Physics
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufm.t53d1613m&link_type=abstract
American Geophysical Union, Fall Meeting 2009, abstract #T53D-1613
Physics
[8120] Tectonophysics / Dynamics Of Lithosphere And Mantle: General, [8123] Tectonophysics / Dynamics: Seismotectonics, [8125] Tectonophysics / Evolution Of The Earth, [8147] Tectonophysics / Planetary Interiors
Scientific paper
We introduce a new approach to estimating the seismic potential of continental intraplate regions based on the deep seismic properties of the lithosphere. Our hypothesis is that greater integrative lithospheric strength correlates with lower rates of continental crustal seismicity and with lower maximum earthquake magnitudes, also known as Mmax. Integrative lithospheric strength is controlled by lithospheric composition and the geotherm, which is correlated with S-wave velocity. High lithospheric S-wave velocities, typical of cratonic lithosphere, correspond to high integrative lithospheric strength. We have created new global maps of S-wave velocity anomalies (δVs) at a depth of 175 km. We find that δVs ranges from +5% to -5%. We compare the values of these mantle S-wave anomalies with the moment magnitudes of intraplate earthquakes in the overlying crust. We find that only 10% of 460 events with moment magnitudes between 5 to 6; 15% of 110 events with moment magnitudes between 6 to 7; and none of the 14 intraplate events with moment magnitudes greater than 7 occur above mantle lithosphere with δVs greater than 3.5% (cratonic lithopshere). We conclude therefore that integrated lithospheric strength, as indicated by S-wave velocity anomalies, correlates with crustal seismicity. Mmax appears to be M7 for cratonic continental regions underlain by δVs greater than 3.5% at 175 km depth. This includes a large portion of the Precambrian continental interior of North America of Archean and Neoproterozoic age.
Mooney Walter D.
Ritsema J. E.
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