1. Recording earthquake motion & identifying seismic waves

2. Seismograph: The instrument Apparatus to measure and record vibrations Seismogram: The actual wiggle Record of an earthquake recorded by a seismograph The difference between a “Seismograph” and a “Seismogram” FuturePast

3. P-waves S-waves Surface waves

4. P-waves primary wave compression wave fastest of the seismic waves can travel through solids, liquids, and gases Surface waves 2 types: Love waves and Rayleigh waves Slowest seismic waves May cause the greatest damage in an earthquake S-waves secondary wave shear wave second-fastest seismic wave can only travel through solids Seismic waves

5. Travel time from San Diego to Los Angeles 25 seconds P-waves 25 seconds 41 seconds S-waves 41 seconds 50 seconds Surface waves 50 seconds

6. Types of Seismic Waves: P-wave, S-wave, surface wave P and S waves travel through the Earth (and even into the core!) Surface waves travel along Earth’s surface

8. Seismic data can also be used to learn about Earth

9. USArray Transportable Array 9

10. Looking at seismic data: the ANZA network

11. Screenshot of ANZA (southern CA) data: November 26, 2009 24 hours

12. 2:00am PST Trucks? Content from the ANZA network http://eqinfo.ucsd.edu/faq/traffic.php Seismologists record the motion of the ground to look for earthquakes, but plenty of other things cause the ground to move as well! What do you think the spikes in this image are caused by?

13. 8:00am PST Note the much higher noise amplitudes – this makes it difficult to pick out small earthquakes! Content from the ANZA network http://eqinfo.ucsd.edu/faq/traffic.php

14. Middle of the night Commute traffic! Content from the ANZA network http://eqinfo.ucsd.edu/faq/traffic.php

15. Content from the ANZA network http://eqinfo.ucsd.edu/faq/traffic.php This image shows an earthquake record. Note the numbers on the vertical axis. How does the maximum value compare to the noise seen in previous slides?