HR: 10:35h
AN: S52B-02    [Abstracts]
TI: An Improved Global Energy to Moment Ratio Catalog: More Events, Stations, and Rupture Durations
AU: * Convers, J A
EM: jconvers@gatech.edu
AF: Georgia Institute of Technology, School of Earth and Atmospheric Sciences, 311 Ferst Drive, Atlanta, GA 30332, United States
AU: Newman, A V
EM: anewman@gatech.edu
AF: Georgia Institute of Technology, School of Earth and Atmospheric Sciences, 311 Ferst Drive, Atlanta, GA 30332, United States
AU: Nobles, A L
EM: anobles3@gatech.edu
AF: Georgia Institute of Technology, School of Earth and Atmospheric Sciences, 311 Ferst Drive, Atlanta, GA 30332, United States
AB: To enhance a global dataset of radiated earthquake energies, E, we use the methodology of Newman & Okal [1998] to develop an improved catalog of events that include activity for the past 10 years, incorporating all earthquakes with M_W > 6.6. This new catalog contains 5 × the number of earthquakes, and 20 × the waveforms of the original study. For each event, E is compared to the seismic moment, M₀, to determine average values and variations in earthquake strong shaking. In addition to a denser event database, we also extend the original dataset upward by a unit magnitude due to the inclusion of recent, very large earthquakes. Because we utilize the complete rupture durations (especially important for large and "tsunami earthquakes"), energy estimates more accurately represent true shaking for long duration events. We find that globally the average ratio, Θ = log₁₀E/M₀ = -4.66, is somewhat higher than the value (-4.98) found by Newman & Okal [1998]. Likewise, because of a vast improvement in globally available seismic data for more recent events, we can now better explore the effects of source directivity, together with random and path- dependent errors in global energy calculations. Additionally, we explore the possibility of regional effects on the E/M₀ ratio, determining energies for all earthquakes M_W>5.5 along the Middle America Subduction zone, the site of an energy-deficient "tsunami earthquake" in 1992. We find that regional dip-slip events are characterized by a lower average Θ of -5.13, with no significant along-strike observed changes. The lower regional value suggests that these events have generally slower ruptures, lower stress drops, or are in a higher attenuation environment than the global average.
DE: 7200 SEISMOLOGY
DE: 7203 Body waves
DE: 7209 Earthquake dynamics (1242)
DE: 7215 Earthquake source observations (1240)
SC: Seismology [S]
MN: 2007 Fall Meeting