<p>Faults are prominent features in the subsurface that define the geological development and distribution of geological formations and resources therein. Faults can define resources themselves (e.g. minerals, thermal conduits), but more often they can pose a hazard to subsurface drilling, injection and extraction activities . Well-known examples are Basel – Switzerland (geothermal stimulation), Oklahoma – US (waste water injection) and Groningen – The Netherlands (conventional hydrocarbon extraction).</p><p>Despite that faults are a typical product of geological mapping, there was, until now, no consistent insight in these structures in a pan-European context. There are some examples focusing on the publication of seismogenic faults (e.g. GEM Global Active Faults Database, SHARE  European Database of Seismogenic Faults, USGS Quaternary faults database), yet deeply buried faults are under-represented here. With the European fault database, the GeoERA-HIKE project addresses the following objectives: i) develop a consistent and uniform repository for fault data and characteristics across Europe, ii) Implement an associated tectonic vocabulary which provides a framework for future interpretation, modelling and application of fault data, and iii) assess the applicability of fault data in case studies.</p><p>The current fault database is envisioned to be a major stepping stone for a sustained and uniform development and dissemination of tectonic data and knowledge which will be applicable to a broad spectrum of subsurface research challenges. The database contains data from Geological Survey Organizations and partners in the Netherlands, Germany, Austria, Belgium, Iceland, Denmark, Poland, Lithuania, Italy, France, Ukraine, Portugal, Slovenia, Albania and various countries in the Pannonian Basin Area.</p><p>The GeoERA-HIKE project has received funding from the European Union’s Horizon 2020 research and innovation programme under agreement No. 731166</p>

<p>In geosciences, where nomenclature naturally has grown from regional approaches with limited cross-border harmonization, descriptive texts are often used for coding data whose meanings in the international context are not conclusively clarified. This leads to difficulties when cross border datasets are compiled. On one hand, this is caused by the national-language, regional and historical descriptions in geological map legends. On the other hand, it is related to the interdisciplinary orientation of the geosciences e.g. when concepts adopted from different areas have a different meaning. A consistent use and interpretation of data to international standards creates the potential for semantic interoperability. Datasets then fit into international data infrastructures. But what if the interpretation to international standards is not possible, because there is none, or existing standards are not applicable? Then efforts can be made to create machine-readable data using knowledge representations based on Semantic Web and Linked Data principles.</p><p>With making concepts reference able via uniform identifiers (HTTP URIs) and crosslinking them to other resources published in the web, Linked Data offers the necessary context for clarification of the meaning of concepts. This modern technology and approach ideally complements the mainstream GIS (Geographic Information System) and relational database technologies in making data findable and semantic interoperable.</p><p>GeoERA project (Establishing the European Geological Surveys Research Area to deliver a Geological Service for Europe, https://geoera.eu/) therefore provides the opportunity to clarify expert knowledge and terminology in the form of project specific vocabulary concepts on a scientific level and to use them in datasets to code data. At the same time, parts of this vocabulary might be later included in international standards (e.g. INSPIRE or GeoSciML), if desired. So called “GeoERA Project Vocabularies” are open collections of knowledge that, for example, may also contain deprecated, historical or only regionally relevant terms. In an ideal overall view, the sum of all vocabularies results in a knowledge database of bibliographically referenced terms that have been developed through scientific projects. Due to the consistent application of the data standards of Semantic Web and Linked Data nothing stands in the way of further use by modern technologies such as AI.</p><p>Project Vocabularies also could build an initial part of a future EGDI (European Geological Data Infrastructure, http://www.europe-geology.eu/) knowledge graph. They are restricted to linguistic labeled concepts, described in SKOS (Simple Knowledge Organization System) plus metadata properties with focus on scientific reusability.  In order to extend this knowledge graph, additionally they also could be supplemented by RDF data files to support project related applications and functionality.</p>