Exploring Spatiotemporal Trends of Earthquake Activity in the Iranian Plateau through Space-Time Cube Analysis

Abstract. This study investigates the spatiotemporal trends of seismicity in the Iranian plateau over a 50-year period (1972–2021). To facilitate this analysis, the study region was divided into grids of 50 km, 75 km, and 100 km quadrangles. Earthquake data for each quadrangle were extracted, and quadrangles lacking sufficient data (i.e., fewer than five events over the study period) were excluded to ensure statistical validity. The Space-Time Cube (STC) model was employed to integrate spatial and temporal information, while the Mann–Kendall non-parametric test was used to detect monotonic trends in earthquake frequency within each quadrangle. A 95% confidence level (p < 0.05) was used as the threshold for identifying statistically significant trends. The resulting seismicity pattern maps categorized the quadrangles into three groups: no significant trend, increasing trend, and decreasing trend. Comparative analysis indicates that, across much of Iran, seismicity shows no significant temporal trend during the studied period. However, an increasing trend is evident in several quadrangles—predominantly in the Zagros fold-and-thrust belt, a region known for active convergence and crustal shortening. Conversely, decreasing trends are mainly observed in eastern and central Iran, including parts of the Lut and Central Iranian blocks, where recent major seismic activity appears to have declined. Sensitivity analysis using different spatial and temporal resolutions confirmed the robustness of these results. Overall, the findings suggest stable and spatially coherent seismicity trends, with localized zones of activity that correspond well with major tectonic structures. These insights provide a quantitative basis for linking long-term seismicity evolution with underlying geodynamic processes and contribute to improved regional seismic hazard assessment.