The pilot of the tailwheel equipped airplane reported that, after a wheel landing, the tail wheel touched down on the ground and started a "violent shaking." He pushed forward on the control yoke to raise the tail, increase throttle and subsequently let the tail touched down on the runway again. The tailwheel continued to shake, and the airplane began to veer left but the pilot corrected with opposite rudder. Shortly after the airplane regained runway heading, the airplane veered right, exited the runway to the right and ground looped. The airplane sustained substantial damage to the left wing. The pilot reported that there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation. The pilot added that, during landing, the wind was from 010º at 4 knots. The automated weather observation station located on the airport reported that, about the 15 minutes before the accident, the wind was from 160° at 4 knots. The airplane landed on runway 03. The pilot did not submit the National Transportation Safety Board Pilot/Operator Aircraft Accident/Incident Report Form 6120.1.