DYNAMICS OF A CREEP-SLIP MODEL OF EARTHQUAKE FAULTS

Starting off from the relationship between lime-dependent friction and velocity softening we present a generalization of the continuous, one -dimensional homogeneous Burridge-Knopoff (BK) model by allowing for d isplacements by plastic creep and rigid sliding. The evolution equatio ns describe the coupled dynamics of an order parameter-like field vari able (the sliding rate) and a control parameter field (the driving for ce). In addition to the velocity-softening instability and determinist ic chaos known from the BK model, the model exhibits a velocity-streng thening regime at low displacement rates which is characterized by ano malous diffusion and which may be interpreted as a continuum analogue of self-organized criticality (SOC). The governing evolution equations for both regimes (a generalized time-dependent Ginzburg-Landau equati on and a non-linear diffusion equation, respectively) are derived and implications with regard to fault dynamics and power-law scaling of ev ent-size distributions are discussed. Since the model accounts for mem ory friction and since it combines features of deterministic chaos and SOC it displays interesting implications as to (i) material aspects o f fault friction, (ii) the origin of scaling, (iii) questions related to precursor events, aftershocks and afterslip, and (iv) the problem o f earthquake predictability. Moreover, by appropriate re-interpretatio n of the dynamical variables the model applies to other SOC systems, e .g. sandpiles. (C) 1998 Published by Elsevier Science B.V. All rights reserved. PACS: 05.45.+b; 46.30.Pa; 47.20.Ky; 91.30.Px.