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Earthquakes and Seismic Hazards, Fall 2001
Geol 344
Homework #3
(50)
1. Consider the focal mechanism solutions below for all Mw >5.4 earthquakes around the world during
September and early October, 2001.
a) Explain the general significance of the locations of these moderate to large magnitude earthquakes.
You do not need to consider each earthquake individually. Just the general distribution.
(2)
b) Choose any three of the focal mechanism solutions (circle them on the map) and provide the following
information:
i) Fault plane solutions (strike, dip, and type of fault) for both faults in each double couple.
ii) The tectonic setting for the locations you picked, and a line of reasoning as to whether the
earthquake focal mechanism solution makes sense given the general tectonic setting.
(15)
(9)
c) The largest magnitude earthquake on the map is a Mw 6.4 reverse-oblique earthquake event off the
coast of Kamchatka. Indicate this particular solution by drawing a box around it on the map.
(2)
Earthquakes and Seismic Hazards, Fall 2001
Geol 344
2. The table below shows information for the two largest earthquakes of 1999 for oceanic and continental
crust, respectively.
OCEANIC CRUST
CONTINENTAL CRUST
99/11/15 05:42:43.31
SOUTH INDIAN OCEAN
Epicenter: 1.416°S 89.004°E
Mb 6.5 MS 7.0 MW 6.8
99/08/17 00:01:38.56
TURKEY
Epicenter: 40.639°N 29.830°E
Mb 6.3 MS 7.8 Mw 7.4
MOMENT TENSOR SOLUTION
Depth 19
No. of sta: 17
MOMENT TENSOR SOLUTION
Depth 17
No. of sta: 40
Principal axes:
T Val= 1.59 Plg=13 Azm= 54
N
0.05 74 196
P
-1.63
9
322
Principal axes:
T Val= 1.36 Plg=12 Azm= 49
N
0.00 75 188
P
-1.36 10
317
Best Double Couple:Mo=1.6*10**19
NP1:Strike= 98 Dip=74 Slip= 178
NP2:
188 88
16
Best Double Couple:Mo=1.4*10**20
NP1:Strike= 92 Dip=75 Slip= 178
NP2:
183 88
15
a) Use the epicenter data (latitude/longitude) to determine the exact locations of the earthquakes on a
world map, then describe these locations as well as the general tectonic setting for each location.
(4)
b) Use the double-couple solutions to create focal mechanism diagrams for each event.
(4)
c) Describe the type of faulting responsible for each earthquake (2 potential solutions for each).
(6)
d) For each earthquake, there are three different magnitudes listed. Why are there three, and why are they
different from each other?
(4)
e) Contrast the two earthquake events, providing reasons for the difference in respective maximum
magnitudes in oceanic versus continental crust.
(4)