Focus Question: HOW CAN WE LOCATE THE EPICENTER OF AN EARTHQUAKE?

Is caused by an an earthquake under the ocean TSUNAMI Is caused by an an earthquake under the ocean

Formation of a tsunami

Tsunamis

Seismographs Allow us to measure Seismic Waves and study earthquakes

Both travel faster as the pressure or density increases They travel faster (and take less time) They travel slower (and take more time) Both travel faster as the pressure or density increases They can travel through any type of material They can travel only through solids They cause a vibration perpendicular to the direction of movement of the waves They cause a vibration parallel to the direction of movement of the waves

The velocity for both P and S-waves increases The velocity for both P and S-waves decreases

Seismic Waves Primary/compressional waves (P): travel faster through solids, liquids, gases, and plasma arrive first Secondary/Sheer/(S): travel slower through solids only arrive second Surface waves: most destruction

The farther away a seismograph is from the epicenter, the longer the difference between the arrivals of the P- and S- waves

The smaller the difference in arrival time between P & S; Farthest Closest The smaller the difference in arrival time between P & S; The closer the station to the epicenter

20 Seconds 200 Km

Question 1 Classwork P waves 5 min S waves 9 min Difference 4 min

Question 2 4,200 Km

Question 3 4, 800 Km

Question 4 9 min 40 sec

Question 5 S waves 12:40 P waves 7:00 Diff 5 min 40 sec

One seismic station report allow us to find the distance to the epicenter As the distance from the epicenter increases, the difference in arrival time increases The average velocity: distance ÷ time

How is an Earthquake’s Epicenter Located?

How is an Earthquake’s Epicenter Located? Three seismograph stations allow us to locate the epicenter of an earthquake A circle represents each station The intersection of the 3 circles locates the epicenter

Triangulation of 3 stations to locate earthquake epicenter

Earthquake time & Arrival Time (P & S Waves) Arrival time: Earthquake origin time + P/S travel time Earthquake Origen time: P/S arrival time – P/S travel time

Locating an Earthquake

Time-Travel Curve

Locating an Earthquake Epicenter Triangulate means to use three positions to determine an exact location.

Locating Earthquakes