REPORTING FROM JOHN WILKINS WITH THE SAN DIEGO UNION-TRIBUNE: 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 . What was that? The region joined a list of communities from coast-to-coast that are defined in part by unexplained goings-on. “Mysterious Shaking Rattles San Diego County AGAIN,” the website Strange Sounds trumpeted in a headline this week. And this! Thirty years ago, thousands of San Diegans were drawn to what some believed was the apparition of a slain girl on a blank billboard in Chula Vista. But unexplained loud, shaking noises are the most common, sometimes falling under the general term “skyquakes.” On the East Coast, enigmatic booms are known as “Seneca Guns,” the name drawn from a lake in upstate New York, the setting for a short story, “Lake Guns,” written in 1850 by James Fenimore Cooper. “It is a so...