Probabilistic Fault Displacement Hazard Analysis for North Tabriz Fault

Hosseyni, Mohamadreza; Rahimi, Habib

doi:https://doi.org/10.5194/nhess-2021-351

Preprints

https://doi.org/10.5194/nhess-2021-351

Preprints

07 Dec 2021

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

Probabilistic Fault Displacement Hazard Analysis for North Tabriz Fault

Mohamadreza Hosseyni¹ and Habib Rahimi² Mohamadreza Hosseyni and Habib Rahimi Mohamadreza Hosseyni¹ and Habib Rahimi²

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¹M.Sc. Graduated, Department of Earth Physics, Institute of Geophysics, University of Tehran, Tehran, Iran
²Associate Professor, Department of Earth Physics, Institute of Geophysics, University of Tehran, Tehran, Iran

Received: 19 Nov 2021 – Discussion started: 07 Dec 2021

Abstract. The probabilistic fault displacement hazard analysis is one of the new methods in estimating the amount of possible displacement in the area at the hazard of causal fault rupture. In this study, using the probabilistic approach and earthquake method introduced by Youngs et al., 2003, the surface displacement of the North Tabriz fault has been investigated, and the possible displacement in different scenarios has been estimated. By considering the strike-slip mechanism of the North Tabriz fault and using the earthquake method, the probability of displacement due to surface ruptures caused by 1721 and 1780 North Tabriz fault earthquakes has been explored. These events were associated with 50 and 60 km of surface rupture, respectively. The 50–60 km long section of the North Tabriz fault was selected as the source of possible surface rupture.

We considered two scenarios according to possible displacements, return periods, and magnitudes which are reported in paleoseismic studies of the North Tabriz fault. As the first scenario, possible displacement, return period, and magnitude was selected between zero to 4.5; 645 years and Mw~7.7, respectively. In the second scenario, possible displacement, return period and magnitude were selected between zero to 7.1, 300 years, and Mw~7.3, respectively. For both mentioned scenarios, the probabilistic displacements for the rate of exceedance 5 % in 50, 475, and 2475 years for the principle possible displacements (on fault) of the North Tabriz fault have been estimated. For the first and second scenarios, the maximum probabilistic displacement of the North Tabriz fault at a rate of 5 % in 50 years is estimated to be 186 and 230 cm. Also, mentioned displacements for 5 % exceedance in 475 years and 2475 years in both return periods of 645 and 300 years, are estimated at 469 and 655 cm.

Mohamadreza Hosseyni and Habib Rahimi

Status: final response (author comments only)

RC1:
'Comment on nhess-2021-351', R. E. S. Moss, 11 Jan 2022

I found this manuscript to be well written and the study well executed. I only have two comments.

1. All figures need to be revised so that they are legible from a publication perspective. The inset text, colored zones, legends, and font size all need to be improved to make the figures more readable.

2. I would be interested to hear the authors opinion on an appropriate hazard level (e.g., 975 yr return) that should be used for surface fault displacement. This is an area of ambiguity where there is currenlty no concensus. Since this study looks at many hazard levels, which would correspond to the type of construction of infrastructure in and around Tabriz?

Citation: https://doi.org/10.5194/nhess-2021-351-RC1
- AC1: 'Reply on RC1', Habib Rahimi, 18 Jan 2022
  
  Thanks for taking the time to read the manuscript.
  Regarding the quality of the figures as well as the writings inside them, these figures must be edited and the quality will be improved in the text of the revised version. Of course, due to the file being converted to PDF and uploaded to the site, the resolution of the figures has dropped a bit.
  Regarding the return period, as you mentioned, there is no consensus in this regard in the different studies, and for this reason, we have considered various return periods for this purpose. In the Tabriz region, due to the existence of urban buildings in the study area, a return period of 475 years can be used. Also, for higher importance structures such as petrochemicals and refineries in the study area, higher returns periods can be considered.
  
  Citation: https://doi.org/10.5194/nhess-2021-351-AC1
RC2:
'Comment on nhess-2021-351', Anonymous Referee #2, 27 Jan 2022

The main aim of this paper is to evaluate the probabilistic on-fault displacement hazard analysis for the North Tabriz Fault. The authors consider two different scenarios, based on two different published paleoseismological studies, and apply the Petersen et al. 2011 approach, due to the strike-slip kinematic of the considered fault. The study is interesting because there are very few examples of PFDHA and its application worldwide, but before to consider it as publication, in my opinion a major review is necessary.

These general comments must be addressed:

1) The introduction is missing of several worth-to-mention papers and should be improved accordingly.

2) The input data must be clearly descibed both in the main text and in the figure. Fault length and selected site are just two examples.

3) The section Methodology of probabilistic fault displacement hazard analysis needs a deep reveiew. I suggest to focus only on the approach used (i.e., Petersen at al.) and I would like to see all equations used ( and how).

4) The section Results and Discussions is very poor. There is no discussion about the results and, for me, it has been very hard to understand how input parameters are considered and which equations are used. This paper could help the seismic hazard local community but it need a major review in order to make the manuscript clear and readble. Reading the paper I have the feeling that most of things are omitted and not well described.

5) As it is, this work is just an application of an already published work (Petersen et al., 2011). Which is the contribute to the scientific community ? even if the authors are in position that they cannot contribute from a methodological point of view, a good discussion section can help to improve the quality of the manuscript, for example, highlighting the critical aspects of this approach, the difficulties that they have found in its application, area that need further and future works, implication in the hazard of the area, and so on.

6) Several references (more than 15!!) are in the reference list but they are not in the manuscript. This is a little bit embarassing. Reference list is important as well figure and main text as.

7) Please address also comments in the annoted pdf.

Citation: https://doi.org/10.5194/nhess-2021-351-RC2
- AC2: 'Reply on RC2', Habib Rahimi, 19 Mar 2022
  
  Thank you very much for reading our manuscript in full detail. We edited the manuscript but later realized that at this stage, we only need to answer the questions. We read and considered your comments item by item as follows.
  1- The introduction is missing several worth-to-mention papers and should be improved
  Answer 1:
  Yes - In this section, by studying and reviewing several articles, including (mentioned below), they were added to our introduction so that we can have a better and more up-to-date literature review.
  Baize, S., Nurminen, F., Sarmiento, A., Dawson, T., Takao, M., Scotti, O., Azuma, T., Boncio, P., Champenois, J., Cinti, F.R. and Civico, R., 2020, A worldwide and unified database of surface ruptures (SURE) for fault displacement hazard analyses: Seismol. Res. Lett, 91(1), 499-520.
  Goda, K., 2021, Potential Fault Displacement Hazard Assessment Using Stochastic Source Models: A Retrospective Evaluation for the 1999 Hector Mine Earthquake: GeoHazards, 2(4), .398-414. https://doi.org/10.3390/geohazards2040022.
  Nurminen, F., Boncio, P., Visini, F., Pace, B., Valentini, A., Baize, S. and Scotti, O., 2020. Probability of occurrence and displacement regression of distributed surface rupturing for reverse earthquakes: Front. Earth Sci. 8, 456.
  
  2) The input data must be clearly described both in the main text and in the figure. Fault length and selected site are just two examples.
  
  Answer 2):
  Yes - In this section, in addition to re-editing Figure 1, to introduce the input parameters, we also briefly explained these parameters in the introduction. We also mentioned this because our study is based on the study (Petersen 2011) and his code, and according to your positive opinion, our view in this manuscript changed somewhat compared to the past, we examined the strengths and weaknesses of (Petersen 2011) study and we will explain about it in the following paragraphs.
  
  3) The section Methodology of probabilistic fault displacement hazard analysis needs a deep review. I suggest focusing only on the approach used (i.e., Petersen et al.) and I would like to see all equations used ( and how).
  
  Answer 3): In this section, as mentioned, we first reviewed the history of the method (PFDHA) from (2003), reviewed and introduced on Petersen 2011. Our purpose in this section has been to examine Petersen's method (2011), and we have no claim to change this method in this manuscript.
  
  4) The section Results and Discussions is very poor. There is no discussion about the results and, for me, it has been very hard to understand how input parameters are considered and which equations are used. This paper could help the seismic hazard local community but it need a major review in order to make the manuscript clear and readble. Reading the paper I have the feeling that most of things are omitted and not well described.
  
  Answer 4): Yes - We did our best to revise this section of the manuscript. In this manuscript, we have examined these positive and negative features of Petersen's introduced method, which we have discussed in detail in the Results and Discussions and Conclusion section.
  To explain the obtained results more clearly, we added Figure 9 to the article, which examines and compares the results obtained for two different scenarios and identifies the worst case, and will have a better description of the results obtained.
  
  5) As it is, this work is just an application of an already published work (Petersen et al., 2011). Which is the contribute to the scientific community? even if the authors are in position that they cannot contribute from a methodological point of view, a good discussion section can help to improve the quality of the manuscript, for example, highlighting the critical aspects of this approach, the difficulties that they have found in its application, area that need further and future works, implication in the hazard of the area, and so on.
  
  Answer 5): yes - This comment was very effective and useful for us. We examined the strengths and weaknesses of the work and also examined the applications of this method in northwestern Iran, how they can be effective in the future. This fault has a high level of risk and lacks high instrumental data, and causes uncertainty in studies. For this reason, different scenarios have been considered for displacement estimates.
  
  6) Several references (more than 15!!) are in the reference list but they are not in the manuscript. This is a little bit embarassing. Reference list is important as well figure and main text as.
  
  Answer 6): Yes – we considered your comments and all the mentioned parts has been revised.
  
  Citation: https://doi.org/10.5194/nhess-2021-351-AC2

Mohamadreza Hosseyni and Habib Rahimi

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Short summary

Earthquakes, not only because of earth-shaking but also because of surface ruptures, are a serious threat to many human activities. Reducing earthquake losses and damages requires predicting the amplitude and location of ground movements and possible surface displacements in the future. Using the probabilistic approach and earthquake method, the surface displacement of the North Tabriz fault has been investigated, and the possible displacement in different scenarios has been estimated.


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