How should I deal with being harassed by my supervisor in a non-work situation? I'm a female student in some huge and popular university in my country.

I have a supervisor who is much older then me. He is a very respected person in our community.

We worked together a lot, it was fine. We communicated about personal issues as well, but nothing sex-related and/or inappropriate. No physical contact, hugs or even handshakes.

There was nothing special until the day we were celebrating something along with a lot of other teachers and students. I had drunk more then I should and stopped realizing what was happening. Then I found myself face to face with my supervisor and he started to harass me. I waited for a lucky moment and ran away.

Now we are ok with this and go on working together. This episode is ignored but not forgotten. I feel responsible for this but not guilty. I know that I'm not the first student he had close relationships with. And I know that he thought I would not mind it, so, now he is sorry. I know about two very alike situations with my friends in two other universities in my city.

Should I blame myself for this episode? I think that only for my careless and non-professional behaviour, not for the sexual issue.

Do you think I had to leave the university or communicate to the authorities or something?

How can you prevent yourself of having such a person as your supervisor? In my opinion, if he wasn't interested in me that way, I could drink even more and nothing would happen.
First, I would recommend that you put away any feelings of guilt and responsibility, and instead begin planning to protect yourself.  Unfortunately, it appears likely that your supervisor is a predator and abuser given several red flags in your story.  In particular:


Your supervisor waiting until you were impaired by alcohol before making unwanted sexual advances.  This is a massive red flag of abuse: safe and respectful people talk with prospective partners when they are sober.
Your supervisor appears to have sought an isolated environment in the midst of a group event where he could assault you and where you could run away without others noticing. 
Your supervisor appears to be manipulating your interpretation of his sexual assault on you: you say things like "we are OK with this" (taking a collective view) and "I know that he thought" (taking his view) and "he is sorry" (how did you feel?) that indicate that your view of the situation is being strongly influenced by his view.  To be blunt: it doesn't matter what he thought or felt; what matters is what you thought and felt when you were sexually assaulted.  Making you feel responsible for his feelings is an abuse tactic.
It sounds as though your supervisor engages in grooming for abuse, by picking certain "favorite" students and violating professional boundaries with them (talking about personal issues).  Some people just have minimal filter with everybody, but the picking favorites is a red flag: abusers often do this in order to identify people who will be good victims for their abuse, and then may wait quite patiently for an opportunity to switch into their preferred mode of abuse.
Your supervisor chose to make a sexual advance on their student, over whose life they have a huge amount of power and control, rather than waiting until you were no longer their student and could be more of a peer as a partner.


Now, it's possible that your supervisor is not a predator and abuser, but that's a lot of red flags, including an actual sexual assault.  Furthermore, most abusers do not believe that they are abusers, and can often be very persuasive to others, including the victims that they ensnare. 

So, what would I recommend that you do?  Unfortunately, the student/advisor power dynamics make this a tricky situation to navigate without doing harm to yourself and your career.  I would thus recommend that you start by protecting yourself and then find resources or otherwise get professional support to help decide how to proceed.


Never drink or otherwise impair yourself when you may encounter your supervisor, even if there are other people present.  He has isolated you for assault once, and may do it again. 
Find some good resources on abuse and familiarize yourself with their information and recommendations.  One site that I would recommend as helpful is: http://www.abuseandrelationships.org/.  Even though you are not in a sexual relationship with your advisor, a) your supervisor just attempted to start one, and b) you are in an important relationship due to the student/advisor connection.
If you can, begin consulting with a professional therapist or counselor with a good reputation for helping victims of assault and abuse.  Having a trustworthy and professional third party will be very valuable for helping you get a clear perspective on your situation and figuring out what is the right path for you, as well as helping deal with any emotional repercussions of your assault. 


Once you've taken all of those other steps, you will need to decide which of several paths you want to take, ranging anywhere from filing formal charges against your supervisor to quietly changing supervisors to simply protecting yourself and carrying through to graduation.  Unfortunately, all of the choices you make are likely to risk serious negative consequences to you, and only you (hopefully with aid from an experienced and supportive therapist or counselor) can decide which path and which risks are the best choice for your situation.