Combining EarthScope Long Period Magnetotelluri and Geomagnetic Observatory Data: Hypothetical Events at Continental Scale

Abstract:

The EarthScope USArray project has been collecting long period (1 hz) MT data on a quasi-uniform 70 km grid since 2006, using a “rolling” array of approximately 20 long period MT sensors. Up to this point over 700 sites have been occupied (each for ~3-4 weeks) covering almost half the continental US. Seven “backbone” EarthScope MT sites were deployed (but did not fully operate) continuously from 2008-2011. At the same time, continuous high-quality 1 hz vector magnetic field data are available from eight geomagnetic observatories spread over the continental US/southern Canada since 2007. These data can be supplemented with long term (but again not always continuous) magnetometer deployments used for space physics research—e.g., up to 25 sites are available from the Themis project. I will discuss application of multivariate array processing methods to these datasets, with the goal of merge the large scale synoptic observatory, with the other sites, including the spatially dense, but short duration, partially overlapping EarthScope arrays. The merged array can be used to create true hypothetical events -- maps of the electromagnetic that would be observed for highly idealized sources—both plane wave and gradient. These maps can provide a unique perspective on the internal induced fields within the Earth, and suggest novel strategies for extracting reliable information about crust and mantle conductivity. The synthesis may also provide new insights into external source characteristics, and their interaction with the conducting Earth. Application of these results to development and validation of methods for modeling and predicting geomagnetically induced currents (GIC) will also be discussed.