 The earthquake was 6 @.@ 4 on the moment magnitude scale , with a maximum perceived intensity of IX ( Violent ) on the Mercalli intensity scale . However , most of the intensity measurements were consistent with an overall maximum intensity of VII ( Very strong ) , and only the damage to a single structure , the Imperial County Services building in El Centro , was judged to be of intensity IX . Several comprehensive studies on the total structural failure of this building were conducted with a focus on how the building responded to the earthquake 's vibration . It was one of the first heavily instrumented office buildings to be severely damaged by seismic forces . 
