HR: 16:15h
AN: G24A-04 INVITED     [Abstracts]
TI: Use of Geological Data to Investigate the Rheology, Geometry, and Temporal Evolution of Faulting in the New Madrid Seismic Zone
AU: * Kenner, S J
EM: skenner@uky.edu
AF: Univ. of Kentucky, Department of Geological Sciences, 101 Slone Build., Lexington, KY 40506 United States
AU: Joshi, A
EM: ajosh2@uky.edu
AF: Univ. of Kentucky, Department of Mechanical Engineering, 101 Slone Building, Lexington, KY 40506 United States
AB: In this study we use paleoseismic observations to investigate possible earthquake generation models in the New Madrid Seismic Zone (NMSZ). Observations from the NMSZ include mean recurrence times of ~500 years, finite fault length, and ~100 m of total offset. Faulting is inferred to have begun in the Holocene. To be successful, understanding of the proposed models at a number of time-scales and rheological conditions is extremely important. If the NMSZ is modeled as a relaxing weak zone at depth, the time-scale of that relaxation process must match observations. The duration of the modeled relaxation process is highly dependent on the rheology of the weak zone. We have investigated a number of rheologies including Maxwell viscoelastic, standard linear solid, and power-law rheologies. Acceptable rheologies must satisfy the duration of the total relaxation process, as stated above. Postseimic effects, which act at a shorter time-scale are also observed in the model. During the earthquake, stresses are transferred back the underlying weak zone. This effectively recycles strain and prolongs relaxation of the proposed weak zone. Though relatively short-lived, postseismic effects clearly play an important part in the overall behavior of the system. There are also geometric effects that influence the relaxation time of the proposed weak zone. If the weak zone is wide, then stress is transferred upward to areas far from the actual faults. This prolongs the relaxation process as these stresses must work their way to the actual fault as relaxation continues. For narrow weak zones this effect is less important. Finally, there are time-scales that are much longer than the time-scales inferred from observations in the NMSZ. These are the processes that act to initially localize stress within the NMSZ. We investigate whether or not these stresses are localized or generated in the far-field. Further, we investigate the possible geometrical evolution of faulting using plastic models of strain accumulation through time. These models incorporate the source(s) of stress which drive seismicity in the NMSZ.
DE: 1208 Crustal movements--intraplate (8110)
DE: 3210 Modeling
DE: 8110 Continental tectonics--general (0905)
DE: 8159 Rheology--crust and lithosphere
DE: 8164 Stresses--crust and lithosphere
SC: Geodesy [G]
MN: 2005 Joint Assembly