HR: 13:55h
AN: S53C-02 INVITED    [Abstracts]
TI: Improving on Inversions for Kinematic Parameters of the Earthquake Source
AU: * Archuleta, R J
EM: ralph@crustal.ucsb.edu
AF: Institute for Crustal Studies, 1140 Girvetz Hall University of California, Santa Barbara, Santa Barbara, CA 93106, United States
AU: Liu, P
EM: pcliu@crustal.ucsb.edu
AF: Institute for Crustal Studies, 1140 Girvetz Hall University of California, Santa Barbara, Santa Barbara, CA 93106, United States
AU: Custódio, S
EM: susana@crustal.ucsb.edu
AF: Institute for Crustal Studies, 1140 Girvetz Hall University of California, Santa Barbara, Santa Barbara, CA 93106, United States
AU: Page, M
EM: pagem@physics.ucsb.edu
AF: Department of Physics, Broida Hall University of California, Santa Barbara, Santa Barbara, CA 93106, United States
AB: Since the first inversion of strong motion data for the slip during the 1966 Parkfield earthquake, there have been numerous attempts to infer the kinematic parameters of earthquakes. It is grossly inadequate to think of the distribution of final slip as being a kinematic model. Besides the geometry of the fault and the location of the hypocenter, a kinematic model includes the functional form of the slip rate time function, the temporal parameters of the slip rate function (rise time), the rupture time (equivalently the rupture velocity) and the final slip. All of the parameters can be spatially varying on the fault. The fault and the recording stations are located in a velocity/attenuation structure. Besides the basic uncertainty in the Green's functions regarding the correct velocity/attenuation structure, the fundamental problem is nonlinear with respect to the temporal parameters. The other critical pieces of the puzzle are the distribution of stations and the type of data being inverted. Thus it is no surprise that while there are numerous kinematic inversions for a faulting model, there have been far fewer attempts to address the basic question of what can inversions resolve about the faulting. This has related questions, such as what are the errors in the presented models, which depend on what the resolution is, and also what the data and Green's function errors are and how these errors propagate to the solution. In this presentation we review some of the basic findings about resolution as well as present some results on resolution with respect to the combined inversion of seismic and GPS data. Among the results that need to be emphasized is the most obvious that the distribution of stations inherently limits the resolution. A second major conclusion is that the rupture velocity is variable and has a profound effect on the solution. The rupture velocity and the spatial distribution of slip are fundamentally linked; any use or description of a kinematic model must emphasize each. Of course, because the rupture velocity is nonlinearly related to the data, it is doubly difficult to estimate error in this parameter without considering the correctness of the velocity structure itself. We find that GPS data (static field) can constrain the final slip, but because of the difference in the Green's functions for the static field and dynamic radiation, the inversion should be a two-step process. In the first step the static field data can be inverted using an irregular grid, the spacing determined by the model resolution. The static slip can then constrain the nonlinear inversion of the seismic data.
DE: 7200 SEISMOLOGY
DE: 7209 Earthquake dynamics (1242)
DE: 7215 Earthquake source observations (1240)
DE: 7260 Theory
SC: Seismology [S]
MN: 2007 Fall Meeting