one thing you do when you Thinking is Headache. Explanation is a type of Thinking. Explanation is related to Explain. Explain is related to Brief. 
Awful is a synonym of Tremendous. Tremendous is related to Grief. 
Headache <--HasSubevent-- Thinking <--IsA-- Explanation <--RelatedTo--> Explain <--RelatedTo--> Brief 
Awful <--Synonym--> Tremendous <--RelatedTo--> Grief 