The only magnitude 8.0 or greater earthquake in July-December 1986 happened near the Tonga-Kermadec oceanic trench has the following parameters listed in the NEIC PDE: origin time 1986/10/20 06:46, latitude 28.12S, longitude 176.37W, depth 29 km, and M=8.3, F-E Region: 177 - KERMADEC ISLANDS REGION.
Kermadec 1986 Kermadec 1986 Kermadec 1986