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Published May 3, 2024 | Version Published
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Why do seismic hazard models worldwide appear to overpredict historical intensity observations?

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Abstract

Probabilistic seismic hazard assessments (PSHAs) provide the scientific basis for building codes to reduce damage from earthquakes. Despite their substantial impact, little is known about how well PSHA predicts actual shaking. Recent PSHA for California, Japan, Italy, Nepal, and France appear to consistently overpredict historically observed earthquake shaking intensities. Numerical simulations show that observed shaking is equally likely to be above or below predictions. This result from independently developed models and datasets in different countries and tectonic settings indicates possible systematic bias in the hazard models, the observations, or both. Analysis of possible causes shows that much of the discrepancy is due to a subtle and rarely considered issue: the conversion equations used in comparing the models—which forecast shaking as peak ground acceleration or velocity—and observations—parameterizations of qualitative shaking reports. Historical shaking reports fill a crucial data gap, but more research is warranted on how qualitative observations relate to instrumental shaking measures for earthquakes.

Copyright and License

© 2024 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution License 4.0 (CC BY).

Acknowledgement

We thank the reviewers of this paper for helpful feedback and M. Petersen and A. Llenos for helpful discussions.

Funding

This work was supported in part by the Institute for Policy Research at Northwestern University and the Pacific Gas and Electric Geosciences Department Long-Term Seismic Program. L.S. was supported by the U.S. Geological Survey Mendenhall Postdoctoral Fellowship program.

Contributions

Conceptualization: L.S., S.S., S.E.H., M.M.G., and J.S.N. Methodology: L.S., S.S., S.E.H., M.M.G., N.A., and J.S.N. Software: L.S. Validation: L.S., M.M.G., and J.S.N. Formal analysis: L.S., M.M.G., and J.S.N. Investigation: L.S. and M.M.G. Resources: L.S. and S.E.H. Data curation: L.S. and M.M.G. Writing—original draft: L.S. and S.S. Writing—review and editing: L.S., S.S., S.E.H., M.M.G., and J.S.N. Visualization: L.S. and M.M.G. Supervision: L.S., S.S., and S.E.H. Project administration: L.S. and S.S. Funding acquisition: L.S.

Data Availability

All data needed to evaluate the conclusions in the paper are present in the paper and the following sources: DBMI15v2 Italian macroseismic data are from M. Locati, R. Camassi, A. Rovida, E. Ercolani, F. Bernardini, V. Castelli, C. H. Caracciolo, A. Tertulliani, A. Rossi, R. Azzaro, S. D’Amico, and A. Antonucci. (2019); Database Macrosismico Italiano version 2 (DBMI15v2) [Dataset]; Istituto Nazionale di Geofisica e Vulcanologia (INGV); https://doi.org/10.13127/dbmi/dbmi15.2. Last accessed 17 May 2023. ESHM20 Italian hazard map is from L. Danciu, S. Nandan, C. Reyes, R. Basili, G. Weatherill, C. Beauval, A. Rovida, S. Vilanova, K. Sesetyan, P. Y. Bard, F. Cotton, S. Wiemer, D. Giardini. (2021)—The 2020 update of the European Seismic Hazard Model: Model Overview. EFEHR Technical Report 001, v1.0.0, https://doi.org/10.12686/a15 and http://hazard.efehr.org/en/hazard-data-access/hazard-maps/.

Conflict of Interest

The authors declare that they have no competing interests.

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Funding

Northwestern University
United States Geological Survey
Mendenhall Fellowship