SANTA MONICA FAULT ZONE

What is a fault investigation?

 

A fault investigation is an investigation to locate existing faults and estimate the age of the most recent movement. A fault is considered active if there is evidence of seismic activity in the last 11,000 years. There are several methods of performing fault investigations, the most common being trenching. Trenching consists of  digging trenches on a property to expose the subsurface stratigraphy and mapping important geologic features along the exposed trench wall.  The size and depth of trenches will vary from site to site. Another common method, which is generally paired with trenching, is using cone penetration test (CPT) soundings and geotechnical soil borings closely spaced together to create a transect which can then be used to create a geologic profile of the site. Group Delta is staffed with certified geologists experienced in both methods.   

 

https://www.youtube.com/watch?v=BDl6ifWVX6Q&feature=youtu.be

http://www.conservation.ca.gov/cgs/information/publications/cgs_notes/note_49/Documents/note_49.pdf

 

How long does an investigation take and how much can I expect to pay?

 

There are no two sites which are identical, so standardizing a flat cost and time frame is impossible. Give us a call, and we will be glad to provide you with an estimate.

 

How do I know if I am required to conduct a fault investigation?

 

The California Geological Survey has Earthquake Fault Zone maps available to download here, though some zones of required investigation have not yet been mapped. Depending on the location and jurisdiction, some cities will publish their own temporary zones of required investigation (e.g. City of Santa Monica Fault Hazard Management Zone, City of Los Angeles Preliminary Fault Rupture Study Area). If you are unsure if you are within a required fault investigation zone, Group Delta can provide you with a no-cost/no-obligation site-specific review of your property.

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Are fault investigations required for all buildings within a fault study zone, or are there exceptions?

 

The California Geological Survey states: “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.”

 

My property lies within the fault study zone, now what?

 

If your property is developed, you will not need to conduct a fault investigation unless you would like to remodel or add to the existing structure. For new developments, a fault investigation will be required to demonstrate that the proposed development will not be constructed over active faults. Give us a call at 310-320-5100, and we can discuss your options.

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If an active fault is on my property, do I need to publically disclose that information?

 

According to the California Geological Survey,

 

“The fact that a property is located in an Earthquake Fault Zone must be disclosed to a potential buyer before the sales process is complete. The real estate agent is legally bound to present this information to the buyer. When no realtor is involved, the seller must inform the buyer directly. This is usually done at the time an offer is made or accepted.

 

Effective June 1, 1998, the Natural Hazards Disclosure Act requires that sellers of real property and their agents provide prospective buyers with a "Natural Hazard Disclosure Statement" when the property being sold lies within one or more state-mapped hazard areas, including Earthquake Fault Zones.”

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Can I construct a building over an active fault trace? How far away does my building need to be offset from an active fault?

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No. If an active fault has been mapped on your property, the planned construction will generally need to be offset about 50 feet away from the active fault trace. There is currently no minimum setback distance. Group Delta can perform state-of-the-art probabilistic rupture potential analyses to estimate the displacement along an active fault and, in some cases, reduce the offset.

 

Can more than one consultant conduct a fault investigation on my property? What if their findings are not in agreement?

 

Yes. Ultimately, the local or state government agencies will deem the consultant’s conclusions acceptable or not.