Temporal variation in fault friction and its effects on the slip evolution of a thrust fault over several earthquake cycles

Abstract

Terra Nova, 24, 357–362, 2012 Abstract The friction coefficient is a key parameter for the slip evolution of faults, but how temporal changes in friction affect fault slip is still poorly known. By using three‐dimensional numerical models with a thrust fault that is alternately locked and released, we show that variations in the friction coefficient affect both coseismic and long‐term fault slip. Decreasing the friction coefficient by 5% while keeping the duration of the interseismic phase constant leads to a four‐fold increase in coseismic slip, whereas a 5% increase nearly suppresses slip. A gradual decrease or increase of friction over several earthquake cycles (1–5% per earthquake) considerably alters the cumulative fault slip. In nature, the slip deficit (surplus) resulting from variations in the friction coefficient would presumably be compensated by a longer (shorter) interseismic phase, but the magnitude of the changes required for compensation render variations of the friction coefficient of >5% unlikely.

Horizontal surface velocity and strain patterns near thrust and normal faults during the earthquake cycle: The importance of viscoelastic relaxation in the lower crust and implications for interpreting geodetic data

“…During the second step, slip on the fault is initiated by extension or shortening of the model, and at this stage, the fault slips continuously. Its slip rate, which we do not prescribe, increases gradually until it reaches a constant value that depends on the velocity boundary condition applied at the model side [cf., Hampel and Hetzel , ]. Note that the constant slip rate is reached when the entire fault plane is activated (i.e., the establishment of constant slip is not linked to the behavior of the viscous model layers).…”

“…Allowing the fault to reach a steady state slip rate prior to the first earthquake cycle ensures that the results obtained from the modeled earthquake do not depend on the number of previous earthquake cycles. In other words, continuous fault slip at a steady state slip rate and perfectly periodic earthquake cycles are equivalent in our model [cf., Hampel and Hetzel , ]. As a consequence, the initial model phase with continuous fault slip until establishment of a steady state slip rate can be regarded as equivalent to spinning‐up the model through a sufficient number of earthquake cycles such that the results become invariant between one cycle and the next [e.g., Savage and Prescott , ; Hetland and Hager , ].…”

“…To simulate the earthquake, we unlock the fault, which leads to a sudden slip on the fault plane owing to the strain accumulated during the previous locking phase. The transition between the locked and unlocked fault states is achieved by changing the boundary conditions on the fault [cf., Hampel and Hetzel , ]. We emphasize that the amount of coseismic slip is not prescribed but develops freely as a function of the long‐term fault slip rate, the length of the preseismic phase, and the rheological properties of the fault and the surrounding lithosphere [cf., Hampel and Hetzel , ].…”

Laboratory observations of time‐dependent frictional strengthening and stress relaxation in natural and synthetic fault gouges

“…The evolution of fault strength during the seismic cycle exerts an important control on earthquake size and recurrence [ Hiller et al ., ; De Paola et al ., ; Hampel and Hetzel , ; McLaskey et al ., ]. In order for a fault (or fault patch) to undergo repeated earthquake failure, it must have the ability to restrengthen during the interseismic period [ Brace and Byerlee , ; Brace , ; Dieterich , , ].…”

Postseismic Coulomb stress changes on intra-continental dip-slip faults due to viscoelastic relaxation in the lower crust and lithospheric mantle: insights from 3D finite-element modelling

“…During the initial model phase, all faults slip continuously to let them achieve a constant slip rate (cf. Hampel and Hetzel, 2012). After all faults have attained a constant slip rate, the earthquake cycle is simulated in three steps (cf.…”