A series of earthquakes hit off the Oregon coast in northwest United States from Sunday through Monday, apparently causing no harm to life and property.

The US Geological Survey (USGS) said the latest quake, measured at magnitude 6.0, struck at 1:12 pm Monday in the Pacific Ocean about 480 kilometers west of Newport, and another temblor at magnitude 5.8 was near the same location shortly before midnight.

In media reports reaching here, Max Rudolph, a geologist at Portland State University, was quoted as saying that the quakes occurred near the boundary between the Juan de Fuca plate and the Pacific plate as part of "a natural ongoing movement between these two tectonic plates."

No tsunamis were triggered and no damage has been reported to local authorities.

The USGS also said there was a magnitude-4.3 quake about 1:40 am Monday, a magnitude-5.5 quake about 3:45 am Monday and 4.4 quake about 7:45 am Monday in the same area.

Besides that they were nearly 10 kilometers deep, Rudolph said he was "not concerned" about these events because they were far off shore.