Although there isn't currently a built-in way to handle this, there is a workaround that can be done using some jQuery in an Embed widget for the affected pages. 
  1. Log into your onMessage site

  2. Under Pages & Menus, click Edit Page Content for the affected page

  3. Add an Embed widget to your page. You may want to add it above your Events content type so you don't forget about it. 
    User-added image

  4. Click the settings cog and paste the following code: 

    <script>
    head.ready(function() {
    var d = $('.location');
    d.text(d.text().trim().replace(/(( - )\w+)$/i, ""));
    });
    </script>
    User-added image
  5. Save the Embed Settings and view your page to verify that it worked.
     

Before:

User-added image

After:

User-added image