Imaging topographic growth by long-lived postseismic afterslip at Sefidabeh, east Iran
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This paper describes observations and models of the postseismic deformation following the 1994 Sefidabeh earthquake sequence in east Iran, which shed light on the nature of the earthquake cycle and the mechanisms of topographic growth in the region. Interferometric synthetic aperture radar observations show creeping fault motion (“postseismic afterslip”) on an array of faults. Some of these faults probably represent the extensions of those that ruptured in the blind thrust-faulting earthquakes in 1994, and cut through the entire seismogenic layer, while others are shallow and break up the hanging walls of the coseismic faults. The postseismic slip accommodates at least part of the vertical displacement gradient resulting from the buried coseismic slip, which was concentrated at depths of greater than ∼5 km. The postseismic afterslip is visible for over 16 years following the earthquakes. Agreement between the areas of postseismic uplift and indications of long-term motion preserved in the geomorphology suggest that shallow fault slip during seismic cycles similar to the one we have observed governs the development of the landscape in the region. Slip on an array of shallow faults provides a mechanism for the development of short-wavelength topography and geological structures above active thrust faults and has important implications for the interpretation of shallow geological features produced in regions experiencing similar seismic cycles to that at Sefidabeh.
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1944-9194
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Natural Environment Research Council (NE/K011014/1)