Fault Rupture Investigations

Century City and Beverly Hills, California
Client
Westfield USA I Crescent Heights Confidential

Services

Geotechnical Engineering
Engineeering Geology

Geocon Leaders

Gerry Kasman
Susan Kirkgard



Two complex fault zones converge in the densely developed Century City – Beverly Hills area: the Santa Monica Fault Zone and the West Beverly Hills Lineament. Geocon provided consultation services and performed site-specific fault rupture hazard investigations for three large-scale developments within several adjacent city blocks that were potentially impacted by these faults. The developments included proposed high-rise tower developments at the Westfield Century City Mall and 10000 Santa Monica Boulevard and a proposed mid-rise mixed-use development for a confidential client in Beverly Hills. These three planned developments were in various stages of the permitting process and were considered “free of active faulting” until a 2011 seismic study for the Los Angeles County MTA Subway Extension raised concerns of active faulting and halted the planned developments.

Investigation of these developments was extremely challenging due to the dense urban environment. The Westfield site was completely developed and required a combination of specialized exploration techniques that included continuous-core borings, cone penetration tests, and high-resolution seismic reflection surveys to investigate faults identified by the 2011 transportation study that traversed the mall site and specifically the proposed tower site. In contrast, the vacant 10000 Santa Monica site allowed for more typical fault investigation methods that included the excavation of a 25-foot-deep, 325-foot-long trench across the site to investigate the faults mapped through the site. Detailed analysis of geologic units encountered in the explorations and correlation of pedogenic soil development suggested that the faults mapped as traversing the site were not active. Detailed pedogenic analysis and geomorphic analysis was performed to estimate the relative age of unfaulted geologic units at the sites.

Geocon’s geologic staff has over 25 years of experience performing fault investigations in both urban and rural environments on the many major faults throughout California. This experience combined with proactive collaboration with the client, client counsel, city geologists, and independent reviewers throughout the project duration and a proven track record for first-time agency approval resulted in a substantial client benefit. All three developments were found to be free of active faulting and in some cases, we were able to demonstrate with a very high level of confidence that the mapped faults did not exist.

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