Quake-proofing Hollywood

California is a messy quilt of earthquake faults. The Alquist-Priolo Earthquake Fault Zoning Act, passed after the 1971 Sylmar earthquake, requires the state to map those faults that are deemed to be active and to set zones around them. Developers who want to build housing within those zones must perform geological testing to determine that their sites don’t straddle a fault line that could rupture the surface. In the event of an earthquake, a building set on such a fault line could not escape being cracked like a coconut as its foundation was forced to move in opposite directions.

The Hollywood fault runs east and west through the heart of Hollywood, not in one single line but in strands, paralleling Yucca Street — where it has headed smack into a development boom. It is an active fault line that has been deemed capable of rupturing the surface, and it now appears that a trio of massive developments — one already under construction, one just approved and the other approved last year — could be sitting closer to the fault line than the developers initially realized.

In all three cases, the developers performed some seismic studies and concluded that their projects were not near enough to fault lines to cause problems. But faults are tricky. The city has a map of the Hollywood fault zone. But the state geologist is currently remapping the fault in greater detail, and that map will probably revise the location of the fault zone. Once that state map is completed, any proposed development that sits within roughly 500 feet of either side of the fault will be compelled to perform extensive geological testing to see exactly how close it comes to the actual fault line. If it’s on the fault line, building permits cannot be issued.

But the city doesn’t have to wait for the new map to be released. And it shouldn’t. The city should insist, beginning immediately, that developers who intend to build in the vicinity of a mapped fault that could crack on the surface must dig a trench and look for the fault line before their project can be approved. Trenching is the smartest, safest and most precise way to determine how close a proposed building sits to a fault that could devastate it.

Sure, there are structures on active surface faults in Los Angeles — structures built long before the state began placing restrictions on them. And many other faults are not readily apparent to geologists: No one knew there was a blind thrust fault under Northridge until it ruptured catastrophically in 1994. But we do know about the dangers of the Hollywood fault and numerous others. We have techniques for determining whether a proposed development is sitting on them. Let’s require developers to use those techniques.