The Seismic Gap Hypothesis

Walter Szeliga
Central Washington University, Geological Sciences
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Using actual earthquake data from the circum-Pacific region, students make predictions about where earthquakes should occur in the immediate future. Data are provided in the form of global earthquake locations over 30 year time spans from 1900–2015. Students form groups and use one map to predict where earthquakes should occur during the subsequent 30 year interval. Students then compare their predictions to actual earthquake locations.

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Learning Goals

Student should gain an appreciation for the patterns of earthquakes over the century time-scale. Students should also develop thinking related to earthquake occurrence and the biases in making predictions based on pre-selected data.

Context for Use

This activity has been used in a small classroom setting (<30 students) with the data plotting and collection being completed in one 50 minute class period. Since this is a somewhat social activity, students are given additional time to complete their assignment and clean up their interpretation before handing it in. A basic understanding of how earthquakes occur and the spatial footprint of earthquake rupture is essential. This is typically the first assignment in an early upper-division tectonics course.

Description and Teaching Materials

Students form groups and use the large-scale maps provided in class to classify circum-Pacific faults based on the last time they experienced and earthquake. Each group is assigned a time-period as their starting period and then uses a classification scheme based on a simplified scale taken from "Seismic Gaps and Plate Tectonics: Seismic Potentials for Major Boundaries" by McCann et al., 1979. Student then make predictions about where they believe earthquakes are likely during the period subsequent to their starting time period. Students then switch maps and compare their predictions with actual earthquakes from the period subsequent to their starting period.
Seismic Gap Activity Student Handout (Acrobat (PDF) 23kB May2 19)
Global Seismicity 1900-1930 (Acrobat (PDF) 1.4MB May2 19)
Global Seismicity 1930-1960 (Acrobat (PDF) 1.4MB May2 19)
Global Seismicity 1960-1990 (Acrobat (PDF) 1.4MB May2 19)
Global Seismicity 1990-2015 (Acrobat (PDF) 1.4MB May2 19)

Teaching Notes and Tips

Getting students to suspend knowledge and avoid predicting earthquakes in locations that they know have had earthquakes is tricky. Part of the goal of this activity is to use only knowledge one could have had during the time period to make predictions. Depending on the organization of students and the layout of the classroom, plotting the data and sharing the maps can be a bit hectic.


Students are asked to explain their prediction methodology and the outcome of their predictions. Students are assessed on the clarity of the explanation of both the methodology and the outcome. Students are also asked to make predictions for the future.

References and Resources