Imperial Valley, California, Earthquake October 15, 1979. Rupture (or "mole track") on the Imperial Fault in a field south of Heber Road (2.4 kilometers northwest of the southeast end of the fault). Piled-up soil fragments are compressional mounds that formed between the ends of echelon fractures in the ground. View is northwest.J.C. Tinsley measured 45 degrees and 3 centimeters of dextral displacement on offset crop rows in this field.
Scarp of the Brawley Fault zone at Keystone Road site 100 (location shown on Plate 1, Professional paper 1254). The cracks (dark line) in the pavement formed at the crest of the scarp where the flexure of the ground is greatest. The base of the scarp generally is on the west side of the cracking for all strands of the Bradley Fault Zone. This position of cracking with respect to the base of the scarp is generally present in fields as well as at road intercepts. Leveling of the profile before and after the earthquake indicated that about 9 centimeters of the total relative uplift of about 16 centimeters at the scarp was due to the October 15 earthquake. Across an 80-meter wide zone centered on the fault scarp, the total relative uplift since the road was paved in 1960 or 1961 is about 0.5 meter. View is east.
Lateral spread at site 13 on Heber Road (location shown on Plate 1, Professional paper 1254), showing associated displacements, fissures, and sand boils. The pavement on Heber Road settled, cracked, and shifted to the south by as much as 1.2 meters. View is east.
Slumped banks of the Barbara Worth Drain at site 30 (location shown on Plate 1, Professional paper 1254). The slump in the east bank destroyed a farm lane and blocked the drain. View is south.
East end of the Imperial County Services Building, showing a row of columns (far right) that failed during the main shock. View is north.