Improving estimates of the b-value in regional catalogs by means of the the b-more-positive method
DOI:
https://doi.org/10.26443/seismica.v5i2.1689Abstract
The b-value, which controls the slope of the frequency-magnitude distribution of earthquakes, is a critical parameter in seismic forecasting. However, accurately measuring the true b-value is challenging due to the temporal and spatial variations in the completeness of instrumental seismic catalogs. In this study, we systematically compare traditional methods for estimating the b-value with newer approaches, specifically focusing on the b-more-positive estimator based on positive magnitude difference statistics. We conduct this comparison using both synthetic ETAS catalogs, with artificially introduced incompleteness, and instrumental catalogs from five regions: Japan, Italy, Southern California, Northern California, and New Zealand. Our analysis of synthetic ETAS catalogs demonstrates that traditional estimators systematically underestimate the b-value under incompleteness scenarios, whereas the b-more-positive estimator yields highly accurate results. Consistent patterns are found in instrumental catalogs, suggesting that conventional methods also underestimate the b-value in real datasets, with important implications for seismic forecasting. Moreover, the b-more-positive estimator provides robust evidence of significant differences in the b-value across the considered geographic regions.
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