Spatial heterogeneity of stress and attenuation data revealing the Complex seismotectonic nature of the Central Alborz

Spatial heterogeneity of stress and attenuation data revealing the Complex seismotectonic nature of the Central Alborz

The Alborz is one of the most seismically active seismotectonic provinces in Iran. Furthermore, the existence of Tehran in this range intensifies the seismic hazard in it. In this study, a new method is introduced for stress mapping. The SHmax values in the Alborz region extracted from earthquake focal mechanism data are mapped by using this new approach. The attenuation of coda waves, Qc, is also estimated in this region, using a single back-scattering model of S-coda envelopes. The results show substantial variation in SHmax directions, which reflects the complicated tectonic nature of the region. The average Qc values estimated and their frequency-dependent relationships also correlate well with a highly heterogeneous and highly tectonically active region. From the stress studies point of view, in the central Alborz, more small-area and localized anomalies in maximum horizontal stress direction are observed, emphasizing the heterogeneity of the stress field. Qc results also show that the attenuation is higher in the central region of Alborz compared to other areas. Thus, both approaches confirm the high seismotectonic complexity in the central Alborz which necessitates more studies in this region for seismic hazard and risk mitigation purposes.