The Importance of Assessing the Geological Site Effects of Ancient Earthquakes from the Archaeoseismological Point of View

Round 1

Reviewer 1 Report

The paper is clear and easy to read, and may be interesting to archeologists not familiar with seismology. But on the scientific hand, there is nothing significantly new here. All these considerations on local effects are quite classical in seismology.

Author Response

Dear Reviewer,

Thank you very much for your dedicated time reviewing my manuscript. I appreciate it.

• Indeed, it is true that the archaeological community is somewhat unfamiliar with the topic of "local site effects" and other seismological topics. I believe this is the cause of poor or inadequate documentation of ancient earthquakes in the archaeological record. Moreover, the extrapolated implications found in archaeological literature on such grounds merit true archaeoseismological research.
• Basically, the tone of the paper is to bring seismology to archaeologists.
• I have addressed the English language and style issue in the manuscript.

Thank you very much for your time.

Reviewer 2 Report

This article presents an interesting study about the importance of assessing the geological site effects of ancient earthquakes from the archaeoseismological point of view. Text and figures are very clear. Examples and references are well chosen. I recommand the acceptance in present form for this article.

Author Response

Dear Reviewer,

Thank you very much for your dedicated time reviewing my manuscript. I truly appreciate it.

You have recommended the manuscript for publication as it is; however, other reviewers have recommended changes, so you might or might not see some improvements when I submit it to address the first round of reviews. 

Once again, thank you very much for your time in reviewing the manuscript.

Reviewer 3 Report

The manuscript can be accepted with minor corrections

Comments for author File: Comments.rar

Author Response

Dear Reviewer,

Thank you very much for your reviewing this manuscript. It is much appreciated it.

All your comments and suggestions have been addressed individually; however, you might notice additional changes per the reviewers' request. 

Once again, thank you very much for your time reviewing the manuscript.

Reviewer 4 Report

The manuscript discusses the need for enhanced quantitative methods to support the identification of the past earthquake effects at the Archeological sites. The authors suggest the use of local seismic response LSR analyses under 1D conditions. However, the following points are unclear:

1) Why not to use 2D analyses, when the case

2) How can be used the results from LSR in archeoseismicity studies?

These two points are the main concern of this manuscript. Thus, they need to be clarified before the manuscript could be accepted for publication. 

Furthermore, other suggestions and comments inserted directly on the review copy of this manuscript must be also addressed. 

Comments for author File: Comments.pdf

Author Response

Dear Reviewer,

Thank you very much for your devoted time reviewing this manuscript. I appreciate it. Most of your review centralizes on the local site response analysis approach, which is dealt with in section 5 of the manuscript. I have addressed all your comments and suggestions to the best of my knowledge, which are explained below:

Reviewer: The manuscript discusses the need for enhanced quantitative methods to support the identification of the past earthquake effects at the Archeological sites. The authors suggest the use of local seismic response LSR analyses under 1D conditions. However, the following points are unclear:

1) Why not to use 2D analyses, when the case

Author: Generally, most archaeological sites worldwide occur in sedimentary basins or valleys; however, they also occur on topographic highs. This observation is justified because most civilizations looked for accessible land and convenient environmental conditions. A 1D local site response (LSR) analysis is standard in geotechnical earthquake engineering. Its goal is to estimate the nonlinear cyclic response of soils with either a nonlinear model or the equivalent–linear model. A 1D LSR analysis can capture the essential aspects of surface ground response; however, it cannot model slopping, irregular ground surfaces, basin effects, topographic effects, and embedded geologic structures, which are apt for 2D or 3D models. However, 2D or 3D modeling efforts are too expensive for most archaeological project budgets. A 1D LSR analysis solves the problem of horizontally polarized vertically propagating shear waves with planar wavefronts from the bedrock into horizontally layered soils with frequency-independent damping (valley geology). A 1D LSR analysis considers the wave modification properties of layered, damped soil deposits overlying weathered/unweathered elastic bedrock. The use of 1D site models from sedimentary basins with a width-to-depth ratio (WDR) ≥ 6 is considered valid for a 1D LSR analysis according to Zhang and Zhao (2009) (reference: Response spectral amplification ratios from 1- and 2-dimensional nonlinear soil site models, Soil Dynamics and Earthquake Engineering. 29, 563-573). So for cases where the sedimentary basin's width is much broader than its thickness or depth (WDR ≥ 6), a 1D site-response analysis is appropriate. In addition, it is economically affordable for an archaeological project's budget. I have added this reference to the manuscript and this explanation at the beginning of section 5.

 

2) How can be used the results from LSR in archeoseismicity studies?

Author: A LSR analysis allows the calculation of site-specific surface amplification and associated surface ground motions at multiple sites due to potential ancient earthquake ground shaking. If ground-acceleration-dependent empirical equations of MMI are available for the region, the MMI value for every site can be calculated using the computed surface accelerations obtained in the 1D LSR analysis. Hence, if a distribution of MMI values is obtained, isoseismal lines can be drawn for the area leading to a more accurate reconstruction of a macroseismic intensity map. I emphasize that the earthquake source parameters also need to be modeled because the ancient causative earthquake/fault is often unknown in the archaeological or geological context. The LSR approach requires input from archaeological, geoarchaeological, geophysical, geological, geotechnical, and historical (if available) investigations relevant to the site(s) of interest. The premise is that such sources of information must facilitate the reconstruction of the ancient ground surface conditions at the time of the (postulated) ancient earthquake, requiring the identification and removal of accumulated soils younger than the archaeological horizon of interest; and leading to a realistic assessment of the "ancient walking horizon" and modeling sites. This critical step avoids an over-or-underestimation of local site effects. Figure 4 tries to explain this entire sequence. From such comprehensive LSR and synthetic earthquake scenarios, one can shed light on the possible causative ruptured faults that might explain observed co-seismic damage to anthropogenic structures. I have included this explanation in section 5.

Furthermore, other suggestions and comments inserted directly on the review copy of this manuscript must be also addressed.

Author:

• The abstract and the text have now clarified the objective of this study.
• The paper by Vessia et al. (2021) has now been incorporated into the text and the reference list. Thank you for sharing this (summary) paper.
• As per your request, the inset in Figure 1 (archaeological site in the valley) has been moved to the valley's center. Yes, the sedimentary basin edge effects play a role. Thank you.
• Per your request, the statement on lines 79 to 80 about what causes soil amplification has been corrected.
• The paper by Lanzo et al. (2019) has now been incorporated into the text and the reference list. Thank you for pointing out this illustrative paper.
• The comment referring to lines 230-231 ("The goal of this study should be to use the seismic response analyses within archaeoseismicity procedure.”) was already explained in section 5.
• The comment referring to lines 244-246 ("How can be built the synthetic motions if no info on the seismic source activity and characters of the past is available?") was already explained in section 5, explicitly using Figure 4. I made a better attempt in the text to emphasize this point.
• I improved the explanation of the flowchart in Figure 4. Thank you.
• As per your request, a brief mention of the degradation curves was made. Thank you.
• The MMI means Modified Mercalli Intensity scale. I spelled out the abbreviation in the text and figure. The archeological community is most familiar with the MMI scale because of its practicality. So, it is possible to translate ground acceleration values to MMI values using empirical equations of ground accelerations for Greece. Hence, the MMI value is calculated using the acceleration values, which account for the local site effects.
• The comment referring to lines 412-413 has been addressed by explaining how site-response analysis helps estimate isoseismal lines and thus reconstruct the macroseismic intensity scenario. Thank you.
• The comment referring to line 435 has been addressed. Thank you.

 

English language and style are fine/minor spell check required

Author:  The grammar and style have been revised.

 

Once again, thank you very much for your time reviewing the manuscript. Have a nice day.

Round 2

Reviewer 1 Report

The answers to my previous comments give a different light on this paper, together with the supplementary texts.

Reviewer 4 Report

Dear Authors,

the revised manuscript answers all my comments and questions. According to me, the paper is now ready to be published. I have appreciated your multidisciplinary study!