Daisy's earthquake served two functions, getting rid of the witness (who Nick figured was probably too shaken up by the jeep veering around to radio in before Nick could shoot him too, but at least he didn't need to waste a bullet now) and freaking out the A.I.M. goons while it likely fucked up all their precious expensive technology. To prove this latter theory he pulled out his energy meter and got a much lower and sporadic reading from the area they were headed towards.
"Good," Nick stated his approval succinctly and holstered his weapon. They were about halfway through the valley now, the wreck of the jeep off to their right and behind them now. Nick relaxed a little and remarked, "Ain't this fun?" knowing full well that Daisy probably did not agree. He kept his attention on the meter and watched as the power source grew stronger. "Say, why don't you send another few tremors due north? Our dino pals don't seem to give a fuck." Which was true as they simmered down their annoyance and returned to their grassy dinner.
If Daisy's earthquakes could further disrupt whatever the hell A.I.M. was doing then it would be easier to sneak in among the chaos to plant some well placed explosives then get the fuck out. If she managed to set off any more traps with her tremors ahead of time then it was a bonus- one less thing they'd have to worry about on their way in.