Publication Date:
2017-04-04
Description:
We analyzed the correlations among the parameters of the Reasenberg and Jones [Reasenberg, P.A., Jones, L.M., 1989. Earthquake
hazard after a mainshock in California, Science 243, 1173–1176] formula describing the aftershock rate after a mainshock as a
function of time and magnitude, on the basis of parameter estimates made in previous works for New Zealand, Italy and California.
For all of three datasets we found that the magnitude-independent productivity a is significantly correlated with the b-value of
the Gutenberg–Richter law and, in some cases, with parameters p and c of the modified Omori’s law. We also found significant
correlations between p and c but, different from some previous works, not between p and b.We verified that assuming a coefficient
for mainshock magnitude α≈2/3b (instead of b) removes the correlation between a and b and improves the ability to forecast the
behavior of Italian sequences occurred from 1997 to 2003 on the basis of average parameters estimated from sequences occurred
from 1981 to 1996. This assumption well agrees with direct α estimates made in the framework of an epidemic type model (ETAS)
from the data of some large Italian sequences. Our results suggest a modification of the original Reasenberg and Jones (1989)
formulation leading to predict lower rates (and probabilities) for stronger mainshocks and conversely higher rates for weaker ones.
We also inferred that the correlation of a with p and c might be the consequence of the trade-off between the two parameters of the
modified Omori’s law. In this case the correlation can be partially removed by renormalizing the time-dependent part of the rate
equation. Finally, the absence of correlation between p and b, observed for all the examined datasets, indicates that such correlation,
previously inferred from theoretical considerations and empirical results in some regions, does not represent a common property of
aftershock sequences in different part of the world.
Description:
Published
Description:
41-58
Description:
JCR Journal
Description:
reserved
Keywords:
Aftershocks forecasting; Omori law; Gutenberg–Richter law; Parameters correlation
;
05. General::05.01. Computational geophysics::05.01.04. Statistical analysis
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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