Short-term seismicity patterns along the most active faults in Iran

Abstract

In this study, six seismically active fault systems located in different tectonic regimes have been surveyed. The data were from three Persian seismotectonic provinces (Alborz-Azarbaijan, Zagros and East-Central Iran) with different seismic properties, covering a time span of 8 years. The earthquake (Eq.) data have been recorded by the seismological network of the Institute of Geophysics of the University of Tehran, Iran (IGUT), the International Institute of Earthquake Engineering and Seismology of Iran (IIEES), and also include the early large instrumental earthquakes in the Engdahl catalog. During this period, few months of seismic quiescence occurred on the entire length of both Dasht-e Bayaz (DB) and Abiz faults, while most of the moderate and large earthquakes occurred after few months of lack of seismicity on the Main Recent fault, DB, Golbaf and Kazeroun faults. Moreover, single and triple migration patterns of seismicity were regularly seen along Golbaf fault and North Tabriz fault (NTF), respectively. Some large earthquakes (the 2011, MN 5.2 Eq. of Golbaf F. and the 2008, MN 5.2 Eq. of NTF) occurred at the end of these seismicity migration patterns. Along NTF, a diffuse seismicity with no specific seismic pattern has been distinguished. In all the case studies and during the investigated time period the entire lengths of the fault systems were not active at the same time. Finally, there is not a clear relationship between the duration of the seismic gaps and the magnitude of large earthquakes with different co-seismic rupture lengths in depth.