The San Andrés fault is a continental transforming defect that runs through California from north to south for 1,300 kilometers and that delimits the North American plate from the Pacific plate and is basically found on the Earth's surface.
Above it are the huge urban centers of San Diego and Los Angeles, the second most populous city in the United States. 38 million people live nearby.
Some consider that due to the activity of this fault, whose slippage in the accounts sector is about 25 mm / year and in the furthest 30 mm / year, the Baja California peninsula, located in Mexico, was formed. In addition, the city of Los Angeles is caused to move toward San Francisco Bay at a rate of 4.6 cm per year. Although this action cannot be perceived on a human level, it has caused damage to engineering works such as aqueducts, roads and ranches.
The middle part of the fault broke about 160 years ago and the north part in 1906; Due to that, an earthquake of 7.8 degrees was caused that destroyed a large part of San Francisco and, consequently, three thousand people died.
What experts are most concerned about now is the possibility of the Big One happening, which is a catastrophic earthquake that, according to seismologists, should have already occurred, and would occur in Southern California.
"The information with which we scientists work indicates that the southern end of the San Andrés fault is the one where a major earthquake is most likely to occur in the next 30 years," he told the BBC in July of this year, Jennifer Andrews, seismologist at the California Institute of Technology.
For this reason, they warn of the need to implement security protocols, because an earthquake with these characteristics would cause the death of at least two thousand people, 50 thousand wounded and material losses of 200 million dollars.