Analysis and removal of sediment signal in receiver functions

Vera Schulte-Pelkum, Justin Ball, Thorsten W. Becker, Robert Porritt, & Whitney M. Behr

Submitted August 15, 2019, SCEC Contribution #9720, 2019 SCEC Annual Meeting Poster #091

Receiver functions in sedimentary basins can show strong shallow reverberations that can overprint signal from the deeper crust and Moho. At the same time, these reverberations carry information on near-surface velocity structure that may be useful for site and surface characterization.

We compare receiver functions from the UTIG Mojave Experiment, a dense line of seismic stations in the California Mojave desert with stations specifically sited to avoid near-surface signal in order to target deep fault structure and shear fabric, and from other stations in the Mojave with those from nearby stations with strong reverberations. Ps receiver functions from stations only a few kilometers apart show fundamentally different character, and the Moho and other deep crustal structure may be misidentified. We demonstrate the same effect using a cluster of closely situated Transportable Array stations near the PASSCAL facility in Socorro, NM.

One approach to removing near-surface reverberations requires characterizing the near-surface structure. Filters targeting S reverberations similar to water multiple removal can be successful in some locations, but fail when mixed mode reverberations have significant amplitude. We show examples of instantaneous phase-based methods that may allow separation of multiples from primary deeper conversions without describing the shallow structure accurately.

However, for seismic hazard assessment, an accurate characterization of the near-surface structure in terms of Vp, Vs, and depth is desirable. Waveform modeling and inversion of receiver functions for these parameters is poorly constrained and nonunique. We explore approaches that simplify the problem and attempt more robust characterization of the near-surface structure by using zero-delay component amplitudes and amplitudes and timing of the Ps conversion from the contact between a shallow low-velocity layer and bedrock and multiples of that arrival.

Considered on a continental U.S. scale, basin effects strongly modify receiver function as well as surface wave signals in a large portion of the area. Solving the reverberation problem thus contributes to current development efforts such as the USGS National Crustal Database and aids both hazard characterization as well as deep lithospheric imaging.

Key Words
Crustal structure, basins, receiver functions, Mojave Experiment

Schulte-Pelkum, V., Ball, J., Becker, T. W., Porritt, R., & Behr, W. M. (2019, 08). Analysis and removal of sediment signal in receiver functions. Poster Presentation at 2019 SCEC Annual Meeting.

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