Evidence of active faulting in the Azarshahr-Tabriz fault zone of northwestern Iran

نوع مقاله : مقاله تحقیقی‌ (پژوهشی‌)

نویسندگان

1 Department of Seismology, Institute of Geophysics, University of Tehran

2 استاد

چکیده

The Azarshahr-Tabriz fault zone (ATF) of northwestern Iran is a poorly known structural assemblage of several fault strands with a variety of extensional and compressional mesoscale structures. The 1641 Dehkhwargan-Tabriz destructive earthquake with estimated surface-wave magnitude of 6.8, is the only recorded seismic event in the region south of the North Tabriz fault (NTF), including Azarshahr, Khosrowshahr and Osku towns of East Azarbaijan province, for which there is a serious ambiguity regarding its causative fault. In this paper, by field survey in an area between Tabriz and Azarshahr and use of satellite imagery and aerial photographs we provide geologic and geomorphic indications to introduce the active fault zone passing through the meizoseismal region of this historic earthquake. Our observations have let us to propose that the ATF is an active left-lateral strike-slip fault zone, conjugate to the well-known NTF, at the northwestern part of Central Iran microplate with a low slip-rate of <1 mm yr−1. Surface topography and tectonic geomorphology of the region suggest that more historical/prehistoric earthquakes may have occurred that have not been documented. The Azarshahr-Tabriz left-lateral fault is therefore important to introduce in seismic risk assessment, especially in rapidly growing provincial capital city of Tabriz (population ~1.5 million).

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Evidence of active faulting in the Azarshahr-Tabriz fault zone of northwestern Iran

نویسندگان [English]

  • Saeid Rahimzadeh 1
  • Yasamin Moshasha 1
1 Department of Seismology, Institute of Geophysics, University of Tehran
چکیده [English]

The Azarshahr-Tabriz fault zone (ATF) of northwestern Iran is a poorly known structural assemblage of several fault strands with a variety of extensional and compressional mesoscale structures. The 1641 Dehkhwargan-Tabriz destructive earthquake with estimated surface-wave magnitude of 6.8, is the only recorded seismic event in the region south of the North Tabriz fault (NTF), including Azarshahr, Khosrowshahr and Osku towns of East Azarbaijan province, for which there is a serious ambiguity regarding its causative fault. In this paper, by field survey in an area between Tabriz and Azarshahr and use of satellite imagery and aerial photographs we provide geologic and geomorphic indications to introduce the active fault zone passing through the meizoseismal region of this historic earthquake. Our observations have let us to propose that the ATF is an active left-lateral strike-slip fault zone, conjugate to the well-known NTF, at the northwestern part of Central Iran microplate with a low slip-rate of <1 mm yr−1. Surface topography and tectonic geomorphology of the region suggest that more historical/prehistoric earthquakes may have occurred that have not been documented. The Azarshahr-Tabriz left-lateral fault is therefore important to introduce in seismic risk assessment, especially in rapidly growing provincial capital city of Tabriz (population ~1.5 million).

The Azarshahr-Tabriz fault zone (ATF) of northwestern Iran is a poorly known structural assemblage of several fault strands with a variety of extensional and compressional mesoscale structures. The 1641 Dehkhwargan-Tabriz destructive earthquake with estimated surface-wave magnitude of 6.8, is the only recorded seismic event in the region south of the North Tabriz fault (NTF), including Azarshahr, Khosrowshahr and Osku towns of East Azarbaijan province, for which there is a serious ambiguity regarding its causative fault. In this paper, by field survey in an area between Tabriz and Azarshahr and use of satellite imagery and aerial photographs we provide geologic and geomorphic indications to introduce the active fault zone passing through the meizoseismal region of this historic earthquake. Our observations have let us to propose that the ATF is an active left-lateral strike-slip fault zone, conjugate to the well-known NTF, at the northwestern part of Central Iran microplate with a low slip-rate of <1 mm yr−1. Surface topography and tectonic geomorphology of the region suggest that more historical/prehistoric earthquakes may have occurred that have not been documented. The Azarshahr-Tabriz left-lateral fault is therefore important to introduce in seismic risk assessment, especially in rapidly growing provincial capital city of Tabriz (population ~1.5 million).

کلیدواژه‌ها [English]

  • Azarshahr-Tabriz fault zone
  • seismogenic fault
  • transtension structure
  • seismic hazard
  • northwestern Iran
  • Osku