A unified framework for earthquake sequences and the growth of geological structure in fold-thrust belts

Abstract

Bends in thrust faults create unbalanced elastic stresses within the surrounding medium, which must be relaxed by off-fault deformation • Elasto-plastic models coupled with a frictional boundary integral framework to generate geologically consistent earthquake sequences • Off-fault deformation processes may be most evident during the postseismic period using combined seismo-geodetic methods

Structural controls on coseismic rupture revealed by the 2020Mw 6.0 Jiashi earthquake (Kepingtag belt, SW Tian Shan, China)

“…There are many other examples of large earthquakes that ruptured faults that were not previously mapped, and where historical and instrumental records were too short to have revealed the associated seismic hazard beforehand. Furthermore, fold-and-thrust belts contain a wide range of fault structures including décollements and ramp-and-flat thrusts, and it is often not clear which of these host large earthquakes and which creep aseismically (e.g., Copley, 2014;Ainscoe et al, 2017;Mallick et al, 2021). It is also important to consider how subsurface structure and stratigraphy may influence rupture extents, and thus potential earthquake magnitudes (e.g., Nissen et al, 2011).…”

Space Geodetic Evidence of Basement‐Involved Thick‐Skinned Orogeny and Fault Frictional Heterogeneity of the Papuan Fold Belt, Papua New Guinea

“…The stress change in the shallow sedimentary cover induced by slip on the causative faults during the 2018 PNG earthquake (Figure S14 in Supporting Information S1), shows apparent positive stress perturbation at the locations of several anticlines (e.g., Juha, Lavani, Angore, Mananda, Agogo). This indicates the fold growth during the PNG earthquake also involved distributed off‐fault deformation, which is supported by numerical simulation framework that combines an elastoplastic model of folding with a rate‐state frictional model of fault strength in a layered medium (Mallick et al., 2021). However, due to the mechanical coupling between elastic coseismic slip and off‐fault deformation (i.e., fold growth), it is difficult to distinguish quantitively the folding‐related contribution during large earthquake, which should be considered in the fault kinematics inversion and deserves further study to illustrate more realistic earthquake deformation processes in fold and thrust belts.…”

“…Fault‐related folds represent a significant deformation in compressional regimes (i.e., fold and thrust belts) (Brandes & Tanner, 2014). Numerical simulations suggest that fault bends (e.g., flat‐ramp fault geometry) lead to contemporaneous faulting and folding in the upper plate (Mallick et al., 2021; Sathiakumar et al., 2020). The residual interferograms (Figures 2 and 3 and Figures S1 and S2 in Supporting Information S1), show clear unmodeled residual LOS signal that coincides spatially with some anticlinal ranges, which can be explained by structural growth controlled by faulting propagations during earthquakes (Hanani et al., 2016).…”

“…A nearly universal assumption is that slip on underlying causative faults dominates crustal‐scale fold growth, however, off‐fault deformation especially in the shallow sedimentary cover is a significant component of fold growth (Johnson, 2018; Mallick et al., 2021; Sathiakumar et al., 2020). Boundary element models of fault‐related folding with viscoelastic layers suggest that fold growth involves distributed off‐fault deformation and bedding plane slip (Johnson, 2018).…”

Structural controls on earthquake rupture revealed by the 2020 Mw 6.0 Jiashi earthquake (Kepingtag belt, SW Tian Shan, China)

“…There are many other examples of large earthquakes that ruptured faults were not previously mapped, and where historical and instrumental records were too short to have revealed the associated seismic hazard beforehand. Furthermore, fold-and-thrust belts contain a wide range of fault structures including décollements and ramp-and-flat thrusts, and it is often not clear which of these host large earthquakes and which creep aseismically (e.g., Copley, 2014;Ainscoe et al, 2017;Mallick et al, 2021). It is also important to consider how subsurface structure and stratigraphy may influence rupture extents, and thus potential earthquake magnitudes (e.g., Elliott et al, 2011;Nissen et al, 2011).…”