location of table in database with admin log and password change history

Is there a table in the wordpress database for my blog that contains a log of admin changes? I’d also like to know where the user password table is and if it contains a history of the date and time passwords were changed. I know that for privacy reasons the passwords should be encrypted in the database and I’m not looking to see the passwords. I’m just wondering if I can check to see if a user was hacked by looking at a history of their password date/time changes.

I’m using phpMyAdmin and only see the wp_users and wp_usermeta tables. I’m assuming the password table is hidden and am wondering how I’d access it.

Thanks for any help you can provide.