The August 19, 2018 (M W = 8.2) Strong Deep Earthquake West off the Tonga Islands in the Context of Developing Our Concepts of Deep Earthquakes

Abstract—One of the strongest deep earthquakes that occurred on August 18, 2018, MW = 8.2, h = 600 km off the Tonga Islands is analyzed. This earthquake is notable for having a powerful aftershock sequence which is generally untypical of the deep earthquakes and which justifies considering this quake as a unique seismic event. Based on the first-day aftershocks, a three-dimensional (3D) geometric model of the source is constructed, and the seismic history and peculiarities of the aftershock process are studied. In particular, the duration of the aftershock process and the amount of the scalar seismic moment released by the aftershocks are estimated. It is shown that the source of the earthquake of August 18, 2018 pertains to the NDC type. Some characteristics of the earthquake of August 18, 2018 are compared with those of the strong deep ​​earthquake with MW = 8.3 that occurred in the Sea of Okhotsk on May 24, 2013 off the western coast of Kamchatka.