earth and environmental sciences
CRUSTAL STRUCTURE AND SEISMICITY OF NEW ENGLAND
Using data from the New England seismic network, we are investigating the causes and effects of regional earthquakes. Research is in progress to better understand the seismic structure of the Earth beneath New England, to determine more reliably the sizes of local earthquakes, and to locate more accurately earthquake hypocenters. We are also exploring relationships between earthquake activity and faults or other geological features in this region.
EARTHQUAKE FORECASTING RESEARCH
Although earthquake prediction remains an elusive goal, it is possible to forecast the general characteristics of future earthquakes at some level of detail. An earthquake forecast is a long-term statement of probability of one or more earthquakes occurring in a region. Our research in this area is focused on discerning the level of detail that can be known about the spatial and temporal characteristics of future earthquake processes. We are investigating the extent to which the distribution of seismicity in a region delineates where future earthquakes are likely to occur, as well as the extent to which non-random patterns in the temporal distribution of seismicity might indicate increased probability of earthquakes occurring.
SEISMIC HAZARD STUDIES
The determination of the probabilities of different levels of expected ground shaking in future earthquakes is vital information if engineers are to successfully build structures to withstand earthquakes. The analysis of seismic hazard for New England using standard methods as well as the development of new methods of seismic hazard analyses are the major goals of this research. The spatial patterns of earthquake occurrences, the patterns of strong ground motions generated by earthquakes, and the variations of source properties from earthquake to earthquake are some of the topics addressed in this line of research. One project currently under way is to study the effect of ground shaking amplification due to landfill and other soft soil in the Boston area.
REGIONAL AND EDUCATIONAL SEISMIC NETWORKS
Seismologists at Weston Observatory have been recording earthquakes for many decades. We currently operate the 12-station New England Seismic Network to monitor earthquakes in the Northeastern United States, as well as an educational seismic network consisting of seismographs in high schools and middle schools. These networks provide seismological data that are used not only for monitoring regional and global earthquakes and assessing earthquake hazards, but also for exploring the structure of the Earth's interior.
SYNTHETIC SEISMOGRAMS, MODELING EARTHQUAKE SOURCES AND EARTH STRUCTURE
Modern seismic source theory and wave propagation methods can be programmed into a computer to allow the theoretical prediction of earthquake seismograms. These theoretical (or synthetic) seismograms can be used to study the details of an earthquake source or the structure of the deep interior of the Earth. We are using synthetic seismogram methods to study the details of earthquake sources in such places as New England, California and Germany to better determine the active seismotectonics of these areas. We are also applying synthetic seismograms to the study of the internal structure of the Earth, particularly the crust and upper mantle.
PALEOSEISMIC STUDIES IN NEW ENGLAND
Documentation of the maximum credible earthquake that can be expected in a region is fundamental to the assessment of the seismic hazard within the region. New England and adjacent portions of the northeastern United States and Canada is a large region of active seismicity with recorded earthquakes approaching magnitude 6. Paleoseismic investigations of more active centers of seismic activity are warranted because these regions may have experienced a past, even pre-historic, large earthquake. Studies of unconsolidated sediments of Pleistocene and Holocene age may uncover deformational features characteristic of such past large earthquakes. One project under current investigation is a search for paleo-earthquake indicators in the geology of northeastern Massachusetts and southeastern New Hampshire. This area had a strong earthquake in 1727 and there is good geologic evidence for earthquakes within the past few thousand years.