Characteristics of Radiation and Propagation of Seismic Waves in Northern Finland, Estimated Based on Records of Local Earthquakesстатья
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Дата последнего поиска статьи во внешних источниках: 25 января 2019 г.
Аннотация:Characteristics of radiation and propagation of seismic waves required in various seismological applications, especially in seismic hazard assessment, are estimated in the northern Finland based on records of local earthquakes (~80 records from 4 stations, Mw ~1.5–4.1, h ~3–25 km). The northern Finland possesses relatively low seismic activity, however rather strong earthquakes occurred there in the past. We applied coda-normalization method to estimate the quality factor Q(f) ~Q0f n, and then verified and corrected the Q(f) estimates at low frequencies by stochastic simulations. We obtained Q0 ~80–100, n~1.1–1.2 for hypocentral distances of ~20–150 km, and Q0 ~180–350, n ~0.7–0.9 for hypocentral distances of ~150–320 km. Other parameters were estimated by the empirical methods and stochastic simulation of local earthquakes (ML >2.0). We estimated the stress drop (~200 bars), geometrical spreading (as a two-segment function: 1/R for R ~0–80 km and 1/80 for R ~80–300 km), the duration of seismic motion depending on the hypocentral distance, kappa value (~ 0.001-0.03 s), and some other parameters. The obtained high estimates of the stress drop, along with rather high Q-values, may result in noticeably increased (compared to those that could be expected on average) PGA estimates in seismic hazard assessment in the northern Finland.