On‐Fault Geological Fingerprint of Earthquake Rupture Direction

Abstract

How earthquake ruptures evolve and propagate are major outstanding questions in seismology. Our current understanding is limited to modern events captured by seismic networks, making it impossible to observe rupture propagation that occurred during earthquakes in the distant past. Here we propose a new method to discern the rupture propagation directions of past large earthquakes based on geological features preserved on fault slip planes. These features-called slickenlines-are striations formed during seismic slip and record dynamic fault movement during past surface-breaking earthquakes. We develop a theoretical framework that links slickenline curvature with rupture mode and rupture propagation direction for all faulting types and test our model using a global catalogue of historical surface-rupturing earthquakes with seismologically constrained rupture directions. Our results reveal that historical observations are consistent with theoretical predictions, thus providing a robust way to uncover the rupture directions of large earthquakes that lack instrumental data. Plain Language Summary How earthquake ruptures evolve and propagate are major outstanding questions in seismology. Currently, we are unable to observe the details of earthquakes that occurred in the distant past, which limits our understanding to events recorded by modern technology. Here we propose a new method to uncover the rupture propagation direction of past large earthquakes, using geological features preserved on faults scarps. These features-called slickenlines-are scratch marks that form when two sides of a fault move past one another during an earthquake. We develop a theoretical framework that links the geometry of slickenlines with rupture propagation direction for all types of faults and test our model using a global catalogue of surface-breaking earthquakes. Our results reveal a strong link between our model and the available data, providing a new way to uncover the rupture direction of large earthquakes that are not recorded by modern seismic instruments.

Asymmetric Topography Causes Normal Stress Perturbations at the Rupture Front: The Case of the Cajon Pass

“…An analogous effect appears on a vertical strike‐slip fault with asymmetric topography. As shown in Figure 4d and in more detail in Figure S11 in the Supporting Information , we may identify the mountain side of the fault as the “footwall” and the flat side as the “hanging wall.” Even for vertical/symmetrical strike‐slip faults with no topography, strike‐slip motion produces a small component of dip‐slip stress ahead of rupture, and induces a small amount of dip‐slip motion behind the rupture front (e.g., Guatteri & Spudich, 1998a, 1998b; Kearse & Kaneko, 2020). This vertical component of stress and slip is analogous to that of a dip‐slip fault, it also induces clamping and unclamping to match the asymmetric free surface stress boundary condition.…”

Fault Trace Corrugation and Segmentation as a Measure of Fault Structural Maturity

“…Although the concept appeared in early works (Anderson et al., 1996; Chester et al., 1993; Stirling et al., 1996; Wesnousky, 1988), the term was established more recently (Choy & Kirby, 2004; Manighetti et al., 2007) with attempts of quantification based on classifications of specific fault parameters (initiation age, total cumulative slip, length, and slip rate; Manighetti et al., 2007). Nowadays, the concept of fault structural maturity is extensively used, yet with no common definition nor metrics (e.g., Cheng & Barnhart, 2021; Dascher‐Cousineau et al., 2018; DuRoss et al., 2016; Huang, 2018; Kearse & Kaneko, 2020; Materna & Bürgmann, 2016; Perrin et al., 2021; Preuss et al., 2019; Thakur et al., 2020).…”

The Mw 5.1, 9 August 2020, Sparta Earthquake, North Carolina: The First Documented Seismic Surface Rupture in the Eastern United States

“…The initial, deep rupture may be predominantly strikeslip, possibly along a steeper structure with subsequent up-dip failures on shallower preexisting planar discontinuities in the bedrock accommodating most of the reverse component. Slip variations during an earthquake rupture are recognized from recent and historical earthquakes (Kearse and Kaneko, 2020). Further research is needed to understand slip partioning associated with the Sparta earthquake.…”