Many of the active faults in Utah are deep below the earth's surface, and are not visible to us. The San Andreas fault slips horizontally with little vertical movement. This is called a strike-slip fault . The Wasatch fault slips in a primarily vertical direction, with the mountains rising relative to the valley floor. The Wasatch fault is a so-called normal fault .
All earthquakes produce both vertical and horizontal ground shaking.
Usually the horizontal shaking is more energetic and more damaging because structures generally resist vertical loads, like gravity, more easily. Return to The Local Quake Threat . Return to General Quake Information .