The 6.0 magnitude quake was located on a fault line underneath the Pacific Ocean, 173 miles (279 kilometers) from the city of Bandon in the state of Oregon, the US Geological Survey said.

There were no immediate reports of any damage, and computer modeling by the USGS showed "there are likely to be no affected structures in this region."

Seismologists put the depth of the quake initially at 10 kilometers, a default setting for shallow earthquakes that is frequently revised as more data becomes available.

There are a number of fault lines running along, through and near the US West Coast, which form part of a larger network around the world's biggest ocean known as the Pacific Ring of Fire.