5. Describe the intensity pattern shown on your map in one paragraph. Include where the highest intensities are found, other areas with generally high intensity, and areas with low intensity Earlier in the lab, we triangulated the location of the epicenter using three seismographs and found the epicenter to be south of San Francisco. The exact location of the epicenter, determined by triangulation on a large-scale map using P-S intervals from approximately 30 seismographs, is seven miles north of Santa Cruz (find Santa Cruz on your intensity map). 6. How does the area of maximum intensity as shown by your intensity map compare to the actual location of the earthquake epicenter? 7. Discuss some possible reasons for high amounts of damage in San Francisco and Oakland, while locations closer to the epicenter, such as Los Altos and Watsonville, reported lower intensities. The seismograms you are studying in this lab are from Loma Prieta earthquake that affected the San Francisco Bay area on October 17, 1989 at 5:04 pm. This earthquake took place near major population centers and caused significant loss of life and property. You have already found its epicenter and determined its magnitude on the Richter scale. Damage from an earthquake is assessed using the Modified Mercalli Intensity Scale (Table 1). Note that intensity is not the same as magnitude. Magnitude measures the energy released by an earthquake. Intensity measures the resulting damage, which is a function of the types of buildings, how well they are built, and the material they are built on, in addition to the earthquake magnitude and distance from the epicenter. The city of San Francisco has been built on many different types of materials. Some of these materials are shown in the figure below. These materials include uncompacted beach and dune sands, compact Franciscan Sandstone, and artificial fill dumped into San Francisco Bay. In some cases, this fill is debris left over from buildings destroyed in the 1906 San Francisco earthquake. Consider the results of your experiment and assess the relative intensity of ground shaking and seismic risk to buildings located at X, Y, and Z based on the materials that underlie each location. Location X is built on Franciscan sandstone (a sedimentary rock), location Y is built on beach and dune sands (unconsolidated sediments) and location Z is built on artificial fill dumped into San Francisco Bay. Is the risk low (little or no damage) or high (a lot of damage) for each site? Seismographs at locations X,Y, and Z recorded the shaking from the October 17,1989 carthquake. The carthquake caused no significant damage at location X, but there was moderate damage to buildings at location Y and severe damage at location Z. 4. Explain how the actual seismographs and damage compares to what you predicted in the previous questions. ( 1 point) Following the Loma Prieta earthquake, the United States Geological Survey sent out questionnaires to the affected are.

1. 5. Describe the intensity pattern shown on your map in one paragraph. Include where the highest
intensities are found, other areas with generally high intensity, and areas with low intensity
Earlier in the lab, we triangulated the location of the epicenter using three seismographs and
found the epicenter to be south of San Francisco. The exact location of the epicenter, determined
by triangulation on a large-scale map using P-S intervals from approximately 30 seismographs, is
seven miles north of Santa Cruz (find Santa Cruz on your intensity map).
6. How does the area of maximum intensity as shown by your intensity map compare to the
actual location of the earthquake epicenter?
7. Discuss some possible reasons for high amounts of damage in San Francisco and Oakland,
while locations closer to the epicenter, such as Los Altos and Watsonville, reported lower
intensities. The seismograms you are studying in this lab are from Loma Prieta earthquake that
affected the San Francisco Bay area on October 17, 1989 at 5:04 pm. This earthquake took place
near major population centers and caused significant loss of life and property. You have already
found its epicenter and determined its magnitude on the Richter scale. Damage from an
earthquake is assessed using the Modified Mercalli Intensity Scale (Table 1). Note that intensity
is not the same as magnitude. Magnitude measures the energy released by an earthquake.
Intensity measures the resulting damage, which is a function of the types of buildings, how well
they are built, and the material they are built on, in addition to the earthquake magnitude and
distance from the epicenter. The city of San Francisco has been built on many different types of
materials. Some of these materials are shown in the figure below. These materials include
uncompacted beach and dune sands, compact Franciscan Sandstone, and artificial fill dumped
into San Francisco Bay. In some cases, this fill is debris left over from buildings destroyed in the
1906 San Francisco earthquake. Consider the results of your experiment and assess the relative
intensity of ground shaking and seismic risk to buildings located at X, Y, and Z based on the
materials that underlie each location. Location X is built on Franciscan sandstone (a sedimentary
rock), location Y is built on beach and dune sands (unconsolidated sediments) and location Z is
built on artificial fill dumped into San Francisco Bay. Is the risk low (little or no damage) or high
(a lot of damage) for each site?
Seismographs at locations X,Y, and Z recorded the shaking from the October 17,1989
carthquake. The carthquake caused no significant damage at location X, but there was moderate
damage to buildings at location Y and severe damage at location Z. 4. Explain how the actual
seismographs and damage compares to what you predicted in the previous questions. ( 1 point)
Following the Loma Prieta earthquake, the United States Geological Survey sent out
questionnaires to the affected area requesting information on the effects of the earthquake.

2. Typical responses to the survey are listed in Table 2. Use the responses from the damage survey
to prepare a map of the damage and assess the factors that control the distribution of damage
from an earthquake. Follow the steps below. Step 1: Compare the effects of the earthquake to the
Modified Mercalli Intensity Scale (Table 1) and assign an intensity value to each location in
Table 2. Some have been done for you. Step 2: Plot the intensity values on the following map
and contour the data. Remember, contours are lines that separate points of greater value - on one
side of the line - from points of lesser value on the opposite side of the line. Start by finding the
highest intensity value on your map and draw a contour that encloses all points with that value.
Do the same for each intensity until you run out of values. Keep the following in mind -do not
enclose all higher values within the same line if there are lower values between them - for
example you would not draw the 12 contour though an area where all locations are less than 12.
Contours do not have to close - do not draw contours over the ocean to close them - there is no
data over the ocean and so there is no basis for drawing contours over the ocean. It's OK to draw
them over the bay. You do not need to turn your map in, instead answer the following questions
on the answer sheet. 5. Describe the intensity pattern shown on your map in one paragraph.
Include where the highest intensities are found, other areas with generally high intensity, and
areas with low intensity. (4 points) Earlier in the lab we triangulated the location of the epicenter
using three seismographs and found the epicenter to be south of San Francisco. The exact
location of the epicenter, determined by triangulation on a large scale map using P-S intervals
from approximately 30 seismographs, is seven miles north of Santa Cruz (find Santa Cruz on
your intensity map). 6. How does the area of maximum intensity as shown by your intensity map
compare to the actual location of the carthquake epicenter? (1 point) 7. Discuss some possible
reasons for high amounts of damage in San Francisco and Oakland, while locations closer to the
epicenter, such as Los Altos and Watsonville, reported lower intensities. (1 point)
Table 1. Modified Mercalli Intensity Scale
Table 2 - Eyewitness Accounts and Damage Reports from 1989 Loma Prieta Earthquake