GEOLOGY

Detailed explanation-1: -Volcanoes are associated with three types of tectonic structures: convergent plate boundaries, divergent plate boundaries and hot spots. California has all three. The SAF is a transform plate boundary (strike slip fault) and so is not accompanied by volcanic activity.

Detailed explanation-2: -Some, but not all, earthquakes are related to volcanoes. For example, most earthquakes are along the edges of tectonic plates. This is where most volcanoes are too. However, most earthquakes are caused by the interaction of the plates not the movement of magma.

Detailed explanation-3: -Sometimes, yes. A few large regional earthquakes (greater than magnitude 6) are considered to be related to a subsequent eruption or to some type of unrest at a nearby volcano. However, volcanoes can only be triggered into eruption by nearby tectonic earthquakes if they are already poised to erupt.