# Seismic Hazard Evaluation and Strain Dynamics in the
## 4 Discussion and Findings
### Spatiotemporal Energy Release Patterns and Geodetic Strain Analysis  
The spatial distribution of earthquakes occurring in and around the SFZ indicates that the highest seismic activity is concentrated near the western branch of the GFZ, which interacts with the Sundirgi segment (Figure 7). This concentration north of the GFZ initially appears with low bandwidths and gradually spreads across the region, predominantly towards the south. Another area where the spatial concentration of earthquakes increases is the northern part of the Simav segment, which generated the Mw 5.8 Simav earthquake in 2011. The intense seismic activity in this region spreads across the area with high bandwidth ranges. Apart from a small cluster at the eastern end of the SFZ, the overall seismic activity in the rest of the study area remains low. In contrast to the spatial density map, the distributions of intensity in the energy map of earthquakes occurring in and around the SFZ are different from each other. The primary reason for this difference is that spatial density maps are generated based only on the number of earthquakes, regardless of their magnitude. However, the energy released by these earthquakes increases logarithmically. When examining the energy density map, an energy corridor extending from the northeastern part of the SFZ toward the GFZ is observed (Figure 8). These findings align with the M \(\geq\) 5 earthquakes occurring in the northern part of the region, and the area where energy intensifies along the corridor is the junction of the Sundirgi and Simav segments. In this area, four M \(\geq\) 5 earthquakes occurred in 1969 and 1970. Similarly, energy released from earthquakes is concentrated in the northern part of the Simav segment, as well as around the EF and its surrounding areas. In this region, there is destructive seismic activity during the instrumental period (Figure 2; Table 2) and three historical earthquake records: an intensity V earthquake in 1728, an intensity VIII earthquake in 1860, and an intensity VII earthquake in 1896. In this study, a temporal energy density analysis of earthquakes was conducted at 10-year periods between 1900 and 2025 to examine the movement of energy flow along the SFZ, for providing essential insights into the dynamics of seismic activity in the region (Figure 9). In the early periods (1900-1940), the regional distribution of energy density appears to be limited to the western part of SFZ only. The temporal and spatial distributions of energy density have shown a distinct geographical shift, particularly after 1960. Before 1960, the intensity of energy density around the GFZ (Gelenbe Fault Zone) indicates that large-magnitude earthquakes occurred further to the west during this period. However, the post-1960 migration of energy accumulation towards the Simav segment and the vicinity of the northern EF (Erdogmus Fault) may be linked to the redistribution of regional tectonic stress accumulation, or it could indicate a dynamic shift in the regional tectonic regime, which might be ultimately leading to the 1970 Gediz earthquake. These shifts can be interpreted as a result of interactions between fault systems or long-term seismic release processes. Temporal trends reveal that, following the 1980s, the substantial energy release from the Gediz earthquake dominated the energy density distribution of the SFZ, resulting in its concentration within the central segments. In addition, the 2011 Mw: 5.8 and 2012 MI = 5.4 Simav earthquakes, which occurred in close proximity to the south of the Gediz earthquake, are also thought to have contributed to the concentration of energy density in this region during the 2000s. This situation suggests that the SFZ (Simav Fault Zone) released its energy through small-to-moderate magnitude earthquakes occurring in its central segments during the 2010s. However, the 2011-2012 earthquakes highlight that the region has not completely lost its potential for producing moderate-to-large magnitude earthquakes and seismic risk continues.