Penny B
please do not give up.For detailed theory ,you need to read my blog.

http://earthquake-prediction.blogspot.com/

In anutshell ,it is momentum change ( accelaration or retardation of molten magma inside the crust).Though the direction change is apperant,it changes the nomentum suddenly creating imbalance in the internal crust . When maximum pull of Moon joins,it breaks the crust creating an earthquake or volcanic eruption.
regrads
Amit