The Structure of the Kantishna Seismic Cluster, Central Alaska, Derived From Stress Tensor Inversions and Seismicity Trends

The Kantishna Cluster is an enigmatic and energetic cluster of earthquakes located in central Alaska, just to the northwest of Mt. McKinley/Denali and north of the Denali Fault. The Kantishna Cluster is located at a hub of tectonic activity including Bering Block rotation to the west, bookshelf faulting to the northeast, and rotation of southern Alaska due to Pacific plate convergence to the south. The Alaska Earthquake Information Center (AEIC) earthquake catalog locations show the cluster as an S-shaped cloud of earthquakes with no discernable structure. Double difference hypocentral relocations show that the cloud of earthquakes collapses into several distinct trends. Stress tensor inversions of events within the cluster show that the stress orientations vary systematically throughout the cluster. From stress tensor inversions, predominant faulting features can be determined for each trend in the cluster. Combining seismicity trends resolved from hypocentral relocations and faulting features determined from stress tensor inversions, it became possible to infer fault planes or planar structures in the region. The newly uncovered structures and a rotation of the maximum compressive stress throughout the cluster suggest that the Kantishna Cluster exists to accommodate interactions between all the tectonic structures surrounding the cluster.