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Properties of Dynamic Earthquake Ruptures With Heterogeneous Stress Drop

Summary: 255
Properties of Dynamic Earthquake Ruptures With
Heterogeneous Stress Drop
J.-P. Ampuero, J. Ripperger, P. M. Mai
Institute of Geophysics, ETH Zürich, Switzerland
Earthquake rupture is a notoriously complex process, at all observable scales.
We introduce a simplified semi-dynamic crack model to investigate the connec-
tion between the statistical properties of stress and those of macroscopic source
parameters such as rupture size, seismic moment, apparent stress drop and radiated
energy. Rupture initiation is treated consistently with nucleation on a linear slip-
weakening fault, whereas rupture propagation and arrest are treated according to
the Griffith criterion. The available stress drop is prescribed as a spatially correlated
random field and is shown to potentially sustain a broad range of magnitudes. By
decreasing the amplitude of the stress heterogeneities or increasing their correlation
length the distribution of earthquake sizes presents a transition from Gutenberg-
Richter to characteristic earthquake behavior. This transition is studied through a
mean-field analysis. The bifurcation to characteristic earthquake behavior is sharp,
reminiscent of a first-order phase transition. A lower roll-off magnitude observed
in the Gutenberg-Richter regime is shown to depend on the correlation length of the
available stress drop, rather than being a direct signature of the nucleation process.


Source: Ampuero, Jean Paul - Division of Geological and Planetary Sciences, California Institute of Technology
Mai, P. Martin - Institut für Geophysik, Eidgenössische Technische Hochschule Zürich (ETHZ)


Collections: Geosciences