Seismotectonics-Driven Estimation of b-Value: Implications for Seismic Hazard Assessment

<jats:title>Abstract</jats:title>
<jats:p>Taking full advantage of good-quality historical earthquake and seismogenic source data available for Italy (Catalogo Parametrico dei Terremoti Italiani [CPTI15] and Database of Individual Seismogenic Sources [DISS] databases), we tested the regional variability of the b-value of the Gutenberg–Richter law, focusing on the dominantly extensional, nearly 1200-km-long seismogenic corridor straddling the Apennines chain; an 18,200  km2 area generating about 45% of the seismic moment released countrywide. We carefully chose and tested the most appropriate completeness interval and completeness magnitude (Mc), and used the Lilliefors method, the Utsu test, and a bootstrap technique to verify the quality of our results and inferences. The 0.65 b-value we obtained is substantially lower than b-values used in Italian seismic hazard models, often close to 1.0; yet it predicts more accurately the observed Apennines earthquake record, suggesting that most currently adopted magnitude-frequency distributions underpredict events in the Mw range 6.0–7.1 and overpredict those in the range 5.2–5.5. We also highlight that the time, space, and magnitude distribution of the largest Italian earthquakes hardly follows the Gutenberg–Richter law: it rather favors a characteristic behavior. We contend that the b-value is too critical of a parameter for being calculated using statistically weak data sets, such as those resulting from overly detailed area-source models: one may end up characterizing low-hazard areas more accurately than high-hazard areas. Conversely, we advocate the use of fewer, larger area sources that fully exploit the current understanding of regional seismotectonics, as a way of obtaining more realistic regional hazard models.</jats:p>

Aki, K. (1965).Maximumlikelihood estimate of b in the formula logN=a
−bm and its confidence limits, Bull. Earthq. Res. Inst. Tokyo Univ. 43,
237–239.
Albarello, D., R. Camassi, and A. Rebez (2001). Detection of space and
time heterogeneity in the completeness level of a seismic catalogue by
a “robust” statistical approach: An application to the Italian area, Bull.
Seismol. Soc. Am. 91, no. 6, 1694–1703, doi: 10.1785/0120000058.
Amorèse, D., J. R. Grasso, and P. A. Rydelek (2010). On varying bvalues
with depth: Results from computer-intensive tests for
southern California, Geophys. J. Int. 180, no. 1, 347–360, doi:
10.1111/j.1365-246X.2009.04414.x.
Basili, R., G. Valensise, P. Vannoli, P. Burrato, U. Fracassi, S. Mariano,
M. M. Tiberti, and E. Boschi (2008). The Database of Individual
Seismogenic Sources (DISS), version 3: Summarizing 20 years of
research on Italy’s earthquake geology, Tectonophysics 453, 20–43,
doi: 10.1016/j.tecto.2007.04.014.
Camassi, R., and V. Castelli (2005). Journalistic communication in the
17th-18th centuries and its influence on the completeness of
seismic catalogues, Boll. Geof. Teor. Appl. 46, 99–110.
Camassi, R., and M. Stucchi (1997). NT4.1, un catalogo parametrico di
terremoti di area italiana al di sopra della soglia del danno,
Published by GNDT, Milan, Italy, available at https://emidius
.mi.ingv.it/DOM/ (last accessed May 2024) (in Italian).
D’Agostino, N. (2014). Complete seismic release of tectonic strain and
earthquake recurrence in the Apennines (Italy), Geophys. Res. Lett.
41, 1155–1162, doi: 10.1002/2014GL059230.
Danciu, L., S. Nandan, C. Reyes, R. Basili, G. Weatherill, C. Beauval, A.
Rovida, S. Vilanova, K. Sesetyan, P-Y. Bard, et al. (2021). The 2020
update of the European seismic hazard model: Model overview,
EFEHR Technical Rept. 001, v.1.0.0, doi: 10.12686/a15.
Di Bucci, D., P. Burrato, P. Vannoli, and G. Valensise (2010). Tectonic
evidence for the ongoing Africa-Eurasia convergence in central
Mediterranean foreland areas: A journey among long-lived shear
zones, large earthquakes, and elusive fault motions, J. Geophys. Res.
115, no. B12, doi: 10.1029/2009JB006480.
DISS Working Group (2021). Database of Individual Seismogenic Sources
(DISS), version 3.3.0: A compilation of potential sources for earthquakes
larger than M 5.5 in Italy and surrounding areas, Istituto
Nazionale di Geofisica e Vulcanologia (INGV), doi: 10.13127/diss3.3.0.
Efron, B. (2003). Second thoughts on the Bootstrap, Stat. Sci. 18, no. 2,
135–140, doi: 10.1214/ss/1063994968.
Efron, B., and T. J. Tibshirani (1993). An Introduction to the
Bootstrap, Chapman and Hall, London, 436 pp.
Fracassi, U., and G. Valensise (2007). Unveiling the sources of the
catastrophic 1456 multiple earthquake: Hints to an unexplored
tectonic mechanism in southern Italy, Bull. Seismol. Soc. Am.
97, 725–748, doi: 10.1785/0120050250.
Galli, P., F. Galadini, and D. Pantosti (2008). Twenty years of palaeoseismology
in Italy, Earth Sci. Rev. 88, 89–117, doi: 10.1016/j.earscirev.
2008.01.001.
Gerstenberger, M. C., W. Marzocchi, T. Allen, M. Pagani, J. Adams, L.
Danciu, E. Field, H. Fujiwara, N. Luco, K.-F. Ma, et al. (2020).
Probabilistic seismic hazard analysis at regional and national scale:
State of the art and future challenges, Rev. Geophys. 58, no. 2,
e2019RG000653, doi: 10.1029/2019RG000653.
Gruppo di Lavoro CPTI (2004). Catalogo Parametrico dei Terremoti
Italiani (CPTI04), Istituto Nazionale di Geofisica e Vulcanologia
(INGV), Bologna, Italy, doi: 10.6092/INGV.IT-CPTI04 (in
Italian).
Gulia, L., and S. Wiemer (2019). Real-time discrimination of earthquake
foreshocks and aftershocks, Nature 574, 193–199, doi:
10.1038/s41586-019-1606-4.
Gutenberg, B., and C. F. Richter (1944). Frequency of earthquakes in
California, Bull. Seismol. Soc. Am. 34, 185–188.
Herrmann, M., and W. Marzocchi (2021). Inconsistencies and lurking
pitfalls in the magnitude-frequency distribution of high-resolution
earthquake catalogs, Seismol. Res. Lett. 92, no. 2A, 909–922, doi:
10.1785/0220200337.
Ishimoto, M., and K. Iida (1939). Observations of earthquakes registered
with the microseismograph constructed recently, Bull.
Earthq. Res. Inst. Tokyo Univ. 17, 443–478.
Kagan, Y. Y., D. D. Jackson, and R. J. Geller (2012). Characteristic
earthquake model, 1884-2011, R.I.P, Seismol. Res. Lett. 83, no. 6,
951–953, doi: 10.1785/0220120107.
Konstantinou, K. I. (2022). Multiyear temporal variation of b-values at
Alaskan volcanoes: The synergetic influence of stress and material
heterogeneity, J. Volcanol. Geotherm. Res. 427, 107572, doi:
10.1016/j.jvolgeores.2022.107572.
Lilliefors, H. W. (1967). On the Kolmogorov-Smirnov test for normality
with mean and variance unknown, J. Am. Stat. Assoc. 62,
no. 318, 399–402.
Lombardi, A.M. (2021). A normalized distance test for co-determining
the completeness magnitude and b-value of earthquake catalogs, J.
Geophys. Res. 126, e2020JB021242, doi: 10.1029/2020JB021242.
Marzocchi, W., and L. Sandri (2003). A review and new insights on
the estimation of the b-value and its uncertainty, Ann. Geophys. 46,
no. 6, 1271–1282, doi: 10.4401/ag-3472.
Meletti, C., W. Marzocchi, V. D’Amico, G. Lanzano, L. Luzi, F.
Martinelli, B. Pace, A. Rovida, M. Taroni, F. Visini, et al. (2021).
The new Italian seismic hazard model (MPS19), Ann. Geophys. 64,
doi: 10.4401/ag-8579.
Molchan, G., T. Kronrod, and G. F. Panza (1997). Multi-scale seismicity
model for seismic risk, Bull. Seismol. Soc. Am. 87, no. 5, 1220–
1229, doi: 10.1785/BSSA0870051220.
Mucciarelli, M., L. Peruzza, and P. Caroli (2000). Tuning of seismic
hazard estimates by means of observed site intensities, J. Earthq.
Eng. 4, 141–159, doi: 10.1080/13632460009350366.
Parsons, T., E. L. Geist, R. Console, and R. Carluccio (2018).
Characteristic earthquake magnitude frequency distributions on
faults calculated from consensus data in California, J. Geophys.
Res. 123, 10,761–10,784, doi: 10.1029/2018JB016539.
Rovida, A., M. Locati, R. Camassi, B. Lolli, and P. Gasperini (2020).
The Italian earthquake catalogue CPTI15, Bull. Earthq. Eng. 18,
2953–2984, doi: 10.1007/s10518-020-00818-y.
Rovida, A., M. Locati, R. Camassi, B. Lolli, P. Gasperini, and A.
Antonucci (2022). Catalogo Parametrico dei Terremoti Italiani
(CPTI15), INGV versione 4.0, doi: 10.13127/CPTI/CPTI15.4 (in
Italian).
Santulin, M., A. Tamaro, A. Rebez, D. Slejko, F. Sani, L. Martelli, M.
Bonini, G. Corti, M. E. Poli, A. Zanferrari, et al. (2017).
Seismogenic zonation as a branch of the logic tree for the new
Italian seismic hazard map–MPS16: A preliminary outline, Boll.
Geof. Teor. Appl. 58, 313–342, doi: 10.4430/bgta0216.
Scholz, C. H. (2015). On the stress dependence of the earthquake b
value, Geophys. Res. Lett. 42, doi: 10.1002/2014GL062863.
Schorlemmer, D., S. Wiemer, and M. Wyss (2004). Earthquake
statistics at Parkfield: 1. Stationarity of b-values, J. Geophys. Res.
109, no. B12, doi: 10.1029/2004JB003234.
Shi, Y., and B. A. Bolt (1982). The standard error of the magnitudefrequency
b value, Bull. Seismol. Soc. Am. 72, 1677–1687, doi:
10.1785/BSSA0720051677.
Slejko, D., L. Peruzza, and A. Rebez (1998). Seismic hazard maps of
Italy, Ann. Geofis. 41, 183–214.
Slejko, D., G. Valensise, C. Meletti, and M. Stucchi (2022). The assessment
of earthquake hazard in Italy: A review, Ann. Geophys. 65,
doi: 10.4401/ag-8863.
Stirling, M. W., S. G. Wesnousky, and K. Shimazaki (1996). Fault trace
complexity, cumulative slip, and the shape of the magnitude-frequency
distribution for strike-slip faults: A global survey, Geophys.
J. Int. 124, 833–868, doi: 10.1111/j.1365-246X.1996.tb05641.x.
Stucchi, M., P. Albini, C. Mirto, and A. Rebez (2004). Assessing the
completeness of Italian historical earthquake data, Ann. Geophys.
47, nos. 2/3, 659–674, doi: 10.4401/ag-3330.
Stucchi, M., C. Meletti, V. Montaldo, H. Crowley, G. M. Calvi, and E.
Boschi (2011). Seismic hazard assessment (2003–2009) for the
Italian building code, Bull. Seismol. Soc. Am. 101, no. 4, 1885–
1911, doi: 10.1785/0120100130.
Taroni, M. (2023). Estimating the magnitude of completeness of
earthquake catalogs using a simple random variable transformation,
Seism. Rec. 3, no. 3, 194–199, doi: 10.1785/0320230017.
Tormann, T., S. Wiemer, and A. Mignan (2014). Systematic survey of
high-resolution b value imaging along Californian faults: Inference
on asperities, J. Geophys. Res. 119, no. 3, doi: 10.1002/2013JB010867.
Udías, A., and E. Buforn (2017). Principles of Seismology, Second Ed.,
Cambridge University Press, Cambridge, 544 pp., doi: 10.1017/
9781316481615.
Utsu, T. (1992). On Seismicity, Report of the Joint Research Institute
for Statistical Mathematics, Vol. 34, Tokyo, 139–157.
Utsu, T. (1999). Representation and analysis of the earthquake size
distribution: A historical review and some approaches, Pure
Appl. Geophys. 155, 509–535.
Vannoli, P., G. Martinelli, and G. Valensise (2021). The seismotectonic
significance of geofluids in Italy, Front. Earth Sci. 9, doi:
10.3389/feart.2021.579390.
Visini, F., C. Meletti, A. Rovida, V. D’Amico, B. Pace, and S. Pondrelli
(2022). An updated area-source seismogenic model (MA4) for
seismic hazard of Italy, Nat. Hazards Earth Syst. Sci. 22, 2807–
2827, doi: 10.5194/nhess-22-2807-2022.
Wesnousky, S. G. (1994). The Gutenberg-Richter or characteristic
earthquake distribution, which is it? Bull. Seismol. Soc. Am. 84,
no. 6, 1940–1959, doi: 10.1785/BSSA0840061940.
Wesnousky, S. G., C. H. Scholz, K. Shimazaki, and T. Matsuda (1983).
Earthquake frequency distribution and the mechanics of faulting, J.
Geophys. Res. 88, no. B11, 9331–9340, doi: 10.1029/JB088iB11p09331.
Wössner, J., and S. Wiemer (2005). Assessing the quality of earthquake
catalogues: Estimating the magnitude of completeness
and its uncertainty, Bull. Seismol. Soc. Am. 95, no. 2, 684–698,
doi: 10.1785/0120040007.
Wössner, J., L. Danciu, D. Giardini,H. Crowley, F. Cotton, G. Grünthal,
G. Valensise, R. Arvidsson, R. Basili, M. B. Demircioglu, et al.
(2015). The 2013 European Seismic hazard model: Key components
and results, Bull. Earthq. Eng. 13, 3553–3596, doi: 10.1007/s10518-
015-9795-1.
Youngs, R. R., and K. J. Coppersmith (1985). Implications of fault slip
rates and earthquake recurrence models to probabilistic seismic
hazard estimates, Bull. Seismol. Soc. Am. 75, 939–964.