how could this happen/have happened to me?

[Natalia]

Hi. Let's say that something bad happened to me in the past. Should I say:
1) How could this happen to me?
2) How could this have happened to me?

Can you comment on this, please?

[freknu]

Both are past, but I'd dare say the distinction is not so much in time as it is in aspect.

(1) could have happened in the distant or recent past, but is still ongoing or relevant to the present — imperfective.

E.g. you were in a car accident and were severely injured. At the hospital you are now faced with the torment of amputating your legs to save your life.

(2) happened in the past, but is no longer ongoing; often resultative — perfective.

E.g. you amputated your legs. The ordeal is over, but you are now faced with living without legs.

[Daniel]

Freknu's post is accurate. Additionally:

1) How could this happen to me?

This refers to a general situation. It might be in the past, but your question is not only about the past: you want to know why this might happen to you again or in general-- "Why me!?" you ask, referring to who you are as a person or what you do in general. (This would be a really weird question to ask if you just changed your life completely by getting a new job, moving to a new country and changing your lifestyle in general. It implies there is something consistent about you in the past and also now.)
Additionally, this does not NEED to refer to the past. It can, but only indirectly. It's general. (This is not a "present", but a habitual/general verb.)

2) How could this have happened to me?

This specifically happened in the past, and you want to know how. It's possible this is still relevant, but you are focusing on the one event (or maybe several) in the past specifically.

[Natalia]

Thank you, now I get it