htaccess redirect to parent page if not found with only knowing the begiing of path

I have paths like this:

mypage/blog/somestring1
mypage/blog/somestring2
mypage/blog/somestring3

I would like it if I go to mypage/blog/somestring1/page1 and it is not found it redirects back to: mypage/blog/somestring1. All I know is that the path begins with mypage/blog. The rest can be anything. Is it possible to create this 301 redirect if not found in .htaccess?