Open AccessBasement faulting and the focal depths of the larger earthquakes in the Zagros mountains (Iran)
Author(s) -
Jackson James,
Fitch Thomas
Publication year - 1981
Publication title -
geophysical journal of the royal astronomical society
Language(s) - English
Resource type - Journals
eISSN - 1365-246X
pISSN - 0016-8009
DOI - 10.1111/j.1365-246x.1981.tb02685.x
Subject(s) - geology , seismology , basement , subduction , induced seismicity , crust , sedimentary rock , thrust fault , thickening , continental collision , fault (geology) , paleontology , tectonics , chemistry , civil engineering , polymer science , engineering
Summary. The present day seismicity of the Zagros seems to occur on high angle reverse faults distributed across the whole width of the belt. It does not indicate activity on a single inclined thrust surface and there do not seem to have been any well located events at intermediate depths. Modelling of the long period teleseismic body waves of seven large earthquakes presented here shows their focal depths to be in the range 8–15 km. This is thought to indicate faulting in the uppermost basement beneath the sedimentary cover, though the absence of published seismic refraction results renders the sediment thickness uncertain. Faulting of this type and depth may occur on inherited normal faults which have subsequently been reactivated as thrusts. Such reactivation allows considerable shortening to take place in the early stages of continental collision without the subduction or excessive thickening of continental crust.