Question

Shallow-focus earthquakes with tensional focal mechanism are characteristic of:

• A. Subduction zones
• B. Continental shear zones
• C. Transform faults
• D. Mid-ocean ridges

Hint:

Divergent boundaries (mid-ocean ridges) $\Rightarrow$ shallow, tensional earthquakes. Convergent boundaries $\Rightarrow$ deep compressional earthquakes.

Answer 1

The Correct Option is D

Step 1: Types of plate boundaries.
- Subduction zones: Compressional regime, deep and intermediate focus earthquakes. - Continental shear zones: Strike-slip, mostly shallow, but shear not tensional. - Transform faults: Strike-slip, shallow-focus, but dominated by shear not tension. - Mid-ocean ridges: Divergent boundaries, tensional stress regime, producing shallow-focus earthquakes ($< 70$ km).

Step 2: Correct setting.
Tensional mechanisms (normal faulting) with shallow-focus earthquakes are characteristic of mid-ocean ridges.

Final Answer:
\[ \boxed{\text{Mid-ocean ridges}} \]