Rate‐and‐state friction properties of the Longitudinal Valley Fault from kinematic and dynamic modeling of seismic and aseismic slip

Abstract

The Longitudinal Valley Fault (LVF, Taiwan) is a fast‐slipping fault (∼5 cm/yr), which exhibits both seismic and aseismic slip. Geodetic and seismological observations (1992–2010) were used to infer the temporal evolution of fault slip. This kinematic model is used here to estimate spatial variations of steady state velocity dependence of fault friction and to develop a simplified fully dynamic rate‐and‐state model of the LVF. Based on the postseismic slip, we estimate that the rate‐and‐state parameter (a−b)trueσ̄ decreases from ∼1.2 MPa near the surface to near velocity neutral at 19 km depth. The inferred (a − b) values are consistent with the laboratory measurements on clay‐rich fault gouges comparable to the Lichi Mélange, which borders the LVF. The dynamic model that incorporates the obtained (a−b)trueσ̄ estimates as well as a velocity‐weakening patch with tuned rate‐and‐state properties produces a sequence of earthquakes with some realistic diversity and a spatiotemporal pattern of seismic and aseismic slip similar to that inferred from the kinematic modeling. The larger events have moment magnitude (Mw ∼6.7) similar to the 2003 Chenkung earthquake, with a range of smaller events. The model parameterization allows reproducing partial overlap of seismic and aseismic slip before the earthquake but cannot reproduce the significant postseismic slip observed in the previously locked patch. We discuss factors that can improve the dynamic model in that regard, including the possibility of temporal variations in (a − b) due to shear heating. Such calibrated dynamic models can be used to reconcile field observations, kinematic analysis, and laboratory experiments and assess fault behavior.

Constraints on the Geometry and Frictional Properties of the Main Himalayan Thrust Using Coseismic, Postseismic, and Interseismic Deformation in Nepal

“…Many previous studies have used postseismic deformation as a means of determining the frictional properties of faults (e.g., Barbot et al, 2009;Chang et al, 2013;Hearn, 2002;Hussain et al, 2016;Perfettini & Avouac, 2004;Thomas et al, 2017). Most of these studies assume a rate-and-state friction law (Marone, 1998) where fault friction is related to sliding rate and the state of the fault (e.g., contact time).…”

Probing the Variation in Aseismic Slip Behavior Around an Active Suture Zone: Observations of Repeating Earthquakes in Eastern Taiwan

“…The interseismic slip model by Thomas et al (2014) reveals strong spatial variation of interseismic slip rate along‐strike and along‐dip directions due to a combination of heterogeneous frictional properties and stresses. Given that the majority of repeating earthquakes are located deeper than 7 km, the 4.4‐cm/year rate of Thomas et al (2014, 2017) at the depth above 15 km was adopted. Using the geodetically inferred slip rate of 4.4 cm/year, we obtained a scaling relationship between the slip estimate and seismic moment ( d ‐ Mo ): where α and β have been determined to be −1.21 and 0.11, respectively.…”

Pulse‐like partial ruptures and high‐frequency radiation at creeping‐locked transition during megathrust earthquakes

“…We assume that slip along the megathrust is governed by a rate-and-state friction law, as this framework has been shown to produce realistic models of earthquake sequences, aseismic slip, and individual ruptures [ Barbot et al, 2012;Cubas et al, 2015;Thomas et al, 2017]. We assume that the state variable evolves according to the "aging law" [Dieterich, 1972[Dieterich, , 1979Ruina, 1983].…”