Find out Who has Deleted a Site Collection in SharePoint

#Import necessary Modules
Import-Module WebAdministration
Add-PSSnapin Microsoft.SharePoint.PowerShell -ErrorAction SilentlyContinue

#Function to get Log Folder of the SharePoint Web Application
Function Get-IISLogFolder($WebAppURL)
{
    #Get Web Applications' IIS Settings
    $WebApp = Get-SPWebApplication $WebAppURL
    $IISSettings = $WebApp.IISSettings[[Microsoft.SharePoint.Administration.SPUrlZone]::Default]
    $WebSiteName = $IISSettings.ServerComment

    #Get Log Folder from Web Site
    $WebSite = Get-Website -Name $WebSiteName
    $LogLocation = "$($WebSite.LogFile.Directory)\w3svc$($WebSite.id)".Replace("%SystemDrive%",$Env:SystemDrive)
    Return $LogLocation
}

#Function to Parse IIS Log
Function Parse-IISLog {

 [CmdletBinding()]
    [OutputType([System.Data.DataTable])]
 param(
  [Parameter(Mandatory=$True, ValueFromPipeline=$True)][string[]]$LogFilePath
        )
 BEGIN {
        $LogDataTable = New-Object System.Data.DataTable
        $FieldsString = Get-Content -Path $LogFilePath | Select -First 5 | Where {$_ -Like "#[F]*"}
        $Fields = $FieldsString.substring(9).split(' ');
        $FieldsCount = $Fields.count - 1
    }
 PROCESS {
        for($i=0;$i -lt $FieldsCount;$i++) {
            $LogDataTable.Columns.Add($Fields[$i]) | Out-Null   
        }
        $Content = Get-Content -Path $LogFilePath | Where {$_ -notLike "#[D,S,V,F]*" } | ForEach-Object {
            $Row = $LogDataTable.NewRow()
            for($i=0;$i -lt $FieldsCount;$i++) {
                $Row[$i] = $_.Split(' ')[$i]
            }
            $LogDataTable.Rows.Add($row)
        }
    }
    END {
        $PSCmdlet.WriteObject($LogDataTable)
    }
}

#Function to search IIS Logs for a given URL in given web application
Function Search-IISLogs($WebAppURL, [String]$SearchURL)
{
    #Get IIS Log Folder
    $IISLogFolder = Get-IISLogFolder $WebAppURL

    #Get IIS Log files created in the past 30 days
    $IISLogFiles = Get-ChildItem -Path $IISLogFolder -Recurse | Where {$_.CreationTime  -Gt (Get-Date).AddDays(-30)}

    ForEach($LogFile in $IISLogFiles)
    {
        Write-host "Processing Log File:"$LogFile.FullName -f Yellow
        $IISLogData = Parse-IISLog $LogFile.FullName

        #Search Data
        $SearchResults = New-Object System.Data.DataView($IISLogData)
        $SearchResults.RowFilter = "[cs-uri-stem] like '%$SearchURL%'"

        #Result
        If ($SearchResults.Count -gt 0) 
        {
            Write-Host "`tFound Site Deletion!" -ForegroundColor Green
            $SearchResults | Select date, time, cs-uri-stem, cs-username, "cs(Referer)" | Format-Table
        } 
        Else 
        {
            Write-Host "`tNo Site Deletions Found!" -ForegroundColor DarkYellow
        }
    }
}

#Parameters
$WebAppURL="http://intranet.crescent.com"

#Call the function to search site deletions
Search-IISLogs $WebAppURL "/_layouts/15/webdeleted.aspx"

#Call the function to search deleted sites from Central Admin
$CentralAdminURL =  Get-SPWebApplication -IncludeCentralAdministration | Where {$_.IsAdministrationWebApplication} | Select -ExpandProperty URL
Search-IISLogs $CentralAdminURL "/_admin/delsite.aspx"