Department of Earth Science |Northeastern Illinois University

ESCI 121, Fall 2006

Daily Objectives #19  (October 31, 2006)                                                                        Dr. Sanders

By the end of today’s class, you should be able to do the following:

*  Describe how a seismograph works, and explain why every seismic monitoring station actually has three seismographs.

*  Tell how P-waves and S-waves differ in terms of velocity, the way they travel, and whether or not they can travel through liquids.

*  Explain how earthquake waves helped us learn that the outer core is liquid, using the term S-wave shadow zone.

* Explain the significance of the P-S lag.

* Given the velocity of P-waves and S-waves, calculate how long it would take each type to travel a given distance (e.g. 100 miles).

* Given data on the arrival times of P-waves and S-waves at several seismic monitoring stations, calculate the P-S lag.

* Given the P-S lag for an earthquake detected at several seismic monitoring stations, calculate how far from each station the epicenter was.

* Given the distance to the epicenter of an earthquake detected at several seismic monitoring stations, locate the epicenter.

*  Explain why it is necessary for you to have measurements from at least three seismic monitoring stations to find the epicenter of an earthquake.

Homework #3:  Due November 2, it requires you to use latitude and longitude, and to know what east and west mean in that context.  If you're uncomfortable with these concepts, you'll need to learn them on your own before doing the homework.  See p. 684-5 in your text.

Department of Earth Science | Northeastern Illinois University
© 2006 Laura L. Sanders.  Last updated October 31, 2006.