Earthquakes

Although New York City does not sit on a major fault system that has been recently active, like the San Andreas Fault in California, earthquakes are possible here as evidenced by the 1884 earthquake and the more recent 2024 earthquake in New Jersey. 

The likelihood that a strong earthquake will occur is moderate, but the risk is heightened by New York City’s population density, the scale of its built environment, the interdependencies of its critical infrastructure systems, the age of its infrastructure, and the high proportion of buildings that were built before seismic design provisions were adopted in City building codes in 1995. 

What Is the Hazard?

An earthquake is caused by sudden slip on a fault that releases energy in seismic waves. As rocks and the Earth’s plates are strained by these tremendous geological processes from plate tectonics, energy builds up under the Earth’s surface. Eventually, accumulated strain deep underground becomes so great that it is abruptly released in an earthquake, which generates seismic waves that cause shaking. ¹U.S. Geological Survey, “What Is An Earthquake and What Causes Them to Happen?,” U.S. Geological Survey.

From the earthquake source, or “hypocenter” deep underground, the waves radiate outward and cause shaking at the Earth’s surface. An earthquake’s epicenter is the point on the earth’s surface that lies directly above the focus. Seismologists and engineers often measure the shaking that occurs as “ground acceleration.” 

The intensity of ground shaking depends on several factors, including the amount of released energy, the depth of the earthquake beneath the Earth’s surface, the distance from the fault, and the type of underlying soil or bedrock. 

How intensely a built structure responds to shaking during an earthquake depends on the building’s height, weight, and design, and its coupling to the ground. For example, a building on a concrete pad will have a different response to an earthquake than a building with a deep foundation. 

An earthquake has the potential to damage and destroy buildings and a city’s infrastructure and take lives. Under certain conditions, earthquakes can trigger landslides and cause soil liquefaction. The latter occurs when shaking and ground vibration during an earthquake cause unconsolidated, water-saturated soils to soften and turn fluid (i.e., like soft mud). Ground shaking, landslides, and liquefaction together can damage or destroy buildings, disrupt utilities, trigger fires, and endanger public safety. 

Aftershocks are part of the earthquake’s sequence that follows the largest, initial earthquake shock. Aftershocks are typically smaller and therefore less intense than the main shock, and may occur for weeks, months, or years after the initial earthquake event. 

Severity

Earthquake size is classified according to a magnitude scale that can be related to the energy released at the earthquake’s source. Seismographs and other scientific tools are used to measure and record data to understand the severity of each tremor in the Earth and the severity of each earthquake. In the past, earthquake tremors were ranked according to the Richter scale, but in the 1970s, the scientific community began to use the more accurate Moment Magnitude scale. The Moment Magnitude scale measures the size of an earthquake at its source in relation to the size of the fault and the degree to which the fault is displaced. It is a logarithmic scale — each point that an earthquake’s magnitude increases on the scale represents an energy release that is 32 times larger than the point that precedes it. ²U.S. Geological Survey, “Earthquake Magnitude, Energy Release, and Shaking Intensity,” U.S. Geological Survey.

Moment Magnitude Scale

The 2011 Virginia earthquake, which rattled the ground as far away as New York City, was a magnitude 5.8. By comparison, the 2011 earthquake that damaged the eastern coast of Japan was a magnitude 9.0 and considered catastrophic. The largest earthquake that has been recorded by instruments was magnitude 9.5 in Chile in 1960. The Modified Mercalli Intensity (MMI) scale is a measurement based upon what has been observed in seismic shaking during earthquakes. The MMI reflects twelve categories of intensity based on people’s reactions, their observations, and building damage during seismic events. ³U.S. Geological Survey, “Earthquake Hazards Program,” U.S. Geological Survey.

The Modified Mercalli Intensity Scale

On August 10, 1884, New York City experienced its most severe earthquake, which was estimated to have a magnitude of 5.2 on the Richter scale. ⁴Bob Groves, “N.J. Is Not Immune to Quakes,” The Record, Bergen County, March 2, 2001. On the MMI scale, the reported maximum intensities of the 1884 earthquake would correlate to Levels VI to VII. Experts also use quantitative methods to describe earthquake severity, such as Peak Ground Acceleration (PGA). PGA is an expression of the ground’s maximum acceleration as it shakes and moves during an earthquake and is a measure of its changing velocity as a function of time. Acceleration in the horizontal direction (as opposed to vertical direction) is an important way to measure and discuss the intensity of an earthquake, because many seismic building codes incorporate it into guidelines for building construction. Building codes stipulate, for example, the amount of horizontal inertial force (or mass times the acceleration) that buildings should be able to withstand during an earthquake without life-threatening damage. PGA is expressed as a percentage of the force of the Earth’s gravity (%g). A very strong earthquake, such as 1994’s magnitude 6.7 earthquake near Los Angeles, can produce PGAs of over 100 %g in the horizontal direction, which is greater than acceleration due to gravity. ⁵City of Los Angeles, “Remembering the Northridge Earthquake,” City of Los Angeles, January 16, 2020.

PGA continues to be an important measurement of ground shaking. However, Spectral Acceleration (SA) is the ground-motion measurement unit commonly used today in modern seismic building codes. Compared to PGA, SA is considered to be a better indicator of damage to specific building types and heights. SA reflects how buildings of particular masses, heights, and structural stiffness (and related natural response period) react to being shaken by an earthquake. 

How to Model a Building’s Spectral Acceleration (SA)

In a simplified manner, a building is represented by an inverted pendulum of a certain mass on a massless vertical rod that replicates the building’s natural period of vibration and the mechanical damping. A very approximate rule for the natural spectral period Tb (seconds) of a building as a function of the number of stories (n) in the building is as follows: Tb (seconds) = 0.1n. 

For example, a two-story building tends to have a natural period of about 0.2 seconds (frequency of 5 hertz), whereas a 10-story building tends to have a natural period near Tb=1 second (frequency of 1 hertz). The latter means that it would take about 1 second to sway back and forth. 

Probability

PGA is also used to understand more about the types of earthquake hazards that are likely. The U.S. Geological Survey (USGS), which studies seismic conditions nationally, produces maps that indicate where future earthquakes are most likely to occur, how frequently they might occur, and how hard the ground may shake (PGA).⁶Mark D. Petersen, Morgan P. Moschetti, Peter M. Powers, Charles S. Mueller, Kathleen M. Haller, Arthur D. Frankel, Yuehua Zeng, et al., Documentation for the 2014 Update of the United States National Seismic Hazard Maps (U.S. Geological Survey, August 5, 2014).

The National Seismic Hazard Model assesses ground shaking hazards arising from potentially damaging earthquakes within the United States and its territories. This model generates a map that indicates the probability of experiencing damaging seismic activity across the nation over the next century. The latest USGS maps, released in 2023, show that there is a 5 to 25 percent chance of a slight or damaging earthquake occurring in the New York City area over a 100-year period. 

The National Seismic Hazard Model Map, 2023

Location

Strong earthquakes in New York City have not occurred in historic times, but moderate-magnitude earthquakes are possible and have occurred (as in 1884). Even if an earthquake’s epicenter is far from New York City, the geology underlying the northeast United States can cause some ground shaking to be felt in the city. ⁷S. Nikolaou, “Local Geology of New York City and Its Effect on Seismic Ground Motions,” proceedings from the Fifth International Conference on Case Histories in Geotechnical Engineering, New York, NY, April 13–17, 2004.

When an earthquake occurs, the older, harder bedrock of the Northeast transmits ground motions that can travel long distances before they subside. For example, tremors from the 2011 earthquake in east-central Virginia and the 2013 earthquake along Canada’s Ottawa River were felt by many people in the eastern United States, including in New York City. The 2011 Virginia earthquake caused extensive damage 87 miles away in Washington, DC. 

If an earthquake occurs beneath New York City, the unique geologic characteristics of the metropolitan area could result in significant effects due to soil amplification. The two main factors contributing to soil amplification here are the sharp contrast between softer soils and very hard bedrock, and the bedrock motions, which could be relatively short and shake with high frequency. 

High-frequency shaking is efficiently transmitted through the bedrock of the eastern United States and typically affects short, two- to five-story masonry buildings. If a shallow layer of soft soil (less than 100 feet thick) sits atop hard bedrock, shaking is amplified but only for a relatively short period of time. By contrast, a high-rise building atop deep soil deposits will shake longer and shake more slowly during an earthquake. 

Subsurface conditions in New York City, which vary widely across the five boroughs, can affect the degree to which an earthquake’s ground motion is amplified. As shown on the map titled Soil Types in New York City, geologic conditions range from solid bedrock at ground surface (green) to artificial fill (purple). 

Soil Types in New York City

For centuries, large areas of New York City have been filled to cover soft sediments and marshes in order to create new space for building development. ⁸Michael Kimmelman, “When Manhattan Was Mannahatta: A Stroll through the Centuries,” New York Times, May 13, 2020. For example, Manhattan’s present-day Chinatown is on land created by filling in a large pond; the World’s Fair Park site in Flushing, Queens, was built on an ash dump; and JFK Airport on Brooklyn’s south shore was built atop a hydraulic sand fill. These areas are similar to the Marina district in San Francisco, which suffered extensive damage in the 1989 Loma Prieta earthquake because of amplification of seismic waves by the soft soils and by the soft soils liquefying (i.e. becoming like soft mud). 

Historic map of the Chinatown area of New York City

Historic Occurrences

Between 1700 and 1986, over 400 earthquakes with a magnitude of 2.0 and above have been recorded in New York State. 

Between 1973 and 2012, New York State had only two damaging earthquakes with a magnitude of 5.0 and above. Historically, larger earthquakes have a longer “return period” in New York City. That is, they happen much less frequently than smaller earthquakes. ⁹Jagtar S. Khinda, “New York City’s New Seismic Design Criteria Guidelines for the New Millennium and an Update on the Seismic Retrofit for New York City Bridges,” proceedings from International Bridge Conference, Pittsburgh, PA, June 14–16, 1999.

On August 10, 1884, one of the region’s strongest earthquakes happened near New York City somewhere between Brooklyn and Sandy Hook, New Jersey. Based on contemporary reports of its damage, scientists today estimate it to have been a magnitude 5.2 earthquake. Although considered moderate by today’s magnitude scales, the shaking from this earthquake event was felt from Virginia to Maine, damaging chimneys and brick buildings in New Jersey and New York City. Considering the amount of building and development along the Hudson and in New York City since 1884, if the same magnitude earthquake occurred today, the amount of damage to people and property would be far greater. 

The historical earthquakes map shows the distribution of earthquake epicenters throughout the Tri-state area from 1737 to 2014 that were near New York City. Note that this map shows only approximate locations of epicenters for pre-1973 events; also, not every pre-1973 earthquake event is included on the map. ¹⁰U.S. Geological Survey, “Historic World Earthquakes,” U.S. Geological Survey.

NYC Historical Earthquakes

Source: NYCEM GIS

What Is the Risk?

Although the seismic hazard in New York City is moderate, because of the potential occurrence of a unique set of factors, summarized by the high seismic risk equation, the risk to the area could be high due to the high cost of dealing with the repercussions of any earthquake damage in a congested city environment. 

High Seismic Risk Equation

High Seismic Risk = Moderate Seismic Hazard x High Density & Monetary Value x Lack of Seismic Design (Before 1995)

With approximately 1 million buildings, New York City’s risk is very high, largely due to the lack of seismic codes in older buildings, the dense built environment, and the highly interconnected infrastructure. 

Most buildings in New York City were built before 1995, when more stringent seismic provisions in the Building Code were adopted; so, many of the most common building types here, such as unreinforced masonry buildings, are particularly vulnerable to seismic events. 

New York City’s newest commercial and residential buildings are built to modern seismic standards, which minimizes physical risk. Yet, the economic risk remains — real estate and new development sprouting across the boroughs is so valuable that the costs associated with repairing damage from an earthquake are extremely high. 

Any event that interrupts the flow of business, transportation, tourism, or finance in New York City, known as a “business interruption,” poses the risk of a negative economic impact on domestic and international trading partners. 

Social Environment

Unlike most other natural hazards, earthquakes occur with no warning — a situation that places the local population at immediate risk. Since New Yorkers experience earthquakes less frequently than other natural hazard events, people might be at higher risk, because they are less likely to be prepared to respond to this type of emergency. 

Earthquakes present a significant risk to public safety and health. A large-magnitude earthquake may cause significant injuries and casualties, disrupt emergency and medical services, and endanger individuals who depend on these services. Long-term health risks associated with earthquakes include post-traumatic stress disorder and a range of mental health problems such as depression and anxiety. 

A moderate (magnitude 5.5 to 6) earthquake, which is possible in or near New York City, could cause significant injuries and casualties. Mortality and injury typically peak within the first 72 hours following an earthquake. In a study of 1,100 fatal earthquakes around the globe, 75 percent of fatalities were caused by collapsing buildings. 

According to the Federal Emergency Management Agency (FEMA), nonstructural failures account for the vast majority of earthquake damage, causing serious injuries or fatalities and making buildings nonfunctional. Nonstructural components (not part of a building’s structural system) that cause risk include the following: 

• Architectural elements include cladding, windows, glass, and plaster ceilings, as well as exterior decorative features such as pediments, porticos, and statues. 
• Mechanical, electrical, and plumbing (MEP) components. 
• Furniture, fixtures & equipment (FF&E) and contents, such as heavy picture frames, mirrors over beds, hanging plants, and heavy furniture (bookcases, filing cabinets, and china cabinets).¹¹FEMA, Reducing the Risks of Nonstructural Earthquake Damage — A Practical Guide, FEMA, December 2012.

During an earthquake, these components may slide, swing, overturn or fall if they are not tightly affixed to the structure of the building. Theaters, libraries, and other large public areas often have plaster ceilings that are highly vulnerable to collapse when an earthquake shakes the building. Nonstructural failures can cause fatalities, injuries, and property loss — and also block exit routes during emergencies. 

In California, and in other seismically active regions of the country, many homeowners understand earthquake risk and take precautions, such as securing shelving to walls, anchoring valuable items, anchoring water heaters, and embarking upon additional mitigation efforts. In eastern U.S. cities, residents rarely take these precautions because they experience so few earthquakes and assume the risk is low. 

Buildings (six stories and taller) that have rooftop water towers are another risk in New York City. If an earthquake hits, water tanks can be toppled, disrupting water service to residents and potentially injuring pedestrians. 

Destruction of roads, bridges, and tunnels as the ground shakes during an earthquake could trigger widespread injuries and fatalities. The disruption of and damage to infrastructure and other critical systems often has a cascading set of impacts. Ground shaking during earthquakes could cause damage that generates fires, putting residents at significant risk. The disruption of transportation networks puts anyone who depends on them at risk, and also hinders delivery of emergency and medical services. Furthermore, an earthquake may disrupt essential infrastructure like wastewater systems, which can lead to a shortage of water for firefighting and increase the risk of cascading impacts. In an earthquake’s aftermath, health risks increase due to the potential for polluted water and diseases spreading throughout the community. 

The time at which an earthquake occurs also influences its impacts. Historically, if an earthquake occurs on a weekday between 9 a.m. and 5 p.m., mortality rates rise, because people are more likely to be working in a large building and children are likely to be at school. If an earthquake occurs during the night, people are likely to be at home inside with their family members. 

Damage to buildings after a moderate earthquake could force thousands of New Yorkers into interim housing or require permanent relocation for many people. This poses a challenge regarding where to locate interim housing because the city has limited housing options, and the surrounding region may be affected as well. 

An earthquake can put New York City’s economy at risk, displacing and disrupting businesses and utilities, and impairing people’s ability to work and generate income. Property owners are at risk of economic loss due to the need for expensive repairs and the loss of rental income. Any downtime in New York City’s operation, as a major global financial center, potentially affects the entire world’s economy. 

If important national monuments, landmarks, symbols of cultural heritage and arts institutions housing artifacts of great significance are damaged during an earthquake, the psychological and cultural impact from damage to these icons would be felt across the entire nation and perhaps internationally. 

Built Environment

Although earthquakes in New York City have a moderate probability of occurrence, any potential strong shaking here could prove to be catastrophic due to impacts of damage and interruption of services in the unique urban built environment with densely spaced and aged buildings and infrastructure with complex interdependencies and layers of lifeline services.  

A useful analogue for understanding how earthquakes might affect the built environment in NYC is Christchurch, New Zealand, which experienced a sequence of earthquakes in 2010-2011. Christchurch is much less dense than NYC, with a built form closer to a mid-sized U.S. city and most buildings between one and six stories. The University of Buffalo’s Multidisciplinary Center for Earthquake Engineering Research (MCEER) has reinforced the Christchurch-NYC connection, because its building typologies, especially its extensive stock of unreinforced masonry (URM) commercial blocks and mixed-use structures, closely resemble older masonry buildings found throughout the Northeast. UB researchers have used Christchurch ground-motion records and damage data to study the vulnerability of URM buildings typical of older Northeastern cities. ¹²Oskin, B. (2013, February 25). NYC brownstones flattened in earthquake shake test. NBC News. https://www.nbcnews.com Their shake-table tests, including a widely cited experiment on a full-scale NYC-style brownstone wall-demonstrated that Christchurch-level shaking can cause catastrophe out-of-plane failure in URM walls, validating concerns about NYC’s older masonry housing stock. This body of research is one reason Christchurch is routinely used as a real-world proxy for understanding how a moderate but close-in earthquake could affect NYC. 

Buildings

New York City’s built environment consists of a unique concentration of commercial and residential high-rise skyscrapers and low-rise buildings that are largely made of unreinforced brick. Each building type has a very different risk profile according to its height, material, location, and foundation. 

High-Rise and Low-Rise Buildings

The structural systems of New York City’s high-rise buildings are less vulnerable to earthquake damage than low-rise buildings. Large earthquakes with long-period waves tend to damage tall buildings; however, these categories of earthquake events are less likely to occur in New York City. Large-magnitude earthquakes that occur farther away from New York City, such as in Canada or the Midwest, can create low-frequency (slow-moving) shaking in the city that can affect tall buildings. High Rise buildings also tend to have deeper foundations that root below shallow deposits. Their foundations are more likely to be on hard bedrock or firmer soils at depth, whereas low-rise buildings are often built atop shallow deposits. (https://www.exactusengineering.com/resources/shallow-vs-deep-foundations)  

Buildings built according to the New York City Department of Buildings (DOB) 1995 building code and successive seismic regulations such as the 2008, 2014, and 2022 New York City Building Codes — which include a chapter for structural requirements — are expected to be capable of mitigating the impacts of an earthquake. The regulations require buildings to be designed, at minimum, to preserve human life if a major earthquake hits and to preserve general occupancy conditions if less severe earthquakes shake the building. 

Unreinforced Masonry and Wood Buildings

Structures in New York must be designed for earthquake loading since 1995, when the first seismic provisions became in effects. Older buildings not designed for earthquake loads are inherently vulnerable should a large earthquake occur. Unreinforced masonry (brick) buildings are most at risk because masonry is unable to absorb tensile forces during an earthquake. Instead of bending or flexing, walls, facades, and interior structures break or crumble. During a strong earthquake, the structural support system of an unreinforced masonry building has an increased risk of collapse. The typical modes of failure are:  

• Failure of the roof-to-wall connection with a resulting collapse. 
• Out-of-plane (when forces are exerted perpendicular to the surface) failure of unreinforced masonry walls. 
• In-plane failure of unreinforced masonry walls, when cracks develop in the plane of the wall.¹³FEMA, Unreinforced Masonry Buildings and Earthquakes: Developing Successful Risk Reduction Programs, FEMA P-774, October 2009.

As of 2019 in New York City, Brooklyn has the largest number of masonry buildings (165,661), followed by Queens (108,694), the Bronx (49,734), Manhattan (29,766), and Staten Island (7,041). 

Among these are over 100,000 multifamily, unreinforced brick buildings in New York City as a whole, most built between the mid-1800s and 1930s.¹⁴Dan P. E. Eschenasy, “Cases of Failure of Unreinforced Brick Walls Due to Out-of-Plane Loads,” Structural Forensics Magazine, May 2011. All are between three and seven stories high. 

Many New York City neighborhoods consist of rows of attached unreinforced masonry buildings. The buildings rely on one another for stability, so any building that sits at the end of a block or next to a vacant lot is particularly vulnerable during an earthquake event. Masonry loft buildings, which are common in New York City, are vulnerable because they lack interior walls and have higher-than-average ceilings. 

Because wood is a lighter and more flexible building material, wood frame buildings respond better to earthquakes. In New York City’s fire districts, buildings constructed with wood frames are required to have a masonry veneer (or larger distances between buildings). Most one- to two-family houses in New York City are wood frame construction. For these homes, an earthquake could damage the masonry facade, but the structure could still stand. However, for three- to four-story buildings with load-bearing masonry, the building’s stability could be compromised during an earthquake. 

Even if an earthquake caused little damage aboveground, damage to a building’s foundation could render it uninhabitable or unusable. A large portion of New York City’s waterfront originated as wetland or wasteland that was filled in, reclaimed, and built up over time. During colonial times, this land was typically created by using fill with poor structural properties. A few decades ago, more controlled fill and construction procedures were applied. 

New York City has adopted guidelines to protect structures from flooding and has increased its resiliency by recommending that coastal buildings be elevated so that a soft story base permits floodwaters to pass through — for example, supporting the first floor on piers. However, during an earthquake, this combination of a soft story base and poor subsurface conditions could shift most of the building’s load to the foundation, concentrating most of the damage in the bottom story. 

Assessing Potential Earthquake Impacts on New York City Buildings 

NYCEM uses FEMA’s HAZUS-MH software to project losses and to assess structural vulnerability of New York City buildings should an earthquake occur. The five overall damage state categories for the HAZUS-MH earthquake module are None, Slight, Moderate, Extensive, and Complete. The graphic explains the four structural damage states (Slight to Complete) for a single building class (in this case, Type W1-wood, light frame). 

HAZUS-MH Earthquake Damage States 

Source: HAZUS-MH Earthquake User Manual, Figure 9.17 

For the 2026 Hazard Mitigation Plan update, NYCEM transitioned from a single-scenario deterministic earthquake model to a probabilistic analysis. While the previous plan relied on a single magnitude 5.2 event with just one epicenter, the probabilistic approach evaluates the statistical likelihood of ground shaking from all potential seismic sources. 

This shift from deterministic to probabilistic modeling enables NYCEM to move from response-based planning to resilience-based planning. A deterministic model is a tactical, scenario-based tool. It relies on fixed information, like epicenter location and magnitude, to model potential impacts. For example, it can help answer very specific questions like, “What happens to NYC’s essential facilities if a magnitude 6.1 earthquake occurred just west of Manhattan?” Conversely, a probabilistic model provides a comprehensive risk profile. It does not rely on fixed variables, but rather looks at thousands of potential events over long return periods. It incorporates uncertainties in earthquake location, size, and frequency to offer a more comprehensive assessment. 

By modeling various return periods, the City can better assess risk across different timeframes and intensities: 

• Low Intensity: 100-year and 250-year return periods. 
• Moderate Intensity: 500-year, 750-year, and 1,000-year return periods. 
• Extreme Intensity: 1,500-year, 2,000-year, and 2,500-year return periods. 

The return periods used in this probabilistic analysis function on a spectrum of frequency versus severity. Low-intensity return periods, such as the 100-year and 250-year events, represent a high probability of occurring within a typical planning horizon but generally result in low impact regarding structural damage and economic loss. As the return period increases toward the 1,500-year to 2,500-year range, the events become statistically rare, representing a low probability of occurrence. However, these extreme-intensity scenarios involve significantly more powerful ground shaking, leading to high-impact outcomes. 

These model runs represent an as-is view of the City’s impacts from various return periods. To quantify the effectiveness of potential resilience strategies, NYCEM developed earthquake mitigation models that systematically adjust various mitigation strategies within the model framework, such as increasing the Earthquake Design Level for older structures and applying structural retrofits to Unreinforced Masonry to selected buildings and essential facilities. 

These essential facilities include: 

• Airports 
• Bus Facilities 
• Care Facilities 
• Communication Facilities 
• Electric Power Facilities 
• Emergency Operations Centers 
• Ferries 
• Fire Stations 
• Oil Facilities 
• Police Stations 
• Ports 
• Rail Facilities 
• Schools 
• Waste Water Facilities 

By comparing the outputs of these mitigated scenarios against the baseline model, NYCEM can calculate various damages avoided by hardening essential facilities and produce improved mitigation strategies. 

NYCEM ran probabilistic earthquake models to understand the impacts of various return periods, ranging from a low-intensity 100-year event all the way to an extreme-intensity 2,500-year event. 

The baseline models show that NYC’s risk is primarily driven by density, high property value, and infrastructure age. Other factors, like soil liquefaction, can also increase risk and impacts. Even at moderate return periods, the high concentration of assets leads to significant economic and social exposure. 

To understand how various mitigation measures would reduce the impacts to essential facilities, NYCEM applied two mitigation measures for this analysis.  

• Seismic Design Level Upgrades: This strategy adjusts the Earthquake Design Level for older, pre-code critical facility buildings constructed before 1996 to modern standards. This cutoff is based on the adoption of Local Law 17, which represented the first time the New York City Building Code was updated to include specific seismic provisions to protect structures against earthquake forces. Prior to this mandate, most buildings in the City were constructed without formal requirements for seismic resistance.  
• Targeted Unreinforced Masonry (URM) Mitigation: Because low-rise and mid-rise URM buildings drive disproportionately high economic and social impacts due to their brittle nature, this scenario models the impact of targeted structural retrofits for pre-1950 and high-occupancy masonry structures. Pre-1950, most URM buildings used flexible timber, which are more likely have a pancake collapse during an earthquake. Post-1950, there was a shift from wood floors to concrete/steel, and a standardization of mortar and brick strength. This reduces the probability of a total collapse, even if the masonry is still unreinforced.  

By modeling these mitigation measures, NYCEM can calculate the total damages avoided to essential facilities. 

For the full report, you can download here. 

Infrastructure

If an earthquake occurs in New York City, there is a risk that its impact will compromise infrastructure such as transportation, utility, electricity, and water/waste water systems. As part of other capital improvements being made here, some of New York City’s existing lifeline assets such as bridges have been partially retrofitted to improve their seismic performance.  

However, the seismic vulnerability of the city’s complex network of interlinked infrastructure remains poorly understood and exists as an area of high concern, even as parts of the infrastructure undergo change, upgrade, and renewal. Some of New York City’s critical infrastructure systems are vulnerable because they have aged and have maintenance and life cycle challenges.  

During an earthquake event, soil below the ground water could liquefy with its strength reduced or lost. This could result in large-scale ground failure that damages pavements and building foundations and massively disrupts underground utilities. Areas with artificial fill are vulnerable to liquefaction and include the shorelines of Long Island (and around the JFK Airport), the World’s Fair area in Flushing, Queens, the tip (Battery Park) and Chinatown in Manhattan. A strong seismic event in close proximity to the city could cause structures built atop liquefied soils to sink and settle. Damage to underground infrastructure usually occurs wherever pipes and other utility transmission lines are unable to withstand soil differential movements. Damage to these critical links could trigger secondary impacts that pose even greater risk to the public — water contamination, fires, and sudden, powerful explosions.  

Natural Environment

Earthquakes can severely damage the natural environment, destroy trees and disrupt the landscape. 

Competition for space can push development on formerly marginal lands. With increased urbanization, an earthquake (combined with effects of extreme weather) would also affect the more densely populated areas. What would once be a small, localized event will become now a catastrophic event  

Earthquakes also pose risks that could cause severe harm to the natural environment — fires caused by gas pipe explosions, flooding and other disruption caused by broken water pipes, accidental releases of hazardous waste and sewage, and devastating landslides.  

With the increased occurrence of flash floods, hurricanes, extreme rainfalls, an earthquake could be combined with these climate induced hazards which could increase the risk exponentially.  

Future Environment

As New York City’s substantial stock of seismically vulnerable (pre-seismic code) buildings is gradually replaced with new structures conforming to more robust seismic building code specifications, the percentage of vulnerable buildings will gradually decline. However, this would take a very long time. The dollar value of New York City’s vulnerability would be expected to decline as well; however, if the value and volume of New York City’s built assets increase over time, the economic risk from seismic exposure could still increase. 

Aging components of New York City’s infrastructure could amplify the structural impacts of earthquakes in the future. Investments, such as improving the seismic performance of existing bridges, should reduce the risks from future earthquakes. 

How to Manage the Risk?

Even though earthquakes hit without warning and cannot be prevented, many strategies can be used to reduce the risks associated with them. Risk-mitigation strategies continue to grow more successful as seismologists, geologists, engineers, architects, emergency responders, and other experts innovate new public-safety initiatives in their respective fields. 

The primary strategies involve more robust seismic building code requirements, enhanced seismic design requirements, increased effort to inspect and maintain critical infrastructure, and retrofitting of buildings. 

Protecting Buildings: Regulations, Enforcement, Engineering Strategies, and Maintenance 

The 2023 earthquakes in Turkey and Syria brought renewed attention to the importance of building codes and proper enforcement. In New York City, DOB develops and updates building codes to mitigate risk from earthquakes and enforces these codes through extensive administrative measures. The seismic regulation follows the developments and improvements in national seismic standards. 

Since 1985, FEMA has sponsored earthquake engineering research by the National Earthquake Hazards Reduction Program (NEHRP). Their latest 2020 NEHRP Recommended Seismic Provisions: Design Examples, Training Materials, and Design Flow Charts is the primary source of national seismic design requirements for new buildings and other structures. ¹⁵National Earthquake Hazards Reduction Program, “Effect of Soil and Rock Types,” Earthquake Coordinators.

New York City’s current building code is as stringent as any in the United States, with the likelihood of failure or collapse of a modern, code-compliant structure being the same as that in California. Codes provide general occupancy conditions for less severe earthquakes. Any existing building in New York City that undergoes substantial modification is also required to adhere to these standards. 

Promoting Preparedness 

The USGS developed PAGER (Prompt Assessment of Global Earthquakes for Response) to deliver rapid impact estimates following significant earthquakes worldwide. Within about 30 minutes, PAGER provides updated assessments as new data becomes available. These reports include the number of people and cities exposed to varying shaking intensities, along with projected ranges for fatalities and economic losses. 

To learn more about PAGER and how to subscribe for alerts, visit: PAGER. 

USGS ShakeCast – short for ShakeMap Broadcast – is an automated software system designed to deliver customized ShakeMap products to critical users and activate post-earthquake response protocols. This free situational awareness tool automatically retrieves earthquake shaking data from ShakeMap and compares ground motion intensity against users’ facilities. Based on this analysis, ShakeCast generates damage assessments, inspection priority notifications, maps, and web-based products for emergency managers and other key stakeholders. 

The Evolution of Seismic Building Code Provisions

The first seismic provisions in New York City’s Building Code were signed into law in 1995 and took effect in February 1996. ¹⁶NYC Department of Buildings, “NYC Codes,” City of New York.

DOB further addressed the city’s structural vulnerability to earthquakes in 2008 and subsequently in 2014 and 2022, when it adopted the International Code Council’s (ICC) family of codes as the basis of the New York City Construction Codes. It is important to note that while the NYC Construction Codes adopted the ICC codes, they also amended some portions to be more stringent than the ICC. 

The 2008, 2014, and 2022 Codes aim to make buildings stronger, more flexible, and more ductile — able to absorb energy without breaking in a brittle manner. The Codes have sections on soil types and building foundations. Seismic detailing is required to enable a building’s joints, structural connections, and piping to hold up during an earthquake. 

Under the 2008, 2014, and 2022 Construction Codes, critical facilities such as firehouses and hospitals are required to be designed to both survive an earthquake and also remain open and functional following one. 

In 2014, DOB revised the Construction Codes and moved toward a new concept — the risk-based approach, following the model of the American Society of Civil Engineers Standard (ACSE) 7-2010 for designing and constructing seismic-resistant structures. In a similar manner, the 2022 Code follows the model of ASCE 7-2016. These enhanced codes require that new buildings in New York City are designed so they are less likely to collapse or sustain significant damage during an earthquake. 

The revised code also strengthens the design requirements for prevention of soil liquefaction and takes the city’s unique geologic conditions into account. Building designs must account for site-specific soil conditions and building foundations and must ensure that joints and structural connections are flexible. Special detailing for electrical and mechanical systems, building contents, and architectural components are also specified. 

Code committee work is now in progress for the next revision to the Construction Codes. DOB is also working on a draft of the NYC Existing Building Code, which includes a structural chapter intended to address issues related to seismic loads in existing buildings, among other concerns, by referring the user to the NYC Building Code structural requirements. This initiative aims to improve safety or mitigate hazards in buildings constructed before the seismic requirements were enacted. 

Code Enforcement

To make sure that buildings are built to code, new construction and major renovations cannot begin until DOB has reviewed plans and issued work permits. Most of the details required by earthquake design are subject to special inspections performed by qualified private engineers who are responsible for reporting findings to DOB. 

Engineering Strategies for Retrofit of Existing Buildings

To meet seismic standards, architects and engineers employ several methods to design and engineer the retrofit of older buildings — strengthening connections among building elements, increasing the structure’s flexibility, reducing building mass to minimize impact from seismic forces, and strengthening foundations placed in poor soil to ensure stability. 

For existing unreinforced masonry buildings, connections between structural elements are strengthened by anchoring walls to the roof and walls to the foundation and individual floors within the building, thus increasing the structure’s ability to transfer loads during an earthquake. Another approach is to add steel frames to unreinforced brick walls to increase resistance to out-of-plane forces.¹⁷Dan P. E. Eschenasy, “Cases of Failure of Unreinforced Brick Walls Due to Out-of-Plane Loads.”

Parapets are often the most damaged element of unreinforced buildings. Seismic risk can be reduced by anchoring parapets with bolt diagonal steel struts and repairing their mortar. Alternatively, unreinforced masonry parapets can be replaced by masonry parapets anchored to the building. 

Simple, commonsense solutions are often enough to improve the seismic performance of a structure and to reduce the seismic risk. For example, anchoring or bolting furniture to a wall reduces the risk of injuries from falling objects as well as damage to the contents of a building. Anchoring water tanks on buildings that are six or more stories is another method to reduce the risk that the tower would topple over, potentially injuring pedestrians. Anchoring hot water heaters in houses and apartments prevents buildings from being damaged, thus providing an emergency supply of water to building occupants if the water system fails. 

Guidelines written to protect coastal buildings from flooding and coastal storms also discuss seismic safety issues, in particular, the vulnerabilities of elevated buildings. To protect buildings with a soft story base, solutions focus on lessening the extra load by adding bracing or shear walls, or enlarging or strengthening the columns and piles. 

Routine Maintenance

Routine maintenance on all buildings in New York City is essential to minimize the risks associated with earthquakes. This includes keeping roofs secure and in good condition, securing cornices and aluminum panels, repointing mortar regularly (especially on parapets and chimneys), and fixing all cracks. 

Protecting Infrastructure: Government Guidelines, Inspections, and Engineering Strategies

Earthquakes can cause major damage to infrastructure that was not originally designed to withstand earthquake impacts — older bridges, tunnels, sewers, water supply systems, and wastewater treatment plants. New York City is acting to mandate that new infrastructure be designed to meet more robust seismic loading requirements, and that older infrastructure be retrofitted to meet those standards. Federal, state, and local government agencies all play roles in setting standards for and overseeing the implementation of seismic safety improvements for infrastructure. 

Seismic guidelines for infrastructure govern New York City’s actions in retrofitting older bridges, tunnels, and other critical facilities to withstand risks from earthquakes, and designing new infrastructure according to safer standards. 

Protecting Bridges

After the 1989 Loma Prieta earthquake, which caused extensive damage to several bridges in Northern California, many central and northeastern states began adopting new seismic provisions for highway bridges. 

In New York, bridge owners hired seismologists to assess the risk of this hazard here. The Federal Highway Administration administers seismic retrofits of bridges through local authorities, under a 1991 inspection and rehabilitation program mandated by Congress. In 1998, the New York City Department of Transportation (DOT) developed seismic criteria guidelines, which it updates as new science and solutions emerge.¹⁸ Federal Highway Administration, Seismic Retrofitting Manual for Highway Structures: Part 1 — Bridges (Publication No. FHWA-HRT-06-032), Turner-Fairbank Highway Research Center, U.S. Department of Transportation, January 2006.

New York City began seismic retrofitting of critical and essential bridges in 1998. Transportation agencies serving the New York City area either have retrofitted or are in the process of retrofitting the bridges that they manage. 

Seismic Isolation

Seismic isolation is one of the more common methods of seismic protection in bridges and structures. In New York City, the JFK light rail system uses this method. This approach protects bridges or structures by isolating the earthquake movement from the foundation to the structures. Isolators (rubber and steel bearings) are mounted between the bridge deck and its piers, or between the building and its foundation. Isolators are intended to absorb the earthquake’s energy and minimize the energy transferred to the structure. 

DOT is in the process of retrofitting the Brooklyn Bridge to conform to current seismic performance requirements outlined in the infrastructure codes. Under Contract 7, which began in September 2019 and continued through 2023, DOT worked to improve the load carrying capacity of the arch blocks, strengthen the masonry towers, and focus on repairs of the historic brick and granite components. ¹⁹NYC Department of Transportation, “Infrastructure: Brooklyn Bridge,” City of New York. This retrofit includes replacing the original timber piles with stronger structural piles and reinforcing the masonry elements of the bridge. Other bridges have been replaced when seismic performance was assessed as inadequate.

Seismic assessment of bridges in the New York City area requires evaluating each bridge for performance standards based on whether the bridge is determined to be critical, essential, or other. Retrofitting of older bridges or designs of new bridges should incorporate design elements that fit the level of damage expected from the projected earthquake and allow for repairs required after the event.²⁰Weidlinger Associates, New York City Seismic Hazard Study and Its Engineering Applications: Final Report (Weidlinger Associates Prepared for the NYC Department of Transportation, 1998). NYC DOT, which owns and maintains 799 bridges, is in the process of implementing seismic retrofits of all its critical, essential and other bridges. ²¹NYC Department of Transportation, 2020 NYC DOT Bridges and Tunnels Annual Condition Report, City of New York.

Protecting Other Infrastructure

The New York City Department of Environmental Protection (DEP) is currently conducting several projects to enhance seismic protection of the wastewater treatment system. DEP is retrofitting wastewater treatment facilities and methane gas storage systems to withstand earthquakes, because most were designed and built prior to implementation of the current, more stringent seismic standards. To reduce the risks associated with seismic activity to New York City’s sewer system, DEP is inspecting and repairing structural deficiencies in some of the major sewers. 

DEP is conducting a study to assess the seismic resiliency of our water supply system (water tunnels, piping, clean water pump stations, dams, shafts, and tanks) and to determine the appropriate seismic design standards. Study findings will prioritize areas in the water distribution system requiring retrofits to meet current seismic standards. City Water Tunnel No. 3 (described in the NYC Hazard Environment) is currently designed to strict seismic standards. 

Applying the City’s seismic guidelines, the Metropolitan Transit Authority (MTA), which is administered by New York State, is currently incorporating seismic requirements into its bridge and tunnel restoration projects within New York City. 

Research and Professional Education

Collaboration among seismologists, geologists, engineers, architects, politicians, and emergency managers is required to manage earthquake risks. Further research into the potential impacts of earthquakes on New York City will expand knowledge about this hazard and promote greater public awareness. This research may include earthquake impact modeling of New York City’s unique built environment to estimate potential physical and economic losses, incorporating New York City’s large stock of older buildings, soil conditions, and unique geological characteristics. Examples of the research projects follow. 

In 2023, USGS released a new version of the National Seismic Hazard Model of seismic hazard forecast for the United States from induced and natural earthquakes.²²U.S. Geological Survey, “Short-Term Induced Seismicity Models,” U.S. Geological Survey, October 24, 2019.

Similarly, the Next Generation of Ground-Motion Attenuation Models was a multidisciplinary research endeavor that concluded in 2008. Involving collaboration between academia, industry, and government, this initiative focused on creating a consensus for new Ground Motion Models (GMMs), hazard assessments, and site responses for the central and eastern North American region. This project marked a significant advancement in our understanding and prediction of earthquake ground motions, especially in the western United States. It replaced the earlier models from the 1990s and early 2000s, providing a more robust and reliable estimate of ground motions. ²³Pacific Earthquake Engineering Research Center (PEER), A Roadmap for Next Generation Attenuation Models for Central & Eastern North America (NGA-East) (U.S. Geological Survey, April 2008).

The Earthquake Engineering Research Institute established a New York-Northeast chapter to promote awareness of earthquake risk and to offer educational resources on how to reduce this risk at all levels. The organization relies on interdisciplinary expertise, drawing from the fields of engineering, geoscience, architecture, planning, and the social sciences. 

The Multidisciplinary Center for Earthquake Engineering (MCEER), in collaboration with the Structural Engineering Association of New York, initiated studies to better understand the vulnerabilities of unreinforced masonry buildings in New York City. Working alongside the State University of New York at Buffalo, MCEER completed shake-table tests on prototypes of unreinforced masonry structures. This was a precursor to an extensive program aimed at devising engineered solutions for New York City’s archaic building stock. ²⁴M. Tantala and G. Nordenson, et al., Earthquake Risks and Mitigation in the New York | New Jersey | Connecticut Region, The New York City Area Consortium for Earthquake Loss Mitigation (NYCEM) Final Summary Report. MCEER-03-SP02. (Multidisciplinary Center for Earthquake Engineering Research, University of Buffalo, 2003).

Researchers Simulate Earthquake Shaking New York City Buildings

Source: SUNY Buffalo

Public Education and Outreach

Many New Yorkers don’t realize their community faces earthquake risks. Since earthquakes strike without warning, it’s vital to raise awareness and encourage preparedness. Emergency preparation for earthquakes is much like that for hurricanes, storms, or other disasters and can help you be ready for any emergency. 

NYC Emergency Management (NYCEM)’s Ready New York campaign encourages New Yorkers to be prepared for all types of emergencies, to develop a personal disaster plan, and to stay informed about the entire range of hazards that may affect the City. NYCEM’s Ready New York Preparing for Emergencies in New York City guide explains what to do when an earthquake strikes and the steps to take immediately after. 

NYCEM’s Ready New York Reduce Your Risk Guide includes long-term strategies for homeowners and residents to reduce the potential damage that an earthquake can cause. 

Additionally, NYCEM’s Strengthening Communities program offers grants to community networks to build their emergency preparedness plan and support local community resources. The training program focuses on five key areas/deliverables to build an emergency plan specific to each community: creating a needs assessment; designing community maps of the area where services are provided; building a resource directory; preparing a communication strategy; and creating donations and volunteer management plans. NYCEM staff provide training, coaching sessions, and tools that guide participating networks through the program. 

Earthquakes can inflict psychological harm in addition to physical harm, so it is essential to plan for mental health services as part of any future response and recovery effort. The New York City Department of Health and Mental Hygiene’s (DOHMH) Mental Health First Aid education program alerts the public to the range of potential mental health issues, how to identify warning signs, how problems are manifested, and the types of commonly available treatments. 

FEMA and the Northeast States Emergency Consortium organize annual Great Northeast Shakeout drills to encourage organizations, households, and agencies to practice safety during an earthquake. These drills are an opportunity for groups to update their preparedness plans, restock supplies, and secure items in their homes and workplaces to prevent damage and injuries if disaster strikes. 

Beyond Code Design Shift 

The primary objective of current building codes is Life Safety based on a Risk Category which addressed a seismic event that will give new construction a uniform collapse risk of 1% in a 50-year horizon. This ensures no loss of life during and immediately after an earthquake but does not address the time to reoccupy and reuse a building or a lifeline infrastructure, or replace them if damaged beyond repair. Recovery time is estimated for a typical office building in San Francisco to be 6-12 months for design-level earthquake and ~ 2 years for the maximum earthquake considered in the code. Recovery time depends on building risk and design. In Christchurch, New Zealand, during an earthquake, buildings were too damaged to repair after an earthquake, leading to demolition and rebuilding, which extended recovery. A major earthquake in NYC could require similar reconstruction, lengthening the process even if buildings don’t collapse. 

Growing interest in improving resilience and post-event recovery by public and professionals led to the reauthorization of National Earthquake Hazards Reduction Program in 2018, with a Congressional assignment to the National Institute of Standards and Technology and FEMA to spearhead an effort to identify the needs for improving time for public to re-occupy and re-initiate functions after an earthquake event.  

In 2021, the two agencies published the “Recommended Options for Improving the Built Environment for Post-Earthquake Reoccupancy and Functional Recovery Time.” The concept of Functional Recovery (in addition to Life Safety) is introduced as a post-earthquake performance state in which a building or infrastructure system is maintained or restored, to safely and adequately support basic intended functions of pre-eq use or occupancy of a building, or service level of a lifeline system. The acceptable time to functionally recover after the event may vary for different building uses and lifeline services.  

The new concept of Functional Recovery is human-centered and requires thinking beyond code in a philosophy that combines technical knowledge with implementation and recovery. Initial studies using decision support FR frameworks that account for risk and losses from damage but also time to return to service, have shown significant increase in the benefit to invest in resilience. ²⁵NIST-FEMA Special Publication NIST SP-1254/FEMA P-2090, https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.1254.pdf

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• 21
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• 22
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• 23
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