The 2002 June 22 Changureh (Avaj) earthquake in Qazvin province, northwest Iran: epicentral relocation, source parameters, surface deformation and geomorphology

SUMMARY The M w 6.4 Changureh (Avaj) earthquake occurred on 2002 June 22, in Qazvin province, northwest Iran. We use observations from seismology, field investigation and analysis of satellite imagery and digital topography to suggest that slip on a previously unrecognized thrust fault (herein named the Abdarreh fault) was responsible for the earthquake. Inversion of longperiod P and SH body wave seismograms shows rupture on a thrust fault dipping 49 ◦ to the southwest and with a centroid depth of ∼10 km. Multiple-event relocation of the main shock and aftershock epicentres and discontinuous surface ruptures observed after the earthquake are compatible with a northwest-propagating rupture on a southwest-dipping thrust, but maximum recorded displacements are much less than expected from seismology, suggesting that much of the slip failed to reach the surface and was accommodated as folding at the surface instead. Long-term folding is difficult to see in the topography of the epicentral region as the Abdarreh fold is growing through a relict Neogene topography. Anticlinal uplift can, however, be inferred from drainage disruption and stream incision. The 2002 June 22 Changureh earthquake shows the importance of being able to interpret diagnostic features of active faulting in the landscape.

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