I would say encourage is used more commonly than spur. In fact, spur is most often used with the word on, as in to "spur someone on". Spur originated as something used to get a horse to move (which is still one of its meanings).

thank you, Daniel Y

"Spur" and "encourage" can be used similarly as they are both causatives, meaning the subject (agent) causes the object (patient) to perform an action. Depending on the context, they can be used interchangeably as "encourage" can be used as a euphemism for "spur".

Thank you, Priscilla (:

I think in this context, spurred would be the better choice as it is a thing, not a person, performing the action. What do you think, Andy? Your English is very good, Farhad. :)