Session 1 — Why Does the Earth Make Noise? — ESS 314: Introduction to Geophysics

Hook (0 – 7 min)

Show the IRIS MUSTANG global visualization of the 2011 Tōhoku earthquake — no audio, no explanation. Ask:

“What is this? What does a global seismogram record that a single station can’t?”

Pair-share 90 seconds. Take 3–4 responses without correcting them.

Discussion (7 – 42 min)

Central question: “Seismic waves travel through the entire planet in under 20 minutes. What does that mean for what we can learn about Earth’s interior — and for how fast we can warn people?”

Discuss ShakeAlert, currently deployed in the PNW. What wave physics does it use? What are its limits?
What would you need to improve it with what you’re learning this week?
Leave space for students to be wrong — explore the wrongness.

Open problem thread: Why is earthquake early warning still imperfect if seismic waves travel at known speeds? What would a perfect system require?

Relevance

Hazard: USGS estimates ~$15B annual US losses from earthquakes; 50% of US states have significant future shaking potential (USGS EHP Decadal Strategy, 2024). The wave physics from lecture is the foundation of every hazard tool.

Basic science: Everything we know about the liquid outer core and solid inner core came from seismic shadow zones — there is no drill that reaches it. The same waves that warn people about earthquakes also reveal the planet’s deep structure.

Go Deeper

IRIS “How Does a Seismometer Work?” animations · USGS ShakeAlert

One name to look up: Dr. Doug Given, USGS — ShakeAlert coordinator. What does his team’s day-to-day work look like?

Session 1 — Why Does the Earth Make Noise?

Session 1 — Why Does the Earth Make Noise?#