NESN maintains a collection of seismic instruments around New England to measure both local and global seismic events. The live data collected at the Westport Observatory, as well as all the other stations in the NESN and a link to the latest earthquakes monitored by the U.S. Geological Survey, are viewable using the buttons below.
The New England Seismic Network (NESN) in Weston Massachusetts, installed a seismic vault July 15th, 2011 at the Westport Astronomical Society that hosts 2 instruments. One is a seismometer that measures global earthquakes and the other is an accelerometer that measures big, local ones. While not strictly related to astronomy, we support all scientific research and love to share it with the public.
The seismometer at the Westport Observatory is located in a subterranean vault on-site, protecting it interference from local activities, such as foot traffic from public events at the observatory.
The NESN page has historical drums that recorded the devastating 2011 9.0 earthquake in Honshu Japan as well as the 2010 7.0 Haiti quake and more. You can also view a global map of the latest earthquakes, sorted by size and location. Though big earthquakes like the August 23rd, 2011 event are rare in New England, small ones actually happen often, as they explain.
A classic seismogram is made by a pen held by a weight in a fixed position on top of a spinning roll of paper. During a quake, the inertia of the weight keeps the pen from moving, while the paper drum moves due to the waves. The pen then marks the drum as it moves back and forth. Modern instruments detect these waves electronically, but the principle is the same.
This is the typical sequence of waves created by an earthquake: the fastest moving waves are called p-waves, a pressure wave moving through the earth. The next to arrive is an s-wave, a shear wave also moving through the earth. Finally, the largest pulse of energy arrives in the form of surface waves known as Rayleigh and Love waves. The surface waves are where the largest ground motions take place and when most of the damage is done. They also have a lower frequency than the p and s waves, meaning that the wave arrivals become more spread out.
The time between waves arriving at a seismic station depends on how far the station is from the quake. The farther away the station is, the bigger the difference in arrival times. The difference between the p wave arrival and surface wave arrivals can be as little as a fraction of a second for earthquakes very nearby and as long as tens of minutes for earthquakes far away.
Each wave bounces and refracts off slightly different regions within the earth, leading to the complex structure in each portion. That complexity can be used by computers as a way of measuring actual differences inside the Earth.
Westport News ran a story July 16, 2014 about the instruments installed at the Observatory.