A recent study found that the southern portions of the San Andreas fault and parts of the adjacent San Jacinto fault line are locked and loaded to their highest stress levels in 1,000 years. This increases the probability of a significant earthquake in the region.

Earthquake Risk

The study revealed that the stress has been accumulating for more than a century along the southern San Andreas and San Jacinto fault systems. Both fractures make up the boundary of the Pacific and North American tectonic plates, which have been sliding past each other a few centimeters each year while other zones are locked.

The researchers say that the chances are more than 50 percent that an earthquake of 6.7-magnitude or higher occurs along the southern stretch of the San Andreas fault in upcoming decades. The San Andreas and San Jacinto fault systems also meet at a junction called the Cajon Pass, which can either stop or transmit large ruptures between the two faults.

Consequences of a Joint Rupture

If an earthquake were to travel through the Cajon Pass and along both faults, scientists say the consequences would be severe and widespread, affecting critical infrastructure such as major highways, railways, and energy corridors over several cities simultaneously.

The researchers reconstructed the last 1,000 years of seismic activity along the two faults, tracking how stress accumulated and released. They found that earthquakes passed through the junction when both sides of the pass had similar levels of high stress – and “that is the configuration we are approaching today,” said Liliane Burkhard, the study’s lead author.

Original reporting: KEYT (Ventura/Santa Barbara) — read the source article.