Yes. Earthquakes do occasionally occur in the Boston area.
Most earthquakes occur along faults at or near the boundaries between tectonic plates. The earth's outer layer consists of numerous tectonic plates that slowly move across the surface of the earth.
Green dots show the distribution of earthquakes worldwide, outlining the boundaries between tectonic plates. (Red triangles show volcanoes) Source: Unavco
Sometimes tectonic plates move past each other smoothly, but sometimes, friction at their contacts causes them to get stuck. An earthquake occurs when rocks that are stuck, suddenly slip past one another, and release energy that causes ground shaking. This energy can be recorded by a seismometer.
Animation showing rocks slowly moving on either side of a fault, then "snapping" during an earthquake. Source: USGS via Giphy
The process is somewhat similar to a large slab of snow suddenly sliding off your roof in the winter (and the sound it makes is analogous to the energy released).
Snow sliding off roof in a mini earthquake. Source: Giphy
But Boston is not located along an active tectonic plate boundary.
Instead, it is thought that earthquakes in the Boston Area occur along zones of weakness in earth's crust, likely related to the presence of ancient faults that may have been active millions of years ago during the formation of the Appalachian Mountains. These earthquakes may help the plate adjust in response to stresses caused by their motion across the earth.
The exact causes of earthquakes in New England, and the locations of the faults that can produce earthquakes is a subject of ongoing research. Check out some recent work by scientists at Boston University, MIT, and Boston College about earthquakes in New England:
You can learn more about Earthquakes in New England here:
Author: Emerson Lynch
Liquefaction is what happens when the ground acts like quicksand during an earthquake.
Material that is grainy and not well consolidated (like sandy soil) can hold a lot of water in pore spaces (or spaces in between the grains). When earthquake waves move through this material, it shakes, and the pressure of the water in the pore spaces pushes the grains apart and causes the material to liquefy.
Where does liquefaction happen?
Liquefaction happens where there is:
1. Loose, granular sediment that is
2. Saturated with water
3. Strong shaking
In other words, liquefaction can happen:
- Near rivers
- At beaches
- In areas built out over water
- In filled swamps or wetlands
Could liquefaction happen in Boston?
Yes! During the 1744 earthquake in Newburyport, MA, liquefaction caused multiple sand blows in southern New Hampshire and northern Mass.
(image from the Northeast States Emergency Consortium).
While the likelihood of an earthquake is not very high in New England [see Earthquakes in Boston, and Historical New England Earthquakes], the potential damage from liquefaction is high in areas that are poorly consolidated and saturated with water, like areas built on artificial fill such as Back Bay, a neighborhood near Boston University, which used to be an actual bay before it was filled with trash, mud from South Bay, and gravel from Needham, Mass.
Here in Boston, artificial fill makes up a lot of the city – over 5,000 acres! The areas filled between 1630 and 1995 are in light green in the map below:
(image adapted from National Geographic)
Any buildings built on artificial fill could be severely damaged by liquefaction, such as this apartment complex in Niigata, Japan after an earthquake in 1964:
A study conducted in 2004 looked at liquefaction hazard in the Greater Boston Area. Take a look at the map on page 52 to see if your house is at risk!
Explore liquefaction further!
Learn more about earthquakes and hazards in New England here:
Text modified from IRIS: www.iris.edu/hq/educational_resources and NatGeo: https://news.nationalgeographic.com/2017/06/Boston-landfill-maps-history/
Niigata image: https://www.geological-digressions.com/liquefaction-more-than-an-interesting-phenomenon/
Author: Emily Schottenfels
When we think of natural disasters in Boston, what comes to mind are hurricanes, floods, sea level rise, or possibly fires, Snowmageddon, and even the occasional Great Molasses Flood. Earthquakes are not our greatest concern, yet there are records of earthquakes that shook New England, causing serious damage to infrastructure and lasting impacts to society.
According to the United States Geological Survey, New England has a low to moderate earthquake hazard. Most of the earthquakes in New England have been <5.0 magnitude (Mw), but some significant earthquakes >Mw 5.0 occurred in the last few hundred years.
What kind of damage can an earthquake cause to Boston? Let’s take a look at significant historical earthquakes in New England to learn more.
US Geological Survey (USGS) seismic hazard map
Wait, how do we know the magnitude and locations of earthquakes before modern technology?
Unlike earthquakes today, the intensity of historical earthquakes cannot be measured directly using instruments. Instead, we rely on personal accounts of historic earthquakes including location, intensity of shaking, damage to infrastructure, and feeling aftershocks. These personal recollections are classified according to a scale of earthquake intensity, called the Modified Mercalli Intensity Scale. This scale, denoted by Roman Numerals, ranges from imperceptible ground shaking to catastrophic destruction of well-built structures. The Modified Mercalli Intensity Scale is then mapped, and the earthquake magnitude is determined based on this spatial distribution. While personal accounts may cause some uncertainty surrounding historical earthquake magnitudes, this approach combined with geologic and seismic knowledge of the area, provides strong estimates for past earthquakes.
Modified Mercalli intensity Scale (USGS)
Historical earthquakes in New England
Not long after European settlers arrived on the Mayflower, a severe earthquake, now considered to be between a Mw 6.5 and Mw 7, struck central New Hampshire on June 11, 1638 (dates may differ due to changes from the Julian calendar). Although there are not many personal records of the event, the earthquake was felt along the St. Lawrence River in Quebec by Native Americans at Trois Rivieres and all the way to Boston, where people lost their footing and fell to the ground. A noticeable but an undetermined number of aftershocks continued to shake New England for months afterwards. This event impacted settlers to such a degree that New Englanders often dated events based on the years "so long since the earthquake."
Governor John Winthrop of Massachusetts Bay Colony recorded in his journal,
Still no rest for the early settlers:
About 25 years after the 1638 New Hampshire earthquake, the largest known earthquake to rock New England occurred on February 5th, 1663 with a magnitude 7.5 in Charlevoix, Quebec. This large earthquake caused extensive damage across the northeast. In Boston chimneys fell, walls collapsed, and people ran into the streets to seek refuge. In Quebec, the earthquake uprooted trees, triggered landslides along the St. Lawrence river, and many aftershocks shook the region for months.
Rev. Danforth of Roxbury, MA noted,
Chim chiminey, chim chiminey, chim chim cher-ee:
The largest earthquake to strike closest to Boston was the 1755 Cape Ann Mw 6.2 earthquake. The Cape Ann earthquake damaged hundreds of buildings along the east coast from Halifax, Nova Scotia to Winyah, South Carolina. In addition to historical accounts of shaking, the intensity of this earthquake was determined by records of damage to infrastructure, specifically to chimneys. Reports of chimneys across New England with no damage, minor damage, or extensive damage were used to determine the location and intensity of the earthquake. Of approximately 5000 documented chimneys in Boston at that time, roughly two thirds were moderately to severely damaged by the quake and roughly 100 chimneys in Boston were leveled. Reports from other towns in the northeast, such as York, Maine, Braintree, MA, Northampton, MA, New Haven, and NYC, all indicated damage to chimneys. Beyond chimney damage, brick walls and stone fences fell down, and there were reports of cracks in streets in Eastern Massachusetts.
The Boston Weekly News-Letter reported on Nov. 20th, 1755:
Photo depicting the scenes of the earthquake. Source: New England Historical Society
Double the fun:
On December 20th and 24th, 1940, two earthquakes of similar magnitude (Mw5.5) rocked New Hampshire at the northern base of the Ossipee Mountains. Though the first shock was stronger, the second shock may have caused more damage since the structures were already weakened by the first shock. Nearby towns reported chimney damage, muddy well water, cracked walls, and broken furniture. Reports of minor damage stretched across Maine, New York, Vermont and Massachusetts. The shocks were felt from Quebec to Connecticut.
According to the Springfield Republican Newspaper, in Springfield, MA,
Intensity of shaking map of the 1940 earthquake in New Hampshire (Ebel, 1996)
More Information on Earthquakes in New England
Earthquakes in New England are caused by the fracturing of preexisting “weak” regions, which are due ancient tectonic activity. Ancient faults identified and mapped by geologists could reactivate, but it is not well understood if the earthquakes in New England even occur on these known faults. Additionally, much of the Boston area is built on unconsolidated sediments. This increases the likelihood of liquefaction, which amplifies ground shaking and causes more damage to infrastructure.
It wasn’t until the 1970s that researchers in New England installed a seismic network to monitor and detect earthquake on a regular basis. Since then, thousands of earthquakes have been detected, but not enough information has been gathered to understand which faults are active and host earthquakes.
Though large earthquakes in Boston are few and far between, they can still cause extensive damage. Check out this website to learn more about earthquakes in New England, and this website to get the latest info on earthquakes from the New England Seismic Network.
Weston Observatory, New England Seismic Network
Earthquakes in Boston, Boston Globe article
USGS 1638 earthquake
1663 Earthquake, from the New England Historical Society
The Northeast States Emergency Consortium (NESEC)
Ebel, J. E., Somerville, P. G., & McIver, J. D. (1986). A study of the source parameters of some large earthquakes of northeastern North America. Journal of Geophysical Research: Solid Earth, 91(B8), 8231-8247.
Ebel, J. E. (1996). The seventeenth century seismicity of northeastern North America. Seismological Research Letters, 67(3), 51-68.
Ebel, J. E. (2006). The Cape Ann, Massachusetts earthquake of 1755: A 250th anniversary perspective. Seismological Research Letters, 77(1), 74-86.
Author: Miranda Wiebe
First of all, why should you care?
Turbidites are sedimentary rocks that act as a unique “tape recorder” of past earthquakes -- earthquakes that occurred long before humans were around to feel them. This is due to the fact that earthquakes trigger the formation of turbidites, and so the non-turbidite rock deposits in between turbidites can give a sense of the length of time between earthquakes.
Having this record of past earthquakes enables scientists to make statistically significant predictions about future earthquakes. The ability to predict future earthquakes enables humans to better prepare for the immense destruction that these natural disasters can cause.
What is a turbidite?
Turbidites are the consequence of turbidity currents, which are essentially underwater landslides that occur due to sediment accumulation along an underwater shelf. Turbidity currents spread sediment throughout sea channels, as shown in the video below:
Source: Oregon State
How do we identify a turbidite?
Turbidite sediment deposits display “normal grading,” or decreasing grain size upwards from the base of a deposit. Turbidites distinguish themselves from other deposits by following the “Bouma sequence” (Fig. 1). The Bouma sequence is characterized as:
Figure 1: A turbidite deposit in a rock, from the Pigeon Point Formation, Pescadero Beach, California. This turbidite shows layers A-D of the Bouma sequence. Source: Wikipedia.
What causes a turbidite?
In order to trigger the turbidity current that produces a turbidite, there must be some force applied to the area. In many cases, that force is an earthquake. Earthquakes can also trigger shelf collapse, which is another method of generating a turbidity current.
How can turbidites be used to extrapolate earthquake records?
If we take the example of the Cascadia margin, located along the Oregon-Washington coast, we see that an extensive turbidite record can be used to reconstruct the history of earthquakes in the region. (Definition: in this case, a margin is the area along which oceanic crust is crashing into continental crust).
Adams (1990) first suggested that the best explanation of the turbidities are the 13 earthquakes that occurred along the Cascadia margin. When investigating the patterns of timing between turbidite deposits, Adams (1990) found that they matched well with those of great earthquake cycles.
Furthermore, the thickness of the sedimentary layer that tops the turbidites indicates that the last turbidity current occurred roughly 300 years ago, which is consistent with the most recent extensive earthquake event on the Cascadia margin (Adams 1990; Sanders 2005).
Research preformed more recently by faculty at Oregon State University supports the hypothesis put forward by Adams (1990) (Goldfinger et al. 2003). Fig. 2 shows locations of samples taken from the turbidites off the Cascadia margin, both by Adams (1990) and the Oregon State researchers.
Figure 2: Map showing locations of turbidite core samples taken off the coast of Washington and Oregon, on the Cascadia margin. Cores from Adams (1990) are in grey, cores from Oregon State researchers are in yellow. From Oregon State University (2003).
How can turbiditic data help us predict future earthquakes?
Using his turbiditic data to extrapolate patterns in earthquake frequency, Adams (1990) was able to predict that in the next 50 years, there is a 2-10% chance of a great earthquake occurring. Using similar statistical methods, Oregon State University (2003) found that the probability of a full margin rupture along the Cascadia margin in the next 50 years is 7-11%. Similar predictive statistics can be utilized at almost any other continental margin which contain complete turbiditic sequences.
What does this mean for New England?
Historically, New England has suffered earthquakes much smaller in magnitude than Oregon and Washington.
However, turbidite deposits in New England turbidites can be used to determine the timing of past earthquakes in the region. For example, the most severe earthquake on record is the Cape Ann earthquake which occurred in 1755 (Monecke 2018). In Lynn, Massachusetts’s “Sluice Pond,” there are lake sediments deposited in 1740 and 1810 that are interpreted to be turbidites deposited during the intense ground shaking in 1755 (Monecke 2018).
These findings imply that organic-rich sediments in small ponds around New England contain a historical record of earthquakes in the region (Monecke 2018). Perhaps these records may one day be used to predict future earthquakes in the region, which, if the correct magnitude and location, could cause a tsunami in New England (Koebler 2013).
Want to learn more?
Adams, J., 1990, Paleoseismicity of the Cascadia subduction zone; evidence from turbidites off the Oregon-Washington margin. Tectonics., v. 9(4), p. 569.
Goldfinger, C., Nelson, C.H., and Johnson, J.E., 2003, Deep-Water Turbidites as Holocene Earthquake Proxies: The Cascadia Subduction Zone and Northern San Andreas Fault Systems: Annali Geofisica, v. 46, p. 1169-1194.
Koebler, J., 2013, Study: Boston, New England at Greatest Tsunami Risk in US: https://www.usnews.com/news/articles/2013/04/19/study-boston-new-england-at-greatest-tsunami-risk-in-us (Accessed September 2018).
Monecke, K. et al., 2018, The 1755 Cape Ann Earthquake Recorded in Lake Sediments of Eastern New England; an Interdisciplinary Paleoseismic Approach.: Seismological Research Letters Pre-Issue Publication, p. 1212-22.
Oregon State University, 2003, Cascadia Paleoseismic History Based on Turbidite Stratigraphy: http://activetectonics.coas.oregonstate.edu/cascadia_turbs.htm (accessed September 2018).
Sanders, R., 2005, Sinking coastline may precede large subduction zone quakes: https://www.berkeley.edu/news/media/releases/2005/01/20_marshes.shtml (accessed September 2018).