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Fault Hazard Investigations

The California Geological Survey has zoned certain urbanized sections of areas throughout California to be within 'Earthquake Fault Zones', as per the Alquist-Priolo Earthquake Fault Zoning Act of 1972. Before a property is sold, or new construction is proposed for human occupancy within an Earthquake Fault Zone, the property owner or buyer needs to perform a "due diligence" geological evaluation of the property to satisfy the reviewers of the state, county, or city with respect to this Act.

Group Delta has a complete staff of geologists, including expert paleoseismologists, who have evaluated sites throughout Southern California to facilitate land acquisition and land development planning, and project design. We are experienced in evaluating properties for fault rupture hazards according to the standards mandated by this Zoning Act.

A Fault Hazard Investigation usually involves the following:

Desk study. Reviewing published maps and reports to identify known exposed or concealed faults that could pose a potential fault rupture hazard at the study site.

Performing seismic reflection, closely spaced cone penetration tests, or geotechnical borings with continuous sampling to identify stratigraphic offset that might indicate faulting.

Evaluating the age of the fault. This may involve fault trenching or radiocarbon dating. A fault that ruptures through material younger than 11,000 years is defined as an active fault.

Recommending mitigation measures. This may involve establishing a building setback zone.






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