Analysing Civilian Video Footage for Enhanced Scientific Understanding of the 2011 Tohoku Earthquake and Tsunami, Japan, with Implications for PNG and Pacific Islands

Round 1

Reviewer 1 Report

I read with great interest the manuscript. I can not examine in great detail the GIS procedure followed to obtain tsunami inundation and run-up data from civilian video but results seem to me excellent.

I would insert after row 110 a clear definition of run-up and inundation height. Also an appropriate figure would be very useful.

My main concern with the manuscript is the poor quality of data presentation. For example:

fig. 1 is too small so that circles, triangles and so on cannot be distinguished; also the meaning of colour symbols is not visible in legend so that shoul be reported in the caption

fig. 2 and fig. 3 are inverted

fig. 5 what is the meaning of letter K, S and Hn. I suppose is the abbreviation of main Japanese Isles but an international reader could not know this

fig. 6 in the caption is reported the 898 earthquake in the figure 869

fig. 8 red circle showing the position of the study area is quite invisible; I would insert a geographical map instead of a satellite photo and a red star to mark study area position

fig. 13 and 14 are inverted

fig. 20, fig. 21 - not very clear (change colours, enlarge image). I would add the position of the video shooting point.

Moreover, in the text there also several mistakes that should be corrected:

row 77: figure 2 in brackets

row 189: km2 (should be km²)

row 231: Fritz et al., 2012, should be Fritz et al. (2012)

row 236: Foytong et al., 2018 should be Foytong et al. (2018)

and many others so I suggest a deep revision of the manuscript form.

Author Response

Thank you for your helpful review.  Most appreciated. 

In response:

All diagrams are now at higher resolution and Figure 1 has been changed to make it clearer to the readers. The methods and results section has been tightened up with clearer referencing in the text to figures.

We have added definitions re run up and inundation and changed language in the text on this issue to be more precise. 

Suggestions re improving the flow and formatting of the text...e.g. references/citations to literature and figures have been addressed.

Numbered citations are applied as per your suggestion and the editors suggestion. 

Thanks again for your time and expertise.

Mike Petterson 

Reviewer 2 Report

This study analyses civilian video footage to offer a remarkable opportunity to investigate tsunami impacts in localized areas, aiding in understanding tsunami behavior and informing effective mitigation strategies in vulnerable regions.

In the case of Kesennuma City, this method has demonstrated feasibility and value for disaster prevention and urban planning. However, this paper lacks a specific analysis and discussion regarding the significance of the research. It merely focuses on the results generated by the software. As an academic paper, this approach is insufficient. Hence, I recommend a major revision before we can consider proceeding with this paper.

1)    The biggest area for improvement in this paper is the lack of clarity regarding the significance of the research. Although it is mentioned in the abstract that analyzing civilian video footage can provide insights into tsunami impacts, there is a lack of specific analysis and discussion. For example, the authors could map out areas with higher levels of inundation to create a hazard map, which could serve as a reference for urban planning.

2)    Line 36: Tsunamis have significant impacts on coastal areas, whether they are island nations or mainland countries. The reviewer believes it is not necessary to specifically mention Solomon Islands and Tonga, as the focus of this paper is primarily on the research conducted in Japan’s Tohoku region.

3)    Figure 1: The resolution of Figure 1 is very low, and the original image needs to be submitted. Additionally, the reviewer would like to know how dual-factor tsunamis, such as the 2018 Palu tsunami, are defined in the figure.

4)    Line 66: Section 1.2, in my opinion, seems rather redundant as the generation and propagation of tsunamis have already been extensively studied. Since this paper is not a literature review, it is unnecessary to dedicate too much effort to this section.

5)    Line 230: Here the authors could mention the observation of flow velocity using high-frequency (HF) radar, which has been utilized in several studies following the Tohoku tsunami. HF radar can complement video-based observations and provide additional insights.

Reference: https://doi.org/10.1029/2022JB025153

6)    Line 327: If the first wave of the tsunami is a trough, would this method still be able to detect it?

7)    Line 537: The limited number of sampling locations in this study restricts its representation to local tsunami conditions. The authors should mention this limitation.

Minor editing of English language required

Author Response

Thank you for your review, time and expertise.

In response we have:

Added a whole new section re the significance of the work, added your suggested reference, added a local urban tsunami hazard map which summarises the main findings and suggests points for consideration for urban planners.  We would also like to add that we feel the development of a precise and relatively sophisticated methodology for video analysis also constitutes research as does the application of the methodology for calculating quantitative parameters. Part of 'the point' of this research is to open avenues of research to practitioners 'on the ground' who have little 'expert support' to fall back on but who also need to make decisions ...we have further emphasised this application.

We have tightened up diagrams and language re the methods and results section.

We have added references to the more sophisticated techniques re velocity calculations...radar technology.

We have extensively discussed limitations to the method and approach...whilst at the same time suggesting ways for increasing the usefulness of this approach.

We would like to put forward counter arguments to two points made in the review: 1) this paper is to be published in a thematic volume for PNG and the Pacific islands region.  This region is a high tsunami risk region with much more limited geoscience resources than Japan, NZ, USA and other Developed countries.  We would like to retain references to Pacific islands because this audience can learn much from the approaches described in this paper, and because the paper will be published within a Pac island thematic volume.  2) we wish, for similar reasons to retain the section that provides background theory re tsunami causes.  This paper will hopefully be read by many non geoscience experts who may struggle to find appropriate literature to support their understanding.  This modest background review can only assist this type of audience.

We have considered your 'trough first' question and prefer not to include this analysis in the paper although it is an interesting question and thank you for it.  Perhaps offline we can discuss the implications of this questions. 

We hope you will now agree that we have addressed your review and thank you again for your time expertise and helpful comments which have improved the manuscript.

Mike Petterson

Round 2

Reviewer 2 Report

I appreciate the authors’ efforts in revising the manuscript carefully. I have noticed significant improvements compared to the previous version. The authors have extensively discussed limitations to the method and approach.

In addition, I understand that they do not include the “trough first” question in the paper, but I hope they could further investigate it in the future.