Minor Earthquake in Buzzards Bay a Reminder to Prepare for Disasters

By: Elise R. Hugus
Published: 05/17/11

 A magnitude 2.1 earthquake that took place 12 miles south of Woods Hole on Sunday evening did not make waves on shore, but a Woods Hole Oceanographic Institution geophysicist said it is a reminder to prepare in the event of a more serious natural disaster.

The earthquake, which occurred at 8:39 PM, was registered by the New England Seismic Network’s Weston Observatory at Boston College. An aftershock measuring 1.3 on the Richter scale took place seven minutes later.

According to WHOI senior scientist Jian Lin, the “relatively small” quake was likely too small to be felt on land beyond the Elizabeth Islands.

He said the most likely reason for an earthquake was a “stress adjustment” in the sea floor terrain caused by the retreat of the glacier 12,000 years ago.

“It takes a long time to adjust,” said Dr. Lin. “Whether we feel an earthquake or not depends on location. It’s magnitude and location, location, location.”

Each level of magnitude on the Richter scale is a factor of 30, he said. Putting Sunday’s event in context, Dr. Lin said it would require 30 billion magnitude 2 earthquakes to create the same energy as the disastrous March 11 quake off the coast of Japan.

Past lessons, future preparations

The largest recorded earthquake in Massachusetts took place off the coast of Cape Ann on November 18, 1755, said Dr. Lin. At a magnitude of about 6, more than 1,000 families were forced to evacuate from Boston and tremors were recorded from Nova Scotia to South Carolina.

If a similar earthquake were to occur today, the damage would likely be more significant because of the increase in population and buildings, said Dr. Lin.

Geologists do not know if there are fault lines in the Cape Cod area, Dr. Lin said. “There are many things undersea that we have no idea about,” he said.

The earthquake and related tsunami disaster in Japan have taught geologists and urban planners a number of lessons, said Dr. Lin, who is currently in San Francisco researching that event.

“Japan has a much longer [earthquake] record, but they thought the area would have a maximum of [magnitude] 8. They built tsunami walls to sustain that. The major lesson is that you cannot plan based on your short records,” he said.

Cape Cod is “absolutely in danger” of a tsunami, said Dr. Lin. For such a scenario to take place, the earthquake would have to occur dozens of miles offshore, where terrain is steeper and more unstable, he said.

Although earthquakes are rarely felt on the East Coast, the New England Seismic Network regularly records tremors from Quebec to Long Island.

“Earthquakes in Massachusetts are much less infrequent than in California, but because of that, we should prepare for something bigger than a [magnitude] 6,” said Dr. Lin. “It could happen.”