Powershell to remove all alerts for a user in a Web Application

This script will delete all alerts for a specific user on a Web App.  It's useful when a user is deleted, but the MySite cleanup job did not remove their collection level alerts.

Credit on this one to:  http://www.sharepointdiary.com/2011/11/managing-alerts-using-powershell.html - Salaudeen Rajack. 
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##### Remove all alerts for specific user from a Web Application #####
$SPwebApp = Get-SPWebApplication "http://somesharepointsite.com"
$SpecificUser = "AD\someuser"
foreach ($SPsite in $SPwebApp.Sites)
{ # get the collection of webs
foreach($SPweb in $SPsite.AllWebs)
{ $alerts = $SPweb.Alerts
# if 1 or more alerts for a particular user, Make a note of them by copying their ID to an Array
if ($alerts.Count -gt 0)
{ $myalerts = @()
foreach ($alert in $alerts)
{ if ($alert.User -like $SpecificUser)
{ $myalerts += $alert
}
} ### now we have alerts for this site, we can delete them
foreach ($alertdel in $myalerts)
{ $alerts.Delete($alertdel.ID)
write-host $alertdel.ID
}
}
}
}