Simultaneous Dependence of the Earthquake‐Size Distribution on Faulting Style and Depth

• Published in: Geophysical research letters Vol. 46; no. 20; pp. 11044 - 11053
• Main Authors: Petruccelli, A., Gasperini, P., Tormann, T., Schorlemmer, D., Rinaldi, A.P., Vannucci, G., Wiemer, S.
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 28-10-2019; American Geophysical Union
• Subjects: Dependence; Depth; Earth; Earth crust; earthquake forecasting; Earthquakes; Economic models; ENVIRONMENTAL SCIENCES; Geological hazards; Model testing; models evaluation; Null hypothesis; Seismic activity; Seismic hazard; seismic hazard assessment; seismotectonics; Size distribution; statistical modeling; statistical seismology
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2019GL083997

We analyze two high‐quality Southern Californian earthquake catalogues, one with focal mechanisms, to statistically model and test for dependencies of the earthquake‐size distribution, the b values, on both faulting style and depth. In our null hypothesis, b is assumed constant. We then develop and calibrate one model based only on faulting style, another based only on depth dependence and two models that assume a simultaneous dependence on both parameters. We develop a new maximum‐likelihood estimator corrected for the degrees of freedom to assess models' performances. Our results show that all models significantly reject the null hypothesis. The best performing is the one that simultaneously takes account of depth and faulting style. Our results suggest that differential stress variations in the Earth's crust systematically influence b values and that this variability should be considered for contemporary seismic hazard studies.
Key Points
We model the dependence of the b value on depth and tectonic style in Southern California
Statistical tests reveal that faulting style affects the b value more than depth
Simultaneous dependencies result with high statistical significance in the best data description