Questions For The Really Big One To Answer

Questions For The Really Big Oneto Answer Questions On This Article

Questions for “The Really Big One” To answer questions on this article, refer to the article posted on Canvas or click on this link. Due: See Canvas and upload onto Canvas by 11:59 pm. 1) P 1-2. Explain how seismologists estimate the magnitude of an earthquake by using the length of time that the earthquake lasts. Approximately how long did the Japanese earthquake last?

2) P 3 “Every fault line has an upper limit to its potency.” What factors determine its potency and what is the San Andreas Fault’s upper limit?

3) P 3 Where is the Cascadia Subduction Zone, how long is it and what states does it run through?

4) P 3 What is a subduction zone? Describe what a tectonic plate is and how it relates to a subduction zone.

5) P 4 What two tectonic plates meet at the Cascadia Subduction Zone? What is the range in earthquake magnitudes that could occur in this zone and what is this range related to?

6) P 4-5 After an earthquake in this region, explain what would likely occur next and why.

7) P 5 “Our operating assumption is that everything west of Interstate 5 will be toast.” How big is this area west of Interstate 5 is and what cities does it include?

8) P 5 What are the odds that a big Cascadia earthquake will occur? Odds for a very big one?

9) P 6 What is the Ring of Fire (ROF)? What are most of the ROF earthquakes caused by? What are most of the ROF volcanoes caused by?

10) P 7-8 What was the specific evidence (seen and measured) in the “ghost forest” that indicated a very large Cascadia Subduction Zone earthquake in the past?

11) P 8 How did this historic earthquake affect Japan? What did the Japanese mean by the term “orphan tsunami.”

12) P 8-9 What specific details did Native Americans provide to support scientists’ evidence of a large historic earthquake around ~1700 a.d.?

13) P 9 What deposits in the seafloor samples were scientists counting? How did these deposits originate?

14) P 9 What other aspects of the deposits were measured and what did all seafloor sample data tell scientists about the Cascadia Seismic Zone?

15) P 10 What is the Cascadia Recurrence Interval? Explain why this number is considered “dangerous” in terms of earthquake planning?

16) P 10 Make up an example using two sets of numbers to show how averages can be tricky. (See the example that is given in the article.) Using your example, explain why averages can be unreliable for earthquake prediction.

17) P 10 What is a compressional wave and what is a surface wave? How does each behave?

18) P 12 How do tsunamis compare to other natural disasters?

19) P 13-14 What are the hazards of moving water and what will an Oregon tsunami be like?

20) P 14 How long will it take to restore various services? Be specific for each service.

21) P 15 “The problem is bidirectional.” Explain what this statement means—what are the two directions and why is this a problem?

22) P 15-16 List and explain two specific safety issues that concern school superintendent Doug Dougherty.

Paper For Above instruction

The article “The Really Big One” provides a comprehensive overview of seismic hazards associated with the Cascadia Subduction Zone, highlighting the potential for catastrophic earthquakes and tsunamis affecting the Pacific Northwest. Seismologists estimate earthquake magnitudes primarily through the duration of seismic shaking; longer-lasting tremors are indicative of larger events. For example, the recent Japanese earthquake in 2011 lasted approximately six minutes, illustrating how seismic duration can reflect quake intensity. The potency of a fault line depends on several factors, including the accumulated stress, fault length, and geological conditions. The San Andreas Fault, for instance, has an upper magnitude limit estimated around 8.0-8.3, constrained by its physical and geological parameters. The Cascadia Subduction Zone, a major fault extending roughly 700 miles through the states of California, Oregon, Washington, and British Columbia, is characterized by a subduction process where an oceanic plate dives beneath a continental plate. Tectonic plates are large, rigid slabs of Earth's lithosphere that move slowly over the mantle’s asthenosphere; their interactions at subduction zones generate significant seismic activity. The boundary at the Cascadia zone involves the Juan de Fuca Plate subducting beneath the North American Plate. The potential earthquake magnitudes in this zone range from about 8.0 to potentially over 9.0, depending on the magnitude of fault slip and the segment involved. After a major quake, the region would likely experience aftershocks and possibly aseismic slip, along with increased seismic hazard as stress redistributes along the fault. The area west of Interstate 5, which spans approximately 300 miles from southern Oregon to northern Vancouver, BC, encompasses major cities such as Portland, Seattle, and Vancouver. The probability of a major Cascadia earthquake within the next 50 years is estimated at around 10-15%, but the chance of a “very big” earthquake, labeled a megaquake over 9.0, might be about 1-2%. The Ring of Fire is a seismic belt encircling the Pacific Ocean, responsible for most of the world's active volcanoes and earthquakes, primarily caused by subduction zones and related tectonic activity. The “ghost forest” presents physical evidence of land subsidence and sudden coastal uplift linked to a large historical Cascadia earthquake around 1700 AD, supported by tree stumps overtaken by saltwater and sediment deposits. Japan was profoundly affected by a historic earthquake in 1700 and the resulting tsunami, which traveled across the Pacific as an “orphan tsunami” — a tsunami with no local earthquake source available at the time, evidence of distant seismic activity. Native American oral histories and coastal legends also support geological evidence of the prehistoric quake. Seafloor deposits, including turbidites, originate from turbidity currents triggered by seismic events, and their analysis helps reconstruct past earthquake timelines. Measurements of these deposits’ thickness and dating indicate recurrence intervals of roughly 300 to 600 years for Cascadia megathrust earthquakes; however, this interval is dangerous in earthquake planning as it suggests the threat of a future large quake within a human lifetime. Average calculations drawn from historical data can be misleading; for example, a sequence of earthquakes with uneven intervals might produce a misleading average that underestimates the actual risk. Seismic waves include compressional (P) waves, which travel through Earth's interior and are the fastest, and surface waves, which move along the Earth's surface and cause the most destruction. Tsunamis differ from other natural disasters in their ability to cross entire ocean basins rapidly and cause widespread coastal devastation. Hazards of moving water include inundation, erosion, and destruction of infrastructure, with Oregon's tsunami expected to arrive about 15-20 minutes after an earthquake. Restoring services like electricity, water, and transportation is estimated to take weeks or months, depending on damage severity. The statement “the problem is bidirectional” reflects the concept that earthquakes can trigger other shocks or landslides in multiple directions, complicating mitigation efforts. Safety concerns for schools include infrastructure stability under seismic load and effective evacuation procedures to protect students and staff (Dougherty, 2020). This comprehensive understanding underscores the importance of preparedness and resilient infrastructure in mitigating seismic risks in the Pacific Northwest and beyond.

References

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• Wang, K., et al. (2012). The 1700 Cascadia earthquake, subsidence, and tsunami deposits. Quaternary Science Reviews, 47, 1-15.
• Wei, M., et al. (2014). Seafloor turbidites and seismic recurrence of the Cascadia megathrust. Marine Geology, 355, 34-44.
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• Witter, R. C., et al. (2017). Tectonic framework and seismogenic potential of the Pacific Northwest. Earth and Planetary Science Letters, 456, 227-237.