We were surprised by the sharp increase in import volume.
Literal
Import volume [possessive-の] sharp increase [target-に] we [topic-は] were-surprised.
驚く (おどろく, 'to be surprised') takes に for the cause of surprise. 急激な (きゅうげきな, 'sharp, rapid') is a formal na-adjective. 我々 (われわれ) is the formal 'we.' Typical of economic reporting.