Understanding Seismic Detection and Resolution of High-Frequency Sequences and Systems Tracts

Hongliu Zeng
BEG, Jackson School of Geosciences, The University of Texas at Austin, Austin, TX

Seismic mapping of stratigraphy can do better than the resolution limit (a quarter wavelength). For example, seismic geomorphology may resolve a feature normally detectable only in the vertical dimension. The vertical detection limit for horizontal resolution can be defined as an extension of Rayleigh’s criterion for resolution limit, in which an event from a bed, not a surface, is visually separated from other events.

We can quantify detection limit by analyzing the configuration of seismic events that correspond to an acoustically converted stratigaphic profile through various frequency bands, or an Event versus Frequency (EVF). An EVF plot reveals seismic interference patterns, thickness tuning range, and what would expected to see in seismic data of different frequency bands. Generally speaking, in the high-frequency range, the top and base of a unit are resolved, and amplitudes of an event are proportional to impedance contrast. In data of moderate frequency, the unit is detected but not resolved, and thickness tuning may dominate, with amplitudes varying with thickness. In the low-frequency range, the unit fails to be detected, its seismic responses merging with other events, and its identity becoming lost.

Each stratigraphic profile is different, and the detection limit may vary from one high-frequency sequence to another. By analyzing EVF’s from field data at well sites, we can determine the detection range of field seismic data and how it compares with what is required for mapping high-frequency sequences and systems tracts. Proper data conditioning based on this analysis might significantly improve the study of high-frequency sequence stratigraphy.

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas