On shore they can use big truck mounted vibrators and it has much less environmental impact.
True. or to set off charges. Since we are into logic today we have the statement from their PR as part of their to do list:
What method is more likely to cause the most surface damage: a Vibroseis truck vibrating a metal plate underneath it, or an explosive charge of 2-50 lbs set in a drilled hole 10-250 ft deep?
My vote goes to charges going off as causing the most potential surface damage. Not to mention annoyance to the farmers.
A sub question is whether the Brown gang would spend the contract money to grab 3-4 Vibroseis trucks? Probably more expensive than drilling holes, and setting off charges.