In an effort to be more consistent with other providers of hazard information, ABAG replaced previous shaking scenarios maps, which did not include the newest ground motion prediction equations (GMPEs), with the updated USGS scenarios. In general the public does not have easy access to these scenarios through the CISN website and they are not accompanied by information for the lay user about hazard or appropriate actions. In general, shaking maps are developed by assuming a fault segment and a rupture length and using ground motion attenuation relationships to estimate ground motion at locations away from the fault.

USGS, through the California Integrated Seismic Network (CISN) updated their ShakeMap scenarios with updated GMPEs. The scenarios chosen were based on the Working Group on California Earthquake Probabilities’ (Working Group) Uniform California Earthquake Rupture Forecast (UCERF3). Ground motions were estimated using an attenuation relationship using Boore et al (1997) for peak and spectral acceleration and Joyner and Boore (1988) relationship for peak velocity. Site conditions are taken from Wills et al (2000) , and site correction amplification comes from amplitude and frequency-dependent factors from Borcherdt (1994). This method does not consider rupture direction or directivity. The approach only gives average peak ground motions, so actual ground motions may vary significantly.