While the Internet Archive provides preservation copies and vintage broadcasts, official high-definition versions are available through various services:
The Internet Archive is a treasure trove for Tremors fans looking for not just the movie, but rare behind-the-scenes materials, alternate cuts, and preservation projects. However, because of copyright enforcement, full movie availability is inconsistent. The Archive is best used for discovering historical artifacts (trailers, TV spots, making-of docs) and fan restorations that supplement an official copy of the film.
The archive hosts various "making-of" materials and deep dives into the franchise's evolution. Tremors: Blast from the Past - A Different Direction