عنوان مقاله [English]
The Feb. 4, 1997 Bojnourd earthquake of M 6.8 occurred in a mountainous area, North-East Iran, and caused extensive destruction. Relatively a fewer human lives were
lost due to a strong foreshock. Field investigation and aftershocks distribution suggest a NW-SE faulting with a right-lateral strike-slip motion. Aftershock activity was
scattered indicating that the mainshock activated the nearby minor faults. Aftershocks extended to a length of 45km and a depth of 20km. The average stress drop was
estimated to be 20 bar and the static displacement was 35 em. Great destruction in the
affected area was mainly caused by poor seismic resistance of traditional adobe houses.
Well designed buildings in the epicentral region survived with minor damage. The ground-motion characteristics during the mainshock should be considered for the high
safety design of structures in the damaged area.