TY  - JOUR
A1  - Donner, Stefanie
A1  - Ghods, Abdolreza
A1  - Krüer, Frank
A1  - Rößler, Dirk
A1  - Landgraf, Angela
A1  - Ballato, Paolo
T1  - The Ahar-Varzeghan Earthquake Doublet (M-w 6.4 and 6.2) of 11 August 2012: Regional Seismic Moment Tensors
JF  - Bulletin of the Seismological Society of America
N2  - On 11 August 2012 an earthquake doublet (M-w 6.4 and 6.2) occurred near the city of Ahar, northwest Iran. Both events were only 6 km and 11 minutes apart, producing a surface rupture of about 12 km in length. Historical and modern seismicity has so far been sparse in this area. Spatially, the region represents a transitional zone between different tectonic domains, including compression in Iran, westward extrusion of the Anatolian plate, and thrusting beneath the Caucasus.
 In this study, we inverted the surface waveforms of the two mainshocks and 11 aftershocks (M-w >= 4.3) to obtain regional seismic moment tensors. The earthquakes analyzed can be grouped into pure strike slip (including the first mainshock) and oblique reverse mechanisms (including the second mainshock). The sequence provides information about faulting mechanisms at the spatial scale of the entire rock volume affected by the earthquake doublet, including coinciding deformation on minor faults (sub) parallel to the main fault and Riedel shears. It occurred on a so far unknown fault structure, which we call the Ahar fault.
 Alongside the seismological data, we used geological maps, satellite images, and digital elevation data to analyze the geomorphology of the region. Our analysis suggests that the adjacent North Tabriz fault, which accomodates up to 7 mm/yr of right-lateral strike-slip faulting, does not compensate the entire lateral shear strain, and that part of it is compensated farther north. Combined, our results suggest a temporally and spatially complex style of deformation (reverse and strike slip) overprinting older reverse deformation.
Y1  - 2015
U6  - https://doi.org/10.1785/0120140042
SN  - 0037-1106
SN  - 1943-3573
VL  - 105
IS  - 2A
SP  - 791
EP  - 807
PB  - Seismological Society of America
CY  - Albany
ER  -