The Nemuro-Oki (Nemuro Peninsula Offshore) earthquake (Japanese: 根室半島沖地震, Hepburn: Nemurohantō oki jishin) in scientific literature, occurred on June 17 at 12:55 local time.

It also triggered a tsunami with observed heights of nearly 3 meters hitting the coastal regions of Hokkaidō, causing damage.

[7] An average recurrence interval of 72.2 years spans between each large earthquake along this section of the subduction zone.

[4] A rectangular rupture patch is located between that of the 1952 Tokachi and 1969 Kuril Islands earthquakes were the source area of the 1973 event.

[13] Focal mechanism analysis revealed that this earthquake was the result of thrust faulting along the subduction plate boundary.

Waveform inversion on teleseismic seismographs showed that the earthquake ruptured upwards, to the trench, or in a south–southeast direction.

[7] Immediately after the earthquake, at 13:06 local time, the Sapporo District Meteorological Observatory broadcast a tsunami warning to residents along the Pacific coast of Hokkaidō.

Seven days after the mainshock, a magnitude (Ms ) 7.1 earthquake struck west of the Nemuro Peninsula at a depth of 50 km.