thumbnail

Segmentation and the coseismic behavior of basin and range normal faults. Examples from east-central Idaho and southwestern Montana, USA

Journal of Structural Geology

By:
,
DOI: 10.1016/0191-8141(91)90064-P

Links

Abstract

The range-front normal faults of the Lost River and Lemhi Ranges, and the Beaverhead and Tendoy Mountains in east-central Idaho and southwestern Montana have well-preserved fault scarps on Quaternary deposits along much of their lengths. Fault-scarp morphology, the age of deposits displaced by the faults, and the morphology of the range fronts provide a basis for dividing the faults into segments that are typically 20-25 km long. Four characteristics are recognized that help to identify segment boundaries: (1) major en echelon offsets or pronounced gaps in the continuity of fault scarps; (2) distinct, persistent, along-strike changes in fault-scarp morphology that indicate different ages of faulting; (3) major salients in the range front; and (4) transverse bedrock ridges where the cumulative throw is low compared to other places along the fault zone. Only features whose size is measured on the scale of kilometers are regarded as significant enough to represent a segment boundary that could inhibit or halt a propagating rupture. The ability to identify segments of faults that are likely to behave as independent structural entities will improve seismic-hazard assessment. However, one should not assume that the barriers at segment boundaries will completely stop all propagating ruptures.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Segmentation and the coseismic behavior of basin and range normal faults. Examples from east-central Idaho and southwestern Montana, USA
Series title:
Journal of Structural Geology
DOI:
10.1016/0191-8141(91)90064-P
Volume
13
Issue:
2
Year Published:
1991
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
165
Last page:
176
Number of Pages:
12