|
In a one-story brick building built on bedrock, John E. Ebel monitors the size and heft of small earthquakes that rattle parts of New England every year. For three decades, the Boston College professor and seismologist has recorded quakes around the region, sticking red pins into a large map that displays tremor clusters from Maine to Rhode Island. He distributes the information to a network of seismologists worldwide and worries, always, about what could happen if a damaging earthquake strikes New England. “We definitely have the potential,’’ said Ebel, 56, director of Boston College’s Weston Observatory, a geophysical research laboratory. “We don’t know when the next earthquake will strike.’’ The earthquake that devastated Haiti Jan. 12 has provided Ebel the spotlight to tell anyone who will listen that such an event - although rare - could also hit this part of the United States. He’s part of a growing group of researchers, emergency management specialists, and structural engineers readying for such a local catastrophe and debating how much realistically can be done to reduce risks. Like Ebel, they wonder what a substantial jolt would do to the region’s many old brick buildings - including schools and fire stations - which were not built to modern seismic codes and, in many cases, are sited on old landfills that amplify ground vibrations. “A small shake is fine. If there is anything of serious seismic intensity in the range of 6.0 or higher on the Richter scale, we’ll have havoc around here,’’ said structural engineer Mysore Ravindra, president of LeMessurier Consultants in Cambridge. The magnitude of an earthquake is determined by the size of its seismic waves, or ground shaking, measured on the Richter scale, which was devised by Charles Richter of the California Institute of Technology in 1935. The measure is based on a logarithmic scale, which means that for each whole number increase on the scale, the amplitude of the ground motion on a seismograph goes up 10 times. The recent earthquake in Haiti was a magnitude 7. No one is suggesting there is cause for panic. The last major earthquake here occurred in 1755 off Cape Ann, an estimated 6.3 temblor that was felt from Nova Scotia to Maryland. Californians in one year experience the same number of earthquakes that happen over a century in New England, Ebel said. But that doesn’t mean a damaging earthquake couldn’t happen today. Before last month, a major quake had not hit Haiti since 1897. “It is something we take seriously,’’ said Peter Judge, spokesman for the Massachusetts Emergency Management Agency, which stages earthquake-related training every few years. “The worst-case scenario is an earthquake in wintertime.’’ New England sits on the center of the North American tectonic plate, one of nine large plates that make up the earth’s crust. While many earthquakes occur along plate boundaries, such as in California and Haiti, in New England they happen on faults that are reactivated as the earth is squeezed by plates along the West Coast and mid-Atlantic states. About 20 small quakes affect New England annually; the largest recent one was a magnitude 4.2 in 2006 near Bar Harbor, Maine.Continued... |
