Aftershocks of the Northridge quake

Twenty years ago today, much of Los Angeles was shaken awake at 4:31 a.m. by a magnitude 6.7 earthquake on a blind thrust fault that scientists didn’t know existed. The Northridge quake (which was actually centered under Reseda) left 57 people dead, turned the 10 Freeway into a concrete version of a broken Kit Kat bar, caused $20 billion in property damage and made the Santa Susana Mountains on the northern edge of the San Fernando Valley two feet taller.

Since then, we have gotten smarter about earthquakes and buildings. Scientists have a better understanding of the faults beneath Southern California and have discovered more of them, including the Puente Hills blind thrust fault that spreads out under Los Angeles and runs directly below downtown. (It is capable of a magnitude 7.3 or 7.4 quake, geologists say.) The California Geological Survey has mapped 550 surface faults — the kind that rupture on the surface and tear apart the foundation of a building — and set zones inside which developers must do extensive testing before building. In the last 20 years, the Geological Survey has also produced 90 maps pinpointing areas of the state in danger of landslides or liquefaction. New construction since Northridge meets higher standards and probably won’t collapse in a comparable quake.

But there is much more that both government and private business should — and can — do to make Los Angeles sturdier for the next big earthquake and its aftermath. A building that didn’t collapse and kill you might nevertheless be so profoundly damaged that it’s uninhabitable. If a business owner wants his or her business to function soon after an earthquake, that means building beyond the minimum standards of the current code. It is promising that Mayor Eric Garcetti is creating a formal partnership with the U.S. Geological Survey to develop comprehensive earthquake strategies for the city.

PHOTOS: The 1994 Northridge earthquake

Additionally, there are thousands of older concrete and so-called soft-story buildings that need to be inventoried, inspected and probably retrofitted. The L.A. City Council is already looking into possible financial help for property owners.

And even though the state geologist has produced hundreds of maps of surface faults, the office still has 300 to go. Gov. Jerry Brown has proposed increasing funds to the California Geological Survey to allow about half a dozen staff members to continue mapping. State geologist John Parrish estimated it would take them six to 10 years to finish the task. If Brown’s new funds are not approved and the office is left with only one person mapping, Parrish estimated it would take 300 years. That’s too long to wait.