Induced Seismicity: What is the Size of the Largest Expected Earthquake?

Abstract:

The injections of fluids is a well-known origin for the triggering of earthquake sequences. The growing number of projects related to enhanced geothermal systems, fracking and others has led to the question, which maximum earthquake magnitude can be expected as a consequence of fluid injection. This question is addressed from the perspective of statistical analysis. Using basic empirical laws of earthquake statistics, we estimate the magnitude M_T of the maximum expected earthquake in a pre-defined future time window T. A case study of the fluid injection site at Paradox Valley, Colorado, USA, demonstrates that the magnitude m=4.3 of the largest observed earthquake on 27 May 2000 is lying very well within the expectation from past seismicity without adjusting any parameters. Vice versa, for a given maximum tolerable earthquake at an injection site, we can constrain the corresponding amount of injected fluids that must not be exceeded within pre-defined confidence bounds.