Dynamic modeling of the 1992 Landers earthquake

Abstract

Abstract. We have used observed band-pass filtered accelerograms and a previously determined slip distribution to invert for the dynamic rupture propagation of the 1992 Landers earthquake. In our simulations, dynamic rupture grows under the simultaneous control of initial stress and rupture resistance by friction, which we modeled using a simple slip-weakening law. We used a simplified Landers fault model where the fault segments were combined into a single vertical, planar fault. By trial and error we modified an initial stress field, inferred from the kinematic slip distribution proposed by Wald and Heaton [1994], until dynamic rupture generated a rupture history and final slip distribution that approximately matched those determined by the kinematic inversion. We found that rupture propagation was extremely sensitive to small changes in the distribution of prestress and that a delicate balance with energy release rate controls the average rupture speed. For the inversion we generated synthetic 0.5 Hz ground displacements using an efficient Green's function propagator method (AXITRA). This method enables us to propagate the radiation generated by the dynamic rupture to distances greater than those feasible using the finite difference method. The dynamic model built by trial-and-error inversion provides a very satisfactory fit between synthetics and strong motion data. We validated this model using records from stations used in the slip inversion as well as some which were not included. We also inverted for a complementary model that fits the data just as well but in which the initial stress was perfectly uniform while rupture resistance was heterogeneous. This demonstrates that inversion of ground motion is nonunique.

A Probable Earthquake Scenario near Istanbul Determined from Dynamic Simulations

“…The uncertainty in the other model parameters fixed in this study (μ s , μ d , σ 0 , and D c in equations 1 and 2) may not be insignificant and could have been taken into account, although they are globally consistent with many other studies presenting dynamic-rupture simulations in which the dynamic stress drop and D c are of the order of 10 MPa and tenths of centimeters, respectively, for an earthquake of magnitude 7 (e.g., Peyrat et al, 2001;Ruiz and Madariaga, 2013). The proposed scenarios in this study are fully comprehensible from the standpoint of the mechanics and, therefore, appear likely.…”

Evidence of fractional-Brownian-motion-type asperity model for earthquake generation in candidate pre-seismic electromagnetic emissions

“…Ample experimental and theoretical evidence support the above mentioned hypothesis: (i) kinematic or dynamic source inversions of EQs suggest that the final slip (or the stress drop) has a heterogeneous spatial distribution over the fault (see among others Gusev, 1992;Bouchon, 1997;Peyrat et al, 2001). (ii) Power spectrum analysis of the fault surface suggests that heterogeneities are observed over a large range of scale lengths (see Power et al, 1987, in particular Fig.…”

Unfolding the procedure of characterizing recorded ultra low frequency, kHZ and MHz electromagnetic anomalies prior to the L'Aquila earthquake as pre-seismic ones - Part 2

“…Ample experimental and theoretical evidence supports the existence of a fractional Brownian motion scheme: (i) kinematic or dynamic source inversions of EQs suggest that the final slip (or the stress drop) has a heterogeneous spatial distribution over the fault (see among others Gusev, 1992;Bouchon, 1997;Peyrat et al, 2001). …”