Questions

25F-GEOL108 Quiz 5 (Hazards from Earthquakes & Tsunamis)

Multiple choice

How do we know that a megathrust earthquake at the Cascadia subduction zone caused a large tsunami to hit the Pacific Northwest in 1700? (select all that apply)

Options

A.Using three seismographs, scientists could calculate distances, draw circles, and find the epicenter of the earthquake.

B.Geologic evidence of tsunamis are found across the whole coast from British Columbia, Canada to California, indicating it was not a small tsunami

C.Drowned trees indicate that sea level increased due to global warming

D.Ocean sand layers well inland indicate tsunamis inundated the coast

E.Drowned trees indicate seawater rushed inland, suggesting land subsidence after a megathrust earthquake

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Step-by-Step Analysis

To tackle this question, I’ll assess each option in terms of what evidence would support a megathrust earthquake and a large tsunami at Cascadia in 1700. Option 1: 'Using three seismographs, scientists could calculate distances, draw circles, and find the epicenter of the earthquake.' This is not plausible for an event expected to have occurred in 1700, long before modern seismographs existed, and even with modern data, relying on seismographs alone would not directly recor......Login to view full explanation

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