HR: 1330h
AN: S22A-0417    [PDF]
TI: Seismicity in the Central U.S. and Its Implication for Lithospheric Strength in the New Madrid Seismic Zone
AU: * Miao, Q
EM: qingmiao@memphis.edu
AF: Earthquake Research and Information, The University of Memphis 3892 Central Avenue, Memphis, TN 38152 United States
AU: Langston, C A
EM: clangstn@memphis.edu
AF: Earthquake Research and Information, The University of Memphis 3892 Central Avenue, Memphis, TN 38152 United States
AB: The depth histogram for seismicity is generally used in comparisons of seismicity and lithospheric strength models. Here, we examine the depth distribution of cumulative strain energy release (estimated from event magnitude) for seismicity in the central U.S. as a better physical indicator of the lithosphere­_s ability to store and release elastic strain energy. Seismic parameters in Central U.S. were collected and analyzed and include 5127 events occurred from 1974 to present. The analysis was performed with a focus to understand the difference of seismicity between the NMSZ and other Central U.S. areas so as to find constraints for construction of lithospheric strength models in the study area. The result shows that 82% of the 5127 events occurred in the NMSZ, but only accounted for 30% of total energy release, with dominant focal depth at 5 km and dominant energy release depth at 15 km. 18% of the 5127 events occurred in the other areas outside the NMSZ, accounting for 70% of total energy release, with dominant focal depth at 5 km and dominant energy release depth at 10 km. Even though there may be some artifacts for the event depth distribution introduced by the early earthquake location program, it is reasonable to conclude that the dominant energy release depth for the NMSZ is located at a lower depth than that for the other Central U.S. areas. It is noticed that most of the events with magnitude equal to or greater than 3.0 and depth equal to or greater than 15 km occurred in NMSZ. The deepest event with magnitude 4.0 occurred on 30 Apr 2003 with a focal depth at 23.8 km in NMSZ. Based on these analytic results, new lithospheric strength models are constructed for the NMSZ and Central U.S. respectively.
DE: 7218 Lithosphere and upper mantle
SC: Seismology [S]
MN: 2003 Fall Meeting