If the earth under SA is porous, and the day the event was filmed has especially low barometric pressure, then an easy explanation is release of trapped, compressed air. The air would want to seep out everywhere, but if there were a weak point (where the overlaying sand was shallowest and therefore weighed the least) more air would rush out there than anywhere else, and if the sand were blown out, it would represent an even smaller resistance to the continued release of trapped air from that same place. So it all vents from right there.
Makes sense.
Since there appears to be little accumulation of new sand, obviously what is erupting is a clear gas. Most likely, air.
Maybe the inlet is a cave far away.
The site which previously contained the oil is no longer capable of supporting the sand above it and collapsed which compressed the air and the pressure from the compressed air is what is blowing the sand out.
If it was only the sand slowly collapsing from the surface, there would be no indication of an earthquake deep down below. I would imagine that the outburst would eventually stop if it hasn't stopped already.
If we consider that there streams of water flowing underground which leave open channels after the water is gone, then there would be open channels which allowed the compressed air to be blown from miles away from where it finally exits at the weakest place.
I noticed while watching the video that there were pulses of air and sand exiting which would be consistent with an ongoing process where once the sandy earth started collapsing, the condition continued in spurts and the site of the collapse kept expanding with new failures,