2. The first jolt implies the jolt which will destroy the earth and everything on it, and the second jolt at which all dead men will rise up from death and from their graves. This same state has been described in Surah Az-Zumar, thus: And when the Trumpet shall be blown on that Day, all those who are in the heavens and the earth shall fall down dead except those whom Allah may allow (to live). Then the Trumpet shall be blown again and they will all stand up, looking around. (verse 68).
3. Hearts shall tremble: because, according to the Quran, only the disbelievers, the wicked people and the hypocrites will be terror-stricken on the Resurrection Day, the righteous believers will remain secure from this terror. About them in Surah Al-Anbiya (verse 103) it has been said: The time of great fright will not trouble them at all; the angels will rush forth to receive them, saying: This is the very day which you were promised.