Odd classes, due 3/2/11
Finish the Locating the epicenter class work if you did not finish in class. The figures mentioned are in your text book.
Problem: Determine the epicenter location and the time of occurrence of an actual earthquake, using the travel time of P and S waves recorded at three seismic stations.
Materials: figure handout and map, drafting compass (or string and tack), metric ruler
Procedure:
1. The seismogram in Figure 19-8 shows the arrival time of the first P-wave at 10h, 50min, 32s GMT. Estimate the arrival time of the first S-wave to the nearest tenth of a minute.
2. Subtract this S-wave time from the initial P-wave time. What is the P-S separation on the seismogram, in minutes and tenth of minutes? Enter this value in the Data table for the Berkeley seismic station.
3. The P-S separation observed on two other seismogram, also listed on the table. Use the travel-time curves in Figure 19-9 to determine the distances at which the P- and S- curves are separated by the time intervals listed in the data table under map epicenter distances.
4. Use the scale to determine the map distance (in cm) for the epicenter distances from each seismic station and record these distances in the table.
5. Use the compass to draw circles around each station on the map with the radius of each circle equal to the map distance in cm, for that station.’
6. Mark the point of intersection. This is the epicenter of the earthquake.
7. Determine the time of occurrence of the earthquake by reading the P-wave travel time from Figure 19-9 for the epicentral distance for Berkeley. Subtract this from the initial P- wave arrival time at Berkeley, which was 10h, 50mom. Express this time in hours, minutes and seconds.
AND
Read 511-515 1) according to the reading how do tsunamis occur? 2) Why is the term tidal wave incorrect for describing tsunamis? 3) do the using math problem on p 513
