What Is the San Andreas Fault?

The San Andreas Fault is a 1,200-kilometer (800-mile) continental transform fault running through California, forming the tectonic boundary between the Pacific Plate and the North American Plate. These two massive plates grind past each other horizontally at roughly 5 centimeters per year—approximately the speed at which your fingernails grow—building enormous stress that releases in earthquakes.

The fault has three major segments with very different behaviors:

• Northern segment: Stretches from the San Francisco Bay Area to Cape Mendocino. This segment ruptured catastrophically in the 1906 San Francisco earthquake (estimated magnitude 7.9), killing over 3,000 people and destroying much of the city through quake damage and the fires that followed.
• Central segment (creeping section): Runs through central California near Parkfield and Hollister. The fault here moves gradually and continuously, slowly releasing stress without producing large destructive earthquakes.
• Southern segment: Runs from Cajon Pass through the Coachella Valley to the Salton Sea. This is the most seismically locked and dangerous section—it last ruptured in 1857 during the Fort Tejon earthquake (estimated magnitude 7.9) and has been accumulating stress for over 165 years.

USGS scenario modeling (the Great ShakeOut study) projects that a magnitude 7.8 rupture on the southern segment could cause up to 1,800 deaths, 50,000 injuries, and $200 billion in economic damage—affecting 22 million people across Southern California within the first two minutes of shaking.

Understanding the fault is the first step. The second—and far more actionable—step is preparing your home and family before that stress releases.

How to Secure Your Home Before an Earthquake

Most earthquake-related injuries come from falling objects and toppling furniture, not structural collapse. Securing your home is the single highest-impact action you can take, and most of it requires only basic hardware store materials and a few hours of work.

Strap water heaters and gas appliances

Use plumber's tape or dedicated appliance straps to bolt your water heater to two wall studs—one strap near the top third and one near the bottom third. Install flexible gas connectors on all gas appliances to prevent line ruptures when the structure shifts. Budget approximately $20-50 in hardware and 1-2 hours of work. This single step prevents the leading cause of post-earthquake fires: broken gas lines.

Anchor tall furniture to wall studs

Tall bookshelves, filing cabinets, china hutches, and refrigerators should each be secured to studs using L-brackets or furniture anti-tip straps. Most hardware stores stock furniture strapping kits for $5-15 per piece. Move heavy items to lower shelves and store all glassware in closed, latched cabinet doors—not on open shelves.

Retrofit your cripple wall if your home was built before 1980

A cripple wall is the short wood-framed wall between your home's concrete foundation and the first floor. In homes built before modern seismic codes, these walls lack the structural plywood sheathing needed to resist lateral earthquake forces, causing homes to slide off their foundations even in moderate events. A licensed contractor can add cripple wall bracing for roughly $3,000-8,000—a fraction of the cost of post-earthquake foundation repair.

Install a seismic gas shutoff valve

A seismic gas shutoff valve automatically closes your home's gas supply when it detects ground acceleration above approximately 0.3g. These valves cost $250-350 installed by a licensed plumber and can prevent catastrophic post-earthquake fires. Many California cities now require them upon home sale.

Inspect your chimney

Unreinforced masonry chimneys are among the most common sources of injury in moderate earthquakes—bricks falling through a roof can be fatal. Have a licensed mason inspect your chimney for cracks and deteriorating mortar before an event. If your chimney is unreinforced brick, consider removing the above-roofline portion or having it professionally reinforced with steel ties.

Building a 72-Hour Emergency Kit

After a major earthquake, FEMA and California OES recommend having enough supplies to be self-sufficient for at least 72 hours without outside help. In practice, infrastructure repairs after a large San Andreas rupture could take one to two weeks, so building toward a two-week supply is wise if you have the storage space.

Water (the most critical supply)

• Minimum 1 gallon per person per day—include pets in your count
• A 3-day supply for a family of four = 12 gallons minimum
• Use PETE (#1) plastic containers or commercially sealed water jugs rated for long-term storage
• Include water purification tablets (Aquatabs) or a gravity-filter pouch as backup in case stored supply is compromised
• Rotate stored water every 12 months even if sealed

Food

• Non-perishable staples: canned beans, canned tuna or sardines, peanut butter, crackers, granola bars, instant oatmeal, dried fruit
• A manual can opener is non-negotiable—electric models will be useless without power
• A portable camp stove with fuel canisters allows hot meals, which matter enormously for morale during extended displacement
• Rotate all stock every 6-12 months and check expiration dates when you rotate

First Aid Kit

• Adhesive bandages in assorted sizes, sterile gauze pads, and medical tape
• Antiseptic wipes and antibiotic ointment
• Ibuprofen and acetaminophen for pain and inflammation
• A 7-day emergency supply of any prescription medications family members take daily
• Nitrile gloves and a CPR face shield

Documents and Cash

• Waterproof pouch containing copies of: driver's licenses, passports, homeowner's or renter's insurance policy, property deed, vaccination records, and any vehicle titles
• $200-500 in small bills—ATMs and card readers will be offline for days after a major event
• A USB drive with encrypted digital copies of critical files, stored alongside a charged portable battery bank

Tools and Safety Gear

• Battery-powered or hand-crank NOAA weather radio for emergency broadcasts when cell networks are down
• Headlamps for every adult (hands-free lighting is essential when clearing debris or navigating at night)
• A loud whistle to signal for help if you are trapped in rubble
• Heavy work gloves and N95 dust masks for searching through earthquake debris
• An ABC-rated fire extinguisher if you do not already keep one accessible in your home
• Duct tape and heavy plastic sheeting for emergency shelter-in-place situations

What to Do During an Earthquake

When shaking begins you have only seconds to react. The correct response—endorsed by FEMA, the CDC, and structural engineers worldwide—is Drop, Cover, and Hold On. Every second spent deliberating is a second of exposure to falling objects.

Step 1: DROP to your hands and knees immediately

Getting low prevents you from being knocked off your feet and reduces your exposure to flying objects at standing height. Do not run for the door. The vast majority of earthquake injuries occur when people attempt to move to another location rather than sheltering in place.

Step 2: COVER your head and neck with your arms

If a sturdy table or desk is within arm's reach, crawl under it and hold on. If no table is available, press your back against an interior wall away from windows and use both arms to cover the back of your head and neck. Do not stand in a doorway. This is a persistent and dangerous myth—a modern doorway offers no special structural protection, and you are exposed to a swinging door and the open hallway on both sides.

Step 3: HOLD ON until the shaking completely stops

Grip your table or shelter with one hand. Be ready to move with it as the floor shifts. A major earthquake can shake for 30 seconds to over a minute—do not assume a brief lull means it is over. Stay down until all motion has fully ceased.

Special situations

• In bed at night: Stay in bed, roll face-down, and pull your pillow over your head. Running across a dark bedroom toward a doorway is far more dangerous than staying put.
• In a moving vehicle: Signal and pull over, away from overpasses, bridges, tall buildings, and power lines. Stay inside with your seatbelt on. After shaking stops, drive slowly and watch for road damage, downed wires, and bridge damage.
• Outdoors: Move away from buildings, streetlights, and overhead utility lines immediately. Crouch low in a clear open area. The greatest hazards outdoors are falling glass and facade fragments.
• In a crowded public space: Do not rush for the exits. Most injuries in theaters, malls, and stadiums during earthquakes result from panicked crowds falling on stairwells. Drop and shelter in place.

What to Do After the Shaking Stops

The 30 minutes immediately following an earthquake are critical for preventing the secondary hazards—fires, gas leaks, and structural collapses—that often cause more casualties than the shaking itself. Work through these checks calmly and in order.

Immediately after shaking stops

1. Check yourself for injuries before attempting to move. Then check anyone nearby. Do not move an injured person unless they are in immediate danger from a secondary hazard.
2. If you smell natural gas—a sulfur or rotten-egg odor—open windows and exit the building immediately. Call your gas utility from outside. Do not use any electrical switches, lighters, or phones inside.
3. Scan visually for fire hazards: sparking electrical outlets, overturned appliances, broken gas lines, spilled flammable liquids.
4. Put on sturdy closed-toe shoes before walking anywhere in your home. Broken glass on floors is the most common cause of immediate post-earthquake lacerations.

Building safety inspection

1. Check load-bearing walls for cracks wider than 1/4 inch or signs of structural shifting such as doors and windows that no longer fit their frames.
2. Inspect the chimney from outside before using any fireplace. A cracked chimney can collapse inward.
3. Open cabinet and pantry doors slowly—contents shift significantly during shaking and will fall when the door opens.
4. If you observe major structural damage (sagging roof line, shifted foundation, large wall cracks), exit the building and do not re-enter until a licensed structural engineer has cleared it.

Managing utilities

• Water: If pipes appear broken or water looks discolored, shut off the main water valve and rely on your stored supply.
• Electricity: Do not operate any electrical switch or outlet if you suspect a gas leak. A single spark can ignite accumulated gas.
• Gas: Only shut off your gas at the meter if you actively detect a leak. Once shut off, only the gas company can restore service—which can take days to weeks after a large earthquake.

Prepare for aftershocks

Aftershocks can follow the main event for days, weeks, or months, and some can be damaging on their own. Apply Drop, Cover, Hold On each time you feel shaking. Aftershocks are especially dangerous when structural damage has already weakened a building—if yours has damage, get out and stay out.

Creating a Family Emergency Communication Plan

Phone networks become severely congested—or fail entirely—immediately after a major earthquake. Call volume spikes by hundreds of times normal in the first hour. A pre-established plan is the only reliable way to reconnect with family members quickly when infrastructure is overwhelmed.

Step 1: Designate one out-of-state contact as your hub

Choose a friend or relative who lives outside California to serve as the central communication point for your entire family. During a regional disaster, it is consistently easier to reach out-of-state numbers than local ones, because those calls route through less-congested network segments. Every family member—including children old enough to use a phone—should have this person's number memorized or written on a card kept in their wallet or backpack.

Step 2: Establish two physical meeting points

• Meeting Point A (near your home): A specific, unmistakable spot in your immediate neighborhood—a particular neighbor's driveway, a specific street corner, or the mailbox cluster at the end of your street. Use this location if you need to evacuate your house but your neighborhood is accessible.
• Meeting Point B (farther away): A recognizable landmark in a different neighborhood—a library, a school, a place of worship, or a relative's home. Use this location if your immediate area is blocked, flooded, or on fire.

Walk each route with every family member, including young children, before a disaster strikes.

Step 3: Text instead of calling

SMS text messages use far less network bandwidth than voice calls and can queue on the network infrastructure until delivery is possible, even when voice calls cannot connect. Immediately after an earthquake, send texts rather than placing calls. Keep messages short and include your location and status.

Step 4: Register for emergency alerts

• Wireless Emergency Alerts (WEA) are pushed automatically to all cell phones in an affected geographic area—no signup is needed
• Register with your county's emergency notification system (AlertSCC, AlertSF, and similar services vary by county—search your county name plus emergency alerts)
• Download the FEMA app, which provides location-specific disaster alerts, shelter locations, and recovery resources
• Know your local emergency broadcast station, typically an AM station, which operates on backup power during grid outages

Step 5: Plan for children at school

Most California school districts use a formal reunification protocol requiring parents to sign students out in person with valid photo ID. Identify a backup authorized adult—a grandparent, trusted neighbor, or close friend—who can collect your children from school if you cannot reach the campus yourself.

Understanding Earthquake Insurance in California

One of the most financially damaging oversights among California homeowners is assuming their standard homeowners insurance covers earthquake damage. It does not. Earthquake damage requires a separate, standalone policy—and given the state's seismic exposure, this is a coverage gap worth understanding clearly.

The California Earthquake Authority (CEA)

The CEA is the largest provider of residential earthquake insurance in California, offering policies through participating insurance companies. A standard CEA policy can cover:

• Dwelling repair: Structural damage to your home up to your coverage limit
• Personal property: Furniture, electronics, appliances, and clothing damaged in the event
• Loss of use: Temporary housing costs if your home is uninhabitable during repairs
• Emergency repairs: Immediate steps taken to prevent further damage after the event

What earthquake insurance costs

Annual premiums vary significantly based on your home's age, construction type, proximity to active faults, and your chosen deductible. Rough annual ranges:

• New wood-frame home in a lower-risk zone: $800-1,400 per year
• Older stucco or concrete home near an active fault segment: $2,000-4,500+ per year
• Deductibles are typically 5-25% of your total coverage amount—not a flat dollar figure. On a $500,000 home with a 15% deductible, you absorb the first $75,000 of structural damage before insurance pays.

How to decide whether it is worth it

Ask yourself a direct question: if a magnitude 6.5 earthquake caused $100,000 in structural damage to your home tomorrow, could you absorb that cost without insurance coverage? If the answer is no, an earthquake policy is very likely worth the annual premium.

Older homes with unreinforced masonry, soft-story apartment construction, or homes on hillsides or filled land carry substantially higher earthquake risk and typically lose value more dramatically after a seismic event. For these properties, coverage is especially advisable.

To compare current quotes, visit the CEA's website directly or contact your current homeowners insurer and ask whether they participate in the CEA program. Seismic retrofits on qualifying homes can lower your premium by 10-25%.