Knowledge graphs for seismic data and metadata

The increasing scale and diversity of seismic data, and the growing role of big data in seismology, has raised interest in methods to make data exploration more accessible. This paper presents the use of knowledge graphs (KGs) for representing seismic data and metadata to improve data exploration and analysis, focusing on usability, flexibility, and extensibility. Using constraints derived from domain knowledge in seismology, we define semantic models of seismic station and event information used to construct the KGs. Our approach utilizes the capability of KGs to integrate data across many sources and diverse schema formats. We use schema-diverse, real-world seismic data to construct KGs with millions of nodes, and illustrate potential applications with three big-data examples. Our findings demonstrate the potential of KGs to enhance the efficiency and efficacy of seismological workflows in research and beyond, indicating a promising interdisciplinary future for this technology., The data here consists of, and was collected from:

Station metadata, in StationXML format, acquired from IRIS DMC using the fdsnws-station webservice (https://service.iris.edu/fdsnws/station/1/).
Earthquake event data, in NDK format, acquired from the Global Centroid-Moment Tensor (GCMT) catalog webservice (https://www.globalcmt.org) [1,2]. 
Earthquake event data, in CSV format, acquired from the USGS earthquake catalog webservice (https://doi.org/10.5066/F7MS3QZH) [3].

The format of the data is described in the README. In addition, a complete description of the StationXML, NDK, and USGS file formats can be found at https://www.fdsn.org/xml/station/, https://www.ldeo.columbia.edu/~gcmt/projects/CMT/catalog/allorder.ndk_explained, and https://earthquake.usgs.gov/data/comcat/#event-terms, respectively.
Also provided are conversions from NDK and StationXML file formats into JSON format. 
References:
[1] Dziewonski, A. M., Chou, T. A., & Woodhouse, J. H. (1981). Determination of earth..., No special programs or software is reqired to open the data files included here., # README

List of data provided:

* example1.tar.gz
* example1-events-gcmt.ndk
* example1-events-gcmt.ndk.json
* ~~example1-events-ncedc.csv~~
* example1-events-usgs.csv
* example2.tar.gz
* example2-events-gcmt.ndk
* example2-events-gcmt.ndk.json
* example2-stations-stationXML.xml
* example2-stations-stationXML.json
* example3.tar.gz
* example3-events-gcmt.ndk
* example3-events-gcmt.ndk.json
* example3-events-usgs.csv
* example3-stations-stationXML.xml
* example3-stations-stationXML.json

# Individual descriptions

## In: example1.tar.gz

### example1-events-gcmt.ndk

Description:
Event data used in example 1, downloaded from the Global Centroid Moment Tensor Project (https://www.globalcmt.org/). A complete description of the NDK file format can be found at the following [link](https://www.ldeo.columbia.edu/~gcmt/projects/CMT/catalog/allorder.ndk_explained).

### example1-events-gcmt.ndk.json

Description:
Data from file example1-event...