A local geologist says Friday's earthquake in Old Greenwich was not uncommon and will likely happen again. According to Skipp Hobbs, former president of the Geological Society of America, the 2.1-magnitude quake was caused by minor fault action below the surface. He says the region is full of fault lines, with some dating back as far as 500 million years. Many residents say they felt a loud rumble as if a truck had driven by their homes. Officials: 2.1-magnitude earthquake hit Greenwich