Quakes Could Shake Boston

Early on the morning of April 18, 1906, an earthquake measuring 7.8 on the Richter scale tore through the California coast.

The quake, which had its epicenter near San Francisco, resulted in as many as 2,800 deaths and caused an estimated $400 million in damages when it hit 100 years ago yesterday.

Cambridge may be across the country from the site of that earthquake, but Harvard has suffered its share of seismic events as well.

In the mid 1700s, two earthquakes with magnitudes of at least 6.0 shook the city; since then, several lower-intensity quakes have hit the area. As recently as 2002, Harvard felt tremors from a 5.0 earthquake epicentered in New York that measured 3.0 by the time it reached Cambridge. Earthquake shocks also hit in 1921 and 1982, but leading scholars said bigger quakes are unlikely.

“Most large earthquakes occur along tectonic plate boundaries. San Francisco is on one; Boston is not. A large earthquake is highly improbable in Boston, although one cannot be absolutely ruled out,” said Hooper Professor of Geology Paul F. Hoffman.

However, others said that Cambridge and Boston are as vulnerable to damages caused by earthquakes as San Francisco because of Boston’s weak ground, not because of subterranean tectonic activity.

Eva E. Zanzerkia ’97, an associate program director in the National Science Foundation’s division of earth sciences, found in research done at Harvard that Boston’s thousand acres of man-made fill and river basins actually amplify seismic waves.

According to Zanzerkia’s research, earthquake shocks that enter this softer ground become trapped and echo around the area rather than slowing to a stop as in hard bedrock. As a result, the force of the shock causes much more damage, putting Boston and Cambridge at risk of losing their most historic and populated districts.

While Cambridge is located far away from the country’s deadliest fault lines, Harvard sits atop the world’s epicenter of seismic research.

“The reason the seismology center is in Cambridge is because of the work over many decades of seismologists in the Department of Earth and Planetary Sciences,” said Hoffman.

“Seismologists at Harvard collect and interpret data from a global network of seismograms,” Hoffman added, saying government funding agencies support Harvard’s efforts.

As for whether a 7+ magnitude earthquake like San Francisco’s could hit Boston, Assistant Professor of Earth and Planetary Sciences Miaki Ishii said, “The chances of Boston having an earthquake like one in San Francisco are very small.”