In the next 30 years, scientists predict at least one earthquake
of magnitude 6.7 or higher will hit the state.
In the next 30 years, scientists predict at least one earthquake of magnitude 6.7 or higher will hit the state.
Using a new model that compares earthquake likelihood throughout all of California, the 2007 Working Group on California Earthquake Probabilities, a collaboration of scientists and engineers, can predict with more certainty than ever before the probability of an earthquake hitting California.
The new forecast shows a 99.7 percent chance of an earthquake of magnitude 6.7 or higher and a 46 percent chance of an even more powerful quake – magnitude 7.5 or higher – rattling the state in the next 30 years. However, a quake of that magnitude is more likely to hit the southern part of the state, scientists said. This forecast is a “sophisticated integration of scientific data and expert opinion,” said Tom Jordan, director of the Southern California Earthquake Center.
“This new, comprehensive forecast advances our understanding of earthquakes and pulls together existing research with new techniques and data,” U.S. Geological Survey geophysicist and lead scientist Ned Field said. “Planners, decision makers and California residents can use this information to improve public safety and mitigate damage before the next destructive earthquake occurs.”
Experts gathered at a news conference Monday morning to discuss the results of the model and present their findings to the public. They chose to use the reference point of a 6.7 magnitude earthquake because that was the size of the Northridge quake that hit the state in 1994, killing 57 people and wreaking $40 billion in economic damage. The 30-year time frame was chosen because it’s the typical duration of a home loan, Field said.
The working group plans to provide their findings to decision makers who establish local building codes, earthquake insurance rates and emergency planning.
The model allows scientists to compare the likelihood that earthquakes of varying magnitudes will hit the Los Angeles and San Francisco Bay areas and several large faults. The southern San Andreas and Hayward-Rodgers Creek faults are likely sources for high-magnitude seismic activity over the next 30 years, and claim a 59 percent and 31 percent chance of generating a 6.7 or higher magnitude quake, respectively, scientists said. Additionally, scientists predict that there is a 10 percent probability that a quake of magnitude 8 to 9 will hit along the offshore 750 mile long Cascadia Subduction Zone, the southern part of which extends about 150 miles into California. Quakes of this magnitude occur only about once every 500 years on average, the group said.
While the group recognizes that they cannot make predictions specific to the date, time and place of a future quake, they hope that Californians will use the probabilities to plan and prepare for future quakes. The group said the results serve as a reminder that Californians live in “earthquake country” and, through prudent planning and preparedness, can minimize the unpredictable damage of future earthquakes.
