GEO302 - Exercises II: Global seismology
Return this problem set to Richard Allen
1. The P and S-arrival at a seismic station arrives at different times, the P-wave arrives
first followed by the S-wave. How else could you distinguish between P and S arrivals
as recorded on a three-component seismograph?
2. What is the wavelength of a surface wave with a period of 10 sec, 100 sec and 200 sec?
3. The daily electrical consumption in the United States in 1985 was about 7 x 109
kilowatt hours. If this energy was released in an earthquake what would its magnitude
be?
Use the equation
log10 E = 5.24 + 1.44 M
where E is in joules and M is the magnitude.
4. The figure below shows focal spheres with the first arrival polarities for two different
earthquakes. Black indicates a positive first motion, white is negative.
(a) Draw the fault-plane solutions on the two focal spheres.
(b) Indicate the fault types which generate earthquake 1 and 2.
(c) Suggest the tectonic setting where we might expect these fault types and give an
example of a specific location where we find the tectonic setting.
5. The P and S-arrivals for an earthquake in Turkey were recorded at the three stations
shown in the figure below. Calculate the origin time for this earthquake and locate its
epicenter using the following information:
Seismometer 1
P-wave arrival time
S-wave arrival time
Seismometer 2
P-wave arrival time
S-wave arrival time
Seismometer 3
P-wave arrival time
S-wave arrival time
Hours
Minutes
Seconds
13
13
19
20
58.9
04.7
13
13
20
20
02.6
10.8
13
13
19
19
54.5
57.4
Assume the focus was at the surface and use P- and S-wave velocities of 5.6 and 3.4
km/s respectively.
6. Using the earthquake traveltime curves below (Fig 4.13) and the two earthquake
records (Fig 4.14), determine for each earthquake (i.e. each record) (a) the epicentral
distance, and (b) the origin time.