You access a specific IGatherLog object by calling the IGatherLogs.Item property. Since IGatherLogs is a collection, you can access all IGatherLog objects using a for each loop, as in the following example, where objLog is the name you give to the IGatherLog object:
Option Explicit
On Error Resume Next
Dim objSearchAdmin, objBuildServer, objCatalogs, objCatalog, objLogs, objLog
Set objSearchAdmin = CreateObject("Search.SearchAdmin.1")
Set objBuildServer = objSearchAdmin.BuildServer
Set objCatalogs = objBuildServer.BuildCatalogs
Set objCatalog = objCatalogs("KMSampleCatalog1")
Set objLogs = objCatalog.objLogs
For Each objLog in objLogs
...
Next
'Release objects
Set objLog = Nothing
Set objLogs = Nothing
Set objCatalog = Nothing
Set objCatalogs = Nothing
Set objBuildServer = Nothing
Set objSearchAdmin = Nothing