Documentation of benchmark photographs that show the effects of the 1983 Borah Peak earthquake with some considerations for studies of scarp degradation

Abstract

Systematic benchmark photography of modern and prehistoric fault scarps provides an accurate and timely method of documenting details of ground breakage related to earthquakes and provides a near-permanent record for future quantitative analysis of the degradation of these features. During the geologic investigation of surface faulting associated with the 28 October 1983 Borah Peak earthquake of central Idaho, I established 14 benchmark stations for repeat photography of selected deformational features. About 40 photographs (most in stereopairs) were made in November 1983 in order to show some of the details of the newly formed fault scarps, grabens, and an associated landslide. One year later (October 1984), H. E. Malde and I repeated most of the 1983 photographs and photographed from 14 additional stations. This paper provides an account of the location and subject of the photographs that are on file at the U.S. Geological Survey Photo Library in Denver. Hopefully, this study will provide the impetus for including systematic benchmark photography in future studies of ground deformation.