The European Archive of Historical Earthquake Data (AHEAD) installation operates under the auspices of the TCS-Seismology work program,
and considers the principles expressed by the EPOS Data Policy.
AHEAD data consist of the background information of pre-instrumental earthquakes as derived from historical earthquake research.
AHEAD mainly relies on eight regional partners' archives, which supply most of the data, and on data derived from the recent scientific literature.
In addition, a special effort is aimed at making accessible macroseismic data points (MDPs). AHEAD privileges published and open access sources of data.
Quality control of the data available in AHEAD is performed according to the steps and the diagram shown below.
The procedure includes data retrieval, processing and validation steps, and control points.
The uploaded data are prepared, checked and validated to ensure that they conform to the standards and formats used in AHEAD
(Locati et al. 2014; Rovida and Locati 2015).
Inconsistencies in the data structure are identified through careful quality controls involving both relational database tools and manual revisions.
Once the data and metadata are compiled, verified, and made compliant to the FAIR principles,
they are made openly available on the AHEAD web portal and through the AHEAD web services.
These web services are compliant with the FDSN event, OGC WFS, and OGC WMS standards, making AHEAD data accessible by the EPOS ICS portal.
In detail, the steps of the data publication and Quality Control process are:
Step 1 - Data source identification.
New sources of earthquake data are identified in the literature through journals’ mailing lists and social networks by the AHEAD Core Team or reported by the AHEAD partners and contributors.
The identified data sources are then transferred or made accessible to the AHEAD Core Team.
Step 2 - Data source examination and validation.
The identified or suggested data source is examined by the AHEAD Core Team. The data intended for distribution must address the objectives of AHEAD and fulfil its standards. In particular, the candidate data source must deal with earthquakes in the area and time period considered in AHEAD and must provide the results of historical seismological investigations in terms of earthquake parameters, macroseismic data points (MDPs), or textual descriptions of earthquake effects. References to the sources of information and the steps followed throughout the investigation and/or parametrization should be preferably made explicit. Only publicly accessible data sources are taken into consideration and the licence associated with the data sources is evaluated.
The fulfilment of the objectives and requirements of AHEAD is checked and the redistribution of both the original data source and the provided data is evaluated.
Step 3 - Compilation of bibliographical metadata.
The source of data, in any format (journal article, conference proceeding, public report, database, etc) is registered and its standard bibliographical metadata are compiled and stored in the relevant table of the AHEAD relational database. The data source is stored and preserved in the internal repository.
Step 4 - Extraction and standardisation of event data.
Event data (e.g., date, location, magnitude) are identified within the data source and analysed, the event data are then standardised (e.g. date and/or geographical coordinates conversion) and a new record of the dedicated event table of the relational database is manually compiled for each event.
Step 5 - Attribution of the event identifier.
Through the analysis of the parameters and the additional information contained in the data source, each new record of the events table, representing an event, is associated with an event identifier, either already existing or newly created in case a non-existing event is introduced.
The consistency of all earthquake parameters is verified and the association with other AHEAD records by means of the event identifier is checked; the uniqueness of newly created identifiers is ensured.
Step 6 - Extraction and standardisation of intensity data.
In case the data source also provides macroseismic intensity data, they are analysed, standardised and manually added to the relevant table of the AHEAD relational database. Each place mentioned in the data source is georeferenced using a European-wise reference system with unique place identifiers, names, and geographical coordinates, and intensity values are homogenised (e.g., roman to arabic numerals). For each intensity point both the original and the homogenised place name, coordinates and intensity values are stored in the table.
The consistency of the intensity distribution is carefully checked in both table and map.
Step 7 - Data publication.
The data source and its metadata, the event(s) data and the related intensity distribution(s) are finally published in the AHEAD web interface and web services.
The correct visualisation of the event, the correct association with other data sources through the event identifier, the intensity data and the data source bibliographical metadata are checked both on the web portal and by accessing data via web services.