The absence of deep focus earthquakes found along :

Question

Accepted Answer

Deep focus earthquakes are absent along both transform fault and divergent boundaries because these boundaries do not typically involve the subduction of one tectonic plate beneath another to significant depths.

Here's why Option 4 is correct:

*   **Transform Fault Boundaries:** At transform fault boundaries, plates slide horizontally past each other. There is no vertical movement of one plate under another. Since there's no subduction, there's no mechanism to generate earthquakes at great depths. The earthquakes that *do* occur at transform boundaries are generally shallow.

*   **Divergent Boundaries:** At divergent boundaries, plates are moving apart. Magma rises from the mantle to fill the gap, creating new crust. This process primarily involves shallow volcanic activity and shallow earthquakes. There is no subduction occurring, so deep focus earthquakes are not possible.

Now, let's explain why the other options are incorrect:

*   **Option 1: Only divergent boundaries:** This is incorrect because while divergent boundaries lack deep focus earthquakes, transform fault boundaries *also* lack them for the reasons explained above.

*   **Option 2: Only convergent boundaries:** This is incorrect because convergent boundaries are *characterized* by deep focus earthquakes. These occur where one plate subducts beneath another, allowing earthquakes to occur at depths of hundreds of kilometers. The question asks where deep focus earthquakes are *absent*.

*   **Option 3: Only transform fault boundaries:** This is incorrect because while transform fault boundaries lack deep focus earthquakes, divergent boundaries *also* lack them.