Initial margin requirements may be met in cash in multiple currencies or via multiple types of securities.

Below is a general summary per service (refer to above links for official details).

Acceptable Cash

SwapClear Global Service (LCH Ltd. incorporated in U.K.)
SwapClear Members Futures Commission Merchants (FCMs)
US dollars US dollars
Canadian dollars
Swiss francs
Japanese yen
Swedish krona
Danish krone
Norwegian kroner

Acceptable Securities (Acceptable issues will be maintained using ISIN lists.)

SwapClear Global Service
Sovereign and government-guaranteed debt of Australia, Austria, Belgium, Canada, Denmark, Finland, France, Germany, Italy, Japan, Luxembourg, the Netherlands, Norway, Spain, Sweden and the UK. KfW bonds also accepted.
US dollar-denominated securities comprising all US Treasury securities (except strips) and debentures issued by FNMA, FHLMC and FHLB.
Mortgage-backed securities issued by GNMA.