Articles | Volume 21, issue 6
Nonlin. Processes Geophys., 21, 1185–1193, 2014
https://doi.org/10.5194/npg-21-1185-2014
Nonlin. Processes Geophys., 21, 1185–1193, 2014
https://doi.org/10.5194/npg-21-1185-2014

Research article 05 Dec 2014

Research article | 05 Dec 2014

Dependence of sandpile avalanche frequency–size distribution on coverage extent and compactness of embedded toppling threshold heterogeneity: implications for the variation of Gutenberg–Richter b value

L.-Y. Chiao1 and Q. Liu2 L.-Y. Chiao and Q. Liu
  • 1Institute of Oceanography, National Taiwan University, Taipei, Taiwan
  • 2Department of Physics, University of Toronto, Toronto, Canada

Abstract. The effects of the spatiotemporal evolution of failure threshold heterogeneity on the dynamics of fault criticality, and thus on regional seismogenesis, have attracted strong interest in the field of regional seismotectonics. The heterogeneity might be a manifestation of the macroscopic distribution and multiscale strength variation of asperities, the distinct regional stress level, and (microscopically) heterogeneous fault surface roughness or friction regimes. In this study, rather than attempting to mimic the complex microscale slipping physics on a fault surface, sandpile cellular automata were implemented with a straightforward toppling rule. The objective is to examine the influence of distinct configurations of the embedded heterogeneous toppling threshold field on the global system avalanche event statistics. The examination results revealed that increasing the coverage extent and decreasing the compactness of the heterogeneous failure threshold, rather than the magnitude, range of contrast, diversity, or the geometric configuration of the threshold heterogeneity, leads to a systematic increase in the scaling exponent of the avalanche event power law statistics, implying the importance of mutual interaction among toppling sites with distinct thresholds. For tectonic provinces with differing stress regimes evolving spatio temporally, it is postulated that the distinct extent and compactness of the heterogeneous failure threshold are critical factors that manifest in the reported dynamic variations of seismicity scaling.

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Short summary
We implemented sandpile cellular automata to examine the effects of the heterogeneous toppling threshold on the global avalanche statistics. A systematic scaling exponent increase is revealed by increasing the coverage extent and decreasing the compactness rather than varying the range of contrast or the diversity. The distinct extent and compactness of the heterogeneous failure threshold are thus likely critical factors that manifest in the reported dynamic variations of seismicity scaling.