CVEEN 6330

Homework Assignment 3

Part A - Earthquake Magnitude and Fault Parameters from Geologic Data

The use of modern seismologic methods and historical records for estimation of the maximum earthquake potential of

a region is limited by the short historical record, during which only a few of the main faults have experienced surface

faulting with accompanying large earthquakes. The applications of other geologic methods (e.g., fault displacement

measurements, fault rupture measurements and age determinations) enables use to expand our knowledge of potential

seismic conditions such as earthquake magnitude, recurrence intervals, and fault slip rates.

1. Using the geologic map and the fault traces mapped in the Salt Lake Valley, determine the magnitude of the

maximum credible earthquake (MCE) for the:

(a) Salt Lake City segment of the Wasatch Fault

(b) Taylorsville Fault

(c) Granger Fault

For the Salt Lake City segment of the Wasatch Fault, assume that this segment is comprised of the East

Bench Fault and the Wasatch Fault zone that extends to the south into Draper, Utah.

For 1 (a), (b) and (c) use the regression equations found in Table 2A of Wells and Coppersmith to make the

prediction of MCE based on surface rupture length (SRL). In estimating surface rupture length, use a

curvelinear distance. (Note that Wells and Coppersmith recommend that the regression equation developed

for all-slip-type is appropriate for most applications because of the large number of data and good statistical

correlations (see p. 1000).)

Also, discuss any additional assumptions and/or uncertainties with your estimates of the MCE.

2. Using the estimates of surface rupture length from problem 1, estimate the mean and maximum amount of

expected displacement on the fault systems. Give you answer in meters. Discuss any assumptions and

uncertainties with your estimates of mean and maximum fault displacement.

3. Given an earthquake with M = 6.5, what is the surface rupture length and maximum amount of fault

displacement that would you expect using the paper from Wells and Coppersmith?

Part B - Median Response Spectra from Attenuation Relations

4. Use the Abrahamson and Silva (2008) attenuation relation for this problem and the fault parameter for the

Salt Lake City Segment of the Wasatch Fault. Assume that this fault is capable of generating a Mw 7.0

earthquake and the depth to the base of the fault is 20 km. Also, assume that the fault ruptures to the surface.

a. Make a plot of peak ground acceleration (pga) in g as a function of distance from the fault trace. To

do this, plot pga (y-axis) versus Rx for distances values between 0 and 100 km. Assume that the

fault ruptures to the surface and that the soil type is NEHRP site class D with the Vs values for this

site class at the mid-range. Also, assume that all Rx distances are located on the hanging wall side

of the fault. Assume that the average dip angle of the fault (i.e., rupture plane) is 45 degrees. See

additional information at the end of this homework. To determine the Z1.0 and Z2.5 values use Deep

Profile 1 in the attached figures. Assume that these depths do not vary as a function of distance

from the fault.

b. Use the information provided to construct a median 5 percent damped acceleration, velocity and

displacement response spectra for the intersection of I215 and Hwy 201using the Abrahamson and

Silva (2008) attenuation relation.

c. Compare the median acceleration response spectrum develop in 4b with the average median

response spectrum from all other NGA relations.

TOP PORTION OF DEEP PROFILE: 0 - 1000m

0

100

200

300

400

500

600

700

800

900

1000

0 1000 2000 3000 4000 5000

Vs (m/s)

dep

th (

m) SLC Airport East, Wong &

Silva (1993)

Lacustrine-alluvial silt and

clay (Northern CA Bay Mud),

Wong et al. (2002,

published)Interpreted cross section,

distance = 15.5km, Hill et al.

(1990)

Generic U.S. Rock, Boore &

Joyner (1997)

Deep Profile I, this study

Deep Profile II, Wong et al.

(2002, unpublished)

Semi-consolidated

Unconsolidated

End, Wong et al.

2002, published

(152m)

BOTTOM PORTION OF DEEP PROFILE: 1000 - 7000m

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

6000

6500

7000

0 500 1000 1500 2000 2500 3000 3500 4000

Vs (m/s)

dep

th (

m)

SLC Airport East, Wong & Silva

(1993)

Lacustrine-alluvial silt and clay

(Northern CA Bay Mud), Wong et

al. (2002, published)Interpreted cross section,

distance = 15.5km, Hill et al.

(1990)Generic U.S. Rock, Boore &

Joyner (1997)

Deep Profile I, this study

Deep Profile II, Wong et al. (2002,

unpublished)

End, Wong and Silva

1993 (>2600m)

Consolidated

Bedrock

Matchpoint

(6000m)

Infinite Half-Space

BOTTOM PORTION OF DEEP PROFILE: 1000 - 7000m

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

6000

6500

7000

0 500 1000 1500 2000 2500 3000 3500 4000

Vs (m/s)

dep

th (

m)

SLC Airport East, Wong & Silva

(1993)

Lacustrine-alluvial silt and clay

(Northern CA Bay Mud), Wong et

al. (2002, published)Interpreted cross section,

distance = 15.5km, Hill et al.

(1990)Generic U.S. Rock, Boore &

Joyner (1997)

Deep Profile I, this study

Deep Profile II, Wong et al. (2002,

unpublished)

End, Wong and Silva

1993 (>2600m)

Consolidated

Bedrock

Matchpoint

(6000m)

Infinite Half-Space