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What Constitutes Knowledge of “Site Response”? the Embayment Seismic Excitation Experiment 2022 (ESEE2022)

Description: 

Thick, weakly consolidated sediments of the Gulf and Atlantic coastal plains blur the distinction between “path” and “site” effects in the commonly assumed phenomenological model of “source-path-site” used for representing wave propagation from earthquakes. In the absence of empirical strong motion data, this requires that sediment physical properties need to be determined for realistic wave propagation simulations. ESEE2022 was conceived to determine seismic velocity and attenuation structure of a ~900m thick section of Mississippi Embayment sediments near Memphis, TN. A 3km profile of 60 nodal seismometers recorded body and surface waves from 91 kg explosions detonated in 15m depth boreholes at both ends of the profile on the nights of 25 and 26 July 2022. Strong motion velocity data were collected within 150m of each explosion and small-scale P and SH refraction profiles taken at each shot point the week before. Because the nodal seismometers were deployed over a two-week period, there is also a large data set of ambient ground motions along the profile. The working hypothesis for analyzing this large data set is that a single, vertically inhomogeneous velocity and anelastic attenuation earth model can be constructed to fit surface wave dispersion measurements, body wave travel time and amplitude measurements, Greens functions from ambient noise interferometry, and H/V spectral peaks, culminating in full waveform inversion of the explosion data. Near-source strong motion accelerations ranging from 0.5g to 4g may have induced non-linear changes to near-surface materials which might be observed by comparing near-surface velocity structures determined with small scale refraction and the near-station explosion data. We suspect that this dataset will offer information on the limitations and veracity of both passive and active source methods to infer information on thick unconsolidated sediments.

Session: Site-specific Modeling of Seismic Ground Response: Are We Quantitative Enough to Predict? [Poster]

Type: Poster

Date: 4/19/2023

Presentation Time: 08:00 AM (local time)

Presenting Author: Charles A. Langston

Student Presenter: No

Invited Presentation: 

Authors