Earthquake at Underwater Hawaii Volcano Shakes Big Island

A sign is posted warning of earthquake damage to the road from seismic activity at the Kilauea volcano on Hawaii's Big Island on May 17, 2018 in Hawaii Volcanoes National Park, Hawaii. Mario Tama/Getty Images

HONOLULU—An earthquake at an active deep sea volcano off Hawaii shook the Big Island but didn’t appear to have any impact on other nearby volcanoes and no significant damage was reported.

The U.S. Geological Survey’s Hawaiian Volcano Observatory said the magnitude-4.0 quake Wednesday night was located under Loihi seamount, about 20 miles southwest of the Island of Hawaii, also known as the Big Island. It occurred at a depth of 7 miles.