Hello Petra,

That 3.6 is where a set of strong quakes hit in 1956 in the Jaurez Mountains near San Miguel. That's 50 years, but I do not have any data on recurrence for that region. I did find this little nugget about it though.

http://www.seismo-watch.com/EQSERVICES/NotableEQ/Feb/0209.SanMiguel.html

glen