Engineers study effects of a major earthquake on Boston’s historic buildings

Last Tuesday Morning about half an Hour past Four o’Clock, the Weather being serene, the Air clear, the Moon shining very bright, we were surpriz’d with a most terrible Shock of an Earthquake: The conditions were so extreme as to wreck the Houses in this Town to such a degree that the Tops of many Chimnies, and some of them quite down to the Roofs, were thrown down.

Sonia Sorabella, a graduate student in civil engineering, and Tufts engineer Eric M. Hines figure that Ballou Hall, shown behind them, probably would survive a major earthquake. © Melody Ko

This report from the Boston Weekly News-Letter on November 20, 1755, described an earthquake whose magnitude was estimated to be between 6 and 6.5 on the Richter scale. Although New England has had many minor earthquakes since then, this was the last major earthquake to hit the Boston area. Could it happen again? And if it did, what would happen to the buildings in the region?

A major earthquake could indeed happen again, says a Tufts engineer, and in the Boston area, there are historic buildings—including Tufts’ own Ballou Hall—that could be severely damaged because of the way they were constructed.

Students in the civil engineering department are making a detailed inventory of buildings in and around Boston and also developing models to show what would happen if a major earthquake occurred. The work is under the direction of Eric M. Hines, a research assistant professor in civil and environmental engineering, and Laurie Gaskins Baise, an assistant professor in the same department.

Scrounging for detail
“People have been doing this type of work in Boston for more than 30 years, so we see ourselves as working in the midst of a very long tradition,” Hines said. “In the past, people have assessed the inventory based on very basic assumptions about the types of buildings. Our project is to take the existing work a step further. In the past, someone would have said, ‘That’s a steel building.’ We ask, ‘What are the connections like? Is the steel encased in concrete? Is it riveted together?’ Instead of emphasizing an entire building inventory, we’re interested in looking at specific buildings in detail.”

And, Hines said, because there are no actual recordings of major earthquakes in the Boston area, a group of Tufts undergraduate and graduate students will study the geology of the region and also look at earthquakes in other parts of the country to determine “what an earthquake would look like here.”

“A lot of the code requirements in this area of the country are heavily influenced by experiences in California in the last 15 years,” said Hines. “There was the Loma Prieta earthquake near San Francisco in 1989 and the Northridge earthquake near Los Angeles in 1994. Both were responsible for a large wave of seismic research for all types of structures, developed with California and other high seismic regions in mind. Our goal is to take the knowledge gained in California and think very carefully about how it should be applied appropriately in Massachusetts, using state-of-the-art tools and state-of-the-art data.”

Hines said students will be collaborating with researchers at Michigan State and the University of Massachusetts at Amherst, both of which have large-scale structural testing facilities. In particular, one student is studying buildings that were made with un-reinforced masonry—many of which are among Boston’s most historic buildings.

What about Ballou?
Sonia Sorabella, who earned an undergraduate degree in engineering from Tufts last year, is now a graduate student in civil and environmental engineering and has received both a Tufts Graduate Research Award and a Freeman Fellowship from the American Society of Civil Engineers. She is working to develop a catalogue of information about un-reinforced masonry buildings, including Ballou Hall, the oldest building on Tufts’ Medford/Somerville campus.

Built in 1852, at one time Ballou was the campus, housing the entire university, including a dorm, dining hall, offices and classrooms. But like all masonry buildings built well into the 1800s, the brick was not reinforced, meaning there are no steel rods going through the masonry to support the building. Among other well-known buildings made of un-reinforced masonry are Faneuil Hall and Trinity Church, both in Boston.

Sorabella wants to create an inventory of such buildings and find a way to calculate what would happen to them in a major earthquake. She also will learn whether any of these buildings have been reinforced since they were first constructed and recommend what might be done to make them stronger.

The problems of old masonry
Often, Sorabella said, un-reinforced masonry buildings undergo a change of use, such being converted from a warehouse into office space. “That’s when buildings could be upgraded,” she said. One upgrade might be anchoring parapets—the low walls in front of a roof that can easily topple in an earthquake. Another would be to tie the floor structure to the wall. If floors are untied, she said, the outside and inside of the building can shake separately during an earthquake. If they are tied together, the wall can take more stress.

As for Ballou Hall, Sorabella’s preliminary calculations show that if the walls and floor held together, there is a high probability that the building would not collapse and would be safe for use after an earthquake. She is unable to tell from original drawings whether the walls and floors are tied together and will be doing further research to figure that out.

Sorabella grew up in Somerville and is enjoying the fact that her research involves examining some of the buildings she grew up seeing as a child. “It’s interesting and fun to see how we can apply what we’ve learned in class,” she said.