Abstract

Students are typically taught to locate earthquakes by deriving epicentral distances from S-P times. This activity replaces printed seismograms and travel time curves with Google Sheets/PowerPoint slides that they can manipulate themselves. First, students use seismograms that have vertical guidelines added to them, which they use to identify P- and S-wave arrivals. Next, after determining the S-P time for a station, they use a travel time graph with a vertical bar that can be adjusted to match the S-P time and then it can be moved so that its length spans the time between the S- and P-wave travel time curves, allowing students to read off the distance from the station to the earthquake. Once distances for three stations are determined, students use IRIS's Earthquake Triangulation tool to plot the distance circles and determine the earthquake's epicenter.

Context

This activity is part of the earthquakes lab for an introductory geology course at a community college.

Why It Works

Students can uses these tools to easily find the required data for earthquake location and it is easily used by students in an online course or if they are working at and do not have printed seismograms and travel time curves. For the instructor, it saves printing these files and can easily allow stations and/or earthquakes to changed.