Regional spectral analysis of three moderate earthquakes in Northeastern North America
Bulletin of the Seismological Society of America
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Abstract
We analyze Fourier spectra obtained from the horizontal components of broadband and accelerogram data from the 1997 Cap-Rouge, the 2002 Ausable Forks, and the 2005 Rivière-du-Loup earthquakes, recorded by Canadian and American stations sited on rock at hypocentral distances from 23 to 602 km. We check the recorded spectra closely for anomalies that might result from site resonance or source effects. We use Beresnev and Atkinson’s (1997) near-surface velocity structures and Boore and Joyner’s (1997) quarter-wave method to estimate site response at hard- and soft-rock sites. We revise the Street et al. (1975) model for geometrical spreading, adopting a crossover distance of ro=50 km instead of 100 km. We obtain an average attenuation of Q=410±25f0.50±0.03 for S+Lg+surface waves with ray paths in the Appalachian and southeastern Grenville Provinces. We correct the recorded spectra for attenuation and site response to estimate source spectral shape and radiated energy for these three earthquakes and the 1988 M 5.8 Saguenay earthquake. The Brune stress drops range from 130 to 419 bars, and the apparent stresses range from 39 to 63 bars. The corrected source spectral shapes of these earthquakes are somewhat variable for frequencies from 0.2 to 2 Hz, falling slightly below the fitted Brune spectra.
Suggested Citation
Boatwright, J., Seekins, L.C., 2011, Regional spectral analysis of three moderate earthquakes in Northeastern North America: Bulletin of the Seismological Society of America, v. 101, no. 4, p. 1769-1782, https://doi.org/10.1785/0120100225.
ISSN: 1943-3573 (online)
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Regional spectral analysis of three moderate earthquakes in Northeastern North America |
| Series title | Bulletin of the Seismological Society of America |
| DOI | 10.1785/0120100225 |
| Volume | 101 |
| Issue | 4 |
| Publication Date | August 01, 2011 |
| Year Published | 2011 |
| Language | English |
| Publisher | Seismological Society of America |
| Publisher location | El Cerrito, CA |
| Contributing office(s) | Earthquake Science Center |
| Description | 14 p. |
| Larger Work Type | Article |
| Larger Work Subtype | Journal Article |
| Larger Work Title | Bulletin of the Seismological Society of America |
| First page | 1769 |
| Last page | 1782 |
| Country | United States;Canada |