geology lab materils (2)

How Seismic Waves Travel Through Earth | Activity 11.2 Name: Course/Section: Date: Lea rning GOAL You will use travel-time data from an actual earthquake recorded by several seismograph stations to construct travel-time curves for P-, S-, and surface waves. Data from five seismograph stations that recorded a magnitude-7.2 earthquake on May 6, 2019, are given in Fig. A11.2.1. The earth- quake focus was ~127 km below eastern Papua New Guinea, with an epicenter location of 7.0°S, 146.6°E. Travel times for the first arrival of P-, S-, and surface waves are given in decimal minutes to make it easier to plot the data on a travel-time graph. Station Location of Distance To Travel Times (Minutes) ID Seismograph Station Epicenter (km) | P-wave | S-wave | Surface wave PMG | Port Moresby, Papua New Guinea 281 0.7 1-3 -- HNR | Honiara, Solomon Islands LS 3.2 5.6 6.5 - WRAB | Tennant Creek, Australia 1943 3.9 7.0 8.3 DAV | Davao, Philippines 2763 52 9.4 11.9 NWAO | Narrogin, Australia 4128 7.0 12.6 17.8 » 215 15 3 1= E (] E © > ® 10 10 = 5 5 0 0 0 1000 2000 3000 4000 5000 Distance to epicenter (kilometers) Figure A11.2.1 A Plot the travel-time data on the graph in Fig. A11.2.1. 1. Use the distance to the epicenter and the travel times to plot the first arrivals for each of the seismograph stations listed in the table. Use a pencil as you plot each point carefully, using the grid lines to assist you in interpolating the point location on the graph. 2. Notice that the points associated with each of the seismic-wave types seem to plot along a line or curve across the graph, so there seems to be a systematic increase in travel time with increasing distance from the epicenter. Lightly sketch a line or curve through the data points you plotted for each type of seismic wave—three lines/curves in total. Be certain that your lines/curves pass through each of the data points that you plotted. When you are confident in both the location of the points you plotted and the lines/curves through those points, darken them so your teacher can see your work clearly. (Hint: Look at Fig. 11.5 for guidance.) 301