How do earthquake early warning systems work?

Amy Nordrum describes the array of seismic sensors that alerted Mexico before a 7.1 magnitude earthquake hit.

Vocabulary: earthquake, seismic waves, p-waves, s-waves

Next Generation Science Standards: ESS3.B: Natural Hazards, ESS2.B: Plate Tectonics and Large-Scale System Interactions, CCC1: Patterns, and SEP1: Asking Questions and Defining Problems. Can be used to build towards MS-ESS2-2, MS-ESS3–2, and HS-ESS3–1.

Common Core State Standards: CCSS.ELA-LITERACY.RI.6.1, CCSS.ELA-LITERACY.RI.7.1, CCSS.ELA-LITERACY.RI.8.1, CCSS.ELA-LITERACY.RI.9–10.1, CCSS.ELA-LITERACY.RI.11–12.1

On September 19, 2017, a 7.1 magnitude earthquake hit areas of Mexico, including the capital Mexico City. Though the quake resulted in the death of over 200 people and damage to countless buildings, Mexico’s network of seismic sensors alerted people before the quake began, potentially saving countless lives.

Audio Excerpt “Mexico’s Earthquake Early Warning System,” Sept. 22, 2017. (Original Segment)

Questions

• Draw a diagram that shows how p-waves and s-waves are detected by the sensors and by people.
• Mexico installed these sensors, despite their expense. What do you think prompted them to take this action?
• The warning was issued 30–60 seconds before the earthquake. Why does Amy still think that this was a success, even with such short notice? What would you advise people to do during that time?
• What are two things you want to know about these sensors and how they function?

AntoFran Derivative work: Fuzheado/CC BY-SA 4.0/ Wikimedia Commons

Activity Suggestions

• Have students build instruments to help visualize seismic activity with this coding activity where students construct a seismograph and use big data to develop an understanding of plate tectonics. Have them read more about Shake Alert, the USGS project to put seismic sensors on the west coast.
• In this activity have students build and explore a mechanical model of a fault to learn how energy is stored elastically in rocks and released suddenly as an earthquake. This activity is part of a complete lesson plan with support materials available from the Incorporated Research Institutions for Seismology (IRIS).

Additional Resources

• Read Amy’s article on earthquake sensor arrays.
• Crowdsourcing earthquake detection? Yep, there’s an app for that.
• Take a look at Mexico City before and after the earthquake.
• Take a look at the USGS Shake Map for the September 2017 earthquake.