The observatory says the quake struck at 2:18 a.m. Saturday. It was centred about five miles (eight kilometres) north of the small town of Naalehu at a depth of six miles (9.6 kilometres).
There were no reports of damage or injury. People around the island reported light shaking. The observatory says light shaking isn’t expected to damage buildings.
Three aftershocks, magnitudes 1.6, 1.5, 1.4, were recorded at 3:30 a.m.
According to reports, the depth, location, and recorded seismic waves of the earthquake suggest a source on the large fault plane between the old ocean floor and overlying volcanic crust, a common source for earthquakes in this area, scientists said.