Earthquakes risk in Maryland

Earthquake risk in Maryland: what homeowners should know

Maryland sits in the eastern United States, a region where earthquakes are much less frequent than along the West Coast — but where the shaking from any given quake can travel much farther. The bedrock beneath Maryland and its neighbors is old, cold and rigid, so seismic energy spreads across a wide area instead of dissipating quickly. That is why a single earthquake centered in central Virginia in 2011 was felt across a huge swath of the East, including nearly every corner of Maryland.

On the USGS National Seismic Hazard Maps, Maryland falls into the lowest hazard categories in the country, and the state carries a Level 1 out of 5 rating for earthquake risk on HomeRiskMap. That does not mean earthquakes never happen here — it means large, damaging earthquakes are rare, and most Maryland residents will go many decades without feeling a significant one.

Where Maryland's earthquake shaking comes from

Unlike California, Maryland has no mapped, active surface fault that scientists can point to as the source of future quakes. Earthquakes in the eastern U.S. generally occur on ancient, deeply buried faults that rarely break the surface, which makes them difficult to forecast. Most earthquakes actually centered in Maryland are small — typically far too weak to cause damage — and are recorded in the central Piedmont between Washington and Baltimore and in the state's north-central counties.

More often, the shaking Marylanders feel comes from earthquakes centered outside the state. The August 23, 2011 magnitude 5.8 earthquake near Mineral, Virginia, was felt statewide and produced minor damage such as cracked plaster and masonry in parts of the region. Distant earthquakes in the New Madrid seismic zone along the Mississippi River, or in eastern Canada, can occasionally be felt in Maryland as well.

Which areas and buildings are most exposed

• Older, unreinforced masonry buildings in historic neighborhoods of Baltimore, Annapolis, Frederick and Cumberland are the most vulnerable type of structure. Brick walls and chimneys without reinforcement crack or topple more easily when shaken.
• Areas with soft soils or fill — including parts of the Coastal Plain near the Chesapeake Bay and its tidal rivers — can amplify ground shaking compared with hard rock.
• Homes with tall, heavy chimneys or unreinforced crawlspace foundations face a higher chance of cracking even from moderate shaking.

Earthquakes are not seasonal in Maryland. They can occur at any time of year, in any weather, which is one reason preparedness matters more than forecasting.

How it affects homes

Because Maryland's earthquake hazard is low, most residents will never experience serious structural damage from a quake. When shaking is felt, the damage reported in this region is usually cosmetic or limited: cracks in drywall and plaster, hairline cracks in brick veneer or mortar joints, cracked or displaced chimneys, items knocked off shelves, broken windows, and doors or windows that stick because a house has shifted slightly on its foundation.

Less commonly, stronger shaking can cause foundation cracks, separated porches or steps, damaged masonry, and ruptured gas or water lines. Gas leaks and fires are a real concern after an earthquake, since a damaged connection can ignite even without a major collapse.

A few insurance points are worth knowing:

• Standard homeowners, renters and condo policies typically exclude earthquake damage. Earth movement is usually listed as an exclusion, so you generally need a separate earthquake endorsement or policy.
• Earthquake deductibles are often a percentage of your dwelling coverage rather than a flat dollar amount, so your out-of-pocket cost before coverage begins can be higher than your normal deductible.
• Masonry, chimneys and detached structures may be treated differently. Ask your agent exactly what is covered and what is excluded.
• Federal disaster assistance is not a substitute for insurance. FEMA assistance after a presidentially declared disaster is limited and is not designed to make a household whole.

Given Maryland's low risk, many homeowners reasonably decide to keep their standard policy and focus on mitigation instead. If you own an older brick home, or if your home represents most of your savings, it is worth pricing an endorsement — in low-hazard states the coverage is often inexpensive relative to the value of the home. Document your home and belongings with photos and receipts so a claim, if you ever need one, is easier to support.

How to prepare your home

Most earthquake injuries in the eastern U.S. come from falling objects and debris rather than collapsing buildings, so securing what is inside your home is the highest-value step. The Maryland Department of Emergency Management recommends basic preparedness steps that apply to any hazard.

1. Anchor tall furniture. Strap bookcases, dressers, wardrobes, china cabinets and televisions to wall studs with metal brackets or furniture straps. Avoid hanging heavy mirrors or framed art above beds and sofas.
2. Secure your water heater. Two metal straps around the tank, anchored to studs, help keep a water heater from tipping and rupturing gas or water connections. Consider a flexible gas connector and, if you have natural gas, an automatic seismic shutoff valve installed by a licensed plumber.
3. Use cabinet latches and non-slip mats. Childproof-style latches keep cabinet doors closed, while museum putty or shelf liner keeps glassware and breakables from sliding.
4. Inspect and brace chimneys and masonry. Have a mason check for loose bricks, deteriorated mortar and inadequate bracing. Unreinforced chimneys are one of the most common sources of damage in eastern earthquakes.
5. Look at your foundation. An older home that is not bolted to its foundation, or one with unreinforced cripple walls, can shift more during shaking. A licensed structural engineer or contractor can advise whether retrofitting is worthwhile.
6. Know how to shut off your gas. Keep a wrench near the meter, and only shut the gas off if you smell gas or see or hear a leak — a professional is usually needed to turn it back on.
7. Practice Drop, Cover and Hold On with everyone in your household. Drop to your hands and knees, cover your head and neck under a sturdy table, and hold on until the shaking stops.
8. Build an emergency kit with water, non-perishable food, medications, a flashlight, a battery or hand-crank radio, and copies of important documents. Keep a fire extinguisher handy and test your smoke alarms.

Frequently asked questions

Does Maryland actually have earthquakes?

Yes, but they are mostly small. Maryland sits in a low-hazard part of the country, and the quakes centered within the state are typically too weak to cause damage. Much of the notable shaking residents have felt came from earthquakes centered outside Maryland, including the magnitude 5.8 Virginia earthquake of August 23, 2011, which was felt statewide and caused minor damage such as cracked plaster and masonry.

Is earthquake insurance worth it in Maryland?

For most Maryland homeowners it is optional rather than essential, because the likelihood of damaging shaking in any given year is low. It is more often worth considering if you own an older unreinforced masonry home, have a large mortgage or a high replacement cost, or simply want protection against a rare but potentially expensive event. Compare the endorsement's premium against its percentage-based deductible, and confirm what is excluded.

What should I do during an earthquake in Maryland?

Follow the same guidance used anywhere: Drop, Cover and Hold On. If you are indoors, stay indoors, get under a sturdy table or desk and away from windows, mirrors and tall furniture. If you are outdoors, move away from buildings, streetlights and utility wires. If you are driving, pull over to a clear spot and stay in the vehicle. Once the shaking stops, check for injuries, look for gas leaks and structural damage, and avoid using open flames.

Official resources

• Maryland Department of Emergency Management — state preparedness guidance and emergency alerts.
• USGS Earthquake Hazards Program — hazard maps, recent earthquakes and fault information.
• Ready.gov — Earthquakes — step-by-step guidance for before, during and after an earthquake.
• FEMA Earthquake Safety — mitigation, risk management and recovery resources.