Full seismic and tunneling reports on Westside Subway Extension are now online

Lucy Jones, a seismologist with the U.S. Geological Survey, explains faulting to reporters after yesterday's Board committee meeting. Photo by Gayle Anderson/Metro.

The pair of reports on tunneling safety and seismic issues involving the Westside Subway Extension between Beverly Hills and Westwood have been posted online.

The reports were the basis for yesterday’s oral report to the Board of Directors by a variety of engineers, geologists and seismologists. The gist of it: they recommended a station along Constellation Boulevard in Century City to avoid two active earthquake fault zones in the area. They also said that tunneling under the Beverly Hills High School would not compromise the safety of students or the structural integrity of any buildings — or prohibit future development on the campus. Here’s the story on The Source.

A few additional thoughts, having had the chance to see some of the reaction:

•The material in the reports has not been known for a year, as has been alleged by the Beverly Hills Unified School District. Drilling and soil tests began last December — as we posted then — and continued for many months. Logs showing the dates for the different tests, which largely took place between last winter and early this summer, are in the appendices of the Fault Investigation Report. (see above link). The time since was spent doing more tests, analyzing and interpreting the results, writing the reports and having them independently reviewed by other experts. In September, a judge ruled that Metro did not violate the California Public Records Act by withholding any documents. And now, with the information finalized, it is being made public for any and all to scrutinize.

•The reports, as the scientists explained yesterday, are notable because it was the first time that the  location of two faults — the Santa Monica Fault and West Beverly Hills Lineament — were precisely mapped in the Century City and Westwood area. The faults appeared on maps, but this kind of field work had not been done. As a result, much more is known about the location of different strands of the faults in the area. Dr. Lucy Jones, the well-known seismologist with the U.S. Geological Survey and the California Institute of Technology, explained it well: it’s hard and expensive to do detailed seismic studies in areas that are heavily urbanized because a lot of surface features have been paved over and developed. That means a lot of underground work has to be done and that’s not easy. In this case, it was done because Metro had to have the information before attempting to tunnel for a subway in the area.

•The reports do not conclude — or even suggest — that development is going to be shut down between Beverly Hills and the ocean, as some have written. On that note, the Century City area is not a state-designated Alquist-Priolo Earthquake Fault Zone. What’s that mean? “The intent of the AP Act is to ensure public safety by prohibiting the siting of most structures for human occupancy across traces of active faults that constitute a potential hazard to structures from surface faulting or fault creep,” according to the state. Should it be? That’s a decision ultimately up to the state geologist. Even then, the AP Act doesn’t necessarily shut down development. Here’s an explanation from the state’s website answering the question “How does the law work?” when it comes to new development:

The law requires the State Geologist to establish regulatory zones (known as Earthquake Fault Zones) around the surface traces of active faults and to issue appropriate maps. ["Earthquake Fault Zones" were called "Special Studies Zones" prior to January 1, 1994.] The maps are distributed to all affected cities, counties, and state agencies for their use in planning and controlling new or renewed construction. Local agencies must regulate most development projects within the zones. Projects include all land divisions and most structures for human occupancy. Single family wood-frame and steel-frame dwellings up to two stories not part of a development of four units or more are exempt. However, local agencies can be more restrictive than state law requires.

Before a project can be permitted, cities and counties must require a geologic investigation to demonstrate that proposed buildings will not be constructed across active faults. An evaluation and written report of a specific site must be prepared by a licensed geologist. If an active fault is found, a structure for human occupancy cannot be placed over the trace of the fault and must be set back from the fault (generally 50 feet).

•The media — the few which actually showed up — had a chance to ask the experts questions following their presentation to the Board. I asked about the number of earthquakes that actually takes place on both faults. The answer: there hasn’t been much activity on the Santa Monica Fault, whereas there have been some notable quakes on the Newport-Inglewood Fault, of which the West Beverly Hills Lineament has now been shown to be an extension (the Newport-Inglewood caused the damaging 1933 Long Beach earthquake). As the scientists explained, some faults produce lots of little quakes, other faults don’t. That doesn’t suggest they’re any less dangerous.

 

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