This can be done by logging into the app admin, clicking on the "settings" tab, then the "display settings" sub-tab, and then scrolling down to the "Page Header HTML" input box, and then inputting the following code:
<script>
$( document ).ready(function() {
$('#address_search').val('!!!!');
setTimeout(
function()
{
$('.search_bar button').click();
}, 1000);
});
</script>
Replace !!!! with the search terms that you want to be the default search upon page load.
