The warnings came in on cell phones, social media and from news outlets: a tsunami was on the way.

While the advisory may have caused brief concern for some Southern California residents, the waves were less than impressive.

But what if a serious tsunami were to threaten the Orange County coast and the 125,000 people who could be at risk?

The tsunami following 8.3 earthquake struck off Chile on Wednesday didn’t turn out to be a cause for concern, but detailed preparations are in place to protect residents from serious tidal surges, officials say.

“We are thankful nothing more significant happened from the tsunami advisory, but we are glad to have been able to execute our plan,” Vicki Osborn, assistant emergency manager for Orange County, said Thursday.

The National Weather Service projected tsunami waves would arrive at Newport Beach at 4:46 a.m. Thursday and would be less than 1 foot above the usual tide.

Even with such a minor impact expected, the Orange County Emergency Operations Center mobilized as soon as it got the word Wednesday night.

As part of its tsunami protocol, the Emergency Operations Center conducted a conference call around 7:30 p.m. Wednesday with officials in coastal cities to make preparations, Osborn said.

“When we have events, we have coordinated conference calls with all the jurisdictions to make sure we support each other,” she said.

That could include a joint decision by jurisdictions to close or evacuate beaches.

“We try to act as unified effort,” said Brevyn Mettler, emergency services coordinator for Huntington Beach. “If one city is closing their beaches, we all close our beaches.”

Officials decided to close all Orange County beaches, harbors and marinas at 4 a.m. Thursday because of dangerous currents, said Jeff Hallock of the Orange County Sheriff’s Department. Dana Point Harbor closed at 2 a.m.

No evacuations were ordered and officials reopened local beaches, marinas and piers at 6 a.m., Hallock said.

Scenarios in protecting the public vary depending on the seriousness of the tsunami threat, Osborn said.

A tsunami watch means the danger level is not yet known and that individuals should stay alert for more information, according to the National Weather Service.

An advisory means strong currents are likely and that individuals should stay away from the shore, while a warning means an inundating wave is possible and evacuation is suggested.

The Emergency Operations Center has a system in place to disseminate information through Alert OC, which notifies residents of emergencies by cell phone, emails and home phones if they have signed up for the service at www.AlertOC.com.

Alerts are also issued through social media such as Twitter and advisories sent to the media, Osborn said.

The cities of San Clemente, Dana Point, Newport Beach and Huntington Beach also have siren systems alerting residents to seek higher ground during a tsunami warning, she added.

In addition, Orange County coastal cities have street signs and maps on their websites detailing evacuation routes from tsunami inundation areas, Osborn said.

The size of inundation zones vary in Orange County depending on topography.

For example, Huntington Beach has a large zone because it is flat and densely populated, while Dana Point’s zone is smaller because it has a more cliffs fewer residences, Osborn said.

About 70,000 residents, not including tourists, would have to leave Huntington Beach during a full-scale evacuation, Mettler said.

A total evacuation of the Orange County coast could include about 125,000 people, Osborn said.

If a full-scale evacuation were in ordered in Seal Beach, police and volunteers would go door-to-door to alert residents, said Seal Beach police Sgt. Philip L. Gonshak. Those evacuated would be housed in emergency shelters inland such as community shelter, schools and other facilities, Osborn said.

Orange County would have several hours to evacuate coastal areas for major earthquakes originating in quake-prone areas such as Chile, Alaska and Japan, but about 15 to 20 minutes for a local quake such as one near Catalina Island, she said.

As part of its preparations, the Emergency Preparedness Center monitors earthquakes around the clock and fine tunes its tsunami plan with a table-top exercise each March during Tsunami Awareness Month.

“Our ongoing relationships with jurisdictions and the community will help us be better prepared for a future event,” she said.