Search Results (2)

The Alborz mountain range in northern Iran is part of the active and seismic Alpide belt, where assessing seismic hazards is crucial due to the region’s history of large instrumental earthquakes and destructive seismic background. Moment rate estimation, which quantifies tectonic activity, offers a novel approach to understanding the energy potential of active tectonic regions. In this study, a regional perspective is employed to investigate the maximum horizontal acceleration for Tehran, the major city in Alborz, resulting from the Sorkh-e Hesar and Ghasr-e-Firuzeh faults located approximately 7.5 km southeast of Tehran. These faults have a seismic potential of Mw 6.5 and a gravity of ~0.5723. While previous studies have identified faults in northern Tehran as the greatest seismic risk, our findings suggest otherwise. The calculated geological moment was 5.18218 × 10¹⁷ Nm/y, with a seismic moment rate of 1.83375 × 10¹⁴ Nm/y, providing valuable insights into fault activity and seismic potential in the study area. Full article

This study provides a multi-disciplinary overview of the seismology and geodetic data with tectonics analysis in order to provide an evaluation of stress trajectories, and probabilistic fault rupture hazard assessment. Based on the different scenarios obtained from the comparison of several overviews and their interpretation, we investigated the kinematics and active tectonics of different structural zones. In this study, the magnitudes and directions of seismic and geodetic strain rates (SSR and GSR) were evaluated using reliable earthquake focal mechanisms and all available GPS data (1999–2015) in the structural subzones of northern Iran, where have experienced more than 14 strong instrumental earthquakes (Mw ≥ 6). In addition, a tectonic stress model was inferred from the Focal Mechanism Stress Inversion (FMSI). The new crustal stress map was proposed by the weighted average analysis of the SSR, GSR, and FMSI. N35.5° E and N104° E were estimated for the Alborz and Talesh mountains, respectively. The numerical analysis of stress regimes confirms the slip partitioning mechanism of oblique shortening on the sub-parallel thrusts and strike-slip faults in the area. Four main stress regime categories were defined, including thrust (49.37%), strike-slip (39.24%), thrust with a strike-slip component (2.53%), normal (1.27%), and unknown faulting (7.59%). Seismic and geodetic moment rates (SMR and GMR) and their comparison were also calculated in order to evaluate the function of these parameters in determining the seismicity arrangement. The ratio of the seismic/geodetic moment rates for the area is ~70.7%. This ratio for the Alborz, western Koppeh-Dagh, north part of Central Iran, South Caspian Basin, and Talesh is ~0.9, 0.3, 11.9, 0.3, and 57.3, respectively, which indicates the most elastic energy has been released in the Talesh and the north part of Central Iran. The comparison of geodetic moment rates in the subzones of the area indicates that geodetic deformation is high in the Central Alborz (networks 8, 9, 17) and western Koppeh-Dagh (networks 5, 13). Full article