This work describes the characteristics and infrastructure of the “Active Faults of Eurasia Database”. The database comprises 46,775 structures formatted as a shapefile with spatial detail sufficient for a map at a  1:1 M scale. Each fault has a database that comprises fault sense, a rank of confidence, a rank of slip rate, and reference to source publications, supplemented, wherever possible, with a fault name, fault zone name, abbreviated fault parameters and text information from the sources. The database is available at various websites.

This work is of large international relevance and represents a step forward in the representation of the state-of-the-art knowledge of active faults, especially in Asia, where most studies are available in Russian and as hardcopy.

This database helps in the search of active faults in a given area, useful for assessing the framework of regional tectonic activity, or for focusing more in detail on a given structure. It provides the backbone for the study of a particular fault, and guides more-in-depth bibliographic analyses.

The paper is well written and contains all major information on the database, with a couple of short examples. I would only encourage the authors to add some more explanations about the seismicity showed in their web map. The map, in fact, contains also seismicity divided by major, middle and minor earthquakes. It would be wise to know more about the sources of these data, and the criteria of selection of the showed seismic events.

I recognize that it has been a strong effort to gather all this information. I also recognize that the authors have stated, at the ending of the paper, that they encourage researchers to advise them about missing or recently obtained data. Anyway, I have seen the lacking of some major active faults in the present database; for example, in Iceland very few faults have been presented in the database, respect to the available information. Among these, it should be added in the database at least the famous Husavik-Flatey transform fault that is now missing: this is a 100-km-long active structure that comprises an offshore section and a 25-km-long onland section. This structure has been widely studied with clear evidence of Holocene offset deposits, morphological indicators of right-lateral strike-slip motions, elongated seismicity along the fault trace (with some major earthquakes) and at least one paleoseismological trench opened across the fault (some relevant literature:  Metzger et al., 2013, Present kinematics of the Tjornes Fracture Zone, North Iceland, from campaign and continuous GPS measurements. Geophys. J. Int., 192, 441-455. Pasquarè Mariotto et al., 2015, Holocene displacement field at an emerged oceanic transform-ridge junction: The Husavik-Flatey Fault - Gudfinnugja Fault system, North Iceland. J. Struct. Geol., 75, 118-134. Tibaldi et al., 2016, Interaction between transform faults and rift systems: a combined field and experimental approach. Frontiers in Earth Science, 4, 33. Tibaldi et al., 2016, Partitioning of Holocene kinematics and interaction between the Theistareykir Fissure Swarm and the Husavik-Flatey Fault, North Iceland. Journal of Structural Geology, 83, 134-155).

A few detailed observations on the text follow here:

At Line 30 it would be better to introduce here ILP with the entire name International Lithosphere Program, and after that you can use the acronymous. It is fully introduced only at Line 163.

Line 75 IN the database?

Line 93 Not clear why here you write about a target map scale of 1:1 M, whereas previously, at Line 36, you speak about 1:5 M scale, and then at Line 98 you cite a 1:500 000 scale. Explain better.

This manuscript describes the schema and strategy for compiling the Active Faults of Eurasia Database (AFEAD). It also provides a link to the database itself. The database can be accessed freely through a wed mapper interface and downloaded as images (jpg) with topographic background or as vectors (kmz or shapefile) of predefined tiles. The shapefile of the entire collection of faults and an Excel file with the list of references are also available for download through the ResearchGate link.

I commend the authors for the great effort in putting together such an extensive compilation of faults. I am also aware that there is a need for earth scientists to get hold of this type of data through a single access point. Nonetheless, I’m afraid that at the moment, this collection of data suffers from a few weaknesses. In brief, they are: 1) most scientific content is outdated; 2) the database design and organization of the data is technically poor. I elaborate on these aspects in the following.

Scientific weaknesses

The data collection is based on bibliographical investigations, but most of the bibliographic references are quite outdated. Out of the 657 references (in the Excel file), only 13 are post-2010. Of these 13, three are classified as unpublished information. Of all 657, 55 are classified as unpublished information, most of which are as old as 1996. How reliable can be a piece of information supplied to the authors 25 years ago and never published since then?

In the last decade, several active fault databases have been published containing updated information. Below I list some of them (not necessarily exhaustively) that have significant geographical overlap with AFEAD and contain more up-to-date data than AFEAD.

•    Europe (Atanackov et al., 2021; Caputo & Pavlides, 2013; DISS Working Group, 2018; European Geological Data Infrastructure, 2021; Ganas, 2021; Jomard et al., 2017; Vanneste et al., 2013)

•    Middle East (Danciu et al., 2018)

•    Central Asia (Mohadjer et al., 2016)

•    Georgia (Onur et al., 2019, 2020)

•    Japan (National Institute of Advanced Industrial Science and Technology, 2012)

•    Africa (Williams et al., 2021)

•    World (Christophersen et al., 2015; Styron & Pagani, 2020)

Apart from those compilations released in the last year, most of these have been around for quite a long time now. In addition to this lack of data, the relationship between the fault representation in AFEAD and the fault representation in the source dataset is not clear. This is of particular concern for the blind faults since only criteria associated with the topographic signature are recalled. On the one hand, not considering the latest fault compilations prevents AFEAD from listing the newly recognized active faults. On the other hand, it also prevents AFEAD from eliminating those faults that were once considered active but are currently considered not active based on new evidence. Unfortunately, the CONF parameter does not consider the recency of the information.

The compilation of the fault parameters also remains rather obscure in several aspects. For example, of the 47,363 faults, 22,270 (47%) have no parameter assigned (field “Parm” is NULL). Of the 25,093 faults with the field “Parm” not NULL, only 6,849 reports a “Rate=” value; how was then the Rate (rank) parameter assigned to the remaining faults?

Technical weaknesses

The AFEAD is distributed as a single shapefile. Technically speaking, it is not even a database apart from the implicit relation between geographic features and their attributes. No relational table is provided between AFEAD and any of its linked information. In other words, it should be classified as a geographical flat-file, not a proper database.

The fields in the shapefile attribute table are very poorly organized.

First of all, none of the fields can be identified as a primary key. The lack of a primary key prevents the user from uniquely identifying any records and establishing their possible relations with external information. Also, the user cannot make an explicit reference to an individual AFEAD record when using it, including this review.

Both the “Auth” and “Parm” fields contain long text strings that, in the next update, could become even longer and easily exceed the limitations imposed by the shapefile format. Notice that the maximum number of characters in a text field of a shapefile is 254, see Attribute limitations in ESRI documentation at: https://desktop.arcgis.com/en/arcmap/latest/manage-data/shapefiles/geoprocessing-considerations-for-shapefile-output.htm#GUID-A10ADA3B-0988-4AB1-9EBA-AD704F77B4A2

or

https://support.esri.com/en/technical-article/000012081

These two fields are also very difficult to explore, especially the Parm field that contains very heterogeneous parameters. This poor organization makes it hard for the user to use the database. For example, selecting the faults that have a certain “depth” information would require a very complex query, which would discourage the non-experts in SQL and expose the users to uncertain results. Also, the Parm field takes up more bytes than needed by repeating within the field the word to identify the parameter type, such as “Sense=” or “Rate=” or “Depth=”, occasionally also including the reference to the parameter itself.

The use of the “+” (plus) sign in the “Side” field is unnecessary because all the non-null values are a plus. It could also be troublesome because the plus sign can be automatically converted when importing the data in other systems (try saving the attribute table into the Microsoft Excel format, for example).

Other issues (listed by line "L" number)

L1: The name of the database does not reflect its abbreviation “AFEAD” should be “Active Faults of Eurasia Database,” not “Database of the Active Faults of Eurasia.” Please make a choice and stick to it.

L14: In the file provided, the sources are 657, not 612. The difference is 55, which corresponds to the number of unpublished work. Rephrase to make this clear for the readers.

L25: Unclear reference to “Geologische Rundschau, 1955”; see also L327.

L72-74: This statement is unclear, or it is at least quite questionable. Linear landforms created by nontectonic processes are not rare, and several earthquakes have reactivated faults with very complex patterns. Also, cases of tectonic inversion are known. Maybe the authors can expand this paragraph to make it clearer and more documented for what they want to say.

L91-92: Is the fold axis represented? Otherwise, which element of the structure is represented? And how can the user be aware of that?

Table 1: Is the strike-slip with unknown sense contemplated?

L166: Unclear to whom “our team” is referring.

Recommendations

The following technical fixes are necessary to make AFEAD suitable for using it in a proper DBMS.

•    Establish a primary key that uniquely identifies each record (fault) of the shapefile.

•    Separate the “Parm” attributes into different columns, paying attention to storing single numerical values in individual columns.

•    Establish a primary key for the table of bibliographic references.

•    Create a relational table (many to many) that connects the fault table primary keys with the bibliographic reference table primary keys.

•    Once the relational table is created, the column “Auth” can be deleted from the shapefile.

•    Remove all “+” “-“ “=” and similar signs/symbols from all columns. Use the “+” or “-“ sign only with numerical values.

The European plate boundary along the Mid-Atlantic Ridge should be completed to make AFEAD adhere to its name (it could be disappointing for the AFEAD user to find data in the African plate and not the complete European plate).

More explanations are needed to make the user understand the source of information used to assign the Rate ranks.

A justification is needed for not considering all the recent fault data compilations published in the last decade. The authors should also discuss the implications due to the lack of updated information and warn the users about the limitations in using AFEAD instead of more up-to-date regional/local data.

References

Atanackov, J., Jamšek Rupnik, P., Jež, J., Celarc, B., Novak, M., Milanič, B., et al. (2021). Database of Active Faults in Slovenia: Compiling a New Active Fault Database at the Junction Between the Alps, the Dinarides and the Pannonian Basin Tectonic Domains. Frontiers in Earth Science, 9, 604388. https://doi.org/10.3389/feart.2021.604388

Caputo, R., & Pavlides, S. (2013). Greek Database of Seismogenic Sources (GreDaSS): A compilation of potential seismogenic sources (Mw > 5.5) in the Aegean Region [Text/html,application/vnd.google-earth.kml+xml,image/jpg]. University of Ferrara, Italy. https://doi.org/10.15160/UNIFE/GREDASS/0200

Christophersen, A., Litchfield, N., Berryman, K., Thomas, R., Basili, R., Wallace, L., et al. (2015). Development of the Global Earthquake Model’s neotectonic fault database. Natural Hazards, 79(1), 111–135. https://doi.org/10.1007/s11069-015-1831-6

Danciu, L., Şeşetyan, K., Demircioglu, M., Gülen, L., Zare, M., Basili, R., et al. (2018). The 2014 Earthquake Model of the Middle East: seismogenic sources. Bulletin of Earthquake Engineering, 16(8), 3465–3496. https://doi.org/10.1007/s10518-017-0096-8

DISS Working Group. (2018, April 26). Database of Individual Seismogenic Sources (DISS), version 3.2.1. Istituto Nazionale di Geofisica e Vulcanologia (INGV), DOI: 10.6092/INGV.IT-DISS3.2.1. Retrieved July 14, 2020, from http://diss.rm.ingv.it/diss/

European Geological Data Infrastructure. (2021). HIKE European Fault Database. Retrieved from https://geoera.eu/projects/hike10/faultdatabase/

Ganas, A. (2021). NOAFAULTS KMZ layer Version 3.0.1 (2021 update) (Version V3.0.1) [Data set]. Zenodo. https://doi.org/10.5281/ZENODO.4897894

Jomard, H., Cushing, E. M., Palumbo, L., Baize, S., David, C., & Chartier, T. (2017). Transposing an active fault database into a seismic hazard fault model for nuclear facilities – Part 1: Building a database of potentially active faults (BDFA) for metropolitan France. Natural Hazards and Earth System Sciences, 17(9), 1573–1584. https://doi.org/10.5194/nhess-17-1573-2017

Mohadjer, S., Ehlers, T. A., Bendick, R., Stübner, K., & Strube, T. (2016). A Quaternary fault database for central Asia. Natural Hazards and Earth System Sciences, 16(2), 529–542. https://doi.org/10.5194/nhess-16-529-2016

National Institute of Advanced Industrial Science and Technology. (2012). Active Fault Database of Japan, February 28, 2012 version. Research Information Database DB095, National Institute of Advanced Industrial Science and Technology. Retrieved from https://gbank.gsj.jp/activefault/index_e_gmap.html

Onur, T., Gok, R., Godoladze, T., Gunia, I., Boichenko, G., Buzaladze, A., et al. (2019). Probabilistic Seismic Hazard Assessment for Georgia (No. LLNL-TR--771451, 1511856) (p. LLNL-TR--771451, 1511856). https://doi.org/10.2172/1511856

Onur, T., Gok, R., Godoladze, T., Gunia, I., Boichenko, G., Buzaladze, A., et al. (2020). Probabilistic Seismic Hazard Assessment Using Legacy Data in Georgia. Seismological Research Letters, 91(3), 1500–1517. https://doi.org/10.1785/0220190331

Styron, R., & Pagani, M. (2020). The GEM Global Active Faults Database. Earthquake Spectra, 36(1_suppl), 160–180. https://doi.org/10.1177/8755293020944182

Vanneste, K., Camelbeeck, T., & Verbeeck, K. (2013). A Model of Composite Seismic Sources for the Lower Rhine Graben, Northwest Europe. Bulletin of the Seismological Society of America, 103(2A), 984–1007. https://doi.org/10.1785/0120120037

Williams, J. N., Wedmore, L. N. J., Scholz, C. A., Kolawole, F., Wright, L. J. M., Shillington, D., et al. (2021). The Malawi Active Fault Database: an onshore-offshore database for regional assessment of seismic hazard and tectonic evolution (preprint). Geophysics. https://doi.org/10.1002/essoar.10507158.1