Hamid Nazari; Jean-François ritz; Magali Rizza; Reza Salamati; shenon mahan; mohammad ali shokri; J-L Michelot; m Massault; mohammad foroutan; Shirin Zarei
Abstract
The Astaneh Fault is classically described as the source of the most destructive seismic event in the history in Northeastern Iran, the 856 CE Qumis earthquake with an estimated magnitude ...
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The Astaneh Fault is classically described as the source of the most destructive seismic event in the history in Northeastern Iran, the 856 CE Qumis earthquake with an estimated magnitude between 7.4 and 7.9. In this article, based on the results obtained from paleoseismological researches from trenches AT1, AT2, AT3, AT4 and AT5 along the Astaneh Fault, we will determine the magnitude of past earthquakes and their aftershocks. The paleoseismological study along the fault in the two argillic sagpond of Playa and Graben structures provides evidence of 5 to 8 earthquakes in the past, which were determined by using the luminescence and radiocarbon age dating. The youngest seismic rupture was observed in the AT5 trench in the period of 700 ± 20 years BP and 1370 ± 140 years IRSL age, which can be consistent with the historical rupture of the Qumes earthquake. Analysis and measurement of morphological analysis along the fault zone estimates the equivalent displacement of 3.9±0.3 meters for the penultimate earthquake. The surface rupture indicates a moment magnitude between 7.3 and 7.5, comparable to the magnitude estimated for the historical 856 Qumis event. The distribution of past events over time shows a quasi-periodic seismic pattern with a mean return period of 1800 ± 230 years
