NDC-Type Tectonic Earthquakes in the Subduction Zones within Northwestern Segment of the Pacific Ring of Fire

Abstract—A systematic analysis of seismic moment tensors is conducted for earthquakes in the subduction zones of the Aleutian, Kuril-Kamchatka, and Japan island arcs. Earthquakes whose sources are not fit by the double-couple model (non-double-couple (NDC-type) earthquakes) are identified by estimating the angle between the slip vector and the rupture plane in the source based on seismic moment tensor eigenvalues. By analyzing error distribution of moment tensor component estimates, we revealed earthquakes with a significant NDC component in their source. Some features of the distribution of such earthquakes in the studied region are discussed. We compared the results of identifying sources containing a significant NDC component based on data from various seismological agencies. The comparison has shown that the catalogs of the U.S. Geological Survey (NEIC) and the Japan National Research Institute for Earth Science and Disaster Resilience (NIED) slightly underestimate the magnitude of the angle between the slip vector and the rupture plane compared to the Global Centroid Moment Catalog (GCMT). The applied method and the obtained estimates of NDC source slip component can be used in the numerical modeling of slip motion in the sources of strong earthquakes based on the combination of ground-based and satellite strain data.