OTTAWA — What if it had been worse? That was the question that Ottawa residents and emergency planners contemplated Thursday, one day after the most powerful earthquake in 65 years rattled the region and its one million residents.

City officials will review the events of Wednesday afternoon to understand how the emergency response could be improved in the event of a major quake.

“As with every incident, we’re always looking at opportunities to improve, because that’s the only way we’ll get better,” said John Ash, the city’s chief of integrated public safety.

This week’s “moderate” earthquake had a magnitude of 5.0.

But Ottawa sits in an active seismic zone that has twice experienced larger events during the past century. Earth scientists predict a major quake — a magnitude of 6.0 or more — will hit Ottawa once every 2,500 years.

Ash and other city officials said they were very pleased with the emergency response. “I think in this incident we did very well.”

The city’s emergency response began within seconds of City Hall’s being cleared following the 1:41 p.m. quake, said Ash, who convened a meeting of the emergency operations centre control group on the lawn outside the Lisgar Street entrance.

The control group includes city manager Kent Kirkpatrick, deputy city managers, chiefs of emergency services and department heads.

The group set out a plan to ensure emergency and city services continued, he said, even in the event of serious aftershocks.

Ottawa’s 911 system was overloaded for only about three to five minutes, Ash said, as non-emergency callers inquired about what was happening and what to do.

Mayor Larry O’Brien was not in the building when the quake occurred. He was to attend Telus executive and Ottawa philanthropist Janet Yale’s retirement party — he was even supposed to give her one of his trademark “coins” for her charitable work — but “that was not to be,” he said Thursday.

Instead, he returned to City Hall and was in the Office of Emergency Management within minutes.

City staff immediately inspected transit and traffic systems while trying to keep residents informed of the latest developments.

Ash’s team gave the media a technical briefing at about 4 p.m., followed by one to councillors at 4:30 p.m. Even in those 30 minutes, some details of what buildings were closed had changed.

“These are changing by the minute, as you can appreciate,” John Manconi, the city’s general manager of public works, said at the time. In the early hours, reports of what could and couldn’t stay open was “a moving target.”

Council seemed pleased by the teams’ early response, although Barrhaven Councillor Jan Harder noted that almost three hours after the earthquake, there was still no information on the city’s website. A weblink was up between 5 and 5:30 p.m. Before that, the city was tweeting information about their efforts. As well, the 311 infoline answered calls from the public.

Ultimately, there were reports of only minor damage to facilities and area residences. Most of the damage involved broken glass and cracked drywall and foundations. The most significant injury was a fractured leg.

Ash said 100 staff conducted inspections into the night Wednesday on city-owned buildings.

The Greenboro branch of the Ottawa Public Library, Goulbourn municipal building, Bernard-Grandmaître Arena and Barbara Ann Scott Arena all reported some damage, he said. The Barbara Ann Scott Arena and the Greenboro branch of the library remained closed Thursday, although the library branch was expected to reopen at 1 p.m. today. (The Pinecrest Recreation Centre, previously reported closed, is open.)

Meanwhile, Hydro Ottawa reported only brief power outages Wednesday caused by automatic shut-off mechanisms — the safety mechanisms sense tremors — which turned off 15 power transformers.

Spokesman Brian McGregor said hydro crews had to inspect the transformers before they could be restarted. All 16,395 customers affected by the outages had their power restored within 70 minutes of the quake.

The federal government did not activate its emergency plan, even though its own guidelines indicate it should be activated when an emergency “directly involves” federal employees and assets. Thousands of public servants were forced out of their buildings.

A spokeswoman for Public Safety Canada said the government determined that an emergency did not exist, so it did not initiate its plan.

“There was not any significant damage, and the government’s ability to function and deliver services was never threatened,” Sophie Bédard said.

She said the government did not receive a request for assistance from the City of Ottawa or the province. “Had the situation warranted a co-ordinated federal response, the Federal Emergency Response Plan would have been activated.”

John Gordon, national president of the Public Service Alliance of Canada, complained Thursday that many federal workers were left to decide on their own whether to go back to work. “I think there was confusion in some areas,” he said.

Some workers, Gordon said, were ordered to evacuate, even though they feared it would be more dangerous on the street. Others were unsure of what they were to do.

Gordon called for a thorough review of the government’s emergency communications and evacuation procedures before a more serious event. “It would be a good idea to sit down and review it now.”

Government officials said the decision to evacuate is supposed to be made by the senior official in each building.

Public Works announced Thursday all federal buildings have been inspected and deemed structurally sound. Bridges and dams in the earthquake zone were also inspected and cleared.

Much concern had been focused on the West Block, the oldest building on Parliament Hill, built between 1859 and 1906.

Robert Wright, executive director of major Crown projects for Public Works, said the building fared “quite well.” Building operators and engineers did a visual inspection, then structural engineers performed a detailed site analysis, he said. “There’s no damage: nothing that would have any impact on structural integrity.”

Data taken from seismic monitors on Parliament Hill will be assessed by the National Research Council. “That will give us some real evidence, some detailed information, on how the buildings performed,” Wright said.

Public Works has a 25-year plan to rehabilitate the aging stone buildings on Parliament Hill.

The $1.3-billion West Block project has already started with work on the southeast and north towers; more work begins this fall when the building is emptied.

The West Block long predates Canada’s first earthquake-resistant provisions, introduced to the National Building Code in the 1970s. The masons who built the West Block likely didn’t know they were working in an active seismic zone.

“I think we can take solace that the buildings performed well in the earthquake,” said Wright. “These buildings were built well originally and we’re taking all the necessary and proactive steps to ensure they’re upgraded to stand the test of time.”

When the West Block is fully rehabilitated, Wright said, it will be built to withstand an earthquake that delivers 10 times the force of Wednesday’s temblor.

With files from Joanne Chianello