INSIDE


Earthquake Images
 

Eight photos by IGS staff of the fault scarps and damage caused by the 7.3 magnitude Borah Peak earthquake in 1983 near Challis in east-central Idaho. Images are taken from the IGS publication The Borah Peak Earthquake: A 35-mm Slide Set for Earth Science Educators, S-95-3.


Earthquake damage to the Custer Hotel in Mackay. One of the most severe hazards to people during earthquakes is falling masonry and parapets. This view shows the low strength of untied brickwork when shaken by horizontal earthquake forces.
 
Earthquake damage to the IGA store in Mackay. Many attachments to buildings have strength in the vertical direction only, i.e. strong enough to prevent falling due to gravity. Strong horizontal forces during the earthquake knocked down this store-front cover, and presented an extreme hazard to people trying to exit the building.
 
Multiple fault scarps on the Lost River Fault. Borah Peak is visible in the background.

 
View of Lost River fault scarp crossing Double Springs Rd. View from graben, observer side down.
 
Car crushed by debris from earthquake-damaged building in Mackay. 
 
 
View of the Lost River fault scarp, looking northeast from Double Springs Road, showing vertical offset of the road. A downward curve of the upthrown side of the fault is a relict from an earlier earthquake-generated fault movement. Vertical displacement of the ground along the fault during the 1983 earthquake is approximately the height of the freshly broken ground, or somewhat more than the height of the people standing nearby.
 
View of the headwall and rotated blocks in the upper part of the Birch Creek landslide. Note the sag ponds impounded by the rotated blocks. The landslide probably started at the same time as the intense earthquake vibrations, but because landslide debris covers the fault scarp, the landslide was active longer than the time it took for the fault scarp to form.
 
 
Northwest side of Rock Creek valley showing fault displacement of an irrigation aqueduct. In this view, the apex of Rock Creek's alluvial fan is cut by the fault. The concrete irrigation aqueduct originally curved down across an old scarp formed during an earlier earthquake-generated fault movement. The 1983 fault movement broke the aqueduct as seen in this view.