Why Hawaii Is One of America's Most Seismically Active States

Hawaii experiences more earthquakes than almost any other U.S. state. The reason is geology: the Hawaiian Islands formed — and continue to form — as the Pacific Plate moves slowly over a stationary hot spot deep in Earth's mantle. Magma forcing its way through the plate, combined with the immense weight of the islands pressing down on the ocean floor, generates constant seismic stress.

The Big Island sits directly over the hot spot and is the most active. The 2018 eruption of Kilauea was preceded and accompanied by a magnitude 6.9 earthquake — the largest in the state since 1975. Mauna Loa's flanks carry accumulated geological stress that periodically releases in significant quakes. A fault system called the South Flank of Kilauea moves about 6 to 10 centimeters per year, building strain that eventually releases suddenly.

Understanding this context matters because Hawaii's earthquake risk differs from mainland states. Shaking can happen on any island, aftershock sequences can last weeks, and coastal residents face the compounding hazard of tsunamis. Preparation is not alarmist — it is straightforwardly practical for anyone living in or visiting the islands.

Secure Your Home Before the Next Quake

The single most effective action you can take before an earthquake is reducing hazards inside your home. Most earthquake injuries come from falling objects and toppling furniture, not from the ground motion itself. Work through this checklist room by room:

• Anchor tall furniture to walls. Bookshelves, wardrobes, and refrigerators become dangerous projectiles during strong shaking. Use L-brackets or furniture anchor straps rated for at least 200 pounds. Most take under 30 minutes to install with a drill and wall anchors appropriate for concrete or drywall construction.
• Secure heavy items on high shelves. Move the heaviest books, equipment, and decorations to lower shelves. Use museum putty to anchor lamps, framed photos, and collectibles to surfaces.
• Strap your water heater to the wall. Hawaii building codes require this for new construction, but older homes often lack straps. A toppled water heater can rupture gas lines and cause fires — use a double-strap kit from any plumbing supply store.
• Know your gas shutoff location. Find the main gas shutoff valve and keep an adjustable wrench nearby. Only shut off gas if you smell a leak after a quake — resetting requires the gas company to come out.
• Identify safe spots in each room. Under a sturdy desk or table, against an interior wall away from windows, or next to a heavy sofa that will not tip. Standing in a doorframe is outdated advice — it offers no special protection in modern buildings.
• Secure standalone water storage tanks. If you use water catchment or storage tanks, strap them to structural elements so they cannot fall and rupture your supply.

Set aside 2 to 3 hours to go through your home with this list. Photograph each mitigation step for your insurance records. This is the highest return-on-time activity for earthquake preparedness.

Build a 72-Hour Emergency Kit Tailored to Hawaii

FEMA recommends a 72-hour emergency kit for all households, but Hawaii has specific needs. The islands are geographically isolated — resupply after a major event can take several days longer than on the mainland, and road closures from lava flows or landslides can cut off entire communities. Aim for a 7-day kit if storage space allows.

Water

Store one gallon per person per day for drinking and basic sanitation. For a family of four, that is 28 gallons for a 7-day supply. Use food-grade containers or sealed commercial water jugs. Rotate every six months if using tap-filled containers. Keep water purification tablets and a portable filter as backup for treating stream water.

Food

Pack shelf-stable foods your household will actually eat: canned fish, beans, and vegetables; rice and oats in sealed containers; peanut butter; crackers. Include a manual can opener — electric ones are useless without power. Target approximately 2,000 calories per person per day. Account for any dietary restrictions, infant formula, or pet food needs.

First Aid and Medications

• Adhesive bandages, gauze rolls, medical tape, antiseptic wipes
• Tweezers, scissors, disposable gloves
• Pain relievers such as ibuprofen and acetaminophen
• A 7-day supply of all prescription medications — request advance refills from your doctor before an emergency
• Copies of prescriptions and insurance cards in a waterproof bag

Communication and Documents

• Copies of IDs, passports, and insurance policies in a waterproof envelope
• Battery-powered or hand-crank NOAA weather radio — receives tsunami warnings even when cell service is down
• Fully charged portable power bank for phones, rated at least 20,000 mAh
• Written list of emergency contact numbers in case phones are dead or damaged

Tools and Hawaii-Specific Supplies

• Flashlights with extra batteries, at least one per person
• Multi-tool or folding knife
• Dust masks rated N95 or KN95 — volcanic ash and debris enter the air after major earthquakes near active volcanoes
• Emergency Mylar blankets, one per person
• Cash in small bills — ATMs frequently go offline after major disasters

Store the entire kit in a waterproof bin or bag near an exit. Review and restock it every January and July to catch expired food and medications.

During the Earthquake: Drop, Cover, and Hold On

When shaking starts, the correct response is the same in every location: Drop, Cover, and Hold On. Do not freeze in place, do not run outside, and do not stand in a doorframe.

1. DROP immediately to your hands and knees. This protects you from being knocked off your feet and puts you in position to move if necessary.
2. COVER your head and neck with your arms. If a sturdy table or desk is nearby, crawl under it and hold your head there. If no furniture shelter is available, get against an interior wall away from windows and cover your head with both arms.
3. HOLD ON to the table leg if you are sheltered beneath one. Maintain your position until all shaking has completely stopped. Earthquakes sometimes pause briefly and then resume — do not stand up until you are certain the motion has ended.

Hawaii-specific scenarios to prepare for:

• At the beach or coast: After shaking stops, move inland and uphill immediately without waiting for sirens. Local tsunamis can arrive within minutes of the earthquake.
• In a high-rise hotel: Drop and cover in place. Do not use elevators. After shaking stops, listen for instructions from hotel staff. Hawaii high-rises built after the 1970s meet modern seismic codes and are generally safer to shelter in than trying to exit during an event.
• While driving: Pull over away from overpasses, power lines, and building facades. Stay in the car with your seatbelt fastened until shaking stops completely.
• Outdoors away from the coast: Move away from buildings, trees, and power lines. Drop to the ground and cover your head with your hands.

Active shaking typically lasts between 10 and 60 seconds. The instinct to flee is strong — resist it. Most injuries from earthquakes happen when people move during the shaking itself.

After the Quake: What to Do in the First Hour

Aftershocks will follow. Most are smaller than the mainshock, but a major earthquake above magnitude 6.0 can produce aftershocks above magnitude 5.0 that cause additional structural damage. Expect intermittent shaking for hours to days. Work through these steps in order after the initial quake stops:

1. Check yourself and others for injuries. Prioritize life-threatening bleeding — apply direct pressure with any cloth available. Call 911 only for serious emergencies; after a major quake, phone lines become congested immediately.
2. Check for gas leaks. If you smell sulfur or a rotten-egg odor, open windows without touching light switches, leave the building, and call the gas company from outside. Do not use any open flames or electrical switches until the area is cleared.
3. Assess structural damage. Look for large cracks in load-bearing walls, doors that have jammed in their frames (a sign of structural distortion), or a foundation that has visibly shifted. If the building feels unsafe, evacuate to open ground away from all structures.
4. Evaluate tsunami risk if you are near the coast. Did the shaking last more than 20 seconds? Was it strong enough to make standing difficult? These are natural warning signs of a potentially tsunami-generating quake. Move uphill without waiting for an official alert.
5. Turn on your NOAA weather radio or check HI-EMA alerts. Get official guidance about whether evacuation orders are in effect for your area.
6. Stay off roads unless evacuating. Roads may be blocked by debris, and emergency vehicles require open lanes to reach those who need help.

Do not re-enter any damaged building until local authorities have inspected and posted it as safe. In Hawaii, inspectors use color-coded placards: green means safe to occupy, yellow means restricted entry only, and red means do not enter under any circumstances.

Tsunami Preparedness Specific to Hawaii

A locally generated earthquake tsunami is the most time-critical compounding hazard in Hawaii. Unlike distant tsunamis originating from Alaska or South America — which provide hours of warning — a major quake off the Big Island can produce destructive waves reaching Hilo Bay in under 10 minutes. This is not enough time to wait for official warnings.

Know your evacuation zone before you arrive:

• Hawaii County, Maui County, the City and County of Honolulu, and Kauai County all publish tsunami evacuation zone maps. Download the map for your island from the Hawaii Emergency Management Agency website before your trip or before the next storm season.
• Look for blue-and-white evacuation route signs posted at street level when you arrive somewhere new. These mark the walking routes to high ground.
• Your elevation target is at least 100 feet (30 meters) above sea level, or at least one mile inland from the shoreline. Higher and farther is always better.

The natural warning rule: If an earthquake is strong enough that standing is difficult, or if it lasts more than 20 seconds, and you are within one mile of the coast — move inland and uphill immediately. The siren system is primarily designed for distant tsunamis. For local events, your body's perception of the shaking is your most reliable early warning.

Waiting out the wave train: The first wave in a tsunami sequence is rarely the largest. Tsunamis arrive as a series of waves typically spaced 15 to 60 minutes apart. Stay on high ground for a minimum of four hours after the last wave, or until local authorities announce the all-clear on NOAA radio. Many deaths from historical Hawaii tsunamis occurred when people returned to the coast too early.

Hawaii Emergency Alert Systems and Key Resources

Staying informed before, during, and after an earthquake requires multiple overlapping alert systems. Set up all of the following before you need them:

• Wireless Emergency Alerts (WEA): Automatically delivered to your cell phone when you are physically in an affected area — no signup required. These alerts override Do Not Disturb on most U.S. phones. Verify this is enabled in your phone settings.
• HI-EMA Community Alert System: Register with the Hawaii Emergency Management Agency for location-specific warnings by email or SMS text message. Coverage includes earthquakes, tsunamis, and other island-specific hazards.
• NOAA Weather Radio: A battery-powered or hand-crank NOAA weather radio broadcasts continuous updates and tone-alert warnings even when cell towers are overloaded or offline. This is the most reliable backup channel after a major quake. The Midland ER310 and Eton FRX5 are widely available models.
• USGS Earthquake Notification Service: Sign up at earthquake.usgs.gov/ens for email notifications whenever a significant earthquake occurs near Hawaii. You can customize magnitude thresholds and geographic areas.
• Pacific Tsunami Warning Center: Based in Ewa Beach on Oahu, the PTWC issues all official Pacific tsunami bulletins. Their public website displays active advisories in real time and is the authoritative source for official threat levels.

Hawaii tests its outdoor warning sirens on the first business day of each month at 11:45 AM. If you hear the siren on any other day, treat it as a real emergency and move to high ground immediately — verify the situation from high ground, not from the beach.

Print a copy of your evacuation plan and emergency contact numbers and keep it with your emergency kit. Cell service and internet access are often disrupted for hours or days after a major earthquake, and a printed plan requires no battery or signal to use.