I don't think it's typical in the sense that the blended learning approach is very new for most unis! It might be something to raise with your personal tutor/the timetabling team/the lecturers for each to see if one or the other can be rescheduled. Otherwise I guess you would presumably go to campus for the in-person seminar, then probably need to "attend" your online seminar while still on campus, unless you live just a couple of minutes away.