Garmkhan Earthquake of 04 February 1997, Mw 6.6

Garmkhan Earthquake of 04 February 1997, Mw 6.6

At 10:37:47 UTC on Tuesday, 4th February 1997, an earthquake with magnitude of Mw=6.6 and epicentral coordinates 37.71N and 57.49E occurred in Garmkhan mountainous area about 30 kilometers north of the Bojnord city in Northern Khorasan Province. Due to the earthquake, 84 people were killed. The event was associated with a strong foreshock that led to relatively less loss of lives. More than 170 villages were damaged and three villages containing Naveh, Ghezel Ghan and Sheikh were 100% destroyed. The strong motion of the event was recorded in 14 stations of the Iran Strong Motion Network (ISMN) including Ashkhaneh, Kalaleh, Maraveh Tappeh, Raz, Rezvan, Emam Gholi, Neyshaboor, Barezoo Dam1, Gonbad-e-Kavoos, Mashhad1, Robat^*, Farooj^*, Gifan^* and Bojnoord^* in which maximum corrected PGA=192 cm/s² was recorded in the Bojnoord^* station. Hollingsworth et al. (2007) showed that the earthquake resulted from almost pure right lateral strike-slip motion (0.5–1.0 m), which ruptured a ∼15 km long section of fault, striking ∼340° at its northern end, which changes to ∼320° at its southern end. The village of Sheikh lies ∼10–15 km SE of the fault rupture, yet was severely damaged during the earthquake. Analysis of strong-motion records, particularly their significant duration, the polarization of the fault-normal component, and the velocity pulse, indicates a probable directivity effect, in which the rupture propagated from north to south, towards the village of Sheikh.

Reference:

• Hollingsworth J., Jackson J., Alarcon J., Boomer J., and Bolourchi M.J, (2007), “The 4th February 1997 Bojnourd (Garmkhan) earthquake in NE Iran: Teleseismic, and strong-motion evidence for rupture directivity effects on a strike-slip fault”, Journal of Earthquake Engineering, 11: 193-214, DOI: 10.1080/13632460601031078.

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