HR: 1340h
AN: S33B-1101    [Abstracts]
TI: 4Deep Seismix
AU: * Stephenson, M A
EM: mas285@cornell.edu
AF: Cornell University, Department of Earth and Atmospheric Sciences Snee Hall, Ithaca, NY 14853 United States
AU: Brown, L D
EM: brown@geology.cornell.edu
AF: Cornell University, Department of Earth and Atmospheric Sciences Snee Hall, Ithaca, NY 14853 United States
AB: 4D, or time-lapse, seismic reflection imaging is rapidly becoming a mainstream tool in monitoring oil field production. The same technology offers considerable potential in addressing issues central to active tectonics in deeper crust. In this study, we employ acoustic finite difference wave equation modeling using MATLAB (CREWES) to evaluate the issues that constrain the feasibility of time-lapse imaging of seismic and volcanic systems. Such systems are the most likely to have temporal variations which occur on time scales where such surveys may have operational practicality. Among the processes modeled are changes in inflation (or deflation) of magma sills at midcrustal depths, fluid pressure in the deep seismogenic zone, and offset of potential marker horizons by aseismic creep in slow earthquakes. While the latter would seem to be beyond practical consideration, at least at the present time, differential seismic sections produced for a variety of magma inflation models indicate that monitoring of magma movements at depth is a realistic goal. Possible seismogenic variations in deep faults zones are perhaps more problematic, though our model suggests scenarios wherein useful results may be obtained. In all of these cases, resolution is perhaps less of an issue than S/N. Noise sources include both ambient noise, and systematic property variations in overlying media. The latter may be addressed by standard signal enhancement procedures, both in acquisition and processing. The former may be addressed by "registration' of data against natural deep markers. While one can envision a number of significant practical hurdles to time lapse imaging of deep processes, this study indicates that it is not an unreasonable goal. Moreover, the deep crust may prove to be considerably less `static' that we normally assume.
DE: 7223 Seismic hazard assessment and prediction
DE: 7280 Volcano seismology (8419)
DE: 7294 Instruments and techniques
DE: 7209 Earthquake dynamics and mechanics
SC: Seismology [S]
MN: 2004 AGU Fall Meeting