Mongolians believed the world was help up by a giant frog. Each time the animal stumbled under its heavy burden, the ground shook in an earthquake. Similarly, another Hindu myth said the Earth rested on the backs of eight enormous elephants. The Greeks believed that Poseidon, god of the sea, banged the ocean floor with his trident when angry, creating earthquakes and tsunami.
An ancient Japanese legend says that earthquakes come from the writhings of a giant catfish. The gods usually control the fish by pinning it beneath a huge rock. However, the fish can get loose in October, when the gods are away.
Forces of Nature: ThinkQuest 2000 (Team #C003603)
http://library.thinkquest.org/C003603/english/earthquakes/legends.shtml
People of all ancient cultures had some type of explanation for the terrifying earth movements that jarred the world every once in a while. Most attributed it to the gods.