Strategies for Comparison of Modern Probabilistic Seismic Hazard Models and Insights from the Germany and France Border Region

Weatherill, Graeme; Cotton, Fabrice; Daniel, Guillaume; Zentner, Irmela; Iturrieta, Pablo; Bosse, Christian

doi:https://doi.org/10.5194/nhess-2023-98

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https://doi.org/10.5194/nhess-2023-98

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07 Nov 2023

| 07 Nov 2023

Status: this preprint is currently under review for the journal NHESS.

Strategies for Comparison of Modern Probabilistic Seismic Hazard Models and Insights from the Germany and France Border Region

Graeme Weatherill, Fabrice Cotton, Guillaume Daniel, Irmela Zentner, Pablo Iturrieta, and Christian Bosse

Abstract. The latest generation of national and regional probabilistic seismic hazard assessments (PSHA) in Europe presents stakeholders with multiple representations of the hazard in many regions. This raises the question of why and by how much seismic hazard estimates between two or more models differ, not where models overlap geographically but also where new models update existing ones. As modern PSHA incorporates increasingly complex analysis of epistemic uncertainty, the resulting hazard is represented not as a single value or spectrum but rather as probability distribution. Focusing on recent PSHA models for France and Germany, alongside the 2020 European Seismic Hazard Model, we explore the differences in model components and highlight the challenges and strategy for harmonising the different models into a common PSHA calculation software. We then quantify the differences in the source model and seismic hazard probability distributions using metrics based on information theory, illustrating their application to Upper Rhine Graben region. Our analyses reveal the spatial variation and complexity of model differences when viewed as probability distributions and highlight the need for more detailed transparency and replicability of the models when used as a basis for decision making and engineering design.

Received: 16 Jun 2023 – Discussion started: 07 Nov 2023

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Graeme Weatherill, Fabrice Cotton, Guillaume Daniel, Irmela Zentner, Pablo Iturrieta, and Christian Bosse

Status: final response (author comments only)

RC1:
'Comment on nhess-2023-98', Peter Powers, 12 Dec 2023
Weatherill et al., do an excellent job of presenting side by side comparison of three Central European hazard models and their manuscript is extremely well written; a real pleasure to read. This type of comparison of complex PSHAs has not received the attention it deserves in light of rapidly evolving modeling methodologies.
Main comments:
The authors do not mention declustering implying that the rates (GR 'a-values) for zones and gridded seismicity are total catalog rates. I'm not up to speed on the state of PSHA practice in the EU, but we've only just moved away from using decluttered catalog rates (and the 2023 models that do-so are quite a few years out from becoming policy). At a minimum, I think what the rates represent bears mentioning (and I apologize if I missed it).

In discussing GMMs, clarify what you're doing to compute mean sigma. Square-root-sum-of-squares SSRS? I think you refer to the 'median' for the ground motion implying the mean in carious plots is the weighted average of the medians, not the natural log means.

I don't think any change is necessary (because the conclusions of the paper will not be affected) but it is hard to compare three models. Difference and ratio maps are hard to digest when the subtrahend or denominator change. For future reference maybe consider holding ESHA20 (being the 'regional' model) fixed as the denominator and possibly making it easier to see how different the country models are relative to the regional one.

On line 553, what do you mean by the ERF approach? OpenSHA has a class/interface called ERF but its contract is pretty limited in scope and ruptures representing almost anything can be programmatically created to meet the needs of a model. Do you perhaps mean the inversion methodology applied in UCERF3, the 2014 USGS NSHM for the Conterminous U.S.? If yes, then I'd cite Field et al. (2015) instead:

Field EH, Biasi GP, Bird P, Dawson TE, Felzer KR, Jackson DD, Johnson KM, Jordan TH, Madden C, Michael AJ, Milner KR, Page MT, Parsons T, Powers PM, Shaw BE, Thatcher WR, Weldon RJ II and Zeng Y (2015) Long-term time-dependent probabilities for the third uniform California earthquake rupture forecast (UCERF3). Bulletin of the Seismological Society of America 105(2a): 511–543, https://doi.org/10.1785/0120140093.

Editorial comments:
Line 23 'of the earthquake process' or 'of earthquake processes'

Line 30 ...understanding of physical phenomena...

Line 52 (CEN, 2004) not in references

Line 53 ... components of seismicity design...

Line 60 'though' suggests a shortcoming... is it that the national models are using a now outdated regional model?

Line 101 Manchuel et al. 2017? year is 2018 in refs

Line 108 ...and was prepared

Line 130 ...logic trees are shown for FR202, DE2016, and ESHM20 in Figures 1, 2, and 3, respectively.

Table 1 Cauzzi et al. (2014) ref in lower center cell doesn't exist. 2015?

Line 165 ...B are LASZ predicated on the assumption that regional-scale tectonics ...

Line 169 ...and ESHM20; DE2016 uses...

Line 211 ...models arrive a... should be 'at

Line 269 'our' attention instead of 'the'

Line 300 Kagan misspelled

Line 365 Nandan?

Line 375 ESHM20 'has'? Instead of 'finds'?

Line 376 'yields' instead of 'returns'?

Line 489 ...were the attenuation parameters 'of the' backbone GMM...?

Line 539 (Pagani et al., 2014) 'a' | 'b' needed or second ref removed from references.

Line 552 Cornell (1968) year is 1978 in refs

Line 555 Assatorians & Atkinson, 2014 missing from refs

Line 793 information 'theory'? I think as a discipline I don't think it should be modified to describe metrics

Line 971 (US NRC, 2018) not in references.... we use the following for citing the SSHAC procedure:

Budnitz RJ, Apostolakis G, Boore DM, et al. (1997) Recommendations for probabilistic seismic hazard analysis: Guidance on uncertainty and use of experts. Report no. NUREG/CR-6372. Washington, DC: U.S. Nuclear Regulatory Commission, 280 pp.

Line 1105 year is missing from Meletti reference

Reference list issues:
Bommer and Akkar (2012) not referenced.

Bommer and Montaldo Falero (2020) not referenced.

GEOTER (or Fugro and rearrange reference) (2017) is mentioned but not referenced with a year.

Goulet et al. (2021) not referenced.

Monelli et al. (2014) not referenced.

Pagani et al. (2014a/b) not explicitly referenced in text, only Pagani et al. (2014).

Scherbaum et al. (2004) not referenced.

Vilanova et al. (2014) not referenced.

Weatherill and Cotton (2020) not referenced.
Citation: https://doi.org/10.5194/nhess-2023-98-RC1
- AC1:
  'Reply on RC1', Graeme Weatherill, 29 Feb 2024
  We thank the reviewer for their thorough review of the manuscript and their constructive feedback that we believe has helped identify some minor shortcomings. We have attempted to address their comments appropriately and have fixed the editorial issues identified. Below we respond to the main comments in-line, with the reviewer’s original comments posted in italic text and our reply in normal text.
  Main comments:
  The authors do not mention declustering implying that the rates (GR 'a-values) for zones and gridded seismicity are total catalog rates. I'm not up to speed on the state of PSHA practice in the EU, but we've only just moved away from using decluttered catalog rates (and the 2023 models that do-so are quite a few years out from becoming policy). At a minimum, I think what the rates represent bears mentioning (and I apologize if I missed it)
  
  The omission of discussion regarding declustering is an oversight on our part, which we thank the reviewer for highlighting. Declustering is still current practice in Europe, and each of the three models applies it prior to constraining the activity rates; thus the activity rates reflect the rate of mainshocks. A new paragraph describing this comparison is added at the beginning of section 2.2, where we compare the calculation of the magnitude frequency relations.
  In discussing GMMs, clarify what you're doing to compute mean sigma. Square-root-sum-of-squares SSRS? I think you refer to the 'median' for the ground motion implying the mean in carious plots is the weighted average of the medians, not the natural log means.
  
  We appreciate the reviewer pointing out this unclear description in the figures (Figures 6 – 7). To compute the “Mean” labelled in the Figure 6, we take the sum of the median ground motions (μ_i) from each model i in the logic tree, weighted by their corresponding weights in the logic tree (w_i), i.e. Mean=∑_i(μ_i ⋅ w_i). Likewise, for the “Mean” aleatory variability in Figure 7, Mean=∑_i(σ_i ⋅w_i ). This has now been made explicit in the captions.
  I don't think any change is necessary (because the conclusions of the paper will not be affected) but it is hard to compare three models. Difference and ratio maps are hard to digest when the subtrahend or denominator change. For future reference maybe consider holding ESHA20 (being the 'regional' model) fixed as the denominator and possibly making it easier to see how different the country models are relative to the regional one.
  
  We understand the reviewer’s point here and agree that this may be preferable for presentation. However, this particular form of presentation in the paper is deliberately selected to avoid indicating any of the specific models as a “reference”, even if it is just for the purposes of comparisons in the figures. Of course, if one wished to undertake such comparisons in practice, we would recommend the approach the reviewer suggests. A sentence is added here to clarify our motivation for this particular style of presentation of these comparisons.
  On line 553, what do you mean by the ERF approach? OpenSHA has a class/interface called ERF but its contract is pretty limited in scope and ruptures representing almost anything can be programmatically created to meet the needs of a model. Do you perhaps mean the inversion methodology applied in UCERF3, the 2014 USGS NSHM for the Conterminous U.S.? If yes, then I'd cite Field et al. (2015) instead:
  
  Field EH, Biasi GP, Bird P, Dawson TE, Felzer KR, Jackson DD, Johnson KM, Jordan TH, Madden C, Michael AJ, Milner KR, Page MT, Parsons T, Powers PM, Shaw BE, Thatcher WR, Weldon RJ II and Zeng Y (2015) Long-term time-dependent probabilities for the third uniform California earthquake rupture forecast (UCERF3). Bulletin of the Seismological Society of America 105(2a): 511–543, https://doi.org/10.1785/0120140093.
  The reviewer is correct that what we are referring to here is the outcome of the inversion methodology for fault system modelling that was pioneered in the UCERF3 project. This sentence has been revised to clarify this and the citation to Field et al. (2015) added.
  Editorial comments:
  All the editorial comments have been addressed and changes implemented (see inline notes below for specific issues). We thank the reviewer for their thorough reading of the manuscript.
  Line 793 information 'theory'? I think as a discipline I don't think it should be modified to describe metrics
  
  We have modified this to describe the metrics as “non-parametric measures based on information theory”.
  Line 971 (US NRC, 2018) not in references.... we use the following for citing the SSHAC procedure:
  
  Budnitz RJ, Apostolakis G, Boore DM, et al. (1997) Recommendations for probabilistic seismic hazard analysis: Guidance on uncertainty and use of experts. Report no. NUREG/CR-6372. Washington, DC: U.S. Nuclear Regulatory Commission, 280 pp.
  We thank the reviewer for clarifying the reference. We have added the bibliography entry for the SSHAC update document mentioned, which is now cited as Ake et al. (2018).
  Reference list issues:
  All the unused references have been removed from the bibliography.
  
  Citation: https://doi.org/10.5194/nhess-2023-98-AC1
RC2:
'Comment on nhess-2023-98', Anonymous Referee #2, 26 Jan 2024

The manuscript entitled "Strategies for Comparison of Modern Probabilistic Seismic Hazard Models and Insights from the Germany and France Border Region" represents a sound comparison between three different European PSH models, focusing on low-to-moderate seismicity regions spanning across France and Germany. The effort in harmonizing the three models (one for France, one for Germany and one for Europe) is remarkable and well presented.

Citation: https://doi.org/10.5194/nhess-2023-98-RC2
- AC2: 'Reply on RC2', Graeme Weatherill, 29 Feb 2024
  
  We thank the reviewer for their positive assessment of the manuscript.
  
  Citation: https://doi.org/10.5194/nhess-2023-98-AC2
RC3:
'Comment on nhess-2023-98', Anonymous Referee #3, 16 Feb 2024

In this email, you can find the revision for nhess-2023-98 research article attached.
I evaluated the paper as an interesting and well-presented one and shared my favorable opinion for this research to be published with some minor comments/edits (attached).

Citation: https://doi.org/10.5194/nhess-2023-98-RC3
- AC3:
  'Reply on RC3', Graeme Weatherill, 29 Feb 2024
  We thank the reviewers for their positive assessment of the manuscript. We have endeavoured to take into account their suggestions to improve the manuscript and provide our replies to the comments in-line below. The original comments of the reviewer are given in italic, while our replies are seen in normal text.
  Some comments about the work are listed below:
  Other seismic hazard models in globe should be mentioned in “Introduction” with a comment on the similarities and differences with Central European Hazard models.
  
  We appreciate the reviewer’s suggestion and understand that there may be some benefit for readers interested in understanding seismic hazard practice across the globe to gain perspective on how these Central European seismic hazard models compare. Even a cursory comparison would require a considerable expansion of the introductory section of this paper, and a more substantial treatment of similarities/differences would be a separate publication in itself. Given the focus of both the manuscript and the special issue of the journal to which it is intended for publication is on “Harmonised Seismic Hazard and Risk Assessment for Europe”, we believe that it would be better to keep the context more limited to discussing similarities and differences with respect to European models. For a more global perspective we would refer the reader to the Global Seismic Hazard Model of Pagani et al. (2020) (already cited in the introduction) and the interesting discussion paper of Gerstenberger et al. (2020) who look at the current state-of-the-art and at future challenges in regional and national PSHA models, particularly comparing different models from across the globe. The Gerstenberger et al (2020) reference is now added to the introduction.
  A preliminary paragraph can be presented with more detail for the reason in selecting these three models and the region.
  
  In the revised manuscript we have added further sentences to the introduction to explain in more detail the reasons for selecting these models and case study region.
  Other models from Greece, Portugal, Spain beside ESHM13 (in Lines 49-51) may be commented.
  
  We acknowledge the point that the author has made and note that there have been efforts in many other countries to update their seismic hazard maps since ESHM13 too, not just those listed here. A longer list can be found in the paper of Danciu et al (2024) in this issue of NHESS. We have added the case of Spain to the list mentioned in the current manuscript, which follows on from the update by Instituto Geográfico Nacional in 2017 (now cited). For Portugal and Greece we are not aware of specific national scale models being developed between ESHM13 and ESHM20 (though we are happy to be corrected here). However, we do know that following ESHM13, new efforts in these countries were initiated to expand and improve collections of geological and geophysical data that will be relevant for future seismic hazard models in these countries. Some of this data we were able to integrate into ESHM20. We have expanded this paragraph by a couple of sentences to reflect this.
  Gutenberg, B. and Richter, C.F. (1944), may be referred as the base for understanding seismicity rates, which is a fundamental component of probabilistic seismic hazard analysis.
  
  Reference to the original publication of Gutenberg & Richter (1944) is now added.
  Basilic et al., 2013. (The European Database of Seismogenic Faults (EDSF) compiled in the framework of the Project SHARE https://seismofaults.eu/edsf13) may be commented/referred.
  
  We take the reviewer’s point that reference is needed to the European Database of Seismic Faults. We have added in now the reference to the updated database that was used for the ESHM20, published as Basili et al. (2023) in this same special issue of NHESS. https://nhess.copernicus.org/preprints/nhess-2023-118/.
  “Considerable degree of divergence in the tectonic zonations” should be explained commented in Line 261.
  
  Clarification of the meaning of “degree of divergence” is now added to this sentence. The exact differences in the tectonic interpretations can be found in the sentences that follow.
  Discussions on using the complete logic tree with differences in France and Germany should take place.
  
  We are keen to address the reviewer’s comment here, but unfortunately we have not understood where in the paper the shortcomings relating to this comment are to be found and what aspect of the topic we should address in detail. Differences in the logic trees in France and Germany and their implications for usage are addressed in detail throughout the paper. If possible, we would kindly ask if the reviewer could provide further clarification to help us resolve this issue to their satisfaction.
  Line 200: … is not quite so clear…
  
  Now edited to “… is not as clear and intentional as …”
  Line 552: The fundamental framework for PSHA is largely unchanged changed?
  
  Now fixed
  
  Citation: https://doi.org/10.5194/nhess-2023-98-AC3
RC4: 'Comment on nhess-2023-98', Ilaria Mosca, 14 Mar 2024

My comments are included in the PDF file.

Citation: https://doi.org/10.5194/nhess-2023-98-RC4

Graeme Weatherill, Fabrice Cotton, Guillaume Daniel, Irmela Zentner, Pablo Iturrieta, and Christian Bosse

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https://doi.org/10.5194/nhess-2023-98-supplement

Graeme Weatherill, Fabrice Cotton, Guillaume Daniel, Irmela Zentner, Pablo Iturrieta, and Christian Bosse

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Short summary

New generations of seismic hazard models are developed with sophisticated approaches to quantify uncertainties in our knowledge of earthquake process. To understand why and how recent state-of-the-art seismic hazard models for France, Germany and Europe differ despite similar underlying assumptions, we present a systematic approach to investigate model-to-model differences and to quantify and visualise them while accounting for their respective uncertainties.


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