Data Services Newsletter

Volume 17 : No 1 : Spring 2015

Global Empirical Green's Tensors data product

In collaboration with Yang Shen and colleagues at University of Rhode Island, the DMC has released a set of Global Empirical Green’s Tensors. Empirical Green’s functions (EGFs) can be extracted from ambient seismic records. They have precisely known “virtual source” locations and contain useful surface waves at periods shorter than those from teleseismic earthquakes. For these reasons, they have been widely used to image the crust and uppermost mantle structure. The Global Empirical Green’s Tensors data product is a repository of Empirical Green’s Functions across global and continental scales and is now available. The repository currently holds two data sets:

  • 64,000 global scale vertical-vertical component EGFs (20-600s) using ~400 global stations
  • 64,000 continental scale vertical-vertical component EGFs (8-300s) using ~500 North American stations

The database is intended to be non-static: As new seismic data are available from the existing stations and new stations are deployed, the database may be updated. It is also intended to be an open database for anyone to contribute as long as data processing follows a consistent, best practice.

Figure 1
Figure 1: Examples of vertical-vertical EGFs at the global scale. The seismograms have been filtered between 200-400 s period. Red dots mark the travel time of a wave with a group velocity of 4 km/s. The map shows the paths between the virtual source (station CN.DRLN, red triangle) and receivers (GSN stations, black triangles).

by Alex Hutko (IRIS Data Management Center)