The angle of subduction of the down-going slab determines the surface profile of the earthquakes as seen in the image below. If the subduction angle was steeper (steeper subducting plate shown by yellow shade), how would the surface profile change?

Question

BlackTom AI · Accepted Answer

To approach this question, I’ll examine how subduction angle affects the surface expression of earthquakes and then evaluate each option in turn.
Option 1: 'The earthquake profile would widen, spreading further away from the trench.' If the subduction angle were steeper, the down-going slab is more vertical and its interaction with the overriding plate occurs over a shorter horizontal distance from the trench. This would lead to a tighter, not wider, surface distribution of seismicity, so this option is incorrect.
Option 2: 'The earthquake profile would remain unchanged.' A steeper subduction angle changes the geometry of the slab and faulting at depth, which alters where earthquakes occur near the surface. Therefore, saying it remains unchanged ignores the geometric consequences of a steeper angle, making this option unlikely.
Option 3: 'The earthquake profile would narrow, moving closer to the trench.' A steeper subduction angle implies the interface where earthquakes occur slopes more steeply toward the trench, causing the seismicity pattern to be concentrated more near the trench and over a shorter horizontal distance. This description matches the expected surface profile change for a steeper subduction and is consistent with plate-tectonics concepts about slab geometry and earthquake distribution. This option is correct.
Option 4: 'the earthquake profile would reverse' Reversing the profile would imply an inversion of the spatial pattern of earthquakes relative to the trench, which does not align with a monotonic change in dip angle of the subducting slab. There’s no mechanism here that would flip the entire distribution so that near-trench activity becomes far from the trench in a reversed way. This makes this option incorrect.
Option 5: 'The earthquake profile would stay the same size but shift to the right of the trench.' A shift to the right without a change in size would imply a lateral, not vertical, reorganization of the profile, which does not reflect the effect of a steeper dipping slab increasing the proximity of seismicity to the trench. This option mischaracterizes the vertical tightening and horizontal repositioning that accompanies a steeper angle, so it is incorrect.
In summary, evaluating the geometric implications of a steeper subduction angle shows that the surface expression of earthquakes becomes narrower and closer to the trench, which aligns with Option 3. The other choices fail to capture the expected change in the surface faulting pattern caused by a steeper slab dip.

ESS 101 A Examination 2 (Friday December 5th 7:00 - 8:30 PM PST)

The angle of subduction of the down-going slab determines the surface profile of the earthquakes as seen in the image below. If the subduction angle was steeper (steeper subducting plate shown by yellow shade), how would the surface profile change?

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ESS 101 A Examination 2 (Friday December 5th 7:00 - 8:30 PM PST)

The angle of subduction of the down-going slab determines the surface profile of the earthquakes as seen in the image below. If the subduction angle was steeper (steeper subducting plate shown by yellow shade), how would the surface profile change?

View Explanation

Log in for full answers

Similar Questions

During subduction:

The process of fracturing and movement of the outer layers of the Earth is called _____.

Transform boundaries occur where ____.​

What types of plate boundaries do not produce earthquakes?

What types of plate boundaries do not produce volcanoes?

Which type of plate boundary has the deepest earthquakes?

Sedimentary rocks that were deposited in a marine environment occur at the peak of Mt. Everest. What do these rocks demonstrate?

More Practical Tools for Students Powered by AI Study Helper

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Transform boundaries occur where ____.