GEM is an international forum where organisations and people come together to develop, use and share tools and resources for transparent assessment of earthquake risk. Discover GEM, the people and organisations driving the GEM Foundation, and learn how you can use the data, resources and tools as input to improved understanding, assessment and management of risk.
'Working together to assess risk' is our motto. We do this through international scientific consortia developing global best practice, datasets and tools, as well as through regional partnerships in all continents, collaborative projects, open-source software development, rigorous testing and knowledge sharing.
Transparency, credibility and collaboration are core values of GEM. Sharing as much possible as early as possible is key to that. In this section you can explore the different types of resources available for you to use, to share with others, or to promote GEM with.
Join GEM. Only by putting our expertise and data together can we increase resilience to earthquakes. There are many ways you or your organisation can get involved, from becoming a participant in the effort to sharing your expertise and data.
The ISC-GEM Global Instrumental Earthquake Catalogue (1900-2009) features:
events with magnitude >= 7.5, occured between 1900 and 1917
events with magnitude >= 6.25, occured between 1918 and 1959
events with magnitude >= 5.5, occurred between 1960 and 2009
The catalogue is composed of earthquakes with homogeneous locations and magnitude estimates, determined using the same tools and techniques to the extent possible. The magnitude determination and location procedures applied represent a synthesis of state-of-the art methods.
Each event has a Mw value, the magnitude type currently used in the engineering seismology community, where possible based on seismic moment (mainly earthquakes in the period 1976-2009). In other cases new empirical relations have been used to obtain proxy values of moment magnitude. In the early instrumental era (1918-1959) the catalogue contains about 1900 earthquakes with magnitude instrumentally determined, against – for example – about 900 events currently available in the Abe catalogue.
Who developed it?
The International Seismological Centre led a team of international experts in the field. Dmitry Storchak coordinated the project, with scientific input from Willie Lee. In addition, observers from IASPEI (Peter Suhadolc and colleagues from Japan, Germany, United States and the United Kingdom) oversaw the whole process. You can read more about the team in the final report (see sidebar).
How is it of relevance?
Seismic Hazard Assessment
A reliable earthquake catalogue is a highly critical component in any type of seismic hazard analysis. Because earthquakes are low frequency, high-impact events, the history of past events is of great importance for characterizing the seismic hazard in an area. Historical data from descriptions of earthquake events is commonly combined with more accurate instrumental data from when the first seismological equipment started being used in the early 20th century.
Only by working together on a global scale can earthquake hazard and risk assessment advance, as critical input for decisions to mitigate and reduce earthquake risk. The ISC-GEM catalogue provides a global starting point for continuous improvement of seismicity both for science and concrete applications.
What are its characteristics?
It covers 110 years of seismic history. In many developing and emerging countries there is a lack of long-term instrumental recordings and this catalogue currently offers the only long-term record of seismicity for calculating seismic hazard.
It is a truly instrumental catalogue in which the main earthquake parameters (location, depth and magnitude) are re-calculated based on the basic parametric seismogram readings of quality seismic stations worldwide.
It is homogeneous to a high degree, because the main earthquake parameters are calculated based on the same procedure. As a result, one can with a much higher degree of confidence than before compare the earthquake location and magnitude values in the first and second part of the 20th century.
The main earthquake parameters are furnished with estimates of uncertainty. Such information is not available in current catalogues. Uncertainty estimation improves the accuracy of (subsequent) seismic hazard assessment.
The magnitude computations, especially in the first part of 20th century, are based on a wealth of large new volumes of surface wave amplitude readings that were not globally available prior to this work.
Seismicity patterns are clustering out to reveal much finer earthquake occurrence structures that in view of earthquake’s self-repeating principle are seen as a confirmation of improved location of the event(s).
The ISC-GEM Catalogue can be used as reference for regional efforts of creating earthquake history. Basic parameters of moderate events in the regional catalogues will be calibrated based on those of ISC-GEM, creating vertical (in earthquake size) and lateral (between regions) homogeneity worldwide.
The approach taken in construction and compilation of this catalogue can be used as a model for regional efforts.
It provides references to all original sources, including scanned historical bulletin pages.
How is it different?
It comprises more events than current global instrumental catalogues
It goes far beyond a compilation and combination of existing catalogues, magnitudes have been recomputed using original amplitudes
It includes uncertainty estimation
It follows a standard methodology that is well documented and can be used and applied for regional catalogues
It combines knowledge and resources from around the globe and benefited from unique collaboration with scientists working on related topics, such as active faults
Hundreds of bulletins were processed for inclusion in the catalogue
Magnitudes are as much as possible featured as Mw values
The global project to produce a v1.0 of a global instrumental earthquake catalogue has now ended, but we are keen to hear from you at any time...
in case you possess or know of studies that could enhance the catalogue for specific earthquakes
about your experiences using the catalogue
for any other idea or questions
Send an email to firstname.lastname@example.org or use the site contact form.
The ISC-GEM Global Instrumental Earthquake Catalogue covers 110 years of seismic events in the world, bringing together over 20.000 events (of magnitude >= 5.5) in a homogeneous way. The catalogue can be used for seismic hazard calculations, reference at regional scale, understanding of seismic history, and as basis for future research.
Download the ISC-GEM Global Instrumental Earthquake Catalogue (1900-2009) Report
Take a look at the latest presentation on the catalogue (December 2012).