In order to get duplicate messages for Measurement Threshold policy you need to configure Continue Action.
Continue actions are carried out at each polling interval if the start action of the rule was carried out at a previous polling interval, and the reset value is not reached.
Open one Measurement Threshold policy > move to Rules tab > Select a rule for which you would like to get a duplicate message > click Modify button on the right hand side > new dialog window opens up ,move to Actions tab > Select again a rule for which you want to get duplicate message and click Modify button > new dialog window opens up ,move to Continue Actions tab > check “ Use the specified ‘Start Action’ ” >Save and redeploy the policy.
This way you will get a duplicate messages on each polling interval until the reset value is reached.
For more detailed information you may want also to take a look at OMW Online Help: