Four moderate earthquakes rattled the sea floor about 200 miles due west of Winchester Bay on Saturday morning, according to the U.S. Geological Survey.

The first 5.2-magnitude quake struck at 1:11 a.m., followed by a 4.4 quake at 1:24 a.m. and a 4.8 quake at 4:06 a.m. The final quake Saturday shook the sea floor at 8:08 a.m. All were about 6 miles beneath the earth's surface, which is typical for temblors off the South Coast.

Geologists have said this is an extremely active fault area known as the Blanco Fracture Zone. Typically, hundreds of quakes strike along the zone every year, but most are so small no one notices.

The quakes haven't produced tsunamis, since they are caused by the Juan de Fuca plate sliding under the North American plate without changing the shape of the ocean floor, according to the Pacific Northwest Seismic Network.