Are you basing the damage estimates on the largest quake that could strike nearby?

No, we are basing them on the shaking caused by all likely earthquakes, near and far, large and small.

Are you predicting earthquakes?

No, we are not: earthquakes cannot be predicted. The forecasts are based on the long term behavior of faults, using the best public scientific data available.

My house did fine in the 2014 M=6.0 South Napa, 1989 M=6.9 Loma Prieta, or 1994 M=6.7 Northridge shock, so why should I care?

Only if you lived in Napa, the Santa Cruz Mountains, or Northridge, would these earthquakes have tested your home’s seismic resilience. For most of us, they were too far away to matter.

Does a hazard rank lower than, say, 30 mean I am in the clear?

Unfortunately, it does not. For example, the 2003 M=6.6 San Simeon, 1992 M=6.5 Big Bear, 1952 M=7.3 Kern County, and 1933 M=6.4 Long Beach, California shocks all struck where the hazard was less than 30.

If my hazard rank is high, why is the chance of experiencing no damage also high?

That’s how it works with earthquakes: Strong shaking is rare but damaging. Even in California, most homes have not suffered damage in the past 30 years, consistent with this assessment.

Why should I protect myself when the chance of major damage over 30 years is, say, 1 in 20?

To put it in perspective, your chance of getting sued, totaling your car, or burning down your house is lower than 1 in 20, and yet you probably protect yourself from these.