B. San Francisco, California is located in a tectonically active region, it occa
ID: 282937 • Letter: B
Question
B. San Francisco, California is located in a tectonically active region, it occasionally experiences strong earthquakes of San so in a portion have been FIGURE 162 is a map showing the kinds of Earth materials upon which buildings dune sands, river gravel, Francisco. These materials include hard compact Franciscan Sandstone, beach and that reduced large and artificial fill. from buildings destroyed in the 1906 earthquake what risk portions of the The fill is mostly debris insurance company to assess city to blocks of rubble. Imagine that you been hired by an have there may be in buying newly constructed apartment buildings located atx 16.2. Your job is to infor be whether the risk of property damage during strong carthquakes dittle or no damage expected or high (damage can A ments with models in Part expected. All that you have as a basis for reasoning is FIGURE 162 and knowledge of your ex of this activity. 1. Is the risk at location x low or high? Why? 2. Is the risk at location Y low or high? Why? 3. Is the risk at location z low or high? Why? C. On October 17, 1989, just as Game 3 of the World Series was about to start in San Francisco, a strong earthquake occurred at Loma Prieta, California, and shook the entire San Francisco Bay area. Seismographs at locations Y, and Z see FIGURE 16.2) recorded the shaking, and the resulting scismograms are shown in FIGURE 16.3. Earthquakes are recorded on the seismograms as deviations (vertical zigzags) from a flat, horizontal line. Thus, notice that much more shaking occurred at locations Y and Z than at location 1. The Loma Preta earthquake caused no significant damage at location X, but there was moderate damage to buildings at location Yand severe damage at location z. Explain how this damage report compares to your above predictions of risk (Part B). 2. The Loma Prieta earthquake shook all ofthe San Francisco Bay region. Yet FIGURE 16.3 is evidence that the earthquake had very different effects on properties located only 600 m apart. Explain how the kind of substrate (uncompacted vs. firm and compacted on which buildings are constructed influences how much the buildings are shaken and damaged in an earthquake. D. REFLECT&Discuss; magine that you are a member of the San Francisco City Council. Name two actions that you could propose to mitigate (decrease the probability of future earthquake such as the that occurred at locations Y and Z in the Loma Prieta earthquake, hazards damageExplanation / Answer
answer-b- a- at point X the risk of occuring of earthquake damge is low. because this region lies on franciscan sandstone member. it formation of composed of compact sandstone. this region lies below compact sandstone. the surface wave dont travel with high velocty in this compact layer.
b- the Y location lies modern beach and dune sands. these region composed looses and fragmented sand particle. the surface wave generate by the earthquake travel at very rapid rate and cause huge destruction.liquifiction make occurs. So the risk in found in Y location is High.
c- the Z location lies in artificial fill that is debris comes from the destruction of building it includes the rubbles and block. the rocks is not compact wave can travel at very rapid rate. if the water is being added here. the liquifiction may occur which cause huge damage. So the risk at point Z is high.
answer c- a- the highly damage serve in location that lies on the artificial fill that is composed of rubble and block that is being destroyed in previous earthquake that occured in 1905. these are consist of loose fragment liquifiction process may also occurs in these region. So the risk of damage is very high. ON THE other side at point x is lies below compact sandstone of fransicon sandstone member. So here the damge is very low.
b- as we can see in seismograms of all station we can easily determine that massive damge occur in site y and z and reason such damage is lying on the region where looses fragment and liquifiction may also occur in such region. we can see in the seismic station at point x that here the no variation in the seismograph. this lies region lies below the compact sandstone so the wave do not travel at high velocity so caused no damage in the region. builiding lies on y and z region will shaken alot and building lies on point x dont shake they was stable.
answer- If I was the member San fransico city counsil i will not allow any construction above the loose soil. because loose sand , clay and rubble are not favourable site for the building construction. crack can easily developed in such rock. I will stricly apply the rule that construction should be made only such region where the basement rock is compact either granite or compact sandstone.
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