Abstract
To obtain realistic and correct estimates of strong ground motion in the area of construction of the second Severomuisk tunnel, the records of local earthquakes obtained by the Severomuisk seismic station (SVKR) in 2005-2010 are studied (magnitudes M-b of similar to 4.2-5.5, hypocentral distances r of similar to 15-220 km). Stochastic-simulation methods are used to estimate the regional parameters of radiation and propagation of seismic waves in northeastern Buryatia: the stress parameter Delta sigma, shapes of source spectra, wave attenuation at high frequencies (kappa), parameters defining the shape and duration of the acceleration time history, etc. Beforehand, the duration of strong motion as a function of the hypocentral distance was evaluated from the records; the local site amplification A(f) was estimated based on the veloc-ity structure of the region; and the envelope method was applied to estimate the quality function Q(f). The following data were obtained: A sigma approximate to 100 bars; kappa approximate to 0.012 s; Q(f) as similar to 60 f(1.05) for r of similar to 15-30 km, similar to 80 f(1.0) for r of similar to 40-60 km, similar to 90 f(0.9) for r of similar to 100-110 km, and similar to 150 f(0.7) for r of similar to 160-220 km; geometris spreading as 1/r for r <50 km, 1/50 for 50 < r < 150 km, and 1/r(0.5) for r >150 km; and duration as 0 for 0 < r < 5 km, 0.222r for 5 < r < 50 km, and 10 + 0.015r for r > 50 km. These estimates can be used to predict ground motion parameters during future strong earthquakes in the region.
NSTL