Scientific Quarterly Journal of Geosciences

Scientific Quarterly Journal of Geosciences

Pattern of Seismicity in Northwest Iran, Revealed from Local Seismic Network

Document Type : Original Research Paper

Authors
Mohammad Reza Gheitanchi 1
Nourbakhsh Mirzaei 2
Esmaeil Bayramnejad 2
1 Institute of Geophysics, Tehran University, Tehran, Iran
2 Institute of Geophysics, Tehran University, Tehran , Iran
Abstract
Historical background and instrumentally located earthquakes as well as the geological evidences all suggest that northwest Iran is one of the seismically active regions in the Middle East. The destructive Rudbar-Tarom earthquake of 1990 indicated the need to install a permanent seismological network in the region. In 1995 the Institute of Geophysics of Tehran University deployed a telemetric seismic network in NW Iran to monitor local earthquakes. Relying on the records obtained during this period, several seismically active areas were identified. The epicenters of local earthquakes are in agreement with the NW-SE trending major faults. The distributions of earthquakes in east and west parts are consistent with the related major faults (Astara- Rudbar faults in east and Orumiyeh fault in west). A kind of seismic quiescence exists in central part around Tabriz. A similar situation could be observed along the Astara fault in the east. The majority of events are shallow indicating that the seismic activity is mainly taking place in upper crust and the seismogenic layer has a thickness of about 20 km. Taking into account the background seismicity and present pattern of seismicity, the occurrence of a major earthquake in northwest Iran is expectable.
Keywords
active tectonics
historical earthquakes
seismicity of northwest Iran
microearthquakes
local seismic network
seismic gap

Subjects

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Scientific Quarterly Journal of Geosciences
Volume 13, 49-50
Autumn & Winter 2004, Vol. 13, No. 49-50
Winter 2004
Pages 104-111