Recurrence intervals, probability, and risk are concepts that will pop up throughout this course. It is important that you understand them – as we will use these tools later in this week and into the quarter.

Recurrence Intervals (RI)

Geologists often use the geologic record to study, map, and/or date past hazardous occurrences. Often natural hazards are communicated in terms of recurrence intervals.

The recurrence interval is not a prediction of when an event will happen. It is simply the average amount of time (in years) between similar hazardous events.

PLEASE show your work for full credit!

Question 1. Use the formula for Recurrence Interval (RI) to calculate the average number of years between high-magnitude earthquakes off the Washington coast. (Be sure to include the unit in your final answer!) (1 pt)

Calculating the Annual Probability (AP) of an event from a Recurrence Interval (RI)

Now that you have a Recurrence Interval for high-magnitude quakes off the Washington coast, we can calculate the probability of one of these earthquakes in any year (AP).

Question 2. Use the equation for Annual Probability (AP) to calculate the probability of high-magnitude earthquakes occurring off the coast of Washington this year. (Express your answer as a decimal and a percentage.) (1 pt)

Question 3. What is the probability that this earthquake will NOT occur in the next year? Express your answer as a percentage. (1 pt)

Question 4. Given the probability above, is this earthquake something you should worry about? Support your answer with a reason. (1 pt)

Calculating the Probability of an Event (Pt) over several years.

Question 5. Let’s say you plan to live in Washington State for 60 years. What is the probability that Washington (and you!) will experience one of these massive earthquakes during those 60 years? (Hint: Use the equation for the probability of an event of a series of years (Pt). Express your answer as a decimal and a percentage. (2 pt)

More Practice!

Question 6. There have been 15 large earthquakes in the Andean subduction zone in the last 12,000 years. What is the recurrence interval (RI) of these earthquakes? Remember units! (1 pt)

Question 7. Given the information above, what is the annual probability (AP) of a large earthquake in the Andean Subduction zone in a single year? Express your answer as a decimal and a percentage. (1 pt)

Question 8. Your family plans on moving to Chile where you will spend the next 50 years of your life. What is the probability that you will experience a large earthquake from the Andean Subduction Zone within the next 50 years (Pt)? Hint: use the information in question 7!) Express your answer as a decimal and a percentage. (2 pts)

Question 9. If the annual probability (AP) of having 1 cm of volcanic ash fall on your house in a given year is 0.1% (or .001), what is the probability (Pt) of getting ash on your house in 60 years? Express your answer as a decimal or a percentage. (2 pts)

 

  

Transcribed Image Text:

Johns River, Grays Harbor (location, p. 103) INFERRED LAND LEVEL ↑ Soil below water in photo TIME-> Forest Marsh Mudflat Range of dates for subsidence During earthquake, land subsides. 1500 1000 Between earthquakes, land rises from tidal deposition and gradual tectonic uplift. 500 B.C. A.D. 500 Soil inconspicuous in most outcrops № As land rises, forest replaces marsh. 1000 1500 2000 Johns River, Grays Harbor (location, p. 103) INFERRED LAND LEVEL ↑ Soil below water in photo TIME-> Forest Marsh Mudflat Range of dates for subsidence During earthquake, land subsides. 1500 1000 Between earthquakes, land rises from tidal deposition and gradual tectonic uplift. 500 B.C. A.D. 500 Soil inconspicuous in most outcrops № As land rises, forest replaces marsh. 1000 1500 2000

Answer rating: 100% (QA)

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