 During a survey following the earthquake , evidence of coastal uplift was detected when dead and decomposing intertidal organisms were discovered along the beaches in the epicentral region . Further investigation revealed that a 15 km ( 9 @.@ 3 mi ) portion of the shoreline between Cape Mendocino and near Punta Gorda had been uplifted by as much as 1 m ( 3 ft 3 in ) near the middle portion , and decreasing amounts near the outer portions of the affected area . Evidence of previous events has been found in the form of sequential marine terraces along the coast , with periodic events creating shelves at 300 , 1 @,@ 700 , 3 @,@ 000 , and 5 @,@ 000 years before present . No surface ruptures were found during aerial surveillance , but lateral spreading features were observed on a channel near the mouth of the Eel River . 
