New-LogSearchAlert -opResourceGroupName "MyOperationalInsightsResourceGroup" -actionResourceGroupName "MyResourceGroup" -ruleName "MyRule" -searchQuery "My azure activity search query" -workspaceName "MyOperationalInsightsWorkspaceName" -actionGroup "MyActionGroupName"
There are more optional parameters detailed in the Powershell script.
Remove-LogSearchAlert -opResourceGroupName "MyOperationalInsightsResourceGroup" -ruleName "MyRule"