Regional variations in the diffusion of triggered seismicity
- ISSN: 01480227
- DOI: 10.1029/2004JB003387
We determine the spatiotemporal characteristics of interearthquake\ntriggering in the International Seismological Centre catalogue on\nregional and global scales. We pose a null hypothesis of spatially\nclustered, temporally random seismicity, and determine a residual\npair correlation function for triggered events against this background.\nWe compare results from the eastern Mediterranean, 25 Flinn-Engdahl\nseismic regions, and the global data set. The null hypothesis cannot\nbe rejected for distances greater than 150 km, providing an upper\nlimit to triggering distances that can be distinguished from temporally\nuncorrelated seismicity in the stacked data at present. Correlation\nlengths L and mean distances between triggered events hri are on\nthe order of 10 50 km, but can be as high as 100 km in subduction\nzones. These values are not strongly affected by magnitude threshold,\nbut are comparable to seismogenic thicknesses, implying a strong\nthermal control on correlation lengths. The temporal evolution of\nL and hri is well fitted by a power law, with an exponent H 0.1 ?\n0.05. This is much lower than the value H = 0.5 expected for Gaussian\ndiffusion in a homogenous medium. We observe clear regional variations\nin L, hri and H that appear to depend on tectonic setting. A detectable\ntransition to a more rapid diffusion regime occurs in some cases\nat times greater than 100 200 days, possibly due to viscoelastic\nprocesses in the ductile lower crust.