News broadcasts showing collapsed buildings, broken bridges and smashed cars help middle school students visualize the hazardous nature of earthquakes. However, students struggle with understanding how scientists can tell exactly when and where a rupture has occurred because earthquake faults so rarely rupture the surface of the earth and few students understand how scientists investigate earthquakes through analysis of data collected using technology devices (i.e., seismometers) from around the world. The Flash-based Epicenter Location Tools (FELT) were developed in consultation with Dr. Debi Kilb, Director of the Visualization Center at Scripps Institution of Oceanography, UCSD, to bring authentic scientific experiences into sixth grade science classrooms.
FELT consists of three exercises with progressive levels of difficulty. All three exercises use the same collection of data regarding seismic stations and recent seismic activities that have been made available to the public by the Incorporated Research Institutions for Seismology. Students will first be given a list of recent earthquakes from which they can select an earthquake of their interest. Once an earthquake is selected, students will be presented with a collection of seismic stations on a Google Map interface so that further exploration on seismograms recorded by those stations can be conducted. The triangles are used to represent seismic stations.
Exercise #1
This exercise focuses on helping students recognize the fact that three seismic stations are needed to pin-point the epicenter of an earthquake. By clicking on the triangles (seismic stations), students will have a chance to answer questions with regards to how seismic stations help identify epicenters. For each triangle (station) a student clicks, FELT will draw a circle using the distance between the epicenter and the station as its radius. Only after three stations have been clicked will the software identify the epicenter of the earthquake.
Exercise #2 (A Demo)
This exercise allows students to explore actual seismograms recorded at the stations. For each station, students are asked to move two vertical bars along the seismogram to mark the arrival of the Primary (P) and Secondary (S) wave front. Visual and audio hints are provided for students to correctly place the marks. Since FELT purposely selects stations that are azimuthally well distributed around the earthquake epicenter, students will have the opportunity to compare and contrast seismograms for the same earthquake that are recorded at different stations. Once students complete the marking of the P- and S-wave arrivals on a seismogram, FELT will calculate the distance between the epicenter and the station based on the time associated with the markings and draw a circle on the Google Map interface accordingly. When three stations have been explored, students will see an epicenter icon appears on screen. If the icon is moved by students to the actual epicenter of the earthquake, a customized certificate will be presented.
Exercise #3
This exercise further challenges students on the subject of epicenter identification. Similar to the second exercise, students will be asked to move the two vertical bars on seismograms to mark the P- and S-wave arrivals. Instead of having the computer calculate and display the distance between the epicenter and the station based on the time associated with the markings, students will be required to perform the calculation and determine the distance. In addition, students will need to adjust the size of the circle on the Google Map interface to match the distance they determine.
