Within Seam an Interceptor is not a Seam Component. It is a class that can intercept invocations on Seam Components.
You may want to read 5.2. Seam interceptors to get a better understanding of how to write and apply interceptors to Seam components.
There has been some time since the question has been asked but bumping this same need lead me to this question, and probably others as well.
What I finally did is defining a class member of type org.jboss.seam.log.Log initialized by Logger.getLog(Class) method, as appears below:
private Log log = Logging.getLog(ActivityTrackingInterceptor.class);
This gives you an valid instance you can use