Los Angeles is a city of Angels, and of earthquakes. Deadly earthquakes in 1933, 1971 and 1994 have also made it a pioneer in earthquake protection – for example with tough engineering standards to save buildings. Since 2013, with the help of scientists at the US Geological Survey, the city has been developing a resilience plan which culminated in the release of an app that should give residents precious seconds of warning when an earthquake starts. Roland Pease meets the scientists, the Mayor and the officials making the system work.

Picture: An apartment after the Northridge earthquake in 1994