A Laboratory Perspective on the Gutenberg-Richter and Characteristic
Earthquake Models
Abstract
Probabilistic seismic hazard analysis (PSHA) is the standard method used
for designing earthquake-resistant infrastructure. In recent years,
several unexpected and destructive earthquakes have sparked criticism of
the PSHA methodology. The seismological part of the problem is the true
frequency-magnitude distribution of regional seismicity. Two major
models exist, the Gutenberg-Richter (G-R) and the Characteristic
Earthquake (CE) model, but it is difficult to choose between them. That
is because the instrumental, historical, and paleoseimological data
available are limited in many regions of interest. Here we demonstrate
how a friction experiment on aggregates of glass beads can produce both
regular (CE equivalent) and irregular (G-R equivalent) stick-slip. Using
a new rotary shear apparatus we produced and analysed large catalogs of
acoustic emission (AE) events related to stick-slip. The distributions
of AE sizes, interevent times and interevent distances were found to be
sensitive to particle size and the applied normal stress, and, to a
lesser degree, the stiffness of the loading apparatus. More importantly,
the system spontaneously switched behavior for short periods of time. In
the context of PSHA, if faults are able to switch behavior as our
experimental system does, then justifying the choice of either the CE or
the G-R model is impossible based on existing observations.