This page contains significant spoilers from ArmA 3's 'The East Wind' and 'Apex Protocol' campaigns.
The Eastwind device is a machine believed to be capable of causing earthquakes. During The East Wind campaign, capturing the device turns out to be the primary objective of Captain Miller in the non-canon Game Over ending.
In the Apex Protocol campaign, Captain Miller reveals that he believes the device was used to cause the tsunami that wreaked havoc across Tanoa. During this campaign, NATO intelligence suggests that the device produces foreshocks as part of its arming sequence. At the end of the Apex Protocol campaign, Miller secures the Eastwind device and airlifts it to an undisclosed location.