We all have our faults, and that includes planet Earth. Earthquakes, big and small, rattle the globe every day, most recently making news this week with temblors in northern California.

The latest magnitude 6.9 earthquake struck 50 miles (80 kilometers) offshore of Eureka, California, on March 9, according to the U.S. Geological Survey.

The focus of the quake was about 10 miles (16 kilometers) underneath the Pacific Ocean, where a triangle of ocean and continental crust meets to form earthquake-prone faults.

All earthquakes spring from faults deep underground, but what kind? It can take scientists some time to answer that question for specific quakes.

The Earth's crust is made of a jigsaw puzzle of continental and oceanic plates that are constantly