In the ScienceAlert article "New estimates suggest the 'big one' in San Andreas could be much worse than we thought" they make the claim that:
Researchers have forecast a mega-quake running the entirety of the San Andreas fault line in California
A major mechanism suggested for this quake is the "creeping zone" of the fault, which is defined in the article as:
The "creeping section" of the San Andreas fault that Page refers to above is a 153-km (95-mile) stretch that bridges the northern and southern segments of the fault.
The article reports that recent modelling has determined that it was possible (just not all that probable) that:
Seismic activity in this creeping section could help trigger a much larger earthquake, enabling a major quake originating on either side to span the north-south divide.
Researching further (as I know better than to trust news sources), in the USGS publication that the article was based on, "The Uniform California Earthquake Rupture Forecast, Version 3 (UCERF3)—The Time-Independent Model", it is still not entirely clear as to how the 'creeping section' of the San Andreas Fault could cause this mega-quake. Hence the question:
What specifically changed in our understanding of the seismicity of the 'creeping section' to claim that it could be a mechanism for a San Andreas megaquake?
I would not be surprised if it is related to the research going on behind simultaneous and near-simultaneous earthquakes in general
