HR: 0800h
AN: S51B-1001    [Abstracts]
TI: Oceanic Earthquake Source Parameter Variations
AU: * Schramm, K A
EM: schramm@earth.northwestern.edu
AF: Northwestern University, Dept. of Geological Sciences 1850 Campus Drive, Chicago, IL 60208-0860 United States
AU: Stein, S
EM: seth@earth.northwestern.edu
AF: Northwestern University, Dept. of Geological Sciences 1850 Campus Drive, Chicago, IL 60208-0860 United States
AB: We are revisiting several generalizations about oceanic seismicity developed before the wide availability of global digital data. Based on several metrics, Stein and Pelayo (1991) proposed that relative to ridge and intraplate earthquakes, transform events were "slow", or deficient in short period energy. Our initial findings based on body wave modeling suggest that one of these metrics, differences in body vs surface magnitude, may instead reflect a focal mechanism bias. Hence we will investigate whether the "slowness" persists when examined via moment and time function variations. We also reexamine Wiens and Stein's (1983) results about the variation in intraplate oceanic earthquakes depths and mechanisms versus lithospheric age. Preliminary results confirm that the maximum depth of seismicity increases with age consistent with its being temperature-limited in the cooling lithosphere. We hope to decide whether the temperature limit corresponds to the brittle-ductile transition or also permits faulting in the ductile regime. The larger dataset also shows that normal faulting is restricted to the upper 30 km and concentrated in younger lithosphere.
DE: 7203 Body waves
DE: 7215 Earthquake source observations (1240)
DE: 7220 Oceanic crust
DE: 7250 Transform faults
SC: Seismology [S]
MN: Fall Meeting 2005