The paired pashta on consecutive syllables seems to be a particular prophetic motif in the music. The image shows that this pairing is often combined with the single note dip of the zaqef qatan.
It does not occur in the Psalms. In the examples I have so far, I found 13 in Nahum, several in Jonah, several in the Song, where it might represent a kiss (early program music - will come back to this), and in Amos, Esther, and Isaiah. I even note one usage in the Song of Hannah in 1 Samuel 2 - showing that these poems in the prophetic books are different in their music from the psalms. The same sign is used in the Psalms, but not in a paired form.