There are two types of body waves: compressional (P) waves and shear (S) waves. Primary waves (P-waves) travel the fastest, so they arrive at the recording station (seismograph) first. Secondary or shear waves (S-waves) travel slower than P-waves so they arrive second.
Modified frequency modulation (MFM) is an encoding scheme used by PC floppy disk drives and older hard drives.
mf has 2 meanings, often used as: (i) Mother Fucker. (ii) My Friend. definition (i) is more commonly seen in chatrooms; whereas definition (ii) seen in multiplayer games. if someone uses mf towards you, it's best to pretend you dont understand, so they will explain - either (i) or (ii). Since you dont want to just start insulting them.