Southern California Earthquake Data Center

Earthquake Information

Earthquake Preparedness

Earthquake Probabilities

 

One of the primary goals of earthquake research is to be able to reliably predict events. While the fullfillment of this goal is currently out of reach, we can at least make estimates of the probability of earthquakes, given certain circumstances.

 

The following list details some of the computed probabilities for events in Southern California.

 

  • Probability of an Aftershock One Unit of Magnitude Smaller
    (e.g., a M5 aftershock to a M6 mainshock)


    within 1 day: 28%
    within 7 days: 40%
    after 7 days, but within 1 year: 26%

 

  • Probability of a Larger Earthquake at the Same Place


    within one hour: 1.5%
    within three days: 6%

 

  • Probability of an Earthquake One Unit of Magnitude Larger
    (e.g., a M6 mainshock to a M5 foreshock at the same place):


    within three days: 1%

 

  • Probabilities of a Future Large Earthquake May Be Higher Near a Fault Large Enough to Produce a Big Earthquake
    (e.g., the San Andreas)


    Probability of a M7.5 earthquake in the three days after a M6 in the southern Coachella Valley: 0.2%

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