STUDIES OF QUATERNARY FAULTING ALONG THE SOUTHERN MARGIN OF THE WESTERN SNAKE RIVER PLAIN, IDAHO USING REMOTE SENSING AND GIS

Remote sensing and GIS analyses in combination with geological mapping have been used to interpret Quaternary structural activity along the southern margin of the Western Snake River Plain. Various imagery, including 30m Landsat TM, 30m ASTER and 1m DOQQ imagery in addition to 10m DEM data, have been integrated with magnetic and gravity anomaly data.

The Western Snake River Plain (WSRP) is a continental rift structure bounded by northwest trending normal faults. Surficial materials along the southern margin include lacustrine sediments deposited during 2 episodes of lake occupation, ending about 2 million years ago, and more recently deposited alluvial fans. These sediments record a history of WSRP development characterized by tectonic tilting and faulting. The southern margin provides an excellent area in which to investigate Quaternary tectonic activity due to a relative lack of cultural development and an arid climate that results in sparse vegetation.

After image processing to enhance linear elements, lineaments were digitized from TM, ASTER, and DOQQ data. Identified lineaments were then compared to DLG information to eliminate those that represent cultural features such as roads, fences, and canals. Additional comparisons were made with DEM and DLG drainage data to identify lineaments of drainage origin. Lineaments were then classified by type, such as topographic, tonal change, vegetation anomalies, etc. and plotted on a rose diagrams. Integration of the results of these lineament analyses with groundtruthing at selected locations allows for identification of previously-unrecognized fault traces, as well as extrapolation of known faults beyond the confines of their mapped extents. The fault traces that offset late Pleistocene alluvial fan deposits identified in this study generally fall into two sets based on strike (N35-50W and about N70W).