E
E
1.26 in
400/1.26=317.46km/inch
E=35.5 N 119 W

Determining the Epicenter Using 3 Seismographs
Michelle Veitz
This study determines the exact epicenter of a fictitious earthquake. Using 3 different seismograph reports from three locations (Albuquerque, Boise and Sacramento) and a map, we are able to pinpoint the exact epicenter. The epicenter was estimated to be 35.5 degrees North latitude and 119 degrees West longitude.

Partial information was provided in a grid format regarding seismographic data of 3 locations. Using a seismograph report from location Albuquerque, Δt was determined. Using Vp and Vs provided, tp and distance to the epicenter was determined using formulas provided by the professor. After determining a scale for the map, the radial distance was determined by dividing the distance to the epicenter by the appropriate scale. Circles were placed around each location based off of those calculations. At the intersecting point of all three circles is the epicenter for this particular earthquake. These calculations are found in the grid below.
Using a measurement of 24 seconds per tic mark on the seismograph, 96 seconds was used as the Δt for Albuquerque. Δt was given as 79.58 sec for Boise and 30.96 for Sacramento. Vp was given as 6.01 km/sec and Vs was given as 4.1 km/sec. Using the formula, tp = (Vs * ∆t) / (Vp – Vs), tp was determined for all 3 locations. Using formula Dist. = Vp km/sec * tp sec, the distances to the epicenter was calculated from each location. After determining my map was 400 km/1.26’’, the radial distances were calculated and mapped and found a connection point of all 3 circles at roughly 35.5 North latitude and 119 degrees West longitude.