thumbnail

Paleoseismology and neotectonics of the Shivwits section of the Hurricane Fault, northwestern Arizona

Bulletin of the Seismological Society of America

By:
, , and
DOI: 10.1785/012003241

Links

Abstract

The Shivwits section of the Hurricane Fault in northwestern Arizona has been largely ignored in evaluating the seismic hazard posed to the rapidly growing populations of southwestern Utah. To assess this hazard, we conducted studies along the Shivwits section using field observations and geomorphic modeling to understand the Quaternary tectonism of this portion of the Hurricane Fault. We have found evidence that it ruptured with up to 2 to 3 m of vertical displacement per event and likely produced ???M 7 earthquakes. Our results suggest that the slip rate along the southern Hurricane Fault has not decreased during the Quaternary. The Moriah Knoll basalt, offset 150 to 200 m along the Hurricane Fault, yielded a maximum long-term slip rate of 0.15 to 0.25 mm/yr, estimated using a new 40Ar/39Ar age of 0.85 ?? 0.06 Ma. The late Quaternary slip rates on alluvial fan surfaces offset 2 to 7.4 m were estimated using pedogenic carbonate rind thickness as a calibrated proxy for age. These observations yielded slip rates of ??? 0.05 to 0.3 mm/yr. Paleoseismic trench investigations showed that two surface-rupturing events occurred in the past 15-78 k.y. A radiocarbon sample from a most-recent event (MRE) fissure yielded a calibrated age of 8900-10,400 years B.P.; the penultimate event was likely ??? 10 k.y. before the most recent event. Slip-rate estimates using the Moriah Knoll basalt (???0. 15-0.24 mm/yr; 850 ka), surface offset (???0.05-0.3 mm/yr; < 100 ka), morphologic modeling (??? 0.06-0.21 mm/yr; <100 ka), and observations from the trench (??? 0.06-0.34 mm/yr; 15-75 ka) suggest that there has been no detectable change in slip rate in the past 1 million years or so. This implies a constant deformation rate for this portion of the Colorado Plateau Margin; therefore, Basin and Range extension is actively encroaching.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Paleoseismology and neotectonics of the Shivwits section of the Hurricane Fault, northwestern Arizona
Series title:
Bulletin of the Seismological Society of America
DOI:
10.1785/012003241
Volume
94
Issue:
5
Year Published:
2004
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Bulletin of the Seismological Society of America
First page:
1919
Last page:
1942