# Visualizing Earthquakes at Convergent Plate Margins

Cara Harwood
,
University of California, Davis
This activity is part of the Global Earthquakes: Teaching about Earthquakes with Data and 3D Visualizations series.
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#### Summary

In this activity students visualize the distribution and magnitude of earthquakes at convergent plate boundaries. Earthquakes are visualized on a 3D globe, making it easy to see their distribution within Earth's surface without having to mentally transform and interpret symbols that indicate earthquake magnitude and hypocenter depth.

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## Context

#### Audience

Introductory-level undergraduate earth science class, although talking points could be adapted for younger students by giving more background.

#### Skills and concepts that students must have mastered

Students should understand that convergent boundaries occur where plates are moving together. Students should also be familiar with elements of the visualization (introduced in Visualization 1; i.e. how earthquakes are represented, what different sizes and colors of points represent) and have mastered the concepts associated with Visualization 1.

#### How the activity is situated in the course

This activity is part of a series of visualizations in a unit about plate tectonics, although each visualization could also be used in isolation.

## Goals

#### Content/concepts goals for this activity

Students will understand the following concepts:
• Deep, large magnitude earthquakes commonly occur at convergent plate boundaries.
• Earthquakes at convergent plate boundaries are distributed with predictable locations and depths.
• There are two different types of convergent margins that have different types of earthquakes associated with them.
• Earthquakes at subduction zones occur as one tectonic plate slides under another; the downgoing plate bends and shears along the base of the overriding plate. The downgoing plate grinds along the overriding plate, which generates large earthquakes.
• The position and depth of earthquakes at subduction zones is determined by the angle of the downgoing plate. Therefore, the position and angle of the downgoing plate can be determined by the position of earthquakes.
• Earthquakes occur down to a maximum depth of about 600 km; below this depth the crust is hot enough that it no longer behaves in a brittle way.

#### Higher order thinking skills goals for this activity

Students will be able to:
• Synthesize large data sets to recognize naturally occurring patterns
• Use patterns in data sets to make predictions about the distribution and characteristics of earthquakes
• Visualize data in 3D that is traditionally represented in 2D

## Description of the activity/assignment

This screenshot shows the Fiji subduction zone, one of the featured convergent margins in this visualization. The visualization shows how earthquakes at this margin occur at depth, and define the slope of the subducting plate. This visualization also includes other examples of subduction zones and continental convergent margins (Himalayas). Click the image to enlarge or view the MP4 movie (MP4 Video 30.3MB Dec20 11).
The purpose of this activity is to introduce students to the distribution and characteristics of earthquakes associated with convergent plate boundaries. Students will learn about how the magnitude and distribution of earthquakes at convergent boundaries are related to processes that occur at these boundaries and to the geometry and position of the two converging plates. Because the depth of earthquakes can be difficult for students to visualize in 2D representations, this activity allows students to visualize the 3D distribution of earthquakes within Earth's surface, which is essential for understanding how different types of earthquakes occur in different tectonic settings. Locations featured in the visualization include the Chile-Peru Subduction Zone, the Aleutian Islands, the Fiji Subeuction Zone, and the Himalayas. Talking points and questions are included to use this visualization as part of an interactive lecture. In addition to playing back the visualization, instructors can also download the visualization software and data set and explore it themselves.

## Determining whether students have met the goals

'Quakes Questions' throughout the activity are short-answer questions that students answer while the visualization is playing to ensure that they are taking away key concepts. The final 'Quakes Question' requires them to synthesize ideas from this visualization and from 'Visualization 2: Earthquakes and Convergent Plate Boundaries.'

## Teaching materials and tips

• Instructors Notes (Acrobat (PDF) 196kB Sep11 12) This document includes detailed description of the visualization and how it should be used in class, talking points that are linked to specific times in the visualization, and 'quakes questions' for evaluation during playback of the visualization.

## Other Materials

• Click to see the video
Convergent Boundaries Visualization Movie (MP4 Video 30.3MB Dec20 11) Playback time 6 minutes 14 seconds. MPEG-4 movie. Includes overview of earthquakes at convergent plate boundaries, and features the Chile-Peru Subduction Zone, the Aleutian Islands, the Fiji Subduction Zone, and the Himalayas.

## Supporting references/URLs

The visualization software used to create this visualization is freely available and can be downloaded from http://keckcaves.org/education/. In addition to playing back the visualizations available here, instructors can also download the visualization software and data sets and explore it themselves. Download the software and quick-start guide to begin exploring your own data sets in your classroom.

Please contact the author (clharwood@ucdavis.edu) if you would like a higher resolution video.