Where are crash logs after a system freeze?
Apple moves the logs from version to version, but I would start with sysdiagnose.

Open the terminal app and type sysdiagnose or press the keys to trigger the data collection process.


How do you get system diagnostic files from OS X?


The good thing about this is it collects both the traditional log file based logs, snapshots like recent crashes, panics, hangs as well as a recent sample stored in a potable log archive format of the system log database files (since 10.9 more and more logs are stored in the apple system logs database as opposed to flat files and panic logs).

From there, you can open the file and search for the panics and crashes.