Log files created as part of an upgrade will have "update" in their name such as these:
logapp_x.x.x_update_err.log (where x.x.x is the version number for the LMI, e.g. logapp_5.7.0_update_err.log)
logapp_x.x.x_update.log

The main update.log above provides the log activity for all the different parts of the LMI upgrade process but a secondary log contains specific information for the task involved in installing upgraded RPMs. That activity is stored in:
upgrade_log_<datetime stamp> (e.g. upgrade_log_201702011551)

Log files created as part of a new installation will instead contain "install" in their name such as these:
logapp_x.x.x_install_err.log (where x.x.x is the version number for the LMI, e.g. logapp_6.1.1_install_err.log)
logapp_x.x.x_install.log

A new installation will not have any of the upgrade-related log files until the new installation has been upgraded to a future version.