Large-N Array Seismology at the Source Physics Experiment

Session: Explosion Seismology Advances [Poster]
Type: Poster
Date: 4/29/2020
Time: 08:00 AM
Room: Ballroom
Description: 

We use seismic interferometry to obtain highly detailed images at the site of the Source Physics Experiment (SPE). SPE was a series of experiments in varying geologies with the objective of obtaining a physics-based understanding of how seismic waves are created at and scattered near seismic sources. Phase I of the experiment involved chemical explosions in granite, with energy traveling across volcanics, carbonates and alluvium. Phase II of the experiment was done in a dry alluvium geology (DAG). The seismic records of these experiments change dramatically as energy moves through different geologies, resulting in highly complex signals. To separate source-specific effects from those due to geological structure, we calculate precise 3D models at scales ranging from tens of meters to tens of kilometers.

In April 2016, a large, dense array of 996 geophones were deployed just south of the Phase I source point recording for several weeks and recording one of the experimental sources. During Phase II, an array of 500 instruments was deployed around the DAG site and left in place for several months, recording three of the sources along with their aftershocks, as well as the ambient background wavefield.

We apply several interferometric techniques to measure the subsurface properties: Source interferometry (SI) uses the explosions as rich sources of high frequency, high signal energy. Coda interferometry (CI) isolates the energy from the scattered wavefield. Ambient noise correlation (ANC) uses the energy of background wavefield. In each case, the data recorded at one seismometer are correlated with the data recorded at another to obtain an estimate of the Green's function (GF) between the two. These GFs are then inverted to obtain the final seismic image.

This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344

Presenting Author: Eric Matzel

Authors