By: David Geller, CPCU, SCLA
Experience can sometimes be the best teacher. While COVID-19 remains a threat for today, the catastrophic impacts that it has wrought may serve as a risk management lesson in the years to come. Human nature may sometimes steer us to dismiss the potential for low frequency/high severity risks. But if the COVID-19 outbreak has taught us nothing else, it is that these once in a generation disasters may be the most important exposures of all.
This article is Part II of the ISO Emerging Issues team’s Actually, It Can Happen To Us series, an effort to identify low frequency/high severity risks that could be overlooked. Check out Part I of our series, which explains Solar Storms, here.
Upon the mention of the word “earthquake”, it would be natural for an American adult’s mind to immediately wander towards sunny California, the site of the Great 1906 San Francisco Earthquake, the Bay Area earthquake in 1989, and the blockbuster film San Andreas, which features The Rock doing The Rock things in the midst of an enormous California earthquake.
But how many of these people would then consider the Empire State Building or a concentration of residential walk-ups as the Earth beneath them shifted?
The truth is, unless you are 136 years old, you don’t know what Manhattan—or the outer boroughs—looks like in the aftermath of a significant earthquake. However, geography and science support the fact that not only can the Big Apple get hit with an impactful earthquake, but it may even be overdue for one.
Lay of the Land: New York
In a 2018 Long-term National Seismic Hazard Map published by the United States Geological Survey (USGS), New York City, as well as the southeast corner of New York State and the northwest corner of New Jersey, are considered to be at “moderate” risk of an earthquake.
Perhaps a factor driving this categorization is that there are a handful of faults in, or at least in proximity to, New York City. According to NY1, here are some of the faults:
- 125th Street Fault – The largest fault in New York City, it extends from New Jersey to the East River, while partially running to the northern tip of Central Park and extending to Roosevelt Island.
- Dyckman Street Fault – Located in Inwood, crosses the Harlem River and into Morris Heights.
- Mosholu Parkway Fault – North of both the Dyckman Street Fault and 125th Street Fault.
- East River Fault – The top portion of this fault runs parallel to the western side of Central Park, it then turns horizontally on 32nd street all the way into the East River—where it stops just short of Brooklyn.
- Dobbs Ferry Fault – This fault is located outside of New York City, in suburban Westchester.
- Ramapo Fault – Similar to Dobbs Ferry, this is also not within the confines of New York City; it runs from Eastern Pennsylvania to the mid-Hudson Valley, less than 40 miles north of NYC. Of note, it is only a few miles northwest of the Indian Point Nuclear Power Plant in New York State.
NY1 does state that New York is not close to a tectonic plate, and it is uncertain which one of these faults—if any—would be the source of a strong earthquake.
New York’s Seismic History
Nevertheless, despite this uncertainty, history does indicate that New York has been hit with impactful earthquakes, and that it will eventually happen again. According to NY1, researchers believe that New York is susceptible to a magnitude 5 earthquake once every 100 years, a magnitude 6 around every 670 years, and a magnitude 7 every 3,400 years.
Per the article, a magnitude 5.2 earthquake shook Manhattan back in 1884 and 1737. These instances are reportedly the only two known New York based earthquakes to register at least a 5, although a 4.9 did hit North Central New Jersey in 1783 and was felt in New York.
Some readers who reside in or near New York may be quick to remember experiencing an earthquake in 2011, but the epicenter of that one was in Virginia, meaning that New York’s relative seismic slumber has continued past the century mark.
How Exactly is New York Vulnerable? Building Construction and Soil Composition Play a Key Role
There are a myriad of factors that can serve to exacerbate—or mitigate—exposure to the worst damages that an earthquake can cause. While New York isn’t necessarily as susceptible to experience enormous earthquakes as its West Coast counterparts, even a moderate one can threaten to levy huge damages given how the city has been developed and its inherent features.
One reason why New York may be poorly positioned to handle a magnitude 5 earthquake is because it took until 1995 for seismic provisions to be included in the Building Code, according to an NYC Hazard Mitigation page. The website notes that much of the construction of the city’s building transpired prior to 1995, meaning that relatively few buildings currently located throughout the city were erected with earthquake protections in mind.
Relatedly, a report published in 2003 by The New York City Area Consortium For Earthquake Loss Mitigation (NYCEM) pointed out that unreinforced brick buildings, which are prominent in NYC, are most vulnerable to an earthquake because the walls in these buildings are prone to collapse outward. Additionally, the NYC Hazard Mitigation page also points out that these unreinforced buildings generally are attached in rows and rely on each other for stability. Of note, this reportedly means that buildings which reside at the end of a block or next to a vacant lot may be most vulnerable during an earthquake.
According to the NYCEM report, over 200,000 buildings in NYC are unreinforced brick, with the most located in Brooklyn (165,561), per the Hazard Mitigation page, which also contains visuals reflecting which neighborhoods could be most exposed to the highest costs in the event of an earthquake.
In addition to building construction, the composition of soil is another dynamic that could heighten the risk of major damage inflicted during a New York earthquake. According to NY1, harder soil could make the land more resistant to shaking. Conversely, softer soil may increase the potential for damage to buildings. Unfortunately, the Hazard Mitigation page points out that soft surfaces are commonplace throughout New York City, both due to circumstance and development plans:
A large portion of New York City's waterfront originated as wetland or wasteland that was filled in, reclaimed, and built up over time. New York City has recently adopted new 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.
The Hazard Mitigation page also points out that, “during an earthquake event, soil liquefaction could result in large-scale ground failure that damages pavements and building foundations and massively disrupts underground utilities.” Among the areas that consist of artificial fill and are thus most vulnerable to soil liquefaction are: JFK Airport, the World’s Fair site in Queens, and Chinatown. According to the NYCEM report, Chinatown and Manhattan’s Upper East Side are most vulnerable to severe damages from an earthquake, due to softer soils and a proliferation of unreinforced masonry buildings.
While building damage from a seismic event is a major concern, experts are also reportedly concerned how infrastructure would respond in the event of an earthquake. According to the Hazard Mitigation page, while there have been some improvements made to existing bridges and other infrastructure to improve its seismic resilience, it generally remains poorly understood how NYC’s critical infrastructure systems are interlinked and what the level of exposure may be.
Additionally, questions continue to proliferate regarding how critical infrastructure outside NYC, such as dams, nuclear power plants, and facilities that contain hazardous material, would handle an earthquake as well.
What is NYC Doing to Prepare?
Since the first seismic building codes for NYC were passed in 1995, additional steps have been taken to mandate earthquake protections into NYC structures, such as the Department of Building’s (DOB) adoption of the International Code Council’s family of codes as the New York City Construction Codes in 2008, per NYC Hazard Mitigation, which also explains that:
The 2008 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 Construction Codes, critical facilities such as firehouses and hospitals were required to be designed to both survive an earthquake event and to also remain open and functional following one.
In 2014, per the NYC Hazard Mitigation page, the DOB revised the Construction Codes to follow the model of American Civil Engineers Standard 7-2010 for designing and constructing seismic-resistant structures, which requires “that new buildings in New York City are designed so it is less likely they will collapse or sustain significant damage during an earthquake.”
Lastly, to account for the inherent vulnerabilities posed by the prevalence of soft soil that structures all across New York are erected upon, “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.”
While more stringent standards may assist in mitigating the potential of losses to brand new buildings, the vast majority of buildings entrenched in Manhattan were built prior to these codes being implemented, as evidenced by a visual in page 26 of the NYCEM report.
Ultimately, while recent efforts indicate that New York is taking the potential for an earthquake threat more seriously in the last couple of decades, a rigorous and lengthy effort may be required (see the “Engineering Strategies for Retrofit of Existing Buildings” resource for more details here) to avoid a major disaster following an earthquake—whenever it may be.