The San Fernando Valley has specific earthquake risk. The 1971 Sylmar earthquake (6.6) and the 1994 Northridge earthquake (6.7) both caused major structural damage to homes throughout the Valley — particularly homes without adequate seismic upgrades. The same fault systems remain active.
The Valley's Seismic Context
The Valley is crossed by several active fault systems:
Sierra Madre fault system: Runs along the foothills at the northern Valley edge (Sylmar, Mission Hills, Granada Hills). This fault produced the 1971 earthquake.
Northridge blind thrust fault: The source of the 1994 earthquake. A "blind" fault (doesn't surface) running under the Valley.
San Andreas fault: While not under the Valley, a major San Andreas event would generate significant shaking in the Valley (estimated MMI VII–VIII in parts of the Valley).
The USGS estimates a 60% probability of a 6.7 or greater earthquake in the greater LA region within the next 30 years.
Upgrade Types by Structure
Wood-Frame Homes on Raised Foundation (Most Common Valley Home Type)
The two primary interventions are cripple wall bracing and anchor bolts:
Cripple wall bracing: Short stud walls between the foundation and first floor. Unbraced, they can collapse in an earthquake. Adding plywood sheathing to these walls (per FEMA P-1100 or City of LA Standard Plan) is the single most effective seismic retrofit for most Valley homes.
Anchor bolts: Connecting the home's mudsill to the concrete foundation. Older homes often have no bolts or inadequate bolt spacing.
Cost: $3,500–$8,000 for a standard cripple wall + anchor bolt retrofit.
Soft-Story Buildings
LA's mandatory soft-story retrofit ordinance requires apartment buildings with tuck-under parking or other soft-story configurations to be retrofitted. This is a code requirement, not optional.
Residential soft-story retrofit cost: $80,000–$200,000 for a typical multi-unit building.
Houses on Hillsides
Hillside construction has specific vulnerabilities — tall wood posts supporting structures over steep slopes can be damaged in lateral earthquake loading. Hillside homes in Studio City, Sherman Oaks, and hillside areas of the Valley may need:
- Post-to-beam connections upgraded with hardware
- Diagonal bracing added to tall post systems
- Foundation bolting at grade beams
Cost: $5,000–$25,000 depending on post configuration and height.
Concrete Block (URM) Buildings
Unreinforced masonry (brick or concrete block without rebar) is highly vulnerable to seismic damage. Most LA residential properties aren't URM, but some older commercial buildings and older apartment buildings are. URM seismic retrofit is complex and expensive — consult a structural engineer.
BRACE + BOLT Program
The City of LA's BRACE + BOLT program provides grants (up to $3,000 for most homeowners) for the standard residential wood-frame retrofit (cripple walls + anchor bolts). Application periods are announced on the LADBS website. This program makes the standard residential retrofit nearly no-cost for income-qualified homeowners.
Documentation and Insurance
Retain documentation of any seismic retrofit performed (permit, final inspection card). This documentation:
- Demonstrates compliance if future code adoption requires verification
- May qualify for premium discounts with earthquake insurance (CEA and private carriers)
- Provides disclosure information for future buyers
For seismic retrofit and structural renovation in the San Fernando Valley, contact us.
Related: Earthquake Retrofitting in Los Angeles · Foundation Repair in Los Angeles