While PowerShell can be used, for very large datasets I commonly use SQL to parse and merge my events. Below is a simple example of how to convert your event files from the Windows Event format to SQL Server.
Download the Log Parser toolset from Microsoft:
Run the following Command (from a command line):
cd “c:\Program Files (x86)\Log Parser 2.2”
logparser “select * into MyTable from c:\MyEventFile\MyEventFile.evtx” -i:evt -o:SQL -createTable:ON -server:MYsqlServer -database:MyDB -username:MyUser -password:MyPassword! -driver:”SQL Server”