1.What is the amplification of seismic waves and how will this amplification gen
ID: 289546 • Letter: 1
Question
1.What is the amplification of seismic waves and how will this amplification generate hazards in Seattle during the “really big one” earthquake (Mag > 8) even though the epicenter will be off the coast of Washington, far from Seattle? (Important fact: most of the Seattle is built on top of unconsolidated sediments, including tide flat sediments and glacial sediments.)
2.Appalachian Mountains are an example of an old and eroding mountain range, and Alfred Wagner used the Appalachians as evidence of the formation of Pangaea. How did the Appalachians form and when did the final act of mountain building occur (which is the same time Pangaea formed)?
3.What is the tectonic setting of Kiska and all the western (west of Cleveland Volcano) Aleutian volcanoes? (Be sure to go there via Google Earth.)
4.Why or why not are there active volcanoes in the Himalaya Mountains? Be sure to include the current tectonic setting and activity of the Himalaya in your answer.
Explanation / Answer
1. It is well known that the seismic waves produced by rock failure travel faster in harder rocks than in softer ones. The movement of such waves in soft sediments leads to accumulation of energy which is what leads to their amplification. An earthquake of a strong magnitude is likely to have a devastating impact on Seattle as the waves reaching the loose sediments would cause a reduction in velocity of seismic waves originating far offshore. As the velocity would decrease the energy would build up and amplify the movement of the ground underneath Seattle.
2. The Appalachian Mountains formed as a result of the collision of African and North American continental landmasses. The final phase of the entire orogenesis took place during late Pennsylvanian (about 290 million years ago) when the Pangaea was a supercontinental landmass comprising of all the present-day continents.
3. Kiska island in the North Pacific Ocean is under the influence of subduction of Pacific plate into the North American plate. This causes the formation of volcanic chains and the resulting tectonic setting along the Western Aleutian island chain is that of a convergent plate boundary.
4. There are no active volcanoes in the Himalayas as the orogeny was that of a continent-continent collision type. The Himalayan region never experienced substantial volcanism as the mountains attained great heights after the subduction of Tethyan oceanic crust. The present-day tectonic setting of the Himalayas does not favor volcanic activity as there is no influence of an oceanic crust subduction within the belt of the tall mountain chain.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.