California’s top geologist has said the 6.0 earthquake in Napa Valley Sunday surprised seismic scientists because it appears to be linked to an obscure fault that had previously been deemed inactive.
“We would not have predicted an earthquake on this particular fault,” Dr. John Parrish, the chief of the California Geological Survey, told Sacramento TV station KCRA (link to KCRA report). Parrish said the Carneros fault, now believed to be the source of the Napa Valley earthquake, was previously deemed inactive because it had not produced any quake activity in the past 150,000 to 200,000 years.
The Napa Valley quake on the Carneros fault “tells us we can have a magnitude 6.0 anywhere,” Dr. Parrish told KCRA. “It tells us they [earthquakes] are unpredictable. We would not have predicted an earthquake on this particular fault.”
Dr. Parrish’s observations “should be a wake-up call for LA city officials and residents” because even the geologist hired by the developer of the controversial twin-skyscraper Millennium project in Hollywood has conceded there are faults on the Millennium site,  said attorney Robert P. Silverstein, who represents community activists fighting the Millennium twin-skyscraper project.
“Opponents of the Millennium project have believed all along that the faults underlying the Millennium site are active,” Silverstein added. “Now we are finding that even very ancient and supposedly inactive, minor faults can suddenly spring into action and pose a threat to life and property. It begs the question: do we need more safety limits than we have now on major construction on top of faults?”
KCRA also reported Dr. Parrish said the Napa Valley earthquake could force officials statewide to reassess the risk posed by faults that are not now deemed active and dangerous.
“The Millennium developer must be quaking in his boots over the prospect that the Napa Valley quake might trigger a rewrite of the rules about what constitutes an active fault and how we protect our citizens from construction on properties with faults on them,” said George Abrahams, a Hollywood community leader and Millennium project opponent.
Dr. Parrish is the official who will make the final determination about the Hollywood Fault map, including whether the fault is active and runs through the Millennium property, the site for a proposed 1.1 million square foot development involving two skyscrapers 39 and 35 stories tall.
State law forbids construction of a habitable structure within 50 feet of an active earthquake fault. California government rules now say faults are active if they have experienced earthquake activity within the past 11,000 years. Faults that have had no earthquake activity within the past 11,000 years are considered inactive. Under current rules, construction can proceed on top of an inactive fault.
The California Geological Survey, which Dr. Parrish heads, produced a preliminary map in January showing the path of the Hollywood Fault. This map showed two traces of an active fault crossing the Millennium site. State law, however, gives property owners the right to challenge those preliminary maps. As part of that process, the Millennium hired Group Delta, a geology firm, to dispute the preliminary map.
Group Delta recently claimed it found no active faults on the Millennium property after digging several deep trenches on and near the property. But Dr. Parrish told the LA Times Group Delta’s 4-page report contained none of the technical material needed to support the clean bill of health it gave its client, Millennium Partners. Dr. Parrish has given the Millennium team 90 days to submit its technical data to his office for review.
Dr. Parrish also told the Times that members of his own staff were only briefly allowed to inspect Group Delta’s trenches, and that they were barred by Millennium from taking photos or making drawings of the geological formations exposed by the trenching and were barred from asking questions of the Millennium team’s workers and consultants.
The trenches have now been filled in and covered up.
“The trenches have been covered-up – that’s very symptomatic of what’s been going on at the Millennium site for some time,” said Silverstein. Silverstein is suing the city of Los Angeles, claiming city officials suppressed ample evidence of faulting on the Millennium property. “The Millennium cover-up is the result of the culture of secrecy, law-breaking and backroom deal-making that prevails at LA City Hall.”
 “These minor faults are attributed to tension faulting localized on the crest of a previously un-mapped anticline which was observed in the trenches of site 2 [located on the Millennium property], 3 and 4…[These faults also] became inactive prior to the Holocene.” Source: Delta Group report, Aug. 5, 2014, p. 2 paragraph 7. Currently, only faults that have experienced earthquake activity during the Holocene period (approximately from 11,000 years ago to the present) are deemed active.