Seismic getting scoured

[leaden mist]

Valda has 6 seismic surges at the start of her turn i storm striders and play scour blowing up all the surges does she still get the discount to her next guardian attack?

[deft needle]

she does, seismic surges applying the discount is not dependent on them being in the arena when the trigger resolves. Once the trigger goes onto the stack it's too late to stop the dicount

[leaden mist]

Ok cool thanks

[deft needle]

it's similar to how scouring runechants after they trigger won't stop the damage

[elfin hazel]

You can't play an instant during the start of the other player's turn as there is no priority window, so you can't destroy the seismic surges before they resolve.
But if you were to destroy them during your turn then no problem, the tokens will be destroyed.

[stiff gyro]

you can technically destroy them after they trigger but before they resolve because surges trigger at the beginning of the action phase, not beginning of the turn. But like Aegisworn said, the trigger will already be on the stack and will resolve successfully regardless