Propagation and Excitation of Lg, Sn, and P-Pn Waves from Eastern United States Earthquakes by Regression Analysis of RSTN Data. Seismic Attenuation Studies at United Kingdom Arrays

摘要

By applying regression analysis to amplitudes of the regional phases, pn, sn and lg in various frequency ranges we have derived the attenuation rates, extrapolated source spectra, and relative site responses for these phases in eastern north america using RSTN data. Observed regional phase amplitudes are modeled with three parameters. The estimates source excitation levels for all three phases exhibit high-frequency falloff rates between 1/f-sq-2 and 1/f-cubed -3 and have approximately the same shape. The average day and night noise levels of the RSTN stations were also measured as part of this study. The seismic noise displacement amplitude falls off roughly as 1/f-sq-2 over the frequency band from 1 TO 20 hz. A diurnal variation in the noise levels is observied at all of the RSTN sites, with the daytime noise averaging from 1.5 to 3 times higher than the nighttime noise. 2). the productivity of any future U.S. researchers using Blacknest data and of the Blacknest staff themselves will be significantly enhanced if the interactive graphics capability of the sun workstation were used for the analysis of seismic array data. It was therefore decided that the objective of this task would be to devise data base display and analysis software that could be used on the sun workstation at Blacknest. in particular, software would be installed that would make the Blacknest data accessible by programs already written to handle data.