Improving Velocity Constraints in Sedimentary Basins by Jointly Modeling Receiver Functions and Autocorrelograms

Benjamin Sadler, Patricia Persaud, & Jay Pulliam

Published September 8, 2024, SCEC Contribution #13723, 2024 SCEC Annual Meeting Poster #023

Sedimentary basins can amplify the energy of earthquakes. The scale and frequency content of the amplification are related to the basin’s shape, depth, and rock properties, as well as the source-time function and location of the earthquake. Because of this, accurate models of sedimentary basins are important for seismic hazard analysis. Here, we present a method that leverages the long recording periods of broadband networks to extract information on sedimentary basin structure. We apply a waveform modeling approach that matches synthetic receiver functions (RFs) and vertical autocorrelograms (ACs) based on a range of possible velocity models to the observed data. The delay time for each converted (Ps) arrival in an RF depends on VP / VS and depth to its conversion point, for a given VP. This relationship can be used to constrain crustal structure. However, RF methodologies often give poor results in sedimentary basins, because basin VP values vary over a broad range and distinguishing between converted and reflected phases generated at the sediment-basement interface and the Moho can be challenging. ACs recover reverberated P waves generated at the same impedance contrasts that cause wave conversions recorded by RFs. The reverberation delay time depends only on VP and depth to the discontinuity. Therefore, considering ACs and RFs together improves constraints on crustal structure, which can be estimated in terms of three independent parameters, VP, VP / VS, and depth to discontinuity, for each in a stack of layers. We use non-linear global optimization methods to navigate the parameter space efficiently and comprehensively.

We applied this method to stations in the Permian Basin in west Texas and eastern New Mexico, the Gulf Coast Basin in the south-central US, and the Bengal Basin in Bangladesh. In these locations, jointly modeling RFs and ACs offered improved constraints relative to RFs alone, with VP being treated as a free parameter for at least the sedimentary units in all three locations. In the Permian Basin, a two-layer velocity structure is considered, while the Gulf Coast Basin and Bengal Basin are both much deeper (>18 km) and have several intrasedimentary contacts. This method has been used to consider up to four layers, with the number of resolvable layers depending on clear phase separation in both the RFs and ACs, as well as solution stability.

Key Words
Sedimentary Basins, Receiver Functions, Autocorrelograms

Citation
Sadler, B., Persaud, P., & Pulliam, J. (2024, 09). Improving Velocity Constraints in Sedimentary Basins by Jointly Modeling Receiver Functions and Autocorrelograms. Poster Presentation at 2024 SCEC Annual Meeting.

Related Projects & Working Groups
Seismology