Santa Clara, Calif. ? Dennis Erickson was hired Tuesday by the San Francisco 49ers to replace Steve Mariucci as coach in a surprising end to a search that stretched nearly four weeks.

Erickson will be introduced as the 49ers’ 14th head coach at a news conference in San Francisco today. The former Seattle Seahawks coach leaves Oregon State, where he went 31-17 over the last four seasons.

Mariucci, fired by owner John York on Jan. 15 despite leading San Francisco to four playoff berths in six seasons, signed a five-year contract with the Detroit Lions last week.

Erickson, who turns 56 next month, is an unexpected choice for San Francisco, which concentrated its search on NFL defensive coaches since York surprised his front office by firing Mariucci.

After wowing York and general manager Terry Donahue in a weekend interview, Erickson received a five-year contract worth $12.5 million — half of what Mariucci will make in Detroit. Erickson is charged with continuing the winning tradition established by Bill Walsh, George Seifert and Mariucci.

“We have found what we were looking for in a new coach: a leader, a motivator, a teacher, an individual with exceptional skills in coaching,” Donahue said. “Dennis Erickson has a long history of coaching winning teams, and I’m confident he’ll succeed in San Francisco.”