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How can we test if a seismic hazard input model is capable of producing a sufficiently realistic rupture for a significant event? A study led by Christopher Brooks (GEM Seismic Hazard Scientist) introduces the Global EarthquakE ScEnarios (GEESE) rupture matching algorithm, an OpenQuake Engine-based tool that retrieves appropriate ruptures (in terms of hypocentral location, magnitude, rupture geometry and style-of-faulting) from seismic hazard input models. Alongside the evaluation of seismic hazard input models, the GEESE algorithm can be used within post-event response to generate an initial finite rupture when other data required to perform a detailed inversion has not yet been disseminated.
Building a Global Database
The GEESE algorithm retrieves finite ruptures from a seismic hazard input that sufficiently match the queried magnitude and hypocentral location. Applied to version 10.0 of the ISC-GEM earthquake catalogue, the method produced a publicly available database (GEESE version 1.0) of finite rupture models for past earthquakes.
Events with a moment magnitude greater than 7.0 and a hypocentral depth less than 200 km were selected. From these, the algorithm retrieved the best matching ruptures from GEM’s Global Hazard Mosaic, providing both rupture models and corresponding ground-motion fields. The OpenQuake format inputs (including the retrieved finite rupture) are provided for the user to perform their own scenario hazard calculations.
The database offers researchers and practitioners a resource for scenario-based hazard and risk analysis applications, helping to bridge historical seismicity with contemporary modelling needs.
Testing Models and Supporting Response
The GEESE algorithm can also serve as a tool for the verification of a model’s seismic source characterisation, given it can test whether a model can generate ruptures sufficiently representative of known events – with matching ruptures identified for approximately 90 percent of the ISC-GEM catalogue events tested. If no ruptures are retrieved, it can provide information on seismic sources which would be expected to be capable of generating a matching rupture based on the admitted information for the given earthquake.
The tool is also of considerable use in post-event response when initially only limited information is often available. Unlike other rupture retrieval algorithms in the literature, the GEESE algorithm is not dependent on additional data to obtain an initial finite rupture, because the geometries are determined by the predefined seismic sources within the seismic hazard input models. Examples of this capability are demonstrated for the 2023 Morocco earthquake and the 2023 Kahramanmaraş earthquake within the recently published journal paper about the GEESE algorithm and associated database.
Implications for the DRR Community
According to Christopher, the tool offers significant benefits for science and practice:
“With GEESE, we can generate finite ruptures for events of interest with minimal information - only the event hypocenter and moment magnitude, because we are leveraging the predefined geometries contained within OpenQuake format seismic hazard input models. This capability is highly useful in post-event response when consideration of a detailed geometry (as opposed to a more crude point source) within scenario risk calculations can significantly alter the suggested allocation of emergency response resources. The algorithm is also useful for evaluating the seismic source characterisations of OpenQuake format seismic hazard input models.”
The study reinforces GEM’s commitment to open science by making the GEESE algorithm and its rupture database publicly accessible. By providing finite rupture models and scenario hazard calculation input files for the largest events in the ISC-GEM catalogue, a systematic means of evaluating hazard models and a capability for retrieving initial finite ruptures in post-event response, the tool strengthens the resources available to the global disaster risk reduction community.
Accessing the Database
Version 1.0 of the GEESE rupture database is openly available under a CC BY-NC-SA license through GEM, offering finite rupture models and associated ground-motion fields for almost 1000 large historical earthquakes. This resource is intended to grow with further data and applications, enhancing global capacity for hazard testing and rapid post-event analysis. Explore the GEESE resources here.
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