Seismic Gap Analysis on Fault Rupture Zones Using MMI and PGA Data (M≥5, Tehran & Central Alborz)

The historical and instrumental seismic activity in Tehran and the southern Central Alborz indicates that this region is susceptible to a potential future earthquake. Based on this premise, the present study identifies seismic hazard zones associated with seismic gaps and outlines vulnerable areas that could be impacted by a future event. These areas are characterized by soft soils, deteriorating urban infrastructure, and high population density—conditions conducive to strain accumulation and release. Zones exhibiting seismic locking are considered potential sites for significant earthquakes. Although these areas have high seismic potential, major events may not occur for extended periods. However, by considering the length of the rupture zone and the seismic history of the fault, it is possible to estimate the magnitude, probable location, and recurrence interval of the next earthquake. To this end, spectral mapping within a Geographic Information System (GIS) framework was employed to classify the ruptured fault zone using seismic intensity data derived from the Modified Mercalli Intensity (MMI) scale, based on strong ground motion (PGA) records. This dataset served as a layer of information for identifying seismic gaps likely associated with future events. Considering the distribution of related earthquake events, the Modified Mercalli Intensity zones near the causative fault can be identified as the rupture zones potentially triggering a future earthquake, thereby determining seismic gaps in the Tehran region.Based on thisanalysis, three zones, labeled "A,B and C" were identified. With The occurrence of an earthquake in southern Tehran validating zone "B".