The first pan-Alpine surface-gravity database, a modern compilation that crosses frontiers

Zahorec, Pavol; Papčo, Juraj; Pašteka, Roman; Bielik, Miroslav; Bonvalot, Sylvain; Braitenberg, Carla; Ebbing, Jörg; Gabriel, Gerald; Gosar, Andrej; Grand, Adam; Götze, Hans-Jürgen; Hetényi, György; Holzrichter, Nils; Kissling, Edi; Marti, Urs; Meurers, Bruno; Mrlina, Jan; Nogová, Ema; Pastorutti, Alberto; Salaun, Corinne; Scarponi, Matteo; Sebera, Josef; Seoane, Lucia; Skiba, Peter; Szűcs, Eszter; Varga, Matej

doi:https://doi.org/10.5194/essd-13-2165-2021

Articles | Volume 13, issue 5

Earth Syst. Sci. Data, 13, 2165–2209, 2021

https://doi.org/10.5194/essd-13-2165-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Earth Syst. Sci. Data, 13, 2165–2209, 2021

https://doi.org/10.5194/essd-13-2165-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 13, issue 5

Data description paper 19 May 2021

Data description paper | 19 May 2021

The first pan-Alpine surface-gravity database, a modern compilation that crosses frontiers

Pavol Zahorec et al.

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Final revised paper (published on 19 May 2021)
Supplement to the final revised paper
Preprint (discussion started on 15 Jan 2021)
Supplement to the preprint

Interactive discussion

Status: closed

RC1: 'Comment on essd-2020-375', Roland Pail, 07 Feb 2021

General remarks: The first compilation of the pan-Alpine surface-gravity database is a great work, performed by gravity experts in all contributing countries. Even though there are not really new methodologies involved -- in my view the greatest innovation is the consistent use of ellipsoidal heights for CBA computation -- the challenge of homogenization of extremely heterogeneous data sets is huge. The methods that have been gerenally applied are very well described and justified. The authors also reflect critically their choices of methodology and weight them against possible alternatives. All figures included are informative and provide added value. The presentation could habe been more condensed, but not without loss of significant information. In this way, the manuscript is an excellent documentation of the datasets, and very useful as a user guide for potential users.

I very much acknowledge the extended discussion on uncertainties of input data and products in chapter 6. Of course it is a pity that at least a kind of "uncertainty map" is not available together with the product. Although not a straightforward error propagation can be done, there from the analysis of the individual input data sets, as it was done ich chapter 2, some kind of uncertaintly information could have been projected to the final grid as an indicator for the users. However, I see this as one of the potential future aspects, which should not prevent the fast publication of this work.

Technical remarks: From a technical point of view, I do not see much room for improvement. The processing steps are described clearly and could be easily reproduced. Choices of processing strategies are well justified. The paper is written concisely and in very good English language.

In conclusion, I recommend publication in the present form.

Roland Pail

Citation: https://doi.org/10.5194/essd-2020-375-RC1
RC2: 'Comment on essd-2020-375', Anonymous Referee #2, 08 Feb 2021

The paper documents the work of the AlpArray Gravity Research Group (AAGRG) on the creation of a homogeneous Bouguer and free-air anomaly grid for the Alpine area. This is an important work and warrants publication in the ESSD journal.

However, the paper is just a technical report with a documentation of all details possible with regard to the collected data, but does not include any new and/or innovative topics (besides perhaps the interpretation given at the end of the paper). The paper is fine as a technical report, but should not be published as a paper in a journal. My suggestion is to publish the paper in its present form as a technical report (e.g., within a series maintained by the participating institutions or online) and to re-submit to ESSD a significantly shortened and more concise version of the paper on the main topics and results.

Especially the history and database details on a country by country basis (pages 4 to 15) should be condensed and go to an appendix. Also, the list of abbreviations and other detailed information could go to an appendix. Besides the abovementioned history and database details, the paper is lengthy in almost all sections with too many details, not suited for a paper (e.g. reference systems, digital elevation models, mass corrections, validation, etc.).

Overall, the quality of the paper could be significantly improved by just focusing on the main and most important topics, while leaving out several unnecessary details.

Citation: https://doi.org/10.5194/essd-2020-375-RC2
EC1:
'Comment on essd-2020-375', Christian Voigt, 09 Feb 2021
Dear authors,
Thank you very much for your manuscript on the pan-alpine gravity database. As you can see both referees agree that your work is very important and should be published in ESSD. In addition, both referees state that the large amount of detailed background information could or should be condensed. While the first referee accepts the manuscript in its present form, the second one strongly recommends to shift large parts into an appendix.
My own opinion is that these two different decisions reflect the wide range of opinions of future readers interested in using your manuscript. While more experienced readers will not be willing to read 72 pages, young PhD students might be very grateful about all the details. As ESSD is the right platform to present a complete documentation on a published data set, I suggest keeping the information but dividing your manuscript into two parts:
Condense your manuscript and write a concise version on max 15-20 pages to keep it attractive to every reader, while considering the rules of writing a good scientific manuscript.

Refer the interested reader to a greatly expanded appendix.

For the guidance of the reader, a table of content might be helpful.

One final remark: Most of the authors should be familiar with the European Gravimetric Quasigeoid project (EGG) by the IAG:
https://com2.iag-aig.org/sub-commission-24
The compilation and homogenisation of the European gravity data sets has been done since decades and is documented e.g. in
Denker, H.: Regional gravity field modeling: Theory and practical results, Monograph in: Xu G. (ed.), Sciences of Geodesy – II, Chapter 5: 185-291, Springer, Berlin, Heidelberg, doi: 10.1007/978-3-642-28000-9_5, 2013.
So, I would like to give thought to whether your title on the “first … surface-gravity database…” and expressions such as “the first compilation…” are justified. At least this work has to be addressed.
Best regards,
Christian Voigt
(Topical Editor of ESSD)
Citation: https://doi.org/10.5194/essd-2020-375-EC1
CC1: 'Comment on essd-2020-375', Magdalena Scheck-Wenderoth, 11 Feb 2021

I would like to emphasize that his is an extremely valuable contribution for which a lot of scientists have been waiting for ages.
This is not a paper on gravity data aquisition, geodesy or the geoid, but a paper offering a base for future multidisciplinary earth science research. The presented database is intended as the authors say to support integrated analysis linking structural geology, tectonics, mineralogy, geomorphology, seismic and electric methods.
Clearly gravity data are the observations that help to integrate a lot of other informations in 3 dimensions. Those who have tried to link the information of 2D deep seismic lines and other shallow 1D/2D observations into a physics based 3D representation of physical properties on the scale of the crust know about what I speak here. It always was a major barrier that data was not publicly available, not documented properly and restricted to domains limited by political boundaries. This piece of work presented here is the outcome of a gigantic joint effort that paves the way for the next generation of geodynamic understanding.
I do not agree with the posted comments that there is nothing new in the paper. The data is new and has never been presented before. Not only do these data resolve regional patterns at an unprecedented accuracy, they also will allow to resolve crustal density distributions in the future und thus understand GPE, stress and structure at the scale of the orogen.
Previous gravity maps of the region either did not "see" certain wavelengths or were not public or did not come with a proper documentation on how ground-based, plane-based and satellite data have been married.
I therefore congratulate the team of authors to have kept the faith in this endeavour of integrating cross-country-cross method and to have provided a proper documentation of how the data has been treated. Yes the paper presents a long, honest and detailed description of these treatments including related uncertainties, but I consider this a strength of the mansucript. These integration methods are scientific achievements on their own, but the real added value for the community lies in the data. Finally it is possible to evaluate in great detail density heterogeneities at the full crustal level, not to speak of the many other options of analysis, such as assessment of differen gravity gradients and their relationship to structural elements.
For the above reasons I look forward that these data will published and thus be made available as fast as possible.

Citation: https://doi.org/10.5194/essd-2020-375-CC1
AC1:
'Comment on essd-2020-375', Hans-Jürgen Götze, 15 Feb 2021

Dear Christian Voigt, dear Roland Pail, dear Anonymous,
First, we would like to thank you for the time invested in reviewing our (long) manuscript. We are pleased that the assessment of the content and the significance for the geo community is positive, also documented by a very positive public comment by Leni Scheck-Wenderoth. After intensive internal discussion will largely follow the suggestions of the topical editor.
With respect to the comments by the reviewers:
Roland Pail has acknowledged in his review the work done by the international AAGRG over the last years and we believe that he has fully accepted our intention in writing the manuscript - we appreciate his review very much.
Regarding the anonymous review, we would like to address some aspects of his review in more detail. ESSD expects a precise and comprehensive, even detailed description of the data sets provided. The presented dataset is the result of national data collection of the Alpine countries for almost 100 years applying different techniques of data acquisition and processing. Therefore, detailed explanation as provide by us is very much needed and we disagree with the suggestion to publish the manuscript as a report at one of the participating institutions. The technical description is novel and very much need to comprehend the details of the data sets. If the interest is only in applying the data on a regional scale, such details might not be needed, but for applications interested in the details of the data sets, that is critical information.
We strongly disagree that our work does not contain "something new and/or innovative topics" and with the recommendation that "the historical data details" should be condensed as they contain important meta-information that was/is indispensable for the overall data processing. We have asked ourselves why "reference systems”, DEMs, explanations of mass correction and validation should be superfluous. We consider the evaluation of the "uncertainty" of the new CBA data as an important point.
As the editor agrees on, the presented manuscript will surely attract a wide and diverse readership, already now downloads of the preview on ESSD are numerous with about 500 accesses.
While we do not consider that the length of a paper should be subject for criticism, if the content requires such details, we will put substantial chapters (e.g. history with contributions of individual countries, metadata description, list of abbreviations and some short technical chapter parts) in an appendix to increase appeal to the reader. Whether we will reach the proposed number of pages of 15 - 20 remains to be seen, because we think that the numerous performed processing steps must be clearly preserved in the description.
Concerning the actuality and novelty of the data compilation we carried out, we would like to reply to the opinion of the reviewer 2 that this compilation would not result in anything new. On the contrary, thousands of unpublished (e.g., industry) data have been included in the compilation due to the contracts we have signed with the participating countries. These data may neither be shown as point data, nor described as such. By agreement we can publish the new database "only" on a 4 km x 4 km grid and give the 2 km x 2 km grid exclusively to members of the AlpArray consortium only after of the participating institutions.
This is also the significant difference to the noteworthy work of Heiner Denker, whose work for the IAG we will mention in our manuscript - thanks for this hint. The database described and published here is unique in this respect also justifies the designations "first... Bouguer gravity database” etc. Furthermore, we would like to mention that neither an improvement of the quasigeoid nor of the geoid in the difficult high mountains of the Alps was in our focus. Our aim is to provide a valuable contribution for the numerous interdisciplinary projects in the AlpArray initiative and other European geo projects (see also comment by Prof. Scheck-Wenderoth) that supports lithosphere and mantle modelling in the Alpine-Mediterranean region.
We are already working on a revision of the manuscript along the lines of Christian Voigt's summary and hope that this urgently needed new database can be published soon.

Citation: https://doi.org/10.5194/essd-2020-375-AC1
- RC3: 'Reply on AC1', Roland Pail, 15 Feb 2021
  
  Dear all,
  I fully agree with the proposal by the editor and the authors.
  In my view, restructuring the article is a little bit of grunt work, because any reader who is interested in the subject can decide for himself/herself if the historic part is interesting or not, and he/she could easily skip it during reading. (I found it very inspiring, because it gives an impression of the great work that had to be done to achieve this new compilation.) Therefore, in the end it does not make much difference if it appears in the main text or the appendix. However, if it makes the main text more handy and helps solving the problem, it is a good compromise solution.
  Best regards,
  
  Roland Pail
  
  Citation: https://doi.org/10.5194/essd-2020-375-RC3
CC2: 'Comment on essd-2020-375', Michael H. Weber, 16 Feb 2021

I would like to congratulate the authors for tackling the long unresolved challenge of a unified “gravity” approach spanning the Alps and their surroundings. Such an approach has been missing for quite some time.
Not being a gravity-person I can not judge fully the novelty in all the processing and corrections applied. Possibly this part could be shortened a bit, to help the general audience to appreciate the work presented. On the other hand, the next generation of geoscientists could use this carefully documented approach to learn how it should be done.
The long-lasting impact of this paper is clearly that provides a long-lasting basis for ongoing and future interdisciplinary studies and the interpretation and the dynamics of the Alps especially. The data base created by this huge team of authors, now available to the whole geo-community, cannot be underestimated in its value; this is thus clearly something new.
For this reason, I strongly support the opinion that this amazing piece of work is published asap.

Citation: https://doi.org/10.5194/essd-2020-375-CC2

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Hans-Jürgen Götze on behalf of the Authors (26 Mar 2021) Author's response Author's tracked changes Manuscript

ED: Publish subject to technical corrections (12 Apr 2021) by Christian Voigt

AR by Hans-Jürgen Götze on behalf of the Authors (14 Apr 2021) Author's response Manuscript

Short summary

The gravity field of the Earth expresses the overall effect of the distribution of different rocks at depth with their distinguishing densities. Our work is the first to present the high-resolution gravity map of the entire Alpine orogen, for which high-quality land and sea data were reprocessed with the exact same calculation procedures. The results reflect the local and regional structure of the Alpine lithosphere in great detail. The database is hereby openly shared to serve further research.