The pilot reported that during the landing roll, the tailwheel-equipped airplane's left main gear began to shake violently and a pronounced wobble was observed with the left wheel. The airplane then began to swerve to the right. The pilot attempted to arrest the swerve to no avail. The left main landing gear subsequently collapsed, and the left wing sustained substantial damage. The pilot further reported that the winds were calm at the time of the accident. Post accident inspection of the landing gear did not determine if there was a mechanical failure or malfunction.