Relating to earthquakes (7)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">relating to earthquakes</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for seismic that I've seen before include "earth-shattering effects?" , "Caused by an earthquake" , "Resulting from earthquakes" , "massive" , "shock" .)