What was the cause of the electromagnetic buildup?
In the late 1970's, the DHARMA Initiative drilled into a pocket of electromagnetic energy which was released. This was referred to by DHARMA as the Incident. The survivors of Oceanic 815, who had traveled to the past, attempted to stop the incident by detonating a hydrogen bomb. Their attempt failed, and it is unclear whether they in fact caused the Incident. ("The Incident, Part 1")
What is the failsafe?
The failsafe was a key that could be turned in order to cause the self-destruction of the Swan. Doing so was considered dangerous and unpredictable, as the failsafe could only be activated from directly underneath the station. ("Live Together, Die Alone")
The Staff is a medical facility, built by the DHARMA Initiative. It was later used by the Others as the place they would bring pregnant women to give birth, and die, due to the problems experienced by pregnant women on the Island. ("D.O.C.")
Why was there a fake beard and clothes at the station?
These were used by the Others to give the impression to the survivors of Oceanic 815 that the Others were a much more rustic people than they really were. ("Maternity Leave") ("Live Together, Die Alone")
Why did the station appear abandoned?
Because the Others had hidden all the medical equipment in a secret vault. ("D.O.C.")
He was a theoretical astrophysicist, and high ranking member of the DHARMA Initiative, who used a stage names (such as Marvin Candle, Mark Wickmund and Edgar Halliwax) while recording orientation films for various DHARMA facilities. ("Some Like It Hoth")
Drilling into the massive pocket of energy beneath the Swan work site, ("The Incident") though it is possible that the survivors also caused some of the damage by detonating the Jughead, as "whatever happened, happened" still applies. ("The Incident") ("The End")
How was the Swan station preventing a similar Incident in the future?
There had been a long-standing feud between the Hostiles and DHARMA, each claiming some right to the Island. Although a truce had been struck between the two, it was uneasy; and eventually someone among the Hostiles gave the order to exterminate the DHARMA initiative. ("The Man Behind the Curtain") ("LaFleur")
Were there any survivors from the DHARMA Initiative?