In the recent draft codes released by BIS on IS 1893 Part 1 & 2, The zone factor is hiked based on PSHA. When I was searching for whether such analysis gives accurate values, I got this reference.
Mulargia, F., Stark, P.B., and Geller, R.J. (2017) “Why is Probabilistic Seismic Hazard Analysis (PSHA) still used?”, Physics of the Earth and Planetary Interiors, Volume 264, Mar., p. 63-75. DOI: 10.1016/j.pepi.2016.12.002
Even though it has never been validated by objective testing, Probabilistic Seismic Hazard Analysis (PSHA) has been widely used for almost 50 years by governments and industry in applications with lives and property hanging in the balance, such as deciding safety criteria for nuclear power plants, making official national hazard maps, developing building code requirements, and determining earthquake insurance rates. PSHA rests on assumptions now known to conflict with earthquake physics; many damaging earthquakes, including the 1988 Spitak, Armenia, event and the 2011 Tohoku, Japan, event, have occurred in regions relatively rated low-risk by PSHA hazard maps. No extant method, including PSHA, produces reliable estimates of seismic hazard. Earthquake hazard mitigation should be recognized to be inherently political, involving a tradeoff between uncertain costs and uncertain risks. Earthquake scientists, engineers, and risk managers can make important contributions to the hard problem of allocating limited resources wisely, but government officials and stakeholders must take responsibility for the risks of accidents due to natural events that exceed the adopted safety criteria.
I am surprised that PSHA has not been validated and BIS is changing the codes based on such an unreliable method and increasing the cost of construction of all future buildings considerably and at the same time making all the available buildings and those under construction as UNSAFE!