Table 1. Using Seismograms to Locate an Earthquake
Observations: Look at the area and read the descriptions associated with each location. Think about what each statement implies about possible earthquake hazards for that location. The blue-gray triangles represent the location of seismic stations in the area.
The P-S Time Interval for the three stations (Mesaview, Hillside, and White Sands) provides information on where the earthquake occurred. Plot the P-S time interval (the time between the arrivals of the P-waves and S-Waves) for each station on the graph below. Then use the distances calculated from the graph to determine approximately where the earthquake occurred.
Answer the question below the graphs.
Three Seismograms Graph to Determine Distance from Epicenter
Station Distance from earthquake (circle the letter for the best answer)
Mesaview (a) 2-3 km, (b) 3-4 km, (c) 4-5 km, (d) 5-6 km, (e) 6-8 km
Hillside (a) 2-3 km, (b) 3-4 km, (c) 4-5 km, (d) 5-6 km, (e) 6-8 km
White Sands (a) 2-3 km, (b) 3-4 km, (c) 4-5 km, (d) 5-6 km, (e) 6-8 km
From the general location of the earthquake, which geologic feature is likely to have caused the earthquake?
Table 2. Impact of an Earthquake for Each Town
For each of the towns located in this area, infer what hazards possibly accompanied the recent earthquake, considering the topographic and geologic setting of that town.
Interpret whether each town has a high, moderate, or low hazard relative to the other towns, and circle your choice in the table below. There is not necessarily one right answer, so explain your reasons in the space provided.
Name of Town Possible Earthquake Hazards (circle all that apply) Hazard Relative to the Other Towns (circle one) Reasons for High, Moderate, or Low Hazard Assessment
Sandpoint (a) ground shaking,(b) especially intense ground shaking of areas close to the fault,(c) liquefaction of soils and other weak materials because of shaking,(d) landslides and other slope failures caused by shaking, (e) destruction by a tsunami (a) high(b) moderate(c) low
Hillside (a) ground shaking, (b) especially intense ground shaking of areas close to the fault, (c) liquefaction of soils and other weak materials because of shaking, (d) landslides and other slope failures caused by shaking, (e) destruction by a tsunami (a) high
(b) moderate
(c) low
Cascade Village (a) ground shaking, (b) especially intense ground shaking of areas close to the fault, (c) liquefaction of soils and other weak materials because of shaking, (d) landslides and other slope failures caused by shaking, (e) destruction by a tsunami (a) high
(b) moderate
(c) low
Mesaview (a) ground shaking, (b) especially intense ground shaking of areas close to the fault, (c) liquefaction of soils and other weak materials because of shaking, (d) landslides and other slope failures caused by shaking, (e) destruction by a tsunami (a) high
(b) moderate
(c) low
Name of Town Possible Earthquake Hazards (circle all that apply) Hazard Relative to the Other Towns (circle one) Reasons for High, Moderate, or Low Hazard Assessment
Ashton (a) ground shaking, (b) especially intense ground shaking of areas close to the fault, (c) liquefaction of soils and other weak materials because of shaking, (d) landslides and other slope failures caused by shaking, (e) destruction by a tsunami (a) high
(b) moderate
(c) low
Cliffside (a) ground shaking, (b) especially intense ground shaking of areas close to the fault, (c) liquefaction of soils and other weak materials because of shaking, (d) landslides and other slope failures caused by shaking, (e) destruction by a tsunami (a) high
(b) moderate
(c) low
Riverton (a) ground shaking, (b) especially intense ground shaking of areas close to the fault, (c) liquefaction of soils and other weak materials because of shaking, (d) landslides and other slope failures caused by shaking, (e) destruction by a tsunami (a) high
(b) moderate
(c) low
White Sands (a) ground shaking, (b) especially intense ground shaking of areas close to the fault, (c) liquefaction of soils and other weak materials because of shaking, (d) landslides and other slope failures caused by shaking, (e) destruction by a tsunami (a) high
(b) moderate
(c) low
Table 3. Locating the Epicenter of the Earthquake (Optional)
Use the graph of distance versus P-S time interval (on Table 1) to more precisely determine the location of the epicenter of the earthquake. To determine how far the earthquake was from each seismic station, use the P-S time interval for a seismic station and read off the corresponding distance from the P-S time-interval graph.
Then, approximately scale off the appropriate distance from the earthquake to the seismic station and sketch part of a circle with this radius around the seismic station. The three circles intersect at the epicenter (the place on the surface directly above the earthquake). The circles may not all intersect at a single point, but may only come close to doing so. The triangles on the figure below represent the location of seismic stations.
