We faced a similar issue and emailed Disqus about this. They confirmed that by default they only support one Disqus module per page.
When browsing the Disqus JS documentation, I did find a solution that might work for you by loading and unloading the Disqus modules as the user interacts with the site:
DISQUS.reset({
reload: true,
config: function () {
this.page.identifier = "newidentifier";
this.page.url = "http://example.com/#!newthread";
}
});
http://docs.disqus.com/help/85/
The exact implementation would depend upon your site, but this should give you a building block to start from. For example, if the event information becomes available by expanding a content area, you could load the Disqus module whenever someone expands the event content.