A plane fault containing two asperities subject to a constant strain rate by the motion of tectonic plates is considered. The fault is modelled as a discrete dynamical system where the average values of stress, friction and slip on each asperity are considered. The state of the fault is described by the slip deficits of the asperities. We study the behaviour of the system in the presence of stress perturbations that are supposed to be due to dislocations of neighbouring faults. The fault complexity entails consequences that are not present in the case of a homogeneous fault. A stress perturbation not only changes the occurrence time of the following earthquake but may also sensitively change the slip amplitude and area, hence the seismic moment, of the earthquake, as well as the position of its hypocentre. The greatest changes take place when simultaneous slip of asperities is involved. A Coulomb stress value can be assigned to each asperity. The change in the difference between the Coulomb stresses of the two asperities is a measure of how much the system gets closer to or farther from the condition for simultaneous slip. As an example, we consider the effect of the 1960 Great Chilean Earthquake on the two-asperity fault that produced the 2010 Maule earthquake and calculate the changes in the moment rate and in the total seismic moment. It results that, in the absence of the 1960 earthquake, the Maule earthquake would have occurred several decades later and would have involved a different sequence of modes, so that the moment rate function would have been very different, with a longer duration and a greater seismic moment.
Dragoni, M., Piombo, A. (2015). Effect of Stress Perturbations on the Dynamics of a Complex Fault. PURE AND APPLIED GEOPHYSICS, 172(10), 2571-2583 [10.1007/s00024-015-1046-5].
Effect of Stress Perturbations on the Dynamics of a Complex Fault
DRAGONI, MICHELE;PIOMBO, ANTONELLO
2015
Abstract
A plane fault containing two asperities subject to a constant strain rate by the motion of tectonic plates is considered. The fault is modelled as a discrete dynamical system where the average values of stress, friction and slip on each asperity are considered. The state of the fault is described by the slip deficits of the asperities. We study the behaviour of the system in the presence of stress perturbations that are supposed to be due to dislocations of neighbouring faults. The fault complexity entails consequences that are not present in the case of a homogeneous fault. A stress perturbation not only changes the occurrence time of the following earthquake but may also sensitively change the slip amplitude and area, hence the seismic moment, of the earthquake, as well as the position of its hypocentre. The greatest changes take place when simultaneous slip of asperities is involved. A Coulomb stress value can be assigned to each asperity. The change in the difference between the Coulomb stresses of the two asperities is a measure of how much the system gets closer to or farther from the condition for simultaneous slip. As an example, we consider the effect of the 1960 Great Chilean Earthquake on the two-asperity fault that produced the 2010 Maule earthquake and calculate the changes in the moment rate and in the total seismic moment. It results that, in the absence of the 1960 earthquake, the Maule earthquake would have occurred several decades later and would have involved a different sequence of modes, so that the moment rate function would have been very different, with a longer duration and a greater seismic moment.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
