Was it an earthquake?

Was it a giant stomping on the roof?

Or did a truck ram into the building?

None of the above. But until the two loud booms just before 2 p.m. were explained, those were all logical explanations. A common sight Tuesday afternoon was to see others pouring from buildings, trying to figure out what happened.

The two rapid-fire explosions were really sonic booms from two military jets scrambled from Portland after a general-aviation airplane intruded into closed airspace soon to be traversed by President Obama, according to media reports.

The Cessna 150 involved in the intrusion landed near Lake Washington, according to Mike Fergus, a spokesman for the Renton-based regional office of the Federal Aviation Administration. He wouldn’t give an exact location.

The FAA issued a two-sentence statement on the incident and referred further questions to North American Aerospace Defense Command or NORAD. According to other reports, the two jets that were scrambled were F-15 Eagles, a twin-engine tactical fighter.

However, it has been reported the plane was a floatplane. Renton Municipal Airport serves floatplanes, but the airport tower reported the incident didn’t involve Renton airport airspace, which extends two miles out in all directions from the airport.

Obama was in Seattle for a campaign fundraising event for Sen. Patty Murray. He was to depart from Boeing Field.

A sonic boom is heard when a jet exceeds the speed of sound, setting off a noisy shock wave. But for those on the ground, the physics of a sonic boom didn’t really matter.

“It sounded like a giant stomped on the roof really hard,” said Daniel Goldman, who lives in southeast Renton.

In downtown Renton Uptown Glassworks owner Paul Sullivan was admiring the shop’s granite entryway created by R.D. Robinson, who happened to stop by. Robinson was in town for the 40th anniversary of Hazen High School’s first graduating glass. The granite comes from such faraway places as India and Argentina.

At about 1:50 p.m., the booms boomed and the ground moved.

Sullivan was reassuring. It was a truck, he said, pounding over the pavement.

Robinson wasn’t so sure, having spent more than three decades in Alaska, where he is an internationally known sculptor. He was standing in the doorway. The building moved laterally, a sign of an earthquake.

A sonic also boom was a possibility.

Calls flooded into newspapers and radio stations to report the explosions, which seemed most noticeable in the south Puget Sound area.

A few minutes later, Sullivan got a call on his cell phone about the earthquake. An earthquake is one thing that a glass-shop owner would fear.