Recurrence intervals between earthquakes strongly depend on history

Abstract

We study the statistics of the recurrence times between earthquakes above a certain magnitude M$ in California. We find that the distribution of the recurrence times strongly depends on the previous recurrence time $τ_0$. As a consequence, the conditional mean recurrence time $\hat τ(τ_0)$ between two events increases monotonically with $τ_0$. For $τ_0$ well below the average recurrence time $\ovτ, \hatτ(τ_0)$ is smaller than $\ovτ$, while for $τ_0>\ovτ$, $\hatτ(τ_0)$ is greater than $\ovτ$. Also the mean residual time until the next earthquake does not depend only on the elapsed time, but also strongly on $τ_0$. The larger $τ_0$ is, the larger is the mean residual time. The above features should be taken into account in any earthquake prognosis.