# Seismic Hazard Evaluation and Strain Dynamics in the
## 4 Discussion and Findings
### Earthquake Recurrence Intervals and Seismic Risk  
Earthquake recurrence describes the interval between the consecutive events occurring on a fault zone or a specific segment, representing the duration of the seismic sequence, and plays a crucial role in seismic hazard analysis. Determining the earthquake recurrence period provides important information for assessing the seismic potential of a region and evaluating seismic risks. This period helps predict the time of future earthquakes in seismic hazard analyses and provide guiding inputs for the safe design of infrastructure and settlements in the stage of local and regional planning. Recurrence periods, which model the temporal distribution of earthquake hazard, also serve as a significant indicator for understanding fault dynamics and stress accumulation, contributing to the identification of increasing seismic risk in regions where no major earthquakes have occurred for an extended period. This study estimates the recurrence periods of earthquakes for the SFZ as 32 years for M = 5, 165 years for M = 6, and 982 years for M = 7.1 (Figure 6). Considering that the relatively short recurrence periods obtained are related to the presence of moderate-sized earthquakes (low \(b\)-values) and partly to the high seismicity rate (high \(a\)-value), it is thought that the a and b parameters obtained from the study align with the stress distribution of the seismic environment in the study area [140]. Although these periods, derived from empirical relationships and past earthquakes, are considered predictions based on the analysis, it can be argued that the risk in those areas rises if no earthquake occurs beyond the expected time frame. The earthquakes that occurred in the historical and instrumental periods in and around the SFZ (Table 2) indicate significant seismic activity in the region. Additionally, the series of Simav earthquakes in 2011 (19 May 2011, Mw: 5.8; 27 June 2011, M: 5.0; 3 May 2012, MI: 5.4) clearly highlight the seismic activity of the SFZ, underscoring the earthquake risk in the region. The results indicate that while moderate-sized earthquakes occur frequently in the Simav and surrounding settlements, a longer period of stress accumulation is required for larger earthquakes to occur. Evaluations made after the 2011 Simav earthquake, one of the region's most recent destructive earthquakes, revealed that the region is easily affected by moderate-sized earthquakes. The damage caused by this earthquake had significant effects on the settlements and infrastructure. Although the earthquake was classified as moderate, it was strongly felt over a wide area and caused significant damage to concrete structures, leading to the collapse of more than 300 buildings and rendering thousands of others severely impaired and unsafe for use. The massive damage caused by this moderate earthquake in the region is largely due to the alluvial fan covering the underlying soil of Simav and its surroundings, which amplified the earthquake's intensity [116; 142]. Considering the short recurrence intervals of moderate earthquakes obtained in this study, it is believed that the densely populated areas and surrounding regions, situated on Quaternary-aged alluvium transported by nearby lakes and rivers, face significant risk due to unconsolidated soil characteristics and the existing building stock in the area.