| In this study a moment-magnitude (M) based earthquake catalog is developed for 425 northeastern United States earthquakes occurring between 1938 and 2002. Calculation of M for these earthquakes is accomplished using the Biswas and Aki (1984) approach, which uses the amplitudes of coda-waves to estimate seismic moment, and hence M. I have chosen events with known Mo in order to calibrate the coda amplitude moment measurements. For these events, coda-wave amplitudes were measured at different lapse times, coda-wave amplitude decay was plotted as a function of lapse time, and average slope and intercept values were computed. Utilizing these results and the previously determined Mo of the given events, a formula for computing Mo is devised for use with the Weston Observatory broadband digital data. This formula is adjusted to be accurate for the older types of earthquake recordings from the U.S. National Seismic Network and from New England Seismic Network stations. |
