$dbUser = "tester"
$dbPass = "myP@ssword"
$primaryServerName = "serverName"
$primaryDbName = "dbName"
$resourceGroupName = "groupName"
$secondaryServerName = "secondary" + (Get-Random)

$existingDb = Get-AzureRmSqlDatabase -ServerName $primaryServerName -DatabaseName $primaryDbName `
    -ResourceGroupName $resourceGroupName

# Create secondary server
$securePass = ConvertTo-SecureString -String $dbPass -AsPlainText -Force
$dbCredentials = New-Object -TypeName "System.Management.Automation.PSCredential" -ArgumentList $dbUser, $securePass
$serverSecondary = New-AzureRmSqlServer -ServerName $secondaryServerName `
    -ResourceGroupName $existingDb.ResourceGroupName -Location "West Europe" `
    -SqlAdministratorCredentials $dbCredentials

# Activate geo-replication
$existingDb | New-AzureRmSqlDatabaseSecondary `
    -PartnerServerName $secondaryServerName `
    -PartnerResourceGroupName $existingDb.ResourceGroupName
    # To allow connections to your secondary DB just add -AllowConnections All