Simi Valley sits in a seismically active part of Southern California. The Simi-Santa Rosa fault runs along the southern edge of the valley, the San Cayetano fault sits to the north, and the 1994 Northridge earthquake — though centered to the south — produced significant shaking and damage across Simi. This page summarizes the local seismic context using USGS and California Geological Survey sources, explains what liquefaction zones are and where they sit in the city, covers what inspectors look for in older homes, and gives realistic cost ranges for common retrofits.
The faults that matter for Simi Valley
The Simi-Santa Rosa fault is the nearest named active fault to the city, running along the southern edge of the valley. The San Cayetano fault sits to the north of the city. The Northridge blind-thrust fault, which produced the 1994 M6.7 earthquake, lies to the south in the San Fernando Valley. The Santa Susana fault sits along the eastern hills.
USGS publishes the most current fault mapping at earthquake.usgs.gov. The California Geological Survey publishes Alquist-Priolo Earthquake Fault Zone maps that identify where active faults are known to cross the ground surface. Construction across an Alquist-Priolo zone is restricted by state law.
What the 1994 Northridge earthquake did in Simi
The Northridge earthquake produced strong ground motion across Simi Valley despite the epicenter being south of the city. Damage in Simi included chimney failures, broken gas lines, and structural damage to older homes with weak foundation connections. The event is the most important data point for understanding what a major regional earthquake feels like at any given Simi address.
Most newer Simi construction (post-1980) performed substantially better than older construction. Building codes were strengthened in response to the 1971 San Fernando earthquake and again after Northridge. Homes built to the post-1995 code have meaningfully better seismic performance than pre-1980 homes.
Liquefaction zones in Simi Valley
Liquefaction is the process where saturated, loosely consolidated soils behave like a liquid during strong shaking. The California Geological Survey publishes Seismic Hazard Zones maps that identify areas of potential liquefaction. Portions of Simi Valley along the Arroyo Simi and other drainage corridors fall within mapped liquefaction zones.
If a parcel sits inside a mapped liquefaction zone, the natural-hazard disclosure provided to buyers will note this. The disclosure does not mean the home is unsafe; it means a site-specific geotechnical evaluation may be warranted for new construction or major additions, and that the buyer should understand the increased risk relative to non-zoned parcels.
What inspectors look for in older homes
Standard items a qualified inspector will check on a pre-1980 single-family home: whether the wood framing is bolted to the concrete foundation, whether cripple walls (short stud walls between the foundation and the first floor) are braced with structural plywood, whether the water heater is strapped, whether masonry chimneys show cracking, and whether any unreinforced masonry is present.
Two-story homes built before about 1980 sometimes have soft-story conditions where a wide garage opening sits below living space. Soft-story conditions are much more common in multi-family apartment buildings than in Simi single-family homes, but they can exist.
- Foundation bolting (sill plate to foundation)
- Cripple-wall bracing (structural plywood)
- Water-heater strapping (two straps)
- Masonry chimney condition
- Unreinforced masonry walls
- Soft-story conditions over garage openings
- Gas-line shutoff accessibility
Cost ranges for common retrofits
Foundation bolting and cripple-wall bracing for a typical single-story Simi home generally runs $3,000 to $8,000 depending on access and the linear footage of cripple wall. Costs increase if access under the home is tight or if extensive sister-blocking is required.
The California Residential Mitigation Program (CRMP) Earthquake Brace + Bolt grant has historically provided up to $3,000 toward this work for eligible homes. Eligibility windows and amounts vary year to year; check the program website for the current cycle. Other retrofits — chimney rebuilds, additional shear-wall work — vary widely.
Insurance — the California Earthquake Authority
Standard homeowners insurance does not cover earthquake damage. Coverage is available primarily through the California Earthquake Authority (CEA), with policies sold through participating carriers. Premiums depend on location, construction type, year built, and whether the home is retrofitted.
Deductibles on CEA policies are significant — typically 5 to 25 percent of the dwelling-coverage amount. The math on whether to carry a policy is a function of equity, deductible percentage, and personal risk tolerance. Get a quote during escrow rather than after move-in.
Buying an older home — questions to ask
For homes built before 1980, ask whether the foundation has been bolted, whether cripple walls have been braced, and whether the chimney has been rebuilt or removed. Ask for permits or receipts. If no documentation exists, assume the work has not been done and factor a retrofit cost into your decision.
For homes built 1980 to 1995, the structural connection standards were improving but were not at the post-Northridge level. A seismic inspection by a qualified contractor or engineer is still worthwhile. For post-1995 homes, the building was designed to a stronger seismic standard but the same questions about water-heater strapping and chimney condition still apply.
Preparation that does not require retrofitting
Securing tall furniture to wall studs, strapping the water heater, installing an automatic gas shutoff valve, and keeping a basic emergency kit in the home are inexpensive steps that reduce the day-of risk and the post-event inconvenience. None of these require structural work.
Knowing where your gas shutoff valve is, and owning the correct wrench for it, are two of the cheapest and most useful pieces of earthquake preparation for any Simi Valley home.
Where to verify the data yourself
USGS Earthquake Hazards Program (earthquake.usgs.gov) provides national and state-level seismic-hazard data. The California Geological Survey publishes Alquist-Priolo Earthquake Fault Zone maps and Seismic Hazard Zones (liquefaction, earthquake-induced landslide). The City of Simi Valley building department can confirm permit history for any address.
The natural-hazard disclosure provided during escrow will note whether the parcel is inside any state-mapped hazard zone. Read it carefully — it is one of the most useful documents in the disclosure package.
Frequently Asked Questions
Is Simi Valley on a fault?
The Simi-Santa Rosa fault runs along the city's southern edge. Multiple other regional faults sit within shaking distance, including the Northridge blind-thrust fault to the south.
Did Simi Valley suffer damage from the Northridge quake?
Yes. The 1994 Northridge earthquake produced strong ground motion across Simi, with damage including chimney failures and structural damage to older homes with weak foundation connections.
What is liquefaction and where does it apply in Simi?
Liquefaction is when saturated, loose soils behave like a liquid during strong shaking. CGS Seismic Hazard Zones maps identify potential zones in Simi along the Arroyo Simi and other drainage corridors.
How much does a foundation retrofit cost?
Foundation bolting and cripple-wall bracing for a typical single-story Simi home generally runs $3,000 to $8,000 depending on access and cripple-wall length.
Does homeowners insurance cover earthquake damage?
No. Earthquake coverage is sold separately, primarily through the California Earthquake Authority via participating carriers.
Is the Earthquake Brace + Bolt grant still available?
Eligibility cycles and grant amounts vary year to year. Check the California Residential Mitigation Program website for the current cycle.
Are newer Simi homes safer in an earthquake?
Post-1995 homes were designed to stronger seismic connection standards adopted after the Northridge earthquake. They generally perform better than pre-1980 homes.
