Quake Forecast: California Faults
4 faults, the Hayward, Rodgers Creek, Green Valley and the Calaveras fault, connected to the infamous San Andreas Fault, are thought to be releasing their built up pressure at the same time. These faults are directly under many suburban and poorly built areas, so damage and death tolls will be high.
"The Hayward Fault is just right in the heart of where people live, and the most buildings and the most infrastructure,"
Estimates by professions have put the Hayward and Calaveras Fault at a 6.8 magnitude, Rodgers Creek and Green Valley at 7.1. These all could potentially go off at the same time, as the first one would set off the next one, and so on.