different log4j file for multiple threads

I need to create a different log4j file for each thread in a process. I want to read the configuration from one file and than change just the file name for each thread.

E.g. Process A  reads loads log4j properties file, the logfile name is processA.log

Process A now spawns 3 new threads, I want each thread to keep the same log4j confiiguation  (i.e. log level, file size etc.) and just change the names to processA_thread1.log, processA_thread2.log et.c

Thanks