Locating Earthquake Epicenters 1) Find p-wave and s-wave arrival times

2) Subtract p and s wave arrivals (Go to p. 11 ESRT) 3) Use scrap to mark the difference (00:01:30) on the Y axis. Slide until the bottom mark touches the P line and top mark touches the S line. 5) Go to the map!!! 4) Drop Down to read the Epicenter distance. Subtract  Mark  Slide Drop Down

a) Mark Radius for each city (1000 km) b) Make circle with compass c) Intersection triangle is where the earthquake happened

Origin Time Practice #1: Kyle arrived at school at 8:03:00 am. It took him 00:08:20 (8 minutes 20 seconds) to walk to school. What time did Kyle leave his house?   Practice #2: An earthquake p-wave arrived at 11:23:00 pm. The p-wave travel time was 00:03:20. What time did the earthquake originate?   **In order to calculate origin time you must subtract the p-wave travel time from the p-wave arrival time.**

6) Find Origin Time (should be the same for all 3 locations) P wave arrival(00:01:00) – P travel (?) Origin time How do I find the P travel time? Use epicenter distance (1000 km) scroll up to P line… head over to Y axis and read the P travel time. (00:02:20)

Recap 1) Find P and S wave arrival times 2) Subtract arrival times (go to page 11 ESRT) 3) Mark the difference. Slide until it’s snuggled between both P and S lines 4) Drop down to read epicenter distance. 5) Go to the map: radii (3), draw circles (3), x marks the spot! 6) Origin Time: P arrival – P travel*. Use epicenter distance, scroll up to P line…head over to Y axis, and read P travel time.