Late Quaternary Basin-Range faulting north of the eastern Snake River Plain, Idaho

Conference · Thu Apr 01 04:00:00 EST 1993 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5099884

Knuepfer, P L.K. ^[1]

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1. Binghamton Univ., NY (United States). Dept. of Geological Sciences

In the decade since the Borah Peak earthquake, paleoseismic studies have elucidated details of the late Quaternary histories of the Lost River, Lemhi, and Beaverhead faults of eastern Idaho, which comprise part of the northward continuation of the Basin-Range province across the Eastern Snake River Plain (ESRP). The faults are segmented but have temporally and/or spatially clustered paleoseismic activity. Each fault comprises five or six segments with distinct paleoseismic history, and maximum late Quaternary slip rates across the central segments of each fault are ca. 0.5 m/ka. However, the faults differ in their behavior. Portions of two segments of the Lost River fault ruptured during the 1983 earthquake, although the prior ruptures of those two segments appear to have been independent. The three central segments of the Lost River fault have had repeat times of around 6,000 years between the last two surface-rupture earthquakes, with the pre-1983 rupture 6,000--8,000 years ago on each; thus paleoseismic activity appears to be spatially clustered. The southernmost segment has a higher slip rate than the segment immediately to its north, countering arguments that slip on the northern Basin-Range faults decays south to the ESRP. Like the Lost River fault, the Lemhi fault comprises 5--6 fault segments with differing paleoseismic histories. The northern 4 segments appear to have ruptured independently during the late Quaternary, and the last ruptures of adjacent segments appear to have significantly different ages, [approximately]6,000--12,000 years ago. Some segments appear to have had relatively uniform uplift rates during the last 130 ka, whereas at least one segment shows a much higher frequency of surface-rupture events prior to around 30 ka. The southern part of the Lemhi fault displays a complicated paleoseismic history, with two or three ruptures of different parts of the fault closely spaced in the 15--25 ka interval and quiescence in the last 15--18 ka.

• OSTI ID: 5099884
• Report Number(s): CONF-9305259--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 25:5
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
CENOZOIC ERA
DEVELOPED COUNTRIES
DISPLACEMENT RATES
GEOLOGIC AGES
GEOLOGIC FAULTS
GEOLOGIC FRACTURES
GEOLOGIC HISTORY
GEOLOGIC STRUCTURES
IDAHO
NORTH AMERICA
QUATERNARY PERIOD
SEISMICITY
SNAKE RIVER PLAIN
USA