The sixth seal:
When he opened the sixth seal, I looked, and behold, there was a great earthquake, and the sun became black as sackcloth, the full moon became like blood, (Revelation 6:12).
Immediately after the tribulation of those days: ‘The sun will be darkened, and the moon will not give its light; the stars will fall from the sky, and the powers of the heavens will be shaken.’ At that time the sign of the Son of Man will appear in heaven, and all the tribes of the earth will mourn. They will see the Son of Man coming on the clouds of heaven, with power and great glory. And He will send out His angels with a loud trumpet call, and they will gather His elect from the four winds, from one end of the heavens to the other. (Matthew 24:29-31).
Matthew 24 specifically locates the cosmic disturbances of Revelation 6 immediately after the great tribulation. The rapture becomes imminent after the cosmic disturbances of the sixth seal i.e. it occurs between and the sixth seventh seal. The sixth seal indicates the impending wrath of God, specifically, the chronological sets of seven trumpet and and seven bowl judgements following the seventh seal.
The seventh seal:
Revelation 8 follows an explicit sequence of events:When the Lamb opened the seventh seal, there was silence in heaven for about half an hour. Then I saw the seven angels who stand before God, and seven trumpets were given to them. And another angel came and stood at the altar with a golden censer, and he was given much incense to offer with the prayers of all the saints on the golden altar before the throne, and the smoke of the incense, with the prayers of the saints, rose before God from the hand of the angel. Then the angel took the censer and filled it with fire from the altar and threw it on the earth, and there were peals of thunder, rumblings, flashes of lightning, and an earthquake. Now the seven angels who had the seven trumpets prepared to blow them. The first angel blew his trumpet, and there followed hail and fire, mixed with blood, and these were thrown upon the earth. And a third of the earth was burned up, and a third of the trees were burned up, and all green grass was burned up. (Revelation 8-1-7).
The Fifth Seal Martyrs
This passage indicates that the wrath of God is yet to be discharged. As such, the trumpet and bowl judgments cannot occur before the fifth seal is opened.
2. https://www.newadvent.org/fathers/0712.htm
3. https://biblehub.com/greek/3195.htm
https://www.alankurschner.com/2014/02/22/seals-trumpets-bowls-at-the-same-time-or-one-after-the-other-i-e-concurrent-recapitulation-or-consecutive-https://www.alankurschner.com/2015/06/04/seals-trumpets-bowls-concurrent-recapitulation-or-consecutive-progressive-part-2-of-2-ep-37/
progressive/https://www.alankurschner.com/2017/08/10/articles-for-posttribulationism-to-consider/
https://www.tedmontgomery.com/bblovrvw/emails/prewrathposttrib.html