Nature of the high-speed rupture of the two-dimensional Burridge-Knopoff model of earthquakes

TL;DR

This study uses extensive simulations to analyze high-speed rupture dynamics in a 2D Burridge-Knopoff earthquake model, revealing anisotropic, irregular rupture patterns and size distributions resembling real earthquake statistics.

Contribution

It provides new insights into the anisotropic and irregular rupture propagation in a uniform 2D model, aligning with observed earthquake behaviors.

Findings

Large events are highly anisotropic and irregular.

Rupture propagation sometimes mimics asperity failures.

Magnitude distribution follows Gutenberg-Richter law for small events.

Abstract

The nature of the high-speed rupture or the main shock of the Burridge-Knopoff spring-block model in two dimensions obeying the rate-and-state dependent friction law is studied by means of extensive computer simulations. It is found that the rupture propagation in larger events is highly anisotropic and irregular in shape on longer length scales, although the model is completely uniform and the rupture-propagation velocity is kept constant everywhere at the rupture front. The manner of the rupture propagation sometimes mimics the successive ruptures of neighboring "asperities" observed in real large earthquakes. Large events tend to be unilateral, with its epicenter lying at the rim of its rupture zone. The epicenter site is also located next to the rim of the rupture zone of some past event. Event-size distributions are computed and discussed in comparison with those of the corresponding one-dimensional model. The magnitude distribution exhibits a power-law behavior resembling the Gutenberg-Richter law for smaller magnitudes, which changes over to a more characteristic behavior for larger magnitudes. The behavior of the rupture length for larger events is discussed in terms of the strongly anisotropic rupture propagation of large events reflecting the underlying geometry.