Another mystery boom leaves San Diego grasping for answers John Wilkens, The San Diego Union-Tribune March 14, 2021 FacebookTwitterEmail A girl plays along the border wall, right, separating San Diego from Tijuana, Mexico, where it meets the Pacific Ocean, Tuesday, June 11, 2019, in Tijuana.Gregory Bull/Associated Press SAN DIEGO — Everybody loves a mystery. But we like them solved, too, and so far an answer has been elusive for the Big Border Boom. It rattled windows and shook doors across a large swath of San Diego and Tijuana late Wednesday afternoon, jangling the nerves of residents who’d experienced a similar noisemaker last month, and one a year earlier.