Earthquake - pinned beneath rubble

[Zebediah Magus]

I never actually used the spell, so I decided to give it some attention. It doesn't look impressive, since the Ref saves are fixed at DC 15 (not sure about tha DC 20 for open ground casting, though), but the part about being pinned beneath rubble wasn't very clear to me.

What are the actions one may take when pinned in such way? Does it work like being pinned in a grapple? How can one escape without help?

 

[Whimsical]

There's some rules for dealing with cave ins and colapses in the SRD that would work here.

Characters who aren’t buried can dig out their friends. In 1 minute, using only her hands, a character can clear rocks and debris equal to five times her heavy load limit. The amount of loose stone that fills a 5-foot-by-5-foot area weighs one ton (2,000 pounds). Armed with an appropriate tool, such as a pick, crowbar, or shovel, a digger can clear loose stone twice as quickly as by hand. You may allow a buried character to free himself with a DC 25 Strength check.