After having been subpoenaed to testify in court, how can I get this changed to a deposition?

In January of this year, I witnessed a motorcycle accident. I have now been subpoenaed by the city to testify in traffic court on May 24 on the East Coast of the U.S. However, I am moving to the West Coast on May 10, and I’m getting married there on May 25. I can’t be out East for the court date. What steps do I need to take in order to be permitted to give a deposition rather than appear in court? There are no attorneys listed on the subpoena.