About Worldwide Earthquake Map
FM Global is dedicated to helping its clients manage their risk and ensure operating resilience. We have conducted extensive research, building on the data and experience of noted governmental and research organizations, to create the FM Global Worldwide Earthquake Map that identifies seismic risk.
Understanding of earthquake hazard (the strength of bedrock shaking) and earthquake risk (how shaking affects the built environment at a particular site) is continually evolving and improving due to:
- Better earthquake source data (e.g., active faults and historical earthquake catalogs), modeling methodology, and ground motion prediction equations that more accurately represent how shaking changes as it radiates away from the earthquake source.
- Revised methods to extract local site (soil) conditions from general geologic data, and updated factors that more accurately account for amplification of bedrock shaking by those local site conditions.
- Studies that allow development of improved methods to model the vulnerability of structural systems and nonstructural components to shaking.
The Worldwide Earthquake Map is based largely on the global mosaic of seismic hazard models created by the Global Earthquake Model (GEM) Foundation, of which FM Global is a partner. The GEM Foundation global mosaic provides the most consistent and widely recognized understanding of worldwide seismic hazard currently available. In addition, the FM Global map accounts for the amplifying effects of local site soils by incorporating detailed and accurate data from worldwide soil maps (developed and collated by FM Global from geology maps) supplemented by local or national soil models, and the most recent site (soil) amplification factors. Finally, the structure shaking vulnerability threshold used to define earthquake zones is representative of a broad range of weak buildings consistent with the GEM damage functions for global building types. Note that GEM hazard models are sometimes supplemented, and GEM damage functions verified, by FM Global Research scientists based on their expert knowledge.
Using the most up-to-date hazard, soil, and vulnerability data affords us the opportunity to evaluate our earthquake zones such that they provide an entirely consistent understanding of earthquake risk worldwide.
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Earthquake Zone Legend
FM Global earthquake zones are based on the mean return period of “damaging” ground motions. Shaking is “damaging” when it is strong enough to cause non-trivial damage to structures and contents that are not properly designed to resist earthquake forces. However, the shaking intensity within a zone at that return period could be much higher than this threshold level. The FM Global Worldwide Earthquake Map displays zones conveying the mean return period of damaging ground motions at a site, not the mean return period of earthquakes at the site.
For each FM Global earthquake zone, the following table presents three equivalent ways of conveying the earthquake risk: 1) the mean return period of damaging ground motions, 2) the probability that damaging ground motions will occur in any year (i.e., annual probability), and 3) the chance that there will be one or more occurrences of damaging ground motions within a 50-year facility life.
FM Global Earthquake Zones
Damaging Earthquake Ground Motions
Zone
Relative Risk
Worldwide Earthquake Map Legend
Mean Return Period
Annual Probability
Chance of at Least One Occurrence in a 50-Year Facility Life
50-year
Severe
Dark Blue
0 to 50 years
≥ 2%
> 63%
100-year
High
Red
51 to 100 years
1% to 2%
39-63%
250-year
Moderate
Orange
101 to 250 years
0.4% to 1%
18-39%
500-year
Moderate
Light Green
251 to 500 years
0.2% to 0.4%
10-18%
>500-year
Low
White
>500 years
< 0.2%
< 10%
The mean return period of an event (e.g., damaging ground motion) is the average number of years between successive events. A mean return period of 500 years does not imply that successive events will be exactly 500 years apart. Nor does it imply that there is 100% probability of its occurrence in a 500-year period. This concept can be effectively illustrated by comparison to rolling a 6-sided die. There is a one-in-six chance of rolling a “3” (a “return period” of 6); however, in six rolls of the die, it is possible that a “3” will not be rolled and it is also possible that a “3” will be rolled more than once.
Each FM Global earthquake zone is named by a single return period of damaging ground motion but encompasses a range of return periods (or the corresponding annual probabilities), as shown in the table. The return period of damaging ground motion in, for example, a >500-year earthquake zone may be only slightly more than 500 years. Earthquake zone boundaries must be drawn somewhere, but it should be recognized that crossing a zone boundary does not necessarily represent a large “jump” in the earthquake risk. If future earthquake zone boundary revisions place a location in a different earthquake zone, this may represent a relatively modest change in the actual risk.
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Frequently Asked Questions
Q: How is the FM Global Worldwide Earthquake Map different from other earthquake maps?A: Although the underlying science of the seismic hazard calculations used by building codes and FM Global are largely the same, the two map different parameters.
Building codes map seismic hazard, that is, the underlying bedrock shaking determined based only on seismicity (the first point above). Site (soil) condition, and structural and nonstructural vulnerabilities, are accounted for via calculations, not directly in the maps. Building code maps typically display earthquake zones or accelerations in bedrock for a single return period, often 475 years or 2475 years. Because the mapped parameter, the return period, and the definition of bedrock can vary from country to country, the bedrock seismic hazard in building code maps is not easily compared worldwide.
By contrast, FM Global maps earthquake zones that directly display seismic risk, accounting for parameters in all three points above (seismicity, site [soil] condition and vulnerability). FM Global zones convey the mean return period of earthquake shaking, including the amplifying effects of local soil, that may cause non-trivial damage to structures if they are not properly designed to resist earthquake forces. Contents and nonstructural components may also be damaged at this level of shaking. FM Global earthquake zones are developed using the same methodology worldwide, allowing easy comparison of earthquake risk across the globe.
Q: How should the FM Global Worldwide Earthquake Map be used?A: The FM Global earthquake zone indicates a location’s seismic risk. For 50-year through 500-year earthquake zone locations, FM Global recommends that their clients implement earthquake design and protection provisions at least as strict as those specified in FM Global Property Loss Prevention Data Sheets. Several data sheets exclusively address earthquake:
- Data Sheet 1-2, Earthquakes
- Data Sheet 1-11, Fire Following Earthquakes
- Data Sheet 2-8, Earthquake Protection for Water-Based Fire Protection Systems
Earthquake protection guidance specific to certain subjects, equipment, or occupancies is also contained in other FM Global Property Loss Prevention Data Sheets (e.g., Data Sheet 10-2, Emergency Response and Data Sheet 3-2, Water Tanks for Fire Protection). Register to receive FM Global data sheets at fmglobal.com/datasheets. FM Global further recommends that their clients choose products appropriate for use in earthquake zones (e.g., steel suction tanks) or that can be used to provide earthquake protection (e.g., seismic sway brace components for sprinkler piping). Information regarding Approved products can be found in our Approval Guide at fmapprovals.com/approval-guide.
Earthquake design provisions in the local building code may be more restrictive than those contained in FM Global Property Loss Prevention Data Sheets in certain cases (e.g., local codes may require earthquake design in some FM Global >500-year earthquake zones). Where this occurs, the local building code provisions should be followed.
Q: How was the FM Global Worldwide Earthquake Map developed?A: A team of public, private, academic, and non-governmental organizations worldwide are collaborating on a Global Earthquake Model (GEM) mosaic hazard model by collating available and newly-created regional and national seismic hazard models. FM Global uses the available GEM hazard models and GEM’s OpenQuake software to calculate earthquake ground motions in bedrock for multiple return periods for most countries and regions. We have used alternate or supplemental seismic hazard information for China, the United States, Greenland, Singapore, Canada, and some small islands. In China, for example, a hazard model co-developed by FM Global and the Institute of Geology of the China Earthquake Administration is used; and the 2018 United States Geological Survey (USGS) national seismic hazard maps replace the GEM hazard model for the U.S.
Soil amplifications are included in developing FM Global earthquake risk zones, classified using the United States National Earthquake Hazards Reduction Program (NEHRP) soil categories, defined in terms of Vs30 (the average shear wave velocity in the top 30 meters). It is impractical to measure Vs30 at a global scale, so two proxies are used: geology (rock or sediment type and age) as developed by the California Geological Survey supplemented in limited areas by topographic slope as developed by the USGS. Detailed geology and slope data from thousands of digital geology maps and from national soils models are used to assign soil classes on a maximum 1 km x 1 km grid worldwide, with an even finer soils grid in certain areas. Because soils at a location have a significant and direct impact on shaking levels and resulting damage, this level of detail is key to accurately quantifying the risk.
The final step in developing FM Global earthquake risk zones is to compare, at each location for each return period, the soil-amplified ground motions with the shaking that may result in non-trivial damage to structural and nonstructural components lacking earthquake protection. The threshold at which non-trivial damage occurs is based on hundreds of GEM damage functions for a broad and international range of building types, validated with data from structural and non-structural experimental shake table tests. From this comparison the final overall zone map can be generated.
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Excluded Features
The FM Global Worldwide Earthquake Map displays only the risk due to shaking. Secondary hazards, such as liquefaction, settlement, landslide, fault rupture, and tsunami are not considered.
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Data Sources
General:Allen, T. and Wald, D., 2007. Topographic slope as a proxy for seismic site-condition (Vs30) and amplification around the globe, U.S. Geological Survey, Open File Report 2007-1357.
ASCE 7, Minimum Design Loads and Associated Criteria for Buildings and Other Structures, 2016. Reston, Virginia: American Society of Civil Engineers.
FEMA P-1050-1, NEHRP Recommended Seismic Provisions for New Buildings and Other Structures, 2015. Washington, D.C.: Building Seismic Safety Council (BSSC) of the National Institute of Building Sciences (Institute) for the Federal Emergency Management Agency (FEMA) National Earthquake Hazards Reduction Program (NEHRP).
Wills, C. and Silva, W., 1998. Shear Wave Velocity Characteristics of Geologic Units in California, Earthquake Spectra, vol. 14, pp. 533-556.
Wills, C. and Clahan, K., 2006. Developing a map of geologically defined site-condition categories for California, Bulletin of the Seismological Society of America, 96, 1483-1501. doi: 10.1785/0120050179
GEM and OpenQuake:D’Ayala, D., Meslem, A., Vamvatsikos, D., Porter, K., Rossetto, T., 2015. Guidelines for Analytical Vulnerability Assessment of Low/Mid-Rise Buildings, Global Earthquake Model, Vulnerability Global Component.
Global Earthquake Model Foundation. [Online]. https://www.globalquakemodel.org/ (incorporating data through 2019).
Pagani, M., Monelli, D., Weatherill, G., Danciu, L., Crowley, H., Silva, V., Henshaw, P., Butler, L., Nastasi, M., Panzeri, L., Simionato, M. and Vigano, D., 2014. OpenQuake engine: An open hazard (and risk) software for the Global Earthquake Model, Seismological Research Letters 85, 692-702.
China Earthquake Risk Map:Chen, G., Magistrale, H., Rong, Y., Cheng, J., Binselam, S.A. and Xu, X., 2019. Seismic site condition of mainland China from geology. Seismological Research Letters, in press.
Cheng, J., Rong, Y., Magistrale, H., Chen, G. and Xu, X., 2017. An Mw-based historical earthquake catalog for mainland China, Bulletin of Seismological Society of America 107, 2490-2500.
Cheng, J., Rong, Y., Magistrale, H., Chen, G. and Xu, X., 2019. Earthquake rupture scaling relations for mainland China, Seismological Research Letters, 91 , 248-261.
Dangkua, D.T., Rong, Y. and Magistrale, H., 2018. Evaluation of NGA‐West2 and Chinese Ground‐Motion Prediction Equations for Developing Seismic Hazard Maps of Mainland China, Bulletin of the Seismological Society of America 108, 2422-2443.
Rong, Y., Pagani, M., Magistrale, H. and Weatherill, G., 2017. Modeling seismic hazard by integrating historical earthquake, fault, and strain rate data, in The Proceedings of the 16th World Conference on Earthquake Engineering, Santiago, Chile.
Rong, Y., Shen, Z.-K., Chen, G. and Magistrale, H., 2018. Modeling strain rate and fault slip for China and vicinity using GPS data, Abstract T22A-01, presented at 2018 Fall Meeting, AGU, Washington D. C., 10-14 Dec.
Rong, Y., Xu, X., Cheng, J., Chen, G. and Magistrale, H., 2019. A probabilistic seismic hazard model for mainland China, Earthquake Spectra, 36 , 181-209.
U.S. Earthquake Hazard:Petersen, M. D., Shumway, A. M., Powers, P. M., Mueller, C. S., Moschetti, M. P., Frankel, A. D., Rezaeian, S., McNamara, D. E., Luco, N., Boyd, O. S., Rukstales, K. S., Jaiswal, K. S., Thompson, E. M., Hoover, S. M., Clayton, B. S., Field, E. H., and Zeng, Y., 2019. The 2018 update of the US National Seismic Hazard Model: Overview of model and implications, Earthquake Spectra 36, 5-31.
Greenland Earthquake Hazard:Rong, Y., and Klein, E., 2020. A probabilistic seismic hazard model for Greenland, Research Technical Memorandum, FM Global, Norwood, MA.
Singapore Earthquake Hazard:Megawati, K., and Pan, T.-S., 2010. Ground motion attenuation relationship for the Sumatran megathrust earthquakes, Earthquake Engineering and Structural Dynamics 39, 827-845.
Canada Earthquake Hazard:Adams, J., Halchuk, S., Allen, T., and Rogers, G. 2015. Canada’s 5th Generation seismic hazard model, as prepared for the 2015 National Building Code of Canada, In Proceedings of the 11th Canadian Conference on Earthquake Engineering, Victoria, BC, Canada, 21–24 July, paper 93775.