The 20 June 2025 Mw 4.9 Event in the Central Alborz, Iran: A Rare Normal-Faulting Earthquake Within a Complex Transpressional Regime
Abstract
Abstract On 20 June 2025, an Mw 4.9 earthquake struck the central Alborz Mountains in northern Iran. Using high-quality broadband data from in-country seismic stations, we estimated source mechanisms using different estimation approaches. All approaches consistently yielded a double-couple normal-faulting solution at 7–8 km depth. This event is anomalous for the region because the Alborz accommodates deformation primarily through thrust and left-lateral strike-slip faulting within a complex transpressional regime. The earthquake is the first significant normal-faulting event in the central Alborz in 37 yr. Its mechanism provides the best-constrained and most direct seismological evidence of extensional tectonism within the transpressional central Alborz Mountains, in agreement with previous geological observations and geodynamic models.
Fields of Study & Subjects
earthquake and tectonic studies
High-pressure geophysics and materials
Geological and Geophysical Studies Worldwide
Publication details
- Journal / source
- The Seismic Record
- Publisher
- Seismological Society of America (SSA)
- Volume
- 6
- Issue
- 1
- Pages
- 54–64
- Publication date
- 1 January 2026
- Language
- EN