The 2007 Working Group on California Earthquake Probabilities reported that "the likelihood of [an earthquake in California] of magnitude 7.5 or greater in the next 30 years is 46%." The report noted that "[t]he final forecast is a sophisticated integration of scientific fact and expert opinion" (source: https://pubs.usgs.gov/fs/2008/3027/fs2008-3027 .pdf).
Explain whether the figure of 46% is based on personal probability, long-run relative frequency, physical assumptions about the world, or some combination.