The concert originally was slated for Saturday, April 22, four days after the April 18 quake anniversary. But this week city officials conceded that there hasn't been enough money raised and that the concert is being postponed until later in the year.

"Financially it just was not working out for us on April 22," Matthew Goudeau, director of protocol in the Mayor's Office of Protocol, wrote in an e-mail to The Chronicle on Tuesday evening.

City officials estimate the concert could cost between $1.5 million and $2.5 million. The money to pay for the show and other anniversary events is being raised through private donations.

Santana, a Bay Area resident, was not going to charge for his time. There also was talk of getting other bands to participate, with Green Day among those rumored to perform.

"I know they've been raising money," said Jim Lazarus, vice president of the San Francisco Chamber of Commerce and one of the earthquake commemoration organizers who sits on a committee that is coordinating the events. "I know it hasn't been coming in as quickly as they thought it would."

Despite April 22 being initially selected as the date for the concert, the event itself and other plans for the centennial have not yet been officially announced.

Mayor Gavin Newsom said Wednesday night that the concert will take place later this year, though he would not specify when.

"It will be even bigger and better than what we had been planning,'' he told The Chronicle.

Newsom said companies sponsoring the commemoration events want to focus on earthquake preparedness around the anniversary of the quake and fire -- not on a concert at this time.

But, he added, he is confident that a sponsor or sponsors will come through later. He said a concert is an important part of the centennial: "We don't want to just lament the earthquake. We want to celebrate how far we've come and what more we can do.''

The other large-scale events planned include a three-day expo at Pier 48, sponsored by the San Francisco Fire Department Historical Society, set for the weekend before the anniversary and featuring historical exhibits on the quake and educational exhibits on disaster preparedness.

The annual wreath-laying ceremony at Lotta's Fountain, where many city residents convened after the 1906 quake and fire to post messages and learn about the fate of family members and friends, also will take place the morning of April 18. The handful of remaining quake survivors will be there to tell their stories, and the event is expected to draw thousands.

The Chronicle is in talks with city officials to be a financial sponsor for the concert and the Lotta's Fountain ceremony.

Why money could not be raised for a concert commemorating the most significant event in city history remains unclear.

Board of Supervisors President Aaron Peskin said he had been asked for help with the anniversary concert by officials with the city's Office of Protocol earlier this month.

"They came to my office on Feb. 3 to tell me about their plans and get my advice about fundraising," Peskin said Wednesday. "I gave them a whole lot of ideas, including names of companies that have had a long-standing relationship with the city, but I guess it was too little too late."

Rita Barela, who is producing the concert, said no future date has been set for the show.

"The whole theme of the mayor's commemoration is San Francisco rising. It's not just about the day San Francisco was almost destroyed," she said Wednesday. "It still can be later in the year."

Lazarus said the earthquake anniversary events commemorate the disaster and educate Bay Area residents on how to be prepared for another quake. But the concert is meant to celebrate the rebuilding of San Francisco.

"It was rebuilt in three years, and it was a massive undertaking," he said. "Those of us who had family here in those days are always proud that the city came back."

P.J. Johnston, who served as press secretary to former Mayor Willie Brown and now works as a private communications consultant handling public relations for the earthquake commemoration, said plans for the concert were always evolving.

"Mayor Newsom made clear he wants to have a yearlong commemoration of the anniversary," Johnston said. "There's lots of events throughout the year that aren't happening the week of the 18th, and this very well may be one of them."

E-mail Cecilia M. Vega at cvega@sfchronicle.com. Staff Writers Rachel gordon and Charlie Goodyear contributed to this report.

This article appeared on page B - 7 of the San Francisco Chronicle