as a regression problem reduced RMSE and increased R2 compared to
classification, with Support Vector Regression (SVR) achieving the
strongest results (RMSE: 0.231, R2: 0.617). Granularity and entropy
analyses revealed that regression provided much finer relevance
estimates than classification. Overall, our research presents a first
step towards making insights from social media more actionable and
decision-ready for disaster response. Reproducibility review available
at: https://doi.org/10.17605/OSF.IO/ZPURT