The January 23, 2018 M7.9 earthquake ruptured conjugate set of strike-slip faults in the outer rise of the Alaska subduction zone, southeast of Kodiak Island. The complex nature of this earthquake is evident from the earthquake focal mechanism and aftershock relocation patterns, which revealed rupture of multiple north-south and east-west trending conjugate fault planes. Here, we suggest that this earthquake occurred as a result of two different modes of interaction process. The stress triggering process reveals (i) the co-seismic and post-seismic deformation of the M9.2 1964 Alaska megathrust earthquake increased Coulomb failure stress of ∼10 kPa and
∼0.05 kPa respectively in the 2018 Kodiak earthquake source region, and (ii) the overall deformation is being accommodated in the outer rise region due to slip partitioning resulting from the oblique convergence between the Pacific and North American plates along the Alaska Aleutian megathrust.
Figure Caption: Models for southern Alaska tectonics and block deformation. Top left: Rotation model, Top right: Extrusion model, Bottom left: Oblique convergence model, Bottom right: Model depicting slip partitioning in the outer trench of the Alaska-Aleutian subduction zone.
The M7.9, 2018 Kodiak earthquake is interpreted to be the result of unusual slip-partitioning in the outer rise region.
Bhaskar Kundua, Rajeev Kumar Yadav, Vineet K. Gahalaut, Dibyashakti Panda; 2020, The January 23, 2018 M7.9 Kodiak earthquake, Alaska: A consequence of slip partitioning in the outer rise region; Journal of Geodynamics; 137, 101732, https://doi.org/10.1016/j.jog.2020.101732