Scientists have believed for decades that the highly active San Andreas Fault in California was unable to create an earthquake that could span the entire state. Scientists believe that the central portion of the San Andreas Fault acted as a natural barrier to prevent a large earthquake in the southern part of California from spreading to the northern part of the state and vice versa. However, new research suggests that a massive statewide earthquake might be possible after all.
Scientists now believe that a massive earthquake that could be felt from San Diego to San Francisco might be possible after all. Using laboratory measurements and computer simulations a pair of scientists has illustrated how a phenomenon known as creeping segments in the fault could behave like locked segments of the fault, building up stress over time and rupturing suddenly. These creeping segments of the fault were long believed to slip slowly and steadily as the tectonic plates shift along the fault line.
The scientists believe that a rupture in creeping segments of another fault is what caused the 9.0 magnitude Tohoku-Oki earthquake that hit Japan in 2011. This earthquake triggered a massive tsunami that led to the death of 16,000 people and major damage to the Fukushima nuclear power plant. Before the massive earthquake, scientists had believed that a massive earthquake was impossible in that area of the fault.
The scientists also point out that a section of another fault believed to be stable ruptured in 1999 causing a 7.6 magnitude earthquake in Taiwan called the Chi-Chi quake. The scientists who believe a major earthquake could be possible along the California San Andreas Fault used the properties of the rock in the area of the Chi-Chi earthquake fault in their computer models. The scientists computer models found that most of the time only the locked area of the San Andreas fault line ruptured. However, the computer models found instances when the simulation resulted in ruptures of the creeping patches well.
Researcher Nadia Lapusta said, “The thinking has been that an earthquake could either occur on the southern San Andreas fault or on the northern San Andreas fault — that the creeping segment is separating it into two halves. But this study shows that if an earthquake penetrates that creeping area in a certain way, it could rupture through it.”
“The San Andreas wouldn’t necessarily snap as the fault in the model did. Sopefully the creeping segment is such that it doesn’t have the propensity for weakness. But without examining further, you can’t say.”
[via LA Times]