In order to understand this view of the October 17, 1989, Loma Prieta earthquake, imagine that you are underground looking toward the NW. The trace of the San Andreas fault on Earth's surface runs directly away from you over your head (light blue line). You can also see the Pacific coast of California (green line) near the city of Santa Cruz. Notice that the earthquakes do not fall on a vertical line as might be expected on a simple strike-slip fault. This is due to the fact that the San Andreas fault has a slight bend here and the Pacific Plate is riding up and over the North American plate, creating the Santa Cruz Mountains.
