This scooping pattern of damage is commonly observed in unreinforced masonry buildings subjected to earthquakes. Figures 3.3 and 3.4 show a building damaged in the 1954 Fallon Stillwater earthquake in Nevada, with a scooping pattern similar to those noted in the Macellum. Damage in the 1954 Fallon Stillwater Nevada Earthquake. Note that the height of the wall varies, being taller in the front, resulting in deeper scooping there. A detail of figure 3.3.
Loads acting perpendicular to the face of the wall cause the wall to burst outward.
The line of failure tends to scoop upward toward the corners because the intersecting walls act as buttresses restraining the outward movement. Figures 3.5 and 3.6 show two more examples, one from the 1989 Loma Prieta earthquake in Santa Cruz, south of San Francisco, and another from the 1987 Whittier earthquake in southern California. The damage is partially visible in the upper left corner of the photo. Damage from the 1987 Whittier Earthquake. Note that the failure line extends down to the second floor level, and that the scooping pattern is interrupted by a window at the left end.