Google (GOOG) bought a big office complex in Mountain View, in its largest property purchase of 2011 in Silicon Valley, a deal that broadens the tech titan's remarkable expansion plans in the region.

Mountain View-based Google confirmed Thursday that it has bought The Landmark at Shoreline, a 240,000-square-foot office center. City officials say current zoning rules would allow Google to fill the complex with about 960 workers.

Google paid $100 million for the cluster of two-story office buildings on Landings Drive near Charleston Road just north of Highway 101. An affiliate of realty investment firm Broadreach Capital Partners completed the sale of The Landmark to Google on Oct. 18, county property records show.

"As we continue to hire, it's important to find space for our new employees," said David Radcliffe, a Google vice president of real estate and workplace services.

The Landmark is next to Google's primary headquarters.

"We look forward to incorporating it into our campus," Radcliffe said of its new acquisition.

Yet this is far from Google's sole purchase in the area.

During 2011 alone, the company has paid at least $225 million for at least 15 properties in Mountain View, according to public documents and realty agents. The purchases are primarily existing buildings.

"Google is like Pac-Man," said Jim Beeger, a senior vice president with realty brokerage Colliers International. "They are gobbling up everything in one corridor and then going up another corridor."

Much of Google's expansion activity initially centered on properties north of Highway 101. Then the company began buying some sites south of 101. These properties on the other side of the freeway, some miles from the headquarters, included low-slung research buildings on Terra Bella and a four-building complex a few blocks from Mountain View's downtown.

In August came a big leap for Google. For the first time, the company decided to move into Sunnyvale with the lease of a four-building project known as the Ariba Campus.

"I haven't seen anything quite like this in Silicon Valley," Beeger said. "Apple (AAPL) and Cisco (CSCO) have had some bursts of expansion. But they haven't taken this much space."

Mountain View officials say Google's growth has bolstered the city's economy.

"The Landmark deal not only solidifies Google's presence in Mountain View, but it also helps make Mountain View a center for innovation," said Ellis Berns, the city's economic development director. "Google is drawing in other companies and innovation startups."

Contact George Avalos at 925-977-8477. Follow him at twitter.com/george_avalos.