traumatic memory is any memory of any content which causes you anxiety, depression, nightmares .....

example

abuse of any kind can cause someone to have anxiety,depression, nightmares, flashbacks.
natural disasters can cause a person to have anxiety, depression, nightmares.
losing ones job may be something that causes someone to have anxiety, depression....
a death in the family may cause someone to have PTSD symptoms...
work stress could be traumatizing to someone.

what is traumatic for one person may not be traumatic for another...

example it was traumatic for me when I lost my home in hurricane sandy. but for my wife losing our home was not traumatic for her, she was just glad we were all safe and were able to procure other living arrangements.

another example it was traumatic for me to be a witness to a crime but for someone else i know witnessing this same crime was not traumatic to them.

each human being has their own coping tools and what causes them to have trauma symptoms. the symptoms do not come in any special order, one person may have anxiety first where as another may have flashbacks first its all individualized depending upon ones own brain and how they think, react, and what their own bodies feel is traumatic for them.