Answer for this SO-post says event hub REST end points can be used to initiate the fail over, but I don't find any Microsoft docs about event hub REST end points. Could you please share how to do it?
First, read this doc Azure Event Hubs - Geo-disaster recovery for the concept if you need it.
For rest api, please refer to this official doc: Disaster Recovery Configs.
For java, you can refer to this sample in github: eventhub-java-manage-event-hub-geo-disaster-recovery.
For .net, you can refer to this sample in github: Microsoft Azure Event Hubs Geo-DR.