MILQ: A liquefaction triggering map for Italy

Barani, Simone; Ferretti, Gabriele; Scafidi, Davide

doi:https://doi.org/10.5194/egusphere-2022-1139

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https://doi.org/10.5194/egusphere-2022-1139

Preprints

24 Oct 2022

| 24 Oct 2022

MILQ: A liquefaction triggering map for Italy

Simone Barani, Gabriele Ferretti, and Davide Scafidi

Abstract. In the present study, we analyze ground-motion hazard maps and hazard disaggregation in order to define areas in Italy where liquefaction triggering due to seismic activity can not be excluded. To this end, we refer to the triggering criteria proposed by the Italian Guidelines for Seismic Microzonation, which are described in the main body of the manuscript. However, the study can be replicated in other countries that adopt different criteria. The final goal is the definition of a screening map for all of Italy that classifies sites in terms of liquefaction triggering potential according to their seismic hazard level. The map, which is referred with the Italian acronym MILQ (Mappa del potenziale d’Innesco della LiQuefazione), and the associated data are freely accessible at the following web address: www.distav.unige.it/rsni/milq.php. Our results can be useful to guide land-use planners in deciding whether liquefaction is a hazard that needs to be considered within the planning processes or not. Furthermore, they can serve as a guide for recommending geological and geotechnical investigations aimed at the evaluation of liquefaction hazards or, conversely, rule out further studies with a consequent saving in efforts and money.

Received: 21 Oct 2022 – Discussion started: 24 Oct 2022

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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.

Journal article(s) based on this preprint

03 May 2023

| Highlight paper

Evaluation of liquefaction triggering potential in Italy: a seismic-hazard-based approach

Simone Barani, Gabriele Ferretti, and Davide Scafidi

Nat. Hazards Earth Syst. Sci., 23, 1685–1698, https://doi.org/10.5194/nhess-23-1685-2023,https://doi.org/10.5194/nhess-23-1685-2023, 2023

Short summary Executive editor

Simone Barani et al.

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2022-1139', Anonymous Referee #1, 03 Dec 2022
General comment: the paper deals with an interesting topic (a liquefaction triggering map for Italy) and is generally well written. I think that the paper is important from a technical point of view. Further comments are reported below:

It could be useful to define liquefaction induced by earthquakes.

I suggest adding further information regarding liquefaction phenomena in Italy.

Line 63. “Lime” should be replaced by “silt”.

Line 99. S_S should be defined as the “soil stratigraphy amplification factor”. “Stratigraphy” should be added.

Line 107. I think that Fig. 1 is interesting and should be better commented. For example, further considerations could be done on the fact that the highest values of SS are in Emilia Romagna where liquefaction occurred in 2012.

Line 116. M must be defined too.

Line 135. Maybe “di” should be replaced by “of”.
Citation: https://doi.org/10.5194/egusphere-2022-1139-RC1
- AC1: 'Reply on RC1', Simone Barani, 09 Mar 2023
  
  First of all, we thak the reviewer for his helpful suggestions and comments, which resulted in an improvement of the manuscript. Our replies (in red) to the comments are in the file attached.
  
  Citation: https://doi.org/10.5194/egusphere-2022-1139-AC1
RC2:
'Comment on egusphere-2022-1139', Anonymous Referee #2, 31 Jan 2023
GENERAL COMMENTS
The proposed manuscript presents a map of Italy where regions with different seismic intensity levels able to trigger (or not) earthquake-induced liquefaction are distinguished for a return period of 475 years. The study has a good scientific significance, where the substantial contribution and main novelty can be detected in the innovative criteria to select the moment magnitude to use for assessing the soil liquefaction potential according to the simplified approach.
The technical approach and the applied methods are valid, i.e., the scientific quality is good. The presentation quality is generally fair, but the technical and English language needs to be improved as detailed in the ‘technical corrections’.
Even though the paper addresses relevant questions within the scope of NHESS, I raised some critical issues that require major revisions before publication, as listed in the following:

SPECIFIC COMMENTS
The Authors correctly said that if the seismic hazard at a specific site is too low, the liquefaction does not need to be considered in the planning process. Conversely, the opposite situation (i.e., high seismic hazard) is necessary but not enough to trigger liquefaction phenomena. Indeed, earthquake-induced liquefaction occurs only if the triggering (earthquakes) and predisposing factors (loose saturated granular soils) coexist contemporarily. For the above reason, I think that the title of the paper is misleading because it seems that the proposed map shows the areas where there is the occurrence of liquefaction. This is not true because liquefaction is going to happen only where susceptible soils to liquefaction are encountered. Consequently, I suggest a much more robust description of the title and the map, such as an example: ‘Screening map for earthquake-induced liquefaction based on the existence of triggering factors’ that in Italian would be ‘Mappa di selezione delle aree in cui sussistono fattori scatenanti della liquefazione sismo-indotta’. Please, revise the manuscript accordingly.

The Authors correctly stated in the conclusions that site-specific analyses can allow the refinement of the maximum acceleration, and that subsoil and topographic class can be changed through a user-friendly interface. However, it can be appropriate to highlight that a seismic response analysis to assess the local effects is mandatory when the considered site cannot be categorized in one of the subsoil classes according to the national building code (section 3.2.2, Ministero delle Infrastrutture e dei Trasporti, 2018).

Putting the acronym in the title is probably not the best solution because it is not informative. It can be explained in the subsequent part of the paper.

The Italian acronym is described in Italian, it is suggested to also report the English translation to be much clearer and to be in line with international standards.

The Author said in the abstract that they refer to the triggering criteria proposed by the Italian Guidelines for Seismic Microzonation, but nothing is said about the predisposing factors (type of soil, shallow ground water table). I suggest that the Authors immediately clarify in the Abstract if the predisposing factors are considered or not in the definition of the map.

TECHNICAL CORRECTIONS
First line of the Introduction. ‘potential liquefaction hazards’ is redundant. I suggest ‘potential liquefaction’ or ‘liquefaction hazard’ which are both standalone.

First line of the Introduction. ‘site’ is repeated two times in both (1) and (2) questions. I suggest being concise and anticipating ‘at the site of interest’ before ‘always’. In this way, the two questions are becoming brief and more effective without ‘at the site of interest’ in question (1) and ‘at that site’ in question (2), respectively.

Second line of the Introduction. ‘favorable’ could be better substituted with ‘prone’.

Second line of the Introduction. ‘ground motions’ is redundant and can be removed. ‘Earthquakes’ should be instead of ‘earthquake’.

Line 9 of the Introduction (section 25 of the pdf file). A bracket is open after ‘surface’ but it is not closed anymore. Please, correct this.

First line of section 30 of the pdf file. ‘site hazard’ should be ‘seismic hazard’ otherwise it is unknown what kind of hazard the Authors refer to.

Line 4 of section 45 of the pdf file. What do the Authors mean by ‘1D magnitude’?

Line 2 of section 50 of the pdf file. The year of the reference ‘Italian Guidelines for Seismic Microzonation’ needs to be added.

Chapter 2. Criteria for liquefaction triggering. Line 3. ‘limes’ and ‘limey’ should be substituted with ‘silts’ and ‘silty’, respectively.

Chapter 3.1 Seismic hazard map. Line 5 of section 100 of the pdf file. ‘ground types’ should be ‘soil types’ or ‘subsoil class’. Please, revise is in the entire manuscript.

Chapter 3.2 Hazard disaggregation. Line before section 130 of the pdf file. The statement ‘We expect that decreasing 𝑉S,eq and/or increasing soil thickness the site resonance period increases.’ is due to the definition of the natural period of a homogenous deformable soil deposit overlying a half-space. Please, add the reference for this, e.g., Kramer (1996).

Line section 135 of the pdf file. ‘di’ after control needs to be deleted.

Chapter 6. Discussion. Line 2 of section 220 of the pdf file. ‘with red dots indicating the sites where liquefaction triggering is expected to occur’ the dots looks blue and light blue and are used to define past liquefaction events. Please, revise.

MENTIONED AND SUGGESTED REFERENCES
Ministero delle Infrastrutture e dei Trasporti. Aggiornamento delle “Norme tecniche per le costruzioni”, D.M. 17 Gennaio 2018, Supplemento ordinario alla Gazzetta Ufficiale N. 42 del 20 Febbraio, 2018.
Kramer S.L. ‘Geotechnical Earthquake Engineering’ Prentice-Hall, Upper Saddle River, NJ 1996.
Citation: https://doi.org/10.5194/egusphere-2022-1139-RC2
- AC2: 'Reply on RC2', Simone Barani, 09 Mar 2023
  
  First of all, we thank the reviewer for his helpful suggestions and comments, which resulted in an improvement of the manuscript. Our replies (in red) to the comments are in the attached files.
  
  Citation: https://doi.org/10.5194/egusphere-2022-1139-AC2
AC3:
'Comment on egusphere-2022-1139', Simone Barani, 09 Mar 2023

Dear Editor,
it is not clear to us how to upload the revised version of the manuscript, so as you and the reviewers can read it.
Sincerely,
Simone Barani

Citation: https://doi.org/10.5194/egusphere-2022-1139-AC3
- EC1: 'Reply on AC3', Giovanni Forte, 10 Mar 2023
  
  Dear Simone,
  in this stage it was required to address the comments of the reviewers.
  The next step is upload the modified version.
  Best
  Giovanni
  
  Citation: https://doi.org/10.5194/egusphere-2022-1139-EC1

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2022-1139', Anonymous Referee #1, 03 Dec 2022
General comment: the paper deals with an interesting topic (a liquefaction triggering map for Italy) and is generally well written. I think that the paper is important from a technical point of view. Further comments are reported below:

It could be useful to define liquefaction induced by earthquakes.

I suggest adding further information regarding liquefaction phenomena in Italy.

Line 63. “Lime” should be replaced by “silt”.

Line 99. S_S should be defined as the “soil stratigraphy amplification factor”. “Stratigraphy” should be added.

Line 107. I think that Fig. 1 is interesting and should be better commented. For example, further considerations could be done on the fact that the highest values of SS are in Emilia Romagna where liquefaction occurred in 2012.

Line 116. M must be defined too.

Line 135. Maybe “di” should be replaced by “of”.
Citation: https://doi.org/10.5194/egusphere-2022-1139-RC1
- AC1: 'Reply on RC1', Simone Barani, 09 Mar 2023
  
  First of all, we thak the reviewer for his helpful suggestions and comments, which resulted in an improvement of the manuscript. Our replies (in red) to the comments are in the file attached.
  
  Citation: https://doi.org/10.5194/egusphere-2022-1139-AC1
RC2:
'Comment on egusphere-2022-1139', Anonymous Referee #2, 31 Jan 2023
GENERAL COMMENTS
The proposed manuscript presents a map of Italy where regions with different seismic intensity levels able to trigger (or not) earthquake-induced liquefaction are distinguished for a return period of 475 years. The study has a good scientific significance, where the substantial contribution and main novelty can be detected in the innovative criteria to select the moment magnitude to use for assessing the soil liquefaction potential according to the simplified approach.
The technical approach and the applied methods are valid, i.e., the scientific quality is good. The presentation quality is generally fair, but the technical and English language needs to be improved as detailed in the ‘technical corrections’.
Even though the paper addresses relevant questions within the scope of NHESS, I raised some critical issues that require major revisions before publication, as listed in the following:

SPECIFIC COMMENTS
The Authors correctly said that if the seismic hazard at a specific site is too low, the liquefaction does not need to be considered in the planning process. Conversely, the opposite situation (i.e., high seismic hazard) is necessary but not enough to trigger liquefaction phenomena. Indeed, earthquake-induced liquefaction occurs only if the triggering (earthquakes) and predisposing factors (loose saturated granular soils) coexist contemporarily. For the above reason, I think that the title of the paper is misleading because it seems that the proposed map shows the areas where there is the occurrence of liquefaction. This is not true because liquefaction is going to happen only where susceptible soils to liquefaction are encountered. Consequently, I suggest a much more robust description of the title and the map, such as an example: ‘Screening map for earthquake-induced liquefaction based on the existence of triggering factors’ that in Italian would be ‘Mappa di selezione delle aree in cui sussistono fattori scatenanti della liquefazione sismo-indotta’. Please, revise the manuscript accordingly.

The Authors correctly stated in the conclusions that site-specific analyses can allow the refinement of the maximum acceleration, and that subsoil and topographic class can be changed through a user-friendly interface. However, it can be appropriate to highlight that a seismic response analysis to assess the local effects is mandatory when the considered site cannot be categorized in one of the subsoil classes according to the national building code (section 3.2.2, Ministero delle Infrastrutture e dei Trasporti, 2018).

Putting the acronym in the title is probably not the best solution because it is not informative. It can be explained in the subsequent part of the paper.

The Italian acronym is described in Italian, it is suggested to also report the English translation to be much clearer and to be in line with international standards.

The Author said in the abstract that they refer to the triggering criteria proposed by the Italian Guidelines for Seismic Microzonation, but nothing is said about the predisposing factors (type of soil, shallow ground water table). I suggest that the Authors immediately clarify in the Abstract if the predisposing factors are considered or not in the definition of the map.

TECHNICAL CORRECTIONS
First line of the Introduction. ‘potential liquefaction hazards’ is redundant. I suggest ‘potential liquefaction’ or ‘liquefaction hazard’ which are both standalone.

First line of the Introduction. ‘site’ is repeated two times in both (1) and (2) questions. I suggest being concise and anticipating ‘at the site of interest’ before ‘always’. In this way, the two questions are becoming brief and more effective without ‘at the site of interest’ in question (1) and ‘at that site’ in question (2), respectively.

Second line of the Introduction. ‘favorable’ could be better substituted with ‘prone’.

Second line of the Introduction. ‘ground motions’ is redundant and can be removed. ‘Earthquakes’ should be instead of ‘earthquake’.

Line 9 of the Introduction (section 25 of the pdf file). A bracket is open after ‘surface’ but it is not closed anymore. Please, correct this.

First line of section 30 of the pdf file. ‘site hazard’ should be ‘seismic hazard’ otherwise it is unknown what kind of hazard the Authors refer to.

Line 4 of section 45 of the pdf file. What do the Authors mean by ‘1D magnitude’?

Line 2 of section 50 of the pdf file. The year of the reference ‘Italian Guidelines for Seismic Microzonation’ needs to be added.

Chapter 2. Criteria for liquefaction triggering. Line 3. ‘limes’ and ‘limey’ should be substituted with ‘silts’ and ‘silty’, respectively.

Chapter 3.1 Seismic hazard map. Line 5 of section 100 of the pdf file. ‘ground types’ should be ‘soil types’ or ‘subsoil class’. Please, revise is in the entire manuscript.

Chapter 3.2 Hazard disaggregation. Line before section 130 of the pdf file. The statement ‘We expect that decreasing 𝑉S,eq and/or increasing soil thickness the site resonance period increases.’ is due to the definition of the natural period of a homogenous deformable soil deposit overlying a half-space. Please, add the reference for this, e.g., Kramer (1996).

Line section 135 of the pdf file. ‘di’ after control needs to be deleted.

Chapter 6. Discussion. Line 2 of section 220 of the pdf file. ‘with red dots indicating the sites where liquefaction triggering is expected to occur’ the dots looks blue and light blue and are used to define past liquefaction events. Please, revise.

MENTIONED AND SUGGESTED REFERENCES
Ministero delle Infrastrutture e dei Trasporti. Aggiornamento delle “Norme tecniche per le costruzioni”, D.M. 17 Gennaio 2018, Supplemento ordinario alla Gazzetta Ufficiale N. 42 del 20 Febbraio, 2018.
Kramer S.L. ‘Geotechnical Earthquake Engineering’ Prentice-Hall, Upper Saddle River, NJ 1996.
Citation: https://doi.org/10.5194/egusphere-2022-1139-RC2
- AC2: 'Reply on RC2', Simone Barani, 09 Mar 2023
  
  First of all, we thank the reviewer for his helpful suggestions and comments, which resulted in an improvement of the manuscript. Our replies (in red) to the comments are in the attached files.
  
  Citation: https://doi.org/10.5194/egusphere-2022-1139-AC2
AC3:
'Comment on egusphere-2022-1139', Simone Barani, 09 Mar 2023

Dear Editor,
it is not clear to us how to upload the revised version of the manuscript, so as you and the reviewers can read it.
Sincerely,
Simone Barani

Citation: https://doi.org/10.5194/egusphere-2022-1139-AC3
- EC1: 'Reply on AC3', Giovanni Forte, 10 Mar 2023
  
  Dear Simone,
  in this stage it was required to address the comments of the reviewers.
  The next step is upload the modified version.
  Best
  Giovanni
  
  Citation: https://doi.org/10.5194/egusphere-2022-1139-EC1

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload

ED: Publish subject to minor revisions (review by editor) (10 Mar 2023) by Giovanni Forte

AR by Simone Barani on behalf of the Authors (10 Mar 2023) Author's response Author's tracked changes Manuscript

ED: Publish as is (10 Mar 2023) by Giovanni Forte

AR by Simone Barani on behalf of the Authors (06 Apr 2023)

Journal article(s) based on this preprint

03 May 2023

| Highlight paper

Evaluation of liquefaction triggering potential in Italy: a seismic-hazard-based approach

Simone Barani, Gabriele Ferretti, and Davide Scafidi

Nat. Hazards Earth Syst. Sci., 23, 1685–1698, https://doi.org/10.5194/nhess-23-1685-2023,https://doi.org/10.5194/nhess-23-1685-2023, 2023

Short summary Executive editor

Simone Barani et al.

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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.

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Metadata XML

This paper produces a map for all of Italy that classifies different regions in terms of liquefaction triggering potential according to their seismic hazard level. The map MILQ (Mappa del potenziale d’Innesco della LiQuefazione), and the associated data are freely accessible at: www.distav.unige.it/rsni/milq.php. The results can be useful to guide land-use planners in deciding whether liquefaction is a hazard that needs to be considered within the planning processes or not. Furthermore, they can serve as a guide for recommending geological and geotechnical investigations aimed at evaluating liquefaction hazards or, conversely, rule out further studies with a consequent saving in efforts and money.

Short summary

In the present study, we analyze ground-motion hazard maps and hazard disaggregation in order to define areas in Italy where liquefaction triggering due to seismic activity can not be excluded. The final results is a screening map for all of Italy that classifies sites in terms of liquefaction triggering potential according to their seismic hazard level. The map and the associated data are freely accessible at the following web address: www.distav.unige.it/rsni/milq.php.


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