J2. Normal fault. Scarp near Beni Rached. 1980 El Asnam Earthquake [4].
The surface faulting illustrated in this slide occurred along the Beni Rached fault, a high angle normal fault that appears to be a secondary splay of the Oued Fodda fault which ruptured during the El Asnam Earthquake of October 10, 1980. The Richter magnitude of this event was 7.2 [4]. The surface faulting occurred along a zone that extended at least 30 kilometers. In most places the surface faulting along the Beni Rached fault was expressed as a simple well-defined fault scarp with vertical displacement averaging about 1 meter. Numerous small graben and extension cracks occurred on the downthrown side along the base of the fault scarp. Apparent right and left lateral offsets of approximately 0.5 to 1 meter were measured along the fault. Many sheep and donkeys were trapped along the surface faulting.
Railroads
J3. Overturned train during the 1980 El Asnam Earthquake.
The east-west railroad between Algiers and Oran and passing through El Asnam crosses the main thrust of the Oued Fodda fault about 15 km east of El Asnam outside the town of Oued Fodda. At the time of the main shock a train going from El Asnam to Algiers was straddling the fault. The train was completely overturned as illustrated in Slide J3. It took about seven days before the work crews could clear the wreckage and reopen the railway. At another site near the location illustrated in this slide the railroad tracks were bent; it is suspected that this may have been caused by a secondary fault.
J4. Bent rails of the railroad between Guatemala City and Puerto Barrios caused by the 1976 Guatemala Earthquake.
A Richter magnitude M = 7.9 earthquake struck the country of Guatemala on February 4, 1976 causing more than 22,000 deaths, 70,000 injuries and widespread devastation leaving over a million people homeless. The cause of this destructive earthquake was the rupture of the long Montagua fault which is the boundary between the Caribbean and North American plates. Surface faulting was seen for a distance of about 250 kilometers. The offset was left-lateral with an average slip of 1 meter and a maximum measured value of 3.25 meters. Ground rupture along the Montagua fault appeared as a series of parallel cracks. The width of the cracked zone in general varied from 1 to 3 meters but at some locations was as wide as 9 meters [5]. The fault rupture offset the railroad tracks (as illustrated by Slide J4), irrigation channels (Slide J5), bridges (as discussed below) and roads.
Irrigation Channels
J5. Damage to irrigation channel produced by the surface rupture along the Montagua fault during the 1976 Guatemala Earthquake.
Bridges
Slides J6 through J9 illustrate the damage to a bridge due to surface movements along the Montagua fault during the 1976 Guatemala Earthquake. The only main highway between Guatemala City and Puerto Barrios (in the Gulf of Honduras) goes along the Montagua fault. At Agua Caliente, located about 27 kilometers from Guatemala City, there was a five-span steel plate girder bridge. The three central spans of this bridge were simply supported on four tall reinforced concrete piers (frames) as illustrated in Slides J6 and J7. Because of the poor detailing of the supports for these spans (the short supported lengths) and the relative movement between piers, the three central spans collapsed. Slide J8 shows the two main steel girders of one of these central spans, twisted by impact on striking the ground. Slide J9 shows the details of the support of the end span.
J6. Overall view of the collapse of the three central spans of the bridge at Agua Caliente caused by the 1976 Guatemala Earthquake.
J8. The collapsed (twisted) main girders of the bridge, at the base of the piers.
J7. View of the three intermediate piers that supported the bridge.
J9. Detail of the girder support (fixed bearing) at one of the abutments of the bridge.
Lifelines
The M = 6.5 San Fernando Earthquake of February 9, 1971, which resulted in only 65 deaths but produced damage evaluated at more than $550,000,000 (1971 dollars), was caused by the rupture along the Santa Susana and the San Fernando faults [6]. The fault offset (up to 1 meter vertically and 1 meter laterally) produced considerable damage to the lifelines in the San Fernando Valley. Slide J10 illustrates the rupture of water and sewage lines that crossed the fault rupture. Some of the steel gas pipes were compressed and ruptured, causing gas leakage, resulting in fires.
J10. In Sylmar (San Fernando Valley, north of Los Angeles), water and sewage lines crossing the fault ruptured during the 1971 San Fernando Earthquake.
Buildings
Damage to buildings and facilities along the fault scarps of the San Fernando Earthquake of February 9, 1971 varied considerably, ranging from completely demolished houses, to rupture of the foundations, tilting of the foundation slabs and walls (as illustrated in Slide J11), and to houses that suffered minor damage.
J11. Superficial cracks and damage to a building located in the Sylmar area, during the 1971 San Fernando Earthquake.
The University of California, Berkeley Copyright 1997, The Regents of the University of California. Structural Engineering Slide Library, W. G. Godden, Editor Set J: Earthquake Engineering, V. V. Bertero
