EARTHQUAKE / THE LONG ROAD BACK : Temblor Is Reminder to O.C. of Its Own Fault : Seismology: It underlines Newport-Inglewood fissure’s potency.

According to Mark Johnson’s personal seismic meter--a stairwell chandelier that smashed against a window in his home during Monday’s violent earthquake--the 4:31 a.m. temblor was the strongest he has experienced in four years in Orange County.

For Johnson, manager of the Orange County Fire Department’s emergency management division, the quake served as a powerful reminder of the destructive potential of the Newport-Inglewood Fault line, which stretches under some of the most populous areas of Orange and Los Angeles counties.

The Northridge quake, which rumbled up from a previously unknown fault in the San Fernando Valley, causing 40 deaths and extensive damage, should underline to Orange County officials and residents that they, too, sit atop a potentially deadly geological crease, Johnson and others said Tuesday. The two faults are not connected.

“Anytime we have an earthquake, it is a reminder of the threat that we face here,” Johnson said. “But this one yesterday was a better lesson for us for several reasons--because of its proximity and the way it impacted people here, and because of the similarity here to the population density in the valley.”

Geologists have long warned that even a moderate shaker on the Newport-Inglewood Fault, which cuts a 40-mile subterranean path from Newport Beach through Long Beach and north to Beverly Hills, could result in a greater loss of life than a more serious quake along the better-known San Andreas Fault.

The Newport fault runs along the coastline, under more densely populated areas that sit atop sandy soil, which would prove unstable during a quake.

In a 1988 report, experts with the state division of mines and geology warned that a quake of magnitude 7.0 on the Newport-Inglewood Fault “poses one of the greatest hazards to lives and property in the nation.”

“Everyone talks about the Big One and the San Andreas, but we are far away from the San Andreas,” said Medhat Haroun, chairman of UCI’s Civil and Environmental Engineering Department. “We can get potentially more damage from a magnitude 7 earthquake on the Newport-Inglewood than a magnitude 8 on the San Andreas.”

The Newport-Inglewood Fault, the only major one in the county, is best known for causing the 1933 Long Beach earthquake, which killed more than 100 people and resulted in millions of dollars in damage.

Jim Davis, a geologist with the California Department of Conservation, the parent agency of the division of mines and geology, stressed that the Long Beach temblor, which measured 6.3 on the Richter scale, also was considered to be of moderate size.

In the aftermath of Monday’s quake, which caused comparatively little damage in Orange County, Johnson said the emergency management division already had begun to study the preliminary seismic data and damage estimates in order to glean any information that might be useful to the county’s emergency planning.

In terms of lessons for Orange County, the quake--delivered by a fault that runs under populous areas of the northwest San Fernando Valley--may provide a far more useful example than if it had occurred along the bigger San Andreas Fault, about 60 miles east of Los Angeles, Johnson said.

Times staff writer Jeff Brazil contributed to this report.

Deadly Fault Zone

The Newport-Inglewood Fault covers a relatively short distance, but is considered potentially deadly because it runs through a densely populated area.