World map showing topography as well as bathymetry, or the depth of landforms below sea level
Submap is a user-friendly tool that allows anyone with an Internet connection to create quick, custom maps of subduction zones. This map shows bathymetry, or the depth of landforms below sea level, along with world topography. Credit:

Subduction zones are complex. But mapping them is now as simple as cropping a family photo.

That’s thanks to Submap, an online resource hosted by the University of Montpellier in France. The latest version was intentionally designed for a wide audience, suitable for students, teachers, and professional researchers. The fast, free service incorporates dozens of data sets and makes mapping available to anyone with an Internet connection.

“Everything is public. Everybody can use it,” said Serge Lallemand, a marine geodynamicist who helped develop the resource.

Graphic Design Meets Geoscience

Some of the deadliest disasters in recent history have occurred around subduction zones, including the 2004 Indian Ocean tsunami and the 2011 Tōhoku earthquake. But scientists are still distinguishing the phenomena that cause these catastrophes. The slow scrape of subducting plates occurs deep underground. Visualization tools like Submap can illuminate the process by creating maps and cross sections from multiple areas and angles.

The first version of Submap appeared online in 2009. In the years since, Lallemand and his research group have steadily published public data sets to improve the project. This spring, they went a step further and completely overhauled the website to make it more widely accessible. The new version debuted in June.

Submap has always been a public resource, said Lallemand. His lab group regularly adds and updates their findings and boosts the site with public data sets published by others. The modules include parameters that factor into the formation of giant tremors, like sediment thickness and seafloor roughness.

The user-friendly design was intentional, too, he said. The Submap team includes geoscientists and computer engineers but also a graphic designer. Although other mapping tools exist, Submap is unique in its user-friendly appearance, Lallemand said. The tools also include options for readers who are color-vision deficient, following inclusive recommendations from a 2020 Nature Communications perspective.

How to Map a Subduction Zone

A digitally created map of Central America showing red arrows for the direction and velocity of the subducting Cocos plate, red triangles for volcano locations, and hundreds of circles for earthquake locations shaded to represent depth of the quake epicenter
MAP-Geodyn creates fast and free maps of subduction geodynamics using public data. This map of Central America shows the epicenters and depths of all recorded earthquakes rated magnitude 5 or higher as yellow circles and volcano locations as red triangles, as well as the velocity and direction of the Cocos plate as it subducts beneath the Caribbean plate. Credit:

The Submap website features four tools, including MAP-Geodyn. The mapping service lets users simply drag and drop the corners of a square over a map of the world just like they’re cropping a photo. Users decide what parameters to visualize, like seafloor age or topobathymetry. They can pepper their map with volcano locations, earthquake epicenters, and subduction velocities. Users click “generate map,” and seconds later, Submap produces a custom graphic ready to download in multiple file formats.

A digitally created map of Japan shows black arrows for the direction of the subducting plate, green triangles for volcano locations, stars for epicenters of quakes, and colored patches for rupture areas. The subducting plate is also colored to indicate the roughness of the subducting seafloor.
MAP-Subquake visualizes seafloor roughness and earthquake locations. This MAP-Subquake graphic shows the epicenters and rupture areas of all subduction earthquakes rated magnitude 7.5 or higher off Japan since 1900. Black arrows indicate the direction of the Pacific plate (right) subducting beneath the Okhotsk (north) and Philippine (south) plates, green triangles identify volcano locations, stars identify epicenters of quakes, and colored patches indicate rupture areas. Credit:

The other three Submap tools are equally visual. SECTION-Geodyn creates cross sections of Earth’s crust up to 1,800 kilometers long. MAP-Subquake maps seafloor roughness against sites of major subduction earthquakes. Sub-DATA supplies parameters for trench transects around the world.

“It’s very, very thoughtfully designed,” said Margarete Jadamec, a geodynamicist at the University at Buffalo not involved in the project. The tools combine user-friendly layout with actual quantitative data, she said, which meets the needs of several audiences. The program is a valuable teaching tool for students, a vital time-saver for researchers, and an important avenue for science communication.

“Submap is done in such an intuitive way that it has the ability to reach beyond just the scientific community and to really reach the broader public.”

“Submap is done in such an intuitive way that it has the ability to reach beyond just the scientific community and to really reach the broader public,” she said.

Although the Submap site is active and ready to use, Lallemand and his colleagues continue to add to and enhance the data. He’s currently researching kinematic parameters for areas with multiple microplates. His students are examining variations among arc volcanoes. Any results will be published open-access and added to the project.

For now, Lallemand wants researchers to try the tools, get ideas, and deliver feedback. Comments are welcome, he said. Every suggestion and contribution improves the project and increases the public understanding of these potentially catastrophic rupture sites.

—J. Besl (@J_Besl), Science Writer

Citation: Besl, J. (2023), A new, underground atlas of subduction zones, Eos, 104, Published on 28 August 2023.
Text © 2023. The authors. CC BY-NC-ND 3.0
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