document: A major earthquake registering 7.2 on the Richter scale shook the Solomon Islands in the South Pacific today , the U.S. Geological Survey says . The preliminary reading of 7.2 is slightly stronger than the 7.1 magnitude earthquake that hit the San Francisco Bay area Oct. 17 . The earthquake struck the islands at 8:05 a.m. today , or 5:05 p.m. EDT Friday , said USGS spokesman Don Finley . It was the largest earthquake in the Solomons since a 7.4 quake on Nov. 5 , 1978 . There were no immediate reports of injury or damage . Major earthquakes in the Solomons usually do n't cause much damage or many casualties because the area is sparsely populated and not extensively developed . The Pacific Tsunami Warning Center in Honolulu said no Pacific-wide tsunami _ popularly called a tidal wave _ was generated by the quake , but some areas might see small changes in sea levels . Saturday 's earthquake was the strongest in the world in five months , Finley said . An 8.3 quake hit the Macquarie Islands south of Australia on May 23 . The survey 's earthquake monitors in Golden , Colo. , said early seismograph readings placed the epicenter of Saturday 's earthquake about 200 miles southeast of Honiaria , which is on Guadacanal Island and is the capital of the Solomons . That places the earthquake just east of San Cristobal , the easternmost island in the Solomons chain and about 1,300 miles northeast of Brisbane , Australia . The Richter scale is a measure of ground motion as recorded on seismographs . Every increase of one number means a tenfold increase in magnitude . Thus a reading of 7.5 reflects an earthquake 10 times stronger than one of 6.5 . An earthquake of 3.5 on the Richter scale can cause slight damage in the local area , 4 moderate damage , 5 considerable damage , 6 severe damage . A 7 reading is a `` major '' earthquake , capable of widespread heavy damage ; 8 is a `` great '' quake , capable of tremendous damage .
extractive_keyphrases: richter scale solomon islands major earthquakes epicenter widespread heavy damage largest earthquake earthquake monitors