GPS Constraints on Seismic Hazard in Continental Intraplate Regions: Eastern Canada

Example

S. Mazzotti, J. Henton, T. James, J. Adams

Geological Survey of Canada & Geodetic Survey Division, Natural Resources Canada

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 110, B11301, doi:10.1029/2004JB003590, 2005

Figure A10–1

Regional strain =E-W shortening(agrees with earthquake mechanisms)

Strain rates 1-4 x 10-9 /yr

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Convergence across St Lawrence 0-1 mm/yr

(2) Crustal Strain from GPS Figure A10–2

(3) GPS & Seismic Hazard

Assumptions for integration of GPS strain rates in hazard:

1) Strain model:GPS Seismic strain release

2) Earthquake statistics:GR recurrence / characteristic

3) Seismic thickness:maximum depth / effective

thickness

Magnitude & Recurrence of large

earthquakes

Figure A10–3

GPS convergence rate:~0.7 +/- 0.4 mm/yr

Gutenberg-Richter distribution up to Mx

Charlevoix: Mx = 7.8 (std. 7.2-8.5)

Lower St Lawrence: Mx = 7.3 (std. 5.5-8.3)

(3) GPS & Seismic Hazard Figure A10–4

GPS convergence rate:~0.8 +/- 0.5 mm/yr

Characteristic earthquakes

Charlevoix: M7 = 1/200 yr (std. 100-400 yr)

Lower St Lawrence: M7 = 1/1000 yr (std. 400-20,000 yr)

(3) GPS & Seismic Hazard Figure A10–5

Conclusions

1) In Charlevoix and Lower St Lawrence, 2) GPS strain rates agree well with seismic strain rates

CHV: 0.7 (+/- 0.4) mm/yr <=> 1.0 (+/- 0.5) mm/yr

BSL: 0.2 (+/- 0.6) mm/yr <=> 0.2 (+/- 0.3) mm/yr

2) GPS data constrain the recurrence and magnitude of large earthquakes

CHV: Mx ~7.8 (+/- 0.6) <=> T(M7) ~ 200 – 1000 yr

BSL: Mx ~7.3 (+/- 1 ?) <=> T(M7) >> 400 yr

Figure A10–6