Surface slip variability on strike‐slip faults

Abstract

Slip in strike-slip earthquakes is spatially variable along a fault, but the degree to which variability over short length scales is inherent to the rupture process or introduced by interpretation and measurement has not been quantified. In this study, we examine the effects of interpretation error on apparent short-wavelength variability in surface slip distributions by comparing numerical landscape evolution models and recent ruptures on strike-slip faults measured by hand and with image correlation.Surface slip distributions measured by hand from 63 strike-slip earthquakes have average spatial variability (CV slip-spatial = standard deviation/mean) of 0.43-0.52, and a total range of 0.14-1.14. Displacement measurements of offset geomorphic markers from numerical models that simulate constant slip along a fault have average spatial variability of $0.25-0.40 when measured by hand and no spatial variability when measured by image correlation. Slip distributions from seven recent ruptures measured by image correlation have short-wavelength variability of 0.09-0.29, which is considered inherent to how rupture propagates to the surface. Our results demonstrate that variability innate to the rupture process and introduced by interpretation both contribute substantially to the observed variability in slip distributions measured by hand. Resolving the extent to which short-wavelength variability is inherent to rupture propagation through near-surface material versus an artifact of interpretation furthers understanding of the relationship between surface rupture and fault mechanics and informs interpretation of slip distribution and slip-per-event in past earthquakes.

Recovering Surface Slip Distribution Along the Sertengshan Piedmont Fault (Northern China) From Airborne LiDAR Data

“…The reconstructed slip distributions reveal obvious random variation of surface slip along the fault strike. Such high‐frequency along‐fault slip variation has commonly been observed for nearly all recent earthquake ruptures (Elliott et al., 2012; Gold et al., 2013; Haeussler et al., 2004; Klinger et al., 2005; McGill & Rubin, 1999; Nissen et al., 2014; Oskin et al., 2012; Reitman et al., 2022), and may be attributed to measurement uncertainties or local site effects, for example, variation in local fault geometric parameters or site response to seismically induced strain (Zielke et al., 2015). In addition to this high‐frequency slip variation, we also observe slip decrease at the step‐over zone or fault bend between different segments.…”

Spatial and Temporal Analysis of Geologic Slip Rates, Cucamonga Fault, California, USA: Implications for Along‐Strike Applications and Multi‐Fault Rupture

“…Spatial variability in fault slip is considerable and occurs over multiple length scales (e.g., Manighetti et al., 2001; Reitman et al., 2022). It has primarily been examined in single earthquakes (e.g., Manighetti et al., 2005; Moss & Ross, 2011; Wesnousky, 2008).…”

“…The sources of variability are important, in this context, only if they can be used to constrain a representative slip rate. Spatial and temporal variability has been widely documented, but the implications for uncertainty have rarely been quantified (Dolan et al., 2007; Faure Walker et al., 2019; Friedrich et al., 2003; Gold & Cowgill, 2011; Manighetti et al., 2001; McPhillips & Scharer, 2018; Reitman et al., 2022; Resor et al., 2018; Schlagenhauf et al., 2008).…”

“…Cumulative slip may also provide better insights into earthquake processes by averaging stochastic variability of single-earthquake slip (Mai & Beroza, 2002;Styron, 2019). On the other hand, cumulative-slip measurements are vulnerable to modification by surface erosion or long-wavelength topographic changes such as glacial-isostatic rebound (e.g., Jewell & Bruhn, 2013;Reitman et al, 2022Reitman et al, , 2023.…”

“…The sources of variability are important, in this context, only if they can be used to constrain a representative slip rate. Spatial and temporal variability has been widely documented, but the implications for uncertainty have rarely been quantified (Dolan et al, 2007;Faure Walker et al, 2019;Friedrich et al, 2003;Gold & Cowgill, 2011;Manighetti et al, 2001 Milliner et al, 2015;Reitman et al, 2022;Rockwell & Klinger, 2013). The spatial variability of cumulative slip has received less attention than single-earthquake slip, in part because it is frequently challenging to measure cumulative slip over a common time interval at multiple points along strike, although examples exist (e.g., DuRoss, 2008;Frankel et al, 2007;Gunderson et al, 2018;Manighetti et al, 2001;McPhillips & Scharer, 2018;Rood et al, 2011).…”