Exploring the legacy of strike-slip faulting in the landscape.
Funding Source: US National Science Foundation
Collaborators: Greg Tucker (Co-I) - CU Boulder, Phaedra Upton (co-I) - GNS Science,
GeoScape Team Members: Alison Duvall (PI), Tamara Aranguiz (graduate student), Sarah Harbert (PhD 2019)
Despite the obvious imprint of strike-slip faulting on Earth's surface and the challenges to interpreting this record, few studies have gone beyond the first-order, near-fault tectonic landforms to understand the longer-term geomorphic process response to prolonged lateral fault motion.
Overview
Strike-slip faults, which are among the straightest and longest geologic features on Earth, are often identified by their geomorphic expression, including hallmarks such as offset rivers, shutter ridges, sag ponds, and linear, strike-parallel valleys [e.g., Wallace, 1949; Hill and Dibblee, 1953]. Detailed mapping and dating of such features offer a means for determining fault location and, in the best cases, slip rates.
Fault slip rate estimates form the cornerstone of most paleoseismological and neotectonic studies, as they are instrumental in assessing earthquake hazards, understanding the mechanics of fault zones, and determining changes in fault behavior over time. Slip rates along major faults are commonly found by measuring the magnitude of displacement and the timing of offset landforms such as rivers or river terraces [e.g., Weldon and Sieh, 1985; Berryman, 1990; Mann et al., 1998; Hubert-Ferrari et al., 2002; Van der Woerd et al., 2002; Mériaux et al., 2004; Cowgill, 2007], especially along strike-slip faults where piercing points are sharp and well defined. Although simple in principle, complications with this approach arise from the challenges and uncertainty in dating of landforms as well as ambiguities in terrace-riser reconstructions [Cowgill, 2007; Gold et al., 2009]. Additional difficulties occur in regions where river channels are ephemeral or catchments are young and evolving. In these settings, rivers might not predate fault motion and thus record only a small portion of the fault offset [Lacassin et al., 1998].
from Duvall and Tucker (2015)
Landscape evolution modeling to investigate the longer-term, catchment-wide landscape response to horizontal fault motion demonstrates that strike-slip faulting induces a state of landscape disequilibrium that continues for as long as the fault is active. Comparison of a suite of models with different horizontal slip rates, bedrock erodibility, hillslope diffusivity, and regional uplift rate shows a range of landscape patterns and geomorphic response to lateral forcing. These promising results suggest that in addition to the long-observed process of river offset along active strike-slip faults, analysis of near-fault landforms, such as ridges and facets, as well as the catchments upstream of strike-slip faults, has the potential to reveal important information about tectonic rates and surface processes. Results from this study also suggest that the long-term geomorphic response to strike-slip faulting could be an important yet underappreciated component of landscape development at the orogenic scale.
Many of the world’s active mountain belts are deformed by large strike-slip faults (e.g., Tibet, west coast of N. America, New Zealand, Chile) but only a limited number of studies of landscape evolution [e.g., Anderson, 1990; Braun and Sambridge, 1997; Willett et al., 2001; Miller and Slingerland, 2006; Castelltort et al., 2012] consider any horizontal component of deformation in addition to the vertical. Our findings underscore the need to further consider the role of tectonic advection in long-term landscape evolution, especially in strike-slip settings where motion is dominantly horizontal.
from Duvall and Tucker (2015)
Related Publications:
Harbert, S.A., Duvall, A.R., and Tucker, G.E., 2018, The role of near-fault relief elements in
creating and maintaining a strike-slip landscape: Geophysical Research Letters, 45, 10 pp. http://doi:10.1029/2018GL080045.
Duvall, A.R. and Tucker, Gregory E., 2015, Dynamic Ridges and
Valleys in a Strike-Slip Environment: Journal of Geophysical Research:Earth Surface, v. 120, 10 pp. doi:10.1002/2015JF003618.
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