What part of the united states is most likely to experience earthquakes and volcanoes (tectonic activity)?

The west coast as it is located along the transform boundary between the North American and Pacific plates

Geothermic gradient is the rate of increasing temperature with respect to increasing the depth in the earths interior. away from tech tonic plates boundaries, it is about 25-40 c/km (72-87 degrees f/mi) of depth near the surface in most of the world.