[logback-user] Why would logback ever READ the log file it is writing to?

In our java application that uses logback, and running under Windows 7, the sysinternals process monitor (www.sysinternals.com) shows that the java process is READING the application's log file. Why would this be? I had thought that an appender would only append to the end of the log file and am surprised to see this, especially after I insisted it couldn't be true. Can someone explain why logback would need to READ a logfile? I can categorically say that none of the application's code reads the file. Steve Cohen