A large buildup of strain in the San Andreas fault makes a quake imminent:
Fialko gathered eight years’ worth of radar data from European Space Agency satellites that measure in detail how the ground moves. He also added 20 years’ worth of data from global-positioning measurements on the ground.Taken together, he says, the measurements suggest that the two plates either side of the southern San Andreas are slipping past each other at around 25 millimetres per year. Without a recent earthquake to alleviate that strain, Fialko says, the fault line itself, which has remained essentially static for centuries, has built up between 5.5 and 7 metres of ‘slip deficit’.
If released all at once, that could result in a magnitude-8.0 earthquake, he says, roughly the size of the devastating 1906 quake in San Francisco. Such a powerful event might threaten even those buildings constructed to earthquake specifications.