Traditionally personas have been created based on interviews, observations and other qualitative methods. Earlier on I have also used segmentation tools to start from. I have recently played a minor part in an interesting research project started by Jim Jansen and his team at Hamad Bin Khalifa University in Doha, Qatar. At HBKU the have created automated personas based on a large amount of data derived from social media.
You can read more about the Automated Personas Generation here: http://jimjansen.blogspot.dk/2017/04/dynamic-persona-generation.html