Letter abstract
Nature Geoscience 1, 59 - 63 (2008)
Published online: 9 December 2007 | doi:10.1038/ngeo.2007.36
Subject Categories: Seismology | Structural geology, tectonics and geodynamics
Persistent earthquake clusters and gaps from slip on irregular faults
Tom Parsons
Earthquake-producing fault systems like the San Andreas fault in California show self-similar structural variation1; earthquakes cluster in space, leaving aseismic gaps between clusters. Whether gaps represent overdue earthquakes or signify diminished risk is a question with which seismic-hazard forecasters wrestle1, 2, 3, 4, 5. Here I use spectral analysis of the spatial distribution of seismicity along the San Andreas fault (for earthquakes that are at least 2 in magnitude), which reveals that it obeys a power-law relationship, indicative of self-similarity in clusters across a range of spatial scales. To determine whether the observed clustering of earthquakes is the result of a heterogeneous stress distribution, I use a finite-element method to simulate the motion of two rigid blocks past each other along a model fault surface that shows three-dimensional complexity on the basis of mapped traces of the San Andreas fault. The results indicate that long-term slip on the model fault generates a temporally stable, spatially variable distribution of stress that shows the same power-law relationship as the earthquake distribution. At the highest rates of San Andreas fault slip (40 mm yr-1), stress patterns produced are stable over a minimum of 25,000 years before the model fault system evolves into a new configuration. These results suggest that although gaps are not immune to rupture propagation they are less likely to be nucleation sites for earthquakes.
- US Geological Survey, MS-999, 345 Middlefield Rd., Menlo Park, California 94025, USA
Correspondence to: Tom Parsons e-mail: tparsons@usgs.gov
MORE ARTICLES LIKE THIS
These links to content published by NPG are automatically generated.
NEWS AND VIEWS
Earthquake science Faults greased at high speedNature News and Views (29 Jan 2004)
Getting beyond numerologyNature News and Views (20 May 1993)
See all 17 matches for News And ViewsRESEARCH
Implications for prediction and hazard assessment from the 2004 Parkfield earthquakeNature Article (13 Oct 2005)
Particle size and energetics of gouge from earthquake rupture zonesNature Letters to Editor (07 Apr 2005)
See all 45 matches for Research
